Potential concerns related to using octadecyltrichlorosilane (OTS) in rendering soils and porous ceramics hydrophobic

The treatment of hydrophilic porous ceramics to render them hydrophobic and wetting to non-aqueous phase liquids (NAPLs) is frequently needed in multiphase flow experiments to control the flow or to measure the pressure of the NAPL. In addition, research dealing with soil wettability implies a need for hydrophobic or NAPL-wet soils. The traditional procedure, which has been widely used in literature, to render hydrophilic porous ceramics and soils hydrophobic is achieved by placing the hydrophilic solid in a 5% (by volume) octadecyltrichlorosilane (OTS) solution in ethanol followed by rinsing in ethanol. This research assesses the use of this procedure as it was found that this treatment procedure resulted in excess OTS on the surface of treated hydrophobic solids which can dissolve in an organic phase and in turn alter the wettability condition of adjacent hydrophilic soils. A modified procedure, which results in hydrophobic solids free of excess OTS, is presented.     

The impact of methanogenesis on flow and transport in coarse sand

The effects of biofilm growth and methane gas generation on water flow in porous media were investigated in an anaerobic two-dimensional sand-filled cell. Inoculation of the lower portion of the cell with a methanogenic culture and addition of methanol to the bottom of the cell led to biomass growth and formation of a gas phase. Biomass distributions in the water and on the sand in the cell were measured by protein analysis. The biofilm distribution on sand was observed by confocal laser scanning microscopy. The formation, migration, distribution and saturation of gases in the cell were visualized by the charge-coupled device (CCD) camera. The effects of biofilm and gas generation on water flow were separated by performing one tracer test in the presence of both biofilm and a gas phase and a second tracer test after removal of the gas phase through water flushing. The results of tracer tests demonstrated that flow and transport in the two-dimensional cell were significantly affected by both gas generation and biofilm growth. Gas generated at the bottom of the cell in the biologically active zone moved upwards in discrete fingers, so that gas phase saturations (gas-filled fraction of void space) in the biologically active zone at the bottom of the cell did not exceed 40-50%, while gas accumulation at the top of the cell produced gas phase saturations as high as 80%. The greatest reductions in water phase permeability, based on measurements of reductions in water phase saturations, occurred near the top of the box as a result of the gas accumulation. In contrast the greatest reductions in permeability due to biofilm growth, based on measurements of biofilm thickness, occurred in the most biologically active zone at the bottom of the cell, where gas phase saturations were approximately 40-50%, but permeability reductions due to biofilm growth were estimated to be 80-95%.     

Biomass consumption and CO2, CO and main hydrocarbon gas emissions in an Amazonian forest clearing fire

Biomass consumption and CO₂, CO and hydrocarbon gas emissions in an Amazonian forest clearing fire are presented and discussed. The experiment was conducted in the arc of deforestation, near the city of Alta Floresta, state of Mato Grosso, Brazil. The average carbon content of dry biomass was 48% and the estimated average moisture content of fresh biomass was 42% on wet weight basis. The fresh biomass and the amount of carbon on the ground before burning were estimated as 528 t ha^?1 and 147 t ha^?1, respectively. The overall biomass consumption for the experiment was estimated as 23.9%. A series of experiment in the same region resulted in average efficiency of 40% for areas of same size and 50% for larger areas. The lower efficiency obtained in the burn reported here occurred possibly due to rain before the experiment. Excess mixing ratios were measured for CO₂, CO, CH₄, C₂–C₃ aliphatic hydrocarbons, and PM_2.5. Excess mixing ratios of CH₄ and C₂–C₃ hydrocarbons were linearly correlated with those of CO. The average emission factors of CO₂, CO, CH₄, NMHC, and PM_2.5 were 1,599, 111.3, 9.2, 5.6, and 4.8 g kg^?1 of burned dry biomass, respectively. One hectare of burned forest released about 117,000 kg of CO₂, 8100 kg of CO, 675 kg of CH₄, 407 kg of NMHC and 354 kg of PM_2.5.     

The development of effects-based air quality management regimes

This paper considers the evolution of attempts to control and manage air pollution, principally but not exclusively focussing upon the challenge of managing air pollution in urban environments. The development and implementation of a range of air pollution control measures are considered. Initially the measures implemented primarily addressed point sources, a small number of fuel types and a limited number of pollutants. The adequacy of such a source-control approach is assessed within the context of a changing and challenging air pollution climate. An assessment of air quality management in the United Kingdom over a 50-year timeframe exemplifies the range of issues and challenges in contemporary air quality management. The need for new approaches is explored and the development and implementation of an effects-based, risk management system for air quality regulation is evaluated.     

