Climate change impacts on eutrophication in the Po River(Italy):Temperature-mediated reduction in nitrogen export but no effect on phosphorus  

作　　者：Elisa Soana Maria Pia Gervasio Tommaso Granata Daniela Colombo Giuseppe Castaldelli 

机构地区：[1]Department of Environmental and Prevention Sciences,University of Ferrara,Via Luigi Borsari 46,44121 Ferrara,Italy [2]CESI-Italian Electrical and Technical Experimental Center,via Rubattino 54,20134,Milano,Italy

出　　处：《Journal of Environmental Sciences》2024年第9期148-163,共16页环境科学学报（英文版）

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.

摘　　要：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.

关 键 词：Nutrient export EUTROPHICATION Climate change Water temperature DENITRIFICATION Po River 

分 类 号：P467[天文地球—大气科学及气象学] X52[环境科学与工程—环境工程]