Measurement modelling and mapping of arsenic bioaccessibility in Northampton, United Kingdom

The human ingestion bioaccessibility of As was measured on 50 representative samples of soils selected from a 281-soil-sample geochemical survey of Northampton. The major and trace element content, pH and near infrared (NIR) spectra of the 281 soils were determined. A multiple linear regression (MLR) model using total As, major element composition and pH identified total As, pH and P to be the significant predictor variables for bioaccessible As (R2 = 0.72, median standard error of prediction = 1.5 mg kg(-1) bioaccessible As). When spectral components (SC) derived from chemometric analysis of the NIR spectra were also included in the MLR, total As, pH, Mg and two NIR spectral components were found to be significant predictor variables (R2 = 0.84, median standard error of prediction = 1.2 mg kg(-1) bioaccessible As). Correlation analysis of the SC with major element data suggested that the two NIR SC in the second model were related to different forms of Fe oxides in the soil. When plotted over a geological map of Northampton interpolated predictions of bioaccessible As showed clear geological control. The median total As concentration of the soils in Northampton was 30.2 mg kg(-1) and the median bioaccessible As was 3.0 mg kg(-1).