As content below detection limit.

WHO – World Health Organization.

Pb, Cd, Zn, Cu, Co, Cr, and Ni.

USEPA – United States Environment Protection Agency.

**Table 3.** Heavy metal content of water samples (mg L-1)

SD- Standard deviation.

(P≤0.001) in mean metal contents in water samples from different zones

\*\* Correlation is significant at the 0.01 level (two-tailed) (two-tailed; n=75)

**Table 4.** Correlation coefficients: water heavy metal concentrations

When compared with the metal profile of the rivers around the world (Table 5) the situation does not seem that desperate here, at least as far as heavy metal contamination is concerned. The picture, however, is quite different when we consider the WHO guidelines for drinking water and World average of trace elements in unpolluted rivers [56, 57], the concentration ranges of Pb and Cd were well above the international guidelines and acceptable concentra‐ tions for drinking water (Table 3). When compared to the world average of trace elements for unpolluted rivers, the river was considered polluted by Pb, Cd, Zn and Cu.


**Table 5.** Average heavy metal concentrations of rivers around the world (mg L-1)

#### **4.2. Soil**

Concentrations of heavy metals in the soil samples have been summarized in Table 6. Quan‐ titatively the metals were observed in the sequence Pb > Zn > Cr > Ni > Cu > As > Cd > Co (Figure 3), though their thresholds for concern, mobility in soil and toxicity are different so this trend does not necessarily reflect the threat of individual metals. Pb and Zn were found in fairly higher concentrations at all the sampling locations. Generally, an overall linear increasing trend of metal contamination was noted from site 1, before the Yamuna enters the city of Mathura, to site 10 where the river leaves Agra. Thus, maximum values for all metals were observed in the samples pertaining to Agra. In the third zone metal concentrations were seen to decrease gradually. One-way ANOVA and Fisher's LSD test indicate that mean Pb and Co content was different at all sites (P ≤ 0.001); while mean Cr, Cd, Cu, Ni, and As in zone 2 differed significantly from zone 1 and 3 (P ≤ 0.001). The latter did not differ significantly among themselves. Mean Zn content in zone 1 differed significantly from zone 2 and 3 (P ≤ 0.05). The difference between the latter was not significant statistically.


F value :'\*' statistically significant. Different letters in the same column denote significant statistical difference (P≤0.05) in mean metal contents in soil samples from different zones.

SD- Standard deviation.

**Rivers Pb Cd Zn Cu Co Cr Ni References**

0.001-0.00 5

28.65 3.12 253.74 36.29 - 76.26 70.1 [50]

20 0.3 95 45 90 68 [55]

0.8-9.37 0.009-0.32

0.05-0.341 0.47-1.76 0.27-1.58

**Cauvery river, India** 13.35 - 47.51 4.57 8.25 1.01 4.53 [13] **Brahmaputra river, India** - - 916 108 168 222 179 [10] **Ganga river, India** 76.36 11.5 332.5 48.39 - 5.36 4.88 [14] **Gomti river, India** 3.058 - 63.022 - - 0.064 0.013 [12] **Challawa river, Nigeria** 0.44 - 1.2 0.22 - 0.47 - [40] **Mghogha river, Morocco** 48.25 0.36 299.5 56.7 - 86.4 46.83 [41] **Sava river, Croatia** 34 0.5 91 24 - - - [42] **Pasig river, Philippines** 70 - 530 - 160 - 21.2 [43] **Rhine river, Netherland** 188.2 7.1 684.3 62.5 6.4 33.7 [44] **Zhujiang, China** 75.2 - 212 51 17.8 70.6 61.8 [45] **Almendares river, Cuba** 93 2.5 262 158 - 90 - [46] **Montevideo, Uruguay** 44-128 1-1.6 174-491 58-135 - 79-253 - [47] **Ribeira river, Brazil** 767102 0.2-5.5 15-5090 60 - - [48] **Amazon river, Brazil** 83 - 110 37.5 - 65 26.7 [49]

**Msimbazi river, Tanzania** - 0.9 79 14 - 12 8.7 [51] **Brisbane River, Australia** 20.1-81.9 1.9 40.8-144.031.1-30.2 - 14.2-54.3 - [52] **Siahroud river, Iran** 9.7 0.05 14.9 - - 1.03 - [53] **Gediz River, Turkey** 1.3 - 2.6 - 1.6 - 4 [54]

