Pollution monitoring of Khorram-Rud River - Lorestan Province using macroinvertebrates as biological indicators

Human activities are the main cause of river pollution that continuously affect the water quality of the rivers. In this study, the population structure of macroinvertebrates was investigated as a biological indicator for water quality in the Khorram-rud River. For this purpose, a number of 4 stations were selected and some physicochemical parameters along with macroinvertebrates sampling were done monthly for 12 months (December 2018- November 2019) in each station. Totally 26 families in 14 orders of macroinvertebrates with the domination of families Chironomidae, Baetidae, and Tricorythidae, respectively were found. The results of physicochemical factors showed that the lowest and highest water temperatures recorded were 8.66 ± 0.57 in December and 23.66 ± 0.57 in July, respectively, the maximum average dissolved oxygen in March 5.83 ± 0.28 mg/l  in the station (1), and the minimum was 0/00 mg/l in a station(4). pH value recorded with a minimum of 6 ± 0.86 in January and a maximum of 8 ± 0/00 in June. The average change of nitrite in different stations showed a slight fluctuation but was higher than the allowable limit in all stations. The highest amount of nitrate in a station (3) in June was 36.66 ± 5.77 and the lowest in a station (1) in December recorded as 2 ± 0/00 mg/l. The seasonal variations in density of macroinvertebrates indicate the maximum density in autumn and the minimum density in winter. The results based on (BMWP, ASPT) and richness and diversity indices (Shannon-Weiner, Margalef) indicated that the Khorram-rud river water is in the contaminated water class.