عنوان مقاله [English]
Khalkai River is located in northern part of Iran that passes through Masal City and enters Anzali wetland. The effects of trout farm effluents on the water quality parameters and self-purification in the Khalkai River were investigated. In this study, four trout farms and eight stations (inlet and outlet of each farm) were selected. Physiochemical characteristics and nutrients of water, including water temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), biological oxygen demand (BOD5), Chemical Oxygen Demand (COD), phosphate, nitrate and nitrite were monitored monthly in five month. The results showed that the average of these parameters from entrance stations were: 10.09±0.62 mg/lit for DO, 6.62±2.16 mg/lit for BOD5, 0.048 ±0.005 mg/lit for PO4, and 0.035 ±0.004 mg/lit for NO2. Also outlet station were calculated between, 9.20±0.73 for DO, 12.81±3.97 mg/lit for BOD5,, 0.075±0.007 mg/lit for PO4, and 0.088±0.009 mg/lit for NO2, respectively. All the parameters showed fluctuations at different stations, and for some of them such as BOD5, COD and phosphate, nitrate and nitrite there was significant difference between before and after farm stations (p<0.05). The parameters showed fluctuations at different stations, and for some of them such as BOD5, COD, TDS, EC, phosphate, and nitrite there was significant difference between different month (p<0.05). These results were due to the effects of trout farms and of the self-purification of river. Meanwhile, all the parameters showed changes in different seasons that were due to fluctuations of environmental conditions and activity rates of the farms.