Laboratory and Field Evaluation of Measurement Methods for One-Hour Exposures to O3, PM25, and CO

ABSTRACT

While researchers have linked acute (less than 12-hr) ambient O₃, PM₂₅, and CO concentrations to a variety of adverse health effects, few studies have characterized short-term exposures to these air pollutants, in part due to the lack of sensitive, accurate, and precise sampling technologies. In this paper, we present results from the laboratory and field evaluation of several new (or modified) samplers used in the “roll-around” system (RAS), which was developed to measure 1-hr O₃, PM₂₅, and CO exposures simultaneously. All the field evaluation data were collected during two sampling seasons: the summer of 1998 and the winter of 1999.

To measure 1-hr O₃ exposures, a new active O₃ sampler was developed that uses two nitrite-coated filters to measure O₃ concentrations. Laboratory chamber tests found that the active O₃ sampler performed extremely well, with a collection efficiency of 0.96 that did not vary with temperature or relative humidity (RH). In field collocation comparisons with a reference UV photometric monitor, the active O₃ sampler had an effective collection efficiency ranging between 0.92 and 0.96 and a precision for 1-hr measurements ranging between 4 and 6 parts per billion (ppb). The limits of detection (LOD) of this method were 9 ppb-hr for the chamber tests and ~16 ppb-hr for the field comparison tests.

PM_2.5 and CO concentrations were measured using modified continuous monitors—the DustTrak and the Langan, respectively. A size-selective inlet and a Nafion dryer were placed upstream of the DustTrak inlet to remove particles with aerodynamic diameters greater than 2.5 um and to dry particles prior to the measurements, respectively. During the field validation tests, the DustTrak consistently reported higher PM_2.5 concentrations than those obtained by the collocated 12-hr PM_{2 5} PEM samples, by approximately a factor of 2. After the DustTrak response was corrected (correction factor of 2.07 in the summer and 2.02 in the winter), measurements obtained using these methods agreed well with R² values of 0.87 in the summer and 0.81 in the winter. The results showed that the DustTrak can be used along with integrated measurements to measure the temporal and spatial variation in PM_{2 5} exposures. Finally, during the field validation tests, CO concentrations measured using the Langan were strongly correlated with those obtained using the reference method when the CO levels were above the LOD of the instrument [~1 part per million (ppm)].     

Weekday/Weekend Ozone Differences: What Can We Learn from Them?

Abstract

A national analysis of weekday/weekend ozone (O₃) differences demonstrates significant variation across the country. Weekend 1-hr or 8-hr maximum O₃ varies from 15% lower than weekday levels to 30% higher. The weekend O₃ increases are primarily found in and around large coastal cities in California and large cities in the Midwest and Northeast Corridor. Both the average and the 95th percentile of the daily 1-hr and 8-hr maxima exhibit the same general pattern. Many sites that have elevated O₃ also have higher O₃ on weekends even though traffic and O₃ precursor levels are substantially reduced on weekends. Detailed studies of this phenomenon indicate that the primary cause of the higher O₃ on weekends is the reduction in oxides of nitrogen (NO_x) emissions on weekends in a volatile organic compound (VOC)-limited chemical regime. In contrast, the lower O₃ on weekends in other locations is probably a result of NO_x reductions in a NO_x-limited regime. The NO_x reduction explanation is supported by a wide range of ambient analyses and several photochemical modeling studies. Changes in the timing and location of emissions and meteorological factors play smaller roles in weekend O₃ behavior. Weekday/weekend temperature differences do not explain the weekend effect but may modify it.     

Development of Emission Factors for Polycarbonate Processing

Abstract

Emission factors for selected volatile organic compounds (VOCs) and particulate emissions were developed while processing eight commercial grades of polycarbonate (PC) and one grade of a PC/acrylonitrile-butadiene-styrene (ABS) blend. A small commercial-type extruder was used, and the extrusion temperature was held constant at 304 °C. An emission factor was calculated for each substance measured and is reported as pounds released to the atmosphere/million pounds of polymer resin processed [ppm (wt/wt)]. Scaled to production volumes, these emission factors can be used by processors to estimate emission quantities from similar PC processing operations.     

