Habitat-specific bioaccumulation of methylmercury in invertebrates of small mid-latitude lakes in North America

We examined habitat-specific bioaccumulation of methylmercury (MeHg) in aquatic food webs by comparing concentrations in pelagic zooplankton to those in littoral macroinvertebrates from 52 mid-latitude lakes in North America. Invertebrate MeHg concentrations were primarily correlated with water pH, and after controlling for this influence, pelagic zooplankton had significantly higher MeHg concentrations than littoral primary consumers but lower MeHg than littoral secondary consumers. Littoral primary consumers and pelagic zooplankton are two dominant prey for fish, and greater MeHg in zooplankton is likely sufficient to increase bioaccumulation in pelagic feeders. Intensive sampling of 8 lakes indicated that habitat-specific bioaccumulation in invertebrates (of similar trophic level) may result from spatial variation in aqueous MeHg concentration or from more efficient uptake of aqueous MeHg into the pelagic food web. Our findings demonstrate that littoral-pelagic differences in MeHg bioaccumulation are widespread in small mid-latitude lakes.     

Tree decline in North America

Air-borne, phytotoxic pollutants are known to adversely affect forest tree growth in North America. On a local scale, exposure to high concentrations of toxic gases, such as sulphur dioxide and fluoride, result in foliar injury, branch dieback, reduced radial growth and increased mortality in a variety of tree species. On a regional scale, the photochemical oxidant, ozone, is responsible for growth decline of pollutant-sensitive eastern white pine genotypes in the eastern United States, and of ponderosa and Jeffrey pines in the mountains of southern and central California. The etiology associated with the reported declines of high elevation red spruce in the Appalachian Mountains and of sugar maple in the northeastern United States and southeastern Canada is incompletely known at present. A complex of predisposing and inciting factors, including temperature and moisture stress, edaphic conditions, aluminium toxicity, insect depredation, and air-borne pollutants are probably involved in these declines.     

Forest health conditions in North America

Some of the greatest forest health impacts in North America are caused by invasive forest insects and pathogens (e.g., emerald ash borer and sudden oak death in the US), by severe outbreaks of native pests (e.g., mountain pine beetle in Canada), and fires exacerbated by changing climate. Ozone and N and S pollutants continue to impact the health of forests in several regions of North America. Long-term monitoring of forest health indicators has facilitated the assessment of forest health and sustainability in North America. By linking a nationwide network of forest health plots with the more extensive forest inventory, forest health experts in the US have evaluated current trends for major forest health indicators and developed assessments of future risks. Canada and Mexico currently lack nationwide networks of forest health plots. Development and expansion of these networks is critical to effective assessment of future forest health impacts.     

Organic acidity in precipitation of North America

Organic anions were measured in 16 precipitation events sampled in central Virginia between 25 April and 1 October 1983. Formic and acetic acids contributed 16% of volume weighted free acidity. The decrease in free acidity in stored aliquots was directly proportional to the disappearance of dissociated HCOO⁻ and CH₃COO⁻. The loss of free acidity between pH measured at field sites and at central laboratories was used to estimate dissociated organic acidity in samples collected by the National Atmospheric Deposition Program (NADP) and the MAP3S Precipitation Chemistry Project. Based on the arithmetic means of the volume weighted averages for each site, we estimate that organic acids contributed 18–35% of free acidity in NADP samples and 16% of free acidity in MAP3S samples. The loss of free acidity in MAP3S samples was three times greater during the growing season than it was during the rest of the year. Because they are rapidly assimilated by microbes, organic acids are unimportant in the long-term acidification of the environment.     

Atmospheric aerosol measurements over North America and the North Atlantic Ocean

Measurements of atmospheric aerosol, obtained during thirty-nine transit flights within North America and across the North Atlantic Ocean, are presented and analyzed. The measurements comprise Aitken nucleus concentrations, particle size distributions, and the particle component of the light-scattering coefficient. Measurements of ozone are also presented.These data provide information on the ‘background’ and average values of the atmospheric aerosol in the lower and middle troposphere in continental, marine and high-latitude airmasses. The effects of temperature inversions, vertical mixing, clouds and precipitation, and stratospheric intrusions are illustrated. Time and spatial scales are derived for the transformations of the aerosol from those characteristic of a marine airmass into those characteristic of a continental airmass and vice versa.     