Concentrations of heavy metals in the soil samples have been summarized in Table 6. Quan‐ titatively the metals were observed in the sequence Pb > Zn > Cr > Ni > Cu > As > Cd > Co (Figure 3), though their thresholds for concern, mobility in soil and toxicity are different so this trend does not necessarily reflect the threat of individual metals. Pb and Zn were found in fairly higher concentrations at all the sampling locations. Generally, an overall linear increasing trend of metal contamination was noted from site 1, before the Yamuna enters the city of Mathura, to site 10 where the river leaves Agra. Thus, maximum values for all metals were observed in the samples pertaining to Agra. In the third zone metal concentrations were

**Table 5.** Average heavy metal concentrations of rivers around the world (mg L-1)

**Yamuna river (present**

554 Environmental Risk Assessment of Soil Contamination

**Danube river, Serbia and Montenegro**

**Avg. shale value/ world**

**avg.**

**4.2. Soil**

0.018-0.09 5

**study)**

**Table 6.** Heavy metal content of soil samples (mg kg-1)

**Figure 3.** Average heavy metal content in soil samples

All the metals in soils were positively (P<0.01) correlated with each other (Table 7). Significant negative correlation was observed between metal concentrations and soil pH (P<0.01). The same was observed in the case of Zn and Co with Organic matter. Phosphate is able to increase water-soluble lead forms from contaminated soils by 56.8– 100% [61]. This is clearly shown by the phosphate values (Table 2) obtained for different samples with maximum in zone 2 followed by zone 1 which probably led to higher Pb values in zones 1 and 2 (Table 6). Fertilizers contain from trace to several ppm of Pb, Zn, Cu, Mg [62, 63]. High P2O5-blended fertilizers and the pure phosphates, contain significant concentrations of several elements of potential environmental or agronomic concern [62, 64].


\* Correlation is significant at the 0.05 level (two-tailed; n=75)

\*\* Correlation is significant at the 0.01 level (two-tailed)

**Table 7.** Correlation coefficients: soil heavy metal concentrations

Agra is the fourth most populated city in Uttar Pradesh, India. With a population of 1.7 million (2011 census) it generates about 700 tonnes of solid wastes every day. It is also a major cause for adding contamination to soil and groundwater. Solid waste is also discharged from 200 hospitals and nursing homes along with 168 foundries, 52 tanneries, 300 shoe industries, 200 petha (a local sweet) manufacturing units, 50 dairies, 56 electroplating units, 15 silver vibrators and 15 galvanizing units. Significantly higher amount of metal pollution in the samples from the city (sites 6-10) is obviously due to untreated domestic/wastewater, sewage and industrial effluent discharged at these sites throughout the year. The increasing contamination as one proceeds downstream mirrors the extent of damage caused to the pedosphere.

Mean concentrations of heavy metals in soils at the sites studied were compared with threshold values of soil suggested by the Canadian Environmental Quality Guidelines [58]. It was observed that As (sites 1-13) and Ni (sites 6-10) crossed their respective industrial thresholds while the other metals (Pb, Zn and Cu) are well within it. Mean concentrations of As at sites 4-10 were approximately twice the thresholds suggested. Cd and Cr levels were above their thresholds only at site 10. However, the situation is drastically different in the perspective of the residential limits where in addition to these, the thresholds are exceeded even by Pb, Cd (10 sites each), Cr (5 sites) and also Zn and Cu at one site.

**Figure 3.** Average heavy metal content in soil samples

556 Environmental Risk Assessment of Soil Contamination

environmental or agronomic concern [62, 64].

\* Correlation is significant at the 0.05 level (two-tailed; n=75) \*\* Correlation is significant at the 0.01 level (two-tailed)

**Table 7.** Correlation coefficients: soil heavy metal concentrations

All the metals in soils were positively (P<0.01) correlated with each other (Table 7). Significant negative correlation was observed between metal concentrations and soil pH (P<0.01). The same was observed in the case of Zn and Co with Organic matter. Phosphate is able to increase water-soluble lead forms from contaminated soils by 56.8– 100% [61]. This is clearly shown by the phosphate values (Table 2) obtained for different samples with maximum in zone 2 followed by zone 1 which probably led to higher Pb values in zones 1 and 2 (Table 6). Fertilizers contain from trace to several ppm of Pb, Zn, Cu, Mg [62, 63]. High P2O5-blended fertilizers and the pure phosphates, contain significant concentrations of several elements of potential

