Responses of herbaceous plants to urban air pollution: Effects on growth, phenology and leaf surface characteristics

Vehicle exhaust emissions are a dominant feature of urban environments and are widely believed to have detrimental effects on plants. The effects of diesel exhaust emissions on 12 herbaceous species were studied with respect to growth, flower development, leaf senescence and leaf surface wax characteristics. A diesel generator was used to produce concentrations of nitrogen oxides (NO_x) representative of urban conditions, in solardome chambers. Annual mean NO_x concentrations ranged from 77 nl l^−l to 98 nl l⁻¹, with NO:NO₂ ratios of 1.4-2.2, providing a good experimental simulation of polluted roadside environments. Pollutant exposure resulted in species-specific changes in growth and phenology, with a consistent trend for accelerated senescence and delayed flowering. Leaf surface characteristics were also affected; contact angle measurements indicated changes in surface wax structure following pollutant exposure. The study demonstrated clearly the potential for realistic levels of vehicle exhaust pollution to have direct adverse effects on urban vegetation.     

Occurrence and sources of polychlorinated dibenzo-p-dioxins, dibenzofurans and dioxin-like polychlorinated biphenyls in surficial sediments of Lakes Superior and Huron

Concentrations and congener profile patterns of 2378-substituted PCDD/Fs and DLPCBs in offshore, nearshore and tributary sediments of Lakes Superior and Huron are reported, and spatial trends and source contributions assessed. PCDD/F concentrations ranged from 5 to 18 000 pg/g dw (Lake Superior) and 3 to 6100 pg/g dw (Lake Huron); DLPCBs ranged from 9 to 11 000 pg/g dw (Lake Superior) and 9 to 27 000 pg/g dw (Lake Huron). Our analysis indicated atmospheric deposition is a primary source to depositional areas of both lakes; however, greater PCDD/F and DLPCB concentrations were observed at several nearshore and tributary sites, and were attributed to corresponding land use in the watershed. Statistical analysis and pattern comparison suggested that industrial inputs mainly associated with wood treatment plants, pulp and paper mills, mining operations, and chlorine-based chemical manufacturing also contributed to contamination by PCDD/Fs and DLPCBs in certain nearshore and offshore areas of Lakes Superior and Huron.     

Household wood heater usage and indoor leakage of BTEX in Launceston,Australia: A null result

A study has been conducted in Launceston, Australia, to determine within households with wood heaters the effect of leakage from the heater and flue on the indoor air concentrations of the pollutants: benzene, toluene, ethylbenzene and xylene (BTEX). The study involved three classes: 28 households without wood heaters, 19 households with wood heaters compliant with the relevant Australian Standard and 30 households with non-compliant wood heaters. Outdoor and indoor BTEX concentrations were measured in each household for 7 days during summer when there was little or no wood heater usage, and for 7 days during winter when there was widespread wood heater usage. Each participant kept a household activity diary throughout their sampling periods. For wintertime, there were no significant differences of the indoor BTEX concentrations between the three classes of households. Also there were no significant relationships between BTEX indoor concentrations within houses and several measures of the amount of wood heater use within these houses. For the households sampled in this study, the use of a wood heater within a house did not lead to BTEX release within that house and had no direct detectable influence on the concentrations of BTEX within the house. We propose that the pressure differences associated with the both the leakiness or permeability of the building envelope and the draught of the wood heater have key roles in determining whether there will be backflow of smoke from the wood heater into the house. For a leaky house with a well maintained wood heater there should be no backflow of smoke from the wood heater into the house. However backflow of smoke may occur in well sealed houses.The study also found that wood heater emissions raise the outdoor concentrations of BTEX in winter in Launceston and through the mixing of outdoor air through the building envelopes into the houses, these emissions contribute to increases in the indoor concentrations of BTEX in winter in all houses in Launceston.     

Fate and Transport Modeling of Potential Pathogens: The Contribution From Sediments1

