水质标识指数法在赣江尾闾段水质评价中的应用

Application of a water quality identification index to evaluate the Ganjiang River estuary

赣江为鄱阳湖的重要补给水源,赣江水质对鄱阳湖生态有着重要影响。本文以电导率(EC)、浊度(TUR)、悬浮物(SS)、总磷(TP)、总氮(TN)、氨氮(NH4-N)、硝态氮(NO3-N)以及化学需氧量(COD)作为赣江水质评价指标,采用水质标识指数法对赣江尾闾段2015年10月30日、12月4日以及2016年1月12日、3月10日和5月30日5个时间点、3个支流、8个监测点的水质进行综合评价分析。分析结果表明:采用主要污染物水质标识指数法(PP-WQI)所得赣江下游北、中、南支流污染指数分别为3.84(COD)、3.53(COD)、3.84(COD/SS),综合水质标识指数法(CWQI)所得污染指数分别为3.8077、3.5003、3.7465;水质介于Ⅲ类和Ⅳ类之间,属于轻度污染,主要污染物为COD、TN和SS。水质在空间上表现为中支较好,南支和北支较差,上游优于下游;在时间上表现为夏季(5月30日)最差,冬季最好(12月4日和1月12日)。

The Ganjiang River is the main inflow to the Poyang Lake,and thus plays an important role in determining the ecological condition of the lake.In the present study,the water quality of the Ganjiang River was evaluated using the Water Quality Identification index(WQI)method,which summarizes parameters such as electrical conductivity(EC),turbidity(TUR),suspended solids(SS),total phosphorus(TP),total nitrogen(TN),ammonia nitrogen(NH4-N),nitrate nitrogen(NO3-N)and chemical oxygen demand(COD).Water sampling were conducted at eight monitoring points located in three downstream tributaries of the Ganjiang River on five separate dates(30 October and 4 December 2015,12 January,10 March and 30 May 2016).The results show that the calculated Primary Pollutant WQI(PP-WQI)values for the northern,central and southern tributaries of the Ganjiang River are 3.84(COD),3.53(COD)and 3.84(COD/SS),respectively.The calculated Comprehensive WQI(CWQI)values were 3.8077,3.5003 and 3.7465 for these three tributaries,which makes the water quality of the river classified somewhere between category III and IV.The main pollutants in the river are COD,total nitrogen(TN)and suspended solids(SS).Additionally,it is found that there is a linear correlation between the WQI indexes in groundwater and in surface water sampled at the same geographical locations.Spatially,the water quality is better in the central branch than in the southern and the northern branches,and better in upstream than in downstream.Temporally,the water quality is worse in summer(30 May)than in winter(4 December and 12 January).