Quality reference values for heavy metals in soils of Rio Grande do Norte, BrazilIndustrial development and population growth have increased heavy metal concentrations in soils and impacted soil quality. In this scenario, environmental protection agencies have been concerned with establishing heavy metal quality reference values (QRV) that may identify contaminated sites. The study was carried out to provide soil reference values for the metals Ag, Ba, Cd, Co, Cr, Cu, Ni, Pb, Sb, V, and Zn in soils of the State of Rio Grande do Norte according to Brazilian legislation. The study analyzed 416 soil samples taken from native forest or areas with minimal human interference. These samples were digested by the USEPA 3051A method, and the metals were measured by Inductively Coupled Plasma - Optic Emission Spectrometry (ICP-OES) or flame atomic absorption (FAA). The results showed that regional geochemical surveys are essential in establishing QRVs for heavy metals. For example, the QRV for the soils of Rio Grande do Norte were more restrictive than the QRVs adopted for other Brazilian states. Confirmation factorial analysis of the data was useful for obtaining more reliable QRVs and showed that for the state these values could be obtained from two replicates only per collection location. Thus, advance planning is essential in distribution of sampling locations so that the diverse geomorphological, pedological, and geological compartments of the state are represented.
trace elements; soil contamination; soil pollution; environmental monitoring
