محسن مزرعاوی

Continuous monitoring and evaluation of surface water quality is necessary to protect the global ecosystem and human health. One of the most critical ways to estimate water quality is the WQI method. In order to check the water quality of the Maroon Dam lake located in Khuzestan province (15 km from Behbahan city), five sampling stations were selected at the inlet, outlet and inside of the lake. Sampling to measure the water temperature factor (with intervals of five meters by five meters from the surface to the bottom of the lake) and other factors such as dissolved oxygen, pH, biochemical oxygen demand, total phosphorus, total nitrogen monthly and from the surface to a depth of 60 meters (with distances of 20 meters by 20 meters) were carried out from October 2014 to September 2019 and finally the WQI index was calculated using qualitative parameters. The results of this study showed that the trend of changes in WQI index in different months of sampling in different stations in the quality class was medium to relatively good and the range of changes of this index was calculated between 49 in June to 66 in October. The depth measurement of temperature showed that in the lake behind the dam thermal stratification was created in spring (0 to 20 meters), summer and autumn (0 to 40 meters), but in winter, there is no such difference between surface and depth. According to the evaluation of the WQI index values of the reservoir water, it is suitable for all kinds of drinking purposes for domestic animals, agricultural purposes and raising resistant species of fish.

In this study, a comprehensive assessment of the occurrence and spatial distribution of heavy metals including Nickel, Lead, Zinc, Copper, Cadmium and Chromium, as well as, TPHs in the surface sediments of the coastal areas and far from the coast of the Persian Gulf in Bushehr and Khuzestan provinces were performed to identify the possible sources of sediment contamination and determining the degree of pollution. Eight pollution indices were used to evaluate the quality of sediments in terms of heavy metal and TPH pollution. The investigated areas could be distinguished by a significant degree of heavy metal pollution of Nickel, Cadmium and Zinc. High concentrations of Nickel and Zinc were observed in stations around Nakhiloo, Bushehr. The comparison of average pollution indices between regions showed that both Bushehr and Khuzestan provinces, respectively, with the average of contamination degree (CD) (20.25 and 22.11), modified contamination degree (MCD) (3.38 and 3.69), pollution load index (PLI) (31.17 and 57.57), potential ecological risk index (PERI) (353.54 and 349.39) have a significant degree and risk of Nickel and Cadmium pollution, especially in Nakhiloo area, Bushehr. Investigating the spatial fluctuations of the concentration of TPHs in two provinces showed an increasing trend from Bushehr to Khuzestan. However, areas were located in no pollution or low pollution zonation and were safe from the adverse biological effects of TPHs. Comprehensive and impressive strategies to control and reduce these pollutions, especially in polluted areas, should be considered, so that the sources of these pollutions be managed.

In this study, due to the importance of Doiraj Dam Lake, which supplies an important part of agricultural water of Dehloran and Mosian, the assessment of the lake water was carried out in order to develop aquaculture activities and investigate the possibility of fish farming in the lake behind the dam. For this, 4 stations selected, the entrance, before and ater the lake and sampling were done in three seasons by using Van veen grab with with 0.0625 m2. The results of this study were determined based on the biological indicators. In benthic indices, the quality of water was evaluated by determining the species composition and biological value of different species using Shannon-Wiener diversity indices and Hilsenhoff Family Biotic Index (HFBI). The HFBI index in the studied stations ranged from 3.07 to 6.07. In general, based on the biological indicators, in most of the stations and seasons, moderate pollution was observed, which was more evident in the stations before the dam due to its without move nature than the entry and after stations.

The object of this study was to investigate the status of physicochemical parameters and nutrients in demersal fishing grounds in the Iranian waters of the Persian Gulf from the Hormozgan province to Khuzestan province, from autumn and winter of 2017 to 2020. The local data of physical and chemical parameters of water were recorded and analyzed, by using a CTD (Conductivity, Temperature, and Depth)  device, during 2017, 2018 and 2020 years. Also, the sea surface temperature and chlorophyll-a were recorded from the MODIS (Moderate Resolution Imaging Spectroradiometer) satellite, aqua sensor, in 2018 and 2019 years. The average of remote sensing data of sea surface temperature and chlorophyll-a were 22.83 C° and 1.80 mg.m-3, respectively in the studied area, from 2018 to 2020. The average of local data of water temperature, chlorophyll-a, salinity and pH were 21.53 °C, 0.84 mg.m-3, 39.53 ppt and 8.28, respectively in the studied area during the years 2017, 2018 until 2021 winter. The average of concentrations of nitrate, phosphate and silicate were 0.034, 0.008 and 0.517 mg/L, respectively, in the present study. Based on the results, the amount of chlorophyll in the Persian Gulf has a relationship with the sea surface temperature and silicate. By increasing the sea surface temperature and concentration of silicate, the chlorophyll-a increases in the studied area. Changes in the concentrations of nitrate and phosphate had no significant effect on the concentration of chlorophyll-a in the studied area. The average of sea surface temperature and the concentrations of phosphate and silicate increased, but the concentration of chlorophyll-a and nitrite decreased from 2018 autumn to 2020 winter.