Ecological Risk Assessment of Molecular Marker of Sewage Discharge (LASs) in the Abbas Abad Rivers in Hamadan

The aim of this study was to investigate the linear alkyl benzene sulphonates (LASs) as molecular markers to detect contaminants associated with municipal wastewater in Abbasabad River. Sampling was done in 17 stations from Abbasabad River in spring 2019. water temperature, (pH), (EC), (TDS), (DO) and(ORP) were measured at the sampling site. the LAS concentration was read using a spectrophotometer at 650 nm and the LAS concentration was calculated using the calibration curve and absorbed wavelength. Ecological risk assessment was performed by calculating RQ index. The results showed LAS concentration ranged from 0.11 to 2.65 mg/L with a mean of 1.25 mg/L. The entry of untreated wastewater into the Abbasabad River was the main cause of the high concentration of LAS. Ecological risk assessment results showed high risk in the studied basin. The results of Spearman correlation test between LAS and water quality factors showed positive relationship between LAS with salinity, TDS, EC and temperature. Comparison of LAS concentration according to Iranian standard for discharge to groundwater resources and agricultural and irrigation purposes showed that LAS concentration in 14 stations was higher than permitted for agricultural, irrigation and discharge into wells and at four stations above the permitted level of discharges to surface water sources. The concentration of LAS at 15 stations was above the permissible level of detergents in drinking water according to the Iranian and WHO standards. This study demonstrated the usefulness of investigating LASs as powerful indicators for tracking contaminants associated with urban wastewater discharge.