Pollution Load Assessment in the Soil and Water Resources: A Case Study in Karun River Drainage Basin, Southwest of Iran

Abstract

Agricultural, industrial and urban waste discharges along with natural factors such as drought conditions are the main cause of decline in soil and water resources quality.  Karun and Dez rivers, the largest drainage basin in the southwest region of Iran, are an important components in the climate system, and play a key role in human health and life of the study area. The issue has grown in importance in recent developments in sectors of agriculture, industry and urban that it has considerably affected water quality and increased contamination loads to the rivers. The aim of this paper is to determine and assess the contamination status and pollution loads to the studied rivers. The main issues addressed in this paper are pollution loads of: a) Agricultural drainage, b) urban wastewaters, and c) industrial wastewaters. A total of 284 samples consist of 24 sources of agricultural drainages outlet, 9 sources of industrial wastewaters discharges, 38 sources of urban wastewaters discharges were collected during four times in 2013-14 in an attempt to make each season one sample. 15 physical and chemical parameters including flow rate, COD, PO4, BOD, DO, NO3, NH3, TSS, pH, EC, TDS, Total Coliform, Fecal Coliform, Cl-1 and SO4-2 were determined for each sample. Results showed that agricultural activities had the higher risk of degrading the quality of soil and water resources in Khuzestan Plain and Karun basin in salinity and increased load of soluble salts (TDS).The Agricultural drainages, with the capacity of 2,375×106 m3.yr-1, and a salt pollution load of 11,862×103 kg.d-1 had the greatest contribution among pollutants. Dez River in Haft-Tapeh region with the 285×103 kg.d-1 of organic pollution based on chemical oxygen demand (COD) being discharged by the sugarcane industries subsidiaries, such as KaghazPars and Harir, is considered sensitive and vulnerable regarding natural self-purification. Results show that Ahvaz, by discharging 400×103 m3.d-1 of urban wastewater to Karun River, from the gateway to the southern end of the city, is one of the major centers of organic pollution based on biochemical oxygen demand (BOD) and ammonia and microbial pollution loads.