Luiz Carlos Luchini

Impact of long‐term pesticide applications on some soil biological parameters

Abstract The soil oxidative and anaerobic processes, as well as, the microbial biomass were followed during three years in a cotton farm (Tatuí) where the recommended pesticides have been used for several years, and in an experimental field (São Paulo) treated first time with the same pesticides. The oxidative process was monitored by the dehydrogenase (DHA)‐activity using triphenyltetrazolium chloride (TTC) as substrate. The anaerobic process was followed by the iron‐oxide reduction, and the microbial biomass was estimated by the substrate (glucose)‐indiced respiration. Increases in DHA‐activity and in the microbial biomass occurred only in the farm soil, with concomitant decreases in iron‐reduction. In the experimental field soil, the increases in DHA‐activity were followed only by decreases in iron‐reduction. Soil characteristics were the determining factor for different biological parameters after pesticide inputs. All the pesticides produced at least one clear but transient effect.

Sorption, Degradation, and Leaching of Tebuthiuron and Diuron in Soil Columns

Abstract A study in small outdoor lysimeters was carried out to determine the leaching of the herbicides tebuthiuron and diuron in different soil types, using undisturbed soil columns. Soil sorption and degradation for both herbicides were also studied in the laboratory. The multi-layered AF (Attenuation Factor) model was evaluated for predicting the herbicides leaching in undisturbed soil columns. Tebuthiuron leached in greater amounts than diuron in both soils. Sorption was well represented by linear and Freundlich equations, however parameters from the linear equations were used in the AF model. In general, both herbicides presented very low sorption, with diuron presenting lower values of sorption coefficient than tebuthiuron in the two soils. Chromatographic data indicated rapid late degradation of diuron and tebuthiuron in both soil types at two different depths. Simple exponential equation was not able to represent degradation, thus a bi-exponential equation was used, and some model adjusting was needed. Average measured amounts of each herbicide were compared with amounts predicted by the multi-layered-soil AF model. The AF model was able to predict leaching amounts in the sandy soil, especially for diuron, however it did not perform well in the clayey soil.A study in small outdoor lysimeters was carried out to determine the leaching of the herbicides tebuthiuron and diuron in different soil types, using undisturbed soil columns. Soil sorption and degradation for both herbicides were also studied in the laboratory. The multi-layered AF (Attenuation Factor) model was evaluated for predicting the herbicides leaching in undisturbed soil columns. Tebuthiuron leached in greater amounts than diuron in both soils. Sorption was well represented by linear and Freundlich equations, however parameters from the linear equations were used in the AF model. In general, both herbicides presented very low sorption, with diuron presenting lower values of sorption coefficient than tebuthiuron in the two soils. Chromatographic data indicated rapid late degradation of diuron and tebuthiuron in both soil types at two different depths. Simple exponential equation was not able to represent degradation, thus a bi-exponential equation was used, and some model adjusting was needed. Average measured amounts of each herbicide were compared with amounts predicted by the multi-layered-soil AF model. The AF model was able to predict leaching amounts in the sandy soil, especially for diuron, however it did not perform well in the clayey soil.

Dissipation and degradation of DDT, DDE and parathion in Brazilian soils

Abstract The persistence of 14C‐DDT was monitored in the field at two sites representing tropical and subtropical climates in Sao Paulo State. Persistence of 14C‐DDE and 14C‐parathion was also studied in the subtropical region. In the extracts of soils treated with DDT, the main product was DDT. The amount of DDE was small and reached a maximum of 16% of the extractable radioactivity after 16 weeks, while DDD was detected only after 48 weeks. Bound 14C‐residues increased slowly and amounted to about 10% after 48 weeks. Extracts from 14C‐DDE‐treated soils contained only DDE after 48 weeks. I4C‐DDT dissipated with a half‐life of over 200 weeks in both regions while 14C‐DDE dissipated at a faster rate (Tl/2 = 88 weeks). It seems likely that the long persistence of DDT in this study relates to the acidic nature of the soil. Parathion dissipated much faster and, the degradation products paraoxon and 4‐nitrophenol, were identified after short periods. Bound residues increased with time to about 30% after 6 week...

