Estimation of nutrient emissions into the river system of the southwestern Taihu Basin

Abstract

以MONERIS河流系统模型为基础, 建立了由农业土地营养盐平衡模型、流域营养盐排放模型及河道营养盐滞留模型3个模型组成的模型系统。该系统被用来计算太湖西南部河流流域的营养盐排放量。利用实测的河流系统的负荷数据, 对模型系统进行验证。验证结果表明, N、P计算负荷与实测负荷的偏差分别在10%及30%以内。利用该系统, 对1992-1996年及1997-2001年间的营养盐排放量进行计算。计算结果表明, 1997-2001年间的氮的年平均排放量为5646t/a, 该排放量比前5年的年均排放量减少827t/a。从磷的排放量来看, 1997-2001年间的年排放量为554t/a, 比前5年的均值减少45t/a。分析结果表明, 与1992-1996年相比, 1997-2001年间的点源排放量及农业土地营养盐剩余量的减少是流域营养盐排放量减少的主要原因。;According to MONERIS, three models were established to estimate the nutrient emissions into the river systems of the southwestern Taihu Basin, i.e, a nutrient balance model of the agricultural land, an emission model that was used for the estimation of nutrient emissions from catchments to river systems, and a riverine retention model that was used for the estimation of nutrient loads from emissions. The comparison of the calculated loads with the observed loads shows a deviation as low as 10% and 30% for nitrogen and phosphorus, respectively. It was estimated that the nitrogen input into the river system amounts to about 5645 t/a in the period 1997 - 2001. These emissions have decreased since the former five years by about 827 t/a. For phosphorus the emissions have reduced by 45 L/a and amount 554 t/a in the period 1997-2001. Analysis of the results show that the decrease of the nutrient emissions are mainly caused by the great reduction of nutrient surpluses from the agricultural land and the emissions from point sources.