**3.2. Soil**

**3. Physico-chemical profile**

550 Environmental Risk Assessment of Soil Contamination

of faecal wastes in adjacent areas along the river.

**Table 1.** Physico-chemical profile of water

Physico-chemical properties of the water samples collected from the study zones are men‐ tioned in Table 1. The pH values indicate neutral nature of river water acceptable as per BIS [36] and WHO [37] guidelines. A reading of 6.5 to 7.5 is considered neutral, suitable for general plant growth [38]. Conductance which reflects the status of major ions/inorganic pollution and is a measure of total dissolved solids and ionized species in the water, varies between 434 – 503 µmho/cm. Total dissolved solids were highest in zone 2. The hardness of water body is regulated largely by the levels of Ca and Mg salts. Other metals if present such as Fe, Al and Mn may also contribute to hardness. Most parameters were within their respective acceptable limits [36, 37]. Electrical conductivity was low. High COD, BOD and low DO in zones 1 and 2 are due to the discharge of huge amount of the untreated urban and industrial wastewater/ effluents indiscriminately. All three zones were faecally contaminated. Bacterial contamina‐ tion ranged from19000—93000 coliform/100ml; the values are much higher than recommended values of 1coliform/100ml. Most of these coliforms were of faecal type due to gravity discharge

**Parameters Zone 1 Zone 2 Zone 3 Acceptable**

pH (1:2.5) 7.31 7.23 7.61 6.5-8.5 Total Dissolved Solids (mg/l) 266 314 245 500

N-NO3 (mg/l) 3.54 4.37 4.11 10 N-NH3 (mg/l) 2.34 2.36 1.63 10 Total hardness (mg/l) 227 223 210 250

Chloride (mg/l) 8.5 8 9 250

Dissolved Oxygen (mg/l) 5.63 - 8.67 >5

Conductivity (µmho/cm) 462 503 434

Total alkalinity (mg/l) 203 188 209 Chemical Oxygen Demand (mg/l) 23.5 24.3 11.3

Fluoride (mg/l) 0.37 0.37 0.32

Biological Oxygen Demand (mg/l) 9.63 10.7 5.34 Sodium (mg/l) 6.81 6.62 7.15 Potassium (mg/l) 0.38 0.4 0.38 Ca hardness (mg/l) 124 131 115 Mg hardness (mg/l) 83 96.4 91.6 Faecal coliforms (MPN/100ml) 86000 93000 19000 Streptococcus (MPN/100ml) 64000 71000 17000 **Limits [36, 37]**

**3.1. Water**

The soil of the study area is characterized by alluvium, which is an admixture of gravel, sand, silt and clay in various proportions deposited during the quaternary period. The area is a part of Indo-Gangetic alluvium of quaternary age and is made up of recent unconsolidated fluviatile formations comprising sand, silt, clay and *kankar* with occasional beds of gravel. The topsoil is coarse and angular sand with small clay fraction. The sub-soil is sandy throughout. The stabilized topsoil is reddish brown with sand and clay mixed. The minimum depth of topsoil layer is 60 cm.

Physico-chemical properties of soil samples are given in Table 2. The topsoil in the study area is sandy loam (sand 60-80%, silt 10-24%, clay 8-16%). It has high exchangeable sodium percentage (ESP) values and moderate water retaining capacity. The sub-soil is sandy through‐ out. Soil pH ranged from neutral to alkaline. Zones 3, 2 and 1 were classified as very low, low and medium in organic matter, respectively.


#### **Table 2.** Physico-chemical profile of soils

The electrical conductivity (EC) of soils ranged from 0.33-0.54 dS/m. Zone 1 and 2 soils fall in very high (>100 kg/ha), soils from zone 3 and control site in the high (50-100 kg/ha) phosphate availability bracket. Soils from zones 1, 3 and control displayed medium (130-330 kg/ha) potash levels while zone 2 was low (<130 kg/ha) in available potash. Nitrogen content in the soil samples ranged from 50.1 – 112.9 kg/ha.
