Trimethylamine abatement in algal-bacterial photobioreactors

Trimethylamine (TMA) is an odorous volatile organic compound emitted by industries. Algal-based biotechnologies have been proven as a feasible alternative for wastewater treatment, although their application to abate polluted air emissions is still scarce. This work comparatively assessed the removal of TMA in a conventional bacterial bubble column bioreactor (BC) and a novel algal-bacterial bubble column photobioreactor (PBC). The PBC exhibited a superior TMA abatement performance compared to the conventional BC. In this sense, the BC reached a removal efficiency (RE) and an elimination capacity (EC) of 78% and 12.1 g TMA m^?3 h^?1, respectively, while the PBC achieved a RE of 97% and a EC of 16.0 g TMA m^?3·h^?1 at an empty bed residence time (EBRT) of 2 min and a TMA concentration ~500 mg m^?3. The outstanding performance of the PBC allowed to reduce the operating EBRT to 1.5 and 1 min while maintaining high REs of 98 and 94% and ECs of 21.2 and 28.1 g m^?3·h^?1, respectively. Moreover, the PBC improved the quality of the gas and liquid effluents discharged, showing a net CO₂ consumption and decreasing by ~ 30% the total nitrogen concentration in the liquid effluent via biomass assimilation. A high specialization of the bacterial community was observed in the PBC, Mumia and Aquamicrobium sp. being the most abundant genus within the main phyla identified.

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Evaluation of the effect on arthropod populations by using deltamethrin to control Phloeotribus scarabaeoides Bern. (Coleoptera: Scolytidae) in olive orchards

Field tests were made for the control of an olive insect pest, the olive bark beetle, Phloeotribus scarabaeoides (Col: Scolytidae), using the pyrethroid insecticide deltamethrin (D) and this insecticide combined with ethylene (D+E), an attractant of the olive bark beetle. The tests were run in olive orchards in the provinces of Granada and Jaén (Andalusia, southern Spain), treating several olive rows so as to create a barrier effect to control the pest attack. The main objective was to evaluate the arthropod fauna affected by these treatments. The different taxa captured have been separated in three different trophic groups: parasitoids, predators and phytophagous. A knock-down effect was found during the first dates in all the functional groups in all cases. The results showed the following trend in arthropod abundance: D+E>D>C. This trend was significant (p<0.05) for predators and phytophagous insects in both zones. The parasitoids of Prays oleae (Lep.: Plutellidae), a major olive pest, were most affected by the treatments, together with several groups of predators such as ants, cantharids, coccinellids and mirids. Data from the captures show the need to determine the optimum time for insecticide application in order to minimise its effect on beneficial insect populations.     

Sources and concentrations of indoor nitrogen dioxide in Barcelona, Spain

Sources and concentrations of indoor nitrogen dioxide (NO2) were examined in Barcelona, Spain, during 1996-1999. A total of 340 dwellings of infants participating in a hospital-based cohort study were selected from different areas of the city. Passive filter badges were used for indoor NO2 measurement over 7-30 days. Dwelling inhabitants completed a questionnaire on housing characteristics and smoking habits. Data on outdoor NO2 concentrations were available for the entire period of the study in the areas of the city where indoor concentrations were determined. Bivariate analysis was performed to investigate relationships between indoor NO2 concentrations on one hand and outdoor NO2 concentrations, housing, and occupant characteristics on the other. Stepwise multiple linear regression was performed with variables that were found to have a significant bivariate relationship. Indoor NO2 mean values ranged between 23.57 ppb in 1996 and 27.02 ppb in 1999, with the highest yearly value of 27.82 ppb in 1997. In the same time period, mean outdoor NO2 concentration ranged between 25.26 and 25.78 ppb with a peak of 30.5 ppb in 1998. Multiple regression analysis showed that principal sources of indoor NO2 concentrations were the use of a gas cooker, the absence of an extractor fan when cooking, and cigarette smoking. The absence of central heating was also associated with higher NO2 concentrations. Finally, each ppb increase in outdoor NO2 was associated with a 1% increase in indoor concentrations.     

Optimizing microwave-assisted solvent extraction (MASE) of pesticides from soil

Microwave-assisted solvent extraction (MASE) was investigated as an alternative for extraction of parathion (O,O-diethyl O-4-nitrophenyl phosphorothioate), methyl parathion (O,O-dimethyl O-4-nitrophenyl phosphorothioate), p,p'-DDE [1,1'-dichloro-2,2-bis(4-chlorophenyl)ethane], hexachlorobenzene (HCB), simazine (6-chloro-N2,N4-diethyl- 1 ,3,5-triazine-2,4-diamine) and paraquat dichoride (1,1'-dimethyl-4,4'-bipyridinium) from two different soils and from an earthworm-growing substrate. The matrices were fortified with 14C-radiolabeled pesticides and extracted with various solvent systems under different microwave conditions. Recoveries of more than 80% could be obtained depending on the used microwave conditions and solvent, except for paraquat whose recovery was generally less efficient. Thus, MASE can be successfully used to extract pesticides from environmental and biological samples and could be a viable alternative to conventional extraction methods. The technique uses smaller amounts of organic solvents, thereby minimizing the costs of the analysis and the disposal of waste solvent.     

