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The present study was carried out with the aim of determining the concentration of heavy metals (zinc, lead, cadmium, and chromium) in water, sediment, and muscle and liver tissues of Barbus sharpeyi and Barbus xanthopterus of the Karoon River in order to investigate the status of heavy metals. In this river and to determine the health of the water ecosystem of the Karoon River in Bavi City, the evaluation of these two widely consumed fish species as biological monitors of heavy metals should also be done.

This study was conducted in April 1401 in order to investigate the concentration of heavy metals such as zinc, lead, cadmium, and chromium in six stations in the Karun River in Bavi city. The statistical population for the measurement of heavy metals with three replications included 18 water samples, 18 sediment samples, and 40 benny and gotan fish. Then, in order to measure the concentration of heavy metals in water samples, the sediment and tissues of Beni and Gatan fish after acid digestion were injected into the Contra-AA 330 model atomic absorption device. A comparison of heavy metal data from water samples, sediment, and fish tissues was done using SPSS software. The Shapiro-Wilk test was also used to check the normal distribution of the results. The statistical method of one-way analysis of variance was also used for general comparisons, and Tukey's test was used for multiple comparisons, and the differences were significant at the 95% level.

The average concentration of zinc, lead, cadmium, and chromium in water samples was 5.36, 1.80, 0.18, and 0.68 micrograms/liter, respectively, in sediment samples 46.57, 13.31, 2.89, and, respectively, 22.29 μg/g. Regarding the amount of zinc, lead, cadmium, and chromium in the muscle samples of benny fish, respectively, 57.13, 1.60, 0.94, and 0.51 micrograms per gram, and 11.65, 0.91, and 56, respectively, in Gatan fish. 0.0 and 0.41 μg/g were obtained. Also, the amount of these elements in Bani fish liver is 27.33, 3.49, 2.15, and 1.51 micrograms per gram, and in Gatan fish liver it is 23.49, 2.11, 1.40, and 1.32, respectively. µg/g was obtained. Comparing the amounts of elements in the edible muscle tissue of Beni and Gatan fish showed that the amount of zinc in the muscle tissue of two species of fish is lower than the international standards, but lead, cadmium, and chromium in the muscle tissue of Beni and Gatan fish were higher than some international standards. Pearson's correlation test showed that there is a positive and significant relationship between the concentration of metals in water samples, sediment, and tissues of Bani and Gatan fish (p<0.05). The results of calculating the MPI pollution index showed that the value of this index was greater than 1 for all the investigated elements. The BAF index in all samples was less than 1, and the BCF index was greater than 1 for zinc and cadmium elements and less than 1 for lead and chromium. Also, the results of calculating the MLR index showed that the amount of this index for the studied metals is about 0.5.

The concentration of all heavy metals studied in the non-edible tissue of the liver was higher than the edible muscle tissue of Beni and Gatan fish caught from the Karun River located in Khuzestan province. The high levels of the three elements lead, cadmium, and chromium in some international standards indicate the need to pay attention to the possibility of the continuous entry of the sources of these polluting factors, such as the effluents of agricultural poisons, herbicides, insecticides, and residues from fossil fuels. The use in industrial activities depends on the habitat of the mentioned species. Based on the metal pollution index (MPI, BAF, BCF, and MLR), it can be said that among the two investigated fish species, the amount of pollution and health risk of consuming benny fish is much higher than that of gatan fish. The MPI index showed that the level of contamination in the liver is higher than in the muscle. Also, the bioaccumulation factor was higher in Bani fish than in Gatan. The bioconcentration index also shows the high accumulation power of Beni and Gatan fish for zinc and cadmium elements. Therefore, these two species are suitable biological indicators for monitoring the pollution of heavy metals such as zinc and cadmium in the Karun River. Also, considering that the highest bioconcentration index of metals is in Beni fish, Beni fish can be the most indicative species in relation to the accumulation of zinc and cadmium elements in the Karun River. The ratio of muscle to liver also showed that this index can be an important biological index in monitoring heavy metal pollution in aquatic ecosystems. The concentration of heavy metals in the liver and muscle changes with the level of environmental pollution. In polluted places, heavy metals preferentially accumulate in the liver. The results of Pearson's correlation coefficient also showed that there is a significant correlation between the concentration of metals in water and the muscle and liver tissue of Beni and Gatan fish, so it can be concluded that the muscle and liver tissue of Beni and Gatan fish can be a suitable biological monitor for Heavy metals are investigated in the Karun River, and the liver is a more suitable monitor than the muscle. In general, based on the results of this study, it can be seen that the use of fish can give a better picture of the bioavailability of heavy metals such as zinc, lead, chromium, and cadmium. Also, in terms of the health status of the Karun River, using biological monitors, the muscle tissue and liver of Bani and Gatan fish, especially the liver, can be a suitable biological monitor for river health studies. Due to the entry of agricultural, urban, etc. effluents into this area, more periodical investigations and more accurate knowledge of the concentration of pollutants in different foodstuffs such as fish, plants, and agricultural fields are necessary. Also, it is necessary to accurately identify the origin of these pollutants and their input and production sources using chemical fingerprinting techniques so that better control can be done in order to manage these pollutants and finally prevent the penetration of such pollutants into the environment. Values should be avoided.

The aims of the present study were to investigate the macrobenthos communities in the Caspian Sea and to investigate the pollution of this ecosystem based on the pollution indices ABC (Abundance Biomass Comparison), BC (Biotic Coefficient) and ABC curve in 2018 (autumn and winter) and 2019 (spring and summer). According to the results, polychaetes, crustaceans, and bivalvia formed the major groups of macrobenthos communities with 4, 11 and 1 species, respectively. The polychaetes (mainly Streblospio gynobranchiata) included about 70% of the total abundance and the group of bivalvia (Cerastoderma glucaum) included about 76-93% of the macrobenthos in all seasons except in spring. The mean values of the Shannon index and evenness indices were calculated as (1.56) and (0.55), respectively. The annual pollution (ABC) and BC indices were obtained as -3.1 and 2.7, respectively. These values along with characteristics of ABC curve indicate severe stress caused by pollution in the Caspian Sea ecosystem. In this study, the percentage abundance of the invasive species S. gynobranchiata in macrobenthos communities was 52%, which is about 10% decrease compared to 2009 and 2010. This decreasing trend can be considered as positive evidence in the improvement process of the ecosystem in this part of the food chain. However the continuity of recovery trend needs more time, no force by new stressors, proper management, and reduced pollutions into the ecosystem.

This study aimed to investigate the geochemistry of toxic metals in soil and sediments of the west area of Khoy city to the Razi border, in Western Azerbaijan province. Evaluation of environmental geochemistry of heavy metals in soils and sediments of Iran are not much. As can be seen in addition to the ​​geology and tectonic and constructive factors of the area, human factors and industrial activities also can cause the presence of heavy metals in soil and sediments in areas around that area.
Cluster analysis showed significant correlation between almost all elements (with the exception of cadmium, copper) in this study. It seems that there is a good agreement between the two used indicators Igeo and EF pollution intensity. Both used indicators showed severity pollution for cadmium, cobalt, copper, manganese, nickel, lead, vanadium, zinc and iron. And for the rest of the elements can not be matched due to the use of different basic environment (such as amounts of shale, shell values and background values).