Dermal exposure to pesticides in greenhouses workers: discrimination and selection of variables for the design of monitoring programs

Dermal exposure to pesticides is one of the main sanitaryproblems which greenhouses workers face. With the dual aimsof establishing both the body part that receives the greatestexposure and the variable that has greatest influence on this exposure level, 22 pesticide application trials were performed. Trials were carried out in different greenhouse vegetable crops,using different pesticides and different spray diameters from the spray gun. In order to determine dermal exposure, the wholebody method was used. Pieces of the applicator suit were subject to an extraction procedure and their pesticide contentdetermined using GC-NPD analysis. Multivariate analysis were applied to the data obtained. Principal component analysis showed that all trials produced a high exposure level on lowerleft leg and lower right leg. Cluster analysis distinguished between three sample groups. The most and the least affectedparts were clearly distinguished. Discriminant analysis indicated that the thin drop size of the spray gun is responsible for both the differences between groups and the minimum or maximum exposure level measured on the applicatorsuit. Therefore, selecting the variables, lower legs and thindrop size, is considered fundamental in designing programs formonitoring pesticide exposure.     

Response of complex food webs to realistic extinction sequences

Although an ecosystem's response to biodiversity loss depends on the order in which species are lost, the extinction sequences generally used to explore such responses in food webs have been ecologically unrealistic. We investigate how several extinction orders affect the minimum number of secondary extinctions expected within pelagic food webs from 34 temperate freshwater lakes. An ecologically plausible extinction order is derived from the geographically nested pattern of species composition among the lakes and is corroborated by species' pH tolerances. Simulations suggest that lake communities are remarkably robust to this realistic extinction order and highly sensitive to the reverse sequence of species loss. This sensitivity is not well explained by the known sensitivity of networks to the loss of highly connected species but appears to be better explained by our observation that trophic specialists preferentially consume widely distributed species at low risk of extinction. Our results highlight an important aspect of community organization that may help to maintain biodiversity amidst changing environments.     

Planktonic ciliates in a hypertrophic pond: functional role and importance

Taxonomical composition and abundance of the planktonic ciliate assemblage in a Lake Tezozomoc, a hypertrophic pond located into an urban park in Mexico City, was investigated along the rainy season (May to October). The aims of the study were to know the main trophic roles and ecological significance of ciliates in a highly productive environment. A low number of taxa (27) and a wide abundance fluctuation (104-387 cil ml(-1)) were found. The most abundant species (up to 162 cil ml(-1)) was Halteria grandinella, an oligotrich ciliate that graze on bacteria and picoplankton, but also several big body sized species that feed on pico and nanoplankton were abundant. Sudden temporal changes in species dominance occurred. Ciliate biomass was very high and fluctuated widely (1.6-88 10(6) microm(3) ml(-1)) being dominated by the >50 microm size fraction that mainly included the pico and nanoplankton feeders. Ciliates are a very important component in the plankton of hypertrophic lakes and their main control factor seems to be the grazing by big-body size Daphnia species.     

PLS and PCR Methods in the Assessment of Coastal Water Quality

Partial least squares regression analysis (PLS) and principal component regression analysis (PCR) were examined asmethodological procedures for assessing the quality of coastalwaters in a tourist area. Four variables related to the trophicstate of waters, namely nitrate, nitrite, ammonia and phosphate were analyzed. The models resulting from PLS and PCR were verysimilar. Both defined three groups of water masses characterizedby different nutrient loadings. These groups were in accordancewith those obtained by numerical classification. The PLS methodwas selected as the optimal model, on the basis of its lowerprediction errors (lower Press and Rmsd values). For managementpurposes, this statistical model allows mesotrophic conditions,reflecting some nutrient enrichment over background conditions,to be characterized and the successful diagnosis of additionalsamples within this context.     

Guatemala strives for environmental and economic sustainability in the Rio Dulce region

Conditions in Guatemala's Rio Dulce National Park (RDNP) present an immediate decision-making challenge concerning the reversal of current destructive environmental trends, and in establishing policies for restoration, protection, and sustainable use. This article summarises results of environmental assessment activities undertaken at three levels: an environmental impact assessment (EIA) of a proposed industrial forestry activity, an environmental assessment of management options for the Rio Dulce National Park, and water management planning for the Rio Dulce/Lago Izabal watershed. A key result of the EIA was to prohibit construction of a barge terminal within the boundaries of the park because it could set a precedent for future development. Management options for the park focused on establishing land-use controls, dealing with river transport more effectively, and identifying funding mechanisms to implement solutions. At the watershed scale, a strategic approach was recommended to identify priority issues for initiating change toward sustainability in the region.     

Microbial oxygen uptake in sludge as influenced by compost physical parameters

The wide range of optimal values reported for the physical parameters of compost mixtures suggest that their interactive relationships should be investigated. The objective of this study was to examine the microbial O₂ uptake rate (OUR) in 16 sludge waste recipes, offering a range of moisture content (MC), waste/bulking agent (W/BA) ratio and BA particle size levels determined using a central composite experimental design. The 3 kg samples were maintained at a constant temperature and aeration rate for 28 days, during which a respirometer recorded O₂ uptake to provide a measure of microbial activity and biodegradability. The cumulative O₂ consumption after 14 and 28 days was found to be significantly influenced by MC, W/BA ratio, BA particle size and the interaction between MC and W/BA ratio (p < 0.05). Using multivariate regression analysis, the experimental data was used to generate a model with good predictive ability for cumulative O₂ consumption after 28 days as a function of the significant physical variables (R² = 0.84). The prediction of O₂ uptake by the model depended highly on the interaction between MC and W/BA ratio. A MC outside of the traditional 50–60% (wet basis) range still resulted in a high level of microbial O₂ uptake as long as the W/BA ratio was adjusted to maintain a suitable O₂ exchange in the sample. The evolution of OUR in the samples was also investigated, uncovering strong associations between short and long-term respirometric indices, such as peak OUR and cumulative O₂ consumption (p < 0.005). Combining peak OUR data with cumulative O₂ consumption after 14 days allowed for accurate predictions of cumulative O₂ after 28 days of aeration (R² = 0.96), implying that future studies need only run trials up to 14 days to evaluate the overall O₂ consumption or biodegradability of similar sludge mixtures.     

Vulnerability of human environment to risk: case of groundwater contamination risk

Based on a theoretical revision of the social vulnerability concept, this article proposes a scheme of vulnerability indicators within the human environment focused on different aetiology risks. An adaptation of this generic scheme of vulnerability factors is set for the specific field of aquifer contamination risk, as well as a methodology for its analysis. Finally, model application examples are given for the Sierra de Líbar and Sierra de Mijas carbonate aquifers and the Vélez River detrital aquifer, all of which are located in the south of Spain. Obtained cartography results show a range of utilities for risk mitigation and permit appropriate spatial discrimination for its performance over different scales. The exposure and vulnerability of the groundwater contamination risk concept is evaluated in specific maps, taking into account the resident population as well as their assets.