Spatial distribution and ecological risk of heavy metals in agricultural surface soil around brick kilns, Natore, Bangladesh.

Spatially explicit evidence on soil metal enrichment is scarce for the clustered, small-scale brick kilns that dominate rural Bangladesh. This study determined the concentrations, spatial distribution and ecological risk of chromium (Cr), lead (Pb) and cadmium (Cd) in agricultural surface soil around three closely spaced brick kilns at Lalpur, Natore. Twenty-two surface soil samples (0-10 cm) were collected at nominal distances of 100 m and 200 m from the chimneys in four directions during the 2024 burning season, digested in nitric-perchloric acid and analysed by flame atomic absorption spectrometry. Spatial patterns were visualised by inverse distance weighting and interpreted against firing-season wind data; contamination was assessed using four indices against two geochemical baselines. Cr ranged from 21.62 to 52.18 mg/kg and Pb from 35.00 to 47.72 mg/kg, while Cd fell below the detection limit of 0.012 mg/kg at 21 of 22 points, with a single detection of 2.35 mg/kg. Pb exceeded the regional reference value of 23 mg/kg at every point by 52-107%, whereas mean Cr (33.01 mg/kg) remained below its reference value of 41 mg/kg. Distance from the chimney correlated weakly and non-significantly with both metals; elevated concentrations occurred in sectors not predicted by the pre-monsoon wind field. Total ecological risk was low throughout. These findings establish a spatial association between kiln proximity and soil metal enrichment without attributing it to kiln emissions, and support annual Pb monitoring within 200 m of kilns, on-site containment of fuel and ash, and a paired control-impact campaign.