Mara Mercedes de Andréa

OPTIMIZING MICROWAVE-ASSISTED SOLVENT EXTRACTION (MASE) OF PESTICIDES FROM SOIL

Microwave-assisted solvent extraction (MASE) was investigated as an alternative for extraction of parathion (O,O-diethyl O-4-nitrophenyl phosphorothioate), methyl parathion (O,O-dimethyl O-4-nitrophenyl phosphorothioate), p,p′-DDE [1,1′-dichloro-2,2-bis(4-chlorophenyl)ethane], hexachloro-benzene (HCB), simazine (6-chloro-N 2,N 4-diethyl-1,3,5-triazine-2,4-diamine) and paraquat dichoride (1,1′-dimethyl-4,4′-bipyridinium) from two different soils and from an earthworm-growing substrate. The matrices were fortified with 14C-radiolabeled pesticides and extracted with various solvent systems under different microwave conditions. Recoveries of more than 80% could be obtained depending on the used microwave conditions and solvent, except for paraquat whose recovery was generally less efficient. Thus, MASE can be successfully used to extract pesticides from environmental and biological samples and could be a viable alternative to conventional extraction methods. The technique uses smaller amounts of organic solvents, thereby minimizing the costs of the analysis and the disposal of waste solvent.

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.

Screening mitosporic fungi for organochlorides degradation

Fifty-five isolates of filamentous fungi were studied regarding their ability to decolorize Remazol brilliant blue R dye. The fungi were isolated from soil in the Baixada Santista region, which is contaminated with industrial residues containing a mixture of organochlorine compounds, mainly hexachlorobenzene. The fungi were grown in liquid malt extract medium with 0.02% of dye and shaken at 200 rpm for 14 days at 28 ± 2oC. Two types of behavior regarding the dye were observed: adsorption and degradation. Eupenicillium baarnenseSsp1951 and Ssp1952 and Eupenicilliumcrustaceum SSP1953 presented high RBBR decolorization and were then analyzed regarding their ability to degrade 14C-hexachlobenzene (4138.31 mg HCB per kg soil) during a 56 days culture at 28 ± 2oC. Eupenicillium crustaceum SSP1953 was able to reduce n-hexane soluble 14C-compounds (24.6%) and to form non-extractable 14C-residues (20.5%). The same behavior was also observed in the two E. baarnense strains (Ssp1951 and Ssp1952) but the percentages were lower than those obtained for Eupenicilliumcrustaceum. The main action of Eupenicillium spp on HCB is to transform it into non-extractable 14C-residues as confirmed by the gas chromatography results.

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...

Degradação acelerada do metalaxil em solos agricultáveis do Estado de São Paulo

This work investigated the effect of repeated applications on enhanced degradation of metalaxyl in two different agricultural soils used for cultivation of orange and lemon from Casa Branca and Itapetininga districts of Sao Paulo State, Brazil. Soil samples were collected from areas repeatedly treated with commercial ridomil 50GR for six successive years, and from other areas never exposed to this fungicide. At the laboratory, soil samples received a 14C-metalaxyl solution and its degradation was studied through radiometric techniques to measure biomineralization and recovery of extractable- and soil-bound products. Enhanced degradation was verified only in one soil, although partial degradation and mineralization of the fungicide were detected in both soils. The different rates and patterns of metalaxyl degradation in the soils were probably due to their different physical, chemical, and biological characteristics.

Influence of soil properties on bioaccumulation of 14C-simazine in earthworms Eisenia foetida

