社会经济系统磷物质流分析--以安徽省含山县为例

氮、磷等营养物质过量输入是造成我国湖泊富营养化问题日益严重的根源,磷作为水体富营养化过程关键限制元素,主要来自流域社会经济系统中的人类活动排放,因此,定量刻画社会经济系统内的磷流动路径是追踪水体外源磷来源和进行有效控制磷排放量的前提。以巢湖流域的安徽省含山县为例,构建社会经济系统磷流分析框架,建立磷流核算模型,并在实地调查和数据统计分析的基础上定量刻画了含山县2008年度社会经济系统磷流路径。结果表明,2008年含山县社会经济系统向水体排放的磷总量为1592t,其中农业种植子系统的排放所占比例最大(77%),该子系统的磷利用效率也较低(45%)。因此,含山县富营养化治理的重点是优化农业种植系统的磷流路径,主要措施包括合理施肥、科学排灌等。

Anthropogenic phosphorus flow analysis of Hanshan County in Anhui Province

Excessive input of nutrients such as nitrogen and phosphorus into natural water bodies is an escalating factor that leads to eutrophication.As a critical limiting nutrient for the growth of aquatic biomass,phosphorus is mainly from human activities of the socio-economic system.Hence,quantifying the pathway of phosphorus throughout the socio-economic system is essential for the selection of appropriate measures to mitigate phosphorus discharge.The study develops a framework for analyzing phosphorus flows in socio-economic at county which divides the life-cycle of phosphorus flow into four stages: extraction,fabrication and manufacturing,use,and waste management.Meantime,we subdivide the stage of use into five major subsystems: agriculture,large-scale livestock breeding,domestic breeding,rural consumption,and urban consumption.Furthermore,based on principle of mass conservation,we develop formulas for calculating phosphorus flows which is mainly expressed in three kinds: constant equations,dependent equations and balance equations.In addition,we apply our framework and calculation formulas to quantify the anthropogenic phosphorus flows of Hanshan County in 2008.Hanshan county located east of Chaohu Lake.Our data mainly come from questionnaire,face-to-face interviews,official statistics,published literature,and expert consultation.The data of phosphorus content of the products are collected from published literature and expert consultation.The data of phosphorus product consumption per capita are acquired through questionnaire and face-to-face interviews.The other data,such as planting area and rural and urban population,come from official statistics. The results show that,in 2008,the total input of phosphorus in Hanshan county is 5324 tons,of which,59% is imported from outside with purchased fertilizers.The total output of phosphorus in Hanshan County is 3023 tons,and 22% is exported outside.In terms of phosphorus loss,there was 1592 tons of phosphorus discharged into local surface water in Hanshan county,which primarily comes from agriculture(77%) and rural consumption(18%),and the other subsystems contribute only 5% of the total phosphorus loss into watercourses.Moreover,agricultural subsystem accounts for the largest proportion of the phosphorus input with the lowest phosphorus use efficiency(45%) due to excessive phosphorus loss.At the same time,intensive input of fertilizers in agricultural practices was identified as the most important source of phosphorus load on local surface water.Based on our above analysis,we propose that the eutrophication of local water bodies could be addressed by optimizing agricultural structure,promoting rational fertilization and scientific farming,encouraging the appropriate disposal of livestock manure,enhancing residents’ environmental consciousness and improving the waste management system.Limitations of the methodology and data are also discussed.We will simulate and analyze the policies and control programs with the substance flow model and scenario analysis in future study.