A study of the total atmospheric sulfur dioxide load using ground-based measurements and the satellite derived Sulfur Dioxide Index

We present characteristics of the sulfur dioxide (SO₂) loading over Thessaloniki, Greece, and seven other selected sites around the world using SO₂ total column measurements from Brewer spectrophotometers together with satellite estimates of the Version 8 TOMS Sulfur Dioxide Index (SOI) over the same locations, retrieved from Nimbus 7 TOMS (1979–1993), Earth Probe TOMS (1996–2003) and OMI/Aura (2004–2006). Traditionally, the SOI has been used to quantify the SO₂ quantities emitted during great volcanic eruptions. Here, we investigate whether the SOI can give an indication of the total SO₂ load for areas and periods away from eruptive volcanic activity by studying its relative changes as a correlative measure to the SO₂ total column. We examined time series from Thessaloniki and another seven urban and non-urban stations, five in the European Union (Arosa, De Bilt, Hohenpeissenberg, Madrid, Rome) and two in India (Kodaikanal, New Delhi). Based on the Brewer data, Thessaloniki shows high SO₂ total columns for a European Union city but values are still low if compared to highly affected regions like those in India. For the time period 1983–2006 the SO₂ levels above Thessaloniki have generally decreased with a rate of 0.028 Dobson Units (DU) per annum, presumably due to the European Union's strict sulfur control policies. The seasonal variability of the SO₂ total column exhibits a double peak structure with two maxima, one during winter and the second during summer. The winter peak can be attributed to central heating while the summer peak is due to synoptic transport from sources west of the city and sources in the north of Greece. A moderate correlation was found between the seasonal levels of Brewer total SO₂ and SOI for Thessaloniki, Greece (R = 0.710–0.763) and Madrid, Spain (R = 0.691) which shows that under specific conditions the SOI might act as an indicator of the SO₂ total load.     

The variability of free tropospheric ozone over Beltsville,Maryland (39N, 77W) in the summers 2004–2007

Ozone profiles are often used to investigate day-to-day and year-to-year variability in origins of free tropospheric ozone. With this in mind, more than 50 ozonesonde launches were conducted in Beltsville, MD, during the summers of 2004 through 2007. Budgets of free tropospheric ozone were calculated for each ozone profile in the four summers using a laminar identification (LID) method and unusual episodes were analyzed with respect to meteorological variables. The laminar method showed that stratosphere-to-troposphere transport (ST) accounted for greater than 50% of the free tropospheric ozone column on 17% of days sampled, a more pronounced influence than regional convective and lightning (RCL) sources. The ST origins were confirmed with trajectories, and tracers (water vapor and potential vorticity). The amount of free tropospheric ozone from ST and RCL sources varied from year-to-year (up to 13%) and can be explained by differences in mean meteorological patterns. On average, almost 30% of the free tropospheric column was attributed to ST influence, about twice as much as RCL, although the LID method may not capture weeks-old lightning influences as in a chemical model. The prevalence of ST ozone in summertime Beltsville soundings was similar to six sounding sites in the IONS-04 campaign [Thompson, A.M., et al., 2007b. Intercontinental Transport Experiment Ozonesonde Network Study (IONS, 2004): 1. Summertime upper tropospheric/lower stratosphere ozone over northeastern North America. J. Geophys. Res. 112, D12S12; Thompson, A.M., et al., 2007c. Intercontinental Transport Experiment Ozonesonde Network Study (IONS, 2004): 2. Tropospheric ozone budgets and variability over northeastern North America. J. Geophys. Res. 112, D12S13.] and to statistics from a 30 year climatology of European soundings [Collette, A., Ancellet, G., 2005. Impact of vertical transport processes on the tropospheric ozone layering above Europe. Part II: Climatological analysis of the past 30 years. Atmos. Environ. 39, 5423–5435]. The Beltsville record also demonstrated the value of soundings for air quality forecasting in an urban area. The 22 nighttime soundings collected over Beltsville in 2004–2007 can be divided into distinct polluted and unpolluted subsets, the former 20 ppbv higher in residual layer ozone (1 km) than the latter. These distinctions propagated to daytime differences of 10 ppbv at the surface in the Washington, DC, area, with the high-ozone residual layers leading to non-attainment of the National Ambient Air Quality Standard for ozone. More frequent ozone observations aloft appear essential for better understanding ozone variability and for enabling air quality modelers to achieve more accurate ozone forecasts.     

