Photoinduced reduction of divalent mercury in ice by organic matter

Reduction of divalent mercury and subsequent emission to the atmosphere has been identified as loss process from surface snow, but its mechanism and importance are still unclear. The amount of mercury that stays in the snow pack until spring is of significance, because during snow melt it may be released to the aquatic environment and enter the food web. Better knowledge of its fate in snow might further assist the interpretation of ice core data as paleo-archive. Experiments were performed under well-controlled laboratory conditions in a coated wall flow tube at atmospheric pressure and irradiated with light between 300 nm and 420 nm. Our results show that the presence of benzophenone and of oxalic acid significantly enhances the release of mercury from the ice film during irradiation, whereas humic acid is less potent to promote the reduction. Further it was found that oxygen or chloride, and acidic conditions lowered the photolytically induced mercury release in the presence of benzophenone, while the release got larger with increasing temperatures.     

Volatile nanoparticle formation and growth within a diluting diesel car exhaust

A major source of particle number emissions is road traffic. However, scientific knowledge concerning secondary particle formation and growth of ultrafine particles within vehicle exhaust plumes is still very limited. Volatile nanoparticle formation and subsequent growth conditions were analyzed here to gain a better understanding of "real-world" dilution conditions. Coupled computational fluid dynamics and aerosol microphysics models together with measured size distributions within the exhaust plume of a diesel car were used. The impact of soot particles on nucleation, acting as a condensational sink, and the possible role of low-volatile organic components in growth were assessed. A prescribed reduction of soot particle emissions by 2 orders of magnitude (to capture the effect of a diesel particle filter) resulted in concentrations of nucleation-mode particles within the exhaust plume that were approximately 1 order of magnitude larger. Simulations for simplified sulfuric acid-water vapor gas-oil containing nucleation-mode particles show that the largest particle growth is located in a recirculation zone in the wake of the car. Growth of particles within the vehicle exhaust plume up to detectable size depends crucially on the relationship between the mass rate of gaseous precursor emissions and rapid dilution. Chassis dynamometer measurements indicate that emissions of possible hydrocarbon precursors are significantly enhanced under high engine load conditions and high engine speed. On the basis of results obtained for a diesel passenger car, the contributions from light diesel vehicles to the observed abundance of measured nucleation-mode particles near busy roads might be attributable to the impact of two different time scales: (1) a short one within the plume, marked by sufficient precursor emissions and rapid dilution; and (2) a second and comparatively long time scale resulting from the mix of different precursor sources and the impact of atmospheric chemistry.     

Mechanisms of purple moor-grass (Molinia caerulea) encroachment in dry heathland ecosystems with chronic nitrogen inputs

We analysed growth strategies (biomass allocation, nutrient sequestration and allocation) of heather (Calluna vulgaris) and purple moor-grass (Molinia caerulea) seedlings in monocultures and mixtures in relation to N, P, and N + P fertilisation in a greenhouse experiment in order to simulate a heath’s pioneer phase under high airborne nitrogen (N) loads. N fertilisation increased the total biomass of both species in monocultures. In mixtures, M. caerulea sequestered about 65% of the N applied, while C. vulgaris suffered from N shortage (halving of the total biomass). Thus, in mixtures only M. caerulea will benefit from airborne N loads, and competition will become increasingly asymmetric with increasing N availability. Our results demonstrate that the heath’s pioneer phase is the crucial tipping point at which the competitive vigour of M. caerulea (high belowground allocation, efficient use of belowground resources, shortened reproductive cycles) induces a shift to dominance of grasses under increased N availability.     

