The Suez Canal is a unique sea-level waterway between northern Africa and southern Asia that connects the Mediterranean Sea to the Red Sea via the Isthmus of Suez. The canal’s artificial navigation route substantiall...The Suez Canal is a unique sea-level waterway between northern Africa and southern Asia that connects the Mediterranean Sea to the Red Sea via the Isthmus of Suez. The canal’s artificial navigation route substantially reduced the sailing distance between countries in Europe and East Asia and offered a more direct route between the North Atlantic Ocean and the Indian Ocean through the Mediterranean Sea and the Red Sea. The primary objective of this study is to document the historical, economical, and environmental impacts of connecting the Mediterranean Sea and the Red Sea via a canal. After the completion of the Suez Canal in 1869 the canal became an economically lifeline for Egypt. However, the economic gains were partially offset by negative environmental impacts. The impact of port activities on the environment depends on their cargo volume and location, seaports can have an impact on the air quality and therefore on the health of the communities along the Suez Canal. The salinity barrier to migration was removed and animals and plants from the Red Sea began colonizing the eastern Mediterranean. Since the 1880s, species from the Indo-Pacific Ocean have been introduced, via the canal, into the Mediterranean ecosystem. They are endangering some local and endemic species and impacting the ecology. The results showed significant changes in the shoreline and land cover due to climate change and anthropogenic activities that necessitate the implementation of adequate protective measures. The findings of this study may assist policymakers in formulating adaptation plans to protect this crucial area, the communities along the Suez Canal and the Red Sea and Mediterranean ports, from climate change and human activities.展开更多
Environmental sociology and the sociology of natural resources are two key subdisciplines of the sociological study on the interactions between nature and human society.Previous discussion on the relationships of thes...Environmental sociology and the sociology of natural resources are two key subdisciplines of the sociological study on the interactions between nature and human society.Previous discussion on the relationships of these two fields has largely focused on their distinctions and synthesis in western(particularly American) academia.Environmental sociology emerged as an important sociological subdiscipline in China in the early 1990s and is under vigorous disciplinary construction at present.By contrast,the sociology of natural resources is still a novel term for most Chinese researchers.This article provides a systematic review of recent literature on the relationships between environmental and natural resource sociologies,which should provide important implications for the further development of environmental sociology in China.展开更多
The Dnieper River headwaters are in Russia’s Valdai Hills and the river flows south to the Black Sea. The Dnieper River provides a waterway in which to transport goods to and from various European nations. In additio...The Dnieper River headwaters are in Russia’s Valdai Hills and the river flows south to the Black Sea. The Dnieper River provides a waterway in which to transport goods to and from various European nations. In addition, the dams on the river provide hydro power. There are approximately 2260 km of Dnieper waterways in Russia, in Belarus, and within Ukraine. The Dnieper River has numerous urban centers including Smolensk in Russia, Mogilev in Belarus and Kiev and Zaporizhzhya in Ukraine. The worst nuclear accident in history unfolded, in the Dnieper River watershed, in northern Ukraine as a reactor at the Chernobyl nuclear power plant exploded and burned. After an accident, such as Chernobyl, radionuclide contaminated bodies of water via direct deposition from the air, discharge as effluent or indirectly from catchment basin washout. When radionuclides contaminate large bodies of water, they are quickly dispersing and accumulate in water bottom sediments, benthos, aquatic plants, and bottom feeding fish. The main pathways to humans are through contamination of drinking-water, from use of water for irrigation of food crops, and consumption of contaminated fish. Kakhovka Dam on the Dnieper River was destroyed during the Russian-Ukraine conflict and the dam needs to rebuild as soon as possible. Perhaps lessons learned by the US Army Corps of Engineers (USACE), after using TNT to blow up the Birds Point front line levee on the Mississippi River in May of 2011, can be applied to the man-induced 2023 Kakhovka Dam breach. The Birds Point man-induced levee breaches and subsequent flooding of farmland resulted in the loss of the 2011 crops and damaged the future soil productivity. The strong current and sweep of the water through the three man-induced levee breaches on the New Madrid floodway levee created deep gullies, displaced tons of soil, and damaged irrigation equipment, farms, and homes. The New Madrid floodway agricultural lands were restored, and the environmental damages were mitigated. The Kakhovka Dam destruction caused widespread flooding which affected settlements and farmland across the Dnieper watershed. The presence and breach-induced redistribution of Chernobyl-derived nuclides is an additional condition not present at the New Madrid man-induced levee breach. Four canal networks have become disconnected from the feeder reservoir. The canals were the source of drinking water for 700,000 people living in southern Ukraine. The Kakhovka canals also provided irrigation for vast areas of farmland. The water loss from the canals adversely affected food production in the region. The primary objectives of this paper are to assess lessons learned by the USACE and apply them in Ukraine to help restore and manage the Dnieper lifeline and watershed.展开更多
The Lancang-Mekong River in China, Laos, Thailand, Myanmar, Cambodia, and Vietnam is the soul and heart of mainland Southeast Asia. Over 60 million people depend on the river and its tributaries for food, transportati...The Lancang-Mekong River in China, Laos, Thailand, Myanmar, Cambodia, and Vietnam is the soul and heart of mainland Southeast Asia. Over 60 million people depend on the river and its tributaries for food, transportation, water, and other necessities of life. The river supports one of the world’s most diverse fisheries, second only to Brazil’s Amazon River. Lancang-Mekong and tributaries are already heavily dammed primarily in China, Laos, Thailand, and Cambodia, with many more dams planned or under construction. Dams can worsen the impact of periodic droughts in the Lancang-Mekong basin and block the river’s “pulse effect” that spreads water and nutrients needed for fishing and farming onto the floodplains and delta. The headwaters of the Lancang are in China and its waters are considered a national resource. China regards the Lancang, Yangtze and Yellow rivers as a free resource rather than a shared resource. The primary difference between these rivers is the Lancang flows from China into and through other countries and not directly into a sea or ocean. China and Myanmar have not joined the Mekong River Commission (MRC) as full members but have been Dialogue Partners since 1996. Over the past thirty years, China’s Lancang policies and actions have reflected its national resource interests. China has actively engaged with individual transboundary countries at various levels including environmental, conservation, and economic agreements. The primary objective of this study is to assess the environmental and human impacts of all Lancang-Mekong mainstem and tributary dams and the plans by many countries for more hydropower utilizing the potential of the river as the continent’s energy lifeline. Future dams need to include fish ladders and navigation locks to reduce the environmental impacts on fish populations, natural resources, navigation, and livelihoods. Strengthening of international collaboration via the MRC or by individual or multiple country agreements to address Lancang-Mekong’s sustainable transboundary development goals is recommended. When new Lancang-Mekong and tributary dams are built within any of the transboundary watershed countries, additional communities will need to be resettled. Significant environmental and human impacts are observed. Steps will have to be taken by all the concerned countries to prevent these problems and to ensure that people’s livelihoods are restored after resettlement.展开更多
