Gross pollutants are the primary targeted pollutants in urban catchment management for urban water quality improvement as well as mitigation of flood. Apart from aesthetically unattractive because of its visibility, g...Gross pollutants are the primary targeted pollutants in urban catchment management for urban water quality improvement as well as mitigation of flood. Apart from aesthetically unattractive because of its visibility, gross pollutants also contributes to degradation of river water quality and loss of aquatic habitat as it carries harmful pollutants such as oxygen demanding material, hydrocarbons and heavy metals. This study analyzed trend of gross pollutant generated from two urban residential areas located in Selangor, Malaysia. The median value of gross pollutant load obtained fi＇om the Amanah Apartment and Bandar Botanic are 347.41 kg/ha/year and 32.46 kg/ha/year, respectively. Relationship between gross pollutant wet load with rainfall depths was derived using regression equation. A significant trend of increasing gross pollutant wet load into drainage system with increasing rainfall depth was observed. The behavior of pollutant load is related to the one observed in Australia.展开更多
Most studies on dissimilatory nitrate reduction to ammonium （DNRA） in paddy soils were conducted in the laboratory and in situ studies are in need for better understanding of the DNRA process. In this study, in situ...Most studies on dissimilatory nitrate reduction to ammonium （DNRA） in paddy soils were conducted in the laboratory and in situ studies are in need for better understanding of the DNRA process. In this study, in situ incubations of soil DNRA using ^15N tracer were carried out in paddy fields under conventional water （CW） and low water （LW） managements to explore the potential of soil DNRA after liquid cattle waste （LCW） application and to investigate the impacts of soil redox potential （Eh） and labile carbon on DNRA. DNRA rates ranged from 3.06 to 10.40 mg N kg 1 dry soil d-1, which accounted for 8.55%-12.36% and 3.88% 25.44% of consumption of added NO3-^15N when Eh at 5 cm soil depth ranged from 230 to 414 mV and -225 to -65 mV, respectively. DNRA rates showed no significant difference in paddy soils under two water managements although soil Eh and/or dissolved organic carbon （DOC） were more favorable for DNRA in the paddy soil under CW management 1 d before, or 5 and 7 d after LCW application. Soil DNRA rates were negatively correlated with soil Eh （P 〈 0.05, n = 5） but positively correlated with soil DOC （P 〈 0.05, n - 5） in the paddy soil under LW management, while no significant correlations were shown in the paddy soil under CW management. The potential of DNRA measured in situ was consistent with previous laboratory studies; and the controlling factors of DNRA in paddy soils might be different under different water managements, probably due to the presence of different microfioras of DNRA.展开更多
Reporting modeling results with uncertainty information can benefit decision making by decreasing the extent that variability exerts a disproportionate influence on the options selected. For making decisions with more...Reporting modeling results with uncertainty information can benefit decision making by decreasing the extent that variability exerts a disproportionate influence on the options selected. For making decisions with more confidence, the uncertainty interval should be as narrow as possible. Here, the soil organic carbon （SOC） dynamics of the major paddy soil subgroup from 4 different paddy field regions of China （located in 4 counties under different climate-soil-management combinations） were modeled using the DeNitrification- DeComposition （DNDC） model for the period from 1980 to 2008. Uncertainty intervals associated with the SOC dynamics for these 4 subgroups were estimated by a long-term global sensitivity and uncertainty analysis （i. e., the Sobolt method）, and their sensitivities to 7 influential factors were quantified using the total effect sensitivity index. The results, modeled with high confidence, indicated that in the past 29 years, the studied paddy soils in Xinxing, Yixing, and Zhongjiang counties were carbon （C） sinks, while the paddy soil in Helong County was a C source. The 3 C sinks sequestered 12.2 （5.4, 19.6）, 17.1 （8.9, 25.0）, and 16.9 （-1.2, 33.6） t C ha-1 （values in the parentheses are the 5th and 95th percentiles, respectively）. Conversely, the C source had a loss of -5.4 （-14.2, 0.06） t C ha-1 in the past 29 years. The 7 factors, which changed with the climate-soil-management context, exhibited variable influences on modeled SOC. Measures with potential to conserve or sequestrate more C into paddy soils, such as incorporating more crop residues into soils and reducing chemical fertilizer application rates, were recommended for specific soils based on the sensitivity analysis results.展开更多
文摘Gross pollutants are the primary targeted pollutants in urban catchment management for urban water quality improvement as well as mitigation of flood. Apart from aesthetically unattractive because of its visibility, gross pollutants also contributes to degradation of river water quality and loss of aquatic habitat as it carries harmful pollutants such as oxygen demanding material, hydrocarbons and heavy metals. This study analyzed trend of gross pollutant generated from two urban residential areas located in Selangor, Malaysia. The median value of gross pollutant load obtained fi＇om the Amanah Apartment and Bandar Botanic are 347.41 kg/ha/year and 32.46 kg/ha/year, respectively. Relationship between gross pollutant wet load with rainfall depths was derived using regression equation. A significant trend of increasing gross pollutant wet load into drainage system with increasing rainfall depth was observed. The behavior of pollutant load is related to the one observed in Australia.
