Indoor- and outdoor-derived contaminants in urban and rural homes in Ottawa, Ontario, Canada

Indoor and outdoor air contaminants have largely been treated separately in studies of their respective effects on respiratory and nonrespiratory health. In this paper, we report the results of a comprehensive study of key contaminants in 10 urban and 10 rural homes in Ottawa, Ontario, Canada. The analyses included house dust mite and cat allergens along with the fungal inflammatory polysaccharide beta1,3-D-glucan in settled dust and fine particulate matter, coarse particulate matter, ergosterol, glucan, and endotoxin from air samples. In addition, black carbon was continuously measured for 7 days. A detailed physical assessment of the house and patterns of use were undertaken, including a careful inspection for mold and water damage, as well as measurements of air leakage. The performance of the houses and the range and distribution of the contaminants measured were largely similar to that of previous Canadian studies. For certain combinations, it is thought that the presence of both allergen and inflammatory materials increases asthma symptoms. House-by-house comparisons of airborne concentrations of inflammatory compounds measured (endotoxin, fine particulate matter, and fungal glucan) with dust mite allergens indicated that certain houses had relatively higher amounts of both kinds of materials.     

Assessing the effects of transboundary ozone pollution between Ontario,Canada and New York,USA

We investigated the effects of transboundary pollution between Ontario and New York using both observations and modeling results. Analysis of the spatial scales associated with ozone pollution revealed the regional and international character of this pollutant. A back-trajectory-clustering methodology was used to evaluate the potential for transboundary pollution trading and to identify potential pollution source regions for two sites: CN tower in Toronto and the World Trade Center in New York City. Transboundary pollution transport was evident at both locations. The major pollution source areas for the period examined were the Ohio River Valley and Midwest. Finally, we examined the transboundary impact of emission reductions through photochemical models. We found that emissions from both New York and Ontario were transported across the border and that reductions in predicted O3 levels can be substantial when emissions on both sides of the border are reduced.     

Leeches as indicators of dietary mercury exposure in non-piscivorous waterfowl in central Ontario, Canada

We collected and analysed 113 leeches (Hirudinea) from 17 small lakes in the acid-stressed Muskoka region of central Ontario, Canada to examine the relationship between lake chemistry and mercury (Hg) concentrations in leeches, and thus determine whether leeches and other benthic invertebrates posed a dietary risk of Hg exposure for non-piscivorous waterfowl. Hg concentrations in leeches were generally low and only a few-fold above the detection limit (0.78 ng g(-1) wet weight (ww)). Mean Hg concentration in the bloodsucker Macrobdella decora was 6.94 +/- 0.78 SE ng g(-1) ww (n=49) and was 5.98 +/- 0.46 ng g(-1) ww (n=64) in the scavenger Percymoorensis marmoratis. Leech Hg concentrations were correlated with calcium and dissolved organic carbon concentrations in the water, respectively. These data suggest that leeches are not suitable monitors of Hg (usually as methylmercury) biomagnification in central Ontario lakes, and do not pose a dietary risk to non-piscivorous waterfowl.     

The Pb pollution fingerprint at Lochnagar: the historical record and current status of Pb isotopes

Ratios of 206Pb/207Pb in a Lochnagar sediment core slowly decline from c. 1.32 at 140 cm to c. 1.23 at 9 cm, and then rapidly decline to c. 1.15 at the surface. Ninety percent of the Pb in the surface sediments can be attributed to anthropogenic sources. The 206Pb/207Pb ratio data imply that catchment peat surface contains a higher fraction of anthropogenic Pb than the sediment surface. The 206Pb/207Pb ratios in the surface of the sediment core are consistent with ratios in trapped sediments collected annually between 1998 and 2003. However, there is no significant decline in these recent samples suggesting that the reduction in atmospheric Pb emissions has not yet been recorded by the sediments due to Pb inputs from the catchment. As catchment peats store about 840 kg previously deposited anthropogenic Pb since 1860, it is likely that catchment inputs will continue to affect future 206Pb/207Pb ratios.     