The opening of the Panama Canal in 1913 transformed ocean-shipping and the availability of internationally-traded goods, shortened travel time between the Pacific and Atlantic oceans, increased ship tonnage, and spark...The opening of the Panama Canal in 1913 transformed ocean-shipping and the availability of internationally-traded goods, shortened travel time between the Pacific and Atlantic oceans, increased ship tonnage, and sparked the growth of port authorities on both the Atlantic and Pacific coasts of the Panama Canal. Historically, the United States was number one and China was number two in tons of cargo that pass through the canal annually in the high stakes game of import and export markets. Prior to the construction of the Panama Canal, the most efficient way to cross the 82-kilometer isthmus, between the Port of Panama City on the Pacific and the Port of Colon on the Atlantic, was by mule trails through tropical forests and river transportation. Since the construction of the Panama Canal through tropical forests in the 1910s, pesticides have been essential for managing mosquitoes as well as controlling wetland vegetation that blocked lakes, rivers and the canal. The pri<span>mary objective of this research study is to document the long-term environmental impacts of pesticide and herbicide use in the Panama Canal Zone. Many of these chemicals, including 2, 4,-D, 2, 4, 5-T and DDT, have a long half-life under water and some, like arsenic (As), have no half-life. Pesticides </span>and chemicals flowed into Lake Gatun via surface runoff either in solution or attached to the sediment during the rainy season. The by-product 2,3,7,8-tetrachlorodibenzo-<i>p</i>-dioxin (TCDD) is an unanticipated contaminant created during the manufacture of the herbicide 2,4,5-T. TCDD can bio-accumulate in fish and birds and enter into the human food supply. The extent of the current chemical and pesticide contamination on former U.S. military base grounds and in Lake Gatun is unknown. Systematic soil sampling of current and former military bases, chemical disposal sites and Lake Gatun or the Panama Canal sediments is needed to determine if mitigation is necessary.展开更多
Rhizobium tropici-derived extracellular polymeric substances (EPS) have been used in soils to enhance soil structures and mitigate soil erosions. However, information on their use to improve soil health and fertility ...Rhizobium tropici-derived extracellular polymeric substances (EPS) have been used in soils to enhance soil structures and mitigate soil erosions. However, information on their use to improve soil health and fertility indicators, and plant growth is limited. In a greenhouse study, we investigated their effects on some soil health, soil fertility indices, and the growth of black-eyed peas (Vigna unguiculate). Results showed that soils incubated with EPS significantly increased basal soil respiration, soil microbial biomass, permanganate oxidizable carbon (POC), and potentially mineralizable nitrogen (PMN). The EPS shifted microbial populations from bacteria to fungi and Gram (−ve) to Gram ( ve) bacteria. However, it had little or no effects on soil pH, soil organic matter (SOM), and cation exchange capacity (CEC). The EPS decreased soil moisture loss, increased soil aggregate stability, but delayed blacked-eyed peas germinations in the soils. At 0.1% (w/w) concentrations in soils, there was increase in plant root nodulations and vegetative growth. This study was carried out within 40 days of incubating soils with EPS or growing the black-eyed peas in a greenhouse study. The plant growth parameters were taken before flowering and fruiting. Further studies of the effects of incubating soils with the extracellular polymeric substances on plant growth. Soil microbial biomass, microbial diversities, and other soil fertility indices are deemed necessary.展开更多
The Volga River flows entirely through Russia and the watershed includes three of the country’s ten largest cities. The river is the longest in Europe and western Russia’s principal waterway. The Volga River basin i...The Volga River flows entirely through Russia and the watershed includes three of the country’s ten largest cities. The river is the longest in Europe and western Russia’s principal waterway. The Volga River basin is home to approximately half of Russia’s population and occupies almost two-fifth of European Russia. It covers much of the Volga region and stretches 3530 kilometers from its source in the Valdai Hills to the Caspian Sea, the world’s largest inland water body. Its economic, cultural, and historic importance makes it one of the world’s greatest rivers. The Volga basin makes up 8 percent of the Russian territory. Stalingrad, located on the banks of the Volga River, has been described as the site of the greatest de-feat in the history of the German Army. It is often identified as the turning point on the Eastern Front of WWII, in the war against Germany, and in the entire WWII. The meeting point of the Eurasian Civilization was historically the Volga River. The river has some of the world’s largest reservoirs and is a major source of livelihood for millions of people. Many factories and cities empty their waste including sewage, industrial waste, fertilizers, and pesticides into the Volga River. Pollutants tend to settle in the reservoirs and contain several meters of heavily contaminated muck. The primary objectives are to assess lessons learned, manage, and restore the Volga River system lifeline in Russia.展开更多
The River Nile in Africa is the world’s longest river. It is approximately 6650 km from the mouth of the Mediterranean Sea to its headwater sources, the Blue Nile and White Nile. The Nile drainage basin is about 9674...The River Nile in Africa is the world’s longest river. It is approximately 6650 km from the mouth of the Mediterranean Sea to its headwater sources, the Blue Nile and White Nile. The Nile drainage basin is about 9674 million km2 making it the third-largest drainage basin in the world. The primary research objectives are to document how the periodic flooding of the Nile River was controlled, how the Nile became Egypt’s economic, agricultural, and urban development engine, and provide historical lessons for other countries to learn from when attempting to develop their own river resources and the need to balance many competing economic and environmental interests. A major task for any country attempting to develop their river resources will be to mitigate the negative environmental impacts of economic, agricultural, and urban development while realizing the economic benefits.展开更多
The Upper Mississippi River flows approximately 2000 km from Lake Itasca, Minnesota to Cairo, Illinois where it is confluences with the Ohio River to form the Lower Mississippi River. North of the confluence, numerous...The Upper Mississippi River flows approximately 2000 km from Lake Itasca, Minnesota to Cairo, Illinois where it is confluences with the Ohio River to form the Lower Mississippi River. North of the confluence, numerous snags, sand bars, rapids, and other obstructions made the Upper Mississippi River travel difficult. This paper highlights how the geological and landscape resources of the Upper Mississippi River and tributary watershed were responsible for the successful economic development of this historically rich region of North America. Environmental challenges include an attempt to keep invasive species such as the Asian carp out of the rivers and lakes north of the Twin Cities. In an attempt to protect the Mississippi River resource, Environmental and Conservation groups have opposed continued navigation through Minneapolis and St. Paul and the planned Upper Mississippi River navigation infrastructure restoration by the United States Corps of Engineers including the upper and lower St. Anthony locks and dams. These Environmental, Conservation and Save the River groups are attempting to mitigate the historic highest and best use of the Mississippi River and adjacent watershed, navigation, and economic development, by having the urban river restored to the natural state.展开更多
Transposable elements have been utilized as mutagens to create mutant libraries for functional genomics. Isolation of genomic segments flanking the insertion Mutator （Mu） is a key step in insertion mutagenesis studi...Transposable elements have been utilized as mutagens to create mutant libraries for functional genomics. Isolation of genomic segments flanking the insertion Mutator （Mu） is a key step in insertion mutagenesis studies. Herein, we adopted a modified AFLP method to identify and isolate Mu-flanking fragments from maize. The method consists of the following steps： 1） double-digestion of genomic DNA with Bgl II/Msp I and ligation of digested fragments to the Bgl II- and Msp I-adaptors; 2） enrichment of a subset of Bgl II/Msp I fragments followed by selective amplification of the Mu-flanking fragments; 3） simultaneous display of AFLP bands derived from the flanking regions for both insert and native Mu transposons; 4） identification and isolation of AFLP bands resulting from Mu insertions by comparing the banding profiles between Mu-induced mutants and their parental lines; and 5） confirmation of flanking fragments related to these Mu insertions. Using this approach, we have isolated flanking fragment（s） resulting from Mu insertion for every Mu-induced mutant, and one such fragment, M196-FF, is found to contain a partial sequence of the DNA topoisomerase I gene Topl. Moreover, the modified AFLP method including all restriction enzymes, adaptors and primers has been optimized in this study. The modified AFLP method has been proved to be simple and efficient in the isolation of Mu-flanking fragments and will find its usefulness in the functional genomics of maize.展开更多
