Características química, física e teores de elementos- traço em solos diferentes ambientes no Rio Grande do Norte

Abstract

The soils naturally have trace elements in varying concentrations, depending on the parental material which were formed, genesis processes, composition and proportion of the soil solid phase components, however the human activities can affect their concentration in the soil. The irrigation water, fertilizer application and use of pesticides can contribute to soil contamination with these elements, as well as sewage disposal and waste from industrial and residential. The problems caused by trace elements excess depend on the chemical forms and amount in which occur in soils. Although the soil total concentration not a good parameter for bioavailability predicting its determination aims at obtaining data on the accumulation of these elements over time mainly due agricultural practices. Recently the trace elements has raised interest because of the possibility of their to food chain transfer, since some agricultural inputs as lime and fertilizers used in agriculture be contamination source. In Rio Grande do Norte are few studies on the soils contaminated by trace elements. Thus, the work realized in 2010, evaluated the trace elements concentration in soil of the native forest (natural environment), agricultural and landfills or dumps in four Rio Grande do Norte cities and its correlation with the chemical and physical soil characteristics. For this purpose soil samples were collected before and after the rains period in three cities (Mossoró, Assú, Lajes and Natal) in three areas with different use. In each city and within the chosen environment three compost soil samples taken from depths of up to 20 cm, were analyzed for pH, Ca, Mg, Na, K and Al exchangeable, and P available. Were calculated the sum of bases (SB) and cation exchange capacity effective (CEC). In the physical characterization utilized the granulometry, bulk soil, particle density and calculated the soil total porosity (TP). The samples were analyzed for were cadmium (Cd), copper (Cu), manganese (Mn), nickel (Ni), lead (Pb) and zinc (Zn) by 3051A method of the Environmental Protection Agency (USEPA). The quantification of the trace elements content was performed by atomic absorption spectroscopy (AAS) with air-acetylene flame. The results were analyzed using descriptive statistics, simple linear correlation and multivariate statistics (principal component analysis and factorial). In general the mean trace elements concentration in the soil followed the order: natural range < agricultural soil < dump and their mean concentrations in the areas of landfill were higher than the CETESB's benchmarks