Developing realistic soil carbon （C） sequestration strategies for China＇s sustainable agriculture relies on accurate estimates of the amount, retention and turnover rates of C stored in paddy soils. Available C est...Developing realistic soil carbon （C） sequestration strategies for China＇s sustainable agriculture relies on accurate estimates of the amount, retention and turnover rates of C stored in paddy soils. Available C estimates to date are predominantly for the tilled and flood-irrigated surface topsoil （ca. 30 cm）. Such estimates cannot be used to extrapolate to soil depths of 100 cm since soil organic carbon （SOC） generally shows a sharp decrease with depth. In this research, composite soil samples were collected at several depths to 100 cm from three representative paddy soils in the Taihu Lake region, China. Soil organic carbon distribution in the profiles and in aggregate-size fractions was determined. Results showed that while SOC decreased exponentially with depth to 100 cm, a substantial proportion of the total SOC （30%-40%） is stored below the 30 cm depth. In the carbon-enriched paddy topsoils, SOC was found to accumulate preferentially in the 2-0.25 and 0.25-0.02 mm aggregate size fractions. δ^13C analysis of the coarse micro-aggregate fraction showed that the high degree of C stratification in the paddy topsoil was in agreement with the occurrence of lighter δ^1313C in the upper 30 cm depth. These results suggest that SOC stratification within profiles varies with different pedogenetical types of paddy soils with regards to clay and iron oxyhydrates distributions. Sand-sized fractions of aggregates in paddy soil systems may play a very important role in carbon sequestration and turnover, dissimilar to other studied agricultural systems.展开更多
为了尽可能量化不同土壤结构下变电站接地网安全性能的差异大小,基于所得土壤电阻率测量试验数据,对比分析了山地、沿海、丘陵3类地区垂直分层土壤结构和水平分层土壤结构下的变电站接地网接触电压和跨步电压等安全指标,并以两者间的偏...为了尽可能量化不同土壤结构下变电站接地网安全性能的差异大小,基于所得土壤电阻率测量试验数据,对比分析了山地、沿海、丘陵3类地区垂直分层土壤结构和水平分层土壤结构下的变电站接地网接触电压和跨步电压等安全指标,并以两者间的偏差百分比来衡量不同土壤结构与不同地区间差异。结果表明:使用现有的电流分布、电磁场、接地和土壤结构分布(current distribution,electromagnetic field and soil analysis,CDEGS)软件可以比较准确地计算出土壤水平分层和垂直分层结构;各地区两种土壤分层结构下的接触电压和跨步电压的对比说明了考虑土壤垂直分层的必要性;在同一地区垂直分层结构下,靠近土壤分界面部分的接触电压和跨步电压偏差百分比较高;最大值偏差百分比的计算结果说明,土壤电阻率越大,这种不同土壤分层结构所带来的差异越明显。展开更多
[Objective] This study aimed to investigate the effects of biogas slurry irri- gation on heavy metal contents in soils. [Method] A pot experiment was carried out to investigate the effects of biogas slurry irrigation ...[Objective] This study aimed to investigate the effects of biogas slurry irri- gation on heavy metal contents in soils. [Method] A pot experiment was carried out to investigate the effects of biogas slurry irrigation on the accumulation of heavy metals in soils by measuring the contents of Cu, Zn, Pb, Cr and Cd in different soil layers. [Result] The results showed that original and 30-fold biogas slurry increased the contents of Cu, Zn, Pb, Cd and Cr in soils; Cr might partially reach an exces- sive level in a short term. Biogas slurry irrigation increased the downward migration velocity of Cu and reduced the downward migration velocity of Zn in soils. [Conclu- sion] Biogas slurry irrigation influences the contents of heavy metals, and long-term application of biogas slurry will lead to the accumulation of heavy metals in soils.展开更多
文摘Developing realistic soil carbon （C） sequestration strategies for China＇s sustainable agriculture relies on accurate estimates of the amount, retention and turnover rates of C stored in paddy soils. Available C estimates to date are predominantly for the tilled and flood-irrigated surface topsoil （ca. 30 cm）. Such estimates cannot be used to extrapolate to soil depths of 100 cm since soil organic carbon （SOC） generally shows a sharp decrease with depth. In this research, composite soil samples were collected at several depths to 100 cm from three representative paddy soils in the Taihu Lake region, China. Soil organic carbon distribution in the profiles and in aggregate-size fractions was determined. Results showed that while SOC decreased exponentially with depth to 100 cm, a substantial proportion of the total SOC （30%-40%） is stored below the 30 cm depth. In the carbon-enriched paddy topsoils, SOC was found to accumulate preferentially in the 2-0.25 and 0.25-0.02 mm aggregate size fractions. δ^13C analysis of the coarse micro-aggregate fraction showed that the high degree of C stratification in the paddy topsoil was in agreement with the occurrence of lighter δ^1313C in the upper 30 cm depth. These results suggest that SOC stratification within profiles varies with different pedogenetical types of paddy soils with regards to clay and iron oxyhydrates distributions. Sand-sized fractions of aggregates in paddy soil systems may play a very important role in carbon sequestration and turnover, dissimilar to other studied agricultural systems.
文摘为了尽可能量化不同土壤结构下变电站接地网安全性能的差异大小,基于所得土壤电阻率测量试验数据,对比分析了山地、沿海、丘陵3类地区垂直分层土壤结构和水平分层土壤结构下的变电站接地网接触电压和跨步电压等安全指标,并以两者间的偏差百分比来衡量不同土壤结构与不同地区间差异。结果表明:使用现有的电流分布、电磁场、接地和土壤结构分布(current distribution,electromagnetic field and soil analysis,CDEGS)软件可以比较准确地计算出土壤水平分层和垂直分层结构;各地区两种土壤分层结构下的接触电压和跨步电压的对比说明了考虑土壤垂直分层的必要性;在同一地区垂直分层结构下,靠近土壤分界面部分的接触电压和跨步电压偏差百分比较高;最大值偏差百分比的计算结果说明,土壤电阻率越大,这种不同土壤分层结构所带来的差异越明显。
基金Supported by Technology Benefitting-the-People Project(S2013GMD100042)~~
文摘[Objective] This study aimed to investigate the effects of biogas slurry irri- gation on heavy metal contents in soils. [Method] A pot experiment was carried out to investigate the effects of biogas slurry irrigation on the accumulation of heavy metals in soils by measuring the contents of Cu, Zn, Pb, Cr and Cd in different soil layers. [Result] The results showed that original and 30-fold biogas slurry increased the contents of Cu, Zn, Pb, Cd and Cr in soils; Cr might partially reach an exces- sive level in a short term. Biogas slurry irrigation increased the downward migration velocity of Cu and reduced the downward migration velocity of Zn in soils. [Conclu- sion] Biogas slurry irrigation influences the contents of heavy metals, and long-term application of biogas slurry will lead to the accumulation of heavy metals in soils.