Based on the study of REE in Mesozoic-Cenozoic sandstones, the paper indicates that Jurassic Fanghushan and Yuantongshan Formations and Lower Cretaceous Zhougongshan Formation have ∑REE of 157 μg·g^(-1), δ_(Eu...Based on the study of REE in Mesozoic-Cenozoic sandstones, the paper indicates that Jurassic Fanghushan and Yuantongshan Formations and Lower Cretaceous Zhougongshan Formation have ∑REE of 157 μg·g^(-1), δ_(Eu) of 0.69 and (La/Yb)_N of 11.1, which are similar to the Foziling and Luzhenguan Groups, and it implies that the latter may be the source rocks of the former. The Sanjianpu and Heishidu Formations have high REE concentrations (∑REE=264.8 μg·g^(-1), 328.2 μg·g^(-1) respectively), high Eu anomaly (δ_(Eu)=0.57, 0.67 respectively) and lower Eu/Sm ratios (0.18～0.19), which differs from existent metamorphic rocks in the Dabie Mountains, so where their source rocks came from remains to be studied. The REE features of the Zhengyangguan Formation can be comparable to the Dabie complex and Luzhenguan Group, which shows that the Dabie complex had suffered unroofing in Neocene and constituted the source rocks. Mesozoic sandstones in Huainan area have lower REE concentrations (∑REE=80.9 μg·g^(-1)), high Eu anomaly (δ_(Eu)=0.66) and (La/Yb)_N of 5.7, and it indicates that their source rocks may not come from the Dabie Mountains.展开更多
Whenever levees on the Ohio or Mississippi rivers are breached, there are soil damages in the flooded areas that impact agricultural management capacities and crop productivity. Floodwaters coat the entire flooded lan...Whenever levees on the Ohio or Mississippi rivers are breached, there are soil damages in the flooded areas that impact agricultural management capacities and crop productivity. Floodwaters coat the entire flooded land surface with sediments which include a variety of pollutants, nutrients and contaminants. The nature of the sediments in floodwaters varies with the topographical and land use characteristics of the watershed. The soil types, hydro-geologic features, volume of flow, time of year, agricultural use of fertilizers, pesticides, and other chemicals as well as upstream point sources such as sewage treatment plants, storm sewer drainage and other urban land uses will affect the extent of the contamination and fine scale remediation needed. Preliminary characterization and measurement of soils and sediment deposit at three locations that experienced recent natural and man induced levee breaches are analyzed to identify patterns of soil and crop damage. These findings provide guidance to the restoration of craters, gullies, land scoured areas and contaminated sediment depositional sites with a goal to improve decision-making, risk analysis and remedial effectiveness. Recommendations include： （1） improve characterization and measurement of eroded soils and distribution of sediment contaminants after levee breaching; （2） assess contamination effects on soil productivity and long term agricultural production in order to understand the impacts of flooding on agricultural soils; （3） evaluate reconstruction investments needed to repair levees based on return of the land to productivity and increased landscape resilience by reducing vulnerability to future flooding and levee breaching stress.展开更多
A 12-year cover crops study on the effects on SOC sequestration, storage, retention and loss and corn and soybean yields was conducted in southern Illinois. The use of cover crops for the maintenance and restoration o...A 12-year cover crops study on the effects on SOC sequestration, storage, retention and loss and corn and soybean yields was conducted in southern Illinois. The use of cover crops for the maintenance and restoration of soil organic carbon (SOC) and soil productivity of previously eroded soils were evaluated. No-till (NT), chisel plow (CP), and moldboard plow (MP) treatment plots with and without cover crops were established in 2001. The plot area was on sloping with a moderately well drained, eroded soil. The average annual corn and soybean yields were statistically the same for NT, CP, and MP systems with and without cover crops. By 2012, the cover crop treatments had more SOC stock than that without cover crops for the same soil layer and tillage treatment. The NT, CP, and MP treatments all sequestered SOC with cover crops. A pre-treatment SOC stock baseline for rooting zone was used to validate the finding that cover crops sequestered SOC in the topsoil, subsoil and root zone of the NT, CP and MP treatments during the 12-year study. Additional sequestered SOC was lost as a result of being transported off of the plots and retained in lower slopes, transported to the stream or released to atmosphere.展开更多
Prunus africana is an endangered medicinal species and has been classified as a priority for domestication in Cameroon.However,the seeds rapidly lose their viability during storage at room temperature after 2–3 month...Prunus africana is an endangered medicinal species and has been classified as a priority for domestication in Cameroon.However,the seeds rapidly lose their viability during storage at room temperature after 2–3 months.This study aimed to improve seed germination of P.africana by germinating at different temperatures(4℃,28℃)using different concentrations of growth stimulators(sodium nitrate and gibberellic acid)and different concentrations of salts.P.africana seeds had 91.7%germination at 4C after 1 month of storage.Growth regulators considerably influenced germination after 6 months and reached 66.0%with 10 mM gibberellic acid and 100%with 10 mM sodium nitrate.Approximately three shoots per seed were developed,an indication of polyembryony.Histochemical analyses revealed the presence of protein-like bodies close to the embryo axis and accumulations of starch after 7 days of germination.After 14 days,amyloplasts and dark protein bodies of various sizes were observed.The outcome of this study will contribute to improve the germination of P.africana for better domestication and conservation.展开更多
Temperate grassland soils are typically a sink for carbon. However, it is estimated that up to 99% of tallgrass prairies in North America have been converted to another land use. These conversions can lead to increase...Temperate grassland soils are typically a sink for carbon. However, it is estimated that up to 99% of tallgrass prairies in North America have been converted to another land use. These conversions can lead to increased soil erosion and soil organic carbon (SOC) mineralization rates, turning a large carbon sink into a source. The purpose of this study was to compare by land use the retention of SOC, TSN, and fly ash on sloping landscapes with an emphasis on measuring the subsoil in addition to the surface soil. Eight paired plots were established on adjacent, sloping landscape profiles in western Iowa;one site a cropland and the other a remnant tallgrass prairie. The prairie landscape had a baseline SOC stock of 232 Mg-C ha-1. After roughly 150 years of agriculture the cropland had 52% less SOC, 39% less TSN, and 22% less fly ash which equates to annual losses of 0.55 Mg-C ha-1 yr-1, 0.04 Mg-N ha-1 yr-1, and 0.0002 Mg-fly ash ha-1 yr-1.展开更多
Discoveries in Charles Darwin’s laboratory led to modern herbicides. Darwin discovered the internal mechanism that directed plants to grow toward sunlight and sources of water. Scientists in Europe and America later ...Discoveries in Charles Darwin’s laboratory led to modern herbicides. Darwin discovered the internal mechanism that directed plants to grow toward sunlight and sources of water. Scientists in Europe and America later called this mechanism a plant’s hormone response system. Administrators and scientists, including Dr. Ezra J. Kraus, the Head of the Botany Department at the University of Chicago and a plant physiologist, suggested on the eve of WWII that weed killers had significant military value as chemical weapons. Dr. Kraus obtained access to a synthetic chemical, 2,4-D, and found that when the chemical was absorbed through the leaves of plants, it destroyed a plant’s hormones. After exposure, the plant experienced rapid and uncontrolled growth, and then the leaves shriveled, died and fell off. Dr. Kraus obtained funding for his Department of Botany research program from Department of Defense (DOD) during World War II (WWII). Camp Detrick (Biological Weapons Laboratory) scientists later obtained samples of newly created 2,4,5-T which contained unknown amounts of the by-product dioxin TCDD. In the 1950s and 1960s, Fort Detrick military scientists formulated the herbicide Agent Orange, which was a 50 - 50 mixture of 2,4-D and 2,4,5-T. These dual purpose herbicides were used by DOD and USDA. American and European farmers in the 1940s used 2,4-D and 2,4,5-T to eliminate weeds from pastureland and cropland. After WWII, synthetic herbicides (and pesticides) development continued in tandem with production of synthetic fertilizers and breeding of high-yield plant varieties. These new agricultural products were then shipped worldwide to increase crop yields, as part of the Green Revolution. This new system of agricultural technologies was intended to eliminate global starvation and increase food security by increasing field and farm crop yields. In contrast, the goal of military use of herbicides, as chemical weapons, was to defoliate jungle forests and destroy food crops as a strategy to win battles and wars. The primary objective of this research study is to describe how agricultural herbicides became tactical chemical weapons. A current assessment will address the environmental impacts of military and environmental chemical weapons on the United States and Vietnam ecosystems and need for additional dioxin TCDD hotspot clean-up efforts.展开更多
