Evaluation of surface water and groundwater quality in the Tongken River Basin,Heilongjiang Province

To investigate the water pollution in the Tongken River Basin,Heilongjiang Province,this study evaluates the surface water and groundwater quality based on 11 surface water samples and 161 groundwater samples collected from the area. The results indicate that the overall quality of surface water is poor,with the comprehensive evaluation predominantly falling into Class IV water. The primary impact factors are chemical oxygen demand(COD),total phosphorus(TP),and mercury(Hg). According to the single-factor evaluation of total nitrogen(TN),most samples were classified as Class V water,with a few downstream sites reaching inferior Class V. The exceedance rate for TN reached 81%,and TP concentration exceeded the standard by 2.0 times. Owing to intensive agricultural development and special geological structures,the pollution level of surface water in the Tongken River Basin is higher than that in the Songhua River and Nenjiang River basins. Jointly influenced by geological background and human activities,groundwater quality in this basin is characterized by notable exceedances of manganese(Mn) and iron(TFe),with exceedance rates of 72.05% and 70.81%,respectively. Class V water accounted for 64.6% of the groundwater samples,a proportion higher than that in the Songnen Plain and Sanjiang Plain.