Reference values for potentially harmful elements in soils from Atlantic Rainforest, Brazil

Abstract

Soil formation processes and the parent rock lead to differences in potentially harmful elements (heavy metals) contents in soil and sediments distribution patterns. The Brazilian legislation demands that natural baseline values must be defined for each specific environment or each state in the country. In this work natural baseline values of potentially harmful elements (PHE) in soils from Parana's Coast Plain (Atlantic Rainforest) were established and correlations with soil properties were verified. The sampling points were defined by geological and soil maps information crossing. We performed soil fertility, texture and Fe oxides (crystalline and amorphous) analysis. Pseudo-total metal concentrations were obtained by microwave-assisted digestion using the EPA3051A method. There were positive correlations between PHE and clay in the soils. The pedogenetic Fe oxides had important role in the adsorption and maintenance of PHE in soil. Natural baseline values were higher in comparison with other states of Brazil and with other foreign studies. The increase in PHE content in the sandy soils of Coastal Plain was attributed to the heavy flow of vehicles for centuries towards the coast of Paraná state. The background PHE values for Parana's Coast plain from 75 percentiles, in mgkg−1, were: Ag (0,29); As (4,78); Ba (111,4); Cd (1,02); Co (<0.17); Cr (48,8); Cu (17,9); Mo (1,44); Ni (17,2); Pb (16,9); Sb (3,12); V (60,2); and Zn (52,5). Special attention should be given to Sb due to its lower critical environmental level. When confronted to other values we confirm the necessity to regional (inside a state) baseline reference values.