Degradation of the insecticide parathion in methanol by gamma-irradiation

The gamma-radiation from60Co was used to induce parathion degradation in methanol solution, and the resulting products were quantified by GC-NPD and identified by GC-MS. The insecticide was completely degraded (99%) in methanol after treatment with 30 kGy doses at a dose rate of 3.12 kGy h−1. The metabolites detected after radiolysis were p-aminophenol, paraoxon and aminoparathion, but no p-nitrophenol. The parathion radiation yield (G-parathion) in methanol solution was also calculated.

Behavior of atrazine in soils of tropical zone

Abstract Movement and degradation of 14C‐atrazine (2‐chloro 4‐(ethylamino)‐6‐(isopropylamino)‐s‐triazine, was studied in undisturbed soil columns (0.50m length × 0.10m diameter) of Gley Humic and Deep Red Latosol from a maize crop region of Sao Paulo state, Brazil. Atrazine residues were largely confined to the 0–20cm layers over a 12 month period Atrazine degraded to the dealkylated metabolites deisopropylatrazine and deethylatrazine, but the major metabolite was hydroxyatrazine, mainly in the Gley Humic soil. Activity detected in the leachate was equivalent to an atrazine concentration of 0.08 to 0.11μg/1. The persistence of 14C‐atrazine in a maize‐bean crop rotation was evaluated in lysimeters, using Gley Humic and Deep Red Latosol soils. Uptake of the radiocarbon by maize plants after 14‐days growth was equivalent to a herbicide concentration of 3.9μg/g fresh tissue and was similar in both soils. High atrazine degradation to hydroxyatrazine was detected by tic of maize extracts. After maize harvest, w...

Multiresidue Screening Methods for the Determination of Pesticides in Tomatoes

The possibility of applying thin layer chromatography (TLC) detection for the analysis of pesticide residues in tomatoes was investigated. Samples of tomatoes that have never been treated with pesticide were fortified with atrazine, carbaryl, carbofuran, chloroxuron, diuron, dimethoate, imazalil, oxamyl and methamidophos. The samples were extracted, cleaned‐up by gel permeation chromatography and then applied on silica gel plates. The pesticides were eluted with ethyl acetate and dichloromethane. Two eluting solvent systems were tested, one using the reagents o‐ toluidine + potassium iodite (o‐TKI) and the other p‐ nitrobenzene fluoroborate (NBFB). After the development of the plates, the diameter of the spots was measured. The lowest minimum detection quantity (MDQ) for o‐TKI system for atrazine was 12 ng. The highest was 125 ng for carbofuran. Using NBFB system, the lowest MDQ was 60 ng for carbaryl and the highest was 70 ng obtained for carbofuran. Considering the concentration of these pesticides in the spiked tomato samples, the minimum concentration was 1.1 ng/µL and 32.3 ng/µL for atrazine and carbofuran, respectively, by using o‐TKI system. For NBFB system the minimum concentration reached was 3.5 ng/µL and 4.3 ng/µL for carbaryl and carbofuran, respectively. This study showed that TLC can be used for semi‐quantitative analysis.

Bioaccumulation and Retention of 14C-hexachlorobenzene (HCB): I. The Marine Tropical Mussel Perna perna

HCB (hexachlorobenzene) is a ubiquitous pollutant, which is highly toxic to aquatic organisms; however, it is continuously generated and released to the environment. In order to explore the potential of the mussel Perna perna as a sentinel species for monitoring HCB contamination, we have investigated the accumulation and depuration kinetics of 14C-HCB in the mussel exposed to spiked sediment. The sediment, water and mussels were sampled periodically and submitted to solvent extraction for the determination of the radiocarbon and organism lipid content. The analysis showed that most of the radioactivity remained in the sediment as a potential long-term source of pollution, whereas the HCB concentration in the seawater was below the detection limit. The mussel soft tissues were contaminated very little; the residues were distributed as extractable and bound residues, which were strongly correlated with the lipid content of the mussel tissues. The sensitive radiotracer technique used allowed the detection o...

