Comparison of carbon balances between continuous-cover and clear-cut forestry in Sweden

Continuous-cover forestry (CCF) has been recognized for the production of multiple ecosystem services, and is seen as an alternative to clear-cut forestry (CF). Despite the increasing interest, it is still not well described how CCF would affect the carbon balance and the resulting climate benefit from the forest in relation to CF. This study compares carbon balances of CF and CCF, applied as two alternative land-use strategies for a heterogeneous Norway spruce (Picea abies) stand. We use a set of models to analyze the long-term effects of different forest management and wood use strategies in Sweden on carbon dioxide emissions and carbon stock changes. The results show that biomass growth and yield is more important than the choice of silvicultural system per se. When comparing CF and CCF assuming similar growth, extraction and product use, only minor differences in long-term climate benefit were found between the two principally different silvicultural systems.     

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.     

Model selection and evaluation for risk assessment of dioxin-contaminated sites

The general European population has a total intake of dioxins and dioxin-like chemicals near the limit recommended by the European Union, making additional exposure above background levels undesirable. For populations living near dioxin-contaminated sites, additional exposure may occur by intake of locally produced food, inhalation of particles, dermal contact with soils, or other exposure pathways. Risk assessment tools are required to estimate risks associated with contaminated sites and to set priorities for site remediation. Here, we review several multimedia models that can be applied as tools to support risk assessment. We then present a strategy to select, apply, evaluate, and adapt a model to address a specific situation. The case study we consider is a risk assessment of generic background dioxin exposure in Sweden, and we compare the predictions with environmental observations and exposure data from Sweden. Arguments are presented for selecting the CalTOX model for this case study. We demonstrate the application, evaluation, and adaptation of the model and discuss the requirements for extending the analysis to conduct risk assessment for subpopulations living near dioxin-contaminated sites.     

Environmentally friendly assessment of organic compound bioaccessibility using sub-critical water

The evaluation of microbial availability of contaminants is of high importance for better reflecting the processes governing contaminant fate in soil and for establishing the risk associated with contaminated sites. A sub-critical water extraction technique was assessed for its potential to determine the microbially degradable fraction of [¹⁴C]phenanthrene-associated activity in two dissimilar soils at three different ageing times (14, 28 and 49 days). For the majority of determinations, no significant (p > 0.05) difference between sub-critical water-extracted ¹⁴C-activity at 160 °C and the fraction mineralized by catabolically active Pseudomonas sp. was observed. Collectively, the results suggested that the sub-critical water extraction technique was an appropriate technique for predicting the biodegradable fraction of phenanthrene-associated ¹⁴C-activity in dissimilar soils following increasing soil-contaminant contact time.     

Assessing biodegradation potential of PAHs in complex multi-contaminant matrices

This study sought to extend validation of a cyclodextrin based extraction method for the assessment of PAH-biodegradation potential to complex multi-contaminant matrices. To this end, four reference materials (RMs) were produced by blending, in different proportions, soils impacted with diesel, lubricating oil and spent oxide. These reference materials had modest ∑PAH (16 US EPA) concentrations that ranged from 5.6 ± 0.5 to 44.4 ± 4.5 mg kg⁻¹. However, extractable petroleum hydrocarbon (EPH) concentrations were comparatively high (up to 2520 ± 204 mg kg⁻¹). To complement these RMs, two further soils from a municipal gas plant (MGP) with highly elevated concentration of PAHs ranging from 877 ± 52 to 2620 ± 344 mg kg⁻¹ were also tested. Results showed, regardless of matrix complexity, that PAH biodegradation within the four RM substrates, and two MGP soils correlated well with biodegradation predicted by hydroxypropyl-β-cyclodextrin (HPCD) extraction.     

Large variation in breast milk levels of organohalogenated compounds is dependent on mother's age, changes in body composition and exposures early in life

