摘要
采用根垫法研究玉米根际土壤铜形态动态变化。结果表明 :玉米生长过程中根际土壤铜形态发生显著变化。植物生长前期交换态和碳酸盐结合态铜含量逐渐增加 ,随后增加量减少。植物生长后期根际交换态和碳酸盐结合态铜含量低于非根际土壤。这种变化主要由根际环境变化与植物吸收引起。与根际土壤中铜形态变化 ,特别是交换态铜含量变化关系密切的因素包括土壤溶解性有机碳、p H和土壤微生物。随着植物生物量的增加 ,对铜的吸收速率不断增加 。
Rhizobox was used to study the distribution of copper species in maize rhizosphere and transformation kinetics of copper speciation under controlled condition. Copper speciation was characterized using Tessier's procedure. Exchangeable, carbonate bound, Fe-Mn oxide bound, organic bound, and residuals in maize rhizosphere and control (as bulk soil) were extracted sequentially after various growth period from 20 to 100 days. pH, Eh, dissolved organic carbon, and microbial mass were detected at the same time. The copper accumulated in the maize was also measured for the plant grew for various days.;The results of the experiment revealed that transformation among copper species occurred during the growth period. The exchangeable copper in the rhizosphere increased at the beginning and reached its climax after 20 days or so, after which the exchangeable copper decreased gradually and hit its original lever around the 40th day. The trend of decrease continued for rest of time to a very low level. For the carbonate bound copper, the level of the species showed a very similar pattern of the transformation but much slower than that of the exchangeable copper. It did not reach the maximum value till about 40 days and dropped to the starting value at the 80th day or so.;As for Fe-Mn oxides, it also followed a similar pattern of the exchangeable and the carbonate bound copper and increased in the early period and decreased late. However, Fe-Mn oxides bound copper in the rhizosphere remained elevated in comparing to the bulk soil.;Organic bound copper, however, varied in an opposite direction. It decreased at the beginning and increased slightly during the later stage. ;If the change in fractionation after certain days were examined, the change in various species are similar to those reported in the literature. For instance, after 30 days of incubation, the exchangeable, the carbonate bound, and the Fe-Mn oxide bound copper increased to 0.21,0.48 and 1.57mg/kg, respectively. Significant differences in the exchangeable and the carbonate bound copper between the rhizosphere and the bulk soil were confirmed by the results of t-test at this time. By average, amount of the exchangeable, the carbonate bound, the Fe-Mn oxides bound, and the organic bound copper transformed in the rhizosphere were 0.4, 1.0, 1.4, and 2.4 mg/kg respectively, which approximately accounted for 50%, 10%, 6.0%, and 4.0% of the corresponding copper species in the rhizosphere. In other words, the intensity of copper species transformation in the rhizosphere decreased in following order, the exchangeable > the carbonate bound > the Fe-Mn oxides bound > the organic bound.Results of the measurement of other parameters including pH, Eh, DOC, and microbial mass indicate that rhizosphere pH steadily increased about 0.25 pH unit while Eh decreased about 60mV during the incubation. DOC in the rhizosphere remained higher than that in non-rhizosphere soil during the entire experimental period. DOC reached its climax, e.g. 29.2 mg/kg, after 15 days of incubation and decreased afterwards. After 100 days, the difference in DOC between the rhizosphere and the non-rhizosphere was only 2.5 mg/kg. Microbial mass in rhizosphere rapidly increased in the late period. The difference in the microbial mass carbon between the rhizosphere and the non-rhizosphere reached 220.6 mg/kg after 100 days. The results of correlation analysis suggested that variation in the exchangeable copper negatively correlated with the change in rhizosphere pH significantly. And there was a significantly positive correlation between the changes in the exchangeable copper and Eh. It is clear that the change in the exchangeable copper in the rhizosphere was markedly influenced by pH and Eh. On the other hand, the increase in DOC in the rhizosphere increased the level of the exchangeable copper. Since changes in both pH and DOC in the rhizosphere are at least partially the results of root exudation. It is believe that root exudates from the plant affected the transformation of copper species in the rhizosphere. T
出处
《生态学报》
CAS
CSCD
北大核心
2002年第10期1666-1671,共6页
Acta Ecologica Sinica
基金
国家自然科学基金资助 ( 4 0 0 31 0 1 0
4 0 0 2 4 1 0 1 )
