Prediction of microbial accessibility of carbon-14-phenanthrene in soil in the presence of pyrene or benzo[a]pyrene using an aqueous cyclodextrin extraction technique

Traditionally, solvent extractions are routinely used in the assessment of contaminated land. However, vigorous solvent extractions only give total concentrations rather than that relating to the bioaccessible fraction. Recently, less harsh, aqueous-based extraction methods have been shown to be a better estimate of the microbial degradation of polycyclic aromatic hydrocarbons (PAHs). The aqueous-based hydroxypropyl-beta-cyclodextrin (HPCD) extraction technique was tested using 14C-PAHs in soils and compared against indigenous microbial mineralization (a measure of bioaccessibility) of 14C-phenanthrene in the presence of pyrene or benzo[a]pyrene (B[a]P) over a range of concentrations (0, 5, 10, or 50 mg kg(-1)) and aged for 0, 25, 50, and 100 d in four soils. At each time point, the total loss, extractability, and mineralization of 14C-phenanthrene was measured in each of the soils. The presence of the other PAHs had little effect on the behavior of 14C-phenanthrene in any of the soils. Comparisons between the amounts of 14C-phenanthrene extracted using HPCD and mineralized were made and showed that there was a correlation (1:1). This study demonstrates that HPCD extraction is able to predict the microbial accessibility fraction of 14C-phenanthrene in the presence of other PAHs in a range of soils, further supporting the applicability of this technique.     

Community Capacity for Adaptation to Climate-Induced Water Shortages: Linking Institutional Complexity and Local Actors

There is growing concern for the capacity of urban and rural communities to manage current water shortages and to prepare for shortages that may accompany predicted changes in climate. In this paper, concepts relating to the notion of climate adaptation and particularly capacity building are used to elucidate several determinants of community-level capacity for water management. These concepts and criteria are then used to interpret empirically derived insights relating to local management of water shortages in Ontario, Canada. General determinants of water-related community capacity relate to upper tier political and institutional arrangements; the characteristics of, and relationships among, pertinent agencies, groups, or individuals involved in water management; and the adequacy of financial, human, information, and technical resources. The case analysis illustrates how general factors play out in local experience. The findings point to geographically specific factors that influence the effectiveness of management. Key factors include collaboration between water managers, clarification of agency roles and responsibilities, integration of water management and land-use planning, and recognition and participation of both urban and rural stakeholders, whose sensitivities to water shortages are spatially and temporally variable.     

Groundwater management by watershed agencies: an evaluation of the capacity of Ontario's conservation authorities

Watershed-based resource management organizations around the world are becoming more involved in groundwater management. This reflects, among other considerations, growing awareness of the critical role that these local agencies can and should play in the management of groundwater resources. Ontario's conservation authorities (CAs) are an important example. CAs are taking on new responsibilities for groundwater data collection, monitoring and planning. Unfortunately, not all local organizations are equally capable of participating effectively in groundwater management. This certainly is the case among Ontario's 38 CAs, which have highly variable levels of financial and staff resources. Local capacity for water management can be explored from the perspective of the institutional environment, the watershed community, and the financial, technical and staff resources of the organizations. This paper presents an evaluation of the groundwater management capacity of Ontario's conservation authorities, drawing on two detailed case studies (the Upper Thames River CA and the Ganaraska Region CA), and additional data gathered from all 38 CAs. Institutional issues, such as the clarity of management roles and senior government commitment to local management, as well as resourcing concerns, local working relationships, and public support, largely determine the capacity of CAs to expand their involvement in groundwater management. Strengthening the capacity of watershed-based agencies to participate in groundwater management is an important challenge in all jurisdictions, as these agencies are well placed to reinforce municipal groundwater management by identifying local needs and trends, facilitating communication and cooperation, and promoting best management practices.     