Fate of bisphenol A during treatment with the litter-decomposing fungi Stropharia rugosoannulata and Stropharia coronilla

Bisphenol A is an endocrine disrupting compound, which is ubiquitous in the environment due to its wide use in plastic and resin production. Seven day old cultures of the litter-decomposing fungus Stropharia coronilla removed the estrogenic activity of bisphenol A (BPA) rapidly and enduringly. Treatment of BPA with purified neutral manganese peroxidase (MnP) from this fungus also resulted in 100% reduction of estrogenic activity, as analyzed using a bioluminescent yeast assay, and in the formation of polymeric compounds. In cultures of Stropharia rugosoannulata, estrogenic activity also quickly disappeared but temporarily re-emerged in the further course of cultivation. LC-MS analysis of the extracted estrogenic culture liquid revealed [M−H]⁻ ions with m/z values of 219 and 235. We hypothesize that these compounds are ring fission products of BPA, which still exhibit one intact hydroxyphenyl group to interact with estrogen receptors displayed by the yeast.     

Toxicity assessment of a common laundry detergent using the freshwater flagellate Euglena gracilis

Synthetic detergents are among the commonly used chemicals in everyday life. Detergents, reaching aquatic environments through domestic and municipal wastewater, can cause many different effects in aquatic organisms. The present study was aimed at the toxicity evaluation of a commonly used laundry detergent, Ariel, using the freshwater flagellate Euglena gracilis as a biotest organism. Different parameters of the flagellate like motility, swimming velocity, cell shape, gravitactic orientation, photosynthesis and concentration of light harvesting pigments were used as end points for the toxicity assessment. No Observed Effect Concentration (NOEC) and EC₅₀ values were calculated for the end point parameters at four different incubation times, i.e. 0, 6, 24 and 72 h. After 72 h incubation, swimming velocity of the cells was found to be the most sensitive parameter giving NOEC and EC₅₀ values of 10.8 and 34 mg L⁻¹, respectively. After 72 h exposure to the detergent, chlorophyll a and total carotenoids were significantly decreased in cultures treated with Ariel at concentrations of 50 mg L⁻¹ and above while chlorophyll b significantly decreased at concentrations above 750 mg L⁻¹. The maximum inhibitory effect on the quantum yield of photosystem II was observed after 24 h exposure and thereafter a recovery trend was observed. Motility, gravitaxis and cell shape were strongly impaired immediately upon exposure to the detergent, but with increasing exposure time these parameters showed acclimatization to the stress and thus the NOEC values obtained after 72 h were higher than those immediately after exposure.     

Water pollution in Pakistan and its impact on public health--a review

Water pollution is one of the major threats to public health in Pakistan. Drinking water quality is poorly managed and monitored. Pakistan ranks at number 80 among 122 nations regarding drinking water quality. Drinking water sources, both surface and groundwater are contaminated with coliforms, toxic metals and pesticides throughout the country. Various drinking water quality parameters set by WHO are frequently violated. Human activities like improper disposal of municipal and industrial effluents and indiscriminate applications of agrochemicals in agriculture are the main factors contributing to the deterioration of water quality. Microbial and chemical pollutants are the main factors responsible exclusively or in combination for various public health problems. This review discusses a detailed layout of drinking water quality in Pakistan with special emphasis on major pollutants, sources of pollution and the consequent health problems. The data presented in this review are extracted from various studies published in national and international journals. Also reports released by the government and non-governmental organizations are included.     

Urban mining: hibernating copper stocks in local power grids

Large technical systems serving the everyday needs of people, such as water supply systems, power grids or communication networks, are rich in accumulated metals. Over time, parts of these systems have been taken out of use without the system infrastructure being removed from its original location. Such metal stocks in hibernation thus constitute potential resource reservoirs accessible for recovery. In this paper, obsolete stocks of copper situated in the local power grids of two Swedish cities are quantified. Emphasis is also on economic conditions for extracting such “hibernating” cables. The results show that on a per customer basis, the two power grids contain similar amounts of copper, i.e. 0.04–0.05 tonnes per subscriber. However, the share of the copper stock that is in hibernation differs between the grids. In the larger grid of Gothenburg, almost 20% of the copper accumulated in the grid is no longer in use, while the obsolete share does not exceed 5% in the city of Linköping. For managers of local power grids, recovery of hibernating cables could be beneficial if integrated with other maintenance work on the grid. At the present price of copper, however, separate recovery of obsolete cables is not economically justified.     