Environmental and economic evaluation of bioenergy in Ontario, Canada

We examined life cycle environmental and economic implications of two near-term scenarios for converting cellulosic biomass to energy, generating electricity from cofiring biomass in existing coal power plants, and producing ethanol from biomass in stand-alone facilities in Ontario, Canada. The study inventories near-term biomass supply in the province, quantifies environmental metrics associated with the use of agricultural residues for producing electricity and ethanol, determines the incremental costs of switching from fossil fuels to biomass, and compares the cost-effectiveness of greenhouse gas (GHG) and air pollutant emissions abatement achieved through the use of the bioenergy. Implementing a biomass cofiring rate of 10% in existing coal-fired power plants would reduce annual GHG emissions by 2.3 million metric tons (t) of CO2 equivalent (7% of the province's coal power plant emissions). The substitution of gasoline with ethanol/gasoline blends would reduce annual provincial lightduty vehicle fleet emissions between 1.3 and 2.5 million t of CO2 equivalent (3.5-7% of fleet emissions). If biomass sources other than agricultural residues were used, additional emissions reductions could be realized. At current crude oil prices ($70/barrel) and levels of technology development of the bioenergy alternatives, the biomass electricity cofiring scenario analyzed is more cost-effective for mitigating GHG emissions ($22/t of CO2 equivalent for a 10% cofiring rate) than the stand-alone ethanol production scenario ($92/t of CO2 equivalent). The economics of biomass cofiring benefits from existing capital, whereas the cellulosic ethanol scenario does not. Notwithstanding this result, there are several factors that increase the attractiveness of ethanol. These include uncertainty in crude oil prices, potential for marked improvements in cellulosic ethanol technology and economics, the province's commitment to 5% ethanol content in gasoline, the possibility of ethanol production benefiting from existing capital, and there being few alternatives for moderate-to-large-scale GHG emissions reductions in the transportation sector.     

Geochemistry of a septic-system plume in a coastal barrier bar, Point Pelee, Ontario, Canada

The major ion and trace metal geochemistry of a septic system plume in a shallow sand aquifer was characterized to assess geochemical processes controlling the transport of nutrients and their release to a nearby wetland. The plume was generated from a 16-year-old tile bed, and is more than 60 m long, 40 m wide and 7 m thick. The groundwater pH at the site is near neutral, but up to 0.4 units lower in the plume core as a result of H⁺ generated from NH₃ and DOC oxidation in the unsaturated zone. The plume can be divided into distinct redox zones, which show differences in nutrient mobility. Proximal to the tile bed, there is a shallow suboxic zone, with intermediate Eh values (>400 mV), low concentrations of dissolved oxygen (<1.0 mg/l), and elevated concentrations of Mn (1–3 mg/l) and nutrients (10–80 mg/l NO₃–N, 1–15 mg/l NH₃–N, 0.1–1.5 mg/l PO₄–P, 6–13 mg/l dissolved organic carbon). At the base of the aquifer, there is a reduced zone (Eh<200 mV) with elevated concentrations of Fe (1–14 mg/l), PO₄ and NH₃, but negligible concentrations of NO₃ (<0.01 mg/l N). Distal from the tile bed, the shallow groundwater is suboxic to oxic, and has elevated concentrations of NO₃ and NH_3, but negligible PO₄. In the lower reduced zone, elevated concentrations of PO₄ occur up to 60 m away. The release of groundwater containing even very low concentrations of PO₄ (<0.02 mg/l P) can lead to the development of eutrophic conditions in surface water bodies. Geochemical calculations indicate that, in the Mn-rich zone, the groundwater is close to saturation or supersaturated with respect to hydroxyapatite, rhodochrosite, calcite and ferrihydrite. In the reduced zone, the groundwater is close to saturation or supersaturated with respect to hydroxyapatite, vivianite, calcite and siderite. Formation of these phases, or related phases, are likely limiting the concentrations of dissolved PO₄, Fe and Mn and controlling the geochemical evolution of the plume.     

