Air concentrations of PCDD/Fs, PCBs and PCNs using active and passive air samplers

The concentrations of polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) were determined in air samples collected at four sampling sites located in two zones of Barcelona (Spain): near a municipal solid waste incinerator (MSWI) and a combined cycle power plant (3 sites), and at a background/control site. Samples were collected using high-volume active samplers. Moreover, 4 PUF passive samplers were deployed at the same sampling points during three months. For PCDD/Fs, total WHO-TEQ values were 27.3 and 10.9 fg WHO-TEQm(-3) at the urban/industrial and the background sites, respectively. The sum of 7 PCB congeners and the Sigma PCN levels were also higher at the industrial site than at the background site. In order to compare active and passive sampling, the accumulated amounts of PCDD/Fs, PCBs and PCNs in the four passive air samplers, as well as the total toxic equivalents in each sampling site were also determined. To assess the use of PUF passive samplers as a complementary tool for PCDD/F, PCB and PCN monitoring, sampling rates were calculated in accordance with the theory of passive air samplers. PUF disks allowed establishing differences among zones for the POP levels, showing that they can be a suitable method to determine POP concentrations in air in areas with various potential emission sources. Although both particle and gas phase were sorbed by the PUFs, data of gas phase congeners are more reproducible.     

Application of fluorescence in situ hybridization technique to detect simazine-degrading bacteria in soil samples

We propose a new approach to evaluate the natural attenuation capacity of soil by using fluorescence in situ hybridization (FISH). A specific oligonucleotide probe AtzB1 was designed based on the sequence data of the atzB gene involved in the hydrolytic deamination of s-triazines; this gene, located in a multiple copy plasmid was detected by the optimized FISH protocol. Two agricultural soils (Lodi and Henares) with a history of simazine treatments, and two natural soils (Soto and Monza), without previous exposure to simazine, were studied. AtzB1 probe-target cells were found only in the agricultural soils and, in a greater percentage, in the Lodi soil, compared to the Henares one. Moreover, the greatest percentage of AtzB1 probe-target cells in Lodi was accompanied by a greater mineralization rate, compared to the Henares soil. The FISH method used in this study was suitable for the detection of simazine-degrading bacteria and could be a useful indicator of the potential of soil bioremediation.     

Evaluation of Cu-PPHs as active catalysts for the SCR process to control NOx emissions from heavy duty diesel vehicles

Copper based catalysts supported on mesoporous materials, which were in turn based on a surfactant expanded zirconium phosphate for the formation of silica galleries in the interlayer space, were prepared by the impregnation method. They were then characterised and tested in the selective catalytic reduction of NO with ammonia as active catalysts for the control of the NOx emissions from heavy duty vehicles. Copper catalysts displayed a high catalytic performance, even in the presence of 14% (v/v) of H2O and 100 ppm of SO2. They also displayed improved catalytic behaviour when compared to a CuZSM5 catalyst.     

Estimating the environmental impact of micro-pollutants in the low Ebro River (Spain): an approach based on screening toxicity with Vibrio fischeri

The aim of this study was to assess the likely impacts on the ecosystems due to agricultural, human, and industrial activities carried out in an ecologically important area of the Ebro River (Spain). For it, a screening site specific ecological risk assessment was conducted. Considering the presence of high levels of potentially toxic substances, such as metals and chlorinated organic compounds, aqueous and organic extracts were used to assess toxicity in sediments by using the photo-luminescent bacteria Vibrio fischeri (Microtox) as screening response variable. Sediment samples collected during 2005-2006 in the last course of the Ebro River and its Delta have been analyzed. Toxic responses have shown strong relationships to the levels of pollutants in the area. Moreover, various sites presented some toxicity level, probably because of other factors associated with reducing environments into the sediments. Results indicate that Microtox bioassay is an appropriate tool to perform risk assessment studies at screening level.     

Soil vapor extraction in sandy soils: influence of airflow rate

Airflow rate is one of the most important parameters for the soil vapor extraction of contaminated sites, due to its direct influence on the mass transfer occurring during the remediation process. This work reports the study of airflow rate influence on soil vapor extractions, performed in sandy soils contaminated with benzene, toluene, ethylbenzene, xylene, trichloroethylene and perchloroethylene. The objectives were: (i) to analyze the influence of airflow rate on the process; (ii) to develop a methodology to predict the remediation time and the remediation efficiency; and (iii) to select the most efficient airflow rate. For dry sandy soils with negligible contents of clay and natural organic matter, containing the contaminants previously cited, it was concluded that: (i) if equilibrium between the pollutants and the different phases present in the soil matrix was reached and if slow diffusion effects did not occur, higher airflow rates exhibited the fastest remediations, (ii) it was possible to predict the remediation time and the efficiency of remediation with errors below 14%; and (iii) the most efficient remediation were reached with airflow rates below 1.2 cm(3)s(-1) standard temperature and pressure conditions.     

