Maria José Cerejeira

Pesticides in Portuguese surface and ground waters

Pesticides used in Portuguese agricultural areas have been found in surface and ground waters. In the surface water collected in three river basins from 1983 to 1999, insecticides and herbicides were detected from the monitored pesticides, particularly atrazine, chlorfenvinphos (Z+E), alpha- and beta-endosulfan, lindane, molinate and simazine, reaching the maximum values, respectively, of 0.63, 31.6, 0.18 microg/L (alpha-endosulfan), 0.18 microg/L (beta-endosulfan), 0.24, 48 and 0.3 microg/L. In the ground water collected from the wells of seven agricultural areas from 1991 to 1998, several monitored herbicides were detected: alachlor, atrazine, metolachlor, metribuzine and simazine, reaching the maximum concentration values of 13, 30, 56, 1.4 and 0.4 microg/L, respectively. The herbicides more frequently detected were atrazine (64%), simazine (45%) and alachlor (25%). Other than these, the monitored pesticides can be present in Portuguese surface and ground waters. Therefore, to improve the analytical conditions, the use of multiresidue methods and automated techniques are desirable in future work.

BIOCONCENTRATION OF ORGANIC CHEMICAL VAPOURS IN PLANT LEAVES : THE AZALEA MODEL

Abstract Experimental data on the accumulation and release kinetics of azalea leaves exposed to constant vapour levels of alachlor, dieldrin and 3,4,3′,4′-tetrachlorobiphenyl are reported. Calculated leaf/air bioconcentration factors for these and other 11 organic chemical vapours are used to improve a correlation with the 1- octanol water and air/water equilibrium partition coefficients.

Chlorinated dioxins: volatilization from soils and bioconcentration in plant leaves.

Polychlorinated dibenzodioxins (PCDDs) are a group of xenobiotics of extreme environmental interest, by virtue of their high toxic potential, coupled with high bioaffinity and resistance to degradation. One in particular (2,3,7,8tetrachloro dibenzo-p-dioxin, 2,3,7,8-TCDD), is probably the most poisonous substance ever introduced into the environment. PCDDs are not intentionally produced, but mainly arise from combustion processes and certain industrial activities; all the sources of these substances are not yet completely known (Hutzinger and Fiedler 1989). However, loads to the environment are certainly significant as PCDD residues may be found in many different environmental matrices (Jones and Bennet 1989).

Pesticides and nitrates in groundwater from oriziculture areas of the ‘Baixo Sado’ region (Portugal)

The aim of this study was the groundwater evaluation to pesticide compounds and nitrates in oriziculture areas of the ‘Baixo Sado’ region (Portugal), based on their use, predictive approaches, and field and laboratory work. One or more of the pesticide compounds analysed (chlorfenvinphos, cycloxydim, 3,4-dichloroaniline, endosulphan, MCPA, molinate, oxadiazon, profoxydim, propanil) were detected in 62% of 171 water samples collected from 22 wells used for public supply, domestic supply, and irrigation, during 2002 and 2003. From the total samples, 6% presented maximum concentration levels of at least one of the compounds above 0.1 µg L−1. Mixtures of pesticide compounds were observed in 25% of the total groundwater samples, with up to five substances being detected in each one. The concentration sum of all was above 0.5 µg L−1 in four water samples. All the analysed compounds, with the exception of the insecticide chlorfenvinphos, occurred in groundwater. Molinate was the most frequently detected (55%), particularly with maximum concentration levels above 0.1 µg L−1. Detection frequencies were higher in water samples collected from irrigation wells (78%). Groundwater exposure to total pesticides and nitrates was analysed. Maximum concentration levels were 59.6 µg L−1 and 183 mg L−1 respectively. A seasonal variation pattern could be observed for both parameters in water samples collected from some wells. The results from this study show that sustainable use of pesticides and nitrogen fertilizers is required in order to achieve an overall contamination reduction from these compounds in the aquatic environment.

Simazine, metribuzine and nitrates in ground water of agricultural areas of Portugal

From 1996 to 1998, residues of simazine, metribuzine and nitrates in ground water (irrigation and drinking) were monitored in wells of the main vineyard, apple and pear orchards, potato and tomato growing areas of “Ribatejo e Oeste”;, an important agricultural region of Portugal. Of a total of 214 samples collected in nine different areas, simazine was the most frequently detected herbicide. It was measured in 96 water samples (44.9%) and reached a maximum concentration of 0.43 μg/L. Metribuzine was found in 15.4% of the samples with a maximum concentration of 1.45 ug/L. Levels of metribuzine and simazine above 0.1 ug/L were found respectively in 4.7% and 6.1% of the total number of analysed samples. Only residues of simazine were detected in ground water for human consumption. Nitrates were also analysed and levels above the maximum concentration of 50 mg/L were found in some areas, reaching a maximum concentration value of 276mg/L.

Comparing the sensitivity of soil invertebrates to pesticides with that of Eisenia fetida

The sole routine testing of the standard earthworm Eisenia fetida for the terrestrial risk assessment of pesticides has been under much debate since other soil invertebrates may be more sensitive than this standard test species. However, the very low availability of laboratory toxicity data for taxa other than E. fetida has greatly hampered sensitivity comparisons. In the present study, the relative tolerance (T(rel)) approach was used to enable comparing toxicity thresholds obtained from the US-EPA ECOTOX database, for main terrestrial taxonomic groups and pesticidal types of action (insecticides, fungicides, herbicides, and other) separately. Analyses confirmed previously reported lower and higher sensitivity of collembolans to fungicides and insecticides, respectively. However, various other discrepancies in susceptibility relative to E. fetida were encountered as indicated by species sensitivity distributions and/or calculated 95% confidence intervals of T(rel) values. Arachnids and isopods were found to be more sensitive to insecticides, and nematodes to fungicides, as compared to E. fetida. Implications of study findings for the terrestrial risk assessment of pesticides are discussed.