Human Culture and Large Carnivore Conservation in North America

We examined and compared human attitudes toward wolves ( Canis lupus ), grizzly bears ( Ursus arctos horribilis ), and mountain lions ( Puma concolor ) in North America, with an emphasis on the Rocky Mountains of the United States and Canada. Primary research, literature review, and secondary data were included in the analysis. Wolves were historically persecuted by Euro-American settlers, but they have been the focus of a significant attitudinal transformation during the latter half of this century. Many now view the wolf in positive and protective ways. Considerable variation remains, however, in contemporary attitudes. Attitudes toward mountain lions have been highly ambivalent, never assuming the prominence or clarity of views on wolves. The behavior and physiology of the species, along with human psychological factors, are important reasons for the difference in human perceptions of wolves and mountain lions. We also examined attitudes toward grizzly bears. Many indigenous cultures revered grizzly bears, although European settlers were interested in exploiting and eliminating them. Today, perceptions of grizzly bears range from positive to negative. Our recommendations include targeting key groups with education programs, building support through the use of spokespeople within the target groups, integrating human and ecological concerns, and designing species-specific education initiatives in some cases.     

Near-field loading dynamics of total phosphorus and short-term water quality variations at a rainbow trout cage farm in Lake Huron

Aquatic total phosphorus (Tot-P) is measured at fish-cages in Lake Huron for environmental regulatory compliance. An improved understanding of how Tot-P is manifested in the near-field (相似文献   

Experimental investigation of wellbore integrity and CO2–brine flow along the casing–cement microannulus

Wellbore integrity is one of the key performance criteria in the geological storage of CO₂. It is significant in any proposed storage site but may be critical to the suitability of depleted oil and gas reservoirs that may have 10’s to 1000’s of abandoned wells. Much previous work has focused on Portland cement which is the primary material used to seal wellbore systems. This work has emphasized the potential dissolution of Portland cement. However, an increasing number of field studies (e.g., Carey et al., 2007), experimental studies (e.g., Kutchko et al., 2006) and theoretical considerations indicate that the most significant leakage mechanism is likely to be flow of CO₂ along the casing–cement microannulus, cement–cement fractures, or the cement–caprock interface.In this study, we investigate the casing–cement microannulus through core-flood experiments. The experiments were conducted on a synthetic wellbore system consisting of a 5-cm diameter sample of cement that was cured with an embedded rectangular length of steel casing that had grooves to accommodate fluid flow. The experiments were conducted at 40 $°$ C and 14 MPa pore pressure for 394 h. During the experiment, 6.2 l of a 50:50 mixture of supercritical CO₂ and 30,000 ppm NaCl-rich brine flowed through 10-cm of limestone before flowing through the 6-cm length cement–casing wellbore system. Approximately 59,000 pore volumes of fluid moved through the casing–cement grooves. Scanning electron microscopy revealed that the CO₂–brine mixture impacted both the casing and the cement. The Portland cement was carbonated to depths of 50–250 $\mu$m by a diffusion-dominated process. There was very little evidence for mass loss or erosion of the Portland cement. By contrast, the steel casing reacted to form abundant precipitates of mixed calcium and iron carbonate that lined the channels and in one case almost completely filled a channel. The depth of steel corroded was estimated at 25– $30\mu$m and was similar in value to results obtained with a simplified corrosion model.The experimental results were applied to field observations of carbonated wellbore cement by Carey et al. (2007) and Crow et al. (2009) to show that carbonation of the field samples was not accompanied by significant CO₂–brine flow at the casing–cement interface. The sensitivity of standard-grade steel casing to corrosion suggests that relatively straight-forward wireline logging of external casing corrosion could be used as a useful indicator of flow behind casing. These experiments also reinforce other studies that indicate rates of Portland cement deterioration are slow, even in the high-flux CO₂–brine experiments reported here.     

Speciated arsenic in air: measurement methodology and risk assessment considerations

