A socio-technical hazard analysis of Trace Organic Contaminants in peri-urban shallow groundwater in Uganda

Abstract

Trace organic contaminants (TrOCs) are increasingly reported in the environment, with potential adverse ecological effects. This study aimed to enhance the understanding of socio-technical factors influencing the distribution of TrOCs and the associated risks in peri-urban shallow groundwater in Uganda. Specifically, to; i) analyse the influence of socio-technical management frameworks, ii) assess the spatial and seasonal variability of TrOCs, iii) investigate the influence of on-site sanitation practices (OSS) on TrOCs and the associated risks, and iv) explore the influence of socio-institutional factors. The study adopted an exploratory embedded case study design, focusing on Bwaise and Wobulenzi. Mixed methods were used, including critical literature review, laboratory analysis (using high-performance liquid and gas chromatography coupled with triple quadrupole mass spectrometry (LC/MS/MS and GC/MS/MS)), key informant interviews and transition arenas. The findings showed that integrated water resources management lead to improved integrative approaches like Water Safety Plans (WSPs), but has had a limited impact on mitigating groundwater contamination. Antibiotics, pesticides and hydrocarbons were detected in both Bwaise and Wobulenzi. Ampicillin was the most frequently detected antibiotic and the total antibiotic concentrations were up to 3,700 ng/L. Antibiotics also showed significant statistical associations with physico-chemical and microbial parameters associated with OSS practices (E.coli, nitrates, chlorides and sodium). Using the risk quotient, antibiotics presented a high risk for antibiotic resistance at 65% of the sources in Bwaise (dry season). Pesticides were detected, predominantly in Wobulenzi, attributed to agricultural land-use, exceeding the European Commission guideline (500 ng/L) at 75% of the sources (wet season). Cypermethrin and metalaxyl were most frequent, with total pesticide concentrations of up to 2,400 ng/L. Hydrocarbons were at low concentrations to cause adverse health impacts (up to total concentration of 2,500 ng/L). The key socio-institutional drivers of groundwater contamination were; land-use management, user attributes, governance, infrastructure management, groundwater valuation, and the operating environment. These findings imply that peri-urban communities are exposed to health risks from residual antibiotics and pesticides, attributed to OSS and agricultural practices, respectively. The study recommends improved monitoring and regulation of TrOCs, OSS and agricultural practices through WSPs integrating hydrogeological and socio-institutional aspects.