Heavy and trace metal concentrations in three rockpool shrimp species (Palaemon elegans, Palaemon adspersus and Palaemon serratus) from Tenerife (Canary Islands)

Trace metal concentrations (Fe, Cu, Co, Zn, Ni and V) were investigated in three rockpool shrimp species (Palaemon elegans, Palaemon adspersus and Palaemon serratus) from six littoral sampling sites (polluted and non-polluted) of Tenerife in the Canary Islands (Central Eastern Atlantic), Spain. Sex ratio for all three species has been determined: females predominate over males in all species and significant differences in total length and cephalothorax length was detected between sexes, being females larger than males. By other side, concentrations of trace metals were determined in whole specimens. Higher mean values for every metal were observed in P. adspersus. In males, higher values were observed in P. elegans and P. serratus, whereas in P. adspersus, mean values are higher in females. Finally, mean concentrations of trace metals studied were higher, in general terms, in the two clearly polluted stations: Santa Cruz of Tenerife commercial harbour and its fishery dock dependency.     

Characterization of the olfactory impact around a wastewater treatment plant: Optimization and validation of a hydrogen sulfide determination procedure based on passive diffusion sampling

A monitoring program based on an indirect method was conducted to assess the approximation of the olfactory impact in several wastewater treatment plants (in the present work, only one is shown). The method uses H₂S passive sampling using Palmes-type diffusion tubes impregnated with silver nitrate and fluorometric analysis employing fluorescein mercuric acetate. The analytical procedure was validated in the exposure chamber. Exposure periods of at least 4 days are recommended. The quantification limit of the procedure is 0.61 ppb for a 5-day sampling, which allows the H₂S immission (ground concentration) level to be measured within its low odor threshold, from 0.5 to 300 ppb. Experimental results suggest an exposure time greater than 4 days, while recovery efficiency of the procedure, 93.0 ± 1.8%, seems not to depend on the amount of H₂S collected by the samplers within their application range. The repeatability, expressed as relative standard deviation, is lower than 7%, which is within the limits normally accepted for this type of sampler. Statistical comparison showed that this procedure and the reference method provide analogous accuracy. The proposed procedure was applied in two experimental campaigns, one intensive and the other extensive, and concentrations within the H₂S low odor threshold were quantified at each sampling point. From these results, it can be concluded that the procedure shows good potential for monitoring the olfactory impact around facilities where H₂S emissions are dominant.

Implications: Passive samplers are very attractive tools to experimentally tackle a number of air pollution problems, especially those related to odor impact. Their small size and cost permit a denser sampling design and thus a more detailed spatial characterization than other techniques. On the other hand, the large inherent variability in passive sampler measures requires an uncertainty analysis of the chemical species and analytical procedures used.     

Spain's greatest and most recent mine disaster

On 25 April 1998, the mineral waste retaining wall at the Swedish-owned pyrite mine at Aznalcóllar (Seville, Spain) burst, causing the most harmful environmental and socio-economic disaster in the history of the River Guadiamar basin. The damage was so great that the regional government decided in May 1998 to finance a comprehensive, multidisciplinary research initiative with the objective of eradicating or at least minimising all of the negative social, economic and environmental impacts. This paper utilises a Strengths, Weaknesses, Opportunities and Threats (SWOT) analysis to identify eight strategic measures aimed at providing policymakers with key guidelines on implementing a sustainable development model, in a broad sense. Empirical evidence, though, reveals that, to date, major efforts to tackle the negative impacts have centred on environmental concerns and that the socio-economic consequences have not been completely mitigated.     

Single-walled carbon nanotube behavior in representative mature leachate

Escalating production and subsequent incorporation of engineered nanomaterials in consumer products increases the likelihood of nanomaterials being discarded in landfills. Although direct measurement of particle disposal has not yet occurred, life cycle assessments suggest that over 50% of nanomaterials produced will eventually reside in landfills. Laboratory-scale experiments were conducted to evaluate how organics (humic acid: 20-800 mg/L), ionic strength (100-400 mM NaCl), and pH (6-8) typical of mature leachates influence carbon nanotube surface charge, relative stability, and mobility through representative solid waste environments. Results from the batch experiments suggest that the presence of high molecular weight organics, such as humic acid, acts to stabilize carbon nanotubes present in leachate, even at high ionic strengths (>100 mM NaCl). These results also suggest that in mature landfill leachate, as long as humic acid is present, ionic strength (when represented as NaCl) will be a dominant factor influencing nanomaterial stability. Column experiment results indicate the carbon nanotubes may be mobile through solid waste, suggesting particle placement within landfills needs to be examined more closely.     