Terrestrial exposure of oilfield flowline additives diminish soil structural stability and remediative microbial function

Onshore oil production pipelines are major installations in the petroleum industry, stretching many thousands of kilometres worldwide which also contain flowline additives. The current study focuses on the effect of the flowline additives on soil physico-chemical and biological properties and quantified the impact using resilience and resistance indices. Our findings are the first to highlight deleterious effect of flowline additives by altering some fundamental soil properties, including a complete loss of structural integrity of the impacted soil and a reduced capacity to degrade hydrocarbons mainly due to: (i) phosphonate salts (in scale inhibitor) prevented accumulation of scale in pipelines but also disrupted soil physical structure; (ii) glutaraldehyde (in biocides) which repressed microbial activity in the pipeline and reduced hydrocarbon degradation in soil upon environmental exposure; (iii) the combinatory effects of these two chemicals synergistically caused severe soil structural collapse and disruption of microbial degradation of petroleum hydrocarbons.     

Larvicidal and pupicidal activities of eco-friendly phenolic lipid products from Anacardium occidentale nutshell against arbovirus vectors

Environmental Science and Pollution Research - Aedes aegypti and Culex quinquefasciatus are vectors of diseases that constitute public health problems. The discovery of products capable of...     

Changes in Streambed Composition in Salmonid Spawning Habitat of the Elwha River during Dam Removal

One uncertainty associated with large dam removal is the level of downstream sediment deposition and associated short‐term biological effects, particularly on salmonid spawning habitat. Recent studies report downstream sediment deposition following dam removal is influenced by proximity to the source and river transport capacity. The impacts of dam removal sediment releases are difficult to generalize due to the relatively small number of dam removals completed, the variation in release strategies, and the physical nature of systems. Changes to sediment deposition and associated streambed composition in the Elwha River, Washington State, were monitored prior to (2010‐2011) and during (2012‐2014) the simultaneous removal of two large dams (32 and 64 m). Changes in the surface layer substrate composition during dam removal varied by year and channel type. Riffles in floodplain channels downstream of the dams fined and remained sand dominated throughout the study period, and exceeded levels known to be detrimental to incubating salmonids. Mainstem riffles tended to fine to gravel, but appear to be trending toward cobble after the majority of the sediment was released and transported through system. Thus, salmonid spawning habitats in the mainstem appear to have been minimally impacted while those in floodplain channels appear to have been severely impacted during dam removal.     

Effects of diesel/biodiesel blends on regulated and unregulated pollutants from a passenger vehicle operated over the European and the Athens driving cycles

This paper presents the regulated and unregulated exhaust emissions of a diesel passenger vehicle, operated with low sulphur automotive diesel and soy methyl ester blends. Emission and fuel consumption measurements were conducted under real driving conditions (Athens Driving Cycle, ADC) and compared with those of a modified New European Driving Cycle (NEDC) using a chassis dynamometer. A Euro II compliant diesel vehicle was used in this study, equipped with an indirect injection diesel engine, fuelled with diesel fuel and biodiesel blends at proportions of 5, 10, and 20% respectively. Unregulated emissions of 11 polycyclic aromatic hydrocarbons (PAHs), 5 nitro-PAHs, 13 carbonyl compounds (CBCs) and the soluble organic fraction (SOF) of the particulate matter were measured. Qualitative hydrocarbon analysis was also performed on the SOF. Regulated emissions of NO_x, CO, HC, CO₂, and PM were also measured over the two test cycles. It was established that some of the emissions measured over the (hot-start) NEDC differed from the real-world cycle. Significant differences were also observed in the vehicle's fuel consumption between the two test cycles. The addition of biodiesel reduced the regulated emissions of CO, HC and PM, while an increase in NO_x was observed over the ADC. Carbonyl emissions, PAHs and nitro-PAHs were reduced with the addition of biodiesel over both driving cycles.     

