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

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 δ¹³C_DIC as a tracer is limited to subsurface environment. Further, nitrogen isotopes δ¹⁵N-NH₄ and δ¹⁵N-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.

GRAPHICAL ABSTRACT

KEYWORDS:

• Isotopes
• environmental tracer
• fractionation mechanism
• leachate

Acknowledgement

This work was supported through a project titled ‘Leachate Transport Modelling for Gazipur landfill site and suggesting Ameliorative measures’ (Grant Ref: SP-28/2019–20/PDS-19) under National Hydrology Project.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

All data used during the study are available from the corresponding author by request.

Author contribution

Anjali Bhagwat: Data curation, Formal analysis, Investigation, Methodology, Writing – Original draft, Writing – Review & editing.

Chandra Shekhar Prasad Ojha: Supervising, Review and editing.

Sudhir Kumar: Supervising, Review and editing.

Bhisam Kumar: Supervising, Review and editing.

Additional information

Notes on contributors

Anjali Bhagwat

Ms Anjali Bhagwat, Scientist'C', Groundwater Hydrology Division of NIH Roorkee. Her research focuses on Groundwater flow and contaminant Transport Modelling, Contaminant Hydrology, Isotope Hydrology Micro-plastic assessment & Hydrological Modelling.

Chandra Shekhar Prasad Ojha

Prof. Chandra Shekhar Prasad Ojha, Professor at Department of Civil Engineering, IIT Roorkee. He has more than 40 years of experience. His field of Interest is Hydraulics, Hydrology and Environmental Engineering. He has More than 100 research papers in international Journals.

Sudhir Kumar

Dr Sudhir Kumar, Former Director and Scientist, NIH Roorkee. He is an expert Hydrogeologist and headed the Isotope Laboratory at NIH Roorkee for more than 15 years. His main area of interest is Groundwater Flow modelling.

Bhishm Kumar

Dr Bhishm Kumar, Former Prof Staff, IAEA, Vienna, Austria & Advisor (IH), Former Sr Scientist & Head, NIH Roorkee, His expertise lies in the Application of Isotopes in Hydrology and Water Resources.