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.     

Prenatal diagnosis of exencephaly

This paper presents a sonographic diagnosis of exencephaly made during the last trimester of gestation. The sonogram showed the absence of bones in the cranial vault together with the presence of a disorganized cerebral mass, with loss of its normal anatomy. Post-partum examination of the newborn confirmed the findings of the sonogram. We briefly review the characteristics of exencephaly, its aetiology, and its relationship to anencephaly.     

Strategically designed sample composition for fastest screening of polychlorinated biphenyl congeners in water samples

A new strategy for preparing composite samples of special interest and applicability in environmental screening studies is presented. The use of supersaturated experimental design matrices to conduct the sample composition of water sample specimens in screening studies is demonstrated. In contrast to well known conventional sample composition, this strategic approach provides analytical objects allowing the accurate prediction of analyte concentration levels in the original individual sample specimens while fixing the number of experiments to be carried out down to the very number of sample specimens. This will be of special importance when dealing with analytes that require complicated, labour intensive and expensive analytical processes. To reach this goal, two main conditions must be fulfilled. The first one is the sparsity effect (Pareto principle) which holds for the specimens in the sampling campaign. This means that the number of really anomalous or contaminated specimens, as compared to the total number of specimens to be analysed, is low. In environmental screening studies, frequently this situation can be reasonably assumed. The second condition is to have an effective manner to develop and solve the experimental designs required to build-up the composite samples. The challenging problem of screening PCBs in water samples has been tackled to show the usefulness of this strategic approach by combining chemometrically assisted sample composition and rapid analysis using solid-phase microextraction of the composite samples.     

Micro-evolutionary change in host response to a brood parasite

The relationship between brood parasites and their hosts is usually assumed to result in coevolution, and documentation of changes in extant populations should thus be possible. Here we describe how the ejection rate of eggs of an obligate brood parasite, the great spotted cuckoo Clamator glandarius, by its host, the magpie Pica pica, has recently increased in an area in southern Spain. The ejection rate of great spotted cuckoo eggs in naturally parasitized nests of the magpie increased at a rate of 0.5% year' during the period 1982–1992. This result was verified in a number of field experiments using nonmimetic and mimetic model eggs. The rate of increase in ejection rate was 4.7% year^-1 for mimetic eggs and 2.3% year^-1 for nonmimetic eggs. There were clear differences in parasitism by the great spotted cuckoo between study plots and years, which makes comparisons of rates of parasitism between areas difficult without considering temporal variation. The recent increase in the ejection response of magpies to great spotted cuckoo eggs was not due to magpies using the abundance of cuckoos as a cue to the intensity of parasitism.     

Direct measurements of urban OH reactivity during Nashville SOS in summer 1999

Emissions of volatile chemicals control the hydroxyl radical (OH), the atmosphere's main cleansing agent, and thus the production of secondary pollutants. Accounting for all of these chemicals can be difficult, especially in environments with mixed urban and forest emissions. The first direct measurements of the atmospheric OH reactivity, the inverse of the OH lifetime, were made as part of the Southern Oxidant Study (SOS) at Cornelia Fort Airpark in Nashville, TN in summer 1999. Measured OH reactivity was typically 11 s(-1). Measured OH reactivity was 1.4 times larger than OH reactivity calculated from the sum of the products of measured chemical concentrations and their OH reaction rate coefficients. This difference is statistically significant at the 1sigma uncertainty level of both the measurements and the calculations but not the 2sigma uncertainty level. Measured OH reactivity was 1.3 times larger than the OH reactivity from a model that uses measured ambient concentrations of volatile organic compounds (VOCs), NO, NO2, SO2, and CO. However, it was within approximately 10% of the OH reactivity from a model that includes hydrocarbon measurements made in a Nashville tunnel and scaled to the ambient CO at Cornelia Fort Airpark. These comparisons indicate that 30% of the OH reactivity in Nashville may come from short-lived highly reactive VOCs that are not usually measured in field intensive studies or by US EPA's Photochemical Assessment Monitoring Stations.