ABSTRACT
The dissipation rate of seven currently used soybean and corn pesticides in two tropical soils (Ustox and Psamments) of Brazil was studied in a laboratory incubation experiment. Dissipation half-lives of pesticides ranged between 2 (monocrotofos) and 90 days (endosulfan-beta). The contrasting clay contents of the studied tropical soils (130 versus 470 g of clay kg(-1) of soil) did not influence the dissipation dynamics of pesticides substantially. Mineralization to CO(2) was high [up to 78% of the applied radioactivity (AR)] for the studied organophosphorus compounds and deltamethrin, which also formed considerable amounts of bound residues (>20% of AR) during the 80 days of incubation. The highest portion of nonextractable residues was found for alachlor and simazine (55-60% of AR). In contrast, the nonpolar trifluralin and endosulfan formed only small amounts of bound residues (mostly <20% of AR) but showed the highest dissipation half-lives (>14 days) in the studied soils, also due to a low mineralization rate. When endosulfan-sulfate, as the main metabolite of endosulfan, was considered, the half-life time of endosulfan compounds (sum of -alpha, -beta, and -sulfate) was enhanced to >160 days in both soils. In comparison with the laboratory experiments, dissipation half-life times of chlorpyrifos, endosulfan-alpha, and trifluralin were shortened by a factor of 10-30 in field trials with the same soils, which was related to the volatilization potential of pesticides from soils.
Subject(s)
Glycine max , Pesticide Residues/analysis , Pesticides/chemistry , Soil/analysis , Zea mays , Acetamides/chemistry , Brazil , Carbon Radioisotopes , Chlorpyrifos/chemistry , Endosulfan/chemistry , Half-Life , Herbicides/chemistry , Insecticides/chemistry , Isotope Labeling , Monocrotophos/chemistry , Nitriles , Pyrethrins/chemistry , Simazine/chemistry , Trifluralin/chemistry , Tropical ClimateABSTRACT
Os potenciais de lixiviaçäo de dezenove pesticidas nos primeiros 60 cm de latossolo da regiäo de Guaíra, Estado de Säo Paulo, foram estimados mediante fator deatenuaçäo (AF). O modelo aplicado considerou propriedades do pesticida e do solo, assim como a taxa de recarga hídrica líquida. Os pesticidas com maior potencial de lixiviaçäo foram manocrotofós>carbofuranmetalaxil>aldicarb>metolactor>metamidofós. Para todos os pesticidas estudados naquele latossolo, o tratamento da lixiviaçäo devido à volatilizaçäo foi muito pequeno quando comparado com o retardamento devido à sorçäo:Todos os pesticidas que apresentaram os mais altos potenciais delixiviaçäo foram os mais solúveis em água, com valores do coeficiente de partiçäo (Koc) iguais ou menores que 200 mL/g. Além disso, a meia-vida da maioria destes pesticidas excedeu 30 dias. Os resultados obtidos permitiram estimar que 15,2 por cento do Monocrotofós, 5,7 por cento do Carbofuran e 2,5 por cento do Metalaxil que atinge a superfície do solo ultrapassariam os primeiros 60 cm do perfil do solo, sendo que cerca de 8 mg para cada 100g de Monocrotofós aplicados na superfície do solo passariam através dos primeiros 3m. Com base nos baixos valores de AF calculdados, o potencial de lixiviaçäo dos pesticidas que tem sido usados em áreas agrícolas de Guaíra (SP) sobre latossolos apresenta-se baixo, assim como o consequente risco de contaminaçäo da água subterrânea
Subject(s)
Environment , Environmental Health , Percolation , Pesticides , Aldicarb , Carbofuran , Groundwater Pollution , MonocrotophosABSTRACT
