Recommended metric for tracking visibility progress in the Regional Haze Rule

For many national parks and wilderness areas with special air quality protections (Class I areas) in the western United States (U.S.), wildfire smoke and dust events can have a large impact on visibility. The U.S. Environmental Protection Agency’s (EPA) 1999 Regional Haze Rule used the 20% haziest days to track visibility changes over time even if they are dominated by smoke or dust. Visibility on the 20% haziest days has remained constant or degraded over the last 16 yr at some Class I areas despite widespread emission reductions from anthropogenic sources. To better track visibility changes specifically associated with anthropogenic pollution sources rather than natural sources, the EPA has revised the Regional Haze Rule to track visibility on the 20% most anthropogenically impaired (hereafter, most impaired) days rather than the haziest days. To support the implementation of this revised requirement, the EPA has proposed (but not finalized) a recommended metric for characterizing the anthropogenic and natural portions of the daily extinction budget at each site. This metric selects the 20% most impaired days based on these portions using a “delta deciview” approach to quantify the deciview scale impact of anthropogenic light extinction. Using this metric, sulfate and nitrate make up the majority of the anthropogenic extinction in 2015 on these days, with natural extinction largely made up of organic carbon mass in the eastern U.S. and a combination of organic carbon mass, dust components, and sea salt in the western U.S. For sites in the western U.S., the seasonality of days selected as the 20% most impaired is different than the seasonality of the 20% haziest days, with many more winter and spring days selected. Applying this new metric to the 2000–2015 period across sites representing Class I areas results in substantial changes in the calculated visibility trend for the northern Rockies and southwest U.S., but little change for the eastern U.S.

Implications: Changing the approach for tracking visibility in the Regional Haze Rule allows the EPA, states, and the public to track visibility on days when reductions in anthropogenic emissions have the greatest potential to improve the view. The calculations involved with the recommended metric can be incorporated into the routine IMPROVE (Interagency Monitoring of Protected Visual Environments) data processing, enabling rapid analysis of current and future visibility trends. Natural visibility conditions are important in the calculations for the recommended metric, necessitating the need for additional analysis and potential refinement of their values.     

Feasibility of coupling a thermal/optical carbon analyzer to a quadrupole mass spectrometer for enhanced PM2.5 speciation

A thermal/optical carbon analyzer (TOA), normally used for quantification of organic carbon (OC) and elemental carbon (EC) in PM_2.5 (fine particulate matter) speciation networks, was adapted to direct thermally evolved gases to an electron impact quadrupole mass spectrometer (QMS), creating a TOA-QMS. This approach produces spectra similar to those obtained by the Aerodyne aerosol mass spectrometer (AMS), but the ratios of the mass to charge (m/z) signals differ and must be remeasured using laboratory-generated standards. Linear relationships are found between TOA-QMS signals and ammonium (NH₄⁺), nitrate (NO₃^?), and sulfate (SO₄^2-) standards. For ambient samples, however, positive deviations are found for SO₄^2-, compensated by negative deviations for NO₃^?, at higher concentrations. This indicates the utility of mixed-compound standards for calibration or separate calibration curves for low and high ion concentrations. The sum of the QMS signals across all m/z after removal of the NH₄⁺, NO₃^?, and SO₄^2- signals was highly correlated with the carbon content of oxalic acid (C?H?O?) standards. For ambient samples, the OC derived from the TOA-QMS method was the same as the OC derived from the standard IMPROVE_A TOA method. This method has the potential to reduce complexity and costs for speciation networks, especially for highly polluted urban areas such as those in Asia and Africa.

Implications: Ammonium, nitrate, and sulfate can be quantified by the same thermal evolution analysis applied to organic and elemental carbon. This holds the potential to replace multiple parallel filter samples and separate laboratory analyses with a single filter and a single analysis to account for a large portion of the PM_2.5 mass concentration.     

Silver near municipal wastewater discharges into western Lake Ontario,Canada

Because of the widespread use of silver nanoparticles in commercial products, discharges of municipal wastewater may be a point source of silver in the aquatic environment. We monitored two sites in western Lake Ontario impacted by discharges from wastewater treatment plants serving the City of Toronto. Concentrations of silver were elevated in bottom sediments and suspended sediments collected at the two sites. We also deployed two types of passive samplers in the water column at the two sites, the newly developed Carbon Nanotube Integrative Samplers for monitoring “CNIS-labile” silver and Diffusive Gradient in Thin Film samplers for monitoring “DGT-labile” silver. Results from these passive samplers indicated that the concentrations of silver at the two sites were either below detection limits or were in the ng/L range. In laboratory experiments where the sediments were re-suspended in Milli-Q water, a small proportion of the silver (i.e., <?25%) was labile and partitioned as colloidal or dissolved silver into the liquid phase after agitation. Nanoparticles tentatively identified as silver nanoparticles were detected by single-particle ICP-MS in suspension after agitation of both suspended and bottom sediments. Therefore, there is a need to assess whether silver species, including silver nanoparticles are transported from wastewater treatment plants into sediments in the aquatic environment. This study is unique in focusing on the in situ distribution of silver in natural waters and in sediments that are potentially impacted by urban sources of nanoparticles.     

