Analysis of Lead-210 in Surface Water nearby a Phosphate Mining at Semi-arid Region in Santa Quitéria, Ceará State, Brazil

Abstract

Aims: To report the activity concentrations (AC) of 210Pb in surface waters in a semi-arid region, aiming to record these concentrations before the beginning of a Naturally Occurring Radioactive Material (NORM) mining operation, facilitating subsequent comparisons with the operational phase besides verifying the radioecological characteristics of this radionuclide and the potability of the water used for human consumption by the local population. Study Design: The water samples were collected in a six points grid associated to places of human consumption, aiming to verify their radioecological characteristics and radiological potability. Place and Duration of Study: The study site was a semi-arid region associated to a NORM phosphate deposit, between October 2009 and December 2011. No collection occurred in January and February 2010, accounting for 25 collections and 50 analyzes (soluble and particulate) per point. Methodology: 1 L of water, per point, was collected acidulated and filtered. The filtrate was considered as the soluble fraction and the retained part as the particulate fraction. The 210Pb was separated by coprecipitation and analyzed by total beta counts. Data were analyzed by univariate and multivariate statistical methods and the values found were compared with international potability standards. Results: The values found were within the international recommendations of ingestion of 210Pb in water (mean value of 0.05 Bq∙l-1 < recommended of 0.1 Bq∙l-1). Radionuclide radioecology proved to be complex. The total AC of 210Pb (sum of the soluble and particulate fractions) showed no difference between points, ranging from 0.05 Bq∙l-1 at point 01SQ to 0.10 Bq∙l-1 at point 04SQ. But when the AC of the fractions were analyzed, it could be verified that the AC of the particulate fraction were systematically higher than that of the soluble fraction. Conclusion: The analyzed water, in relation to the activity concentration of 210Pb, is considered potable and the particulate fraction has higher AC than the soluble fraction. The characterization of the water must be complemented when entering the operation of the phosphate mine to verify the radiological environmental impact assessment of the enterprise.