The pH-dependent adsorption of tributyltin to charcoals and soot

Widespread use of tributyltin (TBT) poses a serious environmental problem. Adsorption by black carbon (BC) may strongly affect its behavior. The adsorption of TBT to well characterized soot and two charcoals with specific surface area in the range of 62-111 m² g⁻¹ have been investigated with main focus on pH effects. The charcoals but not soot possess acidic functional groups. TBT adsorption reaches maximum at pH 6-7 for charcoals, and at pH > 6 for soot. Soot has between 1.5 and 15 times higher adsorption density (0.09-1.77 μmol m⁻²) than charcoals, but charcoals show up to 17 times higher sorption affinities than soot. TBT adsorption is successfully described by a new pH-dependent dual Langmuir model considering electrostatic and hydrophobic adsorption, and pH effects on TBT speciation and BC surface charge. It is inferred that strong sorption of the TBTOH species to BC may affect TBT toxicity.     

Community assembly in experimental grasslands: suitable environment or timely arrival?

It is hard to defend the view that biotic communities represent a simple and predictable response to the abiotic environment. Biota and the abiotic environment interact, and the environment of an individual certainly includes its neighbors and visitors in the community. The complexity of community assembly calls forth a quest for general principles, yet current results and theories on assembly rules differ widely. Using a grassland microcosm as a model system, we manipulated fertility, disturbance by defoliation, soil/microclimate, and arrival order of species belonging to two groups differing in functional attributes. We analyzed the outcome of community assembly dynamics in terms of species richness, invasibility, and species composition. The analyses revealed strong environmental control over species richness and invasibility. Species composition was mainly determined by the arrival order of species, indicating that historical contingency may change the outcome of community assembly. The probability for multiple equilibria appeared to increase with productivity and environmental stability. The importance of arrival order offers an explanation of the difficulties in predicting local occurrences of species in the field. In our experiment, variation in fertility and disturbance was controlling colonization with predictable effects on emergent community properties such as species richness. The key mechanism is suggested to be asymmetric competition, and our results show that this mechanism is relatively insensitive to the species through which it works. While our analyses indicate a positive and significant correlation between richness and invasibility, the significance disappears after accounting for the effect of the environment. The importance of arrival order (historical contingency) and environmental control supports the assumption of the unified neutral theory that different species within a trophic level can be considered functionally equivalent when it comes to community assembly. However, our results indicate that variation in asymmetric competition is the key factor determining the richness of the resulting communities, and this is far from neutral.     

The impact of swidden decline on livelihoods and ecosystem services in Southeast Asia: A review of the evidence from 1990 to 2015

Global economic change and policy interventions are driving transitions from long-fallow swidden (LFS) systems to alternative land uses in Southeast Asia’s uplands. This study presents a systematic review of how these transitions impact upon livelihoods and ecosystem services in the region. Over 17 000 studies published between 1950 and 2015 were narrowed, based on relevance and quality, to 93 studies for further analysis. Our analysis of land-use transitions from swidden to intensified cropping systems showed several outcomes: more households had increased overall income, but these benefits came at significant cost such as reductions of customary practice, socio-economic wellbeing, livelihood options, and staple yields. Examining the effects of transitions on soil properties revealed negative impacts on soil organic carbon, cation-exchange capacity, and aboveground carbon. Taken together, the proximate and underlying drivers of the transitions from LFS to alternative land uses, especially intensified perennial and annual cash cropping, led to significant declines in pre-existing livelihood security and the ecosystem services supporting this security. Our results suggest that policies imposing land-use transitions on upland farmers so as to improve livelihoods and environments have been misguided; in the context of varied land uses, swidden agriculture can support livelihoods and ecosystem services that will help buffer the impacts of climate change in Southeast Asia.     

Cross-achievements between policies for drinking water protection

Environmental dynamics have important spatial dimensions, which calls for a spatial approach in policy analyses. Further to this, assessing agri-environmental policies involves analyses of individual measures as well as their combined effects on farmer behaviour and the environment. The integration of an economic behavioural model in a spatial framework has enabled analyses of a geographically targeted subsidy scheme for drinking water protection in combination with a uniform tax on commercial nitrogen fertilizer. Results show that policy measures for reducing nitrogen use can have combined effects (cross-achievements), thereby affecting each other's cost-effectiveness. Cross-achievements between a nitrogen fertilizer tax and a subsidy scheme based on elicitation are shown not to be additive, making partial analyses of policy measures more uncertain.     

Degradation and mobility of linear alkylbenzene sulfonate and nonylphenol in sludge-amended soil