Ultraviolet absorbance as a proxy for total dissolved mercury in streams

Stream water samples were collected over a range of hydrologic and seasonal conditions at three forested watersheds in the northeastern USA. Samples were analyzed for dissolved total mercury (THg_d), DOC concentration and DOC composition, and UV₂₅₄ absorbance across the three sites over different seasons and flow conditions. Pooling data from all sites, we found a strong positive correlation of THg_d to DOC (r² = 0.87), but progressively stronger correlations of THg_d with the hydrophobic acid fraction (HPOA) of DOC (r² = 0.91) and with UV₂₅₄ absorbance (r² = 0.92). The strength of the UV₂₅₄ absorbance-THg_d relationship suggests that optical properties associated with dissolved organic matter may be excellent proxies for THg_d concentration in these streams. Ease of sample collection and analysis, the potential application of in-situ optical sensors, and the possibility for intensive monitoring over the hydrograph make this an effective, inexpensive approach to estimate THg_d flux in drainage waters.     

Effectiveness of a publicly-funded demonstration program to promote management of dryland salinity

Community and catchment-based approaches to salinity management continue to attract interest in Australia. In one such approach, Catchment Demonstration Initiative (CDI) projects were established by the Western Australian (WA) Government in 2000 for targeted investment in large-scale catchment-based demonstrations of integrated salinity management practices. The aim was to promote a process for technically-informed salinity management by landholders. This paper offers an evaluation of the effectiveness of one CDI project in the central wheatbelt of WA, covering issues including: its role in fostering adoption of salinity management options, the role of research and the technical requirements for design and implementation of on-ground works, the role of monitoring and evaluation, the identification and measurement of public and private benefits, comparison and identification of the place and value of plant-based and engineering-based options, reliance on social processes and impacts of constraints on capacity, management of governance and administration requirements and an appreciation of the value of group-based approaches.A number of factors may reduce the effectiveness of CDI-type approaches in facilitating landholder action to address salinity, many of these are socially-based. Such approaches can create considerable demands on landholders, can be expensive (because of the planning and accountability required) on the basis of dollars per hectare impacted, and can be difficult to garner ownership from all involved. An additional problem could be that few community groups would have the capacity to run such programs and disseminate the new knowledge so that the CDI-type projects can impact outside the focus catchment. In common with many publicly-funded approaches to salinity, we found that direct benefits on public assets are smaller than planned and that results from science-based requirements of monitoring and evaluation have long lead times, causing farmers to either wait for the information or act sooner and take risks based on initial results. We also found that often it is a clear outline of the process that is of most importance in decision making as opposed to the actual results. We identified limitations in regulatory processes and the capacity for local government to engage in the CDI.The opportunities that CDI-type approaches provide centre around the value of its group-based approach. We conclude that they can overcome knowledge constraints in managing salinity by fostering group-based learning, offer a structured process of trialling options so that the costs and benefits can be clearly and transparently quantified, and avoid the costly mistakes and “learning failures” of the past.     

The role of satellite and decentralized strategies in water resources management

Existing and projected water shortages and related factors have helped focus attention on the need for water reuse. With recent technological advances in wastewater treatment, it is now possible to produce reclaimed water of any quality. Thus, the use of reclaimed water will depend on the reuse opportunities and the cost of the required infrastructure. Historically, centralized wastewater treatment facilities have served the needs of organized societies since the mid 1800s. However, as there are limited options for expansion of most existing centralized facilities, the use of satellite and decentralized wastewater management systems offers significant advantages including being close both to the source of wastewater generation and to potential water reuse applications. The comparative advantages of satellite and decentralized wastewater management systems for a number of water reuse applications are presented and discussed in this paper. Selected case studies are presented to demonstrate the utility of satellite and decentralized wastewater management. Specific issues associated with the application of such systems in existing and in new developments are examined and discussed.