Unscientific management of municipal solid waste is one of the direct sources of contamination in developing countries like India. The first step to manage these anthropogenic stressors is to accurately assess its impact on the environment. Research and datasets pertaining to it are important as they provide a robust actionable quantitative assessment of the biogeochemical parameters in play. Although there is a substantial body of research about soil and water contamination in the developed, fully urbanized metropolitan cities of India; rapidly developing cities like Silchar in Assam lack such rich datasets and research. Our investigation carried out during October–December 2019 was an attempt to assess parameters such as the quality of groundwater and soil near a dumping site in Silchar, which is the state’s second largest city.
Soil and groundwater samples were sourced from several sampling points around the vicinity of the dumping site. The pH, electrical conductivity (EC), moisture content, porosity and bulk density of the soil samples were analysed whereas the pH, EC, total suspended solids (TSS) and total dissolved solids (TDS) of the groundwater samples were also evaluated. Further, the soil samples were also assayed for the presence of heavy metals using Atomic Absorption Spectrometry. The detailed analysis of the soil and groundwater samples we carried out in and around the municipality dumping site at Nagapatty in Silchar established beyond doubt that it has been affected by the rampant and reckless dumping of untreated municipal sewage.
The soil and groundwater analysis
The overall pH of the soil samples was observed to vary between 4.2 and 7.0, indicating an acidic tendency of the soil. This was, however, not surprising as the production of acidic leachate is common around waste disposal sites. A wide range of trace metals was also observed to be present in the soil, including Zn, Fe, Ni, Cu and Cr. This presents a matter of immense and grave concern as each of these metals poses serious threats to humans.
Using the trace metal concentrations, we calculated a metric known as the Geo-accumulation Index which is essentially the ratio of the measured concentration of a particular trace metal in a soil sample and its geochemical background value in the average shale. To our utter dismay, we discovered that the Geo-accumulation Index of all the trace metals we assayed for fell into the “extremely contaminated soil” category.
The groundwater analysis revealed a picture remarkably similar to the one obtained from the soil sample analysis. Most of the groundwater samples exhibited pH levels below the desired limits. The standard limit of pH for drinking water is 6.5–8.5. In the present study, we found that the pH of 64% of the water samples was below 6.5, therefore rendering it unfit for drinking purposes.
TDS is a water quality metric signifying the concentration dissolved particles or solids in water whereas TSS is a measure of the fine inorganic particles suspended in water. Although the TDS values were within the WHO prescribed limits, the high TSS was indicative of the fact that the water was aesthetically unacceptable for domestic purposes.
Groundwater samples were analysed for the trace elements such as iron, copper, chromium, nickel, arsenic and zinc. The iron, copper and nickel levels in groundwater samples exceeded the guideline values but the chromium and zinc concentrations were found to be within limits. The findings obtained from this assessment demonstrated that the groundwater of the study area was unreliable and unsuitable for drinking purposes and the soil was also unfit for agricultural purposes unless extensive remediation measures are taken as soon as possible.
The team consisted of (late) Mr. Rahul Das and Mr. Gaurav Roy who, in association with Voice of Environment, a non-governmental organization of the youth based out of Guwahati, led the pilot study that included laboratory sampling of water and soil samples. The preliminary study was done under the scholarly guidance of Assam-based Moharana Choudhury, a reputed environmentalist and Secretary, Voice of Environment (VoE); Dr. Dibakar Deb, Head of Chemistry Department, Karimganj College; and Dr. Sumita Paul Purkayastha, Assistant Professor, Dept of Chemistry. The study was followed by detailed data analysis and stakeholder engagement programmes which include community sensitization and mobilization. The team was further enriched by the scholarly expertise and peerless supervision of eminent scientists such as Prof K G Bhattacharya, Department of Chemistry, Gauhati University, Assam; Dr. Darpa Sourav Jyethi, Scientist, Indian Statistical Institute, North-East Centre, Tezpur, Assam; Dr. Joystu Dutta, Assistant Professor and Head of Department, Environmental Sciences, Sant Gahira Guru Vishwavidyalaya, Sarguja, Chhattisgarh; and Tirthankar Sen, an M.Tech student of Department of Biosciences and Bioengineering, Indian Institute of Technology (IIT) Guwahati. The entire research team would like to pay tribute to one of their members Rahul Das whose life was tragically cut short in a road mishap in Guwahati.
The highlights of the research findings were accepted and published by International Journal of Energy and Water Resources, Springer-Verlag on March 4, 2021. It is imperative that such studies are consistently undertaken to ensure environmental resource and solid waste management in other prominent cities of India and the world.
Joystu Dutta*1 and Tirthankar Sen2
1Department of Environmental Sciences, Sant Gahira Guru Vishwavidyalaya, Sarguja, Chhattisgarh
2Department of Biotechnology, Techno India University, Kolkata, West Bengal