Assessment of Heavy Metal Contamination in Urban River Sediments and Its Ecological Impacts

Thesis Abstract

Rapid urbanization has intensified the influx of anthropogenic pollutants into river systems, leading to heightened concerns over heavy metal contamination in river sediments and their subsequent ecological impacts. This study aims to comprehensively assess the levels, sources, and ecological consequences of heavy metals in sediments from the River Green in Riverton City, with the objective of informing sustainable urban water management practices. Specifically, the research seeks to quantify concentrations of lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), and zinc (Zn) in sediment samples, identify pollution sources through spatial analysis, evaluate ecological risks using sediment quality guidelines, and examine potential biological effects on benthic macroinvertebrate communities. Employing a cross-sectional research design, the study involves collecting sediment samples from twenty strategically selected sites along River Green, representing upstream, midstream, and downstream locations, during the dry season to minimize seasonal variability. A total of 60 sediment samples (three per site) are gathered using stainless steel hand augers, ensuring contamination-free collection. Analytical quantification of heavy metals is performed via Inductively Coupled Plasma Mass Spectrometry (ICP-MS), calibrated with certified reference materials to ensure accuracy and precision. The sources of pollution are traced using Geographic Information Systems (GIS) to map spatial distribution patterns and multivariate statistical methods such as Principal Component Analysis (PCA) to distinguish between natural and anthropogenic contributions. Sediment quality assessments are conducted by comparing measured metal concentrations against baseline levels established from pristine reference sites, with ecological risk evaluated using the Geoaccumulation Index (Igeo) and Potential Ecological Risk Index (PERI). Benthic macroinvertebrate diversity and abundance are surveyed at the same sites to investigate biological impacts, utilizing standardized kick-net sampling and subsequent identification to taxonomic levels. Data analysis encompasses descriptive statistics for concentration profiles, inferential statistics including analysis of variance (ANOVA) to detect significant spatial differences, and multiple regression models to explore relationships between sediment contamination levels and macroinvertebrate indices. The study also investigates correlations between heavy metal concentrations and ecological health indicators via Spearman’s rank correlation analysis. Expected findings suggest elevated concentrations of heavy metals in downstream sediments, with Pb and Hg levels exceeding permissible limits set by environmental agencies, indicating significant anthropogenic influence primarily from industrial discharges, vehicular emissions, and wastewater effluents. Spatial analysis is anticipated to reveal pollution hotspots correlating with industrial zones and densely populated neighborhoods. Ecological assessments are projected to demonstrate a decline in macroinvertebrate diversity and abundance with increasing sediment contamination, suggesting adverse biological effects. The results are expected to contribute novel insights into the spatial distribution of contaminants, their sources, and ecological implications within urban river systems. This research advances knowledge by integrating chemical, spatial, and ecological analyses to establish a comprehensive assessment framework, filling existing gaps in regional data and contributing to the development of effective pollution mitigation strategies. The findings are intended to inform policymakers and environmental managers on targeted remediation efforts and sustainable urban planning, emphasizing the importance of pollution control at identified hotspots. In conclusion, the study advocates for continuous monitoring of sediment quality, implementation of stricter regulatory standards on industrial discharges, and community engagement to promote environmental stewardship. Recommendations include adopting sediment remediation techniques such as dredging and stabilization and establishing regular biological monitoring to safeguard ecological integrity in urban riverine environments. Further research is suggested to explore long-term trends and the effectiveness of implemented pollution control measures.