Land subsidence and rising sea levels could result in 40% of the Mekong Delta being covered by the South China Sea within the next few decades. The impact of groundwater withdrawal, in the SE Asia mega deltas of Gange...Land subsidence and rising sea levels could result in 40% of the Mekong Delta being covered by the South China Sea within the next few decades. The impact of groundwater withdrawal, in the SE Asia mega deltas of Ganges-Brahmaputra Delta, Jakarta Delta, Chao Phraya Delta and Mekong Delta, is a major reason these deltas are sinking. There are lessons to be learned from both failures and successful remediation efforts in other mega deltas as Vietnam policy makers seek to address Mekong Delta subsidence. Without a significant Vietnam government remediation and mitigation efforts, land subsidence in the Mekong Delta will continue. Land subsidence has occurred in the Mekong Delta as a result of the retention of sediments behind the China and Laos dams on the main stem of the Mekong River, reduced flooding peaks, climate change, sea level rise, storm surges and flooding. In addition, subsidence has been exascerbated by compaction, groundwater extraction for shrimp ponds, rice paddies and the household and drinking water needs of approximately 20 million people living on the Mekong Delta in Vietnam and Cambodia. The Mekong Delta shorelines are eroding and significant land areas, including wetlands, are becoming open water. The wetlands and land mass are also subsiding as a result of the reduction in sediment deposition. Large dams on the mainstem of the Mekong River in China and Laos have reduced peak flows and reduced sediment loads in lower Mekong River. Population and industrial growth have increased groundwater extraction and salt water intrusion as the delta subsides leading to consolidation and reduction in the current plumes flowing into the South China Sea. The primary objective of this paper is to assess the impact of groundwater withdrawals for rice paddies, shrimp ponds, aquaculture, industry and drinking water on Mekong Delta land subsidence. The secondary objective is to identify mitigation efforts used in other Southeast Asia deltas and make remediation recommendations for the sinking Mekong Delta. Promising mitigation approaches are injecting river water deep into the underlying alluvial sediments, return of the sediments trapped in China and Laos reservoirs to the Mekong River mainstem, increase in the Mekong River flooding peaks, and construction of sea and floodwalls, dykes, polders and levees. The addition of Mekong River sediments to build up existing floodplains, the reduction of coastal shoreline erosion, the planting of mangroves and protection of urban and agricultural areas from being covered by the South China Sea are strategies that could help remediate land subsidence in the Mekong Delta.展开更多
The invasion of nonnative plants is considered one of the main threats to the structure and function of North American ecosystems. Moreover, they can alter ecosystem processes and reduce biodiversity. In arid and semi...The invasion of nonnative plants is considered one of the main threats to the structure and function of North American ecosystems. Moreover, they can alter ecosystem processes and reduce biodiversity. In arid and semi-arid region of North America, the species of European annual grass Bromus tectorum L. is an outstanding example of these problems, which not only increase the fire density and change the fire regime, but replace native communities. Therefore, there are amount of researches on B. tectorum, including resource acquisition, water use efficiency and growth. Whereas the relevant research on the morphology of diaspore is scare. Diaspores have a fundamental role in seed germination and seedling establishment. Besides, as an important link between different generations, diaspores have a vital significance on individual reproduction and population extension. Hence, dias- pores under selection for studying have an important implication. This study compares differences in seed mor- phology for Bromus tectorum collected from the United States, Kazakhstan, and Xinjiang of China. The following indices of B. tectorum diaspores were analyzed： size, thickness of covering layers, and micromorphological char- acteristics of the base, middle and transition area of diaspores as well as of the awn. Micromorphology of the lemma and the cross-section of the diaspore were observed by scanning electron microscopy. Results showed that thick- ness of the lemma and the palea of diaspores from B. tectorum-infested grasslands in the United States were re- duced （P〈0.05）, likely because of environmental influences. This reduction facilitated the germination of diaspores and lowered the resistance of B. tectorum to adverse environmental conditions. The length of the awn also in- creased significantly （P〈0.05）, which helped in dispersal and anchoring of diaspores. Therefore, B. tectorum adapted ecologically to its new environment in the United States by strengthening its establishment ability. However, the defense capability of B. tectorum decreased. These results fit the evolution of increased competitive ability hy- pothesis （EICA） of invasive species. Analysis of various cells on the lemma revealed that prickle densities and col- lapsed, long epidermal cells were easily influenced by environmental factors such as temperature and moisture because of the physiologic function of these structures on silicon accumulation. However, the form and the position of silica cells, which were not greatly influenced by environmental factors, might be genetically controlled. Studying these structures at the microscopic level helps define the relationship between the diaspore and its environment. This study has a reference value for future studies on B. tectorum.展开更多
The primary objective of this research was to predict changes in soil organic carbon (SOC) and total soil nitrogen (TSN) stocks as a result of land use change from prairie to agricultural land if the mesic-frigid temp...The primary objective of this research was to predict changes in soil organic carbon (SOC) and total soil nitrogen (TSN) stocks as a result of land use change from prairie to agricultural land if the mesic-frigid temperature line moved north in the US and the former frigid soils were cultivated. The conversion of prairie to agricultural use, as a result of climate shift, would release SOC to atmosphere and enhance greenhouse gas emissions. The SOC and TSN differences between the prairie site and agricultural land were compared in South Dakota. The agricultural land had 18% less SOC and 16% less TSN or only half of the expected loss from prairie levels. An attempt was made to document the land use history of the prairie site to understand why SOC and TSN losses were less than anticipated. The fly ash concentration levels on prairie side slopes suggested that the prairie was historically disturbed and eroded. Intensive grazing and burning contributed to the disturbance. The SOC and TSN stock losses appear to represent the minimal change that would occur in the next 100-year time period if a prairie was shifted to agricultural use as a result of climate shift and the mesic-frigid temperature line in US was to move north.展开更多
