气候与社会经济变化下抚河流域氮磷负荷变化

Evolution of nitrogen and phosphorus load in Fuhe River Basin under climate and socio-economic changes

目前对氮磷预估的研究主要是基于气候变化和社会经济不变的假定,缺少考虑社会经济动态变化对氮磷负荷的影响。为研究气候和社会经济共同作用下氮磷负荷的变化,选取第六次耦合模式比较计划(CMIP6)中情景完善的5个气候模式中的7个气候情景SSPs(SSP1-1.9、SSP1-2.6、SSP2-4.5、SSP3-7.0、SSP4-3.4、SSP4-6.0、SSP5-8.5),采用SWAT水文模型模拟分析了气候变化和社会经济变化共同作用下抚河流域2021~2050年氮磷负荷相对基准期(1995~2014年)的时空变化特征。研究结果表明:①社会经济变化是氮磷负荷变化的主要影响因素,但1981~2020年气候对总氮负荷变化的贡献率从14.4%上升到18.2%,对总磷负荷变化的贡献率从13.5%上升到17.8%,表明气候变化对总氮总磷负荷的影响在增加,社会经济变化对总氮总磷负荷的影响减小。②抚河流域多年平均总氮负荷量约9333.4 t,1995~2014年以-113.7 t/a速率呈显著下降趋势;相对于基准期,流域总氮负荷量在2021~2050年预计呈显著减少趋势。空间分布上,总氮负荷主要集中在流域中下游干流附近,中游东部和西部总氮负荷较低。③抚河流域多年平均总磷负荷量约1632 t,1995~2014年以2.1 t/a速率呈上升趋势;2021~2050年流域总磷负荷量相比基准期将呈增加趋势。空间分布上,在流域出口及中下游总磷负荷浓度较高,中游东部和上游总磷负荷较低。

The current research on nitrogen and phosphorus(NP)projection is mainly based on assumptions of unchanged climate change and socio-economic conditions,lacking consideration of the impact of socio-economic dynamics on NP loads.To study the changes in NP loads under the combined effects of climate and socio-economic factors,7 new climate scenarios(SSP1-1.9,SSP1-2.6,SSP2-4.5,SSP3-7.0,SSP4-3.4,SSP4-6.0,SSP5-8.5)from 5 climate models with comprehensive scenarios in the Sixth Coupled Model Intercomparison Project(CMIP6)were selected.Using the SWAT hydrological model,the spatial and temporal characteristics of the nitrogen and phosphorus loads in the Fuhe River Basin from 2021 to 2050 were simulated and analyzed relative to the baseline period(1995~2014)under the combined effects of climate change and socio-economic changes.The results showed that:①socio-economic changes were the main factors affecting the changes in nitrogen and phosphorus loads.However,the contribution of climate to the total nitrogen load change increased from 14.4%to 18.2%and the contribution to total phosphorus load change increased from 13.5%to 17.8%during 1981~2020,indicating that the impact of climate change on total nitrogen and phosphorus loads was increasing,the impact of socio-economic changes on total nitrogen and phosphorus loads was decreasing.②The average annual total nitrogen load in the Fuhe River was about 9333.4 t,with a significant decreasing trend at a rate of-113.7 t/a from 1995 to 2014.Compared to the baseline period,the total nitrogen load in the basin from 2021 to 2050 was expected to show a significant decreasing trend.Spatially,the total nitrogen load was mainly concentrated near the mainstream in the middle and lower reaches of the basin,with lower loads in the eastern and western parts of the middle reaches.③The average annual total phosphorus load in the Fuhe River Basin was about 1632 t,showing an increasing trend at a rate of 2.1 t/a from 1995 to 2014,and it was expected to increase from 2021 to 2050 compared to the baseline period.In terms of spatial distribution,higher total phosphorus load concentrations were found at the river basin outlet and in the middle and lower reaches,with lower loads in the eastern middle reaches and upper reaches.