Author/Authors :
Niroula ، Kereena Department of Environmental Science - Tribhuvan University, Padmakanya Multiple Campus , Shrestha ، Mahesh Department of Mathematics and Statistics - Tribhuvan University, Padmakanya Multiple Campus , Adhikary ، Bijaya Department of Environmental Science - Tribhuvan University, Padmakanya Multiple Campus , Shakya ، Sudarshana Department of Botany - Tribhuvan University, Bhaktapur Multiple Campus , Shakya ، Bhushan Department of Chemistry - Tribhuvan University, Amrit Campus , Pradhananga ، Achut Ram Department of Chemistry - Tribhuvan University, Padmakanya Multiple Campus , Shakya ، Bindra Devi Department of Mathematics and Statistics - Tribhuvan University, Padmakanya Multiple Campus , Pant ، Dipesh Raj Department of Environmental Science - Tribhuvan University, Tri-Chandra Multiple Campus , Shakya ، Pawan Raj Department of Chemistry - Tribhuvan University, Padmakanya Multiple Campus
Abstract :
Ever-increasing population, rapid urbanization, and industrialization have critically deteriorated the urban soil quality. This study was conducted to assess the ecological risk of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and lead (Pb) in four different land-use urban soils viz, commercial area (CA), heavy traffic ring roadside (HT), residential area (RA), and agricultural farm (AF) of Kathmandu District, Nepal. For this purpose, concentrations of the five heavy metals (HMs) were determined by using a flame atomic absorption spectrophotometer (FAAS), in a total of 31 soil samples collected from all four land uses. Pollution indices such as contamination factor (CF), degree of contamination (CD), pollution load index (PLI), geo-accumulation index (I-geo), ecological risk factor (ER), and potential ecological risk (PER) were used to assess the ecological risk posed by the HMs. The overall mean concentrations for Cd, Cr, Cu, Ni, and Pb were 0.98, 137.05, 79.80, 100.00, and 72.27 mg/kg, respectively, and were found 2-4 times greater than the background values. The statistical analysis revealed a poor correlation of the HMs against pH and total organic carbon (TOC) suggesting little influence on HMs contamination. Results also showed the highest concentrations of the HMs in HT soils among the land use types. Ecological risk assessment revealed CF (0.42-5.06) and CD (7.83-15.72) values as indicators for low to considerable, and moderate to considerable risks respectively, in soils of all land uses under the present investigation. Whereas the PLI values (1.12-2.96) corresponded to the polluted urban soils, the Igeo values (0.08-1.02) indicated an unpolluted to the moderately polluted class of soil contamination in all the land-uses. Likewise, the ER (0.91- 114.90) and PER (113.97-170.14) values pointed out that all the land use urban soils were exposed to a class of low to considerable, and moderate to considerable risks, respectively. Among the HMs, Cd, and Pb posed a comparatively high ecological risk for soils of all land uses and the estimated indices indicated HT as the most vulnerable land use suggesting immediate control measures.
Keywords :
Ecological risk , Heavy metals , Kathmandu district , Soil pollution , Surface soils
