Rivers worldwide are under stress from eutrophication and nitrate pollution,but the ecological consequences overlap with climate change,and the resulting interactions may be unexpected and still unexplored.The Po Rive...Rivers worldwide are under stress from eutrophication and nitrate pollution,but the ecological consequences overlap with climate change,and the resulting interactions may be unexpected and still unexplored.The Po River basin(northern Italy)is one of the most agriculturally productive and densely populated areas in Europe.It remains unclear whether the climate change impacts on the thermal and hydrological regimes are already affecting nutrient dynamics and transport to coastal areas.The present work addresses the long-term trends(1992-2020)of nitrogen and phosphorus export by investigating both the annual magnitude and the seasonal patterns and their relationship with water temperature and discharge trajectories.Despite the constant diffuse and point sources in the basin,a marked decrease(-20%)in nitrogen export,mostly as nitrate,was recorded in the last decade compared to the 1990 s,while no significant downward trend was observed for phosphorus.The water temperature of the Po River has warmed,with the most pronounced signals in summer(+0.13℃/year)and autumn(+0.16℃/year),together with the strongest increase in the number of warm days(+70%-80%).An extended seasonal window of warm temperatures and the persistence of low flow periods are likely to create favorable conditions for permanent nitrate removal via denitrification,resulting in a lower delivery of reactive nitrogen to the sea.The present results show that climate change-driven warming may enhance nitrogen processing by increasing respiratory river metabolism,thereby reducing export from spring to early autumn,when the risk of eutrophication in coastal zones is higher.展开更多
Background:Grazing by livestock and cultivation have been considered as two important causes of soil erosion and nutrient export.However,there has been limited evidence that grazing or cultivation matters to soil eros...Background:Grazing by livestock and cultivation have been considered as two important causes of soil erosion and nutrient export.However,there has been limited evidence that grazing or cultivation matters to soil erosion and nutrient export in Ethiopia.Hence,this study was conducted in the Galesa watershed in Ethiopia to examine the effects of grazing and cultivation on runoff,soil loss,and nutrient export.Daily values of runoff,soil erosion,and nutrient outflow were measured for three consecutive years following standard procedures.Independent t test was performed to check if the means of runoff,soil loss,and nutrient loss from grazing and cultivated lands were significantly different.Moreover,repeated analysis of variance(ANOVA)was used to test if mean values of runoff,soil loss,and nutrient export varied significantly over the study years.Results:Although the average annual runoff depth was 7.8%higher in grazing land(GL),soil erosion was significantly lower(39%)in GL as compared to cultivated land(CL).Similarly,sediment and runoff-associated annual losses of total nitrogen(N),available phosphorus(P),exchangeable potassium(K),and organic carbon(OC)were low in the GL treatments.Lowest losses of total N(9.30 kg ha^(−1) year^(−1)),available P(0.83 kg ha^(−1) year^(−1)),and exchangeable K(1.84 kg ha^(−1) year^(−1))were recorded in GL treatment.Likewise,lowest losses of sediment-associated total N(32.8 kg ha^(−1) year^(−1)),available P(0.39 kg ha^(−1) year^(−1)),exchangeable K(0.23 kg ha^(−1) year^(−1)),and soil organic carbon(630 kg ha^(−1) year^(−1))were recorded from GL over the 3 years of experimentation.Conclusion:Our results indicate that cultivation increased soil erosion as compared to grazing.Although there were significant reductions in soil erosion and nutrient export from grazing lands compared with cultivated lands,the absolute losses were still high.This implies the need for grazing land management using appropriate physical and biological erosion control measures to increase productivity and reduce soil erosion as well as nutrient export.展开更多
In this paper,the effects of rainfall on nutrient import and export in the broad-leaved evergreen forest in southwest Yunnan Province have been observed. The results show that in the process of rainfall the nutrient i...In this paper,the effects of rainfall on nutrient import and export in the broad-leaved evergreen forest in southwest Yunnan Province have been observed. The results show that in the process of rainfall the nutrient import in rainfall is mainly N and the major elements of nutrient import in throughrain are P, K and Mg. They occupy 69. 85%,77.33%,98.19%,and 80. 40% of the total nutrient import respectively. Ca occupies about half of the total nutrient import in rainfall and throughrain and the percentages are 45.35% and 54.38% respectively. The major form of nutrient export is soil percolation.N,P, K,Ca and Mg occupy 96.52%,86.79%, 69.13%, 98.17% and 97.21 % of the total nutrient export respectively.In nutrient cycle,N,P,K and Ca increase 25. 94 kg/(ha.a),0. 353 kg/(ha.a),3. 83 kg/(ha.a),1. 26 kg/(ha.a) respectively,but Mg reduces 0. 654 kg/(ha. a).展开更多
各种土地利用类型营养盐输出系数是建立非点源污染模型的重要参数。以位于太湖地区的西苕溪流域为研究区,利用G IS技术进行子流域划分并选择了11个典型小流域,通过对2004年Spot遥感影像解译获得流域土地利用数据,于2004年分3次监测了各...各种土地利用类型营养盐输出系数是建立非点源污染模型的重要参数。以位于太湖地区的西苕溪流域为研究区,利用G IS技术进行子流域划分并选择了11个典型小流域,通过对2004年Spot遥感影像解译获得流域土地利用数据,于2004年分3次监测了各个小流域出口的TN、TP浓度。基于以上数据,定性分析了小流域土地利用结构与营养盐输出关系,表明随着耕地面积比例增大或林地面积比例减小,营养盐输出水平增大;在此分析基础上,建立了小流域不同土地利用类型(耕地、林地)面积比例与TN、TP浓度的定量关系,并进而计算获得西苕溪流域耕地的TN、TP输出系数分别为4.747 3 m g/L,0.089 6 m g/L,林地的TN、TP输出系数分别为0.271 3m g/L,0.007 5 m g/L,为流域尺度的营养盐输出负荷估算提供重要参数。展开更多
基金supported by the Consorzio di Bonifica Pianura di Ferrara(Ferrara Land Reclamation Consortium)as part of a collaboration aimed at defining management strategies to control eutrophication in the Po Delta.