Advection climatology for the east coast of North America

The objective of this study is to determine the air mass advection eastward from the North American continent as a function of season, latitude and altitude. The eastern coastline of the continent has been subdivided into eight climatologicall y distinct and homogeneous segments on the basis of air stream and synoptic disturbance analysis. Mean resultant wind vectors and standard deviations have been derived for the 1000, 850, 700 and 500 mb levels from published analyses of upper air and surface winds in the period 1946–1964. Probablity wind roses were calculated assuming a bivariate normal distribution of wind vectors, and offshore and onshore air mass advection has been calculated for each season, coastal segment and layer. Offshore advection exhibits a broad maximum between 33 and 52°N, while onshore flow reaches a sharp maximum between 43 and 47°N because of the orientation of this segment. Offshore advection increases by a factor of approximately two for each successively higher layer, and the ratio of onshore to offshore flow decreases from 0.7 to 0.2 between the surface and layer 4. Winter air mass advection is ~ 1.8 times that in summer. Despite uncertainties introduced by the available wind data and the assumption of a normal distribution, the approach is considered to provide air mass advection values with an estimated uncertainty of about 25%. The results are expected to be useful for improved continental pollutant outflows and budgets.     

Organic nitrogen in precipitation over Eastern North America

A measurement technique was developed to reliably quantify organic nitrogen (ON) in ambient, wet-only precipitation. Samples were frozen during collection and subsequently divided into two aliquots. One set was stored at −170°C and analyzed for total N (TN) via high-temperature combustion to NO and detection by chemiluminescence; the other set was sterilized with CHCl₃, stored refrigerated, and analyzed for NH₄⁺ by automated colorimetry and for NO₃⁻, and NO₂⁻ by ion chromatography. ON was inferred by difference. Analysis of paired, untreated aliquots stored for 30 and 41 days at different temperatures revealed substantial conversion of NH₄⁺ to ON at room temperature and significant losses (16% and 23%) of NH₄⁺ (presumably to biota growing on bottle walls) in refrigerated samples. Analytes in frozen and sterilized samples were stable. Volume-weighted ON concentrations for precipitation sampled at Charlottesville, Virginia (VA), Newark, Delaware (DE), and New Castle, New Hampshire (NH; 3.1, 4.2, and 0.6 μM N, respectively) and corresponding contributions to volume-weighted TN (6.5%, 7.8%, and 2.6%, respectively) are at the lower limit of published values for eastern North America and elsewhere. Methodological differences contribute to the apparent variability among these reported sample statistics. Volume-weighted ON concentrations were generally highest during spring and were lowest during summer. Due to the combined influence of unmeasured ON and loss of NH₄⁺ from inadequately preserved samples, current estimates for the wet deposition of atmospheric N to eastern North America based on data from national networks may be underestimated by 10–20%.     

Patterns and Concentrations of PM10 in a Mountainous Basin Region

ABSTRACT

In this study, continuous data of PM₁₀ (particles with aerodynamic diameter <10 u,m) concentration measurements for a 4-yr period were analyzed. These measurements have been carried out in the Eordea Basin, an industrial area in the northwestern mountainous region of Greece. The annual, monthly, and diurnal patterns are presented and investigated regarding the prevailing meteorological conditions and atmospheric processes that affect the ambient concentrations of PM₁₀. The effect of wind on controlling PM₁₀ concentration is also discussed. Based on the data analysis, an attempt is made to provide useful information about air quality levels, taking into account U.S. Environmental Protection Agency air quality standards.     

Source apportionment of wet sulfate deposition in eastern North America

An analytical model of long distance transport of air pollutants (Fay and Rosenzweig, 1980. Atmospheric Environment 14, 355–365) has been adapted for the estimation of long term (e.g. annual) wet sulfate deposition in eastern N America. The model parameters have been optimized for best agreement with 1980–1982 measurements at 109 monitoring sites in this region. The root mean square residual of the model and measurement comparison is 4 kg ha ⁻¹y ⁻¹ ( 17% of the mean measured value). Transfer coefficients were found to decrease exponentially with source-receptor distance, having length scales between 1100 and 400 km depending upon whether the source is upwind or downwind of the receptor. Source apportionment calculated for four sites from this model shows that about half of the deposition is due to 7–8 of the largest source contributors to each site (aggregated to the state and sub-province level). A 17-year record of precipitation sulfate measured at Hubbard Brook, New Hampshire, compares favourably with the model calculation. Calculated U.S.-Canada transboundary fluxes differ from previous estimates. Isopleths of 1980–1982 yearly depositions were determined. A proposed 45 % reduction in U.S. sulfur emissions was found to produce about a 35% reduction of deposition at environmentally sensitive areas in the U.S. and Canada.     

