Casca de Arroz como Biossorvente de Glifosato em Áreas de Plantio de Arroz Irrigado – Resultados Preliminares

Abstract

In Rio Grande do Sul, as one of the largest producers and the largest processor of national rice, 22 chemical products of different toxicological classes are available and recommended for the control of weeds in rice cultivation under the irrigated system. For this, glyphosate has been used, which is a post-emergence herbicide used after the emergence of weeds in the crop. In this case, in addition to the environmental concern regarding the use of pesticides, there is also the issue of the generation of residues from agro-industries. Using them as biosorbents is one way to reduce their environmental impact. In view of the above, the objective of this work was to demonstrate the deleterious effects of the agricultural pesticide glyphosate on the environment, as well as to propose a solution to mitigate the environmental impacts of its use by making use of rice husk acting as a biosorbent, in the decontamination of soil and water of rice planting areas under the flood system. Rice husk residues (in natura) and the soil used in the experimental areas were obtained from irrigated rice producers. In order to simulate the conditions of a rice field, three experimental stations were implanted. In AREA 01, 55 g of biosorbent were added (height of 0.5 cm). In AREA 02, 90 g (height of 1.0 cm) were added and in AREA 03, 110 g (1.5 cm of height) were added. The mixture of the liquid used in the experiment was 125 mL of glyphosate and 125 mL of water and was applied with a spray bottle. The concentration of glyphosate in the liquid mixture applied to the areas was 410.5 g/L, respecting the time of one day. And each experimental area received 83 mL of this mixture. The analysis of the assays for the determination of adsorption of glyphosate in the biosorbent were carried out by Operator Assessoria e Análises Ambientais Ltda. The methodology used to determine the adsorption of glyphosate on rice husk was Ion Chromatography and procedures standardized by the Brazilian Association of Technical Norms – ABNT: NBR 10006/2004 Procedure for obtaining solubilized extract of solid waste and NBR 10005/2004 Procedure for obtaining leached extract of solid waste. For the analyses, four samples were sent, one being considered the white sample without the addition of glyphosate or any treatment and the others representing each experimental area. With the results it was identified that the rice husk showed glyphosate adsorption values, indicating its possible use as a viable method of glyphosate removal.