Tracing solid waste leachate in groundwater using δ13 C from dissolved inorganic carbon

Contaminants of Emerging Concern as novel groundwater tracers for delineating wastewater impacts in urban and peri-urban areas

Management and treatment of environmental impacts from wastewater treatment plants (WWTPs) is a major, worldwide, sustainability challenge. One issue associated with WWTP operation is the potential for groundwater contamination via leaking or infiltration of wastewater, particularly with inorganic nutrients (ammonia and nitrate) as well as persistent organic compounds. Despite the potential for such contamination to create environmental and health risks, conventional methods, such as the assessment of major ions, nutrients, bacteriological indicators and conventional tracers (such as stable and radiogenic isotopes) are often unable to provide accurate delineation of multiple potential sources of contamination. This is particularly important for WWTPs which often occur in urban, peri-urban or intensively farmed agricultural areas where multiple potential sources (such as livestock, fertilisers, wastewater irrigation, and domestic septic systems) may contribute similar contaminants. This review explores the applicability of promising novel groundwater tracers, such as Contaminants of Emerging Concern (CECs) and isotopic tracers, which can be used in conjunction with conventional tracers (i.e. 'co-tracers') to provide a more definitive assessment of contaminant sources, plume delineation and even (potentially) indicating the age of contamination (e.g., recent vs. legacy). The suitability of the novel groundwater tracers is evaluated according to four key criteria: (i). sufficient presence in raw wastewater and/or treated effluents; (ii) diagnostic of WWTP impacts as opposed to other potential off-site contamination sources; (iii) persistence in the subsurface environment; and (iv) amenable to rapid and sensitive analysis. Further analysis of various classes of CECs along with improved detection limits associated with improvements in analytical methodologies should allow for future application of promising groundwater tracers, providing WWTP operators and regulatory authorities a more definitive toolbox with which to assess groundwater contamination associated with site operations. These include: persistent pharmaceuticals and personal care products (carbamazepine, crotamiton, primidone, atenolol and sulfamethoxazole), artificial sweeteners (acesulfame, sucralose, saccharin and cyclamate) and potentially, certain pesticides (atrazine and simazine).

Environmental monitoring of a landfill area through the application of carbon stable isotopes, chemical parameters and multivariate analysis

Leachate produced during an organic matter decomposition process has a complex composition and can cause contamination of surface and groundwaters adjacent to a landfill area. The monitoring of these areas is extremely important for the characterization of the leachate produced and to avoid or mitigate environmental damages. Thus, the present study has the objective of monitoring the area of a Brazilian landfill using conventional parameters (dissolved metals and anions in water) and alternative, stable carbon isotopes parameters (δ¹³C of dissolved organic and inorganic carbons in water) in addition to multivariate analysis techniques. The use of conventional and alternative parameters together with multivariate analysis showed that cells of the residues are at different phases of stabilization of the organic matter and probably already at C3 of the methanogenic phase of decomposition. In addition, the data showed that organic matter stabilization ponds present in the landfill are efficient and improve the quality of the leachate. Enrichment of the heavy ¹³C isotope in both surface and groundwater suggested contamination in two sampling sites.

Identification of groundwater contamination zone around a reclaimed landfill using carbon isotopes

Chemical and isotopic analyses of groundwater from piezometers localized around a reclaimed landfill were performed in order to identify the boundaries of groundwater contamination zone. Spatial distribution of dissolved inorganic carbon (DIC) concentration and stable carbon isotopes in the groundwater was used to distinguish the piezometers localized within the contaminated aquifer. Background groundwater was characterized by low DIC concentration (from 1.8 to 5.0 mmol/L) and negative values of δ¹³C_DIC (from -20.6‰ to -12.4‰). Higher DIC concentrations (from 6.0 to 12.5 mmol/L) and higher values of δ¹³C_DIC (from -10.9 to +3.6‰) were determined in groundwater contaminated by landfill leachate. The study confirmed that δ¹³C_DIC value in the groundwater was a useful tracer in determining the extent of the contamination zone around the landfill. In general, upgradient from the landfill, carbon isotopic composition of groundwater depended on natural sources of carbon and δ¹³C_DIC values were negative. Downgradient from the landfill, where groundwater was contaminated by the landfill leachate, δ¹³C_DIC values were higher, sometimes even positive.