Document Type : Research Paper
Introduction
Among the aquatic ecosystems, rivers are considered as one of the basic sources of water supply for various uses, including agriculture, industry, and drinking, which are directly or indirectly affected by any human activity (Majlesi et al., 2019). Along with the growth and development of urban, industrial and economic activities during the last few decades and the production of various types of chemical compounds, pollutants have been unintentionally introduced into nature, which has brought serious problems and dangers to the environment and humans (Seifi and Rahi, 2019). . Currently, the pollution of aquatic ecosystems is one of the serious environmental threats (Bayati et al., 2020). Li et al., (2020) investigated heavy metals in the Songhua River in China. In this research, the index of heavy metal pollution was used, and the results of this index showed that the water of this river is below the critical level (100) for all metals. Sahoo and Swain (2020) examined heavy metals using the HPI index in 60 stations of surface water in the Indian peninsula. After comparing the results with international standards, the results showed that the water of these stations is within the standard range for drinking and agriculture. This research aims to evaluate the ecological effect of the presence of heavy metals (chromium, copper, nickel, zinc, iron and manganese) in the water of Gamasiab river using Heavy Metal Pollution Index, Metal Index and Heavy metal evaluation index was done.
Methodology
Water sampling was done in 2018 during two seasons of low rainfall (summer) and high rainfall (spring) from the stations specified in Figure 1 of the Gamasiab river with three repetitions. A total of 45 water samples were collected from 15 stations during each season. To prepare the water sample, 100 grams of the sample was poured into the beaker and 5 cc of Merck's 65% nitric acid was added to it. The sample was placed on a heater until its volume reached less than 10-20 cc, and after complete digestion, the sample was brought to 100 ml using distilled water. Finally, the concentration of the control sample and the digested samples was obtained using the ICP-OES inductively coupled plasma spectrometer (APHA, 2005). After sampling and transferring the samples to the laboratory, the required analyzes were done on each parameter. The results were analyzed using IBM SPSS and Excel statistical software, according to normality and non-normality, by relevant tests. The normality or not of the data was checked using the Kolmogorov-Smirnov test (Janisarvani and Shahrokhi, 2023). Then, to compare the results of two seasons, mean comparison (Man-Whitney-U test) was used, and Kruskal-Wallis non-parametric test was used to compare different stations. Correlation coefficient was used to check the relationship between parameters. Graphs were drawn using Excel software.
Results and Discusson
In this research, the concentration of heavy metals in Gamasiab river water was investigated to evaluate the river water pollution. According to the results, it was found that in the spring season, the highest concentrations are in the order of iron > zinc > chromium > nickel > manganese > copper, and in the summer season, the highest concentrations are in the order of iron > manganese > copper > zinc > nickel > It is chrome. Also, in both seasons, the highest standard deviation related to iron metal was obtained. According to the results, it was found that in the spring season, the highest concentrations are in the order of iron > zinc > chromium > nickel > manganese > copper, and in the summer season, the highest concentrations are in the order of iron > manganese > copper > zinc > nickel > chromium. be Also, in both seasons, the highest standard deviation related to iron metal was obtained. In order to increase accuracy, the samples examined in Gamasiab river water in spring and summer were compared with some studies done in Iran and the world.The concentration of metals in the Gamasiab river water sample showed lower values than other similar studies in other regions in most cases. As mentioned, the heavy metal pollution index is used to determine the effect of heavy metals on human health. For this purpose, we must compare the measured concentration of metals with the ideal concentration and standards of the World Health Organization (Farzi et al., 2022).
The numerical average of the HPI index for the spring season was -2.46 and the summer season was -3.36. As mentioned, this index examines the impact of a set of different metals on water quality (Seifi and Riahi, 2019). The results showed that, on average, Gamasiab river water is free of heavy metal contamination in terms of HPI index. This issue is due to the high water flow of the Gamasiab river and its self-purification along the route. Numerical analysis of MI index in two seasons, spring and summer, with values of 0.075 and 0.01, respectively, showed that Gamasiab river water is in the potable category in terms of heavy metal pollution.
In order to calculate the heavy metal evaluation index (HEI), the concentration obtained for each element is compared with the maximum allowed concentration of each element in water. The results showed that in spring and summer it was 12.75 and 12.35, respectively, which was lower than the risk threshold value (400).
Conclusions
In this research, in order to investigate the contamination of Gamasiab river water with heavy metals, water sampling was done in spring and summer and the concentration of heavy metals chromium, copper, nickel, zinc, iron and manganese was investigated. According to the obtained results, there is a significant difference between the concentrations of the investigated metals in the water of Gamasiab river at the level of 0.05. Examining the average concentration of the studied metals in the river water section showed that the average concentration of all metals except zinc metal in the water in the wet season was higher than in the summer season. The reason for the high concentration of most metals in the river water in the spring season can be attributed to the increase in rainfall and precipitation in the high water season, which leads to an increase in runoff that comes from land and land around industries, roads, agricultural lands, etc. high volume of pollutants. Especially heavy metals flow into river areas. Also, considering that the volume of river water is high in the high season. Therefore, the polluting substances remaining in the water column are carried by the water and do not have a chance to settle.
Acknowledgements
We sincerely thank the cooperation of the laboratory of environment department of Malair University for the cooperation of this research.