We identified factors that are important determinants of body burdens (breast milk levels) of polychlorinated biphenyls (PCBs), dioxins (polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs)) and polybrominated diphenyl ethers (PBDEs). PCBs, PCDD/Fs and PBDEs were analysed in breast milk from up to 325 first-time mothers in Uppsala, Sweden, who delivered between 1996 and 2006. Hierarchical clustering was used as a method for identification of groups of compounds with common sources of exposure and similar toxicokinetics. Based on correlations between levels of single compounds/congeners in breast milk, distinctly separated clusters were formed, strongly dependent on structural similarities of the organohalogen molecules. In a multiple regression model, levels of PCBs (except PCB 28), PCDD/Fs and BDE-153 were positively associated with age of the mother and weight loss after delivery and inversely associated with pre-pregnancy BMI (body mass index) and weight gain during pregnancy. Higher levels of mono-ortho PCB TEQ, non-ortho PCB TEQ and BDE-153 in milk were found among women with high physical activity. Women who were breastfed during infancy and grew up on the Baltic coast of Sweden, with high availability of contaminated fish from the Baltic sea, had higher levels of PCBs and PCDD/Fs in breast milk indicating that exposure early in life from breast milk and contaminated fish may still affect body burdens at the time of pregnancy. The importance of current consumption of fatty Baltic fish as a source of exposure was supported by the positive association with breast milk levels of mono-ortho PCB TEQ, PCDF TEQ and BDE-153. The results show that, in contrast to the lower brominated PBDE congeners, the hexa-brominated BDE-153 resembles the chlorinated compounds with regards to determinants in breast milk. This suggests that some of the PBDEs may have toxicokinetic properties and that are similar to the PCBs and PCDD/Fs. Our results show that a few simple advices to women regarding weight changes in connection with pregnancy and consumption of contaminated fatty fish during the whole lifetime may lower the levels of dioxins in breast milk by up to 60%.     

Report: waste refinery in the municipality of Bor?s.

This paper briefly describes waste treatment trends in Sweden and describes an example of state-of-the-art treatment in a local integrated waste treatment system (Bor?s). The focus is on treatment of household waste, to illustrate what can be done to establish a sustainable waste treatment system with high recovery of materials and energy. The various processes have resulted in a low amount of landfilled household waste, and high proportions of recovered energy and materials. Heat, electricity, vehicle fuel and fertilizers, metals and construction materials are recovered from the local waste in Bor?s, with less than 4% of domestic waste being sent to landfill.     

A modeling analysis of the sustainability of ecotourism in Belize

Over the past two decades, ecotourism has emerged as an important conservation strategy, especially in the Tropics where a diversity of species and habitats are threatened by traditional forms of development. However, questions remain about the sustainability of ecotourism in terms of distributions of income to local people and degradation of ecosystems visited by the ecotourists. In this study, a computer simulation model was used to study the possible long-term patterns of ecotourism at the country scale for Belize, Central America. The model includes state variables for natural ecosystems and tourism infrastructure with a submodel for global oil supply. It was simulated over a 100-year period as an EXCEL spreadsheet with a time step of 1?year. In all of the simulations, a decline over time in income from ecotourists was found due to increases in the price of oil and due to environmental impacts by tourism. Conservation efforts can slow the declines, but ultimately, the system is shown to be unsustainable. The results are discussed in the context of long-term conservation potential in Belize.     

Farmers’ markets – linking food consumption and the ecology of food production?

Urban and industrialised societies usually involve little connection between consumers and the resource base upon which the production of goods depends. Changing this situation could potentially enhance social and ecological sustainability. This study explored ecological aspects of the educational role of local food supply, with the aim of identifying signs of enhanced consumer understanding or awareness of the ecology of food production resulting from producer–consumer interaction. A series of qualitative interviews were carried out with customers at a farmers’ market in Stockholm. The results showed that the interviewees were mainly concerned with quality, price and taste, and not production conditions. In addition, a number of interviewees experienced a sense of trust when shopping at the market. We found few examples of contributions to ecological knowledge among customers at the market, but there were some examples of learning opportunities. The local food supplied by the market reminded customers of the seasonality of production. Stallholders also provided information on how to store, prepare and cook vegetables, which may encourage a change in diet that is preferable from an environmental standpoint.     

Can NO(2) be used to indicate ambient and personal levels of benzene and 1,3-butadiene in air?

The aim of this study was to investigate the relation between two toxic volatile organic compounds, 1,3-butadiene and benzene, and a commonly used indicator of vehicle exhaust fumes, NO(2). This was to see if NO(2) can be used to indicate personal exposure to carcinogenic substances or at least estimate ambient levels measured at a stationary point. During the winter of 2001, 40 randomly selected persons living in the City of Umea (in the north of Sweden) were recruited to the study. Personal measurements of 1,3-butadiene, benzene and NO(2) were performed for one week, and were repeated for 20 of the 40 participants. Additional information was gathered using a diary kept by each participant. During the same time period weekly stationary measurements were performed at one urban background station and one street station in the city centre. The results from the personal measurements showed a negligible association of NO(2) with 1,3-butadiene (r= 0.06) as well as with benzene (r= 0.10), while the correlation coefficient between 1,3-butadiene and benzene was high and significant (r= 0.67). In contrast to the personal measurements, the stationary measurements showed strong relations between 1,3-butadiene, benzene and NO(2) both within and in-between the street and urban background station. This study supports NO(2) as a potential indicator for 1,3-butadiene and benzene levels in streets or urban background air, while the weak relations found for the personal measurements do not support the use of NO(2) as an indicator for personal 1,3-butadiene and benzene exposure.