Influence of soil texture on the distribution and availability of 238U, 230Th, and 226Ra in soils

The influence of soil texture on the distribution and availability of (238)U, (230)Th, and (226)Ra in soils was studied in soil samples collected at a rehabilitated uranium mine located in the Extremadura region in south-west Spain. The activity concentration (Bqkg(-1)) in the soils ranged from 60 to 750 for (238)U, from 60 to 260 for (230)Th, and from 70 to 330 for (226)Ra. The radionuclide distribution was determined in three soil fractions: coarse sand (0.5-2mm), medium-fine sand (0.067-0.5mm), and silt and clay (<0.067 mm). The relative mobility of the natural radionuclides in the different fractions was studied by comparison of the activity ratios between radionuclides belonging to the same radioactive series. The lability of these radionuclides in each fraction was also studied through selective extraction from the soils using a one-step sequential extraction scheme. Significant correlations were found for (238)U, (230)Th, and (226)Ra between the activity concentration per fraction and the total activity concentration in the bulk soil. Thus, from the determination of the activity concentration in the bulk soil, one could estimate the activity concentration in each fraction. Correlations were also found for (238)U and (226)Ra between the labile activity concentration in each fraction and the total activity concentration in bulk soil. Assuming that there is some particle-size fraction that predominates in the process of soil-to-plant transfer, the parameters obtained in this study should be used as correction factors for the transfer factors determined from the bulk soil in previous studies.     

The ability of Helianthus annuus L. and Brassica juncea to uptake and translocate natural uranium and 226Ra under different milieu conditions

Seedlings of Helianthus annuus L. (HA) and Brassica juncea (BJ) were used to test the effect of the pH, the presence of phosphates, and the addition of ethylene-diamine-tetraacetic acid (EDTA) or citrate on the uptake and the translocation of uranium isotopes ((238)U, (235)U, and (234)U) and (226)Ra. The results indicated that the presence of phosphates generally reduces the uptake and transfer of uranium from the roots to the shoots of HA. In the case of BJ, while phosphate enhanced the retention of uranium by roots, the translocation was poorer. Likewise, for (226)Ra, the best translocation was in the absence of phosphates for both species. The addition of citrate increased the translocation of uranium for both species, but had no clear effect on the transfer of (226)Ra. The effect of EDTA was much more moderate both for uranium and for (226)Ra, and for both plant species. Only noticeable was a slightly better uptake of (226)Ra by BJ at neutral pH, although the translocation was lower.     

Behavior, distribution and variability of surface ozone at an arid region in the south of Iberian Peninsula (Seville, Spain)

In order to improve our knowledge of the surface ozone in the south of the Iberian Peninsula, annual, monthly, weekly and daily ozone concentrations have been closely monitored in the Seville metropolitan area highlighting those episodes that exceed the European Ozone Directive. A three-year period (2003-2005) and eight ozone stations were used; five of them located in the city's busiest areas and the rest in adjacent zones ( approximately 25km). In addition, the wind regime was also studied in order to understand the main characteristics of the surface atmospheric dynamics. The lowest ozone concentrations 17-33microgm(-3) took place in January while the highest 57-95microgm(-3) occurred in June. The ozone concentration week-weekend differences from May to September indicate that this phenomenon does not affect the ozone stations analysed. Daily cycles show minimum values between 7:00 and 8:00 UTC and maximum at noon, exceeding 90microgm(-3) during summer months. From March to October the ozone concentrations were above the target value for the protection of human health, especially during the summer months, with values up to 30% over the limit. The information threshold has been exceeded at all ozone stations studied but with greater frequency in the stations far from the city centre. In addition, at these latter stations the alert threshold was also exceeded on six occasions. This study in the city of Seville indicates that the high ozone levels are due to local atmospheric effects, mainly since the ozone air masses may undergo recirculation processes. The ozone is transported to the city from the S-SW, having a major impact in the NE areas.     

Fish recruitment prediction, using robust supervised classification methods

Improving our ability to predict recruitment is a key element in fisheries management. However, the interactions between population dynamics and different environmental factors are complex and often non-linear, making it difficult to produce robust predictions. ‘Machine-learning’ techniques (in particular, supervised classification methods) have been proposed as useful tools, to overcome such difficulties. In this study, a methodology is proposed to build a robust classifier for fish recruitment prediction with sparse and noisy data. The methodology consists of 4 steps: (1) a semi-automated recruitment discretization method; (2) supervised discretization of predictors; (3) multivariate and non-redundant predictors selection; (4) learning a probabilistic classifier. In terms of fisheries management, the classifier estimated performance has important consequences and, to be useful, the manager needs to know the risk that is being taken when using this number. Probabilistic classifiers such as ‘naive Bayes’, have the advantage that, in addition to the predictions, estimate also the probability of each possible outcome. Anchovy (Engraulis encrasicolus) and hake (Merluccius merluccius) recruitments are used as application examples. ‘Two-intervals’ recruitment discretization accomplishes 70% accuracies and Brier scores of around 0.10, for both anchovy and hake recruitment. In comparison, ‘three-intervals’ recruitment discretization accomplishes 50% accuracies; and Brier scores of around 0.25 for anchovy and 0.30 for hake recruitment. These statistics are the result of validating not only the classifier, but also the previous steps, as a whole methodology.