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Assessing the impacts of land use and land cover on occurrence, spatial distribution of microplastics and heavy metals in an agricultural watershed, Tadepalligudem, Andhra Pradesh, India
Summary
Researchers mapped the occurrence and spatial distribution of microplastics and heavy metals in agricultural runoff from a watershed in Andhra Pradesh, India. They found an average of 41.7 microplastic items per liter, dominated by polypropylene and polyethylene fibers, with heavy metal concentrations of cadmium, arsenic, chromium, and lead posing varying levels of health risk. The study highlights that land use patterns significantly influence both microplastic and heavy metal contamination in agricultural water systems.
The presence of microplastics (MPs) and heavy metals (HMs) in agricultural runoff is a significant concern and are found to vary with land use and land cover (LULC). The occurrence of these pollutants in aquatic environments, even at minimum concentrations, can pose several ecological and health risks. To mitigate and manage these MPs and HM, there is a need to quantify their occurrence as well as their spatial distribution, as it enables in capturing accumulation patterns and transport pathways. Therefore, in this study, the occurrence and spatial distribution of MPs and five HMs are quantified from 15 grab samples collected from agriculture runoff within a watershed in Tadepalligudem, India, which drains into Kolleru Lake. From the results, the mean concentration of MPs across the sampling sites is found to be 41.7 items/L, with fiber as the predominant MPs shape with polypropylene and polyethylene identified as the dominant polymer types. Among the five quantified HMs, except for mercury (Hg), all four HMs-cadmium (Cd), arsenic (As), chromium (Cr), and lead (Pb)-are observed to be within the maximum permissible limits of surface waters. Along with abundance, the risk associated with both MPs and HM is assessed, which showed that compared to the MPs pollution load, the polymer type is found to pose a greater ecological risk. While, the carcinogenic risks associated with Cd, As, Cr, and Pb varied from a medium to a very high level. Additionally, the study also investigated the relationship between the LULC, MPs, and HMs using principal component analysis and Spearman correlation, where a positive correlation is observed between MPs, Hg, and cropland class, with a p-value less than 0.05. This assessment of MPs and HMs, their spatial distribution, and links to LULC supports effective watershed-scale management strategies and highlights potential impacts on downstream ecosystems.