Assessment using CFD of the wind direction on the air discharges caused by natural ventilation of a poultry house

Air inside poultry houses must be removed on a regular basis to prevent excess of heat, particles and noxious gases that can imperil animals. To cope with this issue, natural ventilation could be an effective method when assisted by accurate predictions. This study investigates air discharges caused by natural ventilation of a poultry house by means of a three-dimensional computational fluid dynamics (CFD) model. It solves the governing equations of momentum, heat and mass transport, radiative transfers and animal-generated heat. Wind directions of 0°, 36° and 56° (0° corresponds to a wind blowing perpendicular to the ridgeline) were investigated; the CFD model predictions achieved a RMSE of 1.2 °C and 0.6 g[H₂O] kg^?1 [dry air] for internal temperature and absolute humidity, respectively, when air blew with an angle of 36°. Air renewal rates (ARR) were 39.5 (±?1.9), 34.9 (±?2.2) and 33.6 (±?1.7) volumes of the building per hour, when air blew at 0°, 36° and 56°, respectively. Such ARR predictions served to know how the gases contained in air would likely spread downstream from the building in order to define regions of potentially high gas concentration that could endanger neighbouring habitable facilities.     

The choice of system boundaries for effective long-term management of phosphorus

Journal of Material Cycles and Waste Management - Material flow analysis (MFA) is a well-established tool for supporting decisions on nutrient management. This paper shows the importance of the...     

Emergency department visits by pediatric patients sustained as a passenger on a motorcycle

Objective: Currently only 5 out of the 50 states in the United States have laws restricting the age of passengers permitted to ride on a motorcycle. This study sought to characterize the visits by patients under the age of 16 to U.S. emergency departments (EDs) for injuries sustained as a passenger on a motorcycle.

Methods: In this retrospective cohort study, data were obtained from the Nationwide Emergency Department Sample (NEDS) for the years 2006 to 2011. Pediatric patients who were passengers on a motorcycle that was involved in a crash were identified using International Classification of Diseases, Ninth Revision (ICD-9) External Cause of Injury codes. We also examined gender, age, disposition, regional differences, common injuries, and charges.

Results: Between 2006 and 2011 there were an estimated 9,689 visits to U.S. EDs by patients under the age of 16 who were passengers on a motorcycle involved in a crash. The overall average patient age was 9.4 years, and they were predominately male (54.5%). The majority (85%) of these patients were treated and released. The average charges for discharged patients were $2,116.50 and amounted to roughly $17,500,000 during the 6 years. The average cost for admission was $51,446 per patient and totaled over $54 million. The most common primary injuries included superficial contusions; sprains and strains; upper limb fractures; open wounds of head, neck, and trunk; and intracranial injuries.

Conclusion: Although there were only about 9,700 visits to U.S. EDs for motorcycle crashes involving passengers less than 16 years old for 2006 to 2011, the total cost of visits that resulted in either ED discharge or hospital admission amounted to over $71 million.     

Towards an international standard: The ISO/DIS 18504 standard on sustainable remediation

Sustainable remediation is the elimination and/or control of unacceptable risks in a safe and timely manner while optimizing the environmental, social, and economic value of the work. Forthcoming International Organization for Standardization (ISO) Standard on Sustainable Remediation will allow countries without the capacity to develop their own guidance to benefit from work done over the past decade by various groups around the world. The ISO standard has progressed through the committee draft (ISO/CD 18504) and draft international standard (ISO/DIS 18504) stages. The risk‐based approach to managing the legacy of historically contaminated soil and groundwater has been incorporated into policy, legislation, and practice around the world. It helps determine the need for remediation and the end point of such remediation. Remediation begins with an options appraisal that short lists strategies that could deliver the required reduction in risk. A remediation strategy comprises one or more remediation technologies that will deliver the safe and timely elimination and/or control of unacceptable risks. The ISO standard will help assessors identify the most sustainable among the shortlisted, valid alternative remediation strategies. Practitioners presenting case studies claiming to constitute sustainable remediation should now report how they have aligned their work with the new standard. Indicators are used to compare alternative remediation strategies. The simplest metric that allows a characteristic to act as an indicator should be chosen. Weightings indicators can become a contested exercise and should only be undertaken where there is a clear desire for it by stakeholders and a clear need for it in identifying a preferred strategy. The simplest means of ranking alternative remediation strategies should be adopted.     

