Black water aggregation （BWA） in Taihu Lake is a disaster for the lake environment. It is a phenomenon resulting from water environmental deterioration and eutrophication caused by accumulation of pollutants in the ...Black water aggregation （BWA） in Taihu Lake is a disaster for the lake environment. It is a phenomenon resulting from water environmental deterioration and eutrophication caused by accumulation of pollutants in the lake, according to research on the water quality, pollutants of BWA, and occurrence mechanisms of BWA. Dead algae are the material base of BWA, the polluted sediment is an important factor for the formation of BWA, and hydrological and meteorological conditions such as sun light, air temperature, wind speed, and water flow are the other factors that may lead to the formation of BWA. Thioether substances such as dimethyl trisulfide are the representative pollutants of BWA. Parameters such as chlorophyll-a, DO, pH, and water temperature are sensitive indicators of BWA. Measures such as algae collection, ecological dredging, pollution control, and water diversion from the Yangtze River to the lake, are effective, and strengthening aeration is an emergency measure to control BWA.展开更多
In order to get a good indicator to evaluate the impacts of no tillage （NT） on soil structure and soil quality, we studied the dynamics of total soil organic carbon （SOC） and aggregate-associated SOC, and their re...In order to get a good indicator to evaluate the impacts of no tillage （NT） on soil structure and soil quality, we studied the dynamics of total soil organic carbon （SOC） and aggregate-associated SOC, and their relationships in the plow layer （30 cm） in black soil of Northeast China under NT practice. The tillage experiment was established in Dehui County, Jilin Province, China, in 2001. The total SOC and aggregate-associated SOC under 5-yr tillage treatments were measured. NT practices did not lead to the increase of average SOC content at 0-30 cm depth, but it did significantly increase SOC at the top soil （0-5 cm）. In NT plots, the change of SOC in 〉 1 000 μm aggregate was the same with that of total SOC, but the effect of NT on SOC in 〉 1 000 lain aggregate was greater than the effect on total SOC, suggesting that 〉 1 000 μm aggregate had more sensitive response to the impact of tillage practices. Also, significant positive correlation occurred between total SOC and SOC in 〉 1 000 μm aggregate in black soil. Consequently, in the short term soil macroaggregate 〉 1 000 μm could be used as an indicator to evaluate the impacts of tillage practices on soil structure in black soil of Northeast China.展开更多
Laboratory experiments were carried out to investigate the effect of freezing and thawing processes on wet aggregate stability （WAS） of black soil. Wet aggregate stability was determined by different aggregate size ...Laboratory experiments were carried out to investigate the effect of freezing and thawing processes on wet aggregate stability （WAS） of black soil. Wet aggregate stability was determined by different aggregate size groups, different water contents, various freeze-thaw cycles, and various freezing temperatures. The results showed that, when at suitable water content, aggregate stability was enhanced, aggregate sta-bility will be disrupted when moisture content is too high or too low, especially higher water content. Temperature also had a significant ef-fect, but moisture content determined the suitable freezing temperatures for a given soil. Water-stable aggregate （WSA〉0.5）, the total aggre-gate content, and mean weight diameter decreasing with the freeze-thaw cycles increase, reached to 5 percent significance level. The reason for crumbing aggregates is the water and air conflict, thus raising the hypothesis that water content affects the aggregate stability in the process of freezing and thawing.展开更多
基金supported by the National Water Project of China (Grant No. 2008ZX07101-011)
文摘Black water aggregation （BWA） in Taihu Lake is a disaster for the lake environment. It is a phenomenon resulting from water environmental deterioration and eutrophication caused by accumulation of pollutants in the lake, according to research on the water quality, pollutants of BWA, and occurrence mechanisms of BWA. Dead algae are the material base of BWA, the polluted sediment is an important factor for the formation of BWA, and hydrological and meteorological conditions such as sun light, air temperature, wind speed, and water flow are the other factors that may lead to the formation of BWA. Thioether substances such as dimethyl trisulfide are the representative pollutants of BWA. Parameters such as chlorophyll-a, DO, pH, and water temperature are sensitive indicators of BWA. Measures such as algae collection, ecological dredging, pollution control, and water diversion from the Yangtze River to the lake, are effective, and strengthening aeration is an emergency measure to control BWA.
基金supported by the National Natural Science Foundation of China (40801071)the Key Technologies R&D Program of China during the 11th Five-Year Plan period (2006BAD15B01)+1 种基金the Program for Advanced Science Field (KZCX3-SW-NA3-31)Doctoral Research Foundation in Northeast Institute of Geography and Agroecology,Chinese Academy of Sciences (O8H2041)
文摘In order to get a good indicator to evaluate the impacts of no tillage （NT） on soil structure and soil quality, we studied the dynamics of total soil organic carbon （SOC） and aggregate-associated SOC, and their relationships in the plow layer （30 cm） in black soil of Northeast China under NT practice. The tillage experiment was established in Dehui County, Jilin Province, China, in 2001. The total SOC and aggregate-associated SOC under 5-yr tillage treatments were measured. NT practices did not lead to the increase of average SOC content at 0-30 cm depth, but it did significantly increase SOC at the top soil （0-5 cm）. In NT plots, the change of SOC in 〉 1 000 μm aggregate was the same with that of total SOC, but the effect of NT on SOC in 〉 1 000 lain aggregate was greater than the effect on total SOC, suggesting that 〉 1 000 μm aggregate had more sensitive response to the impact of tillage practices. Also, significant positive correlation occurred between total SOC and SOC in 〉 1 000 μm aggregate in black soil. Consequently, in the short term soil macroaggregate 〉 1 000 μm could be used as an indicator to evaluate the impacts of tillage practices on soil structure in black soil of Northeast China.
基金National Basic Research Program of China (2005CB121101, 2005CB121103)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-407)
文摘Laboratory experiments were carried out to investigate the effect of freezing and thawing processes on wet aggregate stability （WAS） of black soil. Wet aggregate stability was determined by different aggregate size groups, different water contents, various freeze-thaw cycles, and various freezing temperatures. The results showed that, when at suitable water content, aggregate stability was enhanced, aggregate sta-bility will be disrupted when moisture content is too high or too low, especially higher water content. Temperature also had a significant ef-fect, but moisture content determined the suitable freezing temperatures for a given soil. Water-stable aggregate （WSA〉0.5）, the total aggre-gate content, and mean weight diameter decreasing with the freeze-thaw cycles increase, reached to 5 percent significance level. The reason for crumbing aggregates is the water and air conflict, thus raising the hypothesis that water content affects the aggregate stability in the process of freezing and thawing.
