Residual effect of Cd in oxisols cultivated with lettuce

Abstract

The Environmental Agency of the State of Sao Paulo - CETESB, in 2005, adopted guideline values for heavy metals in soils. However, studies seeking to validate these guideline values are still rare and incipient for cadmium (Cd). In this context, the objective of this study is to generate subsidies to reevaluate the guideline values for Cd in the soils, suggested by CETESB, using lettuce plants. The experiment will be conducted under greenhouse conditions. The plants will be cultivated in pots filled with 3 dm-3 of two Oxisols, with contrasting chemical and physical characteristics. The soils were previously contaminated with Cd and grown with rice plants. The treatments consisted of: 0,0; 0,5 (quality value); 1,3 (prevention value); 3,0 (intervention value) and 6,0 mg dm-3 rates of Cd, based on the guideline values established by CETESB. Thus, the lettuce plants will be carried out in the same soils, order to evaluate the residual effect of Cd in these soils. The experimental design will be in randomized complete blocks in a factorial scheme 5 x 2, with three replications. The number of leaves, fresh and dry matter, Cd concentration and accumulation in the roots and leaves, nutritional status, chlorophyll and flavonol content, NBI (Nitrogen Balance Index) in the leaves and available concentration of Cd in the soils before planting by the extractors DTPA, CaCl2 and Mehlich-1. Data will be submitted to analysis of variance and polynomial regression, using the SAS system of analysis.(AU)