Automated and continuous redox potential measurements in soil

Redox potential (Eh) describes the electrical state of a matrix. In soils, Eh is an important parameter controlling the persistence of many organic and inorganic compounds. A popular, but also criticized, manual measuring method makes use of a small tip of Pt placed on a copper wire that is placed in the soil; a reference electrode is placed in the same soil at a fixed distance. Fluctuations in redox potential values measured in the soil can be very large and depth-dependent. This will be overlooked when making single-point measurements. We developed the datalogger Hypnos 2.0 for continuous redox potential and temperature measurements at various depths in the soil and without disturbance of the site. Hypnos is field-deployable, relatively cheap, and runs on batteries. The datalogger can use a "sleep mode" between sampling events. In sleep mode, there is no constant voltage on the Pt wire or the reference electrode, but there is only a short pulse during sampling. We did not measure an effect of this short pulse on the measured redox potential. In sandy soils in mesocosms and in a salt marsh soil we measured changes in the Eh as large as from -400 to +100 mV within 4 d, and daily cycles of 200 mV. Both absolute redox potential values and their diurnal variations were depth-dependent. Because single redox measurements are insufficient in describing redox conditions in some soil systems, Hypnos can be a powerful tool when studying the effects of fluctuating redox conditions on metal availability and pollutant degradation.     

I will not go,I cannot go: cultural and social limitations of disaster preparedness in Asia,Africa, and Oceania

While much work has been invested in addressing the economic and technical basis of disaster preparedness, less effort has been directed towards understanding the cultural and social obstacles to and opportunities for disaster risk reduction. This paper presents local insights from five different national settings into the cultural and social contexts of disaster preparedness. In most cases, an early warning system was in place, but it failed to alert people to diverse environmental shocks. The research findings show that despite geographical and typological differences in these locations, the limitations of the systems were fairly similar. In Kenya, people received warnings, but from contradictory systems, whereas in the Philippines and on the island of Saipan, people did not understand the messages or take them seriously. In Bangladesh and Nepal, however, a deeper cultural and religious reasoning serves to explain disasters, and how to prevent them or find safety when they strike.     

Assessment of the toxicity of mixtures of halogenated dibenzo-p-dioxins and dibenzofurans by use of toxicity equivalency factors (TEF)

In March 1988 the authors completed a report on the risk assessment of mixtures of halogenated dibenzo-p-dioxins and dibenzofurans at the request of the National Institute of Public Health and Environmental Protection in the Netherlands. Based on a study of the current knowledge of these compounds, a set of toxicity equivalency factors was proposed for use in such risk assessments. This paper presents the section of this report that deals with the literature on the effects of these compounds and the choice of toxicity equivalency factors. The uncertanties in the selection and application of toxicity equivalency factors are discussed.     

A study on the effect of trees on gas explosions

The downstream as well as the upstream oil and gas industry has for a number of years been aware of the potential for flame acceleration and overpressure generation due to obstacles in gas clouds caused by leaks of flammable substances. To a large extent the obstacles were mainly considered to be equipment, piping, structure etc. typically found in many installations. For landbased installations there may however also be a potential for flame acceleration in regions of vegetation, like trees and bushes. This is likely to have been the case for the Buncefield explosion that occurred in 2005 (Buncefield Major Incident Investigation Board, 2008), which led to the work described in the present paper. The study contains both a numerical and an experimental part and was performed in the period 2006–2008 (Bakke and Brewerton, 2008, Van Wingerden and Wilkins, 2008).The numerical analysis consisted of modelling the Buncefield tank farm and the surrounding area with FLACS. The site itself was not significantly congested and it was not expected to give rise to high overpressures in case of a hydrocarbon leak. However, alongside the roads surrounding the site (Buncefield Lane and Cherry Tree Lane), dense vegetation in the form of trees and bushes was included in the model. This was based on a site survey (which was documented by video) performed in the summer of 2006.A large, shallow, heavier-than-air gas cloud was defined to cover part of the site and surroundings. Upon ignition a flame was established in the gas cloud. This flame accelerated through the trees along the surrounding roads, and resulted in high overpressures of several barg being generated by FLACS. This is to the authors’ knowledge the first time a possible effect of vegetation on explosions has been demonstrated by 3D analyses.As a consequence of these results, and since the software had been validated against typical industrial congestion rather than dense vegetation, a set of experiments to try to demonstrate if these effects were physical was carried out as well. The test volume consisted of a plastic tunnel, 20 m long with a semi-circular cross-section 3.2 m in diameter allowing for representing lanes of vegetation. The total volume of the tent was approximately 80.4 m³. The experimental programme involved different degrees of vegetation size, vegetation density (blocking ratio) and number of vegetation lanes (over the full length of the tunnel). The experiments were performed with stoichiometric propane–air mixtures resulting in continuously accelerating flames over the full length of the tunnel for some of the scenarios investigated.The main conclusions of the study are that trees can have an influence on flame acceleration in gas–air clouds, and that advanced models such as FLACS can be used to study such influence. More research is needed, however, because even if FLACS predicts flame acceleration in dense vegetation, no evidence exists that applying the code to trees rather than rigid obstacles provides results of acceptable accuracy.     