A Walnut Gulch rainfall simulator was used to determine runoff water quality and salt balance of a Sandy Loam moderately saline-alkaline site containing 0.27%of gypsum near Moab,Utah.Four rainfall intensities correspo...A Walnut Gulch rainfall simulator was used to determine runoff water quality and salt balance of a Sandy Loam moderately saline-alkaline site containing 0.27%of gypsum near Moab,Utah.Four rainfall intensities corresponding to 2,10,25 and 50-year storm return intervals were applied to dry soil.During each rainfall simulation,time-stamped runoff samples were also collected for the determination of ions concentration.Soil water and solute content by depth increments were determined before and after simulations.All correlation coefficients between the applied simulation water and the amounts of Cl-,SO42-,NO3-and sum of anions in runoff water were positive and ranged between 0.922 and 0.999.The correlation coefficients for Ca2+,Mg2+,Na+,K+and sum of cations ranged between 0.783 and 0.983.We concluded from the data analysis that:(1)The amounts of ions in simulation water and in runoff water represent less than 1%of sum of the soil soluble content before rainfall simulation.(2)The CEC contained about 250%the sum of cation in saturated extract.(3)The very small amount of gypsum in the soil contained 50%the sum of saturated extract ions.This means that special attention should be paid to CEC and gypsum content in the management of such soils.Moreover,when modeling runoff and water quality from soils with these properties the modelers must include suitable subroutines considering gypsum and CEC of the soil for accurate prediction of runoff water quality.展开更多
文摘The Suez Canal is a unique sea-level waterway between northern Africa and southern Asia that connects the Mediterranean Sea to the Red Sea via the Isthmus of Suez. The canal’s artificial navigation route substantially reduced the sailing distance between countries in Europe and East Asia and offered a more direct route between the North Atlantic Ocean and the Indian Ocean through the Mediterranean Sea and the Red Sea. The primary objective of this study is to document the historical, economical, and environmental impacts of connecting the Mediterranean Sea and the Red Sea via a canal. After the completion of the Suez Canal in 1869 the canal became an economically lifeline for Egypt. However, the economic gains were partially offset by negative environmental impacts. The impact of port activities on the environment depends on their cargo volume and location, seaports can have an impact on the air quality and therefore on the health of the communities along the Suez Canal. The salinity barrier to migration was removed and animals and plants from the Red Sea began colonizing the eastern Mediterranean. Since the 1880s, species from the Indo-Pacific Ocean have been introduced, via the canal, into the Mediterranean ecosystem. They are endangering some local and endemic species and impacting the ecology. The results showed significant changes in the shoreline and land cover due to climate change and anthropogenic activities that necessitate the implementation of adequate protective measures. The findings of this study may assist policymakers in formulating adaptation plans to protect this crucial area, the communities along the Suez Canal and the Red Sea and Mediterranean ports, from climate change and human activities.
文摘Environmental sociology and the sociology of natural resources are two key subdisciplines of the sociological study on the interactions between nature and human society.Previous discussion on the relationships of these two fields has largely focused on their distinctions and synthesis in western(particularly American) academia.Environmental sociology emerged as an important sociological subdiscipline in China in the early 1990s and is under vigorous disciplinary construction at present.By contrast,the sociology of natural resources is still a novel term for most Chinese researchers.This article provides a systematic review of recent literature on the relationships between environmental and natural resource sociologies,which should provide important implications for the further development of environmental sociology in China.
文摘The Dnieper River headwaters are in Russia’s Valdai Hills and the river flows south to the Black Sea. The Dnieper River provides a waterway in which to transport goods to and from various European nations. In addition, the dams on the river provide hydro power. There are approximately 2260 km of Dnieper waterways in Russia, in Belarus, and within Ukraine. The Dnieper River has numerous urban centers including Smolensk in Russia, Mogilev in Belarus and Kiev and Zaporizhzhya in Ukraine. The worst nuclear accident in history unfolded, in the Dnieper River watershed, in northern Ukraine as a reactor at the Chernobyl nuclear power plant exploded and burned. After an accident, such as Chernobyl, radionuclide contaminated bodies of water via direct deposition from the air, discharge as effluent or indirectly from catchment basin washout. When radionuclides contaminate large bodies of water, they are quickly dispersing and accumulate in water bottom sediments, benthos, aquatic plants, and bottom feeding fish. The main pathways to humans are through contamination of drinking-water, from use of water for irrigation of food crops, and consumption of contaminated fish. Kakhovka Dam on the Dnieper River was destroyed during the Russian-Ukraine conflict and the dam needs to rebuild as soon as possible. Perhaps lessons learned by the US Army Corps of Engineers (USACE), after using TNT to blow up the Birds Point front line levee on the Mississippi River in May of 2011, can be applied to the man-induced 2023 Kakhovka Dam breach. The Birds Point man-induced levee breaches and subsequent flooding of farmland resulted in the loss of the 2011 crops and damaged the future soil productivity. The strong current and sweep of the water through the three man-induced levee breaches on the New Madrid floodway levee created deep gullies, displaced tons of soil, and damaged irrigation equipment, farms, and homes. The New Madrid floodway agricultural lands were restored, and the environmental damages were mitigated. The Kakhovka Dam destruction caused widespread flooding which affected settlements and farmland across the Dnieper watershed. The presence and breach-induced redistribution of Chernobyl-derived nuclides is an additional condition not present at the New Madrid man-induced levee breach. Four canal networks have become disconnected from the feeder reservoir. The canals were the source of drinking water for 700,000 people living in southern Ukraine. The Kakhovka canals also provided irrigation for vast areas of farmland. The water loss from the canals adversely affected food production in the region. The primary objectives of this paper are to assess lessons learned by the USACE and apply them in Ukraine to help restore and manage the Dnieper lifeline and watershed.
文摘The Lancang-Mekong River in China, Laos, Thailand, Myanmar, Cambodia, and Vietnam is the soul and heart of mainland Southeast Asia. Over 60 million people depend on the river and its tributaries for food, transportation, water, and other necessities of life. The river supports one of the world’s most diverse fisheries, second only to Brazil’s Amazon River. Lancang-Mekong and tributaries are already heavily dammed primarily in China, Laos, Thailand, and Cambodia, with many more dams planned or under construction. Dams can worsen the impact of periodic droughts in the Lancang-Mekong basin and block the river’s “pulse effect” that spreads water and nutrients needed for fishing and farming onto the floodplains and delta. The headwaters of the Lancang are in China and its waters are considered a national resource. China regards the Lancang, Yangtze and Yellow rivers as a free resource rather than a shared resource. The primary difference between these rivers is the Lancang flows from China into and through other countries and not directly into a sea or ocean. China and Myanmar have not joined the Mekong River Commission (MRC) as full members but have been Dialogue Partners since 1996. Over the past thirty years, China’s Lancang policies and actions have reflected its national resource interests. China has actively engaged with individual transboundary countries at various levels including environmental, conservation, and economic agreements. The primary objective of this study is to assess the environmental and human impacts of all Lancang-Mekong mainstem and tributary dams and the plans by many countries for more hydropower utilizing the potential of the river as the continent’s energy lifeline. Future dams need to include fish ladders and navigation locks to reduce the environmental impacts on fish populations, natural resources, navigation, and livelihoods. Strengthening of international collaboration via the MRC or by individual or multiple country agreements to address Lancang-Mekong’s sustainable transboundary development goals is recommended. When new Lancang-Mekong and tributary dams are built within any of the transboundary watershed countries, additional communities will need to be resettled. Significant environmental and human impacts are observed. Steps will have to be taken by all the concerned countries to prevent these problems and to ensure that people’s livelihoods are restored after resettlement.