Sensitivity of surface characteristics on the simulation of wind-blown-dust source in North America

Recently, a wind-blown-dust-emission module has been built based on a state-of-the-art wind erosion theory and evaluated in a regional air-quality model to simulate a North American dust storm episode in April 2001 (see Park, S.H., Gong, S.L., Zhao, T.L., Vet, R.J., Bouchet, V.S., Gong, W., Makar, P.A., Moran, M.D., Stroud, C., Zhang, J. 2007. Simulation of entrainment and transport of dust particles within North America in April 2001 (“Red Dust episode”). J. Geophys. Res. 112, D20209, doi:10.1029/2007JD008443). A satisfactorily detailed assessment of that module, however, was not possible because of a lack of information on some module inputs, especially soil moisture content. In this paper, the wind-blown-dust emission was evaluated for two additional dust storms using improved soil moisture inputs. The surface characteristics of the wind-blown-dust source areas in southwestern North America were also investigated, focusing on their implications for wind-blown-dust emissions. The improved soil moisture inputs enabled the sensitivity of other important surface characteristics, the soil grain size distribution and the land-cover, to dust emission to be investigated with more confidence. Simulations of the two 2003 dust storm episodes suggested that wind-blown-dust emissions from the desert areas in southwestern North America are dominated by emissions from dry playas covered with accumulated alluvial deposits whose particle size is much smaller than usual desert sands. As well, the source areas in the northwestern Texas region were indicated to be not desert but rather agricultural lands that were “activated” as a wind-blown-dust sources after harvest. This finding calls for revisions to the current wind-blown-dust-emission module, in which “desert” is designated to be the only land-cover category that can emit wind-blown dust.     

Metagenomic assessment of the microbial diversity in ground pork products from markets in the North Central Region of South Korea

The purpose of this study was to characterize the microbial community in ground pork using molecular approaches. Forty six ground pork products were purchased from local stores in the north central area of South Korea. Aerobic plate counts varied 4.23 ± 5.14 × 10⁵ CFU/g with the range between 5.00 × 10³ and 1.85 × 10⁶ CFU/g for ground pork samples. Four ground meat samples were further processed for metagenomic analysis. Pseudomonas species was the most relative abundant with a wide range occurring (1.72 to 77.7%) as part of the microbial genera in ground pork. Bacteria such as Carnobacterium, Yersinia, Photobacterium were also identified in ground pork. Despite the prominence of certain genera across all samples there was still extensive microbial diversity among ground pork products that originated from different slaughter houses and were processed in different markets. Such diversity indicates that designing interventions to extend shelf life may be hampered by the extensive variability in the microbial consortia associated with pork products. However, this diversity may be useful for developing microbial traceability signatures unique to a slaughter house or a particular market.     

Air emission inventories in North America: a critical assessment

Although emission inventories are the foundation of air quality management and have supported substantial improvements in North American air quality, they have a number of shortcomings that can potentially lead to ineffective air quality management strategies. Major reductions in the largest emissions sources have made accurate inventories of previously minor sources much more important to the understanding and improvement of local air quality. Changes in manufacturing processes, industry types, vehicle technologies, and metropolitan infrastructure are occurring at an increasingly rapid pace, emphasizing the importance of inventories that reflect current conditions. New technologies for measuring source emissions and ambient pollutant concentrations, both at the point of emissions and from remote platforms, are providing novel approaches to collecting data for inventory developers. Advances in information technologies are allowing data to be shared more quickly, more easily, and processed and compared in novel ways that can speed the development of emission inventories. Approaches to improving quantitative measures of inventory uncertainty allow air quality management decisions to take into account the uncertainties associated with emissions estimates, providing more accurate projections of how well alternative strategies may work. This paper discusses applications of these technologies and techniques to improve the accuracy, timeliness, and completeness of emission inventories across North America and outlines a series of eight recommendations aimed at inventory developers and air quality management decision-makers to improve emission inventories and enable them to support effective air quality management decisions for the foreseeable future.     

Air Emission Inventories in North America: A Critical Assessment

Abstract

Although emission inventories are the foundation of air quality management and have supported substantial improvements in North American air quality, they have a number of shortcomings that can potentially lead to ineffective air quality management strategies. Major reductions in the largest emissions sources have made accurate inventories of previously minor sources much more important to the understanding and improvement of local air quality. Changes in manufacturing processes, industry types, vehicle technologies, and metropolitan infrastructure are occurring at an increasingly rapid pace, emphasizing the importance of inventories that reflect current conditions. New technologies for measuring source emissions and ambient pollutant concentrations, both at the point of emissions and from remote platforms, are providing novel approaches to collecting data for inventory developers. Advances in information technologies are allowing data to be shared more quickly, more easily, and processed and compared in novel ways that can speed the development of emission inventories. Approaches to improving quantitative measures of inventory uncertainty allow air quality management decisions to take into account the uncertainties associated with emissions estimates, providing more accurate projections of how well alternative strategies may work. This paper discusses applications of these technologies and techniques to improve the accuracy, timeliness, and completeness of emission inventories across North America and outlines a series of eight recommendations aimed at inventory developers and air quality management decision-makers to improve emission inventories and enable them to support effective air quality management decisions for the foreseeable future.     

