Test de toxicidad sobre la especie Atriplex lampa, su aplicación para la evaluación de riesgo asociado a derrames de petróleo en suelos de la Patagonia / The application of toxicity test on the specie Atriplex lampa in the risk assessment of oil spills in Patagonian soils

Se estudiaron suelos contaminados con hidrocarburos del petróleo, en cercanías de la ciudad de Comodoro Rivadavia (Chubut, Argentina). Además de cuantificar el contenido de hidrocarburos totales en suelo (TPH), se realizaron bioensayos, utilizando especies vegetales como organismos de prueba. Los índices utilizados fueron: el porcentaje de germinación (G), la elongación de la radícula (R) y del hipocotilo (H) en Lactuca sativa L y dos especies autóctonas de la región patagónica, Atriplex lampa y Prosopis denudans. Se consideró, además, el efecto de la salinidad sobre los bioensayos, en base a la medición de la conductividad eléctrica del suelo (CE). Los resultados obtenidos del análisis por componentes principales, muestran que la primera componente explica el 58,3 % de la variabilidad total con un gradiente de toxicidad al cual contribuyen, principalmente, el porcentaje de germinación de Lactuca sativa L (GL) y Atriplex lampa (GA), en este orden de significancia. La segunda componente explica el 16,9 % y la misma está caracterizada por TPH y CE. Además, no se ha encontrado una correlación simple y directa entre TPH y toxicidad, lo cual sugiere que TPH, en conjunción con ensayos ecotóxicos, parece ser una herramienta más adecuada para definir el punto final de una remediación. La especie autóctona Atriplex lampa mostró tener una sensibilidad similar a la especie Lactuca sativa L por lo que podría considerarse su utilidad como una especie fitoindicadora en las evaluaciones de riesgo ambiental (AU)

Oil spills near of the Comodoro Rivadavia city (Chubut, Argentina) were studied. Total petroleum hydrocarbon (TPH) is used to characterize the samples and bioassays were carried out using plants as test organisms. The percentage germination (G), the root elongation (R) and the hypocotyls elongation (H) in Lactuca sativa L and two native species to Patagonian region, Atriplex lampa and Prosopis denudans were used as toxicological indexes. It was considered the effect of salinity on the bioassays, based on the measurement of the electrical conductivity of soil (EC). Application of principal component analysis to experimental data showed that the first component accounted for more than 58.3 % of variance. The 1st PC is largely influenced by the germination percentage of Lactuca sativa L (GL) and Atriplex lampa (GA), in that order of significance. The second component accounted 16.9 % of variance. The 2nd PC is largely influenced by TPH and EC. A simple and direct correlation between TPH and toxicity was not found suggesting that TPH in conjunction with ecotoxicity test would be more successfully tool to define the end point of a remediation. The native specie Atriplex lampa showed to have a similar sensibility to the Lactuca sativa L suggesting that it could be used as a phytoindicator in assessement of environmental risk (AU)

Natural attenuation of oil spills in Patagonian soils. Characterization by 1H NMR spectroscopy.

The natural attenuation of oil spill contaminated soils, with different exposure times, in Patagonian environment was evaluated by the use of several parameters to quantify the degree of changes in the composition. Column (CC) and gas chromatography (GC); UV-visible and 1H NMR techniques were used to determine compositional and structural indexes. The results show that the nC18/Phytane GC index, that was 1.5 for crude oil, decreased with exposure time to values between 0.97-0.17 in the residues. The percentages for the four aliphatic (H1-H4) and the aromatic (H(A)), proton types, determined by 1H NMR, were: 12.9-34.4 (H1), 43.3-60.2 (H2), 4.24-24.2 (H), 1.33-17.9 (H4), and 0.44-4.81 (HA), in crude oil and residues, respectively. Furthermore, the characterization of significant 1H NMR signals indicated the presence of carboxylic acid hydrogens in the polar fraction of the crude oil and of residues of two years age. The Principal Components Analysis (PCA) of the parameters determined by CC, GC and NMR showed that the first three principal components (1st, 2nd, and 3 rd PC), accounted for more than 84% of variance. The 1st PC is largely influenced by H, H,, H, H, and the nC,,/Phytane GC parameter, in the order given. The evaluation of the different parameters by PCA suggests that 1H NMR is more useful than GC to evaluate the degree of the chemical transformations of oil spills in soils

Organic co-solvent effect on the estimation of the equilibrium aqueous concentrations of oil residuals in Patagonian soil.

Determination of the equilibrium aqueous concentration and the distribution coefficients, K, in soil samples containing oil residuals of different age, was carried out using an organic co-solvent (methanol). It was found that the solvophobic theory could be applied for the interpretation of results. The behavior of the residuals turned out to be dependent on the co-solvent fraction and the age of the oil spill. The values of K vary between 900 (l kg(-1)) and 2,900 (l kg(-1)) showing a general and marked increase for residues of increasing age. The determined parameters are useful for the modeling of environmental impact on polluted soils.