Damián J.G. Marino

Environmental fate of glyphosate and aminomethylphosphonic acid in surface waters and soil of agricultural basins

Argentinian agricultural production is fundamentally based on a technological package that combines no-till and glyphosate in the cultivation of transgenic crops. Transgenic crops (soybean, maize and cotton) occupy 23 million hectares. This means that glyphosate is the most employed herbicide in the country, where 180-200 million liters are applied every year. The aim of this work is to study the environmental fate of glyphosate and its major degradation product, aminomethylphosphonic acid (AMPA), in surface water and soil of agricultural basins. Sixteen agricultural sites and forty-four streams in the agricultural basins were sampled three times during 2012. The samples were analyzed by UPLC-MS/MS ESI(+/-). In cultivated soils, glyphosate was detected in concentrations between 35 and 1502 μg kg(-1), while AMPA concentration ranged from 299 to 2256 μg kg(-1). In the surface water studied, the presence of glyphosate and AMPA was detected in about 15% and 12% of the samples analyzed, respectively. In suspended particulate matter, glyphosate was found in 67% while AMPA was present in 20% of the samples. In streams sediment glyphosate and AMPA were also detected in 66% and 88.5% of the samples respectively. This study is, to our knowledge, the first dealing with glyphosate fate in agricultural soils in Argentina. In the present study, it was demonstrated that glyphosate and AMPA are present in soils under agricultural activity. It was also found that in stream samples the presence of glyphosate and AMPA is relatively more frequent in suspended particulate matter and sediment than in water.

Comparative susceptibility to atrazine of three developmental stages of Rhinella arenarum and influence on metamorphosis: non-monotonous acceleration of the time to climax and delayed tail resorption.

Acute and subchronic toxicity of atrazine was evaluated in embryos (stage 4) and in premetamorphosis (stage 25) and prometamorphosis (stage 38-39) larvae of the common South American toad Rhinella arenarum (Anura: bufonidae). The influence of atrazine on the last stages of metamorphosis was also examined by exposing prometamorphosis larvae until completion of metamorphosis. Results obtained revealed that larvae in premetamorphosis are more sensitive than larvae in prometamorphosis and that these are, in turn, more sensitive than embryonic stages. Indeed, concentrations of atrazine as high as 30 mg/L had little effects on embryonic stages, the embryos surviving and developing in a similar manner as controls. LC50s of premetamorphosis larvae equaled 27.16, 7.03 and 2.32 mg/L of atrazine after 4, 14 and 21 days of exposure, respectively, compared to LC50s values of 18.27 and 14.43 mg/L after 14 and 21 days of exposure for larvae in prometamorphosis. In experiments with premetamorphosis larvae, the range of tested concentrations was extended to very low concentrations (down to 0.0001 mg/L) to examine whether recent findings of greater mortality at lower doses than at higher doses were also observed in R. arenarum but no such pattern was found. Exposure of prometamorphosis larvae to concentrations of atrazine of 10 mg/L and above widely prevented completion of metamorphosis and caused important mortality. Alternatively, whereas all animals eventually completed metamorphosis when exposed to concentrations of atrazine between 0.1 and 5 mg/L, the timings of metamorphosis were altered starting from 0.1 mg/L, the lowest concentration tested. Indeed, a significant decrease in the time needed for 50% of the larvae to reach the metamorphic climax (stage 42) was observed within this range of atrazine concentrations, the response presenting a U-shaped non-monotonic dose-response curve. Larvae exposed to these concentrations of atrazine also needed significantly more time for completing tail resorption, this effect being equivalent at all concentrations. Overall, the combination of these two different facets of atrazine influence on metamorphosis resulted in a significant acceleration of metamorphosis at 1 mg/L and a significant increase in the duration of metamorphosis at 5 mg/L, whereas no significant difference was observed with 0.1 mg/L.

Occurrence of glyphosate and AMPA in an agricultural watershed from the southeastern region of Argentina.