The solid-phase controls on the mobility of heavy metals at the Copper Cliff tailings area, Sudbury, Ontario, Canada

The Copper Cliff Tailings Disposal Area, located near Sudbury, Ontario, covers an area of approximately 2200 ha and constitutes more than 10% of the total area of all mine tailings in Canada. The area has been utilized since 1936, receiving sulphide-containing tailings from the Inco Sudbury operations. Field measurements of pore-gas oxygen and carbon dioxide in the vadose zone indicate that sulphide oxidation has progressed to depths of 1.6 m to 1.7 m within the tailings. The oxidation of sulphide minerals within the vadose zone, and the accompanying dissolution of carbonate and aluminosilicate minerals within these tailings releases SO₄, Fe(II) and other metals to the pore water. In the vadose and saturated zones, concentrations of Fe and Ni exceed 10100 mg/l and 2210 mg/l, respectively. These high concentrations of dissolved metals are attenuated by a series of precipitation, coprecipitation and adsorption reactions. The precipitation of secondary sulphate and hydroxide phases also create hardpan layers at or near the oxidation front. Geochemical modelling of the pore-water chemistry suggests that pH-buffering reactions are occurring within the shallow oxidized zones, and that secondary-phase precipitation is occurring at or near the underlying hardpan and transition zones. Mineralogical study of the tailings confirmed the presence of jarosite, gypsum and goethite within the shallow tailings, suggesting that these phases are controlling the dissolved concentrations of Fe, SO₄ and Ca. Extraction experiments conducted on the tailings solids indicate that the constituents contained in the water-soluble fraction of the shallow, weathered tailings are derived from the original pore water and the dissolution of highly soluble phases such as gypsum. The acid-leachable fraction of the weathered tailings accounts for up to 25% of the heavy metals, and the reducible fraction may contain up to 100% of the heavy metals within the shallow, weathered tailings. Based on the pore water profiles and the geochemistry of the tailings solids, a relative mobility scale of Fe=Mn=Ni=Co>Cd Zn>Cr=Pb>Cu can be determined.     

Discussion of a lagrangian trajectory model describing long-range transport of oxides of nitrogen,the incorporation of pan in the chemical mechanism,and supporting measurements of pan and nitrate species at rural sites in Ontario,Canada

The derivation of a highly simplified parameterization of NO_x chemistry for use with the AES Lagrangian trajectory model is described. Two versions, both employing essentially independent first-order kinetics are discussed:

• 1.(1) a one step mechanism: NO₂→ inorganic nitrate and
• 2.(2) a somewhat more involved reaction scheme including PAN chemistry.

Evaluation of model performance is attempted with data from the Canadian Air and Precipitation Monitoring Network (APN). It is shown that both model versions are able to reproduce trends of annual and monthly average atmospheric nitrate concentrations, although the models tend to suggest transport over larger distances than is apparent from the field data. The inclusion of PAN chemistry appears to improve the model performance. However, the model predicts a winter maximum and a summer minimum for the annual profile of PAN, and this is in direct contradiction with field measurements of PAN elsewhere. Initial results from a PAN measurement program conducted at three sites in Ontario are also reported and compared with the second model version. Observations for summer 1982 are predicted quite well, but data collected during March 1983 are substantially overpredicted. It is indicated that during periods of rain, PAN constitutes the major oxidized NO_x component. The suggestion is made that this observation is due to a much more efficient precipitation scavenging of nitrate species than of PAN.     

Urban and rural ozone concentrations in Alberta,Canada

Ozone concentrations in Alberta cities typically exhibit a maximum in May (up to 35 ppb) and a minimum in November (as low as 4 ppb). This behaviour is similar to that of rural Alberta O₃ concentrations. Annual O₃ concentrations at six urban monitoring stations vary from 11 ppb to 22 ppb and are about one-half the values at rural stations. In winter, urban O₃ concentrations are always smaller than rural concentrations and the cities act as sinks for O₃. Although urban stations do not exceed Canada's maximum acceptable levels of daily (25 ppb) and annual (15 ppb) O₃ concentrations as often as rural stations, the frequency is still quite large. Canada's hourly maximum desirable level (50 ppb) is exceeded 11 times more often at the remote (rural) station than at the downtown (urban) stations.     

