Fecal indicator bacteria (FIB) levels during dry weather from Southern California reference streams

High levels of fecal indicator bacteria (FIB) in surface waters is a common problem in urban areas that often leads to impairment of beneficial uses such as swimming. Once impaired, common management and regulatory solutions include development of total maximum daily loads (TMDLs) and other water quality management plans. A critical element of these plans is establishment of a "reference" level of exceedances against which to assess management goals and TMDL compliance. The goal of this study was to provide information on indicator bacteria contributions from natural streams in undeveloped catchments throughout southern California during dry weather, non-storm conditions. To help establish a regional reference data set, bacteria levels [i.e. Escherichia coli (E. coli), enterococci and total coliforms] were measured from 15 unimpaired streams in 11 southern California watersheds weekly for one full year. Concentrations measured from reference areas were typically between one to two orders of magnitude lower than levels found in developed watersheds. Nearly 82% of the time, samples did not exceed daily and monthly bacterial indicator thresholds. E. coli had the lowest daily percent exceedance (1.5%). A total of 13.7% of enterococci exceeded daily thresholds. Indicator bacteria levels fluctuated seasonally with an average of 79% of both enterococci and total coliforms exceedances occurring during summer months (June to August). Temperature, at all sites, explained about one-half the variation in total coliforms density suggesting that stream temperatures regulated bacterial populations. Accounting for natural background levels will allow for management targets that are more reflective of the contributions from natural sources.     

Distribution of sulfamethazine, chlortetracycline and tylosin in manure and soil of Canadian feedlots after subtherapeutic use in cattle

Feedlots are potential point sources for the flow of antibiotics into the environment due to common use of antibiotics such as sulfamethazine, chlortetracycline and tylosin. Hence soils and manures originating from a grassland control, an experimental and a commercial feedlot were analyzed and mass balances were calculated for these antibiotics. Up to 9990 μg kg⁻¹ sulfamethazine and 401 μg kg⁻¹ chlortetracycline on a dry matter basis were determined in feedlot manure. Soil concentrations were two orders of magnitude smaller. This corresponds to 7-40% of the calculated residual amount. In the commercial feedlot chlortetracycline was found down to soil depths of −40 cm; sulfamethazine was still detectable 1 year after medication. Sulfamethazine and chlortetracycline were additionally determined in manure of a control treatment in the experimental feedlot where cattle never received antibiotics. This was attributed to runoff from upslope pens. Consequently, antibiotics partially persist within feedlots and may be dislocated into the surrounding environment by vertical transport and runoff.     

Integrated approach to PCE‐impacted site characterization,site management,and enhanced bioremediation

Tetrachloroethene (PCE)‐ and trichloroethene (TCE)‐impacted sites pose significant challenges even when site characterization activities indicate that biodegradation has occurred naturally. Although site‐specific, regulatory, and economic factors play roles in the remedy‐selection process, the application of molecular biological tools to the bioremediation field has streamlined the assessment of remedial alternatives and allowed for detailed evaluation of the chosen remedial technology. The case study described here was performed at a PCE‐impacted site at which reductive dechlorination of PCE and TCE had led to accumulation of cis‐dichlorethene (cis‐DCE) with concentrations ranging from approximately 10 to 100 mg/L. Bio‐Trap® samplers and quantitative polymerase chain reaction (qPCR) enumeration of Dehalococcoides spp. were used to evaluate three remedial options: monitored natural attenuation, biostimulation with HRC®, and biostimulation with HRC‐S®. Dehalococcoides populations in HRC‐S‐amended Bio‐Traps deployed in impacted wells were on the order of 10³ to 10⁴ cells/bead but were below detection limits in most unamended and HRC‐amended Bio‐Traps. Thus the in situ Bio‐Trap study identified biostimulation with HRC‐S as the recommended approach, which was further evaluated with a pilot study. After the pilot HRC‐S injection, Dehalococcoides populations increased to 10⁶ to 10⁷ cells/bead, and concentrations of cis‐DCE and vinyl chloride decreased with concurrent ethene production. Based on these results, a full‐scale HRC‐S injection was designed and implemented at the site. As with the pilot study, full‐scale HRC‐S injection promoted growth of Dehalococcoides spp. and stimulated reductive dechlorination of the daughter products cis‐DCE and vinyl chloride. © 2008 Wiley Periodicals, Inc.     

The politics of risk in the Philippines: comparing state and NGO perceptions of disaster management

It is now generally appreciated that what constitutes vulnerability to one person is not necessarily perceived as such by the next. Different actors 'see' disasters as different types of events and as a result they prepare for, manage and record them in very different ways. This paper explores what different perceptions of vulnerability mean in terms of the understanding and practices of two significant sets of actors and stakeholders involved in disaster preparedness and management in the Philippines: the state and NGOs. Approaches to disaster are not just a function of people's perceptions of disaster risk but also of their understanding of the prevailing social order and social relations. Despite a shared vocabulary—which increasingly presents disasters as processes rather than events, takes a proactive rather than a reactive approach, and favours the inclusion of stakeholders rather than solely relying on technocratic management—different realities continue to make for different responses.     