Pesticide pollution of ground and surface water is of growing concern in tropical countries. The objective of this pilot study was to evaluate the leaching potential of eight pesticides in a Brazilian Oxisol. In a field experiment near Cuiabá, Mato Grosso, atrazine, chlorpyrifos, lambda-cyhalothrin, endosulfane alpha, metolachlor, monocrotofos, simazine, and trifluraline were applied onto a Typic Haplustox. Dissipation in the topsoil, mobility within the soil profile and leaching of pesticides were studied for a period of 28 days after application. The dissipation half-life of pesticides in the topsoil ranged from 0.9 to 14 d for trifluraline and metolachlor, respectively. Dissipation curves were described by exponential functions for polar pesticides (atrazine, metolachlor, monocrotofos, simazine) and bi-exponential ones for apolar substances (chlorpyrifos, lambda-cyhalothrin, endosulfane alpha, trifluraline). Atrazine, simazine and metolachlor were moderately leached beyond 15 cm soil depth, whereas all other compounds remained within the top 15 cm of the soil. In lysimeter percolates (at 35 cm soil depth), 0.8-2.0% of the applied amounts of atrazine, simazine, and metolachlor were measured within 28 days after application. Of the other compounds less than 0.03% of the applied amounts was detected in the soil water percolates. The relative contamination potentials of pesticides, according to the lysimeter study, were ranked as follows: metolachlor > atrazine = simazine >> monocrotofos > endsulfane alpha > chlorpyrifos > trifluraline > lambda-cyhalothrin. This order of the pesticides was also achieved by ranking them according to their effective sorption coefficient Ke, which is the ratio of Koc to field-dissipation half-life.
Subject(s)
Glycine max , Pesticides/chemistry , Soil/analysis , Zea mays , Acetamides/chemistry , Atrazine/chemistry , Biodegradation, Environmental , Brazil , Chemical Phenomena , Chemistry, Physical , Chlorpyrifos/chemistry , Endosulfan/chemistry , Half-Life , Monocrotophos/chemistry , Nitriles , Pesticides/analysis , Pyrethrins/chemistry , Simazine/chemistry , Trifluralin/chemistry , Tropical Climate , Water PollutionABSTRACT
O presente trabalho propôs-se a estudar os efeitos da exposiçäo pré-natal a dois fatores diversos: ao inseticida organofosforado monocrotofós e ao estresse por contençäo, durante o período organogênico, e evidenciar as possíveis alteraçöes no desenvolvimento físico e comportamental da prole de ratas observadas no período pós-natal. Foram utilizadas ratas Wistar prenhes subdivididas em dois grupos: estressado e näo estressado, que receberam, por gavage, do 6º ao 15º dias da gestaçäo, 1 mg/kg/dia do monocrotofós (tratado) ou água destilada (controle), e que após o parto tiveram suas ninhadas avaliadas quanto ao desenvolvimento físico e comportamental. Durante o período de tratamento as ratas dos grupos estressados (controle e tratado), apresentaram níveis plasmáticos de corticosterona, cerca de 3 vezes mais elevados do que o normal...
Subject(s)
Animals , Rats , Monocrotophos , Multiple Birth Offspring , Organophosphorus Compounds/toxicity , Pesticide Exposure , Toxicology , Corticosterone/administration & dosage , Immobilization , Insecticides/toxicity , Maternal Exposure , Prenatal Diagnosis , Rats, Wistar , Stress, PhysiologicalABSTRACT
Estudou-se os efeitos tóxicos dos inseticidas esfenvalerato, fenitrotion, fenpropatrin e monocrotofos sobre as ninfas de E. kraemeri em cultura de feijoeiro. A pesquisa doi conduzida no município de Nepomuceno - MG, utilizando uma lavoura comerical de cultivar "Carioca". Os compostos foram diluídos em água nas doses recomendadas pelos fabricantes para o controle de pragas, sendo a aplicaçäo realizada através de um pulverizador costal, propiciando volume de aplicaçäo de 400 L/ha. Os resultados mostraram que todos os compostos controlaram a praga em questäo, porém o fenitrotion na dose de 750 g i.a./ha apresentou o maior nível médio de controle.