Seasonality of environmental health risks and soil pollution from an unsanitary landfill in Nigeria: Implications for water security, agriculture, and climate adaptation

• Leachate from unlined dumpsites poses a potential threat to the environment. • The leachate from the dumpsites contains potentially toxic elements, which can contaminate the soil infiltrate and cause pollution. • The use of unsanitary dumpsites should be avoided to prevent threat to the environment. The increasing global waste crisis, coupled with inadequate landfill management in developing regions, poses significant environmental and public health risks, especially in areas with seasonal climate variations. While previous studies examined landfill contamination, limited research has investigated the seasonal dynamics of soil-environmental health risks and their implications for regional development and climate resilience. This study adopted a multi-parameter approach to assess the seasonal variations in contamination patterns and their impacts on environmental and human health, water security, and agricultural sustainability in Awka, Nigeria. It examined the implications of pollution from an unsanitary landfill, revealing substantial seasonal variations in soil contamination patterns. Analyses of potentially toxic elements (PTEs) showed that cadmium levels (1.23-4.42 ppm) exceeded WHO criteria, with higher levels reported in the wet season compared to the dry season. The pollution load indices indicated moderate to heavy pollution in study samples (1.69-2.54) and moderate pollution in control samples (1.06-1.69). Health risk assessments revealed high cancer risks for children through ingestion pathways (HI > 10 -4 ), while adults had lower risks (HI ∼ 10 -5 ). The research unveiled critical implications for regional water security, agricultural productivity, sustainable landfill construction, and climate adaptation strategies. It also demonstrated that leachate migration patterns intensified during wet seasons, threatening groundwater resources. The findings illuminated the interconnections between waste management practices and climate resilience while providing a practical framework for assessing the seasonal variations in environmental health risks. The evidence-based recommendations for sustainable landfill management hinted on the need for seasonal monitoring and climate-adaptive waste management strategies in similar geological/environmental settings.