Background concentrations of 18 air toxics for North America

The U.S. Clean Air Act identifies 188 hazardous air pollutants (HAPs), or "air toxics," associated with adverse human health effects. Of these air toxics, 18 were targeted as the most important in a 10-City Pilot Study conducted in 2001 and 2002 as part of the National Air Toxics Trend Sites Program. In the present analysis, measurements available from monitoring networks in North America were used to estimate boundary layer background concentrations and trends of these 18 HAPs. The background concentrations reported in this study are as much as 85% lower than those reported in recent studies of HAP concentrations. Background concentrations of some volatile organic compounds were analyzed for trends at the 95% confidence level; only carbon tetrachloride (CCI4) and tetrachloroethylene decreased significantly in recent years. Remote background concentrations were compared with the one-in-a-million (i.e., 10(6)) cancer benchmarks to determine the possible causes of health risk in rural and remote areas; benzene, chloroform, formaldehyde, and chromium (Cr) fine particulate were higher than cancer benchmark values. In addition, remote background concentrations were found to contribute between 5% and 99% of median urban concentrations.     

Preparation of mercury emissions inventory for eastern North America

Point and area inventories of anthropogenic mercury emissions documented by US and Canadian environmental agencies have been aggregated into a single archive for analysis and air pollution modeling work. For 5341 point sources and 1634 aggregated area sources, mercury emissions are apportioned among elemental gaseous [Hg(0)], reactive gaseous[Hg(II)], and particulate [Hg(p)] emissions using speciation factors derived from available monitoring measurements. According to this inventory, 4.82 x 10(5) mol of mercury were emitted in calendar year 1996 in the latitude range 24-51 degrees north, and longitude range 64-91 degrees west, which covers most of North America east of the Mississippi River. Using speciation factors consistent with past emission source studies, we find the relative emission proportions among Hg(0):Hg(II):Hg(p) species are 47:35:18. Maps of the various mercury species' emissions patterns are presented. Gridded emission patterns show local mercury emission extremes associated with individual cement production and municipal incineration facilities, and in contrast to past inventories, population centers do not stand out. Considerable uncertainties are still present in estimating emissions from large point sources, as are methods of apportioning emissions among various mercury species.     

Modeling of mercury emission,transport and deposition in North America

Most studies on the atmospheric behaviour of mercury in North America have excluded a detailed treatment of natural mercury emissions. The objective of this work is to report a detailed simulation of the atmospheric mercury in a domain that covers a significant part of North America and includes not only anthropogenic mercury emissions but also those from natural sources including vegetation, soil and water.The simulations were done using a natural mercury emission model coupled with the US EPA's SMOKE/CMAQ modelling system. The domain contained 132×90 grid cells at a resolution of 36 km, covering the continental United States, and major parts of Canada and Mexico. The simulation was carried out for 2002, using boundary conditions from a global mercury model. Estimated total natural mercury emission in the domain was 230 tonnes (1 tonne=1000 kg) and the ratio of natural to anthropogenic emissions varied from 0.7 in January to 3.2 in July. Average total gaseous mercury (TGM) concentration ranged between 1 and 4 ng m⁻³. Good agreement was found between the modelled results and measurements at three Ontario sites for ambient mercury concentrations, and at 72 mercury deposition network sites in the domain for wet deposition. The correlation coefficient between the simulated and the measured values of the daily average TGM at three monitoring sites varied between 0.48 and 0.64. When natural emissions were omitted, the correlation coefficients dropped to between 0.15 and 0.40. About 335 tonnes of mercury were deposited in the domain during the simulation period but overall, it acted as a net source of mercury and contributed about 21 tonnes to the global pool. The net deposition of mercury to the Great Lakes was estimated to be about 2.4 tonnes. The estimated deposition values were similar to those reported by other researchers.     

Organochlorine pesticide contamination in grassland-nesting passerines that breed in North America

Organochlorine pesticides and metabolites were measured in grassland-nesting passerines that breed in North America. We also examined testes of male birds for abnormalities that may have resulted from pesticide exposure. Forty-four of 99 individuals contained one or more organochlorine pesticides above the detection limit, representing nine of 10 species. The most prevalent compound detected was p,p'-DDE (minimum-maximum levels: 7.55-285.85 ng/g, carcass concentration). Insectivorous birds had significantly higher levels of p,p'-DDE than both omnivores and granivores. Birds that frequented moist grassland habitats had significantly higher levels of p,p'-DDE than those that frequented drier grassland habitats. No evidence of feminization was observed in any of the testes analyzed, however, other endpoint effects of contamination (e.g. hormone levels and immunological parameters) should be investigated in future studies.