Glyphosate (GLY) and AMPA concentrations were determined in sandy soil profiles, during pre- and post-application events in two agricultural soybean fields (S1 and S2). Streamwater and sediment samples were also analyzed. Post-application sampling was carried out one month later from the event. Concentrations of GLY+AMPA in surface soils (0-5 cm depth) during pre-application period showed values 20-fold higher (0.093-0.163 μg/g d.w.) than control area (0.005 μg/g d.w.). After application event soils showed markedly higher pesticide concentrations. A predominance of AMPA (80%) was observed in S1 (early application), while 34% in S2 for surface soils. GLY+AMPA concentrations decreased with depth and correlated strongly with organic carbon (r between 0.74 and 0.88, p<0.05) and pH (r between -0.81 and -0.76, p<0.001). The slight enrichment of pesticides observed from 25 cm depth to deeper layer, in addition to the alkaline pH along the profile, is of high concern about groundwater contamination. Sediments from pre-application period showed relatively lower pesticide levels (0.0053-0.0263 μg/g d.w.) than surface soil with a predominance of glyphosate, indicating a limited degradation. Levels of contaminants (mainly AMPA) in streamwater (ND-0.5 ng/mL) denote the low persistence of these compounds. However, a direct relationship in AMPA concentration was observed between sediment and streamwater. Despite the known relatively short half-life of glyphosate in soils, GLY+AMPA occurrence is registered in almost all matrices at different sampling times (pre- and post-application events). The physicochemical characteristics (organic carbon, texture, pH) and structure of soils and sediment in addition to the time elapsed from application determined the behavior of these contaminants in the environment. As a whole, the results warn us about vertical transport trough soil profile with the possibility of reaching groundwater.

Flurochloridone-based herbicides induced genotoxicity effects on Rhinella arenarum tadpoles (Anura: Bufonidae).

Acute toxicity and genotoxicity of the flurochloridone (FLC)-containing commercial formulation herbicides Twin Pack Gold(®) (25 percent a.i.) and Rainbow(®) (25 percent a.i.) were evaluated on Rhinella arenarum (Anura: Bufonidae) tadpoles exposed under laboratory conditions. Lethal effect was evaluated as end point for lethality, whereas frequency of micronuclei (MN) and single cell gel electrophoresis (SCGE) were employed as end points for genotoxicity. Lethality studies revealed equivalent LC-5096 h values of 2.96 and 2.85 mg/L for Twin Pack Gold(®) and Rainbow(®), respectively. Twin Pack Gold(®) did not induce DNA damage at the chromosomal level, whereas Rainbow(®) increased the frequency of MN only when the lowest concentration (0.71 mg/L) was used. However, all concentrations of Twin Pack Gold(®) and Rainbow(®) increased the frequencies of primary DNA lesions estimated by alkaline SCGE. This study represents the first evidence of the acute toxic and genotoxic effects exerted by two FLC-based commercial formulations, Twin Pack Gold(®) and Rainbow(®), on tadpoles of an amphibian species native to Argentina under laboratory conditions. Finally, our findings highlight the importance of minimizing the impacts on nontarget living species exposed to agrochemicals.

Calculation of pK Values of Flavylium Salts from the Optimization of Correlation Weights of Local Graph Invariants

Abstract A new topological descriptor based on the process of optimization of correlation weights of local graph invariants is proposed to calculate pK values of flavylium salts. Comparison with available experimental data shows a quite satisfactory agreement and the present results improve some previous calculations resorting to the employment of several molecular and topological descriptors. Some future developments on this issue are pointed out aiming to the use of these models to propose new potential food dyes.

A quantitative HPLC-MS method for the simultaneous determination of testosterone, 11-ketotestosterone and 11-β hydroxyandrostenedione in fish serum.

A simple and novel HPLC-MS method for the simultaneous quantification of testosterone, 11-ketotestosterone, and 11beta-hydroxyandrostenedione in fish serum was developed and validated. Separation was achieved on a C-18 column using a water-acetonitrile mobile-phase with a cycle time of 12 min. Ion detection was performed using ESI positive SIM at [M+H] (m/z 303, 303, 289). The linear ranges (0.2-50 ng/ml), limits of detection (0.1-0.2 ng/ml) and quantification (0.2-0.5 ng/ml) were established. The method was validated by measuring the three androgens in goldfish sera, displaying comparable values to those reported by other analytical techniques (RIA, EIA).