Concentrations of PCDD/PCDFs in plasma of subjects living in the vicinity of a hazardous waste incinerator: follow-up and modeling validation

In 2007, the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDFs) were determined in plasma of non-occupationally exposed subjects living near the only hazardous waste incinerator (HWI) in Spain (Constantí, Tarragona County, Catalonia). These data were compared with the levels found in two previous surveys performed in 1998 (baseline) and 2002. The current mean PCDD/PCDF concentration in plasma was 9.36pg I-TEQg(-1) of lipid (range: 1.76-23.44pg I-TEQg(-1) of lipid). It means a significant reduction of the mean PCDD/PCDFs levels in plasma in comparison to the concentrations found in 1998 and 2002 (27.01 and 15.70pg I-TEQg(-1) of lipid, respectively). This important decrease agrees well with the notable reduction in the dietary intake of PCDD/PCDFs recently noted for the population of the same area (210.1pg I-TEQd(-1), 63.8pgWHO-TEQd(-1), and 27.8pgWHO-TEQd(-1), in 1998, 2002 and 2007, respectively). The current data were also used to predict theoretical PCDD/PCDF concentrations in plasma by executing a single-compartment empirically-based pharmacokinetic model on the basis of the daily intake of these pollutants by the local population.     

Effects of long-term soil amendment with sewage sludges on soil humic acid thermal and molecular properties

Sewage sludges are frequently used as soil amendments due to their high contents of organic matter and nutrients, particularly N and P. However, their effects upon the chemistry of soil humic acids, one of the main components of the soil organic matter, need to be more deeply studied in order to understand the relation between organic matter structure and beneficial soil properties. Two sewage sludges subjected to different types of pre-treatment (composted and thermally dried) with very different chemical compositions were applied for three consecutive years to an agricultural soil under long-term field study. Thermal analysis (TG–DTG–DTA) and solid-state ¹³C NMR spectroscopy were used to compare molecular and structural properties of humic acids isolated from sewage sludges, and to determine changes in amended soils. Thermally dried sewage sludge humic acids showed an important presence of alkyl and O/N-alkyl compounds (70%) while composted sludge humic acids comprised 50% aromatic and carbonyl carbon. In spite of important differences in the initial chemical and thermal properties of the two types of sewage sludges, the chemical and thermal properties of the soil humic acids were quite similar to one another after 3 years of amendment. Long-term application of both sewage sludges resulted in 80–90% enrichment in alkyl carbon and organic nitrogen contents of the soil humic acid fraction.     

Arsenate tolerance in Silene paradoxa does not rely on phytochelatin-dependent sequestration

Arsenate tolerance, As accumulation and As-induced phytochelatin accumulation were compared in populations of Silene paradoxa, one from a mine site enriched in As, Cu and Zn, the other from an uncontaminated site. The mine population was significantly more arsenate-tolerant. Arsenate uptake and root-to-shoot transport were slightly but significantly higher in the non-mine plants. The difference in uptake was quantitatively insufficient to explain the difference in tolerance between the populations. As accumulation in the roots was similar in both populations, but the mine plants accumulated much less phytochelatins than the non-mine plants. The mean phytochelatin chain length, however, was higher in the mine population, possibly due to a constitutively lower cellular glutathione level. It is argued that the mine plants must possess an arsenic detoxification mechanism other than arsenate reduction and subsequent phytochelatin-based sequestration. This alternative mechanism might explain at least some part of the superior tolerance in the mine plants.     

Evaluation of stream ecological integrity using litter decomposition and benthic invertebrates

Biomonitoring programs to access the ecological integrity of freshwaters tend to rely exclusively on structural parameters. Here we evaluated stream ecological integrity using (a) benthic macroinvertebrate derived metrics and a biotic index as measures of structural integrity and (b) oak litter decomposition and associated fungal sporulation rates as measures of functional integrity. The study was done at four sites (S1, S2, S3 and S4) along a downstream increasing phosphorus and habitat degradation gradient in a small stream. The biotic index, invertebrate metrics, invertebrate and fungal communities' structure and sporulation rates discriminated upstream and downstream sites. Decomposition rates classified sites S4 and S2 as having a compromised ecosystem functioning. Although both functional and structural approaches gave the same results for the most impacted site (S4), they were complementary for moderately impacted sites (S2 and S3), and we therefore support the need for incorporating functional measures in evaluations of stream ecological integrity.     

Determining metal origins and availability in fluvial deposits by analysis of geochemical baselines and solid-solution partitioning measurements and modelling

Metals in floodplain soils and sediments (deposits) can originate from lithogenic and anthropogenic sources, and their availability for uptake in biota is hypothesized to depend on both origin and local sediment conditions. In criteria-based environmental risk assessments, these issues are often neglected, implying local risks to be often over-estimated. Current problem definitions in river basin management tend to require a refined, site-specific focus, resulting in a need to address both aspects. This paper focuses on the determination of local environmental availabilities of metals in fluvial deposits by addressing both the origins of the metals and their partitioning over the solid and solution phases. The environmental availability of metals is assumed to be a key force influencing exposure levels in field soils and sediments. Anthropogenic enrichments of Cu, Zn and Pb in top layers could be distinguished from lithogenic background concentrations and described using an aluminium-proxy. Cd in top layers was attributed to anthropogenic enrichment almost fully. Anthropogenic enrichments for Cu and Zn appeared further to be also represented by cold 2 M HNO₃ extraction of site samples. For Pb the extractions over-estimated the enrichments. Metal partitioning was measured, and measurements were compared to predictions generated by an empirical regression model and by a mechanistic-kinetic model. The partitioning models predicted metal partitioning in floodplain deposits within about one order of magnitude, though a large inter-sample variability was found for Pb.