Experimental methods to evaluate herbicides behavior in soil

Abstract

-Pesticides are an essential tool for agriculture, however, studies have been shown that only 45% of the sprayed products reach the target-crop, whereas 30% is drifted, 10% is lost due to transport processes (leaching, volatilization and runoff), and 15% reaches the soil. Moreover, only 1% of the applied product reaches the target, in other words, the pathogens, weeds and insects. Even though, risk assessments for environmental contamination due to off-target movement of a pesticide are mandatory and performed prior to its registration, these products are often detected contaminating non-target sites, and freshwater ecosystems are the main impaired. Various biological, physical and chemical processes determine the environment fate and the efficacy of these compounds. Thus, there are several experimental techniques used to evaluate the behavior of herbicides in soil. This review aims to summarize the most commonly used methods to describe and evaluate each process to which a herbicide is subjected in soil and, their advantages and disadvantages. In general, when studying the fate of pesticides in the environment, laboratory experiments provide more precise information because it is possible to control the environmental conditions and isolate the factors that interest the researcher. However, it is important to mention that there is not a more efficient method but there are methods that can provide a better result in a given situation. Thus, the method choice depends in the study aim and the available infrastructure. Keywords: adsorption, biodegradation, leaching, runoff, volatilization Resumo -O uso de agrotóxicos na agricultura é praticamente indispensável, contudo, estudos estimam que somente 45% do produto aplicado atinge a cultura, sendo que aproximadamente 30% sofrem deriva, 10% são perdidos por algum processo de transporte (lixiviação, volatilização e escoamento) e 15% atingem o solo. Além disso, do total aplicado, apenas 1% atinge o alvo, ou seja, patógenos, plantas daninhas e insetos. Embora avaliações de riscos de contaminação ambiental de agrotóxicos sejam obrigatórios para o registro e comercialização, frequentemente estudos relatam a presença destes em locais não alvos, sendo os corpos de água os principais prejudicados. Vários processos biológicos, físicos e químicos determinam o destino ambiental e a eficiência desses. Assim, diversos métodos experimentais podem ser utilizados para avaliar o comportamento de agrotóxicos no ambiente. Essa revisão objetiva resumir os métodos mais comumente utilizados para descrever Schreiber et al.Rev. Bras. Herb., v.17, n