Solid waste is the refuse generated from human activities during industrial, commercial, mining, and agricultural operations. With an increase in population and industrial activities, solid waste must be appropriately managed and contained to avoid an adverse impact on the environment and human health.
Traditionally, landfill sites are used for solid waste management because of their simplicity, large handling capacity, and minimal operating costs. However, improperly maintained landfills and dumping sites with poor leachate collection systems become a potential source of soil, surface and groundwater contamination. The composition of solid waste can alter soil chemistry and cause a considerable environmental impact by producing leachate and biogas. The most common contaminants found in solid waste leachate are chromium, dioxin, hydrocarbons, organochlorines, PAH, PCB, pesticides, radionuclides, TPH, VOC, persistent organic pollutants (POPs) as well as deadly pathogens. Hence, employing a proper leachate monitoring program is obligatory for the safety and risk assessment.
Soil and groundwater testing are a hallmark of good leachate monitoring programs and critical in site investigations or environmental risk assessments. Soil and groundwater matrices and chemistries are complex and highly variable, making accurate measurements challenging. The United States Environmental Protection Agency (USEPA) recommends Toxicity Characteristic Leaching Procedure (TCLP) to determine hazardous elements present in waste. This chemical analysis process simulates contaminant leaching in a landfill environment over time, prior to depositing the waste in designated landfills. TCLP determines the mobility of organic and inorganic contaminants (metals, pesticides, herbicides, and solvents) in liquid, solid, and multiphasic wastes.
The Leaching Environmental Assessment Framework (LEAF), is an alternative evaluation system designed to identify and accurately describe the release of inorganic, semi-volatile organic, and non-volatile organic constituents of potential concern (COPCs) in solid materials. LEAF methods were designed to provide a flexible and customizable framework for distinguishing leaching characteristics under a range of conditions for a variety of solid materials in contact with ground or surface water.
To ascertain the extent of pollution, regulatory agencies (e.g., USEPA) require the use of official methods when testing soil and groundwater. Soil and groundwater are tested for physicochemical properties, including total dissolved solids, pH, hardness of water, cations, anions, organic matter, total carbon, nitrate, ammonium, and heavy metals. Common analytical techniques for soil and groundwater testing include conductivity, titrimetry, gravimetry, fluorimetry, atomic absorption spectroscopy (AAS), high-performance liquid chromatography (HPLC), gas chromatography, ICP-MS, LC-MS, and GC-MS.