Spectrophotometric Determination of Nitrate and Phosphate Levels in Surface Waters of Lake Chad Basin Communities, Borno State

Nutrient enrichment of surface water through agricultural runoff and domestic wastewater disposal is a growing concern for freshwater ecosystems, particularly in ecologically sensitive regions such as the Lake Chad Basin. This study determines nitrate and phosphate concentrations in surface water samples collected from rivers, ponds, and irrigation canals serving communities in Borno State, North East Nigeria. Sampling was conducted across two seasons: the dry and wet seasons, to capture seasonal variations in nutrient loading. Nitrate was quantified using the cadmium reduction method, while phosphate was determined by the ascorbic acid method, both measured spectrophotometrically. Field parameters including pH, temperature, dissolved oxygen, and conductivity were recorded in situ. Results reveal that nitrate levels were considerably higher during the wet season, consistent with increased agricultural runoff from irrigated farmlands. Phosphate concentrations exceeded WHO surface water guidelines at three sampling points adjacent to communities practising intensive vegetable cultivation. Dissolved oxygen levels at the most nutrient-enriched sites were below the threshold recommended for healthy aquatic ecosystems, suggesting early-stage eutrophication. The study recommends the adoption of buffer strips along water bodies, regulated use of phosphate-based fertilisers, and community sensitisation on the risks of nutrient pollution to aquatic biodiversity and human health. Keywords: nitrate, phosphate, Lake Chad Basin, eutrophication, surface water