Abstract: Escherichia coli was used as a bacterial tracer for the development, calibration, and validation of a watershed scale fate and transport model to be extended to a suite of reference pathogens (Cryptosporidium, Giardia, Campylobacter, E. coli O157:H7). E. coli densities in water and sediments from the Blackstone River Watershed, Massachusetts, were measured at three sites for a total of five wet weather events and three dry weather events covering three seasons. The confirmed E. coli strains were identified by ribotyping for tracking the sources of E. coli and for determining the association of downstream E. coli isolates with isolates from upstream sediments. A large number of downstream samples were associated with upstream sediment sources of E. coli. E. coli densities ranged from 71 to 6,401 MPN/100 ml in water samples and from 2 to 335 MPN/g in sediments. Pearson correlation analysis revealed significant correlations between E. coli and total coliforms in water (r = 0.777, p < 0.01) and sediments (r = 0.728, p < 0.01). In addition, E. coli concentrations in water were weakly correlated with sediment particle size and sediment concentrations (r = 0.298, p < 0.01). A hydrologic model, WATFLOOD/SPL9, was used to predict the temporal and spatial variation of E. coli in the Blackstone River. The rapid rise of stream E. coli densities was more accurately predicted by the model with the inclusion of sediment resuspension, thus demonstrating the importance of the process.     

Nitromusk compounds in San Francisco Bay sediments

Synthetic nitromusk fragrances are used in a wide variety of consumer products and can enter aquatic environments through wastewater effluent. Although nitromusks are known to be hydrophobic, little attention has been paid to their behavior in sediments. A sediment extraction method using sonication was developed and used to analyze samples from San Francisco Bay. Both musk xylene (MX) and musk ketone (MK) were found at low levels, with mean concentrations of 0.034 and 0.038ngg(-1), respectively. The highest concentrations were found in the southernmost region of the Bay. Samples were also analyzed from a nearby tidal channel fed by a wastewater treatment plant outfall. At this location both musk xylene and musk ketone were found at higher concentrations of 0.13-0.24ngg(-1) MX and 1.08-2.74ngg(-1) MK. A metabolite of musk xylene was also found at levels up to 4.08ngg(-1), suggesting that these metabolites may play an important role in the fate of nitromusk compounds. Concentrations of all three compounds were highest at the earliest of four sampling dates, and a geographic survey of sediments along the tidal channel showed that concentrations decreased rapidly with distance from the outfall and were close to background before the channel reached the Bay.     

Mass flux from a non-aqueous phase liquid pool considering spontaneous expansion of a discontinuous gas phase

The partitioning of non-aqueous phase liquid (NAPL) compounds to a discontinuous gas phase results in the repeated spontaneous expansion, snap-off, and vertical mobilization of the gas phase. This mechanism has the potential to significantly affect the mass transfer processes that control the dissolution of NAPL pools by increasing the vertical transport of NAPL mass and increasing the total mass transfer rate from the surface of the pool. The extent to which this mechanism affects mass transfer from a NAPL pool depends on the rate of expansion and the mass of NAPL compound in the gas phase. This study used well-controlled bench-scale experiments under no-flow conditions to quantify for the first time the expansion of a discontinuous gas phase in the presence of NAPL. Air bubbles placed in glass vials containing NAPL increased significantly in volume, from a radius of 1.0 mm to 2.0 mm over 215 days in the presence of tetrachloroethene (PCE), and from a radius of 1.2 mm to 2.3 mm over 22 days in the presence of trans-1,2-dichloroethene (tDCE). A one-dimensional mass transfer model, fit to the experimental data, showed that this expansion could result in a mass flux from the NAPL pool that was similar in magnitude to the mass flux expected for the dissolution of a NAPL pool in a two-fluid (NAPL and water) system. Conditions favouring the significant effect of a discontinuous gas phase on mass transfer were identified as groundwater velocities less than ~0.01 m/day, and a gas phase that covers greater than ~10% of the pool surface area and is located within ~0.01 m of the pool surface. Under these conditions the mass transfer via a discontinuous gas phase is expected to affect, for example, efforts to locate NAPL source zones using aqueous concentration data, and predict the lifetime and risk associated with NAPL source zones in a way that is not currently included in the common conceptual models used to assess NAPL-contaminated sites.     

Trace contamination with dioxin-like chemicals: evaluation of bioassay-based TEQ determination for hazard assessment and regulatory responses

Many recent dioxin contamination events have been traced back to poisoned animal feed or feed ingredients. Therefore, enforcement authorities placed limits on the levels of dioxins in food and feed or implemented strict monitoring and control programs. The levels in force are generally expressed as TEQ values, which inherently accepts the underlying hypothesis that the effects of dioxin-like chemicals are additive. TEQ determination involves either chemo-analysis, with high-resolution gas chromatography in combination with high-resolution mass spectroscopy, or bio-analysis. Bio-analytical methods, more particularly the reporter gene expression method CALUX, are advantageous due to their high throughput rate and low cost. Moreover, the CALUX methodology detects the overall dioxin-like toxicity, rather than the limited number of compounds investigated by chemo-analysis. Bioanalytical methods such as CALUX also differ from chemo-analysis in that the contribution of antagonistic as well as synergistic effects, which violate the additivity principle, can be detected. The application of bio-analytical methods can facilitate a broader assessment of public health risks by intensifying the current monitoring programs in terms of both sample numbers and types. Bio-analysis provides information on the total dioxin-like activity of the samples under study (hazard assessment); however, chemo-analysis is still needed to identify the predominant contaminants (congener identification) for risk management.     

