Airborne Emissions of Mercury from Municipal Solid Waste. II: Potential Losses of Airborne Mercury before Landfill

Abstract

Waste distribution and compaction at the working face of municipal waste landfills releases mercury vapor (Hg⁰) to the atmosphere, as does the flaring of landfill gas. Waste storage and processing before its addition to the landfill also has the potential to release Hg⁰ to the air if it is initially present or formed by chemical reduction of Hg^II to Hg⁰ within collected waste. We measured the release of Hg vapor to the atmosphere during dumpster and transfer station activities and waste storage before landfilling at a municipal landfill operation in central Florida. We also quantified the potential contribution of specific Hg-bearing wastes, including mercury (Hg) thermometers and fluorescent bulbs, and searched for primary Hg sources in sorted wastes at three different landfills. Surprisingly large fluxes were estimated for Hg losses at transfer facilities (～100 mg/hr) and from dumpsters in the field (～30 mg/hr for 1,000 dumpsters), suggesting that Hg emissions occurring before landfilling may constitute a significant fraction of the total emission from the disposal/landfill cycle and a need for more measurements on these sources. Reducing conditions of landfill burial were obviously not needed to generate strong Hg⁰ signals, indicating that much of the Hg was already present in a metallic (Hg⁰) form. Attempts to identify specific Hg sources in excavated and sorted waste indicated few readily identifiable sources; because of effective mixing and diffusion of Hg⁰, the entire waste mass acts as a source. Broken fluorescent bulbs and thermometers in dumpsters emitted Hg⁰ at 10 to >100 μg/hr and continued to act as near constant sources for several days.     

Emission Factors for High-Emitting Vehicles Based on On-Road Measurements of Individual Vehicle Exhaust with a Mobile Measurement Platform

ABSTRACT

Fuel-based emission factors for 143 light-duty gasoline vehicles (LDGVs) and 93 heavy-duty diesel trucks (HDDTs) were measured in Wilmington, CA using a zero-emission mobile measurement platform (MMP). The frequency distributions of emission factors of carbon monoxide (CO), nitrogen oxides (NO_x), and particle mass with aerodynamic diameter below 2.5 μm (PM_2.5) varied widely, whereas the average of the individual vehicle emission factors were comparable to those reported in previous tunnel and remote sensing studies as well as the predictions by Emission Factors (EMFAC) 2007 mobile source emission model for Los Angeles County. Variation in emissions due to different driving modes (idle, low- and high-speed acceleration, low- and high-speed cruise) was found to be relatively small in comparison to intervehicle variability and did not appear to interfere with the identification of high emitters, defined as the vehicles whose emissions were more than 5 times the fleet-average values. Using this definition, approximately 5% of the LDGVs and HDDTs measured were high emitters. Among the 143 LDGVs, the average emission factors of NO_x, black carbon (BC), PM_2.5, and ultrafine particle (UFP) would be reduced by 34%, 39%, 44%, and 31%, respectively, by removing the highest 5% of emitting vehicles, whereas CO emission factor would be reduced by 50%. The emission distributions of the 93 HDDTs measured were even more skewed: approximately half of the NO_x and CO fleet-average emission factors and more than 60% of PM_2.5, UFP, and BC fleet-average emission factors would be reduced by eliminating the highest-emitting 5% HDDTs. Furthermore, high emissions of BC, PM_2.5, and NO_x tended to cluster among the same vehicles.

IMPLICATIONS This study presents the characterization of on-road vehicle emissions in Wilmington, CA, by sampling individual vehicle plumes. Approximately 5% of the vehicles were high emitters, whose emissions were more than 5 times the fleet-average values. These high emitters were responsible for 30% and more than 50% of the average emission factors of LDGVs and HDDVs, respectively. It is likely that as the overall fleet becomes cleaner due to more stringent regulations, a small fraction of the fleet may contribute a growing and disproportionate share of the overall emissions. Therefore, long-term changes in on-road emissions need to be monitored.     