文摘The opening of the Panama Canal in 1913 transformed ocean-shipping and the availability of internationally-traded goods, shortened travel time between the Pacific and Atlantic oceans, increased ship tonnage, and sparked the growth of port authorities on both the Atlantic and Pacific coasts of the Panama Canal. Historically, the United States was number one and China was number two in tons of cargo that pass through the canal annually in the high stakes game of import and export markets. Prior to the construction of the Panama Canal, the most efficient way to cross the 82-kilometer isthmus, between the Port of Panama City on the Pacific and the Port of Colon on the Atlantic, was by mule trails through tropical forests and river transportation. Since the construction of the Panama Canal through tropical forests in the 1910s, pesticides have been essential for managing mosquitoes as well as controlling wetland vegetation that blocked lakes, rivers and the canal. The pri<span>mary objective of this research study is to document the long-term environmental impacts of pesticide and herbicide use in the Panama Canal Zone. Many of these chemicals, including 2, 4,-D, 2, 4, 5-T and DDT, have a long half-life under water and some, like arsenic (As), have no half-life. Pesticides </span>and chemicals flowed into Lake Gatun via surface runoff either in solution or attached to the sediment during the rainy season. The by-product 2,3,7,8-tetrachlorodibenzo-<i>p</i>-dioxin (TCDD) is an unanticipated contaminant created during the manufacture of the herbicide 2,4,5-T. TCDD can bio-accumulate in fish and birds and enter into the human food supply. The extent of the current chemical and pesticide contamination on former U.S. military base grounds and in Lake Gatun is unknown. Systematic soil sampling of current and former military bases, chemical disposal sites and Lake Gatun or the Panama Canal sediments is needed to determine if mitigation is necessary.
文摘Rhizobium tropici-derived extracellular polymeric substances (EPS) have been used in soils to enhance soil structures and mitigate soil erosions. However, information on their use to improve soil health and fertility indicators, and plant growth is limited. In a greenhouse study, we investigated their effects on some soil health, soil fertility indices, and the growth of black-eyed peas (Vigna unguiculate). Results showed that soils incubated with EPS significantly increased basal soil respiration, soil microbial biomass, permanganate oxidizable carbon (POC), and potentially mineralizable nitrogen (PMN). The EPS shifted microbial populations from bacteria to fungi and Gram (−ve) to Gram ( ve) bacteria. However, it had little or no effects on soil pH, soil organic matter (SOM), and cation exchange capacity (CEC). The EPS decreased soil moisture loss, increased soil aggregate stability, but delayed blacked-eyed peas germinations in the soils. At 0.1% (w/w) concentrations in soils, there was increase in plant root nodulations and vegetative growth. This study was carried out within 40 days of incubating soils with EPS or growing the black-eyed peas in a greenhouse study. The plant growth parameters were taken before flowering and fruiting. Further studies of the effects of incubating soils with the extracellular polymeric substances on plant growth. Soil microbial biomass, microbial diversities, and other soil fertility indices are deemed necessary.
文摘The Volga River flows entirely through Russia and the watershed includes three of the country’s ten largest cities. The river is the longest in Europe and western Russia’s principal waterway. The Volga River basin is home to approximately half of Russia’s population and occupies almost two-fifth of European Russia. It covers much of the Volga region and stretches 3530 kilometers from its source in the Valdai Hills to the Caspian Sea, the world’s largest inland water body. Its economic, cultural, and historic importance makes it one of the world’s greatest rivers. The Volga basin makes up 8 percent of the Russian territory. Stalingrad, located on the banks of the Volga River, has been described as the site of the greatest de-feat in the history of the German Army. It is often identified as the turning point on the Eastern Front of WWII, in the war against Germany, and in the entire WWII. The meeting point of the Eurasian Civilization was historically the Volga River. The river has some of the world’s largest reservoirs and is a major source of livelihood for millions of people. Many factories and cities empty their waste including sewage, industrial waste, fertilizers, and pesticides into the Volga River. Pollutants tend to settle in the reservoirs and contain several meters of heavily contaminated muck. The primary objectives are to assess lessons learned, manage, and restore the Volga River system lifeline in Russia.
文摘The River Nile in Africa is the world’s longest river. It is approximately 6650 km from the mouth of the Mediterranean Sea to its headwater sources, the Blue Nile and White Nile. The Nile drainage basin is about 9674 million km2 making it the third-largest drainage basin in the world. The primary research objectives are to document how the periodic flooding of the Nile River was controlled, how the Nile became Egypt’s economic, agricultural, and urban development engine, and provide historical lessons for other countries to learn from when attempting to develop their own river resources and the need to balance many competing economic and environmental interests. A major task for any country attempting to develop their river resources will be to mitigate the negative environmental impacts of economic, agricultural, and urban development while realizing the economic benefits.
文摘The Upper Mississippi River flows approximately 2000 km from Lake Itasca, Minnesota to Cairo, Illinois where it is confluences with the Ohio River to form the Lower Mississippi River. North of the confluence, numerous snags, sand bars, rapids, and other obstructions made the Upper Mississippi River travel difficult. This paper highlights how the geological and landscape resources of the Upper Mississippi River and tributary watershed were responsible for the successful economic development of this historically rich region of North America. Environmental challenges include an attempt to keep invasive species such as the Asian carp out of the rivers and lakes north of the Twin Cities. In an attempt to protect the Mississippi River resource, Environmental and Conservation groups have opposed continued navigation through Minneapolis and St. Paul and the planned Upper Mississippi River navigation infrastructure restoration by the United States Corps of Engineers including the upper and lower St. Anthony locks and dams. These Environmental, Conservation and Save the River groups are attempting to mitigate the historic highest and best use of the Mississippi River and adjacent watershed, navigation, and economic development, by having the urban river restored to the natural state.
文摘Transposable elements have been utilized as mutagens to create mutant libraries for functional genomics. Isolation of genomic segments flanking the insertion Mutator （Mu） is a key step in insertion mutagenesis studies. Herein, we adopted a modified AFLP method to identify and isolate Mu-flanking fragments from maize. The method consists of the following steps： 1） double-digestion of genomic DNA with Bgl II/Msp I and ligation of digested fragments to the Bgl II- and Msp I-adaptors; 2） enrichment of a subset of Bgl II/Msp I fragments followed by selective amplification of the Mu-flanking fragments; 3） simultaneous display of AFLP bands derived from the flanking regions for both insert and native Mu transposons; 4） identification and isolation of AFLP bands resulting from Mu insertions by comparing the banding profiles between Mu-induced mutants and their parental lines; and 5） confirmation of flanking fragments related to these Mu insertions. Using this approach, we have isolated flanking fragment（s） resulting from Mu insertion for every Mu-induced mutant, and one such fragment, M196-FF, is found to contain a partial sequence of the DNA topoisomerase I gene Topl. Moreover, the modified AFLP method including all restriction enzymes, adaptors and primers has been optimized in this study. The modified AFLP method has been proved to be simple and efficient in the isolation of Mu-flanking fragments and will find its usefulness in the functional genomics of maize.
