According to the historical changes of coastal lines, seven soil sampling districts, from land to sea, were arranged in Dongtai City, Jiangsu Province to sample soils from surface and profile. Concentrations of seven ...According to the historical changes of coastal lines, seven soil sampling districts, from land to sea, were arranged in Dongtai City, Jiangsu Province to sample soils from surface and profile. Concentrations of seven major heavy metals (HMs), granularity, pH, organic matters and C/N of the soil samples were analyzed. Results show that concentrations of heavy metals in agricultural land present a certain spatial variance, decreasing from land to sea. Pollution assessment indicates that the agricultural soils were not polluted by HMs, but the potential pollution of Cu and Hg needs to be alerted. Different HMs accumulate in the surface and sub-surface of the soil profiles, and concentrations of Hg and Pb decrease significantly with the increment of soil depth. Concentrations of HMs exhibit a significantly negative correlation to pH, but have no significant relation with organic matters in soil. Principle component analysis show that the concentrations of HMs relate to the land use history. Concentrations of Hg, Ni and Cr in soil are closely related with land use history, and concentrations of Pb, Cu and Cr are affected by land use history as well as other factors. However, there is no significant relation between concentration of As and land use history.展开更多
Intercropping is a very effective cultivation method in the agricultural production with a long history. The use of intercropping to build a niche complementary crop community can not only enhance the stability of far...Intercropping is a very effective cultivation method in the agricultural production with a long history. The use of intercropping to build a niche complementary crop community can not only enhance the stability of farmland ecosystem and the resistance of crop community to environmental stress but also reduce the damage of diseases, insect pests, environmental pollution and improve the efficiency of resource use to finally achieve high and stable yield of crop community. By collecting the intercropping researches at home and abroad, this thesis describes the impact of intercropping on crop nitrogen fixation and nitrogen transfer, accumulation and distribution of soil nitrate nitrogen, soil microorganism, crop diseases and insect pests, ventilation and light transmission, quality, yield and nutrient absorption, draws a conclusion on intercropping advantages and points out the sections requiring further study in the future.展开更多
This analysis studies changes in the variation 210Pbex inventory in soil in response to soil erosion on uncultivated land.A model was created to fit the response of 210 Pb ex inventory to variations in soil erosion ra...This analysis studies changes in the variation 210Pbex inventory in soil in response to soil erosion on uncultivated land.A model was created to fit the response of 210 Pb ex inventory to variations in soil erosion rates on uncultivated land using the principle of mass balance.By numerical simulation of the variation in the soil erosion rate in soil of uncultivated land,we prove:(1) past use of what has long been considered the best method of determining 210 Pb ex levels over the past 100 to 200 years is not scientifically accurate;(2) the model shows that variation in 210 Pb ex inventory as a function of time varies according to the index law after variation of soil erosion rates in uncultivated land is considered;and(3) the time needed for the variation in 210 Pb ex inventory to reach a steady-state is affected by changes in the rate of soil erosion and the quality and depth of relaxation in soil of uncultivated land.The results of this research can guide efforts to measure soil erosion rates.展开更多
基金Under the auspices of State Key Development Program for Basic Research of China (No 2002CB410810)
文摘According to the historical changes of coastal lines, seven soil sampling districts, from land to sea, were arranged in Dongtai City, Jiangsu Province to sample soils from surface and profile. Concentrations of seven major heavy metals (HMs), granularity, pH, organic matters and C/N of the soil samples were analyzed. Results show that concentrations of heavy metals in agricultural land present a certain spatial variance, decreasing from land to sea. Pollution assessment indicates that the agricultural soils were not polluted by HMs, but the potential pollution of Cu and Hg needs to be alerted. Different HMs accumulate in the surface and sub-surface of the soil profiles, and concentrations of Hg and Pb decrease significantly with the increment of soil depth. Concentrations of HMs exhibit a significantly negative correlation to pH, but have no significant relation with organic matters in soil. Principle component analysis show that the concentrations of HMs relate to the land use history. Concentrations of Hg, Ni and Cr in soil are closely related with land use history, and concentrations of Pb, Cu and Cr are affected by land use history as well as other factors. However, there is no significant relation between concentration of As and land use history.
基金Supported by National Natural Science Foundation (U1033004)
文摘Intercropping is a very effective cultivation method in the agricultural production with a long history. The use of intercropping to build a niche complementary crop community can not only enhance the stability of farmland ecosystem and the resistance of crop community to environmental stress but also reduce the damage of diseases, insect pests, environmental pollution and improve the efficiency of resource use to finally achieve high and stable yield of crop community. By collecting the intercropping researches at home and abroad, this thesis describes the impact of intercropping on crop nitrogen fixation and nitrogen transfer, accumulation and distribution of soil nitrate nitrogen, soil microorganism, crop diseases and insect pests, ventilation and light transmission, quality, yield and nutrient absorption, draws a conclusion on intercropping advantages and points out the sections requiring further study in the future.
基金supported by the National Natural Science Foundation of China (41030751,41173094 and 41103047)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘This analysis studies changes in the variation 210Pbex inventory in soil in response to soil erosion on uncultivated land.A model was created to fit the response of 210 Pb ex inventory to variations in soil erosion rates on uncultivated land using the principle of mass balance.By numerical simulation of the variation in the soil erosion rate in soil of uncultivated land,we prove:(1) past use of what has long been considered the best method of determining 210 Pb ex levels over the past 100 to 200 years is not scientifically accurate;(2) the model shows that variation in 210 Pb ex inventory as a function of time varies according to the index law after variation of soil erosion rates in uncultivated land is considered;and(3) the time needed for the variation in 210 Pb ex inventory to reach a steady-state is affected by changes in the rate of soil erosion and the quality and depth of relaxation in soil of uncultivated land.The results of this research can guide efforts to measure soil erosion rates.
