Watershed-scale assessment of background concentrations and guidance values for heavy metals in soils from a semiarid and coastal zone of Brazil

Abstract

Determining heavy metal background concentrations in soils is fundamental in order to support the monitoring of potentially contaminated areas. This is particularly important to areas submitted to high environmental impact where an intensive and local monitoring is required. To this end, the aim of this study was to establish background concentrations and quality reference values (QRVs) for the heavy metals Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn, As, and Hg in an environmentally impacted watershed from Brazil. Geochemical associations among Fe, Mn, and trace elements were also assessed to provide an alternative tool for establishing background concentrations. A total of one hundred and four samples comprised twenty-six composite soil samples from areas of native forest or minimal anthropic influence. Samples were digested (USEPA method 3051A), and the metals were determined by ICP-OES, except for As and Hg measured by atomic absorption spectrophotometer. Background concentrations of heavy metals in soils had the following decreasing order: Fe > Mn > Zn > Cr > Pb > Ni > Cu > As > Cd > Hg. These values were usually lower than those observed in the international and national literature. The QRVs for Ipojuca watershed followed the order (mg kg(-1)) Fe (13,020.40) > Mn (91.80) > Zn (30.12) > Cr (15.00) > Pb (13.12) > Cu (3.53) > Ni (3.30) > As (0.51) > Cd (0.08) > Hg (0.04). Significant correlation among Fe, Mn, and heavy metals shows that solubilization by the method 3051A provides a reasonable estimate for predicting background concentrations for Cd, Cr, and Cu as well as Zn, Cr, Cu, and Ni.

Pollution characteristics and ecological risk assessment of heavy metals in paddy fields of Fujian province, China

“…This result showed a similar pattern to that of Du et al, which found that 57.5% of soil samples in paddy field of Hunan province exceed the allowable limit specified by the china soil environmental quality standards 18 . According to the studies that are mentioned above 19 , 20 , 23 , 28 , the agricultural soil is mainly contaminated by Cd, Cu, Pb and Zn to various degrees in southern China. Meanwhile, compared with the pollution survey in the Yangtze river delta and the Pearl river delta 1 , 17 – 20 , 26 , 35 , we found that Fujian province contains a low level of heavy metal pollution, which is mainly due to the low degree of industrialization and the long-term development of the green economy in the region, such as construction of an ecological province in 2000.…”

“…For various heavy metals measurements, the cadmium (Cd), chromium (Cr), lead (Pb), arsenic (As), copper (Cu), nickel (Ni) and cobalt (Co) were determined in this study. To measure the concentration of metals, 0.5 g soils from each sample were digested with a mixture of concentrated HCl-HNO 3 -HF-HClO 4 on a hot plate 15,28 . First, a soil sample (0.5 g) was weighed and digested with 5 ml HCl on an electric hot plate at 190 °C until the solution was reduced to 3 ml.…”

Heavy metal concentrations and ecological risk assessment of the suspended sediments of a multi-contaminated Brazilian watershed

“…Heavy metal background values for the watershed soils were determined in areas of native vegetation or minimal anthropic influence (Silva, Nascimento, Cantalice, Silva, & Cruz, 2015). Aliquots (0.5 g each) of the soil and suspended sediment samples were ground and passed through a 0.3-mm-mesh stainless-steel sieve (ABNT No.…”

“…Contamination in the suspended sediment was assessed by the enrichment factor (EF) and compared with the SQGs. As background values, we used four composite uncontaminated soil samples from each cross section (Silva et al, 2015). To discriminate between the natural and anthropogenic sources of heavy metals in the suspended sediments, the EF was calculated as: EF = metal/Fe sample / (metal/Fe) background (1) The EF values were interpreted according to Sakan, Djordjevic, Manojlovic, and Predrag (2009).…”

Soil contamination by heavy metals in vineyard of a semiarid region: An approach using multivariate analysis

“…QRVs apparently overestimate the EF values of Pb, both on the surface and on the subsurface (Table 2). Silva et al (2015) highlight that despite the extreme importance of QRVs established for the state of Pernambuco, they cannot be adopted without a prior evaluation of their representativeness for specific conditions. It is also noteworthy that, unlike Zn, which showed almost similar values at both depths, Cu presented higher enrichment factor on the surface, indicating low mobility, particularly by the strong interaction with the soil organic matter (Nascimento and Fontes, 2004;Komárek et al, 2008).…”