Occupational chemical exposure and risk estimation in process development and design

Each year more people die from diseases caused by work than are killed in industrial accidents. Therefore, methods are needed to evaluate occupational health hazards as early as possible when the process is still under development. A method for estimating inhalative exposures and risks in petrochemical and related plants is presented. The method is simple and suffices with the limited data availability during the early design stages.The steps of the method, which utilizes preliminary process flow diagrams are as follows: first the fugitive emissions and process plot areas are estimated based on precalculated process modules representing the typical process sections (such as a distillation unit). Chemical concentration in the air is then calculated based on the wind velocity probability and the estimated process cross-sectional area. For this purpose a typical wind velocity distribution in the area is used. The worker risk of exposure to chemicals is evaluated either based on the concentration in air by using the hazard quotient method or calculating the carcinogenic chemicals intake and the resulting risk of cancer. The values are compared to the benchmarks.As a result the process route health characteristics such as fugitive emissions rate, critical wind speed, chemical concentration in air and intake amount as well as the corresponding risk of exposure are produced. By using statistical meteorological data, health risks of occupational exposure can be estimated more realistically as probabilities. The approach is capable of comparing alternative processes to select the concept which is inherently occupationally healthier. Using this method, the exposure problems of a process can be identified earlier and proper decisions can be made early in process development or predesign stage.The concentration-based method is demonstrated by a case study of six competing manufacturing routes for methyl methacrylate (MMA). The C3 is found to be the most harmful alternative to health. Both concentration-based and intake-based methods are applied. The study indicates that the intake-based risk estimation benchmark is stricter than the exposure limit-based benchmark for carcinogens.     

Fine Particle (PM25) Measurement Methodology,Quality Assurance Procedures,and Pilot Results of the EXPOLIS Study

ABSTRACT

EXPOLIS is a European multicenter (Athens, Basel, Grenoble, Helsinki, Milan, and Prague) air pollution exposure study. It is the first international, population-based, large-scale study, where personal exposures to PM_{2 5} aerosol particles (together with volatile organic compounds and carbon monoxide) are being monitored. EXPOLIS is performed in six different centers across Europe, the sampled aerosol concentrations vary greatly, and the mi-croenvironmental samples are not collected with the same equipment as the personal samples. Therefore careful equipment selection, methods development and testing, and thorough quality assurance and quality control (QA & QC) procedures are essential for producing reliable and comparable PM_2.5 data. This paper introduces the equipment, the laboratory test results, the pilot results, the standard operating procedures, and the QA & QC procedures of EXPOLIS. Test results show good comparability and repeatability between personal and microenvironmen-tal monitors for PM2.5 at different concentration levels measured across Europe in EXPOLIS centers.     

A Field Intercomparison and Fundamental Characterization of Various Dust Samplers with a Reference Sampler

The European Economic Community Council Directive 80/779/EEC¹ describes air quality limit values and guide values for sulfur dioxide and suspended particulates. However, article 10, paragraph 1 does not define well enough the reference method required, amongst others, for the gravimetric measurement of suspended particulates. It is explicity stated in article 10, paragraph 5 of the directive, that “the commission shall, in selected locations in the member states and in cooperation with the latter, carry out studies on the sampling…of suspended particulates. These studies shall be designed in particular to promote the harmonization of methods of sampling and analysis of these pollutants.” Therefore, in a joint research program the Umweltbundesamt (grant #104 02263), the commission of European Communities (grant #84-B-6642-11-017-11-N) and the U.S. EPA (grant #2-43211-3580) funded the development of a reference dust sampler by the Fraunhofer-lnstitute of Toxicology and Aerosol Research (FhITA, in Hannover, Federal Republic of Germany) in order: ? to study the particle size distribution of ambient air aerosol at a number of selected sites;

? to compare the results obtained with the reference dust sampler with those of particle samplers operated in Europe and the United States;

? to verify the applicability of wind tunnel results to sampling behaviour in the free atmosphere.