Holocene Records of Human Driven Geological Impacts in a Ramsar Wetland of India

Abstract

The present study evaluated the extent of accumulation of heavy/trace metals in the recent sediments of Ashtamudi Wetland System (AWS), a Ramsar Site located in the Southern State of India, Kerala; using Contamination Factor (CF), Pollution Load Index (PLI) and Geo-accumulation Index (Igeo) in 4 sub-environments of AWS; viz: Ashtamudi Main Kayal, ChavaraKayal, Kureepuzha- KandachiraKayals and Kumbalathu- KanjirakottuKayals for monsoon and non-monsoon seasons. Spatial distribution diagrams of heavy/trace metals for monsoon and non-monsoon seasons were also prepared in GIS in order to assess the spatial and temporal variation of pollution in the entire Wetland System. Comparing the data with the world shale averages for the concerned elements, it is observed that Cr, Fe, Ni and Cu were in higher concentration, indicating high befouling rate. The ChavaraKayaland Kumbalath and KanjirakottuKayals were found highly polluted with heavy metals compared to other sub-environments. Geo-accumulation index (Igeo)values of most of the elements (Cr, Fe, Co, Cu etc) were in classes above zero indicating high degree ofpollution. However, Cobalt in non-monsoon season, Nickel and Zinc in most of the stations fall under zero class of Igeo, probably due to the predominance of lithogenic flux. Zero class of pollutants (Ni and Co during non-monsoon season and Zn) suggests the dilution and dispersion of elements in the Wetland System. A decadal comparative analysis of the accumulation of heavy/trace metals shows the dramatic increase in the heavy metal deposition in the Wetland System which shed light on the human driven geo-environmental impacts in the AWS and the urgent needs of sustainable conservation measures.