In Ghana, inland valleys have been found to be suitable for rice cultivation and could potentially increase lowland paddy rice production, This study estimated the temporal variations of surface water resources and th...In Ghana, inland valleys have been found to be suitable for rice cultivation and could potentially increase lowland paddy rice production, This study estimated the temporal variations of surface water resources and their spatial distribution in the Mankran watershed of Ghana through the collection of recorded hydrological data in the bench mark watershedfrom2008 to 2010. Since most inland valley rice cultivation highly depends on rainfall, the watershed precipitation data over a decadal period showed sufficient wet years with a potential to sustain a high cultivation of paddy rice. Peak wetness occurred in June and October over a bi-modal precipitation pattern. Rating curve data for the Mankran-kesse river-upstream depicted low discharge values despite having a higher stream order. Thus stream order alone was not sufficient to estimate water resources potential. It was presumed that the geomorphology and lithology of the highly porous river bed and the presence of high sub-surface water resources stored in this zone may be implicated for this observation. Provision of water storage options for zones like Kesse-upstream seems a feasible option in order to cater for supplementary irrigation while indirectly tapping on subsurface water resources stored in the porous aquifers through basin interflows. Base flow data also showed that the discharge from upstream locations to the downstream exit of the watershed was high through direct surface river discharge and subsurface interflow. The temporal patterns of the hydrology indicate that annual paddy rice cultivation is ideal between May and October.展开更多
Twenty-one typical coupled large samples were chosen from areas within and surrounding nature reserves on the Tibetan Plateau using the large sample comparison method(LSCM).To evaluate the effectiveness of the nature ...Twenty-one typical coupled large samples were chosen from areas within and surrounding nature reserves on the Tibetan Plateau using the large sample comparison method(LSCM).To evaluate the effectiveness of the nature reserves in protecting the ecological environment,the alpine grassland net primary production(NPP) of these coupled samples were compared and the differences between them before and after their establishment as protected areas were analyzed.The results showed that:(1) With respect to the alpine grassland NPP,the ecological and environmental conditions of most nature reserves were more fragile than those of the surrounding areas and also lower than the average values for the Tibetan Plateau.(2) Of the 11 typical nature reserves selected,the positive trend in the NPP for Manzetang was the most significant,whereas there was no obvious trend in Taxkorgan.With the exception of Selincuo,the annual NPP growth rate in the nature reserves covered by alpine meadow and wetland was higher than that in nature reserves consisting of alpine steppe and alpine desert.(3) There were notable findings in 21 typical coupled samples:(a) After the establishment of the nature reserves,the annual rate of increase in the NPP in 76% of samples inside nature reserves and 82% of samples inside national nature reserves was higher than that of the corresponding samples outside nature reserves.(b) The effectiveness of ecological protection of the Mid-Kunlun,Changshagongma,Zoige and Selincuo(Selin Co) nature reserves was significant; the effectiveness of protection was relatively sig-nificant in most parts of the Sanjiangyuan and Qiangtang nature reserves,whereas in south-east Manzetang and north Taxkorgan the protection effectiveness was not obvious.(c) The ecological protection effectiveness was significant in nature reserves consisting of alpine meadow,but was weak in nature reserves covered by alpine steppe.This study also shows that the advantage of large sample comparison method in evaluating regional ecology change.Careful design of the samples used,to ensure comparability between the samples,is crucial to the success of this LSCM.展开更多
Dissolved organic matter(DOM) is a group of compounds that have complex chemical structures and multiple interactions with their surrounding materials. More than one trillion tons of DOM are stocked in the world's...Dissolved organic matter(DOM) is a group of compounds that have complex chemical structures and multiple interactions with their surrounding materials. More than one trillion tons of DOM are stocked in the world's aquatic ecosystems. DOM is a very important part of aquatic ecosystem productivity and plays a crucial role in global carbon cycling. DOM has rich environmental behaviors and effects such as influencing the bioavailability of contaminants, serving as an important inducer of reactive oxygen species(ROS), and protecting aquatic organisms from the harm of dangerous ultraviolet radiation. There have been many systematic studies on the composition, structure, and sources of DOM because such studies are much easier to conduct than studies on the environmental behaviors and effects of DOM. Due to many factors, the research systems of DOM's environmental behaviors and effects are still being developed and have become a hotspot of environmental science. This review paper focuses on some critical progress, problems, and trends of DOM's environmental behaviors and effects in aquatic ecosystems, including mutual exchange mechanisms between DOM and particulate organic matter(POM) with influencing factors, photochemical behaviors of DOM especially inducing ROS, binding interactions between DOM and anthropogenic organic contaminants(AOC), interactions between DOM and microorganisms, effects of DOM on pollutants' bioavailability, ecotoxicity, and ecological risks. Hopefully, this paper will contribute to a more systematic understanding of the DOM environmental behaviors and effects and to promoting further relevant studies.展开更多
The sustainable development of our future represents an unorthodox challenge in sciences and technologies.The exploration of unconventional chemical reactivities that could potentially result in more sustainable chemi...The sustainable development of our future represents an unorthodox challenge in sciences and technologies.The exploration of unconventional chemical reactivities that could potentially result in more sustainable chemical productions with efficient utilization of resource and inherent prevention of waste will provide the foundation for the synthetic chemistry of our future.As part of this endeavor,we have explored metal-mediated reactions in water to minimize protection-deprotection and the use of organic solvents,catalytic nucleophilic additions via C-H reactions to avoid generation and use of stoichiometric organic halides and metal in water,and Cross-Dehydrogenative-Coupling(CDC) reactions to minimize overall transformation steps.展开更多
文摘In Ghana, inland valleys have been found to be suitable for rice cultivation and could potentially increase lowland paddy rice production, This study estimated the temporal variations of surface water resources and their spatial distribution in the Mankran watershed of Ghana through the collection of recorded hydrological data in the bench mark watershedfrom2008 to 2010. Since most inland valley rice cultivation highly depends on rainfall, the watershed precipitation data over a decadal period showed sufficient wet years with a potential to sustain a high cultivation of paddy rice. Peak wetness occurred in June and October over a bi-modal precipitation pattern. Rating curve data for the Mankran-kesse river-upstream depicted low discharge values despite having a higher stream order. Thus stream order alone was not sufficient to estimate water resources potential. It was presumed that the geomorphology and lithology of the highly porous river bed and the presence of high sub-surface water resources stored in this zone may be implicated for this observation. Provision of water storage options for zones like Kesse-upstream seems a feasible option in order to cater for supplementary irrigation while indirectly tapping on subsurface water resources stored in the porous aquifers through basin interflows. Base flow data also showed that the discharge from upstream locations to the downstream exit of the watershed was high through direct surface river discharge and subsurface interflow. The temporal patterns of the hydrology indicate that annual paddy rice cultivation is ideal between May and October.