文摘Based on the study of REE in Mesozoic-Cenozoic sandstones, the paper indicates that Jurassic Fanghushan and Yuantongshan Formations and Lower Cretaceous Zhougongshan Formation have ∑REE of 157 μg·g^(-1), δ_(Eu) of 0.69 and (La/Yb)_N of 11.1, which are similar to the Foziling and Luzhenguan Groups, and it implies that the latter may be the source rocks of the former. The Sanjianpu and Heishidu Formations have high REE concentrations (∑REE=264.8 μg·g^(-1), 328.2 μg·g^(-1) respectively), high Eu anomaly (δ_(Eu)=0.57, 0.67 respectively) and lower Eu/Sm ratios (0.18～0.19), which differs from existent metamorphic rocks in the Dabie Mountains, so where their source rocks came from remains to be studied. The REE features of the Zhengyangguan Formation can be comparable to the Dabie complex and Luzhenguan Group, which shows that the Dabie complex had suffered unroofing in Neocene and constituted the source rocks. Mesozoic sandstones in Huainan area have lower REE concentrations (∑REE=80.9 μg·g^(-1)), high Eu anomaly (δ_(Eu)=0.66) and (La/Yb)_N of 5.7, and it indicates that their source rocks may not come from the Dabie Mountains.
文摘Whenever levees on the Ohio or Mississippi rivers are breached, there are soil damages in the flooded areas that impact agricultural management capacities and crop productivity. Floodwaters coat the entire flooded land surface with sediments which include a variety of pollutants, nutrients and contaminants. The nature of the sediments in floodwaters varies with the topographical and land use characteristics of the watershed. The soil types, hydro-geologic features, volume of flow, time of year, agricultural use of fertilizers, pesticides, and other chemicals as well as upstream point sources such as sewage treatment plants, storm sewer drainage and other urban land uses will affect the extent of the contamination and fine scale remediation needed. Preliminary characterization and measurement of soils and sediment deposit at three locations that experienced recent natural and man induced levee breaches are analyzed to identify patterns of soil and crop damage. These findings provide guidance to the restoration of craters, gullies, land scoured areas and contaminated sediment depositional sites with a goal to improve decision-making, risk analysis and remedial effectiveness. Recommendations include： （1） improve characterization and measurement of eroded soils and distribution of sediment contaminants after levee breaching; （2） assess contamination effects on soil productivity and long term agricultural production in order to understand the impacts of flooding on agricultural soils; （3） evaluate reconstruction investments needed to repair levees based on return of the land to productivity and increased landscape resilience by reducing vulnerability to future flooding and levee breaching stress.
文摘A 12-year cover crops study on the effects on SOC sequestration, storage, retention and loss and corn and soybean yields was conducted in southern Illinois. The use of cover crops for the maintenance and restoration of soil organic carbon (SOC) and soil productivity of previously eroded soils were evaluated. No-till (NT), chisel plow (CP), and moldboard plow (MP) treatment plots with and without cover crops were established in 2001. The plot area was on sloping with a moderately well drained, eroded soil. The average annual corn and soybean yields were statistically the same for NT, CP, and MP systems with and without cover crops. By 2012, the cover crop treatments had more SOC stock than that without cover crops for the same soil layer and tillage treatment. The NT, CP, and MP treatments all sequestered SOC with cover crops. A pre-treatment SOC stock baseline for rooting zone was used to validate the finding that cover crops sequestered SOC in the topsoil, subsoil and root zone of the NT, CP and MP treatments during the 12-year study. Additional sequestered SOC was lost as a result of being transported off of the plots and retained in lower slopes, transported to the stream or released to atmosphere.
基金This work was supported by The Rufford Small Grants Foundation to Niemenak Nicolas(RSG Ref.70.05.09)and by the UNESCO 1’Oreal Fellowship for Women in Science Program to Nzweundji Justine Germo.The Alexander von Humboldt Foundation is also acknowledged for material donation to Niemenak Nicolas.
文摘Prunus africana is an endangered medicinal species and has been classified as a priority for domestication in Cameroon.However,the seeds rapidly lose their viability during storage at room temperature after 2–3 months.This study aimed to improve seed germination of P.africana by germinating at different temperatures(4℃,28℃)using different concentrations of growth stimulators(sodium nitrate and gibberellic acid)and different concentrations of salts.P.africana seeds had 91.7%germination at 4C after 1 month of storage.Growth regulators considerably influenced germination after 6 months and reached 66.0%with 10 mM gibberellic acid and 100%with 10 mM sodium nitrate.Approximately three shoots per seed were developed,an indication of polyembryony.Histochemical analyses revealed the presence of protein-like bodies close to the embryo axis and accumulations of starch after 7 days of germination.After 14 days,amyloplasts and dark protein bodies of various sizes were observed.The outcome of this study will contribute to improve the germination of P.africana for better domestication and conservation.
文摘Temperate grassland soils are typically a sink for carbon. However, it is estimated that up to 99% of tallgrass prairies in North America have been converted to another land use. These conversions can lead to increased soil erosion and soil organic carbon (SOC) mineralization rates, turning a large carbon sink into a source. The purpose of this study was to compare by land use the retention of SOC, TSN, and fly ash on sloping landscapes with an emphasis on measuring the subsoil in addition to the surface soil. Eight paired plots were established on adjacent, sloping landscape profiles in western Iowa;one site a cropland and the other a remnant tallgrass prairie. The prairie landscape had a baseline SOC stock of 232 Mg-C ha-1. After roughly 150 years of agriculture the cropland had 52% less SOC, 39% less TSN, and 22% less fly ash which equates to annual losses of 0.55 Mg-C ha-1 yr-1, 0.04 Mg-N ha-1 yr-1, and 0.0002 Mg-fly ash ha-1 yr-1.
文摘Discoveries in Charles Darwin’s laboratory led to modern herbicides. Darwin discovered the internal mechanism that directed plants to grow toward sunlight and sources of water. Scientists in Europe and America later called this mechanism a plant’s hormone response system. Administrators and scientists, including Dr. Ezra J. Kraus, the Head of the Botany Department at the University of Chicago and a plant physiologist, suggested on the eve of WWII that weed killers had significant military value as chemical weapons. Dr. Kraus obtained access to a synthetic chemical, 2,4-D, and found that when the chemical was absorbed through the leaves of plants, it destroyed a plant’s hormones. After exposure, the plant experienced rapid and uncontrolled growth, and then the leaves shriveled, died and fell off. Dr. Kraus obtained funding for his Department of Botany research program from Department of Defense (DOD) during World War II (WWII). Camp Detrick (Biological Weapons Laboratory) scientists later obtained samples of newly created 2,4,5-T which contained unknown amounts of the by-product dioxin TCDD. In the 1950s and 1960s, Fort Detrick military scientists formulated the herbicide Agent Orange, which was a 50 - 50 mixture of 2,4-D and 2,4,5-T. These dual purpose herbicides were used by DOD and USDA. American and European farmers in the 1940s used 2,4-D and 2,4,5-T to eliminate weeds from pastureland and cropland. After WWII, synthetic herbicides (and pesticides) development continued in tandem with production of synthetic fertilizers and breeding of high-yield plant varieties. These new agricultural products were then shipped worldwide to increase crop yields, as part of the Green Revolution. This new system of agricultural technologies was intended to eliminate global starvation and increase food security by increasing field and farm crop yields. In contrast, the goal of military use of herbicides, as chemical weapons, was to defoliate jungle forests and destroy food crops as a strategy to win battles and wars. The primary objective of this research study is to describe how agricultural herbicides became tactical chemical weapons. A current assessment will address the environmental impacts of military and environmental chemical weapons on the United States and Vietnam ecosystems and need for additional dioxin TCDD hotspot clean-up efforts.