Assessment of bioavailable PAH, PCB and OCP concentrations in water, using semipermeable membrane devices (SPMDs), sediments and caged carp

Bioavailable water concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were assessed at several freshwater sites in and around the city of Amsterdam. Carp (Cyprinus carpio) were caged for 4 weeks at 10 sites, together with semipermeable membrane devices (SPMDs). In addition, sediment samples were taken at each site. SPMDs and sediments were analysed for PAHs, PCBs and OCPs. Carp muscle tissues were analysed for PCBs and OCP, while PAH metabolites were assessed in fish bile. Contaminant concentrations in the water phase were estimated using three different methods: 1. Using fish tissue concentrations and literature bioconcentration factors (BCFs), 2. Using SPMD levels and a kinetic SPMD uptake model, and 3. Using sediment levels and literature sorption coefficients (K_ocs). Since PAH accumulation in fish is not considered an accurate indicator of PAH exposure, calculated aqueous PAH concentrations from SPMD data were compared with semiquantitatively determined biliary PAH metabolite levels. Contaminant concentrations in the water phase estimated with fish data (Cw_fish) and SPMD data (Cw_spmd) were more in line for compounds with lower K_ow than for compounds with higher K_ow values. This indicates that the assumption of fish–water sorption equilibrium was not valid. At most sites, sediment-based water levels (Cw_sed) were comparable with the Cw_spmd, although large differences were observed at certain sites. A significant correlation was observed between biliary PAH metabolite levels in fish and aqueous PAH concentrations estimated with SPMD data, suggesting that both methods may be accurate indicators of PAH exposure in aquatic ecosystems.     

Application of the City Blueprint Approach to assess the challenges of water management and governance in Quito (Ecuador)

In this paper, we provide an assessment of the challenges of water, waste and climate change in the city of Quito by performing the City Blueprint Approach consisting of three assessment frameworks: (1) the Trends and Pressure Framework (TPF), (2) the City Blueprint Framework (CBF) and (3) the water Governance Capacity Framework (GCF). The TPF summarizes the main social, environmental and financial aspects that may affect urban water management. The CBF provides a clear overview of sustainable urban water management performance and its bottlenecks in municipalities and regions. The GCF comprises nine governance conditions which each consist of three indicators. The GCF provides insight in the most effective improvements to increase the governance capacity to address the identified urban water challenges. Our results show that poor wastewater treatment and long-term drinking water security are Quito’s main water challenges that may be jeopardized given the city’s rapid urbanization and economic pressure. The GCF analysis reveals that cooperation between stakeholders, implementing capacity and citizens’ awareness are the most important conditions for further development to find adequate solutions for Quito’s long-term drinking water security. We also suggest that more attention should be drawn to the transparency, accountability and participation principles. The results of Quito show that the City Blueprint Approach can serve as an affordable quick-scan to facilitate cities in their strategic planning to reach their sustainable development goals.     

The acute toxicity of chlorobenzenes for earthworms (Eisenia andrei) in different exposure systems

Earthworms (Eisenia andrei) were exposed to different concentrations of two chlorobenzenes (1,2,3-trichloro- and pentachlorobenzene) using different routes of administration: in water, in soil, via food and on filter paper. Except for the contact paper toxicity test, lethal body burdens (LBBs) measured in these different exposure systems were similar for the same test chemical. LBBs for 1,2,3-trichlorobenzene varied between 0.44 and 2.1 μmol/g and for pentachlorobenzene between 1.29 and 2.34 μmol/g. These values correspond with literature data for fish. For 1,4-dichloro- and 1,2,3,4-tetrachlorobenzene LBBs measured with the contact paper toxicity test were 0.33 and 3.2 μmol/g, respectively. Exposure to hexachlorobenzene and hexabromobenzene using the contact toxicity test did not result in death within 48 hours.     

Spatial and temporal analysis of pesticides concentrations in surface water: pesticides atlas

Dutch water boards have a well-established program for monitoring pesticide contamination of surface waters. These monitoring data have been processed into a graphic format accessible online and designed to provide insight into pesticide presence in Dutch surface waters and trends over time: the Pesticides Atlas (http://www.pesticidesatlas.nl). With this tool one can easily get maps of where a pesticide is being measured and where it might possibly constitute an environmental problem over the years. Presently, results of the periods 1997/1998 until 2005/2006 are available at the level of individual active ingredients. At a national level, the percentage of pesticides concentrations that exceed the maximum tolerable risk has declined 30% to 38% over the years 2003/2004 compared with 1997/1998. This means that surface water quality in the Netherlands has improved with respect to pesticides, however there are still many locations at which the measured concentrations exceed the environmental quality standards. The results on linking land use to pesticides concentrations were shown to assist in optimization of monitoring programs. By developing the present Internet tool, many new opportunities for environmental risk assessment and risk management were identified, e.g. optimization of monitoring strategies and communication to policymakers.     

Little effect of excessive biofouling on the uptake of organic contaminants by semipermeable membrane devices

The effects of water flow rate and antifouling agents on the extent of biofouling and on the uptake of non-polar organic contaminants by semipermeable membrane devices (SPMDs) were studied during four field experiments in the Western Wadden Sea. Biofouling densities on the sampler surface ranged from 0.3 to 16 g dry weight dm⁻². Water sampling rates were estimated from the dissipation rates of performance reference compounds (PRCs). The antifouling agents Irgarol and capsaicin (33 mg per ml triolein) had no noticeable effect on the extent of fouling, and caused only a 5–10% increase in the absorbed amounts. Enhanced flow rates had only a minimal effect on the amount of biofouling, but caused the water sampling rates to increase by a factor of 1.2–2. Increases in PRC-derived sampling rates were reflected by increases in the absorbed amounts for compounds that were in the linear uptake stage of the sampling process. The results imply (1) that extreme biofouling does not always result in reduced sampling rates, (2) that extreme biofouling does not preclude the existence of flow effects on the sampling rates, and (3) that differences in uptake rates are quantitatively reflected by the dissipation rates of PRCs.     

Spatial variability of nitrogen dioxide and formaldehyde and residential exposure of children in the industrial area of Viadana,Northern Italy

Environmental Science and Pollution Research - Chipboard production is a source of ambient air pollution. We assessed the spatial variability of outdoor pollutants and residential exposure of...