基金The Strategic Priority Research Program of the Chinese Academy of Sciences,No.XDB03030500National Key Technology Research and Development Program,No.2013BAC04B02+1 种基金Key Foundation Project of Basic Work of the Ministry of Science and Technology of China,No.2012FY111400National Natural Science Foundation of China,No.41171080,No.41201095
文摘Twenty-one typical coupled large samples were chosen from areas within and surrounding nature reserves on the Tibetan Plateau using the large sample comparison method(LSCM).To evaluate the effectiveness of the nature reserves in protecting the ecological environment,the alpine grassland net primary production(NPP) of these coupled samples were compared and the differences between them before and after their establishment as protected areas were analyzed.The results showed that:(1) With respect to the alpine grassland NPP,the ecological and environmental conditions of most nature reserves were more fragile than those of the surrounding areas and also lower than the average values for the Tibetan Plateau.(2) Of the 11 typical nature reserves selected,the positive trend in the NPP for Manzetang was the most significant,whereas there was no obvious trend in Taxkorgan.With the exception of Selincuo,the annual NPP growth rate in the nature reserves covered by alpine meadow and wetland was higher than that in nature reserves consisting of alpine steppe and alpine desert.(3) There were notable findings in 21 typical coupled samples:(a) After the establishment of the nature reserves,the annual rate of increase in the NPP in 76% of samples inside nature reserves and 82% of samples inside national nature reserves was higher than that of the corresponding samples outside nature reserves.(b) The effectiveness of ecological protection of the Mid-Kunlun,Changshagongma,Zoige and Selincuo(Selin Co) nature reserves was significant; the effectiveness of protection was relatively sig-nificant in most parts of the Sanjiangyuan and Qiangtang nature reserves,whereas in south-east Manzetang and north Taxkorgan the protection effectiveness was not obvious.(c) The ecological protection effectiveness was significant in nature reserves consisting of alpine meadow,but was weak in nature reserves covered by alpine steppe.This study also shows that the advantage of large sample comparison method in evaluating regional ecology change.Careful design of the samples used,to ensure comparability between the samples,is crucial to the success of this LSCM.
基金supported by the National Project for Water Pollution Control in China(Grant No.2012ZX07103-002)the National Natural Science Foundation of China(Grant Nos.4150308341271462&41030529)
文摘Dissolved organic matter(DOM) is a group of compounds that have complex chemical structures and multiple interactions with their surrounding materials. More than one trillion tons of DOM are stocked in the world's aquatic ecosystems. DOM is a very important part of aquatic ecosystem productivity and plays a crucial role in global carbon cycling. DOM has rich environmental behaviors and effects such as influencing the bioavailability of contaminants, serving as an important inducer of reactive oxygen species(ROS), and protecting aquatic organisms from the harm of dangerous ultraviolet radiation. There have been many systematic studies on the composition, structure, and sources of DOM because such studies are much easier to conduct than studies on the environmental behaviors and effects of DOM. Due to many factors, the research systems of DOM's environmental behaviors and effects are still being developed and have become a hotspot of environmental science. This review paper focuses on some critical progress, problems, and trends of DOM's environmental behaviors and effects in aquatic ecosystems, including mutual exchange mechanisms between DOM and particulate organic matter(POM) with influencing factors, photochemical behaviors of DOM especially inducing ROS, binding interactions between DOM and anthropogenic organic contaminants(AOC), interactions between DOM and microorganisms, effects of DOM on pollutants' bioavailability, ecotoxicity, and ecological risks. Hopefully, this paper will contribute to a more systematic understanding of the DOM environmental behaviors and effects and to promoting further relevant studies.
基金the Canada Research Chair (Tier I) foundationthe E. B. Eddy Endowment Fund+1 种基金the CFI, NSERC, FQRNTthe NSF and the NSF-EPA Joint Program for a Sustainable Environment for partial support of our research over the years
文摘The sustainable development of our future represents an unorthodox challenge in sciences and technologies.The exploration of unconventional chemical reactivities that could potentially result in more sustainable chemical productions with efficient utilization of resource and inherent prevention of waste will provide the foundation for the synthetic chemistry of our future.As part of this endeavor,we have explored metal-mediated reactions in water to minimize protection-deprotection and the use of organic solvents,catalytic nucleophilic additions via C-H reactions to avoid generation and use of stoichiometric organic halides and metal in water,and Cross-Dehydrogenative-Coupling(CDC) reactions to minimize overall transformation steps.