Influence of Substrate on Bioaccumulation of 14C-Paraquat in Compost Worms Eisenia foetida

Contamination of soil with pesticides can be evaluated using toxicity tests with worms because their ecological niche makes them good bioindicators. Bioaccumulation in compost worms of [methyl- 14C] paraquat (1,1′-dimethyl-4,4′-bipyridinium dichloride) was measured after three-month exposure in two substrates with differing physicochemical characteristics, in particular their organic matter and clay contents. The treatments were 1.2, 12, and 120 μg paraquat g−1 substrate. The action of the worms did not influence the loss of 14C from the substrates, as the 14C-recovered was essentially quantitative at the end of the study in both the presence and absence of the worms. The organic matter and clay contents of the substrates determined the extent of the paraquat uptake by the worms; worms from the substrate with smaller amounts of clay and organic matter had the higher values of the bioconcentration factor (BCF), these being about 5 (fresh-weight basis) and independent of the application rate. The BCF values in the substrate containing more organic matter and clay were smaller but increased from 1.1 to 3.8 with the increasing rates of application. However, in both substrates the amounts of paraquat bioaccumulated in the worms was always less than 1% of that applied, indicating the very strong binding of paraquat to the substrates and hence low availability to the worms.

Análise de resíduos de pesticidas em tomates por cromatografia em camada delgada

Pesticide residues are determined by thin layer chromatography (TLC) using the Hill reaction as a detection method. Tomatoes samples without pesticide were fortified with atrazine, diuron, chloroxuron and metribuzin, and were applyed in silica gel plates with the help of a microsyringe. The pesticides were elued with ethyl acetate. There was no need of cleaning up because no interference was noticed. After the revelation of the plates, the diameters of the spots were measure by using a rule. The range of the determined concentration for all the pesticides was from 0.1 to1.0 ng/mL. The results obtained through TLC can be used for semi-quantitative analysis.The results obtained were compared to gas and liquid chromatography, showing good agreement between both techniques.

Avaliação da vestimenta utilizada como equipamento de proteção individual pelos aplicadores de malationa no controle da dengue em São Paulo, Brasil

O inseticida malationa em calda oleosa e utilizado no controle do Aedes aegypti e a sua aplicacao e feita por meio de nebulizacao. Essa atividade exige o uso de equipamento de protecao individual (EPI) pelos aplicadores. Este trabalho avaliou a capacidade de retencao do inseticida malationa nas vestimentas do EPI apos nebulizacao em campo. Foram acompanhadas nebulizacoes em campo, realizadas pelos agentes de zoonoses, na cidade de Sao Paulo, Brasil. Antes de cada nebulizacao eram colocados absorventes sob e sobre a vestimenta do EPI no torax, na face superior da parede toracica (costas) e nos antebracos. Apos cada aplicacao, os absorventes eram retirados, identificados e submetidos a extracao sob agitacao mecânica. Os extratos foram analisados por cromatografia a gas com detector de ionizacao de chama. Observou-se a presenca de malationa nos absorventes sob as vestimentas do EPI ja na primeira aplicacao, antes da lavagem. Os resultados indicam que os agentes, nas condicoes avaliadas, estao expostos ao malationa, mesmo com uso de vestimentas de EPI novos.Malathion insecticide in vegetable oil is used to control Aedes aegypti and is applied by spraying, which requires the use of personal protective equipment (PPE). The current study assessed the capacity of PPE suits to retain malathion. The study monitored field spraying in São Paulo, Brazil. Before each spraying, feminine sanitary napkins were placed under and upon the PPE suit in the chest, back, and forearms. After spraying, the sanitary napkins were removed, labeled, and submitted to extraction under mechanical agitation. The extracts were analyzed by gas chromatography with a flame ionization detector. Presence of malathion in sanitary napkins under PPE suits was observed after spraying and before washing the suits. The findings indicate that sprayers are exposed to malathion, even when they use new PPE suits.