Abstract The toxicity of pesticides has been evaluated by several methods including tests with earthworms in both artificial and natural soils treated with the compounds. The ecological niches of earthworms make them good bioindicators of soil contamination. The bioaccumulation of 14C-simazine (6-chloro-N 2 -N 4 -diethyl- 1,3,5-triazine-2,4-diamine) was evaluated in earthworms (Eisenia foetida) maintained during three months in two substrates with different physical-chemical characteristics. The substrates were treated with 3.0 mg and 330 kBq of 14C-simazine kg−1 substrate. Results indicated that worms did not influence simazine dissipation in both substrates as indicated by similar recoveries and with no statistical differences with and without earthworms. The radiocarbon recoveries were 86.8 and 95.3%, respectively in the substrates with lower and higher organic matter contents with earthworms, and 91.0 and 107.4% in the same substrates without worms. However, in earthworms the recoveries were statistically higher when they were maintained in the substrate with lower amount of organic matter (0.89%) than from the higher one (0.33%). Consequently, 14C-simazine bioconcentration factor (BCF) was also greater in the substrate with lower organic matter (6.89 ± 1.55) than in the substrate with higher organic matter content (0.88 ± 0.06). The results suggest that the higher soil organic matter content will cause lower probability of contamination of soil organisms with simazine.The toxicity of pesticides has been evaluated by several methods including tests with earthworms in both artificial and natural soils treated with the compounds. The ecological niches of earthworms make them good bioindicators of soil contamination. The bioaccumulation of 14C-simazine (6-chloro-N2-N4-diethyl- 1,3,5-triazine-2,4-diamine) was evaluated in earthworms (Eisenia foetida) maintained during three months in two substrates with different physical-chemical characteristics. The substrates were treated with 3.0 mg and 330 kBq of 14C-simazine kg(-1) substrate. Results indicated that worms did not influence simazine dissipation in both substrates as indicated by similar recoveries and with no statistical differences with and without earthworms. The radiocarbon recoveries were 86.8 and 95.3%, respectively in the substrates with lower and higher organic matter contents with earthworms, and 91.0 and 107.4% in the same substrates without worms. However, in earthworms the recoveries were statistically higher when they were maintained in the substrate with lower amount of organic matter (0.89%) than from the higher one (0.33%). Consequently, 14C-simazine bioconcentration factor (BCF) was also greater in the substrate with lower organic matter (6.89+/-1.55) than in the substrate with higher organic matter content (0.88+/-0.06). The results suggest that the higher soil organic matter content will cause lower probability of contamination of soil organisms with simazine.

Comparação de métodos para determinação de biomassa microbiana em dois solos

The potential of soil microbial biomass measurements as indicators of soil bioactivity and interferences in this environment can be verified by the amount of published papers on the subject. Nevertheless, a comparison among data from different authors, regions, and soils is only possible when the methodology employed in the determinations is the same. Several papers, however, propose different methodologies and calculations. This study evaluated the results of microbial carbon determination by different extraction and digestion methodologies in two distinct soils. It was also performed biomass calculations, besides calculations for indirect transformation of CO2 from basal and induced respiration into microbial carbon in the two soils. Results varied greatly among methods and calculations, and the conclusion was drawn that the most frequently used methodology (Vance et al., 1987) should be adopted for a valid comparison of the amount of microbial carbon among soils and literature data.

Degradation of parathion by soil kept moist with and without repeated applications

Abstract Radiochemical methods were used to show that the persistence of parathion in a gley humic soil, rewetted and kept moist after air-drying, decreased with time. Repeated treatment with parathion (8 μg g −1 ), as an aqueous dilution of Folidol each month for 10 months had no effect on the persistence of parathion. However, the microbial population was modified by repeated treatment with parathion because aqueous suspensions of soil which received parathion degraded it faster than soil, which did not. Also, bacteria, tentatively identified as a Nocardia spp. able to degrade parathion and 4-nitrophenol, were isolated from parathion treated soil but not from untreated soil.

Glyphosate: influência na bioatividade do solo e ação de minhocas sobre sua dissipação em terra agrícola

The widespread usage of pesticides leads to the need of improving the knowledge on their environmental behaviour in order to decrease the risks to biota, as well as the water, soil, and food contamination. The influence of the earthworms Eisenia foetida on the dissipation of glyphosate, the herbicide bioaccumulation in the worms and the influence of the herbicide on the endogeneous microbial bioactivity were evaluated in an agricultural soil sample treated with aqueous solution of 14C-glyphosate. The studies were performed in systems maintained for 2 or 4 months containing soil samples treated with three different concentrations of 14C-glyphosate and containing or not the earthworms. After these periods, soil samples and the earthworms were extracted and combusted for radiocarbon quantification by liquid scintillation counting (ECL). The microbial bioactivity was evaluated through the activity of the dehydrogenase enzyme. Results showed that earthworms did not influence the soil dissipation of glyphosate, independently of the contact period, although they bioaccumulated glyphosate residues, proportionally to the contact period. The higher period favoured the 14C-non-extractable or bound residues production. Soil bioactivity was not altered, neither by the earthworms, nor by the treatments or time after treatments.

Dissipação de simazina em solo por ação de minhocas (Eisenia foetida)

The soil contains a large variety of macroscopic and microscopic organisms, which compete for the available resources. Fertilizers and pesticides usually applied in soil to increase the agricultural production may determine environmental changes. Among the edaphic organisms, earthworms are outstanding for their number and role they play on soil characteristics. The performance of earthworms on the persistence, transformation and bioaccumulation of simazine was assessed in a soil treated with the herbicide. The earthworms were sensitive to simazine [CL50(14 days) of 54 mg IA kg-1 soil], accumulated the compound or its metabolites in their tissues (FB = 1,03), and reduced the formation of soil bound residues (about 26 and 33%, with and without earthworms, respectively).