Modelling the fate of hydrophobic organic contaminants in a boreal forest catchment: A cross disciplinary approach to assessing diffuse pollution to surface waters

The fate of hydrophobic organic compounds (HOCs) in soils and waters in a northern boreal catchment was explored through the development of a chemical fate model in a well-characterised catchment system dominated by two land types: forest and mire. Input was based solely on atmospheric deposition, dominated by accumulation in the winter snowpack. Release from soils was governed by the HOC concentration in soil, the soil organic carbon fraction and soil-water DOC content. The modelled export of selected HOCs in surface waters ranged between 11 and 250 ng day⁻¹ during the snow covered period, compared to 200 and 9600 ng/d during snow-melt; highlighting the importance of the snow pack as a source of these chemicals. The predicted levels of HOCs in surface water were in reasonable agreement to a limited set of measured values, although the model tended to over predict concentrations of HOCs for the forested sub-catchment, by over an order of magnitude in the case of hexachlorobenzene and PCB 180. This possibly reflects both the heterogeneity of the forest soils and the complicated and changing hydrology experienced between the different seasons.     

City breathability and its link to pollutant concentration distribution within urban-like geometries

This paper is devoted to the study of pollutant concentration distribution within urban-like geometries. By applying efficiency concepts originally developed for indoor environments, the term ventilation is used as a measure of city “breathability”. It can be applied to analyse pollutant removal within a city in operational contexts. This implies the evaluation of the bulk flow balance over the city and of the mean age of air. The influence of building packing density on flow and pollutant removal is, therefore, evaluated using those quantities. Idealized cities of regular cubical buildings were created with packing density ranging from 6.25% to 69% to represent configurations from urban sprawl to compact cities. The relative simplicity of these arrangements allowed us to apply the Computational Fluid Dynamics (CFD) flow and dispersion simulations using the standard k–? turbulence model. Results show that city breathability within the urban canopy layer is strongly dependent from the building packing density. At the lower packing densities, the city responds to the wind as an agglomeration of obstacles, at larger densities (from about 44%) the city itself responds as a single obstacle. With the exception of the lowest packing density, airflow enters the array through lateral sides and leaves throughout the street top and flow out downstream. The air entering through lateral sides increases with increasing packing density.At the street top of the windward side of compact building configurations, a large upward flow is observed. This vertical transport reduces over short distance to turn into a downward flow further downstream of the building array. These findings suggest a practical way of identifying city breathability. Even though the application of these results to real scenarios require further analyses the paper illustrates a practical framework to be adopted in the assessment of the optimum neighbourhood building layout to minimize pollution levels.     

Improving the layout of recycling centres by use of lean production principles

There has been increased focus on recycling in Sweden during recent years. This focus can be attributed to external environmental factors such as tougher legislation, but also to the potential gains for raw materials suppliers. Recycling centres are important components in the Swedish total recycling system. Recycling centres are manned facilities for waste collection where visitors can bring, sort and discard worn products as well as large-sized, hazardous, and electrical waste. The aim of this paper was to identify and describe the main flows and layout types at Swedish recycling centres. The aim was also to adapt and apply production theory for designing and managing recycling centre operations. More specifically, this means using lean production principles to help develop guidelines for recycling centre design and efficient control.Empirical data for this research was primarily collected through interviews and questionnaires among both visitors and employees at 16 Swedish recycling centres. Furthermore, adapted observation protocols have been used in order to explore visitor activities. There was also close collaboration with a local recycling centre company, which shared their layout experiences with the researchers in this project.The recycling centres studied had a variety of problems such as queues of visitors, overloading of material and improper sorting. The study shows that in order to decrease the problems, the recycling centres should be designed and managed according to lean production principles, i.e. through choosing more suitable layout choices with visible and linear flows, providing better visitor information, and providing suitable technical equipment. Improvements can be achieved through proper planning of the layout and control of the flow of vehicles, with the result of increased efficiency and capacity, shorter visits, and cleaner waste fractions. The benefits of a lean production mindset include increased visitor capacity, waste flexibility, improved sorting quality, shorter time for visits and improved working conditions.     

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.     

