Generally, microelements are beneficial to plants and human beings in adequate quantity, but its more abundance in freshwater bodies causes deleterious effects [28]. The reservoirs are the main source of water, which is used on a large scale for drinking, livestock and irrigation purpose. Industrialization, Urbanization and agricultural practices release a huge amount of wastewater in the river Bhima and its tributaries are getting adversely affected. This results in pollution of water and its bottom sediment. Reservoir water is widely used for drinking and irrigation purpose and due to its contamination; affects quality of soil in the agricultural land. The long term continues irrigation of crops with higher concentrations of a pollutant than the standards proposed by the environmental agency may lead to bio-magnifications at various tropic levels in the food chain. The polluted water interrupts soil fertility and productivity [29].
Table 5
Guidelines for concentrations of heavy metals in river sediments (mg kg− 1) and surface water(mg l− 1).( *long-term trigger value (LTV) and short-term trigger value (STV) designed for agriculture irrigation water standards).
Sr. No | Sample | Guidelines | Fe | Cu | Mn | Zn | References |
1 | Sediment | USEPA 2004 | 30 | 16 | 30 | 120 | [30, 31] |
2 | Surface Water | USEPA 2004 | 0.3 | 0.0025 | 0.05 | 0.005 | [32] |
3 | Irrigation Water | ANZECC (LTV) | 0.2 | 0.2 | 2 | 0.2 | [33] |
4 | Irrigation Water | ANZECC (STV) | 10 | 5 | 5 | 10 | [33] |
The level of Zn in natural surface waters is normally below 10 mg l− 1. Long-term exposure of Zn to various mammalian species causes tissue toxicity. Excessive Zn intake leads to Cu deficiency in humans [34] The Zn level of about 0.005 mg l− 1 in drinking water is optimum for human health. Our results revealed that Zn contents were more abundant in water samples than standard recommended values (Ministry of the Environment, 2004) [30] (see Table 5). However, the concentration of Zn in surface sediment was below the standards recommended by USEPA 2004[30]. Zinc is one of the important trace elements, plays a vital role in the physiological and metabolic processes of living organisms. However, its higher concentrations can be toxic to the organism. An elevated level of Zn in the diet has been shown to induce hypocalcaemia and bone desorption in rats [35]. Apart from this, carcinogenicity studies on mammals showed that zinc- ethanoate in drinking water (about 1.5 mg l− 1) induce the metastases and sarcoma [36].
The Mn in surface water is usually related to industrial pollution. On the basis of the provisional health-based guidelines, the standard value for Mn in drinking water is 0.5 mg l− 1. Here, we found that the values of Mn detected in surface water and sediment were higher than the permissible limit recommended by USEPA 2004[30]. The Mn concentration more than 30 mg kg− 1 in sediment causes hazardous effect to the ecosystem. The higher dose of Mn through the drinking water is associated with cancer risk. Several researchers have discovered that in different living organisms such as Drosophila melanogaster and mice the excess application of Mn enhances the frequency of mutations, chromosomal aberrations, tumor incidences, pancreatic cancer and pituitary adenomas [37]. Moreover, our results revealed that Fe, Cu, Mn and Zn concentrations in surface water were in excess in comparison with standards set for irrigation water by the ANZCC 2000[33]. Hence, continues land irrigations with water may affect soil profile of area around the Ujjani Reservoir.
Human health risk assessment of heavy metals in water specifies that the ADD through consumption of water was below the unit in all stations. As per the] risk assessment indices, If the value of the hazard quotient (HQ) is greater than 1.0, it indicates a high probability of adverse health effects due to exposure [14] In addition, the hazard quotients were lower than the postulated guidelines, suggesting that communities exposed to this water through ingestion pathways are at no risk of sickness associated with consumption of high levels of these contaminants. Also the mean HI of the examined stations was lower than unit, indicating there was no cumulative potential for adverse health risk with regard to reservoir water.
The Pollution load index (PLI) provides comprehensive information about the metal toxicity in a particular sample [19]. The PLI value of > 1 specifies polluted, whereas < 1 designates no pollution [20]. In our study, PLIs for the heavy metals in the studied sediments were less than 1 in all stations. The geoaccumulation index (Igeo) is used to quantify the contamination of metals in sediments, by comparing current concentrations of metals with the pre-industrial levels. Muller classification of Igeo, grouped it into seven grades: Igeo ≤ 0 (grade 0), unpolluted; 0 < ≤ 1 (grade 1),slightly polluted; 1 < Igeo ≤ 2 (grade 2), moderately polluted;2 < Igeo ≤ 3 (grade 3), moderately severely polluted; 3 < Igeo ≤ 4 (grade 4), severely polluted; 4 < Igeo ≤ 5 (grade 5), severely to extremely polluted; and Igeo > 5 (grade 6), extremely polluted [23].Here, the values of Igeo of studied metals were lower than 0 for Fe, Mn and Zn whereas values of Igeo for Cu are between 1 and 2 indicating sediments are moderately polluted with Cu and there is lower risk to ecosystem of the reservoir.
The valuation of the possible risk of the heavy metal contamination was proposed by Swedish scholar Hokinson. It is a method to estimate the heavy metal contamination from the viewpoint of sedimentology. According to this method, the potential ecological risk(ER) coefficient are computed for single element and potential ecological risk index (RI) for the multielement. According to Hakanson the following terminologies are suggested for the ER and RI values: (1) ER < 40, low ecological risk; 40 < ER ≤ 80, moderate ecological risk; 80 < ER ≤ 160, appreciable ecological risk; 160 < ER ≤ 320, high ecological risk; and > 320, serious ecological risk; Also, RI < 150, low ecological risk; 150 < RI < 300, moderate ecological risk; 300 < RI < 600, high ecological risk; and RI ≥ 600, significantly high ecological risk.[22]. RI method contains biological toxicology, environmental chemistry and ecology. It can assess ecological risks caused by heavy metals systematically [22]. In the present study, values of ER and RI were less than 40and 150 respectively, indicating that Ujjani reservoir have lower ecological risk for all studied metals.