RESUMO
Various developmental projects and economic actions such as mining, industries, urban expansion, and agricultural activities contribute toxic heavy metals into the soils and it adversely affects to human health and broadly the environment. For the scientific study (coal mining region of Eastern India) around 120 soil samples were collected from top (0 - 20 cm) and subsurface soil (20 - 50 cm) of coal mining, semi mining and non mining type of land use sites to assess ten heavy metals applying standard methods and indices for the assessment of pollution load and human health risk. Statistical analysis clearly indicated that Fe, Mn, Zr are the most dominantly distributed in the study region. Coefficient of variance (CV)showed that there was very less variation in the metal values among samples of any particular landuse site. Correlation coefficient (0.05% level of significance) depicts that metals were very strongly correlated with each other in every site of Neturia block. Igeo (Geo- accumulation index) values of Fe and As indicated moderate to low pollution in the topsoil of study area. It is because of their regional background value. Enrichment Factor (EF) also showed thatcontamination of Fe ismainly supplied by natural factors (EF < 2)i.e., weathering of parent rock in all over the study area. All other heavy metals indicated their anthropogenic sources (EF > 2)on top and subsurface soil both of three landuse site. Degree of contamination (Cdeg), modified degree of contamination (mCdeg), contamination factor (CF) and pollution load index (PLI) clearly suggest that topsoil of coal mining sites is most polluted than two other sites. Subsurface soil of mining sites also indicated comparatively higher pollution load than subsoil of semi mining or non mining sites. PLI values have been classified into four groups i.e., high pollution (> 6), medium pollution (6 -3), low pollution (3 - 1) and no pollution (< 1) zone. There was no PLI value < 1 in topsoil of the study area. But subsurface soil of non mining site indicated no pollution to the soil. Spatial mapping using Inverse Distance Weightage (IDW) on Arc GIS 10.4 software showed clear variation of metal concentration and pollution load to the top and subsoil of the study area. Human health risk of non - carcinogenic typeisdue to heavy metals intake of topsoil through three exposure pathwaywhich indicates the health risk of HI dermal> HI ingestion> HI inhalation for both the adult and children. Mean values of total HI showed that children are more prone to health risk in comparison with adult. There was no soil sample that exceeds its HI values > 1 for adults and thus no obvious health risk was found from soil heavy metals for adults.On the other hand, topsoil of mining sites indicated HI values >1;therefore, children are prone to health risk in this site. The present investigation suggests that coal mining region is highly polluted by their heavy metal burden on soil. Industrial and semi urban areas of semi mining region are also affected by heavy metal dust to its soil. Agricultural activities in non-mining region indicated lower pollution than other landuse sites. Remedial measures are highly needed to control heavy metal pollution of different landuse sites at colliery region to sustain environmental quality and human health as well. Modern scientific technologies and public awareness should be very useful on this way.