Degradation and mobility of the surfactants linear alkylbenzene sulfonate (LAS) and nonylphenol (NP) were investigated in a lysimeter study using a sandy loam soil and 45-cm soil columns. Anaerobically digested sewage sludge was incorporated in the top-15-cm soil layer to an initial content of 38 mg LAS and 0.56 mg NP kg(-1) dry wt., respectively. Spring barley (Hordeum vulgare L.) was sown onto the columns. The lysimeters were placed outdoors and therefore received natural precipitation, but were also irrigated to a total amount of water equivalent to 700 mm of precipitation. Leachate and soil samples from three soil layers were collected continuously during a growth period of 110 d. Leachate samples and soil extracts were concentrated by solid-phase extraction (SPE) and analyzed using high performance liquid chromatography (HPLC) with fluorescence detection. The concentrations in the top-15-cm soil layer declined to 25 and 45% of the initial contents for LAS and NP, respectively, within the first 10 d of the study. At the end of the study, less than 1% LAS was left, while the NP content was below the detection limit. Assuming first-order degradation kinetics, half-lives of 20 and 37 d were estimated for LAS and NP, respectively. The surfactants were not measured in leachate samples in concentrations above the analytical detection limits of 4.0 and 0.5 microg L(-1) for LAS and NP, respectively. In addition, neither LAS nor NP were measured in concentrations above the detection limits of 150 and 50 microg kg(-1) dry wt., respectively, in soil layers below the 15 cm of sludge incorporation, indicating negligible downward transport of the surfactants in the lysimeters.     

The past impact of livestock husbandry on dispersal of plant seeds in the landscape of Denmark

The recent decline in species richness in (semi)-natural habitats in northern Europe has largely been attributable to habitat destruction, and to subsequent limitation in seed dispersal among fragments. However, some habitat types were probably split up already in the historical landscape, but the segregated parts were probably not isolated to the present degree. This paper seeks evidence for livestock as vectors for propagules at 3 spatial scales in the past cultural landscape. Three main scales at which livestock acted as seed dispersers are important: free movement in the landscape (1-10 km), driving animals to mast feeding or to manors (10-50 km), and the export of living animals (hundreds of km). The emerging picture is for most plant species a dramatically decreased chance of dispersal in the modern landscape. The consequence is probably decreasing species richness in (semi)-natural plant communities, such as pasture, meadow, and heathland.     

Sorption of lambda-cyhalothrin,cypermethrin, deltamethrin and fenvalerate to quartz,corundum, kaolinite and montmorillonite

Sorption to mineral surfaces may be important for retention and degradation of hydrophobic pesticides in subsoils and aquifers poor in organic matter. In this work the title pyrethroids have been used to investigate selective interactions with the surfaces of four minerals. Sorption of the four pyrethroids was quantified in batch experiments with initial pyrethroid concentrations of 1–100 μg/l. Sorption to centrifuge tubes used in the batch experiments accounted for 25–60% of total sorption. Net sorption was obtained from total sorption after subtracting the amounts of pyrethroids sorbed to centrifuge tubes used. All isotherms could be fitted by the Freundlich equation with n ranging between 0.9 and 1.1. Bonding affinities per unit surface area decreased in the order: corundum>quartz>montmorillonitekaolinite. A similar sequence as found for the total surface tension of the minerals. All minerals showed the same selectivity order with respect to sorption affinity of the four pyrethroids: lambda-cyhalothrin>deltamethrin>cypermethrin>fenvalerate, which shows that the most hydrophobic compound is sorbed most strongly. Stereochemical properties of the four pyrethroid formulations may also contribute to the selectivity pattern.     

Halogenated organic contaminants in marine fish and mussels from southern Greenland--pilot study on relations to trophic levels and local sources

Mussels and marine fish (shorthorn sculpin and Greenland cod) were sampled at three locations with varying human activity. Fish livers and mussels were analysed for polychlorinated biphenyls (PCBs), polybrominated diphenylethers (PBDEs) and chlorinated pesticides including chlordane and toxaphene. Levels of chlorinated contaminants in shorthorn sculpins from the background location, [capital Sigma]PCB (217-224 ng g(-1) lw), [capital Sigma]DDT (180 ng g(-1) lw) and hexachlorobenzene (32-44 ng g(-1) lw), were in the same range as previously observed in eastern Greenland but exceeded the levels previously observed in southern and western Greenland. Multivariate analysis showed that pollutant concentrations were mainly explained by trophic levels of the species (cod > sculpins > mussels). A pooled sample of shorthorn sculpins from the harbour of Qaqortoq had significantly higher PCB and PBDE concentrations with a different congener pattern compared to the background site, while other contaminants were comparable. This points towards local pollution sources, possibly accumulated emissions from burning of waste.     

Nitrogen Inputs from Agriculture: Towards Better Assessments of Eutrophication Status in Marine Waters

Nutrient enrichment of coastal marine waters caused by losses of nitrate (NO₃⁻) from agriculture is an increasing global problem. In the European Union, the Nitrates Directive (ND) of 1991 was meant to be a cornerstone in reducing eutrophication effects in coastal waters downstream from intensively farmed catchments. Although reductions in losses of nitrate have been attained, very few Member States have yet been able to reduce eutrophication effects caused by inputs of NO₃⁻ from agriculture. We report trends in concentrations of NO₃⁻ and chlorophyll-a (Chl-a) in Danish coastal and open marine waters during the period from 1996 to 2011 together with an assessment of eutrophication status based on multiple indicators (e.g. nutrient concentrations, Chl-a, submerged aquatic vegetation and benthic macroinvertebrates). Despite decreasing concentrations of both NO₃⁻and Chl-a, Danish coastal waters are not yet to be classified as ‘unaffected by eutrophication’. In order to improve future pan-European evaluations of the effectiveness of the ND, we argue for the added value of including indicators and assessment principles from other European Directives, i.e. the Water Framework Directive and the Marine Strategy Framework Directive.

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