Megafaunal-habitat associations at a deep-sea coral mound off North Carolina,USA

Deep-sea corals provide important habitat for many organisms; however, the extent to which fishes and other invertebrates are affiliated with corals or other physical variables is uncertain. The Cape Fear coral mound off North Carolina, USA (366–463 m depth, 33° 34.4′N, 76° 27.8′W) was surveyed using multibeam sonar and the Johnson-Sea-Link submersible. Multibeam bathymetric data (2006) were coupled with in situ video data (2002–2005) to define habitat associations of 14 dominant megafauna at two spatial scales. Results suggested greater habitat specificity of deep-reef fauna than previously documented, with fishes showing greater affinity for certain habitat characteristics than most invertebrates. High vertical profile, degree of coral coverage, and topographic complexity influenced distributions of several species, including Beryx decadactylus, Conger oceanicus, and Novodinia antillensis on the smaller scale (30 × 30 m). On the broad scale (170 × 170 m), several suspension feeders (e.g., N. antillensis, anemones), detritivores (Echinus spp.), and mesopelagic feeders (e.g., Beryx decadactylus, Eumunida picta) were most often found on the south-southwest facing slope near the top of the mound. Transient reef species, including Laemonema barbatulum and Helicolenus dactylopterus, had limited affiliations to topographic complexity and were most often on the mound slope and base. Megafauna at deep-water reefs behave much like shallow-water reef fauna, with some species strongly associated with certain fine-scale habitat attributes, whereas other species are habitat generalists. Documenting the degree of habitat specialization is important for understanding habitat functionality, predicting faunal distributions, and assessing the impacts of disturbance on deep-reef megafauna.     

Bottoms up: great bustards use the sun to maximise signal efficacy

Visual displays are signals that may be selected to increase visibility. Light is a crucial component in the transmission of visual signals, and white colour is very conspicuous when illuminated by sun and exhibited against darker backgrounds. Here we tested the hypothesis that orientation of sexual displays in male great bustard (Otis tarda) depends upon position of the sun, i.e., males direct their uplifted white tails towards the sun in order to maximise signal detectability to distant females. We recorded the orientation of 405 male displays in relation to the sun and to females at seven leks. Great bustard males signalled towards the sun more often than expected by chance in early morning, although this pattern was not obvious at other times of day, when males displayed more towards females. Our hypothesis was further supported by the fact that displays were more directed towards the sun when the sun was most visible. Males were more likely to direct their displays towards females during the most elaborate components of their courtship display and when there were fewer males on the lek. Pointing white plumage to the sun may be a behaviour selected in species living in steppe-like open landscapes if individuals obtain net fitness benefit by increasing the likelihood of mating.     

Inconsistent definitions of "urban" result in different conclusions about the size of urban carbon and nitrogen stocks

There is conflicting evidence about the importance of urban soils and vegetation in regional C budgets that is caused, in part, by inconsistent definitions of "urban" land use. We quantified urban ecosystem contributions to C stocks in the Boston (Massachusetts, USA) Metropolitan Statistical Area (MSA) using several alternative urban definitions. Development altered aboveground and belowground C and N stocks, and the sign and magnitude of these changes varied by land use and development intensity. Aboveground biomass (live trees, dbh > or = 5 cm) for the MSA was 7.2 +/- 0.4 kg C/m2 (mean +/- SE), reflecting a high proportion of forest cover. Vegetation C was highest in forest (11.6 +/- 0.5 kg C/m2), followed by residential (4.6 +/- 0.5 kg C/m2), and then other developed (2.0 +/- 0.4 kg C/m2) land uses. Soil C (0-10 cm depth) followed the same pattern of decreasing C concentration from forest, to residential, to other developed land uses (4.1 +/- 0.1, 4.0 +/- 0.2, and 3.3 +/- 0.2 kg C/m2, respectively). Within a land use type, urban areas (which we defined as > 25% impervious surface area [ISA] within a 1-km(2) moving window) generally contained less vegetation C, but slightly more soil C, than nonurban areas. Soil N concentrations were higher in urban areas than nonurban areas of the same land use type, except for residential areas, which had similarly high soil N concentrations. When we compared our definition of urban to other commonly used urban extents (U.S. Census Bureau, Global Rural-Urban Mapping Project [GRUMP], and the MSA itself), we found that urban soil (1 m depth) and vegetation C stocks spanned a wide range, from 14.4 +/- 0.8 to 54.5 +/- 3.4 Tg C and from 4.2 +/- 0.4 to 27.3 +/- 3.2 Tg C, respectively. Conclusions about the importance of urban soils and vegetation to regional C and N stocks are very sensitive to the definition of urban used by the investigators. Urban areas, regardless of definition, are rapidly expanding in their extent; a systematic understanding of how our development patterns influence ecosystems is necessary to inform future development choices.     

The "cultural filter", human transport of mussel shell, and the applied potential of zooarchaeological data

Large assemblages of animal bones and/or shells from archaeological sites can provide data valuable for modern conservation efforts, e.g., by providing accurate historical baselines for species reintroductions or habitat restoration. Such data are underused by natural scientists, partly due to assumptions that archaeological materials are too biased by prehistoric human actions (the so-called "cultural filter") to accurately reflect past biotic communities. In order to address many paleobiological, archaeological, or applied research questions, data on past species, communities, and populations must first be demonstrated to be representative at the appropriate level. We discuss different ways in which one kind of cultural bias, human transport of specimens, can be tested at different scales, using freshwater mussel shells from prehistoric sites in the Tombigbee River basin of Mississippi and Alabama to show how representativeness of samples can be assessed.     

