Effects of Catchment Land Use on Nutrients and Heavy Metals Inflows into Maragua and Mathioya Wetlands in Murang’a County, Kenya

Wetland ecosystems in Murang’a County are diminishing due to increased catchment land use practices. Part of wetlands have been converted into farmlands where various agricultural activities are carried out while some parts have been converted into settlement points. Agricultural practices carried out along wetland ecosystems involve the use of excessive agrochemicals during crop production which later contribute to wetland pollution through nutrients and heavy metals inflows. This study aimed at assessing the effects of catchment land use on nutrient and heavy metals inflows into Maragua and Mathioya river basins in Murang’a County. Water samples were collected using the Grab technique, packed in plastic containers, kept in cool boxes, and transported to the research laboratory for analysis. Phosphate and nitrate concentrations were analyzed across different seasons, sampling stations, and sampling levels. During dry season, the mean phosphate concentration was 0.0259 ± 0.0051 mg/L with a standard deviation of 0.0124 mg/L. In wet conditions, the mean phosphate concentration increased to 0.1631 ± 0.1509 mg/L with a standard deviation of 0.3697 mg/L. For nitrate, the mean concentration during dry conditions was 9223.37 ± 2672.33 mg/L with a standard deviation of 6545.84 mg/L, and during wet conditions, it remained the same at 9223.37 ± 2008.17 mg/L with a standard deviation of 4919.00 mg/L.