Bioavailability of persistent organic pollutants in soils and sediments--a perspective on mechanisms, consequences and assessment

It has been observed that as soil-pollutant contact time increases, pollutant bioavailability and extractability decreases. This phenomenon has been termed 'ageing'. Decreased chemical extractability with increased soil-chemical contact time is evident where both 'harsh' techniques, e.g. dichloromethane Soxhlet extraction, and 'non-exhaustive' techniques, e.g. butanol shake extraction, have been used. It has also been observed that the amount of chemical extracted by these techniques varies considerably over time. Similarly, decreases in bioavailability with increased soil-pollutant contact time have been described in bacterial, earthworm and other organism studies. From these investigations, it has been shown that the fraction of pollutant determined to be bioavailable can vary between organisms. Thus, there is an immediate definition problem, what is bioavailability? Additionally, if bioavailability is to be assessed by a chemical means, which organisms should (or can) be mimicked by the extraction procedure? This review provides a background to the processes inherent to ageing, a discussion of its consequences on bioavailability and ends with some reflections on the appropriateness of chemical extraction techniques to mimic bioavailability     

Determination of 4-tert-octylphenol, 4-nonylphenol and bisphenol A in surface waters from the Haihe River in Tianjin by gas chromatography-mass spectrometry with selected ion monitoring

The estrogenic pollutants 4-tert-octylphenol (OP), 4-nonylphenol (NP) and bisphenol A (BPA) were determined in surface water samples from the Haihe River, Tianjin, China. The analytes were extracted and concentrated from 300 ml acidified water samples by liquid–liquid extractions using dichloromethane, derivatized with trifluoroacetic anhydride, and quantified by gas chromatography–mass spectrometry (GC–MS) with selected ion monitoring (SIM). Among the samples collected from 14 sampling sites, only one sample was found to have a relatively high concentration of BPA (8.30 μg l⁻¹) and NP (0.55 μg l⁻¹). The concentrations of OP, NP and BPA in the other samples were in the range of 18.0–20.2, 106–296 and 19.1–106 ng l⁻¹, respectively. Recoveries for OP, NP and BPA in the spiked water samples were all over 80%.     

Size–frequency dynamics of NE Pacific abyssal ophiuroids (Echinodermata: Ophiuroidea)

The 17-year time-series study at Station M in the NE Pacific has provided one of the longest datasets on deep-sea ophiuroids to date. Station M is an abyssal site characterized by low topographical relief and seasonal and interannual variation in surface-derived food inputs. From 1989 to 2005, over 31,000 ophiuroid specimens were collected. Size–frequency distributions of the four dominant species, Ophiura bathybia, Amphilepis patens, Amphiura carchara and Ophiacantha cosmica, were examined for recruitment and the role of surface-derived food supplies on body size distributions. Juveniles were collected in sediment traps and used to investigate settlement patterns and seasonality. Trawl samples showed no indication of seasonal changes in recruitment to larger size classes; however, there was evidence of seasonal settling of juveniles. Interannual differences in median disk diameters and size distributions of trawl-collected adults are greater than those at the seasonal scale. Three of the four species, O. bathybia, A. patens and O. cosmica, had co-varying monthly median disk diameters, suggesting they may have a similar factor(s) controlling their growth and abundance. Interannual differences in monthly size distributions were generally greater than those between seasons. Cross-correlations between the particulate organic carbon (POC) flux (food supply) and size distribution indices for O. bathybia, A. patens and O. cosmica all were significant indicating that increases in food supply were followed by increases in the proportion of smaller size classes after approximately 17–22 months. These findings suggest that food inputs are indeed an important factor influencing deep-sea ophiuroid populations on interannual time scales, more generally supporting the long-hypothesized connection between food availability and population size structure in the deep sea. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Modeling and data assessment of longitudinal salinity in a low-gradient estuarine river