Micro-spatial variation of soil metal pollution and plant recruitment near a copper smelter in Central Chile

Soil chemical changes produced by metal smelters have mainly been studied on a large scale. In terms of plant survival, determination of small scale variability may be more important because less toxic microhabitats may represent safe sites for successful recruitment and thus for plant survival. Three dominant microhabitats (open spaces and areas below the canopy of Sphaeralcea obtusiloba and Baccharis linearis shrubs) were defined in a heavily polluted area near a copper smelter and characterised in terms of microclimate, general soil chemistry, total and extractable metal concentrations in the soil profile (A0 horizon, 0-5 and 15-20 cm depth), and seedling densities. Results indicated a strong variability in microclimate and soil chemistry not only in the soil profile but also among microhabitats. Air/soil temperatures, radiation and wind speed were much lower under the canopy of shrubs, particularly during the plant growth season. Soil acidification was detected on top layers (0-5 cm depth) of all microhabitats while higher concentrations of N, Cu and Cd were detected on litter and top soil layers below shrubs when compared to open spaces; however, high organic matter content below shrubs decreased bioavailability of metals. Plant recruitment was concentrated under shrub canopies; this may be explained as a result of the nursery effect exerted by shrubs in terms of providing a more favourable microclimate, along with better soil conditions in terms of macronutrients and metal bioavailability.     

The effects of a basic effluent on macroinvertebrate community structure in a temporary Mediterranean river

Macroinvertebrate communities and environmental variables were assessed seasonally for 1 year in a temporary river in South Portugal receiving an effluent with high conductivity, pH, sulphates, nitrates and low oxygen content. The usefulness of the ordination method canonical correspondence analysis (CCA) and the classification method cluster analysis (UPGMA) were examined to evaluate the perturbation. Macroinvertebrate samples were segregated along the first ordination axis by CCA, which in turn correlated with sulphates and nitrates. CCA produced a two-dimensional distribution of sites similar to the grouping formed by cluster analysis. In general, three or four groups were distinguished. Immediately downstream of the effluent discharge point, only taxa tolerant to low oxygen, high pH and high sulphate and nitrate concentrations were present. Further downstream, sites had a community similar to the reference sampling locations. During flowing conditions the CCA ordination axis 1 was also correlated with several classic measures of water quality (i.e. taxon richness, diversity and biotic indices). In other periods, only the percentage of Ephemeroptera, Plecoptera and Trichoptera (%EPT) and the ratio EPT/(Chironomidae + EPT) were significantly correlated with CCA axis one. This suggests that ordination methods outperform benthic indices in detecting pollution during low flows and segregated polluted from clean/recovered sites in all periods.     

Online hourly determination of 62 VOCs in ambient air: system evaluation and comparison with another two analytical techniques

This paper presents results of the processing and validation of data collected by an automatic gas chromatograph (AGC). This system was used to monitor 62 volatile organic compounds (VOCs) in urban air in the Basque Country, Spain. The nonpolar compounds (C2-C10) identified-paraffins, olefins, aromatics, and chlorinated compounds-accounted for 88% of the mass of total non-methane hydrocarbons (TNMHCs) in ambient air. The evaluation of linearity, precision, detection limits (DLs), and stability of retention times (RTs) indicates that the equipment is suitable for measuring ambient air automatically for prolonged periods (6 months). The calibration of the equipment using response factors calculated on the basis of the effective carbon number (ECN) showed variations of over 10% for acetylene, isoprene, and n-hexane. The results provided by the automatic chromatograph correlated significantly with simultaneous results from other widely used techniques for determining VOCs in ambient air: (1) portable GC, equipped with photoionization detector (PID), and (2) active adsorption on Tenax-TA followed by thermal desorption and chromatographic analysis.     

Interaction of limestone grains and acidic solutions from the oxidation of pyrite tailings

To characterise the coatings formed and to analyse element partitioning between the aqueous and solid phase, suspensions were prepared with four grain sizes of limestone and three different amounts of acidic solution from oxidized pyrite tailings. In all cases, red coatings with three different layers covered the grain surface, sealing off the acidic solution. The inner layer was composed mainly of basaluminite, the middle layer of schwertmannite, and the outer layer of gypsum and jarosite. Zn, Cd and Tl were co-precipitated by Fe and Al; As and Pb were co-precipitated almost completely by Fe; and Cu formed mainly Cu sulphates. All trace elements reached almost total precipitation at pH 6.3, but the precipitation of As and Pb tended to decrease as the pH rose. Consequently, liming should be calculated so that the soil pH does not exceed 6.3. This calculation should take into account that the armouring of the limestone grains can cause underestimations in the amount of liming material needed.     

Oxygen levels versus chemical pollutants: do they have similar influence on macrofaunal assemblages? A case study in a harbour with two opposing entrances

Generally, harbours are polluted zones characterised by low values of hydrodynamism and oxygen in the water column and high concentrations of pollutants in sediments. The harbour of Ceuta, North Africa, has an unusual structure; it is located between two bays connected by a channel, which increases the water movement and exchange in the harbour, maintaining moderate oxygen levels in the water-sediment interface. Nevertheless, high concentration of organic matter, nutrients and heavy metals were measured in sediments from this harbour. Under these unusual conditions (high levels of pollution but total saturation of oxygen in the water column) we studied the responses of soft-bottom macrobenthic communities using uni and multivariate analyses. The number of species was similar inside and outside the harbour but the species composition differed between internal and external stations; oxygen levels seem to control the "quantity" of species whereas pollutants control the "quality" of them.