On the use of expert judgment to characterize uncertainties in the health benefits of regulatory controls of particulate matter

Health benefits assessment is an analytic tool used extensively by the U.S. Environmental Protection Agency (EPA) in characterizing the costs and benefits of air quality regulations. In a 2002 review of EPA methods, the U.S. National Research Council (NRC) called on EPA to more fully account for and communicate uncertainties in estimates of the health benefits of air pollution regulations. In particular, the NRC recommended that EPA use expert judgment to quantify uncertainties in cases where empirical estimates are lacking. In response, EPA developed and carried out an expert elicitation (EE) study to quantify uncertainties in the effects of fine particulate matter (PM_2.5) on mortality in the U.S. This work has yielded new estimates of the uncertainty distribution of a key relationship – the concentration–response (C–R) function – used around the world in benefits analyses for air quality regulations. This paper discusses the ways in which the EE results have informed and influenced recent regulatory impact analyses (RIAs) carried out by EPA to characterize and communicate the health benefits of regulations affecting ambient PM_2.5 concentrations. Given the growing importance of PM benefits analysis across the globe, recent developments pioneered by EPA could have widespread relevance.     

Explaining the fragmentation in the Brazilian Amazonian forest

Although vast literature exists on the drivers of tropical deforestation and its ecological consequences, less is known about how patterns of forest fragmentation emerge in the first place. The purpose of this paper is to address this issue for the Brazilian portion of the Amazon basin by analyzing the social processes generative of five specific patterns, including rectangular, fishbone, radial, dendritic, and what we refer to as ‘the stem of the rose.’ We argue that forest fragmentation patterns in the Brazilian Amazon are largely determined by the types and arrival times of the agents who engage in land clearing. We also argue that the patterns manifest in the landscape by virtue of road construction and agricultural property formation, which often occur in tandem. We conclude by placing our discussion within legal and institutional contexts, and observe that fragmentation stemming from formal colonization projects is more consistent with biodiversity conservation than that associated with a laissez-faire occupation. However, erosive impacts may be greater in topographically sensitive areas.     

A pioneer validation of a state-space model of vessel trajectories (VMS) with observers’ data

In the context of the expansion of animal tracking and bio-logging, state-space models have been developed with the objective to characterise animals’ trajectories and to understand the factors controlling their behaviour. In the fisheries community, the electronic tagging of vessels commonly designated by Vessel Monitoring Systems (VMS) is developing and provides a new insight for the understanding, the analysis and the modelling of the trajectories of vessels and their prospecting behaviour. VMS data are thus a clue for the proper definition of fishing effort which remains a fundamental parameter of tuna stock assessments. In this context, we used the VMS (recording of hourly positions) of the French tropical tuna purse-seiners operating in the Indian Ocean to characterise three types of movement (states) on the VMS trajectories (stillness, tracking, and cruising). Based on empirical evidences, and on the regular frequency of VMS acquisition, this was achieved by the development of a Bayesian Hidden Markov model for the speeds and turning angles derived from the hourly steps of the trajectories. In a second phase, states were related to activities disentangling stillness into fishing or stop at sea. Finally the quality of the model performances was rigorously quantified thanks to observers’ data. Confronting model prediction and true activities allowed estimating that 10% of the hourly steps were misclassified. The assumptions and model’ choices are discussed, highlighting the fact that VMS data and observers’ data having different time resolutions, the effective use of validating data was troublesome. However, without validation, these analyses remain speculative. The validation part of this work represents an important step for the operational use of state-space models in ecology in the broad sense (predators’ tracking data, e.g. birds or mammals trajectories).     

Clearing the smog? Public responses to air-quality information

Recent perspectives on public responses to environmental and risk communication have emphasised the interpretation, judgement and 'sense-making' that takes place when lay audiences receive information and advice. In this paper we consider the public reception given to air-quality information in the UK as one example of a government information and communication initiative. Drawing on elements of a wider research project undertaken in the city of Birmingham in the UK, involving a survey and in-depth interviews with members of the public, it examines the extent of awareness and use of information services, attitudes towards information and the role of information in behaviour change. The objective of the paper is to assess in practical terms the impact of air-quality information available through the media and other sources, as well as to provide empirical evidence with which to reflect on debates over the practice of environmental communication and the stimulation of pro-environmental behaviour. Conclusions are drawn which point to both problems with air quality information provision and the possibilities of more effective and appropriate interventions through local-level initiatives.     

Modelling treated waste disposal in Port Phillip Bay and Bass Strait biogeochemical and physical removal.

Large cities, such as Melbourne, generate substantial quantities of sewage, which, after treatment, must be disposed. Melbourne's sewage is disposed via two routes, that treated at the Western Treatment Plant (WTP) is discharged in enclosed Port Phillip Bay, while the Boags Rock outfall empties into the exposed Bass Strait. In Port Phillip Bay biogeochemical processes control the fate of waste, while in the Bass Strait physical mixing rapidly disperses the waste. These different processes require very different ecosystem models. Port Phillip Bay requires detailed modelling of water-column and in-sediment processes, in particular detailed models of recycling processes, and also modelling of benthos-water-column interactions. Interaction of these components gives the model a nonlinear response to change in load. The Bass Strait ecosystem model is simple with no modelling of the sediment and limited modelling of water-column recycling. This model's behaviour is largely controlled by the physical environment.     