Continuous data of vertical-profile salinity were analyzed for four stations located successively upriver in a macrotidal estuary, the lower St. Johns River (Northeast Florida, USA). The data analysis confirmed well-mixed salinity conditions in the river with at most 1.3 ppt of vertical variability at Dames Point (river km 20), where the main variations of salinity are along the longitudinal axis of the river. Given the well-mixed salinity conditions and dominant horizontal structure of salinity variations in the river, we present and apply a barotropic, two-dimensional modeling approach for hydrodynamic-salinity transport simulation in the lower St. Johns River. When properly forced by offshore surge, high-resolution wind fields and freshwater river inflows, the model replicated the salinity measurements remarkably well, including the separation into tidal and sub-tidal components. The data and model results show that, at times, offshore winds and surge can be more influential on longitudinal salinity variations than local winds over the river. We demonstrate the importance of using proper boundary conditions to force the model relative to the minimal sensitivity of the model to parameter adjustment of horizontal mixing and uncertainty-based perturbation of wind and inflow forcings.     

Applying the zoo model to conservation of threatened exceptional plant species

Maintaining a living plant collection is the most common method of ex situ conservation for plant species that cannot be seed banked (i.e., exceptional species). Viability of living collections, and their value for future conservation efforts, can be limited without coordinated efforts to track and manage individuals across institutions. Using a pedigree-focused approach, the zoological community has established an inter-institutional infrastructure to support long-term viability of captive animal populations. We assessed the ability of this coordinated metacollection infrastructure to support the conservation of 4 plant species curated in living collections at multiple botanic gardens around the world. Limitations in current practices include the inability to compile, share, and analyze plant collections data at the individual level, as well as difficulty in tracking original provenance of ex situ material. The coordinated metacollection framework used by zoos can be adopted by the botanical community to improve conservation outcomes by minimizing the loss of genetic diversity in collections. We suggest actions to improve ex situ conservation of exceptional plant species, including developing a central database to aggregate data and track unique individuals of priority threatened species among institutions and adapting a pedigree-based population management tool that incorporates life-history aspects unique to plants. If approached collaboratively across regional, national, and global scales, these actions could transform ex situ conservation of threatened plant species.     

Mycotoxins of Aspergillus fumigatus in pure culture and in native bioaerosols from compost facilities

Exposure to secondary metabolites of airborne fungi in waste handling facilities is discussed in regard to potential toxic impacts on human health. The relevance of mycotoxins has been intensely studied in connection with contamination of food and feed. Toxic secondary metabolites are expected to be present in airborne spores, but exposure to mycotoxins in bioaerosols has not been studied sufficiently. Aspergillus fumigatus is one of the most frequent species in the air of compost plants. A wide range of secondary metabolites was found in pure cultures of freshly isolated strains of A. fumigatus. Tryptoquivaline, a compound with tremorgenic properties, and trypacidin, for which no toxic properties are described, were found in native bioaerosols in a compost facility. The highly toxic metabolites gliotoxin and verruculogen were not found in the bioaerosols.     

Atrazine sorption and fate in a Ultisol from humid tropical Brazil

This study combined laboratory based microcosm systems as well as field experiments to evaluate the mobility of atrazine on a Ultisol under humid tropical conditions in Brazil. Results from sorption experiments fit to the Freundlich isotherm model [K(f) 0.99 mg kg(-1)/(mg l(-1))(1/n)], and indicate a low sorption capacity for atrazine in this soil and consequently large potential for movement by leaching and runoff. Microcosm systems using (14)C-atrazine to trace the fate of the applied herbicide, showed that 0.33% of the atrazine was volatilized, 0.25% mineralized and 6.89% was recorded in the leachate. After 60 d in the microcosms, 75% of the (14)C remained in the upper 5 cm soil layer indicating atrazine or its metabolites remained close to the soil surface. In field experiments, after 60 d, only 5% of the atrazine applied was recovered in the upper soil layers. In the field experiments atrazine was detected at a depth of 50 cm indicating leaching. Simulating tropical rain in field experiments resulted in 2.1% loss of atrazine in runoff of which 0.5% was adsorbed onto transported soil particles and 1.6% was in solution. Atrazine runoff was greatest two days after herbicide application and decreased 10 fold after 15 d. The use of atrazine on Ultisols, in the humid tropics, constitutes a threat to water quality, causing surface water and ground water pollution.     

Redox-active ligands in artificial photosynthesis: a review

Environmental Chemistry Letters - Given the rising socioeconomic issues of fossil fuels, efficient artificial photosynthesis would be an important milestone toward a sustainable world. A key step...