Aufnahmepfade von POPs in Biota

POPs (persistent organic pollutants) associated with aquatic sediments can pose a risk to aquatic food chains, since they can be re-introduced to the food web. One major pathway is the bioaccumulation of POPs by endobenthic, sedimentingesting invertebrates (especially tubificid oligochaetes). These worms serve as food for benthivorous fish, which thereby ingest the sediment-borne chemicals and may accumulate contaminant concentrations far higher than from water exposure alone, and consequently transfer them to organisms of higher trophic levels. In order to evaluate such a potential biomagnification, a laboratory test was developed. It consisted of a two-step food chain including the sediment dwelling freshwater oligochaete Tubifex tubifex (Müller) and the three-spined stickleback (Gasterosteus aculeatus, Linné), a small teleost fish which often feeds primarily on benthic invertebrates. Artificial sediment and reconstituted water were used. To examine the influence of benthic prey on the bioaccumulation of a POP in the predator, fish were exposed to ¹⁴C-labelled hexachlorobenzene via spiked water, spiked sediment, pre-contaminated prey organisms, and to combinations of these exposure routes. Summarising the results of these experiments, it could be shown that the exposure to HCB via different routes resulted in a significantly higher accumulation in fish than an exposure to single pathways. It was concluded that the major uptake routes for fish were the overlying water and the food, whereas the contribution of spiked sediment itself was relatively small. HCB was biomagnified in the rested laboratory food chain. Therefore, concerning secondary poisoning, the environmental risk assessment of POPs like HCB should not be based on existing bioaccumulation tests alone, since they focus only on exposure via the water pathway. Instead, the influence of food and sediment as exposure routes should be considered as well, using comprehensive food chain modelling and/or laboratory studies.     

An economic analysis of China’s domestic crude oil supply policies

ABSTRACT

China’s domestic oil production has lagged the growth in domestic oil consumption since the beginning of the 21st century, leading to a growing reliance on imports. In response, the Chinese government has introduced a number of policies, including import license constraints, to support domestic suppliers. In an effort to measure the economic impact of these policies we develop a short-run equilibrium model of China’s wholesale oil and gas market at the provincial scale. We construct counterfactual scenarios that suggest that relaxing policies that prioritize domestic production in 2016, when the average price of Chinese oil imports was US$42 per barrel (bbl), could have increased China’s import demand by 0.29 million barrels per day (MMbbl/d). This results in a substitution of 9% of China’s domestic production in 2016, and a reduction of US $2.8 billion in crude supply costs including transportation as the imported oil has more direct access to the country’s pipeline network, compared to the displaced domestic production. In addition, rising import prices since mid-2017 may provide a window of opportunity for Chinese policymakers to proceed with further deregulation of the domestic oil sector, as the short-term impact on domestic producers is reduced.     

A flow-through passive dosing system for continuously supplying aqueous solutions of hydrophobic chemicals to bioconcentration and aquatic toxicity tests

A continuous supply of water with defined stable concentrations of hydrophobic chemicals is a requirement in a range of laboratory tests such as the OECD 305 protocol for determining the bioconcentration factor in fish. Satisfying this requirement continues to be a challenge, particularly for hydrophobic chemicals. Here we present a novel solution based on equilibrium passive dosing. It employs a commercially available unit consisting of ∼16 000 polydimethylsiloxane (PDMS) tubes connected to two manifolds. The chemicals are loaded into the unit by repeatedly perfusing it with a methanol solution of the substances that is progressively diluted with water. Thereafter the unit is perfused with water and the chemicals partition from the unit into the water. The system was tested with nine chemicals with log K_OW ranging from 4.1 to 6.3. The aqueous concentrations generated were shown to be largely independent of the water flow rate, and the unit to unit reproducibility was within a factor of ∼2. In continuous flow experiments the aqueous concentrations of most of the study chemicals remained constant over 8 d. A model was assembled that allows prediction of the operating characteristics of the system from the log K_OW or PDMS/water partition coefficient of the chemical. The system is a simple, safe, predictable and flexible tool that generates stable aqueous concentrations of hydrophobic chemicals.     

