Prediction of ozone concentrations in Oporto city with statistical approaches

The performance of three statistical methods: time-series, multiple linear regression and feedforward artificial neural networks models were compared to predict the daily mean ozone concentrations. The study here reported was based on data from one urban site with traffic influences and one rural background site. The studies were performed for the year 2002 and the respective four trimesters separately. In the multiple linear regression and feedforward artificial neural network models, the concentrations of ozone, the concentrations of its precursors (nitrogen oxides) and some meteorological variables for one and two days before the prediction day were used as predictors. For the application of these models in the validation step, the inputs of ozone concentration for one and two days before were replaced by the ozone concentrations predicted by the models. The results showed that time-series modelling was not profitable. In the development step, similar performances were obtained with multiple linear regression and feedforward artificial neural network. Better performance indexes were achieved with feedforward artificial neural network models in validation step. Concluding, feedforward artificial neural network models were more efficient to predict ozone concentrations.     

Organochlorine contaminants in complete clutches of Morelet's crocodile (Crocodylus moreletii) eggs from Belize

Seven complete clutches of Morelet's crocodile (Crocodylus moreletii) eggs were collected in northern Belize and examined for organochlorine (OC) pesticide residues. The primary OC detected, p,p-DDE, was found in every egg analyzed (n=175). Other OCs detected included p,p-DDT, p,p-DDD, methoxychlor, aldrin, and endosulfan I. Concentrations of individual OCs ranged from 4 ppb (ng chemical/g egg wet weight) to greater than 500 ppb. A statistical evaluation of p,p-DDE levels in three complete clutches was used to derive the minimum number of eggs needed from a clutch to precisely determine the mean p,p-DDE concentration representative of that clutch. Sample sizes of 8 (80% confidence level) and 11 (90% confidence level) were determined to yield an accurate estimate of contaminant levels in a full clutch of eggs. The statistically recommended sample size of 11 eggs (at 90% confidence level) was successfully tested on the four additional clutches.     

In situ and laboratory bioassays using Poecilia reticulata Peters, 1859 in the biomonitoring of an acidic lake at Camaçari, BA, Brazil

The suitability and viability of acute in situ bioassays were investigated in the biomonitoring program of an acidic lake contaminated with sulphur residues. Responses of organisms observed in laboratory and in situ bioassays were also assessed to determine whether or not they were similar and comparable, regarding accuracy and precision. Newborn Poecilia reticulata were employed as test organisms and exposed to the same water samples under in situ and laboratory conditions. Mortality/immobility was the endpoint assessed and dead/immobile organisms were counted at various time intervals during exposure. The mean calculated LT50 values and 95% confidence intervals were 1.61 (1.36-1.87) h in the laboratory bioassays and 0.72 (0.55-0.89) h in the in situ bioassays. Statistical comparison of these values revealed a significant difference (p<0.05). In situ bioassays were more accurate than those carried out in the laboratory, demonstrating higher sensitivity and better reproduction of what occurs in nature, while laboratory bioassays were more precise.     

Passive air sampler as a tool for long-term air pollution monitoring: Part 1. Performance assessment for seasonal and spatial variations

The potential of passive air sampling devices (polyurethane foam disks) to assess the influence of local sources on the quality of the surrounding environment was investigated. DEZA Valasske Mezirici, a coal tar and mixed tar oils processing plant, and Spolana Neratovice, a chemical factory with the history of high production of organochlorinated pesticides (OCPs), were selected as the point sources of PAHs, and OCPs, respectively. Levels of PCBs, OCPs and PAHs were determined for all sampling sites and sampling periods. The study brought useful data about the air concentrations of POPs in the investigated regions. More important, it provided information on the transport and fate of POPs in the vicinity of local sources of contamination useful for the estimation of their influence. Very good capability of passive samplers to reflect temporal and spatial fluctuation in concentrations of persistent organic pollutants in the ambient air was confirmed which makes them applicable for monitoring on the local scale.     

Effects of ultraviolet radiation and contaminant-related stressors on arctic freshwater ecosystems

Climate change is likely to act as a multiple stressor, leading to cumulative and/or synergistic impacts on aquatic systems. Projected increases in temperature and corresponding alterations in precipitation regimes will enhance contaminant influxes to aquatic systems, and independently increase the susceptibility of aquatic organisms to contaminant exposure and effects. The consequences for the biota will in most cases be additive (cumulative) and multiplicative (synergistic). The overall result will be higher contaminant loads and biomagnification in aquatic ecosystems. Changes in stratospheric ozone and corresponding ultraviolet radiation regimes are also expected to produce cumulative and/or synergistic effects on aquatic ecosystem structure and function. Reduced ice cover is likely to have a much greater effect on underwater UV radiation exposure than the projected levels of stratospheric ozone depletion. A major increase in UV radiation levels will cause enhanced damage to organisms (biomolecular, cellular, and physiological damage, and alterations in species composition). Allocations of energy and resources by aquatic biota to UV radiation protection will increase, probably decreasing trophic-level productivity. Elemental fluxes will increase via photochemical pathways.     