Quantification of biotransformation of chlorinated hydrocarbons in a biostimulation study: added value via stable carbon isotope analysis

Stable carbon isotope analysis of chlorinated aliphatic compounds was performed at an in situ biostimulation pilot test area (PTA) at a site where 1,2-dichloroethane (1,2-DCA) and trichloroethene (TCE) were present in groundwater. Chlorinated products of TCE reductive dechlorination (cis-dichloroethene (cDCE) and vinyl chloride (VC)) were present at concentrations of 17.5 to 126.4 micromol/L. Ethene, a potential degradation product of both 1,2-DCA dihaloelimination and TCE reductive dechlorination was also present in the PTA. Emulsified soybean oil and lactate were added as electron donors to stimulate anaerobic dechlorination in the PTA. Stable carbon isotope analysis provided evidence that dechlorination was occurring in the PTA during biostimulation, and a means of monitoring changes in dechlorination efficiency over the 183 day monitoring period. Stable carbon isotope analysis was also used to determine if ethene production in the PTA was due to dechlorination of TCE, 1,2-DCA, or both. Fractionation factors (alpha) were determined in the laboratory during anaerobic biotransformation of 1,2-DCA via a dihaloelimination reaction in four separate enrichment cultures. These alpha values (as well as the previously published ranges of alpha for the dechlorination of TCE, cDCE and 1,2-DCA) were used, along with isotopic values measured during the pilot test, to derive quantitative estimates of biotransformation during the pilot test. Dechlorination was found to account for 10.7 to 35.9%, 21.9 to 74.9%, and 54.4 to 67.8% of 1,2-DCA, TCE and cDCE concentration loss respectively in the PTA. Stable carbon isotope analysis indicates that dechlorination of 1,2-DCA, TCE and cDCE were all significant processes during the pilot test, while ethene production during the pilot test was dominated by 1,2-DCA dihaloelimination. This study demonstrates how stable carbon isotope analysis can provide more conservative estimates of the extent of biotransformation than do conventional protocols. In addition, in a complex mixed plume such as this, compound specific isotope analysis is shown to be one of the few methods available for clarifying dominant biotransformation pathways where breakdown products are non-exclusive (i.e. ethene).     

Impaired terrestrial and arboreal locomotor performance in the western fence lizard (Sceloporus occidentalis) after exposure to an AChE-inhibiting pesticide

We examined the effects of a commonly used AChE-inhibiting pesticide on terrestrial and arboreal sprint performance, important traits for predator avoidance and prey capture, in the western fence lizard (Sceloporus occidentalis). Lizards were exposed to carbaryl (2.5, 25, and 250 microg/g) and were raced before and 4, 24, and 96 h after dosing. In the terrestrial setting, exposure to low concentrations of carbaryl had stimulatory effects on performance, but exposure to the highest concentration was inhibitory. No stimulatory effects of carbaryl were noted in the arboreal environment and performance in lizards was reduced after exposure to both the medium and highest dose of carbaryl. Our findings suggest that acute exposure to high concentrations of carbaryl can have important sublethal consequences on fitness-related traits in reptiles and that arboreal locomotor performance is a more sensitive indicator of AChE-inhibiting pesticide poisoning than terrestrial locomotor performance.     

Combining Accuracy Assessment of Land-Cover Maps with Environmental Monitoring Programs

A scientifically valid accuracy assessment of a large-area, land-cover map is expensive. Environmental monitoring programs offer a potential source of data to partially defray the cost of accuracy assessment while still maintaining the statistical validity. In this article, three general strategies for combining accuracy assessment and environmental monitoring protocols are described. These strategies range from a fully integrated accuracy assessment and environmental monitoring protocol, to one in which the protocols operate nearly independently. For all three strategies, features critical to using monitoring data for accuracy assessment include compatibility of the land-cover classification schemes, precisely co-registered sample data, and spatial and temporal compatibility of the map and reference data. Two monitoring programs, the National Resources Inventory (NRI) and the Forest Inventory and Monitoring (FIM), are used to illustrate important features for implementing a combined protocol.