Analysis of the air pollution climate at a central urban background site

Measurements of air pollutants from a background site in central London are analysed. These comprise hourly data for CO, NO, NO₂, O₃, SO₂ and PM₁₀ from 1996 to 2008 and particle number count from 2001 to 2008. The data are analysed in terms of long-term trends, annual, weekly and diurnal cycles, and autocorrelation and cross-correlation functions. CO, NO and NO₂ show a typical traffic-associated pattern with two daily peaks and lesser concentrations at the weekend. Particle number count and PM₁₀ show a similar cycle, but with smaller amplitude. Ozone has an annual cycle with a maximum in May, influenced by the spring maximum in background ozone, but the diurnal and weekly cycles are dominated by losses through reaction with nitric oxide. Particle number count shows a minimum corresponding with maximum air temperatures in August, whereas the CO, NO NO₂ and SO₂ show a minimum in June/July. There is a lower particle count to NO_x ratio at the background site compared to a central London kerbside site (Marylebone Road) and a seasonal pattern in particle count to NO_x and PM₁₀ ratios consistent with loss of nanoparticles by evaporation during atmospheric transport. Sulphur dioxide peaks in the morning in summer, but at midday in winter consistent with emissions from elevated sources mixing down from aloft as the diurnal mixed layer deepens. Implications for epidemiological studies of air quality and health are discussed. Sulphur dioxide, carbon monoxide, nitric oxide and nitrogen dioxide show clear downward trends over the measurement period, PM₁₀ declines initially before levels stabilised, and ozone concentrations increased.     

A winter study of air,cloud and precipitation chemistry in Ontario,Canada

During January and February 1984, a field project was conducted near North Bay, Ontario, Canada. The principal objective was to characterize the chemical and microphysical properties of the air masses, clouds and precipitation in this region of NE North America during the winter season. Two extensively instrumented aircraft with some newly designed cloudwater and snow collectors were used, as well as a surface station continuously monitoring pollutant concentrations and a precipitation event sampling network. Pollutant concentrations at the surface were found to vary with the airmass back trajectory with the highest concentrations observed for trajectories from the S and SW and the lowest from the N. Vertical profiles of aerosol particle (0.2−2 μm diameter) and NOx concentrations show similar trends with maxima of 1200 cm⁻³ and 7 ppb, respectively near ground level with air mass trajectories from the S, in comparison to values of 250 cm⁻³ and 1 ppb obtained with trajectories from the N. Cloudwater, aircraft precipitation and ground precipitation samples had a daily median pH of 3.6,4.6 and 4.2, respectively with the cloudwater having the highest sulphate and nitrate concentrations. The nitrate/sulphate equivalent concentration ratios in the cloudwater, aircraft precipitation and ground precipitation samples were 0.7,0.6 and 1.4, respectively. The data suggest that precipitation scavenging of nitric acid below cloud base is an important process during the winter season.     

无锡市农村黑臭河流沉积物营养盐垂向分布与污染特征分析

为揭示太湖流域农村黑臭河流沉积物中碳、氮、磷营养盐的垂向分布与污染特征,以无锡市周铁镇掌下浜(北段)为例,沿河流上游至下游共采集13个沉积物柱状样,分析总氮(TN)、总磷(TP)、氨氮(NH4+-N)、硝氮(NO3--N)、有机氮(Org-N)、有机碳(TOC)的垂向分布特征,并对沉积物中碳(C)、氮(N)、磷(P)的组分分布进行相关性分析。结果表明:TN、TP、Org-N含量在各点位间变化幅度不同,但均表现出随深度增加减小的趋势,即出现明显的"表层富集"现象,TN、TP、Org-N含量在沉积物中的最大降幅分别为55.82%、69.59%和68.12%;相反,沉积物中NH4+-N含量在垂直距离上呈现随深度加大升高的趋势,上升幅度在25.39%~72.77%;在垂直方向上,NO3--N含量在1号、4号~8号采样点处含量随深度加大而升高,增幅最大为107.51%,在2号、3号和9号~13号采样点处含量随深度增加降低,降幅最大为65.17%;TOC含量呈现随深度增加递减的趋势,含量在13.12~37.52 g·kg-1变化;沉积物中C/N在8.31~19.90之间,均值为13.21,有机物以外源有机质为主;C/P比在12.24~51.84之间,均值为26.71;N/P在1.04~2.86之间,均值为2.02;沉积物中TOC、TN、TP含量两两具有极显著正相关关系(pn=13),表明C、N和P具有同源性。     

Study of organochlorine pollutants in snow at North Pole and comparison to the snow at north, central and south Finland

Organic pollutants, especially polychlorinated hydrocarbons, phenols, guaiacols and catechols have been studied by analyses of snow samples from North Pole, May 1984. All of these pollutants were below the limit of determination which was estimated to be as fallout 0.1–0.05 μg/m² for individual compounds. For comparison, snow samples from Central Finland and South Finland 1983–1985 also showed non-detectable levels of chlorinated hydrocarbons but well measurable levels of chlorophenol compounds which were significantly higher at urban (heavy traffic) than rural and higher at South than Central Finnish places, respectively. One sample from Lapland, North Finland 1985, however, had no measurable amounts of chlorophenols like the North Pole sample.     