Accurate measurement of arsenic (As) in air is critical to providing a more robust understanding of arsenic exposures and associated human health risks. Although there is extensive information available on total arsenic in air, less is known on the relative contribution of each arsenic species. To address this data gap, the authors conducted an in-depth review of available information on speciated arsenic in air. The evaluation included the type of species measured and the relative abundance, as well as an analysis of the limitations of current analytical methods. Despite inherent differences in the procedures, most techniques effectively separated arsenic species in the air samples. Common analytical techniques such as inductively coupled plasma mass spectrometry (ICP-MS) and/or hydride generation (HG)- or quartz furnace (GF)-atomic absorption spectrometry (AAS) were used for arsenic measurement in the extracts, and provided some of the most sensitive detection limits. The current analysis demonstrated that, despite limited comparability among studies due to differences in seasonal factors, study duration, sample collection methods, and analytical methods, research conducted to date is adequate to show that arsenic in air is mainly in the inorganic form. Reported average concentrations of As(III) and As(V) ranged up to 7.4 and 10.4 ng/m3, respectively, with As(V) being more prevalent than As(III) in most studies. Concentrations of the organic methylated arsenic compounds are negligible (in the pg/m3 range). However because of the variability in study methods and measurement methodology, the authors were unable to determine the variation in arsenic composition as a function of source or particulate matter (PM) fraction. In this work, the authors include the implications of arsenic speciation in air on potential exposure and risks. The authors conclude that it is important to synchronize sample collection, preparation, and analytical techniques in order to generate data more useful for arsenic inhalation risk assessment, and a more robust documentation of quality assurance/quality control (QA/QC) protocols is necessary to ensure accuracy, precision, representativeness, and comparability.     

Regional source identification using Lagrangian stochastic particle dispersion and HYSPLIT backward-trajectory models

The main objective of this study was to investigate the capabilities of the receptor-oriented inverse mode Lagrangian Stochastic Particle Dispersion Model (LSPDM) with the 12-km resolution Mesoscale Model 5 (MM5) wind field input for the assessment of source identification from seven regions impacting two receptors located in the eastern United States. The LSPDM analysis was compared with a standard version of the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) single-particle backward-trajectory analysis using inputs from MM5 and the Eta Data Assimilation System (EDAS) with horizontal grid resolutions of 12 and 80 km, respectively. The analysis included four 7-day summertime events in 2002; residence times in the modeling domain were computed from the inverse LSPDM runs and HYPSLIT-simulated backward trajectories started from receptor-source heights of 100, 500, 1000, 1500, and 3000 m. Statistics were derived using normalized values of LSPDM- and HYSPLIT-predicted residence times versus Community Multiscale Air Quality model-predicted sulfate concentrations used as baseline information. From 40 cases considered, the LSPDM identified first- and second-ranked emission region influences in 37 cases, whereas HYSPLIT-MM5 (HYSPLIT-EDAS) identified the sources in 21 (16) cases. The LSPDM produced a higher overall correlation coefficient (0.89) compared with HYSPLIT (0.55-0.62). The improvement of using the LSPDM is also seen in the overall normalized root mean square error values of 0.17 for LSPDM compared with 0.30-0.32 for HYSPLIT. The HYSPLIT backward trajectories generally tend to underestimate near-receptor sources because of a lack of stochastic dispersion of the backward trajectories and to overestimate distant sources because of a lack of treatment of dispersion. Additionally, the HYSPLIT backward trajectories showed a lack of consistency in the results obtained from different single vertical levels for starting the backward trajectories. To alleviate problems due to selection of a backward-trajectory starting level within a large complex set of 3-dimensional winds, turbulence, and dispersion, results were averaged from all heights, which yielded uniform improvement against all individual cases.     

Compatibility of hydroxypropyl-beta-cyclodextrin with algal toxicity bioassays

Numerous reports have indicated that hydrophobic organic compound bioaccessibility in sediment and soil can be determined by extraction using aqueous hydroxypropyl-β-cyclodextrin (HPCD) solutions. This study establishes the compatibility of HPCD with Selenastrum capricornutum and assesses whether its presence influences the toxicity of reference toxicants. Algal growth inhibition (72 h) showed no significant (P > 0.05) difference at HPCD concentrations up to and including 20 mM. HPCD presence did not influence the toxicity of the inorganic reference toxicant (ZnSO₄), with IC50 values of 0.82 μM and 0.85 μM, in the presence and absence of HPCD (20 mM), respectively. However, HPCD presence (20 mM) reduced the toxicity of 2,4-dichlorophenol and the herbicides diuron and isoproturon. These reductions were attributed to inclusion complex formation between the toxicants and the HPCD cavity. Liberation of complexed toxicants, by sample manipulation prior to toxicity assessment, is proposed to provide a sensitive, high throughput, bioassay that reflects compound bioaccessibility.