文摘Rivers worldwide are under stress from eutrophication and nitrate pollution,but the ecological consequences overlap with climate change,and the resulting interactions may be unexpected and still unexplored.The Po River basin(northern Italy)is one of the most agriculturally productive and densely populated areas in Europe.It remains unclear whether the climate change impacts on the thermal and hydrological regimes are already affecting nutrient dynamics and transport to coastal areas.The present work addresses the long-term trends(1992-2020)of nitrogen and phosphorus export by investigating both the annual magnitude and the seasonal patterns and their relationship with water temperature and discharge trajectories.Despite the constant diffuse and point sources in the basin,a marked decrease(-20%)in nitrogen export,mostly as nitrate,was recorded in the last decade compared to the 1990 s,while no significant downward trend was observed for phosphorus.The water temperature of the Po River has warmed,with the most pronounced signals in summer(+0.13℃/year)and autumn(+0.16℃/year),together with the strongest increase in the number of warm days(+70%-80%).An extended seasonal window of warm temperatures and the persistence of low flow periods are likely to create favorable conditions for permanent nitrate removal via denitrification,resulting in a lower delivery of reactive nitrogen to the sea.The present results show that climate change-driven warming may enhance nitrogen processing by increasing respiratory river metabolism,thereby reducing export from spring to early autumn,when the risk of eutrophication in coastal zones is higher.
文摘Background:Grazing by livestock and cultivation have been considered as two important causes of soil erosion and nutrient export.However,there has been limited evidence that grazing or cultivation matters to soil erosion and nutrient export in Ethiopia.Hence,this study was conducted in the Galesa watershed in Ethiopia to examine the effects of grazing and cultivation on runoff,soil loss,and nutrient export.Daily values of runoff,soil erosion,and nutrient outflow were measured for three consecutive years following standard procedures.Independent t test was performed to check if the means of runoff,soil loss,and nutrient loss from grazing and cultivated lands were significantly different.Moreover,repeated analysis of variance(ANOVA)was used to test if mean values of runoff,soil loss,and nutrient export varied significantly over the study years.Results:Although the average annual runoff depth was 7.8%higher in grazing land(GL),soil erosion was significantly lower(39%)in GL as compared to cultivated land(CL).Similarly,sediment and runoff-associated annual losses of total nitrogen(N),available phosphorus(P),exchangeable potassium(K),and organic carbon(OC)were low in the GL treatments.Lowest losses of total N(9.30 kg ha^(−1) year^(−1)),available P(0.83 kg ha^(−1) year^(−1)),and exchangeable K(1.84 kg ha^(−1) year^(−1))were recorded in GL treatment.Likewise,lowest losses of sediment-associated total N(32.8 kg ha^(−1) year^(−1)),available P(0.39 kg ha^(−1) year^(−1)),exchangeable K(0.23 kg ha^(−1) year^(−1)),and soil organic carbon(630 kg ha^(−1) year^(−1))were recorded from GL over the 3 years of experimentation.Conclusion:Our results indicate that cultivation increased soil erosion as compared to grazing.Although there were significant reductions in soil erosion and nutrient export from grazing lands compared with cultivated lands,the absolute losses were still high.This implies the need for grazing land management using appropriate physical and biological erosion control measures to increase productivity and reduce soil erosion as well as nutrient export.
文摘In this paper,the effects of rainfall on nutrient import and export in the broad-leaved evergreen forest in southwest Yunnan Province have been observed. The results show that in the process of rainfall the nutrient import in rainfall is mainly N and the major elements of nutrient import in throughrain are P, K and Mg. They occupy 69. 85%,77.33%,98.19%,and 80. 40% of the total nutrient import respectively. Ca occupies about half of the total nutrient import in rainfall and throughrain and the percentages are 45.35% and 54.38% respectively. The major form of nutrient export is soil percolation.N,P, K,Ca and Mg occupy 96.52%,86.79%, 69.13%, 98.17% and 97.21 % of the total nutrient export respectively.In nutrient cycle,N,P,K and Ca increase 25. 94 kg/(ha.a),0. 353 kg/(ha.a),3. 83 kg/(ha.a),1. 26 kg/(ha.a) respectively,but Mg reduces 0. 654 kg/(ha. a).
文摘各种土地利用类型营养盐输出系数是建立非点源污染模型的重要参数。以位于太湖地区的西苕溪流域为研究区,利用G IS技术进行子流域划分并选择了11个典型小流域,通过对2004年Spot遥感影像解译获得流域土地利用数据,于2004年分3次监测了各个小流域出口的TN、TP浓度。基于以上数据,定性分析了小流域土地利用结构与营养盐输出关系,表明随着耕地面积比例增大或林地面积比例减小,营养盐输出水平增大;在此分析基础上,建立了小流域不同土地利用类型(耕地、林地)面积比例与TN、TP浓度的定量关系,并进而计算获得西苕溪流域耕地的TN、TP输出系数分别为4.747 3 m g/L,0.089 6 m g/L,林地的TN、TP输出系数分别为0.271 3m g/L,0.007 5 m g/L,为流域尺度的营养盐输出负荷估算提供重要参数。