Travis Air Force Base: A greener cleanups case study

Travis Air Force Base, California, has accelerated the pace of remediation while reducing long‐term costs and cutting greenhouse gas production. This has been achieved through optimizing existing systems and processes, adopting greener cleanups best management practices, and testing and implementing innovative “green” technologies. By optimizing and replacing existing systems that used energy‐intensive infrastructure, and by promoting the use of innovative in situ technologies, the US Air Force (Air Force) led team comprised of the Air Force Civil Engineer Center, the US Army Corps of Engineers, the performance‐based contractor CH2M, and the regulatory agencies consisting of the US Environmental Protection Agency, the California Water Board, and the California Department of Toxic Substances Control, has reduced annual system operation and maintenance costs by over $200,000 per year, while reducing annual carbon dioxide production by approximately 930 tons per year. As a result of these actions, chlorinated solvent source areas have been reduced by over 99 percent in some cases, and the predicted cleanup time frame for multiple sites has been reduced by several decades. This article provides a case study for implementation of cost‐effective greener cleanup actions, and summarizes the approach taken by the Air Force led team to complete the greener cleanups self‐declaration process consistent with the ASTM International's E‐2893 Standard Guide for Greener Cleanups.     

美国和五大湖双边共同关注区域的白肚燕(双色树燕)雏鸟的有机污染状况

白肚燕,又名双色树燕,栖居于五大湖流域中27个双边共同关注区域(AOCs),从2010年到2014年对其进行了污染物暴露风险评估,以协助管理者和监管者评估五大湖AOCs的污染状况。本文比较了AOCs和附近非AOCs雏鸟体内污染物浓度的差异。AOCs白肚燕雏鸟尸体中多氯联苯(PCB)和多溴联苯醚的含量分别为30%和33%,低于非AOCs的平均浓度。AOCs白肚燕雏鸟胃含物中多环芳烃(PAH)浓度和血浆中全氟化合物浓度分别为67%和64%,也低于非AOCs的平均浓度。但是与已有生殖效应记载的高PCB污染区相比,有些AOCs雏鸟尸体内的PCBs浓度只是存在小幅升高。一些AOCs食物中PAHs的浓度足够高以致引起可测量的生理响应。在AOCs中,全氟化合物全氟辛烷磺酸在血浆中的最高浓度出现在Raisin河(密歇根州,美国;几何平均数330 ng/mL),但远低于预估毒性的参考值(1 700 ng/mL)。之前有研究报道雏鸟胃含物中PAH和PCB的浓度以及尸体中PCBs的含量与沉积物中污染物的含量显著相关,从而可加强白肚燕在评估沉积物污染生物有效性方面的应用。
精选自Thomas W. Custer, Christine M. Custer, Paul M. Dummer, Diana Goldberg, J. Christian Franson, Richard A. Erickson. Organic contamination in tree swallow (Tachycineta bicolor) nestlings at United States and binational Great Lakes areas of concern. Environmental Toxicology and Chemistry: Volume 36, Issue 3, pages 735–748, July 2017. DOI: 10.1002/etc.3598
详情请见http://onlinelibrary.wiley.com/wol1/doi/10.1002/etc.3598/full
     

Interaction webs in arctic ecosystems: Determinants of arctic change?

How species interact modulate their dynamics, their response to environmental change, and ultimately the functioning and stability of entire communities. Work conducted at Zackenberg, Northeast Greenland, has changed our view on how networks of arctic biotic interactions are structured, how they vary in time, and how they are changing with current environmental change: firstly, the high arctic interaction webs are much more complex than previously envisaged, and with a structure mainly dictated by its arthropod component. Secondly, the dynamics of species within these webs reflect changes in environmental conditions. Thirdly, biotic interactions within a trophic level may affect other trophic levels, in some cases ultimately affecting land–atmosphere feedbacks. Finally, differential responses to environmental change may decouple interacting species. These insights form Zackenberg emphasize that the combination of long-term, ecosystem-based monitoring, and targeted research projects offers the most fruitful basis for understanding and predicting the future of arctic ecosystems.