Study of Meteorological Aspects and Urban Concentration of SO2 in Atmospheric Environment of La Plata, Argentina

This article presents and discusses SO₂ (ppbv) concentration measurements combined with meteorological data (mainly wind speed and direction) for a five-year campaign (1996 to 2000), in a site near an oil refinery plant close to the city of La Plata and surroundings (aprox. 740.000 inh.), considered one of the six most affected cities by air pollution in the country. Since there is no monitoring network in the area, the obtained results should be considered as medium term accumulated data that enables to determine trends by analyzing together gas concentrations and meteorological parameters. Preliminary characterization of the behaviour of the predominant winds of the region in relation with potential atmospheric gas pollutants from seasonal wind roses is possible to carry out from the data. These results are complemented with monthly averaged SO₂ measurements. In particular, for year 2000, pollutant roses were determined which enable predictions about contamination emission sources. As a general result we can state that there is a clear increase in annual SO₂ concentration and that the selected site should be considered as a key site for future survey monitoring network deployment. Annual SO₂ average concentration and prevailing seasonal winds determined in this work, together with the potential health impact of SO₂ reveals the need for a comprehensive and systematic study involving particulate matter an other basic pollutant gases.     

A study of the distribution of lead, cadmium and copper between water and kaolin, bentonite and a river sediment

Experiments were carried out to monitor the equilibrium distribution of lead, cadmium and copper between an aqueous phase modelling natural water and a solid phase modelling natural sediment, under varying conditions. The aqueous phase was analysed using ETAAS and differential pulse anodic stripping voltammetry (DPASV), whereas XRD and FTIR were used to study the solid phase. Sorption isotherms at constant pH were measured. Conditional distribution constants were calculated as functions of the pH, the time of equilibration and the amount of solid material. The results obtained stress the need for standardization of the approaches to the study of water-sediment interactions in order to be able to evaluate and compare the extensive data from field measurements and to predict these interactions.     

Improvement of the BCR three step sequential extraction procedure prior to the certification of new sediment and soil reference materials

The Standards, Measurements and Testing Programme (formerly BCR) of the European Commission proposed a three-step sequential extraction procedure for sediment analysis, following extensive expert consultations and two interlaboratory studies. This scheme was recently used to certify the extractable trace element contents of a sediment reference material (CRM 601). Although this procedure offers a means to ensure the comparability of data in this field, some difficulties concerning the interlaboratory reproducibility still remain, and a new project is currently being conducted to determine the causes of poor reproducibility in the extraction scheme. The final objective of the project is the certification of new sediment and soil reference materials for their extractable contents of Cd, Cr, Cu, Ni, Pb and Zn. This paper presents the results of a small-scale interlaboratory study, which aimed to test a revised version of the extraction schemes by comparing the original and the modified protocols using the CRM 601 sample. This work offers an improvement to the BCR sequential extraction procedure through intercomparison exercises. This improved procedure will allow the obtaining of CRMs to validate analytical data in the analysis of soils and sediments, and it will also facilitate comparability of data in the European Union.     

Atrazine and Alachlor Inputs to Surface and Ground Waters in Irrigated Corn Cultivation Areas of Castilla-Leon Region, Spain

The inputs of atrazine and alachlor herbicides to surface and ground waters from irrigated areas dedicated to corn cultivation in the Castilla-León (C-L) region (Spain) as related to the application of both herbicides were studied. Enzyme-linked immunosorbent assays (ELISA) were used for monitoring the atrazine and alachlor concentrations in 98 water samples taken from these areas. Seventy-nine of the samples were of ground waters and 19 were of surface waters. The concentration ranges of the herbicides detected in the study period (October 1997–October 1998) were 0.04–25.3 g L^–1 in the surface waters and 0.04–3.45 g L^–1 in the ground waters for atrazine, and 0.06–31.9 g L^–1 in the surface waters and 0.05–4.85 g L^–1 in the ground waters in the case of alachlor. The highly significant correlation observed between the concentrations of both herbicides in the surface waters (r = 0.89, p < 0.001) pointed to a parallel transport of atrazine and alachlor to these waters. A study was made of the temporal evolution of the concentrations of both herbicides, and it was found a maximum recharge of atrazine in the ground waters for April 1998 and of alachlor in October 1997 and October 1998. The temporal evolution of the concentrations of both herbicides in surface waters was parallel. The highly significant correlations observed between atrazine concentrations determined by ELISA and by HPLC (r = 0.92, p < 0.001) and between alachlor concentrations also determined by both methods (r = 0.96, p < 0.001) confirmed the usefulness of ELISA for monitoring both herbicides in an elevated number of samples. Using HPLC, the presence in some waters of the alachlor ethanesulfonate (ESA) metabolite was found at a concentration range of 0.52–4.01 g L^–1. However the interference of ESA in the determination of alachlor by ELISA was negligible. The inputs of atrazine and alachlor to waters found in this study, especially the inputs to ground waters, could pose a risk for human health considering that some waters, though sporadically, are even used for human consumption.     

IMPACTS OF VISITORS ON SOIL AND VEGETATION OF THE RECREATIONAL AREA “NACIMIENTO DEL RÍO MUNDO” (CASTILLA-LA MANCHA, SPAIN)

This study examines the effects of recreational use on the soil and vegetation at a site of ecological importance (Nacimiento del Río Mundo, Albacete, Spain). The most visited sites showed increased soil compaction of approximately 50%, bare ground increase to 61 ± 10% and a decrease in richness (from 25 ± 2 to 15 ± 2 species), diversity (from 4.0 ± 0.1 to 2.7 ± 0.4) and stratification of plant species (from 80 ± 11 to 21 ± 4%). The most visited sites had 90% less plant species as compared to the least visited. Intense use was associated with the presence of nitrophilous plant and vegetal species with a morphology adapted to heavy trampling. The recreational areas showed a distribution pattern of impact radiating outwards from the most used and degraded point. At the most visited point, Los Chorros (the spring of the river), the impact radiated outwards for about 20 m. A pilot experiment examining the effects of one-year restriction to visitors for access to a formerly impacted area showed a plant cover increase by anthropic and not by native species of 57 percent units.     

Assessment of Metal Contamination in Doñana National Park (Spain) using Crayfish (Procamburus Clarkii)

Water quality assessment in the Aznalcollar area was attempted using multivariate methods based on heavy metal concentrations in red swamp crayfish (Procamburus clarkii). Trace levels of four heavy metals, copper (Cu), zinc (Zn), cadmium (Cd) and lead (Pb), were detected in crayfish from eleven different stations. Principal component analysis (PCA) highlighted a gradient of contamination between the sampling stations. Cluster analysis (CA) distinguished three groups of stations. Discriminant analysis also differentiated three groups. The group centroids of the first discriminant function were used to devise an index that varies according to the source of the crayfish. These standardized values are proposed for use as a water quality index. The ability of this index to successfully predict environmental quality was proved with random samples.