Pesticide impact study in the peri-urban horticultural area of Gran La Plata, Argentina

Vegetable production systems are characterized by intense pesticide use, yet the effects on the surrounding environment are largely unknown and need to be studied. Given this knowledge gap, the objective of this work is to determine the impact of horticulture on a representative watercourse by conducting an integrated study of the occurrence and concentration of pesticides in bottom sediments and their relation to lethal and sublethal effects on benthic fauna. Two sampling campaigns were conducted during seasons of low and high pesticide application in five sites along the Carnaval creek, located in the peri-urban area of La Plata City (Buenos Aires, Argentina). The samples were tested for 36 pesticide compounds by GC-MS and LC-MS, and whole-sediment laboratory toxicity tests were performed using the native amphipod Hyalella curvispina. The results showed a general but variable distribution in the concentrations detected along the stream. For each sampling campaign (first/second), the total pesticide loads, measured as the sum of herbicides, insecticides and fungicides, were 1080/2329, 3715/88, and 367/5ngg-1 dw, respectively. Lethal and sublethal effects were observed in both sampling campaigns. In order to correlate both sets of results, data were assessed by multivariate analysis, including principal component analysis. The observed toxicity was considered to be mainly due to insecticides; thus, horticultural practices have an impact on nearby watercourses and can potentially endanger the benthic fauna. This is the first study in Argentina to assess the impact of pesticides on aquatic environments close to horticultural production areas.

Differential toxicity and uptake of Diazinon on embryo-larval development of Rhinella arenarum.

Diazinon, an anti-cholinesterase organophosphate, is an extensively used pesticide. The main objective of this work was to assess the lethal and sublethal effects of Diazinon and its comparison with the uptake by embryos and larvae of the common South American toad Rhinella arenarum by means of standardized bioassays during acute (96 h), short-term chronic (168 h) and chronic (504 h) exposures. Toxicity resulted time- and stage-dependent, thus the lethal concentration 50 for 96 h, 168 h and 504 h were 27.2; 20.1 and 6.8 mg Diazinon L(-1) for embryos and 8, 6.7 and 1.9 mg Diazinon L(-1) for larvae. It is noteworthy the remarkable differences found in the concentration which caused lethality with those causing adverse effects on development such as malformations (teratogenic effects). Therefore, the teratogenic index from 144 h was greater than two; the main adverse effects were axial flexures, irregular borders, wavy tail, microcephaly, malformed mouth and adhesive structures, gut miscoiling, underdeveloped gills, cloacal edema, desquamation and severe hydropsy. Moreover, the characteristic sublethal effect of Diazinon on larvae was abnormal behavior related to neurotoxicity with a NOEC-168 h of 4.5 mg Diazinon L(-1). Diazinon contents in R. arenarum were time-dependent and significantly related to exposure concentration for both embryos and larvae. Diazinon contents were also stage-dependent, as it was up to 27 times higher for organisms exposed from blastula stage onwards than early larvae. These facts and the Hazard Quotients, a numerical expression of ecological risk, of 2.73, which is above USEPAs Level of Concern, showed the threat that Diazinon represents for R. arenarum populations.

Screening of pharmaceuticals in surface water bodies of the Pampas region of Argentina

Pharmaceuticals have been included among emerging pollutants due to their continuous input in aquatic environments by wastewater discharges. The aim of the present study was detecting and analysing concentration levels of five commonly used pharmaceuticals in surface water bodies of the Pampas region of Argentina. Analyses were done on the soluble fraction by liquid chromatography with mass spectrometry (HPLC–MS) after solid–phase extraction (SPE) extraction. Results show the presence of pharmaceuticals in 10 out of 11 sampling sites, detecting higher concentrations in sites closer to wastewater discharges. Compounds more commonly found and at higher concentrations were caffeine and ibuprofen, with maximum detected levels of 13.32 and 9.66 µg/L, respectively. Highest detected concentrations of carbamazepine and atenolol were 0.63 and 0.55 µg/L, respectively. The compound less frequently detected and at lower levels of concentration was diclofenac.

QSPR modeling of heat of formation and heat of vaporization of aliphatic ketones by means of electrotopological indices

This work deals with the application of the electrotopological index to calculate the enthalpies of formation and vaporization of a set of 39 linear and non-linear C4 to C12 aliphatic ketones within the realm of QSPR theory. Two variants of this index are employed and results show the best results are obtained when the polar and hydrophobic portion of the molecules are taken into consideration.