Ultrafine particles near a major roadway in Raleigh,North Carolina: Downwind attenuation and correlation with traffic-related pollutants

Ultrafine particles (UFPs, diameter < 100 nm) and co-emitted pollutants from traffic are a potential health threat to nearby populations. During summertime in Raleigh, North Carolina, UFPs were simultaneously measured upwind and downwind of a major roadway using a spatial matrix of five portable industrial hygiene samplers (measuring total counts of 20–1000 nm particles). While the upper sampling range of the portable samplers extends past the defined “ultrafine” upper limit (100 nm), the 20–1000 nm number counts had high correlation (Pearson R = 0.7–0.9) with UFPs (10–70 nm) measured by a co-located research-grade analyzer and thus appear to be driven by the ultrafine range. Highest UFP concentrations were observed during weekday morning work commutes, with levels at 20 m downwind from the road nearly fivefold higher than at an upwind station. A strong downwind spatial gradient was observed, linearly approximated over the first 100 m as an 8% drop in UFP counts per 10 m distance. This result agreed well with UFP spatial gradients estimated from past studies (ranging 5–12% drop per 10 m). Linear regression of other vehicle-related air pollutants measured in near real-time (10-min averages) against UFPs yielded moderate to high correlation with benzene (R² = 0.76), toluene (R² = 0.49), carbon monoxide (R² = 0.74), nitric oxide (R² = 0.80), and black carbon (R² = 0.65). Overall, these results support the notion that near-road levels of UFPs are heavily influenced by traffic emissions and correlate with other vehicle-produced pollutants, including certain air toxics.     

The potential of public engagement in sustainable waste management: designing the future for biosolids in New Zealand

Strategies for beneficial use of biosolids in New Zealand and elsewhere are currently focused primarily on land application. The long-term success of these and other strategies is dependent not only on technical factors, but also on their environmental, economic, social and cultural sustainability. This paper briefly reviews the situation with respect to biosolids management in New Zealand, where land application is not yet widespread; the rise in public opposition to land application in the United States; and the biosolids industry's approach to public engagement. We argue that, at least until recently, the industry has misinterpreted the nature and meaning of public opposition and thus substituted public relations for public engagement. We argue that genuine public engagement is necessary and that its purpose cannot be to gain public acceptance for an already-decided-upon strategy. It therefore calls for humility among biosolids managers, including a willingness to open up the framing of 'the problem', to acknowledge areas of uncertainty, and to recognise the role of values in 'technical' decision-making. We then present and analyse an example of the use of the scenario workshop process for public participation in biosolids management policy in Christchurch, New Zealand, and conclude that scenario workshops and related methods represent an opportunity to enhance sustainable waste management when certain conditions are met.     

Public support for river restoration. A mixed-method study into local residents' support for and framing of river management and ecological restoration in the Dutch floodplains

In many European countries, accommodating water has become the dominant paradigm in river management. In the Netherlands, extensive river restoration projects are being implemented, many of which draw serious opposition from the public. To investigate the causes of such opposition, a comprehensive study of public attitudes towards river restoration was conducted in three floodplains, both before and after river restoration. The study combined quantitative questionnaires (N = 562) with open interviews (N = 29). This paper describes how local residents perceive the effects of river restoration on landscape quality and how residents and protest groups use landscape quality in combination with other arguments to strategically frame river management policies. Results show that measurement of the perceived outcomes of nature restoration needs to be complemented by a more dynamic type of research, focusing on the social processes of the framing of restoration plans. Theoretically, the paper aims to contribute to the development of a rigorous research strategy to study framing processes in environmental management, using a mixed-methods approach.     

An Approach for Evaluating the Repeatability of Rapid Wetland Assessment Methods: The Effects of Training and Experience

We sampled 92 wetlands from four different basins in the United States to quantify observer repeatability in rapid wetland condition assessment using the Delaware Rapid Assessment Protocol (DERAP). In the Inland Bays basin of Delaware, 58 wetland sites were sampled by multiple observers with varying levels of experience (novice to expert) following a thorough training workshop. In the Nanticoke (Delaware/Maryland), Cuyahoga (Ohio), and John Day (Oregon) basins, 34 wetlands were sampled by two expert teams of observers with minimal protocol training. The variance in observer to observer scoring at each site was used to calculate pooled standard deviations (SD_pool), coefficients of variation, and signal-to-noise ratios for each survey. The results showed that the experience level of the observer had little impact on the repeatability of the final rapid assessment score. Training, however, had a large impact on observer to observer repeatability. The SD_pool in the Inland Bay survey with training (2.2 points out of a 0–30 score) was about half that observed in the other three basins where observers had minimal training (SD_pool = 4.2 points). Using the results from the survey with training, we would expect that two sites assessed by different, trained observers who obtain DERAP scores differing by more than 4 points are highly likely to differ in ecological condition, and that sites with scores that differ by 2 or fewer points are within variability that can be attributed to observer differences.