Assessing the Geochemical Fractionation of Phosphorous and Heavy metal in Surface Sediments of Mangroves and assertaining its Ecological Risk, Gulf of Kachchh, Second largest mangrove cover of India.

Worldwide rapid industrial growth is leading to heavy urbanization in the coastal areas. Therefore coastal areas are becoming critically contaminated with heavy metal and nutrients, which is serious environmental concern as they are bio-accumulative in nature. Due to its non-biodegradable in nature trace metal is toxic to biotic communities and environment (Gong et al., 2020, Parul and Rina, 2021). The present study has been carried out in India’s second largest mangrove cover in the world. The study area is witnessing rapid urbanization as the area is inhabiting the Asia’s largest fertilizer refinery IFCO along with multiple seaports, with large number of chemical and petroleum industries, and the region is the prime gateway of trade and commerce. Besides this extensive salt producing units with extensive agricultural and aquaculture activities are present which are posing severe threat to the mangroves. The gulf is also inhabiting the complex geomorphological setup such as alluvial plains, tidal mudflats, lagoons creek and stabilized dune area (Deshraj et al. 2012). Construction of saltpan/aquaculture is deteriorating the mangroves health, impairing productivity (Jigar et al, 2022). Phosphorus (P), is one of the important macronutrients that governs the primary productivity and it affects both the terrestrial and marine biogeochemical cycling.  P is released in dissolved or suspended forms, holding both inorganic and organic forms, which undergo a continuous transformation. Knowledge of P speciation in sedimentary environments is crucial to understand the P cycling, bioavailability, and the mechanism of their release, which will help to assess the ecological risk associated with P enrichment. Along with Phosphorous, metal fractionation study is also important to determination of bioavailability and mobility of trace metals in geochemical fractions and ecological risk to the ecosystem. Results suggested that Total sedimentary P was found beyond the global limit and consists of inorganic-P fraction predominantly. PEI values suggest higher P loading in sediment which leads to higher eutrophication risk.

Metal fraction study suggested, a considerable variation in the speciation pattern of trace metals. In the study area, highest proportion of trace elements was associated with the residual phase (F4), which manifested that metals bounded with the alumino-silicate mineral and detritus matter in sediments was highest. Therefore, Present study would be helpful to the policymakers in the view of the current Land use-land cover change and contamination level in Gulf of Kachchh, mangroves for implementation of protection strategies for this precious natural resources.

Keywords:

Phosphorus Fractionation, Metal Fractionation, Sequential extraction, Mangroves Sediment, Ecological risk, Gulf of Kachchh, India