Use of environmental isotopes in leachate studies through multiple isotopic analysis – a review

Abstract

ABSTRACT Contamination of water resources by leachates emanating from different types of landfills and waste heaps is a serious concern. Proper management is possible, only after source identification. Statistical methods such as principal component analysis, Pearson correlation coefficients and Hierarchical cluster analysis can indicate the sources of pollutants, but the quantification of contributions from each of the sources is not possible. Thus tracing the movement of leachate plumes through environmental isotopes (stable and radioactive) is gaining importance. Though the application of isotopes for source identification is an accepted practice, the types and sources of pollution can be traced, and the various advantages and disadvantages associated with the choice of isotopes are not well documented. Thus the review first attempts to understand the possible use of conventional and potential isotopes under different waste composition and try to summarize the isotopic signature of isotopes in different sources and their variability to understand their applicability as a tracer of pollution plume. This study shows that the applicability of δ13CDIC as a tracer is limited to subsurface environment. Further, nitrogen isotopes δ15 N-NH4 and δ15 N-NO3 carry the signature of shallow aquifer and thus cannot be applied as tracer for shallow aquifer. Isotopes of Boron, Strontium, Tritium, Lead, Deuterium, Sulphur, Lithium and Cadmium are useful in tracing the leachate plume movement both in surface and groundwater. The applicability of Boron, Sulphur and Lithium are limited by adsorption. Strontium, Tritium, Lead and Cadmium show very low fractionation and thus become potential candidate to be used as tracers.