基金Supported by the National Natural Science Foundation of China (No. 30821140542)the Japan Science and Technology Agency (No. 09000075)
文摘Most studies on dissimilatory nitrate reduction to ammonium （DNRA） in paddy soils were conducted in the laboratory and in situ studies are in need for better understanding of the DNRA process. In this study, in situ incubations of soil DNRA using ^15N tracer were carried out in paddy fields under conventional water （CW） and low water （LW） managements to explore the potential of soil DNRA after liquid cattle waste （LCW） application and to investigate the impacts of soil redox potential （Eh） and labile carbon on DNRA. DNRA rates ranged from 3.06 to 10.40 mg N kg 1 dry soil d-1, which accounted for 8.55%-12.36% and 3.88% 25.44% of consumption of added NO3-^15N when Eh at 5 cm soil depth ranged from 230 to 414 mV and -225 to -65 mV, respectively. DNRA rates showed no significant difference in paddy soils under two water managements although soil Eh and/or dissolved organic carbon （DOC） were more favorable for DNRA in the paddy soil under CW management 1 d before, or 5 and 7 d after LCW application. Soil DNRA rates were negatively correlated with soil Eh （P 〈 0.05, n = 5） but positively correlated with soil DOC （P 〈 0.05, n - 5） in the paddy soil under LW management, while no significant correlations were shown in the paddy soil under CW management. The potential of DNRA measured in situ was consistent with previous laboratory studies; and the controlling factors of DNRA in paddy soils might be different under different water managements, probably due to the presence of different microfioras of DNRA.
基金supported by the National Natural Science Foundation of China (No.41471177)the Knowledge Innovation Program of Chinese Academy of Sciences (No.KZCX2-EW-QN404)the Strategic Priority Research Program of Chinese Academy of Sciences (No.XDA05050509)
文摘Reporting modeling results with uncertainty information can benefit decision making by decreasing the extent that variability exerts a disproportionate influence on the options selected. For making decisions with more confidence, the uncertainty interval should be as narrow as possible. Here, the soil organic carbon （SOC） dynamics of the major paddy soil subgroup from 4 different paddy field regions of China （located in 4 counties under different climate-soil-management combinations） were modeled using the DeNitrification- DeComposition （DNDC） model for the period from 1980 to 2008. Uncertainty intervals associated with the SOC dynamics for these 4 subgroups were estimated by a long-term global sensitivity and uncertainty analysis （i. e., the Sobolt method）, and their sensitivities to 7 influential factors were quantified using the total effect sensitivity index. The results, modeled with high confidence, indicated that in the past 29 years, the studied paddy soils in Xinxing, Yixing, and Zhongjiang counties were carbon （C） sinks, while the paddy soil in Helong County was a C source. The 3 C sinks sequestered 12.2 （5.4, 19.6）, 17.1 （8.9, 25.0）, and 16.9 （-1.2, 33.6） t C ha-1 （values in the parentheses are the 5th and 95th percentiles, respectively）. Conversely, the C source had a loss of -5.4 （-14.2, 0.06） t C ha-1 in the past 29 years. The 7 factors, which changed with the climate-soil-management context, exhibited variable influences on modeled SOC. Measures with potential to conserve or sequestrate more C into paddy soils, such as incorporating more crop residues into soils and reducing chemical fertilizer application rates, were recommended for specific soils based on the sensitivity analysis results.
