Long-term effects of short-term perturbation in a subalpine grassland

Theoretical advances and short-term experimental studies have furthered our understanding of how ecosystems respond to perturbation. However, there are few well-replicated experimental studies that allow an assessment of long-term responses. Results from a controlled, large-scale field experiment in a subalpine grassland near Interlaken, Switzerland, show that 2-4 years of liming (Ca: 40 g x m(-2) x yr(-1)) still significantly affected the composition of the vegetation and the soil microbial community nearly 70 years after the treatments were imposed, whereas NPK fertilization (8 g x m(-2) x yr(-1)) only marginally affected vegetation composition. The exchangeable content of Ca ions and soil pH were higher in limed plots but were unaffected in fertilized plots. Plant species and PLFAs (phospholipid fatty acids) indicating low pH values were found in higher abundance in the unlimed plots, suggesting that the long-lasting effects of liming on the above- and belowground communities were mediated through changes in soil pH. The results of this long-term study indicate that the resilience of mountain ecosystems may be particularly low in response to perturbations that substantially alter soil pH or other key determinants of belowground processes.     

Factors Related to Spatial Patterns of Rural Land Fragmentation in Texas

Fragmentation of family-owned farms and ranches has been identified as the greatest single threat to wildlife habitat, water supply, and the long-term viability of agriculture in Texas. However, an integrative framework for insights into the pathways of land use change has been lacking. The specific objectives of the study are to test the hypotheses that the nonagricultural value (NAV) of rural land is a reliable indicator of trends in land fragmentation and that NAV in Texas is spatially correlated with population density, and to explore the idea that recent changes in property size patterns are better represented by a categorical model than by one that reflects incremental changes. We propose that the State-and-Transition model, developed to describe the dynamics of semi-arid ecosystems, provides an appropriate conceptual framework for characterizing categorical shifts in rural property patterns. Results suggest that changes in population density are spatially correlated with NAV and farm size, and that rural property size is spatially correlated with changes in NAV. With increasing NAV, the proportion of large properties tends to decrease while the area represented by small properties tends to increase. Although a correlation exists between NAV and population density, it is the trend in NAV that appears to be a stronger predictor of land fragmentation. The empirical relationships established herein, viewed within the conceptual framework of the State-and-Transition model, can provide a useful tool for evaluating land use policies for maintaining critical ecosystem services delivered from privately owned land in private land states, such as Texas.     

Pyrrolizidine alkaloid content in <Emphasis Type="Italic">Senecio</Emphasis>: ontogeny and developmental constraints

Summary. The ontogeny of pyrrolizidine alkaloid (PA) synthesis and constraints on defence level during the seedling stage were examined in the annual Senecio vulgaris and the monocarpic perennial Senecio jacobaea. In both species, PAs were actively synthesized from the onset of seedling growth so that juvenile stages did not go through an undefended stage. Roots are known to be the exclusive sites where PAs are produced. Root biomass was the single most important biomass parameter explaining variation in total PAs per seedling. All correlation coefficients between—relative growth rate and PA concentration were negative, but none was significant. However, a significant negative—correlation was found between shoot to root ratio and PA concentration in S. jacobaeaseedlings, suggesting a dilution effect of the PAs. Earlier studies have shown that the shoot to root ratio is positively correlated with relative growth—rate of established S. jacobaea plants. It is therefore suggested that young S. jacobaea plants with a high shoot to root ratio and hence a high growth capacity necessarily have lower PA defence levels than plants with a low shoot to root ratio. Received 10 July 2002; accepted 16 November 2002.     

Chlorinated paraffins in indoor air and dust: concentrations, congener patterns, and human exposure

Chlorinated paraffins (CPs) are large production volume chemicals used in a wide variety of commercial applications. They are ubiquitous in the environment and humans. Human exposure via the indoor environment has, however, been barely investigated. In the present study 44 indoor air and six dust samples from apartments in Stockholm, Sweden, were analyzed for CPs, and indoor air concentrations are reported for the first time. The sumCP concentration (short chain CPs (SCCPs) and medium chain CPs (MCCPs)) in air ranged from <5-210 ng m(-3) as quantified by gas chromatography coupled to electron ionization tandem mass spectrometry (GC/EI-MS/MS). Congener group patterns were studied using GC with electron capture negative ionization MS (GC/ECNI-MS). The air samples were dominated by the more volatile SCCPs compared to MCCPs. SumCPs were quantified by GC/EI-MS/MS in the dust samples at low μg g(-1) levels, with a chromatographic pattern suggesting the prevalence of longer chain CPs compared to air. The median exposure to sumCPs via the indoor environment was estimated to be ~1 μg day(-1) for both adults and toddlers. Adult exposure was dominated by inhalation, while dust ingestion was suggested to be more important for toddlers. Comparing these results to literature data on dietary intake indicates that human exposure to CPs from the indoor environment is not negligible.     