Modelling the extra and intracellular uptake and discharge of heavy metals in Fontinalis antipyretica transplanted along a heavy metal and pH contamination gradient

Samples of the aquatic bryophyte Fontinalis antipyretica Hedw. were transplanted to different sites with the aim of characterizing the kinetics of the uptake and discharge of heavy metals in the extra and intracellular compartments. The accumulation of metals in extracellular compartments, characterized by an initial rapid accumulation, then a gradual slowing down over time, fitted perfectly to a Michaelis-Menten model. The discharge of metals from the same compartment followed an inverse linear model or an inverse Michaelis-Menten model, depending on the metal. In intracellular sites both uptake and discharge occurred more slowly and progressively, following a linear model. We also observed that the acidity of the environment greatly affected metal accumulation in extracellular sites, even when the metals were present at relatively high concentrations, whereas the uptake of metals within cells was much less affected by pH.     

The combined use of chemical and biochemical markers to assess water quality along the Ebro River

Carp (Cyprinus carpio) and barbel (Barbus graellsii) were collected from five sites along the Ebro River. The study was designed to assess levels of persistent organic pollutants and metals bioaccumulated by fish, and some biochemical responses (cytochrome P450 system, phase II activities, and metallothioneins) against those pollutants. The highest levels of PCBs and DDTs were detected in carp from industrialised areas, which also showed high levels of mercury and cadmium in the liver, and high levels of nonylphenol in bile. Significant alterations in some biochemical markers were observed and associated to combined exposure to pollutants. The activity 7-ethoxyresorufin O-deethylase ranged from 69 pmol/min/mg protein in carp from the reference site to 415 pmol/min/mg protein in those from polluted sites. Carp from the Ebro Delta, an agricultural area, had depressed acetylcholinesterase in muscle tissue. Metallothionein concentrations were positively correlated with copper residues, but no significant differences among sampling points were observed.     

Increased thyroid volume and frequency of thyroid disorders signs in schoolchildren from nitrate polluted area

Thyroid volume (ThV) and echogenicity by ultrasound were estimated in 324 schoolchildren (aged between 10 and 13-years) from high nitrate area (HNA) located in agricultural lowland with high nitrate drinking water supply (51-274 mg/l) from shallow wells. The data were compared to children of the same age from low nitrate area (LNA) consisting of 168 children from the neighboring area with very low nitrate (< 2 mg/l) drinking water and of 596 children from the city of Kosice located in a vicinity of LNA and also supplied by low nitrate water. Blood samples were obtained from 315 willing children from HNA and 109 children from LNA and the levels of thyrotropin (TSH), total thyroxine (TT4), free triiodothyronine (FT3) and thyroperoxidase antibodies (anti-TPO) in serum were determined. ThV (mean +/- SE) in 10-year (5.10 +/- 0.14 ml) and 13-year (5.97 +/- 0.11 ml) old children from HNA was significantly higher than that in two groups of respective age from LNA, 4.58 +/- 0.17 (p < 0.02) and 5.23 +/- 0.15 ml (p < 0.05), and from the city of Kosice, 4.77 +/- 0.10 ml (p < 0.05) and 4.87 +/- 0.1 0ml (p < 0.0001). The frequency of hypoechogenicity in HNA was also significantly higher than that in pooled LNA plus Kosice, 13.7% vs. 4.7% (p < 0.01) in 10-year and 10.6% vs. 5.7% (p < 0.03) in 13-year, respectively. The frequency of TSH level in the range of subclinical hypothyroidism (> 4.0 mU/l) in pooled age groups from HNA was 13/324 (4.0%) and that of positive anti-TPO was 8/324 (2.5%), while no case of either increased TSH or positive anti-TPO was found in 109 children from LNA. Finally, no differences in the levels of TT4 and FT3 were found between HNA and LNA. It was concluded that long-term exposure to high nitrate intake by drinking water and home made meals from local products results in increased thyroid volume and increased frequency of signs of subclinical thyroid disorders (thyroid hypoechogenicity by ultrasound, increased TSH level and positive anti-TPO).     

The composition and relationships between trace element levels in inhalable atmospheric particles (PM10) and in leaves of Nerium oleander L. and Lantana camara L

In order to evaluate the composition of inhalable atmospheric particles and to study the relationship between trace element levels in PM10 and in leaves of two plant species, the amount of Ba, Cu, Fe, Mn, Pb, Ti and V were analysed in PM10 and in Nerium oleander L. and Lantana camara L. leaves from two sites in the city of Seville and one remote control site. In PM10, the Cu and Fe content was significantly lower (p<0.05) in the control site than in the other sites. No correlations between leaf content and air content were found for the elements in L. camara. On the contrary, positive and significant correlations (p<0.05) were found between leaf content of N. oleander and PM10 content for Cu and Fe. The data suggest that N. oleander can be used in atmospheric biomonitoring studies, because it is especially useful for Cu and Fe, N. oleander being a better indicator than L. camara.     

Tradescantia micronucleus test indicates genotoxic potential of traffic emissions in European cities

Urban atmospheres contain complex mixtures of air pollutants including mutagenic and carcinogenic substances such as benzene, diesel soot, heavy metals and polycyclic aromatic hydrocarbons. In the frame of a European network for the assessment of air quality by the use of bioindicator plants, the Tradescantia micronucleus (Trad-MCN) test was applied to examine the genotoxicity of urban air pollution. Cuttings of Tradescantia clone #4430 were exposed to ambient air at 65 monitoring sites in 10 conurbations employing a standardised methodology. The tests revealed an elevated genotoxic potential mainly at those urban sites which were exposed to severe car traffic emissions. This bioassay proved to be a suitable tool to detect local 'hot spots' of mutagenic air pollution in urban areas. For its use in routine monitoring programmes, however, further standardisation of cultivation and exposure techniques is recommended in order to reduce the variability of results due to varying environmental conditions.