The contribution of middle- and long-range transport of tropospheric photochemical ozone to pollution at a rural site in North-West England

Ground-level ozone measurements from a rural site in North-West England are presented. Two distinct types of polluted air mass are identified: one type having passed over the North Sea and Northern England, and the other having travelled from the continent via the South-East and Midlands of England. The former air mass type contains long-range transported ozone originating primarily within continental Europe, whilst the latter type contains both long-range transported ozone and ozone formed from precursors injected during passage of the air mass over middle-distance source areas in England. The monitoring results are compared with the predictions of recent theoretical models of ozone formation in polluted air masses and urban plumes.     

Observational study of ozone pollution at a rural site in the Yangtze Delta of China

Ozone and related trace gases (CO, NO_x, and SO₂) were measured from June 1999 to July 2000 at a rural site in the Yangtze Delta of China, a region of intensive anthropogenic activity. Elevated ozone levels were frequently observed during the study period, with the highest frequency in late spring and early summer. Over a 1 yr period, 21 d were found to have ozone concentrations exceeding the new US 8-h 80 ppb health standard. Calculation of the “SUM06” exposure index also shows relatively high (>15 ppm h) values for each season except winter. At these levels ozone may have adverse effects on human health as well as agricultural crops. Analysis of meteorological data shows that the high ozone days were associated with large-scale stagnation, intense solar radiation, and minimum rainfall. Large-scale back trajectories indicate a slow-moving/re-circulating airmass during the episodic days. Examination of chemical data shows that the observed daytime high ozone concentrations were due to downward mixing of ozone-rich air, in situ photochemical formation, and in some cases, advection to the site of aged plumes. The very high CO levels (and high CO to NO_x ratios) were found to coincide with many of the ozone episodes, suggesting a contribution from sources of emission involving incomplete combustion. It is suggested that the burning of biomass (e.g., biofeuls and crop residues) may be an important source for the observed high CO and O₃ values.     

Sources of personal exposure to fine particles in Toronto, Ontario, Canada

Individuals are exposed to particulate matter from both indoor and outdoor sources. The aim of this study was to compare the relative contributions of three sources of personal exposure to fine particles (PM2.5) by using chemical tracers. The study design incorporated repeated 24-hr personal exposure measurements of air pollution from 28 cardiac-compromised residents of Toronto, Ontario, Canada. Each study participant wore the Rupprecht & Patashnick ChemPass Personal Sampling System 1 day a week for a maximum of 10 weeks. During their individual exposure measurement days the subjects reported to have spent an average of 89% of their time indoors. Particle phase elemental carbon, sulfate, and calcium personal exposure data were used in a mixed-effects model as tracers for outdoor PM2.5 from traffic-related combustion, regional, and local crustal materials, respectively. These three sources were found to contribute 13% +/- 10%, 17% +/- 16%, and 7% +/- 6% of PM2.5 exposures. The remaining fraction of the personal PM2.5 is hypothesized to be predominantly related to indoor sources. For comparison, central site outdoor PM2.5 measurements for the same dates as personal measurements were used to construct a receptor model using the same three tracers. In this case, traffic-related combustion, regional, and local crustal materials were found to contribute 19% +/- 17%, 52% +/- 22%, and 10% +/- 7%, respectively. Our results indicate that the three outdoor PM2.5 sources considered are statistically significant contributors to personal exposure to PM2.5. Our results also suggest that among the Toronto subjects, who spent a considerable amount of time indoors, exposure to outdoor PM2.5 includes a greater relative contribution from combustion sources compared with outdoor PM2.5 measurements where regional sources are the dominant contributor.     