Trihalomethane formation during water disinfection in four water supplies in the Somes river basin in Romania

Background, aim and scope

After the discovery of chloroform in drinking water, an extensive amount of work has been dedicated to the factors influencing the formation of halogenated disinfections by-products (DBPs). The disinfection practice can vary significantly from one country to another. Whereas no disinfectant is added to many water supplies in Switzerland or no disinfectant residual is maintained in the distribution system, high disinfectant doses are applied together with high residual concentrations in the distribution system in other countries such as the USA or some southern European countries and Romania. In the present study, several treatment plants in the Somes river basin in Romania were investigated with regard to chlorine practice and DBP formation (trihalomethanes (THMs)). Laboratory kinetic studies were also performed to investigate whether there is a relationship between raw water dissolved organic matter, residual chlorine, water temperature and THM formation.

Materials and methods

Drinking water samples were collected from different sampling points in the water treatment plant (WTP) from Gilau and the corresponding distribution system in Cluj-Napoca and also from Beclean, Dej and Jibou WTPs. The water samples were collected once a month from July 2006 to November 2007 and stored in 40-mL vials closed with Teflon lined screw caps. Water samples were preserved at 4°C until analysis after sodium thiosulfate (Na₂S₂O₃) had been added to quench residual chlorine. All samples were analysed for THMs using headspace GC-ECD between 1 and 7 days after sampling. The sample (10 mL) was filled into 20-mL headspace vials and closed with a Teflon-lined screw cap. Thereafter, the samples were equilibrated in an oven at 60°C for 45 min. The headspace (1 mL) was then injected into the GC (Cyanopropylphenyl Polysiloxane column, 30 m × 53 mm, 3 μm film thickness, Thermo Finnigan, USA). The MDLs for THMs were determined from the standard deviation of eight standards at 1 μg/L. The MDLs for CHCl₃, CHBrCl₂, CHBr₂Cl and CHBr₃ were 0.3, 0.2, 0.3 and 0.6 μg/L, respectively. All kinetic laboratory studies were carried out only with water from the WTP Gilau. The experiments were conducted under two conditions: baseline conditions (pH 7, 21°C, 2.5 mg/L Cl₂) to gain information about the change of the organic matter in the raw water and seasonally variable conditions to simulate the actual process at the treatment plant and the distribution system.

Results and discussion

This study shows that the current chlorination practice in the investigated plants complies with the THM drinking water standards of the EU. The THM concentrations in all samples taken in the four treatment plants and distributions systems were below the EU drinking water standard for TTHMs of 100 μg/L. Due to the low bromide levels in the raw waters, the main THM formed in the investigated plants is chloroform. It could also be seen that the THM levels were typically lower in water supplies with groundwater as their water resource. In one plant (Dej) with a pre-ozonation step, a significantly lower (50%) THM formation during post-chlorination was observed. Laboratory chlorination experiments revealed a good correlation between chloroform formation and the consumed chlorine dose. Also, these experiments allowed a semi-quantative prediction of the chloroform formation in the distribution system of Cluj-Napoca.

Conclusions

CHCl₃ was the most important trihalomethane species observed after the chlorination of water in all of the sampled months. However, TTHM concentrations did not exceed the maximum permissible value of 100 μg/L (EU). The THM formation rates in the distribution system of Cluj-Napoca have a high seasonal variability. Kinetic laboratory experiments could be used to predict chloroform formation in the Cluj-Napoca distribution system. Furthermore, an empirical model allowed an estimation of the chloroform formation in the Gilau water treatment plant.

     

Exploring the use of computer models in participatory integrated assessment – experiences and recommendations for further steps

Integrated assessment (IA) can be defined as a structured process of dealing with complex issues, using knowledge from various scientific disciplines and/or stakeholders, such that integrated insights are made available to decision makers (J. Rotmans, Enviromental Modelling and Assessment 3 (1998) 155). There is a growing recognition that the participation of stakeholders is a vital element of IA. However, only little is known about methodological requirements for such participatory IA and possible insights to be gained from these approaches. This paper summarizes some of the experiences gathered in the ULYSSES project, which aims at developing procedures that are able to bridge the gap between environmental science and democratic policy making for the issue of climate change. The discussion is based on a total of 52 IA focus groups with citizens, run in six European and one US city. In these groups, different computer models were used, ranging from complex and dynamic global models to simple accounting tools. The analysis in this paper focuses on the role of the computer models. The findings suggest that the computer models were successful at conveying to participants the temporal and spatial scale of climate change, the complexity of the system and the uncertainties in our understanding of it. However, most participants felt that the computer models were less instrumental for the exploration of policy options. Furthermore, both research teams and participants agreed that despite considerable efforts, most models were not sufficiently user-friendly and transparent for being accessed in an IA focus group. With that background, some methodological conclusions are drawn about the inclusion of the computer models in the deliberation process. Furthermore, some suggestions are made about how given models should be adapted and new ones developed in order to be helpful for participatory IA. This revised version was published online in July 2006 with corrections to the Cover Date.     

