Arsenic content and distribution in agricultural soils of Vojvodina Province, Serbia

Arsenic (As) is metalloid designated as a pollutant in the environment due to its harmful effects on biota. Sources of arsenic soil contamination originate from both indigenous and anthropogenic inputs, including atmospheric deposition (mining, industry, dumpsites). In addition, As has been used in agriculture as a component of different agrochemicals. Contamination of groundwater with arsenic is a global issue. Arsenic in drinking water can affect human health; it is considered as one of the most prominent environmental causes of cancer mortality in the world. The content and retention of As in soils, as well as the other heavy metals, is highly dependent on the physicochemical properties of the soil. Vojvodina Province in the northern part of Serbia represents its most important agricultural area. The aim of this study was to determine the content and distribution of As in agricultural soils, its spatial distribution in different geomorphological units and soil types of Vojvodina Province, and to establish permanent monitoring. A grid superimposed on Vojvodina soil by means of a GIS tool has divided study area into 4 × 4 km units, each representing an area of 16 km2. Total number of 1,370 bulked soil samples (0-30 cm depth) were taken from agricultural land. The samples were analysed for pseudototal content of AsT (after MW digesting the soil in ccHNO3 and H2O2) and available contents of AsEDTA (EDTA extraction). The concentrations of As were determined by ICP-OES. Basic soil properties were determined according to standard methods at the Laboratory for Soil and Agroecology of the Institute of Field and Vegetable Crops, Novi Sad, accredited according to the standard ISO/IEC 17025 (2005). The software used for the mapping and spatial analysis was ESRI ArcGIS Geostatistical Analyst 10. All statistical analyses were performed using the data analysis software system Statistica for Windows, version 13.2 (Dell 2015). The obtained results of AsT were within interval 1.0–31.4 mg kg-1. The average concentration of As was 8.4 and 0.4, with median 8.3 and 0.3 mg kg-1 for pseudototal and available content, respectively. Only four samples were above 25 mg kg-1 for AsT, which is the national legislative threshold. These samples belong to the District of Srem, South Banat and two samples are from the South Bačka District. It was found that AsT content is negatively correlated with pH value and CaCO3 and positively correlated with organic matter contents in soil. The effect of different soil particle size on availability of As was proven; availability decreases with higher proportion of clay and slit. As spatial distribution indicated, the majority of Vojvodina Province area has geochemical origin of As. Based on As concertation along geomorphological units, AsT is higher on mountains (10.4) and lower on the sandy area (5.6 mg kg-1) with statistical difference among the other units. Oppositely, AsEDTA is higher on sandy area (0.6) and lower on the mountains (0.3 mg kg-1), which proves effect of organic matter and clay on As availability. Average values of AsT concentrations according to the soil types coincides with main geomorphological units where soils have been formatted. AsT is higher in cambisol (10.9) and lower in arenosol (4.8 mg kg-1). Average values of As in chernozem, most frequent soil type in Vojvodina, was 8.6 and 0.4 mg kg-1 for pseudototal and available content, respectively. The obtained results show that measured levels of As in the soil are not limiting factors for safe food production in Vojvodina. The results emphasize the importance of knowing the spatial determinants of geomorphological units and soil types in establishing a permanent monitoring.