Assessment of seasonal variations and human health risks due to heavy metals in water, soils and food crops using multi-indices approach

摘要

We collected water samples from contaminated Buddha Nullah drain in Ludhiana district of Punjab (India) during pre- and post-monsoon seasons of the year 2017 and 2018. The soil and plant (wheat and rice) samples were also taken from fields cultivated near the water sampling sites. The drain is mainly contaminated by discharge of industrial and urban effluents from the surrounding areas and its confluence with Sutlej River (a tributary of the Indus River). Water samples were analysed for nine metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn). Soil, rice and wheat grain samples were analysed for total metals. Besides this, soil samples were also analysed for and DTPA-extractable metals. The concentration of Cr, Pb and Fe in water exceeded the WHO guidelines during all the seasons. Total Zn, Pb, Mn, Ni and Co concentration in soils exceeded the permissible limits, whereas the average concentration of Fe, Pb, Co and Cd in rice and wheat grains exceeded the permissible limits. The bioaccumulation factor (BAF) for DTPA-extractable heavy metals was in the order: Fe Cr Co Zn Pb Cd Mn Cu Ni (BAF values 1 for all the metals). Heavy metal toxicity load values (HMTL) in water samples were lower than the tolerable toxicity load of heavy metals. However, heavy metal pollution index (HPI) was higher than 100 in all the water samples. Based on the grading of geoaccumulation Index (I-geo), total Cd concentration showed extreme contamination around the soils of Buddha Nullah. The cancer risk associated with heavy metals due to intake of wheat and rice grains and ingestion of soils were in the order: Cd Ni Cr. Spatial distribution maps of HPI showed the maximum contamination and health risks were around the areas having higher industrial and urban activities These results suggest that heavy metals particularly Cd cause potential health risks to urban residents and environment. The HPI and HTML for water, Igeo for soils and BAF for plants are useful for assessing heavy metal contamination. The controlling measures must be taken to reduce the heavy metal contamination in the drain by checking of the urban and industrial effluents discharged in it and cleaning of the Buddha Nullah drain should be initiated to improve the water quality of Sutlej River.