Quantifying food losses and the potential for reduction in Switzerland

A key element in making our food systems more efficient is the reduction of food losses across the entire food value chain. Nevertheless, food losses are often neglected. This paper quantifies food losses in Switzerland at the various stages of the food value chain (agricultural production, postharvest handling and trade, processing, food service industry, retail, and households), identifies hotspots and analyses the reasons for losses. Twenty-two food categories are modelled separately in a mass and energy flow analysis, based on data from 31 companies within the food value chain, and from public institutions, associations, and from the literature. The energy balance shows that 48% of the total calories produced (edible crop yields at harvest time and animal products, including slaughter waste) is lost across the whole food value chain. Half of these losses would be avoidable given appropriate mitigation measures. Most avoidable food losses occur at the household, processing, and agricultural production stage of the food value chain. Households are responsible for almost half of the total avoidable losses (in terms of calorific content).     

Assessing the Cr(VI) reduction efficiency of a permeable reactive barrier using Cr isotope measurements and 2D reactive transport modeling

In Thun, Switzerland, a permeable reactive barrier (PRB) for Cr(VI) reduction by gray cast iron was installed in May 2008. The PRB is composed of a double array of vertical piles containing iron shavings and gravel. The aquifer in Thun is almost saturated with dissolved oxygen and the groundwater flow velocities are ca. 10-15m/day. Two years after PRB installation Cr(VI) concentrations still permanently exceed the Swiss threshold value for contaminated sites downstream of the barrier at selected localities. Groundwater δ(53/52)Cr(SRM979) measurements were used to track Cr(VI) reduction induced by the PRB. δ(53/52)Cr(SRM979) values of two samples downstream of the PRB showed a clear fractionation towards more positive values compared to four samples from the hotspot, which is clear evidence of Cr(VI) reduction induced by the PRB. Another downstream sample did not show a shift to more positive δ(53/52)Cr(SRM979) values. Because this latter location correlates with the highest downstream Cr(VI) concentration it is proposed that a part of the Cr(VI) plume is bypassing the barrier. Using a Rayleigh fractionation model a minimum present-day overall Cr(VI) reduction efficiency of ca. 15% was estimated. A series of 2D model simulations, including the fractionation of Cr isotopes, confirm that only a PRB bypass of parts of the Cr(VI) plume can lead to the observed values. Additionally, the simulations revealed that the proposed bypass occurs due to an insufficient permeability of the individual PRB piles. It is concluded that with this type of PRB a complete and long-lasting Cr(VI) reduction is extremely difficult to achieve for Cr(VI) contaminations located in nearly oxygen and calcium carbonate saturated aquifer in a regime of high groundwater velocities. Additional remediation action would limit the environmental impact and allow to reach target concentrations.     

Environmental occurrence and fate of semifluorinated n-alkanes in snow and soil samples from a ski area

Semifluorinated n-alkanes (SFAs) with carbon chain lengths of 22 to approximately 36 atoms are present in fluorinated ski waxes to reduce the friction between ski base and snow, resulting in a better glide. Semifluorinated n-alkenes (SFAenes) are byproducts in the production process of SFAs and are also found in ski waxes. Snow and soil samples from a ski area in Sweden were taken after a large skiing competition and after snowmelt, respectively, and analyzed for SFAs and SFAenes. Single analyte concentrations in snow (analyzed as melt water) ranged from a few ng L⁻¹ up to 300 μg L⁻¹. ∑SFA concentrations decreased significantly from the start to the finish of the ski trail. Single analyte concentrations in soil ranged up to 9 ng g⁻¹ dw. ∑SFA concentrations in soil did not show a trend along the ski trail. This may be due to the fact that concentrations in soil, although strongly influenced by the competition, reflect inputs during the whole skiing season. The chemical inventory in snow was greater than the inventory in soil for shorter chain SFAs (C₂₂C₂₈) and for all SFAenes. Additionally, a significant change in SFA patterns between snow and soil samples was found. These observations suggested volatilization of shorter chain SFAs and of SFAenes during snowmelt. Evidence for long-term accumulation of SFAs in surface soil over several skiing seasons was not found.