Exploring the Relationship Between Land Use and Pesticide Contamination in a Tropical Rural Catchment: A Case Study of River Chanchaga

Abstract

Freshwater ecosystems are vulnerable to various land uses, resulting in concern for aquatic organisms and humans. Understanding the occurrence of pesticide contamination is necessary to safeguard aquatic biodiversity and human health. Against this background, our study aimed to assess the effect of various land uses on pesticide contamination by evaluating three selected sites according to land use class: a control site (CON), an agricultural area (S1), and an urban area (S2). Various classes of land use around the catchment were determined using ArcGIS 10.8 GIS software, while analysis of pesticide residues was carried out using the liquid-liquid extraction method, followed by gas chromatography-mass spectrometry (GC/MS). A total of 10 herbicides and 12 insecticides were recorded in each sampled sub-catchment, with a statistically significant difference across the sampled sub-catchment. Sampled sites located in agricultural and urban areas recorded higher concentrations of pesticide residues compared to sites located in natural areas, with less anthropogenic influence, reflecting differences in pesticide usage. Redundancy analysis (RDA) revealed crops and urbanized land use were the main sources of pesticide contamination in the water, as pesticides are predominantly used on farms and in various households. Their presence in the water may have potentially detrimental effects on aquatic biodiversity because pesticides have been associated with various health issues. It was evident that all sampled sub-catchments had pesticide concentrations exceeding the WHO permissible limit for human consumption. Implementing alternative methods for managing pests and weeds without relying on pesticides is crucial for sustainable agriculture and environmental preservation.