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The entry of pollutants into a river is considered as the major reason of deterioration of its water quality. Toxic heavy metals, organic compounds, microbes, crude oil and grease, and even nutrients are the leading water contaminants excessively accumulating in the sediments of river which act as both sink and sources for these contaminants. Toxic heavy metals are more significant and hazardous environmental pollutants, originate from both natural processes (weathering of rocks, volcanoes emissions) and human activities (industries, vehicular emission, agrochemicals and mining etc.). These toxic metals present in agricultural soil may be accumulated in food chains which subsequent lead to human health risk. The present study is focused on determination of toxic heavy metals and physicochemical characteristics of Kurram River water and its effects on agricultural land, maize and wheat crops. In the study area i.e. from Surrani bridge (Bannu) upstream to downstream [Darra Tang near Essa Khel Mianwali (Punjab)], where Kurram River throws its water into Indus River; a total number of 110 samples were collected, out of which 30 samples were collected from river water, 30 from sediments, 25 from soil and 25 from each maize and wheat. River water samples were tested for heavy metals (Zn, Cr, Cu, Pb, Ni, Fe, Mn and Cd) and physico-chemical characteristics (pH, E.C, TDS, TSS, Na, K, Ca and Mg), while sediments, soil and crops samples were analyzed for toxic heavy metals only. Physico-chemical characteristics like pH and E.C were measured using their respective electrodes; light metals such as Na, K, Ca and Mg were analyzed using flame atomic absorption spectrometer (FAAS, Flame Atomic Absorption Spectrometer), while heavy metals analyses were carried out using graphite furnace atomic absorption spectrometer (AAS, Perkin-Elmer Analyst 700). Water quality of Kurram River is being degraded by the entry of toxic metals due to point sources such as municipal sewage, industrial waste, dumping of waste along the river banks, and non-point sources like atmospheric deposition and urban/agricultural run-off etc. 7 Contamination of water and other environmental matrices was decreased while going downward the streams. For the estimation of chronic health risk, health risk index (HRI) of food crop consumption was calculated using the formula HRI = daily intake of metals (DIM)/reference doze (RfD), while the average DIM was calculated by using the formula “DIM = Cmetal× Dfood intake /BWaverage weight.”. The values of pH in water samples varied between 8.3 to 8.7 unit with mean value of 633, while the mean values of electrical conductivity (EC), total dissolved solids (TDS), total suspended solids (TSS), Na, K, Ca and Mg were 633 μS/cm, 553 mg/L, 6.60 mg/L, 164 mg/L, 8.78 mg/L, 64.9 mg/L and 0.67 mg/L, respectively. All these parameters were found within their respective permissible limits set by World Health Organization (WHO) and United States Environmental Protection Agency (US-EPA) except in the samples collected from dumping point, Sikna sikander khel and Ghori wala which showed high concentrations of Ca i.e. 76.6 mg/L, 75.9 mg/L and 75.5 mg/L, respectively. Mean concentration of TDS (553 mg/L) and TSS (6.60 mg/L) was also higher than permissible limit set by US-EPA. According to Pakistan EPA (Pak-EPA), US-EPA and WHO, the concentrations of heavy metals such as Zn (3.5-6.0 mg/L), Cr (2.5-8.0 mg/L), Cu (2.5-7 mg/L), Pb (2.5-9.5 mg/L), Ni (2-10.5 mg/L), Fe (3.5-13.25 mg/L), Mn (4.0-10 mg/L) and Cd (0.042- 0.138) were found higher in the river water samples collected at in the study area. In the sediments, Zn concentrations (3.0-8.5 mg/kg), Cr (10.2-18.5 mg/kg), Cu (3.5-13.2 mg/kg), Pb (1.0-12.5 mg/kg), Ni (3.5-12 mg/kg), Fe (12-46.5 mg/kg), Mn (8.75-14 mg/kg) and Cd (0.101- 0.151 mg/kg) were found within their prescribed permissible limits set by USEPA. In soil samples, the concentrations of Zn (11-19.5 mg/kg), Cr (12-19.5 mg/kg), Cu (4.5-14.75 mg/kg), Pb (3.0-14.0 mg/kg), Ni (6-14.5 mg/kg), Fe (17-46.5 mg/kg), Mn (6.25-13.5 mg/kg) and Cd (0.113-0.163 mg/kg) were observed within permissible limits set by USEPA. In maize crop, the concentrations of Zn (4.85-7.9 mg/kg), Cr (5.85-11 mg/kg), Cu (5.95-10.25 mg/kg), Pb (8.55-11 mg/kg), Fe (9.5-23 mg/kg), Mn (7.05-12 mg/kg) and Cd (0.097-0.147 mg/kg) were greatly varied in the study area but observed within their permissible limits set by 8 WHO except Ni (8.9-11.5 mg/kg). In wheat crop the concentrations of Zn (4.25-7.5 mg/kg), Cu (5.75-8.75 mg/kg), Fe (9-22.25 mg/kg), Mn (6.5-11 mg/kg) and Cd (0.094-0.145 mg/kg) were found within safe permissible limits set by WHO except Cr (5.25-10 mg/kg), Pb (8-10.5 mg/kg) and some samples of Ni (8.75-11.25 mg/kg),. The concentrations of heavy metals in selected environmental matrices were observed in the order of: sediments>water>soil>maize>wheat. In water, sediments, soil, wheat and maize the order of toxic metal were: Fe > Mn > Ni > Pb > Cu > Zn > Cr > Cd, Fe > Cr > Mn > Pb > Cu > Ni > Zn > Cd, Fe > Zn > Cr > Cu > Ni > Mn > Pb > Cd, Fe > Ni > Mn > Pb > Cu > Cr > Zn > Cd and Fe > Mn > Ni > Pb > Cu > Cr > Zn > Cd, respectively. For these environmental matrixes, the order of metals was not the same which can be linked with mobility and uptake of these metals and also on the physiology of the grown plants. The DIM values of wheat and maize crops were less than 1, the highest HRI was recorded for Cu (0.7492), while the lowest for Cr (0.0203) in wheat. Similarly, the highest HRI in maize crop was recorded for Ni (0.04155), while the lowest for Cr (0.0041). All the HRI values of selected heavy metals were less than one (<1), thus falls within safe limits having no risk on the health of the inhabitants of the study area. The results also give interesting information about co-relation among selected heavy metals as environmental matrices irrespective of their sources whether natural or anthropogenic. The highest significant co-relation was observed between wheat and maize (r= 0.949), while the lowest co-relationship was observed between sediments and water samples (r= 0.659) for all heavy metals except Fe and Mn, in which the lowest significant co-relation could be seen between water and soil (r=0.130) and sediments and soil (r=0.709). It is revealed from the study that the water of Kurram River is being degraded by a couple of natural and anthropogenic activities which may cause risk not only for the aquatic life but also for the crops cultivating in the study area and finally on the health of local inhabitants. This study recommends the investigation of toxic metals in the human biological samples particularly for those leaving in the sites where high contamination is reported. Other pathways 9 responsible for toxic metals exposure of human beings should also be studied to give a complete picture about the total DIM and health risk and also fill the gaps present in the existing research. The concerned authorities and organizations should commit themselves towards a sustained effort for educating the people about the importance of water and soil quality, implementing the NEQs, and imposing taxes/fines on industrialists and inhabitants of the area on the basis of polluter pays principles to minimize not only the aquatic contamination but also the soil, sediments and food chains. TABLE OF
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