文摘Land subsidence and rising sea levels could result in 40% of the Mekong Delta being covered by the South China Sea within the next few decades. The impact of groundwater withdrawal, in the SE Asia mega deltas of Ganges-Brahmaputra Delta, Jakarta Delta, Chao Phraya Delta and Mekong Delta, is a major reason these deltas are sinking. There are lessons to be learned from both failures and successful remediation efforts in other mega deltas as Vietnam policy makers seek to address Mekong Delta subsidence. Without a significant Vietnam government remediation and mitigation efforts, land subsidence in the Mekong Delta will continue. Land subsidence has occurred in the Mekong Delta as a result of the retention of sediments behind the China and Laos dams on the main stem of the Mekong River, reduced flooding peaks, climate change, sea level rise, storm surges and flooding. In addition, subsidence has been exascerbated by compaction, groundwater extraction for shrimp ponds, rice paddies and the household and drinking water needs of approximately 20 million people living on the Mekong Delta in Vietnam and Cambodia. The Mekong Delta shorelines are eroding and significant land areas, including wetlands, are becoming open water. The wetlands and land mass are also subsiding as a result of the reduction in sediment deposition. Large dams on the mainstem of the Mekong River in China and Laos have reduced peak flows and reduced sediment loads in lower Mekong River. Population and industrial growth have increased groundwater extraction and salt water intrusion as the delta subsides leading to consolidation and reduction in the current plumes flowing into the South China Sea. The primary objective of this paper is to assess the impact of groundwater withdrawals for rice paddies, shrimp ponds, aquaculture, industry and drinking water on Mekong Delta land subsidence. The secondary objective is to identify mitigation efforts used in other Southeast Asia deltas and make remediation recommendations for the sinking Mekong Delta. Promising mitigation approaches are injecting river water deep into the underlying alluvial sediments, return of the sediments trapped in China and Laos reservoirs to the Mekong River mainstem, increase in the Mekong River flooding peaks, and construction of sea and floodwalls, dykes, polders and levees. The addition of Mekong River sediments to build up existing floodplains, the reduction of coastal shoreline erosion, the planting of mangroves and protection of urban and agricultural areas from being covered by the South China Sea are strategies that could help remediate land subsidence in the Mekong Delta.
基金supported by the International Science and Technology Cooperation Program of China (2010DFA92720-06)with partial support to RSN from the US National Science Foundation (1047575) and the Nevada Agricultural Experiment Station
文摘The invasion of nonnative plants is considered one of the main threats to the structure and function of North American ecosystems. Moreover, they can alter ecosystem processes and reduce biodiversity. In arid and semi-arid region of North America, the species of European annual grass Bromus tectorum L. is an outstanding example of these problems, which not only increase the fire density and change the fire regime, but replace native communities. Therefore, there are amount of researches on B. tectorum, including resource acquisition, water use efficiency and growth. Whereas the relevant research on the morphology of diaspore is scare. Diaspores have a fundamental role in seed germination and seedling establishment. Besides, as an important link between different generations, diaspores have a vital significance on individual reproduction and population extension. Hence, dias- pores under selection for studying have an important implication. This study compares differences in seed mor- phology for Bromus tectorum collected from the United States, Kazakhstan, and Xinjiang of China. The following indices of B. tectorum diaspores were analyzed： size, thickness of covering layers, and micromorphological char- acteristics of the base, middle and transition area of diaspores as well as of the awn. Micromorphology of the lemma and the cross-section of the diaspore were observed by scanning electron microscopy. Results showed that thick- ness of the lemma and the palea of diaspores from B. tectorum-infested grasslands in the United States were re- duced （P〈0.05）, likely because of environmental influences. This reduction facilitated the germination of diaspores and lowered the resistance of B. tectorum to adverse environmental conditions. The length of the awn also in- creased significantly （P〈0.05）, which helped in dispersal and anchoring of diaspores. Therefore, B. tectorum adapted ecologically to its new environment in the United States by strengthening its establishment ability. However, the defense capability of B. tectorum decreased. These results fit the evolution of increased competitive ability hy- pothesis （EICA） of invasive species. Analysis of various cells on the lemma revealed that prickle densities and col- lapsed, long epidermal cells were easily influenced by environmental factors such as temperature and moisture because of the physiologic function of these structures on silicon accumulation. However, the form and the position of silica cells, which were not greatly influenced by environmental factors, might be genetically controlled. Studying these structures at the microscopic level helps define the relationship between the diaspore and its environment. This study has a reference value for future studies on B. tectorum.
文摘The primary objective of this research was to predict changes in soil organic carbon (SOC) and total soil nitrogen (TSN) stocks as a result of land use change from prairie to agricultural land if the mesic-frigid temperature line moved north in the US and the former frigid soils were cultivated. The conversion of prairie to agricultural use, as a result of climate shift, would release SOC to atmosphere and enhance greenhouse gas emissions. The SOC and TSN differences between the prairie site and agricultural land were compared in South Dakota. The agricultural land had 18% less SOC and 16% less TSN or only half of the expected loss from prairie levels. An attempt was made to document the land use history of the prairie site to understand why SOC and TSN losses were less than anticipated. The fly ash concentration levels on prairie side slopes suggested that the prairie was historically disturbed and eroded. Intensive grazing and burning contributed to the disturbance. The SOC and TSN stock losses appear to represent the minimal change that would occur in the next 100-year time period if a prairie was shifted to agricultural use as a result of climate shift and the mesic-frigid temperature line in US was to move north.
文摘A Walnut Gulch rainfall simulator was used to determine runoff water quality and salt balance of a Sandy Loam moderately saline-alkaline site containing 0.27%of gypsum near Moab,Utah.Four rainfall intensities corresponding to 2,10,25 and 50-year storm return intervals were applied to dry soil.During each rainfall simulation,time-stamped runoff samples were also collected for the determination of ions concentration.Soil water and solute content by depth increments were determined before and after simulations.All correlation coefficients between the applied simulation water and the amounts of Cl-,SO42-,NO3-and sum of anions in runoff water were positive and ranged between 0.922 and 0.999.The correlation coefficients for Ca2+,Mg2+,Na+,K+and sum of cations ranged between 0.783 and 0.983.We concluded from the data analysis that:(1)The amounts of ions in simulation water and in runoff water represent less than 1%of sum of the soil soluble content before rainfall simulation.(2)The CEC contained about 250%the sum of cation in saturated extract.(3)The very small amount of gypsum in the soil contained 50%the sum of saturated extract ions.This means that special attention should be paid to CEC and gypsum content in the management of such soils.Moreover,when modeling runoff and water quality from soils with these properties the modelers must include suitable subroutines considering gypsum and CEC of the soil for accurate prediction of runoff water quality.