Effects of access to preen gland secretions on mallard plumage

Preen glands exist in almost every bird species and several non-exclusive functions have been proposed for this gland and the oils that it produces. One function generally admitted is that the oily secretions of the preen gland would provide a waterproofing layer when spread over feathers. Alternatively, several authors have proposed that plumage waterproofness is mostly due to the spatial micro-structure of feathers. The purpose of this study was to examine, by manipulating the access to the preen gland, the effect of the preen oil on the plumage waterproofness and condition. To explore this question, we carried out two independent experiments where we temporarily blocked access to the preen gland secretions with a removable mechanism in one group of captive mallards (Anas platyrhynchos), whilst a second group of birds had access to gland secretions. In a long-term experiment (3 months of treatment) and a short-term experiment (10 days), we measured plumage water retention and condition. After 3 months without access to preen glands, we found a significant decrease of plumage condition and an associated increase in plumage water retention. Moreover, we found a significant correlation between plumage condition and water retention ability. In contrast, after 10 days of treatment, no significant effect was found on plumage condition and water retention. Our study shows that preen oil acts to maintain plumage condition and suggests that feather microstructure is essential to maintain plumage waterproofness.     

Implementing comprehensive plans: indicators for a task-sheet based performance evaluation process

Evaluation in spatial planning aims to raise effectiveness of plans as well as efficiency in planning processes. Given that research regarding evaluation of performance and especially plan implementation is sparse, this study presents a minimal set of indicators for a task-sheet based performance evaluation approach for Swiss cantonal comprehensive plans. Thematic task-sheets are a promising characteristic of cantonal comprehensive plans. They translate the comprehensive planning strategy into concrete evaluable tasks. The presented indicators allow assessing procedural efficiency of coordination and implementation of planning tasks (performance). We argue that if task-sheets comply with certain plan quality characteristics, a task-sheet based performance evaluation approach can support the effectiveness of plans and promote the objectives of the planning strategy. We point out plan content and characteristics necessary for effective execution of our approach. As a result, our findings can serve as a framework for designing evaluation processes for comprehensive planning documents beyond Switzerland.     

Biodegradation of phenol and phenol-related compounds by psychrophilic and cold-tolerant alpine yeasts

We characterized 32 cold-adapted, psychrophilic and cold-tolerant, yeast strains isolated from alpine habitats with regard to their taxonomy, growth temperature profile, and ability to degrade phenol and 18 phenol-related mono-aromatic compounds at 10 degrees C. Twenty of the strains were identified by sequencing of the ribosomal ITS region as seven species of the basidiomycota: Cryptococcus terreus (three strains), Cryptococcus terricola (one strain), Rhodosporidium lusitaniae (two strains), Rhodotorula creatinivora (10 strains), Rhodotorula ingeniosa (one strain), Mastigobasidium intermedium (one strain), and Sporobolomyces roseus (two strains). Twelve strains sharing closely related ITS sequences could not be identified to the species level; according to their ITS sequence they are included in the Microbotryomycetidae. These 12 strains were psychrophilic (no growth at temperatures above 20 degrees C); one-third of these strains did not grow above 15 degrees C. None of the 32 strains utilized any of the highly volatile mono-aromatic compounds (benzene, toluene, ethylbenzene, nitrobenzene, o-xylene, m-xylene, and p-xylene) as the sole carbon source. Non/low volatile aromatic compounds were degraded in the following order: phenol>hydroquinone>resorcinol>benzoate>catechol>salicylate>p-cresol>m-cresol. o-Cresol, guaiacol, p-nitrophenol, or p-nitrotoluene were not utilized for growth. R. creatinivora strains degraded up to seven compounds, whereas C. terricola and S. roseus strains degraded only two compounds. The toxicity of the compounds was determined via growth inhibition in the presence of toxicants and nutrients at 10 degrees C. R. creatinivora strains were characterized by higher IC50 values than other species, S. roseus was the most sensitive species. The most toxic compounds were the xylene isomers, ethylbenzene, p-nitrophenol, and m-cresol. There was a relation between the chemical structure of the compounds and their toxicity, whereas a relation between the toxicity of the compounds and the ability of the yeasts strains to utilize these compounds for growth was only detected in some cases.