Work stressors and coworker support as predictors of individual strain and job performance

This study examined job stressors and coworker social support in relation to both psychological strains and performance. One hundred and ninety‐eight door‐to‐door bookdealers, employed on a seasonal basis, completed self‐report measures of job stressors, psychological strains, coworker social support, and job performance. Performance data were also obtained from company records. Results indicated that stressors predicted both psychological strains and one of the two measures of performance. The strongest predictor was a job‐specific measure of chronic stressors. Social support predicted psychological strains, although it was only weakly related to performance. There was no evidence that social support moderated the effects of any of the stressors. Implications of these findings are discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

Copper uptake by Elsholtzia splendens and Silene vulgaris and assessment of copper phytoavailability in contaminated soils

Tolerance and metal uptake are two essential characteristics required for phytoextraction of metals from contaminated soils. We compared tolerance and Cu uptake of Elsholtzia splendens (reported previously to be a Cu hyperaccumulator) with Silene vulgaris (the Imsbach population, a well-known Cu-tolerant excluder species), using 30 soils varying widely in total Cu concentration (19-8645 mg kg(-1)). We further investigated the effectiveness of different soil testing methods for predicting plant metal uptake. The results showed that both Elsholtzia splendens and Silene vulgaris were tolerant to Cu, especially Silene vulgaris. However, Elsholtzia splendens did not hyperaccumulate Cu, but behaved as a typical Cu excluder like Silene vulgaris. The concentrations of Cu in both plants correlated more closely with 1 M NH4NO3 extractable Cu, soil solution Cu, or effective Cu concentration determined using DGT, than with soil total Cu, EDTA extractable Cu or free Cu2+ activity. The relationships between soil solution properties and root Cu concentrations were further investigated using multiple regression. The results showed that increasing soil solution pH increased root Cu concentration when free Cu2+ activity was held constant, suggesting a higher phytoavailability of free Cu2+ at a higher pH. Soil solution DOC appeared to play two contrasting roles on the phytoavailability of Cu: (1) reducing Cu availability by complexing Cu; and (2) increasing Cu availability at the same level of free Cu2+ activity by providing a strong buffer for free Cu2+. The results are consistent with the intensity/capacity concept for phytoavailability of metals in soils.     

Guiding principles for rewilding

There has been much recent interest in the concept of rewilding as a tool for nature conservation, but also confusion over the idea, which has limited its utility. We developed a unifying definition and 10 guiding principles for rewilding through a survey of 59 rewilding experts, a summary of key organizations’ rewilding visions, and workshops involving over 100 participants from around the world. The guiding principles convey that rewilding exits on a continuum of scale, connectivity, and level of human influence and aims to restore ecosystem structure and functions to achieve a self-sustaining autonomous nature. These principles clarify the concept of rewilding and improve its effectiveness as a tool to achieve global conservation targets, including those of the UN Decade on Ecosystem Restoration and post-2020 Global Biodiversity Framework. Finally, we suggest differences in rewilding perspectives lie largely in the extent to which it is seen as achievable and in specific interventions. An understanding of the context of rewilding projects is the key to success, and careful site-specific interpretations will help achieve the aims of rewilding.     

Decabromodiphenylether and hexabromocyclododecane in wild birds from the United Kingdom, Sweden and The Netherlands: Screening and time trends

The brominated flame retardant decabromodiphenylether (DBDE) was analysed in wild birds to identify the most suitable species for monitoring time trends in DBDE contamination. This information was later used for the design of a 10-year trend study on DBDE in the European Union. DBDE was measured in muscle tissue, liver, and eggs from 10 terrestrial and four aquatic bird species. DBDE was detected in 47% of the terrestrial bird samples (nine species) and in 9% of the aquatic bird samples (six species). Peregrine falcon and sparrowhawk specimens were selected as most suitable species to determine temporal trends of DBDE. For sparrowhawks, no significant change in DBDE concentrations between 1973 and 2001 was found, although in later years more DBDE concentrations were above the detection limit. Peak DBDE levels measured in peregrines in 1995, were followed by a decline in concentrations until 2001. The same species were used for a trend study on hexabromocylcododecane (HBCD). Twenty-four percent of peregrine falcon eggs and 12% of sparrowhawk muscle samples demonstrated measurable HBCD residues. Three diastereomers of HBCD were analysed and the α-diastereomer was the predominant one in most samples. No clear time trends were observed for HBCD in either species. This study demonstrated that these DBDE and HBCD are bioavailable to birds of Northern Europe, although bioaccumulation seems to occur to a limited extent.