Heavy Metals (Co, Cr, Cd, Ni, Pb and Zn) in Sediment of Gorganrud River, Iran

RESULTS

Data for metal concentrations in the sediment samples are presented in Table 1. The mean concentrations of Co, Cr, Cd, Ni, Pb and Zn were significantly different between sampling sites (p<0.05), (Table 2). Maximum concentrations of Co, Cr, Cd, Ni and Pb were recorded in station 1 whereas maximum concentration of Zn was recorded n station 10. Minimum concentrations of Co, Cr, Cd, Ni and Pb were recorded in station 6 whereas minimum concentration of Zn was recorded in station 10 (Table 2). between 9, 8, 7, and 5 as well as 2 and 3 in addition to 4 and 10 in sampling sites. There was also no significant difference in Cr concentrations between 9, 8, 7, 5, 3 and 2 as well as 1 and 10 in sampling sites (Table 1).

Results of cluster analysis revealed two major clusters; Cluster 1 includes stations 1 and cluster 2 that includes the stations 2, 3, 4, 5, 7, 8, 9 and 10 (Fig. 2). As shown in Table 2, a significant positive correlation (p<0.001) was found between all of the heavy metals in sediment 1) was found between all of the heavy metals in sediment.

Fig. 2:	Dendrogram indicating relatedness of sites with heavy metal contamination among the fifteen sampling stations

Table 1:	Comparison and concentration (mean±sd) of heavy metals in different sampling sites of Gorganrud River
Values followed by the same letter are not statistically different among the groups (p>0.05). 1For comparison, we report the composition of the continental crust proposed by Taylor and McLennan (1985)

Table 2:	Simple correlation analysis between heavy metal concentration in the sediment of Gorganrud River
** Correlation is significant at the 0.01 level

DISCUSSION

The main sources of pollution of the river are urban, agricultural and industrial wastewaters. In this study heavy metal concentrations were determined at ten stations along the river (upstream stations and downstream). The results revealed higher concentrations of heavy metals (Co, Cr, Cd, Ni and Pb) at downstream stations (St1) compared to upstream stations. Several studies also revealed these facts. Olivares-Rieumont et al. (2005) and Kaushik et al. (2009) proved this finding in Almendares River and Yamuna River, respectively. Several sources for the increased metal concentrations appear likely. Chemical fertilizers containing Ni and Pb are used in agricultural industries of the regions around Gorganrud River. Cr and Ni compounds are used as pigments in the painting industry and as anti-fouling agents (Ramelow et al., 1992). The waste water of these industries is discharged to Gorganrud River directly, without any remediation; only a simple physical screening is being performed. The major sources of pollution in agricultural wastewater are fertilizers containing heavy metals such as Cd, Pb, Cr, Zn, and Ni (Spencer and Green, 1981). Our results also revealed that concentration of Zn was higher in station 5 and 6 compared to other stations. We found that in this study concentration of Cd, Cr, Co and Ni was higher compared to continental crust (Table 2). These high concentrations reflect the influence of anthropogenic activities. In decreasing order of magnitude, the average of concentration of heavy metals are: Zn (68.21)> Cr (49.50)> Ni (35.4)> Pb (14.01)> Co (12.83)> Cd (0.18). Cadmium compounds enter the water bodies from the discharge of effluents from paint manufacturing industries where cadmium also is used to produce excellent color from rechargeable battery (Spencer and Greene, 1981). Effluents from cadmium plating industries in the urban area of Gorganrud River (Fig. 1) are responsible for the presence of this metal in Gorganrud River. Concentration of Co ranged from 6.13 to 10.83 ppm n the sediment upstream of Gorganrud River (St6 to St9) whereas concentration of Co was obtained 19.56 ppm pling point 1. The highest level of chromium was obtained at sampling point 1 and the lowest level of chromium was obtained at sampling point 6. Cr contamination is originated by plating companies located in urban of Gorganrud River. Nickel also originates from the Ni plating processes and lead may result from the anodes used in the Cr plating tanks. Our result also revealed two major clusters: cluster 1, which represents highly contaminated sites and cluster 2, which represents sites of moderate and lower heavy metals levels in the sediments. In terms of the contamination of the stations under study, Cr and Zn seem to be the most problematic pollutant followed by Ni, Pb, Co and Cd. In general, heavy metal levels in the river were high, but varied widely among sampling stations.