Roles of SO2 oxidation in new particle formation events

The oxidation of SO₂ is commonly regarded as a major driver for new particle formation (NPF) in the atmosphere. In this study, we explored the connection between measured mixing ratio of SO₂ and observed long-term (duration > 3 hr) and short-term (duration < 1.5 hr) NPF events at a semi-urban site in Toronto. Apparent NPF rates (J₃₀) showed a moderate correlation with the concentration of sulfuric acid ([H₂SO₄]) calculated from the measured mixing ratio of SO₂ in long-term NPF events and some short-term NPF events (Category I) (R² = 0.66). The exponent in the fitting line of J₃₀ ~ [H₂SO₄]ⁿ in these events was 1.6. It was also found that SO₂ mixing ratios varied a lot during long-term NPF events, leading to a significant variation of new particle counts. In the SO₂-unexplained short-term NPF events (Category II), analysis showed that new particles were formed aloft and then mixed down to the ground level. Further calculation results showed that sulfuric acid oxidized from SO₂ probably made a negligible contribution to the growth of > 10 nm new particles.     

Automobile injury trends in the contemporary fleet: Belted occupants in frontal collisions

Objective: As vehicle safety technologies and evaluation procedures advance, it is pertinent to periodically evaluate injury trends to identify continuing and emerging priorities for intervention. This study examined detailed injury distributions and injury risk trends in belted occupants in frontal automobile collisions (10 o’clock to 2 o’clock) using NASS-CDS (1998–2015).

Methods: Injury distributions were examined by occupant age and vehicle model year (stratified at pre- and post-2009). Logistic regression models were developed to examine the effects of various factors on injury risk (by body region), controlling for delta-V, sex, age, height, body mass index (BMI), vehicle model year (again stratified at 2009).

Results: Among other observations, these analyses indicate that newer model year vehicles (model year [MY] 2009 and later) carry less risk of Abbreviated Injury Scale (AIS) 2+ and AIS 3+ injury compared to older model year vehicles, with odds ratios of 0.69 (AIS 2+) and 0.45 (AIS 3+). The largest reductions in risk between newer model year vehicles and older model year vehicles occur in the lower extremities and in the risk of skull fracture. There is no statistically significant change in risk of AIS 3+ rib fracture or sternum injury between model year categories. Females are at greater risk of AIS 2+ and AIS 3+ injury compared to males, with increased risk across most injury types.

Conclusions: For belted occupants in frontal collisions, substantial reductions in injury risk have been realized in many body regions in recent years. Risk reduction in the thorax has lagged other body regions, resulting in increasing prevalence among skeletal injuries in newer model year vehicles (especially in the elderly). Injuries also remain common in the arm and hand/wrist for all age ranges studied. These results provide insight into where advances in the field have made gains in occupant protection and what injury types remain to be addressed.     

Using spatially explicit,time-dependent analysis to understand how social factors influence conservation outcomes

Conservation across human-dominated landscapes requires an understanding of the social and ecological factors driving outcomes. Studies that link conservation outcomes to social and ecological factors have examined temporally static patterns. However, there may be different social and ecological processes driving increases and decreases in conservation outcomes that can only be revealed through temporal analyses. Through a case study of the invasion of Falcataria moluccana in Hawaii, we examined the association of social factors with increases and decreases in invader distributions over time and space. Over 7 years, rates of invader decrease varied substantially (66–100%) relative to social factors, such as building value, whether land was privately or publically owned, and primary residence by a homeowner, whereas rates of increase varied only slightly (<0.1–3.6%) relative to such factors. These findings suggest that links between social factors and invasion in the study system may be driven more by landowners controlling existing invasive species, rather than by landowners preventing the spread of invasive species. We suggest that spatially explicit, time-dependent analyses provide a more nuanced understanding of the way social factors influence conservation outcomes. Such an understanding can help managers develop outreach programs and policies targeted at different types of landowners in human-dominated landscapes.     

Dissecting the spatial scales of mercury accumulation in Ontario lake sediment

Total mercury concentration was analyzed in 171 lakes from pre-industrial (>30 cm depth; Hg_{pre-industrial}) and present-day sediments (0.5–1 cm; Hg_present-day). Numerous hot or cold spots of sediment mercury enrichment (Hg EF; Hg_{pre-industrial}/Hg_present-day) were evident as determined by local tests of autocorrelation, although in most cases, the maximum correlation among sites was not the nearest neighbor, indicating a strong influence of watershed characteristics. Hg EF was correlated with the area of open water (ha) (r = 0.91, p = 0.035), mine tailings (r = 0.94, p = 0.019), and organic deposits in surficial geology of the watershed (r = −0.91, p = 0.034). Through use of local rather than global regression coefficients, R² increased from 0.20 (p = 0.005) to 0.60 (p = 0.013). A broad spatial pattern (>500 km) observed only in Hg_{pre-industrial} was best explained by mean annual precipitation (shared variance = 3.5%), while finer spatial patterns only observed in Hg_present-day and Hg EF were best explained by pH (average shared variance = 10.8%).