Environmental Fate of Neonicotinoids and Classification of Their Potential Risks to Hypogean, Epygean, and Surface Water Ecosystems in Brazil

ABSTRACT Due to their reported high toxicity to honey bees, ecotoxicological studies into the side-effects of neonicotinoid insecticides have focused almost exclusively on these organisms. The fate of neonicotinoids and potential toxic side-effects on other (especially non-standard) organisms have received considerably less attention. In the present study, the environmental distribution and leaching potential of neonicotinoids registered for agricultural use in Brazil (acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam) were studied by applying several environmental fate models and indices. Potential risks to various environmental compartments were evaluated by applying ranking indices to the maximum application rates recommended in Brazil. Although bees were indeed found to be the most sensitive organism, the neonicotinoids also indicated potential environmental risks to other organism groups. Due to the greater maximum application rates recommended in Brazil as compared to other parts of the world, environmental risk and resistance potential for at least imidacloprid appears especially high in Brazil. Attention should thus also be allocated to organisms other than bees and to resistance potential when performing an environmental risk assessment of neonicotinoids if they are used at relatively high application rates.

Use of new microbiotests with Daphnia magna and Selenastrum capricornutum immobilized forms

A preliminary assessment of toxicity to aquatic life of water from rice fields treated with pesticides, and particularly with the herbicides molinate and quinclorac, was performed from June to August 1996 in a rice paddy area integrated in a Natural Reserve. New rapid-screening microbiotests with Daphnia magna and Selenastrum capricornutum were used. Water samples were collected from: a water source for irrigating the rice fields, two rice plots, a drainage channel and the river in which the water is discharged. The results showed that while the water for irrigation was not toxic to D. magna, the samples collected from the river were very toxic causing 100% immobility in D. magna and substantial inhibition of Selenastrum growth. This, however, is due to the brackish nature of the river water. Water collected in the drainage channel of the rice fields were also found to be quite toxic. A greater effect was detected in samples from the rice plot treated with molinate than from that treated with quinclorac, suggesting that molinate treatment was more toxic to both species. The results indicate that the rapidity, simplicity and relatively low cost of the new microbiotests make them very practical for initial acute toxicity screening and offer an alternative to provide evidence for changes needed in agriculture practices for a better protection of the aquatic environment.

Preliminary aquatic risk assessment of imidacloprid after application in an experimental rice plot

The potential aquatic risk of application of the neonicotinoid insecticide imidacloprid for aphid control in rice was assessed. To this end, imidacloprid was applied as Confidor(®) 200 SC at the recommended field dose of 100g a.i./ha to a Portuguese rice plot. Subsequently, fate of the test compound in water and potential effects of water samples on a battery of test species were determined. As compared to the first-tier predicted environmental concentrations (PECs) calculated using MED-Rice (around 30µg/L depending on the scenario used) and US-EPA (78µg/L) simulations, the actual peak concentration measured in the paddy water (52µg/L) was higher and lower, respectively. As was anticipated based on 50% effect concentrations (EC50 values) for Daphnia magna published in the open literature and that calculated in the present study (48h-EC50 immobility=84mg/L), no effects were observed of field water samples on daphnids. The sediment-dwelling ostracod Heterocypris incongruens, however, appeared relatively sensitive towards imidacloprid (6d-EC50 growth inhibition=0.01-0.015mg/L) and a slight effect was indeed noted in field samples taken the first week after application. Species sensitivity distributions based on published EC50 and NOEC values also revealed that other species are likely to be affected at the peak and time-weighted average imidacloprid concentrations, respectively. By applying the relative tolerance approach (i.e. by dividing the EC50 value of a certain species with that of Daphnia magna), ostracods appear to contain the most sensitive taxa to imidacloprid, followed by EPT (Ephemeroptera, Plecoptera and Trichoptera) taxa. Future field studies into (higher-tier) fate modelling of pesticides in rice paddies and effect assessment on field communities are required to ensure protection of aquatic life and wildlife (e.g. birds) from pesticide stress.

Assessing the quality of freshwaters in a protected area within the Tagus River basin district (central Portugal).

Water-sediment quality was assessed in an agricultural zone of a protected area within the Tagus River basin district (central Portugal) combining chemical analysis to 12 pesticide compounds and whole toxicity testing using the bacterium , the algae , the crustacean , and the midge . The herbicides alachlor, atrazine ethofumesate, metolachlor, terbuthylazine, the insecticides chlorfenvinphos and chlorpyrifos, and the metabolite 3,4-dichloroaniline were detected in surface water samples at four sites and in groundwater samples from six wells, during four sampling occasions. Measured concentrations were compared with parametric values for human consumption, groundwater quality standards, and environmental quality standards applicable to surface water established in European Union legislation. Most severe adverse effects were noted on the growth of and lethality of in nondiluted water samples. Taking into account the values calculated by the method of toxic unit summation for pesticide mixtures, it was not possible to link the pesticides found to the toxicity detected in the water samples. Conducting this study with chemical analyses and biotests provided a more comprehensive quality assessment and realistic picture of the environmental samples analyzed, although additional studies are needed to evaluate the performance of mixture models for predicting mixture toxicity. This study underlines the importance of chemical analysis and whole toxicity testing as tools for assessing the impact of human activity on the status of water, mainly in protected zones.