RESUMO
The sorption and desorption of diuron by soil samples from Horizons A and B (HA and HB) and by their different clay fractions were investigated, using two soil samples, classified as Typic Argiudoll and Oxic Argiudoll. The sorption and desorption curves were adjusted to the Freundlich model and evaluated by parameters Kf, Kd and Koc. Based on the data of groundwater ubiquity score (GUS), leachability index (LIX) and hysteresis index (HI), the risk of groundwater pollution was evaluated. The Kd values obtained for soil samples were between 4.5 mL g-1 (Oxic Argiudoll - HB) and 15.9 mL g-1 (Typic Argiudoll - HA) and between 1.13 and 14.0 mL g-1 for the different mineral fractions, whereas the Koc values varied between 276 (Oxic Argiudoll - HB) and 462 (Typic Argiudoll - HA). According to the parameter GUS, only Oxic Argiudoll - HB presented leaching potential, and based on the LIX index this same soil presented the highest leaching potential. Some samples presented low LIX and GUS values, indicating no leaching potential, but none presented HI results indicative of hysteresis, suggesting weak bonds between diuron and the soil samples and, hence, the risk of groundwater pollution by diuron.
Assuntos
Argila/química , Diurona/química , Poluentes do Solo/química , Solo/química , Adsorção , Brasil , Meio Ambiente , Água Subterrânea , Minerais/química , Poluentes Químicos da Água/químicaRESUMO
A method for determining atrazine in soil extracts was evaluated by flow injection analysis with spectrophotometric detection. The method is based on the reaction of atrazine with pyridine in an acid medium followed by the reaction with NaOH and sulfanilic acid. Several analytical conditions were previously studied and optimized. Under the best conditions of analysis, the limits of detection and quantification were 0.15 and 0.45 mg L(-1), respectively, for a linear response between 0.50 and 2.50 mg L(-1), and a sampling throughput of 21 determinations per hour. Using the standard addition method, the maximum relative standard deviation of 17% and recovery values between 80 and 100% were observed for three extracts from soil samples with different composition. The proposed method is simple, low-cost and easy to use, and can be employed for studies involving atrazine in soil samples or for screening of atrazine in soils.