Levels of lead, cadmium and other elements in mink and otter from Ontario, Canada

Concentrations of Pb, Cd, Cu, Ni, Fe, Zn, Mn, Ca, P, Mg and S were measured in tissues of mink (Mustela vision) and river otter (Lutra canadensis) from five areas of Ontario, Canada. Bone Pb levels in both species were lowest in animals from the collection site most remote from industrial activity and atmospheric deposition of pollutants. Mean liver and kidney Cd levels were also different between collection sites and may reflect natural and/or anthropogenic sources. Copper levels in liver, but not kidney, were elevated in mink and otter from the heavily Cu-contaminated Sudbury region. However, tissue levels did not reflect environmental loading of other metals, such as Fe, Ni and Zn, in the Sudbury area. This may be a function of effective homeostatic regulation in mammals, or low potential for biomagnification of these elements.     

The effects of tertiary treated municipal wastewater on fish communities of a small river tributary in Southern Ontario, Canada

Fish community changes associated with a tertiary treated municipal wastewater effluent outfall in the Speed River, Ontario, Canada, were evaluated at nine sites over two seasons (2008) using standardized electrofishing. Habitat evaluations were conducted to ensure that the riffle sites selected were physically similar. The fish community was dominated by several species of darters that differed in their response to the effluent outfall. There was a significant decrease in Greenside Darter (Etheostoma blennioides) but an increase in Rainbow Darter (E. caeruleum) abundance directly downstream of the outfall. Stable isotope signatures (δ¹³C and δ¹⁵N), which indicate shifts in energy utilization and flow, increased in Rainbow Darter downstream, but showed no change in Greenside Darter. Rainbow Darter may be exploiting a food source that is not as available at upstream sites giving them a competitive advantage over the Greenside Darter immediately downstream of the outfall.     

Correlates of mercury in fish from lakes near Clyde Forks, Ontario, Canada

Subsurface soils near Clyde Forks, Ontario, Canada, can have naturally high concentrations of mercury (Hg) from local geological sources. To investigate Hg in local aquatic food webs, Hg was measured in fish dorsal muscle (mainly yellow perch [YP] and pumpkinseed sunfish [PS]) and surface sediments from 10 regional lakes. Water chemistry, along with fork length, weight, and stable isotopes (delta15N, delta13C, delta34S) in fish were also measured. No lake sediments had elevated (>0.3microg/g dw) Hg, and average Hg concentrations in fish were not sufficiently high (<1microg/g dw) to be of concern for fish-eating wildlife. Variance in fish Hg was best explained by dietary carbon source (delta13C), and certain lake variables (e.g., pH for YP). PS with more pelagic feeding habits had higher delta34S and Hg than those with more littoral feeding habits. Potential biological linkages between fish Hg and delta34S, a parameter that may be related to the lake sulphate-reducing bacteria activity, requires further investigation.     

Recent atmospheric Pb deposition at a rural site in southern Germany assessed using a peat core and snowpack,and comparison with other archives

In a peat bog from Black Forest, Southern Germany, the rate of atmospheric Pb accumulation was quantified using a peat core dated by ²¹⁰Pb and ¹⁴C. The most recent Pb accumulation rate (2.5 mg m⁻² y⁻¹) is similar to that obtained from a snowpack on the bog surface, which was sampled during the winter 2002 (1 to 4 mg m⁻² y⁻¹). The Pb accumulation rates recorded by the peat during the last 25 yr are also in agreement with published values of direct atmospheric fluxes in Black Forest. These values are 50 to 200 times greater than the “natural” average background rate of atmospheric Pb accumulation (20 μg m⁻² y⁻¹) obtained using peat samples from the same bog dating from 3300 to 1300 cal. yr B.C. The isotopic composition of Pb was measured in both the modern and ancient peat samples as well as in the snow samples, and clearly shows that recent inputs are dominated by anthropogenic Pb. The chronology and isotopic composition of atmospheric Pb accumulation recorded by the peat from the Black Forest is similar to the chronologies reported earlier using peat cores from various peat bogs as well as herbarium samples of Sphagnum and point to a common Pb source to the region for the past 150 years. In contrast, Pb contamination occurring before 1850 in southwestern Germany, differs from the record published for Switzerland mainly due to the mining activity in Black Forest. Taken together, the results show that peat cores from ombrotrophic bogs can yield accurate records of atmospheric Pb deposition, provided that the cores are carefully collected, handled, prepared, and analysed using appropriate methods.