Seasonal variation in the nitrate concentration of groundwater samples surrounding the Dangkor Municipal Solid Waste Landfill

Abstract

Groundwater is classified as polluted if it contains sufficient chemical or biological contaminants to cause harm to living organisms. Nitrates are a common groundwater contaminant. In developing countries, a common source of nitrates in aquifers is Municipal Solid Waste (MSW) landfills, where they are produced from the decomposition of organic wastes. Nitrate pollution may cause groundwater quality surrounding MSW landfills to deteriorate if the issue is not managed. This research aims to investigate the presence and concentration of nitrates in leachate and groundwater samples surrounding the Dangkor landfill in Phnom Penh and recommend an effective approach for effectively monitoring and controlling these levels. Nitrate levels in leachate sampled from the landfill and groundwater sampled from surrounding tube wells was analyzed to assess (i) the seasonal variation in nitrate concentrations; (ii) spatial variation in the nitrate contamination of aquifers surrounding the landfill; and (iii) compliance with WHO standards. Groundwater samples were collected from three different wells at four sampling points located 500, 1000, 1500, and 2000 m from a reference point at Dangkor MSW landfill. Each sample was analyzed for the presence of nitrates before the concentration was analyzed. The results had several limitations but they suggest that there is no significant relationship between nitrate concentration in groundwater and distance from the landfill. Recorded nitrate levels were well within WHO guidelines for domestic use (50 mg/L) and as such, landfill leachate is not contributing to unsafe nitrate levels in groundwater aquifers between 500 m and 2000 m from the landfill site.