Simulating transport of non-Chernobyl (137)Cs and (90)Sr in the North Atlantic-Arctic region

The spatial and temporal distributions of the anthropogenic radionuclides (137)Cs and (90)Sr, originating from nuclear bomb testing and the Sellafield reprocessing plants in the Irish Sea, are simulated using a global version of the Miami Isopycnic Coordinate Ocean Model (MICOM). The physical model is forced with daily atmospheric re-analysed fields for the period 1950 to present. Comparison of temporal evolution of observed and simulated concentrations of (137)Cs have been conducted for the regions east of Scotland, west of central Norway and at the entrance of the Barents Sea. It follows that the radionuclides from the Sellafield discharge reach the Barents Sea region after 4-5 years, in accordance with observations. The simulation provides a detailed distribution and evolution of the radionuclides over the integration time. For the Atlantic waters off the coast of Norway and in the southern Barents Sea, the atmospheric fallout dominates over the Sellafield release up to the mid 1960s and from the early 1990s, whereas Sellafield is the main source for the two radionuclides in the 1970s and 1980s. It is furthermore argued that model systems like the one presented here can be used for future prediction of radioactive contaminations in the Nordic Seas and the Arctic Ocean, for instance under various global warming scenarios.     

Bone mineral density in male Baltic grey seal (Halichoerus grypus)

Bone mineral density (mg cm(-3)) was studied in male Baltic grey seals (4-23 years of age) by noninvasive computed tomography (pQCT). The material was grouped according to year of collection. Group A: 1850-1955, a period before the main introduction of organochlorines (OCs); Group B: 1965-1985, a period with very high OC contamination; and Group C: 1986-1997, a period with decreasing concentrations of OCs. The reproducibility of the measurements was good with a Coefficient of Variation (CV) ranging from 0.1% to 2.1%. Trabecular bone mineral density of the radius was significantly higher in specimens collected 1986-1997 than in those collected 1965-1985 (p < 0.05). Cortical bone mineral density of the mandible was significantly lower in specimens collected 1986-1997 compared with those collected 1850-1955 (p < 0.05). These results indicate different responses over time in trabecular and cortical bone. During the period of very high OC contamination (1965-1985), trabecular bone density was lowest, whereas cortical bone density was lowest in specimens collected 1985-1997, representing a period of fairly low OC contamination. The mechanisms behind these effects are not known. However, it can be assumed that OCs are involved. Information about residue levels of OCs in the studied individuals is lacking and, therefore, it was not possible to evaluate the impact of OCs in this respect.     

Heavy Metals in Stockholm Groundwater – Concentrations and Fluxes

Sampling of groundwater in theQuaternary deposits was carried out at 70 sitesin Stockholm for, among other things, metalanalyses. The objectives were to get a notion of the metal content and to get a basis for anestimation of the order of magnitude of thegroundwater transported metal contribution to themain surface water bodies in comparison to otherroutes. Thus, in three watershed areaswithin the Stockholm Town, groundwater flow andmetal concentration propagation were simulatedand metal fluxes were calculated. Theconcentrations of heavy metals were in generalfound to be very high in comparison withgroundwater in forested areas. This was mostpronounced for mercury (Hg) and copper (Cu). Themost remarkable result was a Hg concentration of4.57 g L^-1 in the vicinity of a closed downhospital. The annual contribution of heavy metals(kg) by groundwater to the main surface waterbodies was estimated to: As (2.2), Cd (0.20), Co(4.9), Cr (3.1), Cu (34), Hg (0.06), Ni (28), Pb(2.2) Zn (118). These fluxes are much smallerthan those in forest ecosystems, due to lowergroundwater recharge in urban areas, where agreat part of the runoff is diverted bylandsealing, drainage, tunnels etc. The modelingresults emphasize the importance of the sorptionprocesses indicating that the modeled areas arein a non-steady state condition. It also showsthat the sources generating elevatedconcentrations of the high adsorptive metals Pband Hg are likely to be nearby.     

Life cycle assessment of lithium-ion batteries for plug-in hybrid electric vehicles – Critical issues

The main aim of the study was to explore how LCA can be used to optimize the design of lithium-ion batteries for plug-in hybrid electric vehicles. Two lithium-ion batteries, both based on lithium iron phosphate, but using different solvents during cell manufacturing, were studied by means of life cycle assessment, LCA. The general conclusions are limited to results showing robustness against variation in critical data. The study showed that it is environmentally preferable to use water as a solvent instead of N-methyl-2-pyrrolidone, NMP, in the slurry for casting the cathode and anode of lithium-ion batteries. Recent years’ improvements in battery technology, especially related to cycle life, have decreased production phase environmental impacts almost to the level of use phase impacts. In the use phase, environmental impacts related to internal battery efficiency are two to six times larger than the impact from losses due to battery weight in plug-in hybrid electric vehicles, assuming 90% internal battery efficiency. Thus, internal battery efficiency is a very important parameter; at least as important as battery weight. Areas, in which data is missing or inadequate and the environmental impact is or may be significant, include: production of binders, production of lithium salts, cell manufacturing and assembly, the relationship between weight of vehicle and vehicle energy consumption, information about internal battery efficiency and recycling of lithium-ion batteries based on lithium iron phosphate.