EVALUATION OF SELECTED PESTICIDES IN NORTH CAROLINA SURFACE WATER SUPPLIES: INTAKE STUDY1

ABSTRACT: Studies were conducted to analyze the presence of 11 selected pesticides in 12 surface water supply intakes in the Piedmont and coastal plain regions of North Carolina. Samples were assayed using enzyme linked immunosorbent assays (ELISAs). Samples with pesticide detection of 1 μg/L or greater were extracted and confirmed using gas chromatography/mass spectrometry (GC/MS). Detection limits of the immunosorbent assays for pesticide residues were generally an order of magnitude higher than GC/MS. Atrazine was detected in approximately 45 percent of the samples, and on two occasions was at or above the lifetime Maximum Contaminant Level of 3.0 μg/L set by the Environmental Protection Agency for an annual average in finished drinking water. Metolachlor was detected in 58 percent of the samples. Of the remaining nine pesticides, including carbaryl, aldicarb, 2,4‐D, chiorpyrifos, acetochlor, methomyl, carbofuran, alachlor, and chlorothalonil, only aldicarb, 2,4‐D, and chlorpyrifos were detected in less than 9 percent of the samples for each pesticide.     

Estimating PAH sources in harbor sediments using diagnostic ratios

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the global environment and are subsequently transported into aquatic sediments. As PAHs are formed by various processes, source identification using diagnostic ratios can provide insight to PAH emission sources to distinguish between pyrogenic and petrogenic PAH sources. PAH diagnostic ratios were applied as a forensic source apportionment technique to assess aggregate historical sediment data from 31 small craft harbors (SCHs) across Nova Scotia, Canada. Multiple diagnostic ratios suggest that PAHs present in Nova Scotia SCH sediments are pyrogenic (combustion) in origin, while consistently suggesting that coal‐related PAH sources are potential dominant specific sources. National Institute of Standards and Technology Standard Reference Materials (SRMs) were used as reference for coal tar, urban dust, and diesel exhaust particulates in ratio applications. The SRM for coal tar was most similar to Nova Scotia SCH sediments in multiple ratio applications. Diagnostic ratio results were corroborated by comparing the PAH profile of sediments to source profiles from the literature. Results indicate that Nova Scotia SCH sediments follow global trends by exhibiting a dominant pyrogenic PAH signature, and the specific coal‐related PAH signature of Nova Scotia SCH sediments may be influenced by contamination inputs related to historical industrial coal mining and combustion activities in the province.     

Long‐Term Trends in Streamflow and Precipitation in Northwest California and Southwest Oregon, 1953‐2012

Using nonparametric Mann‐Kendall tests, we assessed long‐term (1953‐2012) trends in streamflow and precipitation in Northern California and Southern Oregon at 26 sites regulated by dams and 41 “unregulated” sites. Few (9%) sites had significant decreasing trends in annual precipitation, but September precipitation declined at 70% of sites. Site characteristics such as runoff type (groundwater, snow, or rain) and dam regulation influenced streamflow trends. Decreasing streamflow trends outnumbered increasing trends for most months except at regulated sites for May‐September. Summer (July‐September) streamflow declined at many sites, including 73% of unregulated sites in September. Applying a LOESS regression model of antecedent precipitation vs. average monthly streamflow, we evaluated the underlying streamflow trend caused by factors other than precipitation. Decreasing trends in precipitation‐adjusted streamflow substantially outnumbered increasing trends for most months. As with streamflow, groundwater‐dominated sites had a greater percent of declining trends in precipitation‐adjusted streamflow than other runoff types. The most pristine surface‐runoff‐dominated watersheds within the study area showed no decreases in precipitation‐adjusted streamflow during the summer months. These results suggest that streamflow decreases at other sites were likely due to more increased human withdrawals and vegetation changes than to climate factors other than precipitation quantity.     

Nitrogen Subsidies from Hillslope Alder Stands to Streamside Wetlands and Headwater Streams,Kenai Peninsula,Alaska

We examined nitrogen transport and wetland primary production along hydrologic flow paths that link nitrogen‐fixing alder (Alnus spp.) stands to downslope wetlands and streams in the Kenai Lowlands, Alaska. We expected that nitrate concentrations in surface water and groundwater would be higher on flow paths below alder. We further expected that nitrate concentrations would be higher in surface water and groundwater at the base of short flow paths with alder and that streamside wetlands at the base of alder‐near flow paths would be less nitrogen limited than wetlands at the base of long flow paths with alder. Our results showed that groundwater nitrate‐N concentrations were significantly higher at alder‐near sites than at no‐alder sites, but did not differ significantly between alder‐far sites and no‐alder sites or between alder‐far sites and alder‐near sites. A survey of ¹⁵N stable isotope signatures in soils and foliage in alder‐near and no‐alder flow paths indicated the alder‐derived nitrogen evident in soils below alder is quickly integrated downslope. Additionally, there was a significant difference in the relative increase in plant biomass after nitrogen fertilization, with the greatest increase occurring in the no‐alder sites. This study demonstrates that streamside wetlands and streams are connected to the surrounding landscapes through hydrologic flow paths, and flow paths with alder stands are potential “hot spots” for nitrogen subsidies at the hillslope scale.