Enrichment and Bioavailability of Toxic Elements in Intensive Vegetable Production Areas1

Abstract

Vegetable cultivation stands out for intensive use of agricultural inputs due to high nutritional requirements of plants within a short period and their high susceptibility to pests and diseases. This study aimed to identify the main factors responsible for changes in pseudo-total and bioavailable contents of Cd, Cu, Cr, Mn, Ni, Pb, and Zn in soils under intensive vegetable cultivation. Soil samples were collected from 146 sites in Petrópolis (RJ), Brazil, in 2017. The samples were collected at a depth of 0-20 cm in family farm systems during vegetable production period. Pseudo-total contents of toxic elements were determined by the EPA 3050B method. Geochemical fractionation procedure was used based on the BCR method. Pollution indices were also calculated. In general, vegetable producing areas presented low contamination by Cu, Zn, Pb, Mn, and Ni, except for Cd, which showed severe contamination. In areas with the lowest slopes, most of the toxic elements showed increasing contents, reflecting relief influence. Overall, inadequate soil management, intensive application of phosphate, potassium, and organic fertilization, and relief were the most influencing parameters on the enrichment and bioavailability of toxic elements in the soil.