**Cd Zn Cu Co Cr Ni As OM pH Pb** 0.821\*\* 0.479\*\* 0.889\*\* 0.629\*\* 0.909\*\* 0.933\*\* 0.894\*\* 0.426\*\* -0.802\*\* **Cd** 0.701\*\* 0.886\*\* 0.724\*\* 0.862\*\* 0.848\*\* 0.906\*\* 0.0876 -0.621\*\* **Zn** 0.723\*\* 0.915\*\* 0.689\*\* 0.653\*\* 0.744\*\* -0.493\*\* -0.371\*\* **Cu** 0.805\*\* 0.966\*\* 0.972\*\* 0.932\*\* 0.0260 -0.773\*\* **Co** 0.809\*\* 0.784\*\* 0.806\*\* -0.304\*\* -0.529\*\* **Cr** 0.991\*\* 0.944\*\* 0.0816 -0.834\*\* **Ni** 0.936\*\* 0.138 -0.837\*\* **As** 0.106 -0.739\*\* **OM** -0.242\*

On comparing metal concentrations with the values suggested for soil remediation by VROM, Netherlands [59], values of Zn (sites 7-13), Ni (sites 4-10) and Cr (site 10) were above the background values but below the intervention level. It is significant to note that in studies similar to the present one, the degree of contamination and the resulting 'hazard indices' for soils may vary when different thresholds, existing in only a few countries, are considered [65]. To increase the reliability of risk estimation due to contaminants, global consensus on such thresholds is urgently needed.

The concentrations of As are usually low, less than 6 ppm, for geological and soil environment [64]. It is estimated that about 60% As in the environment is from anthropogenic sources including As-based pesticides, fertilizers, and wastes from mines, smelter and tannery industries [66]. The relatively high values of As in the samples seem to be directly related to the discharge of domestic and industrial effluent as well as use of phosphate fertilizers, pesticides used in the agricultural activities in the region.

Highly significant positive correlation (P<0.01) was observed between soil and water content of Pb, Cd, Cu, Co, Cr and Ni. The results also indicate that metal concentrations in soil were higher than those in the water. This distribution pattern of heavy metals between the water phase and soil is expected as most heavy metal speciation studies have reported a similar pattern of distribution both in sea water as well as in lakes [67-69].

Several authors have pointed out the need for a better knowledge of urban soils [18, 70]. In the past few years, studies on urban soils in many cities have been carried out around the world. Some examples are Spanish [19, 71] and Italian cities [21, 72]. Other examples for European cities are Aberdeen [73], Athens [74], Oslo [22] and Belgrade [18]. The mean heavy metal contents for all zones are compared in Table 8 to those of some cities around the world. The differences concerning population, living habits, industrial activities, etc., cause significant differences in the metal contamination profile. Compared to average concentrations in urban soils in the world, the mean concentrations of Pb and Cu are up to 2—4 times higher in some cases but still less than London, Naples and Palermo. In the case of Cd, it is many times higher than Kattedan (India). Zn and Cr contents do not differ much; still they are less than those of Naples and Madrid. Ni content is more than almost all European cities, but less than Kattedan and Firozabad in India. Co values are less than those reported from other industrial regions of India. As content is less than that of Firozabad.


**Table 8.** Average heavy metal concentrations in urban soils from different cities across the world (mg kg−1)

It is encouraging to note that the mean concentrations of individual metals are below those reported from other industrial hubs within India i.e. Kattedan (Andhra Pradesh) [except Cd and As] and Firozabad (Uttar Pradesh). Kattedan Industrial Development Area (KIDA) is a major industrial area of Andhra Pradesh and houses 400–500 industries, including 150 large scale industries and 300 small-scale industries. Major sources of metals pollution are battery, electrode, oil refining, metal plating, textile, pharmaceutical, chemical paints, rubber, petro‐ chemicals, glass, therapeutics, and Pb extraction facilities [81]. This is also one of the contami‐ nated areas identified by the Central Pollution Control Board (CPCB) in New Delhi, and referred to as an ecological disaster area [81]. Firozabad is the hub of the Indian Glass industry.
