Determination of trace triazine and chloroacetamide herbicides in tile-fed drainage ditch water using solid-phase microextraction coupled with GC-MS

Solid-phase microextraction coupled with gas chromatography-mass spectrometry (SPME-GC-MS) was used to analyze two triazine (atrazine and simazine) and three chloroacetamide herbicides (acetochlor, alachlor, and metolachlor) in water samples from a midwest US agricultural drainage ditch for two growing seasons. The effects of salt concentration, sample volume, extraction time, and injection time on extraction efficiency using a 100-mum polydimethylsiloxane-coated fiber were investigated. By optimizing these parameters, ditch water detection limits of 0.5 microgL(-1) simazine and 0.25 microgL(-1) atrazine, acetochlor, alachlor, and metolachlor were achieved. The optimum salt concentration was found to be 83% NaCl, while sample volume (10 or 20 mL) negligibly affected analyte peak areas. The optimum extraction time was 40 min, and the optimum injection time was 15 min. Results indicated that atrazine levels in the ditch water exceeded the US maximum contaminant level for drinking water 12% of the time, and atrazine was the most frequently detected among studied analytes.     

Features of resilience

The National Academy of Sciences (NAS) definition of resilience is used here to organize common concepts and synthesize a set of key features of resilience that can be used across diverse application domains. The features in common include critical functions (services), thresholds, cross-scale (both space and time) interactions, and memory and adaptive management. We propose a framework for linking these features to the planning, absorbing, recovering, and adapting phases identified in the NAS definition. The proposed delineation of resilience can be important in understanding and communicating resilience concepts.     

Outdoor tobacco smoke exposure at the perimeter of a tobacco-free university

There are few studies measuring exposure to outdoor tobacco smoke (OTS). Tobacco users often gather at the boundaries of tobacco-free campuses, resulting in unintended consequences. The objective of this study was to measure exposure levels from OTS on sidewalks bordering a tobacco-free university campus. Data were collected while walking along a sidewalk adjacent to a medium traffic road between May and August 2011. Monitoring occurred during “background,” “stop,” and “walk-through” conditions at and near hot spot area to measure fine particulate matter (<2.5 μm; PM_2.5) from OTS using a portable aerosol monitor. The average PM_2.5 levels during stop and walk-through conditions were significantly higher than during background conditions. PM_2.5 peak occurrence rate and magnitude of peak concentration were significantly different depending on smoking occurrence. The peak occurrence rate during the stop condition was 10.4 times higher than during the background condition, and 3.1 times higher than during the walk-through condition. Average peak PM_2.5 concentrations during the stop condition were 48.7% higher than during the background condition. In conclusion, individuals could be exposed to high levels of PM_2.5 when stopping or even passing by smokers outdoors at the perimeter of tobacco-free campuses. The design and implementation of tobacco-free campus policies need to take into account the unintended consequences of OTS exposure at the boundaries.

Implications:In this study, outdoor tobacco smoke (OTS) exposure was measured at the perimeter of tobacco-free campus. OTS exposure could be determined by peak analysis. Peak occurrence rate and peak concentration for OTS exposure were identified by using peak analysis. People could be exposed to high levels of PM_2.5 when standing or even passing by smokers at the perimeter of tobacco-free campus. OTS exposure measurement in other outdoor locations with smokers is needed to support outdoor smoking regulation.     

Historic preservation,significance, and age value: A comparative phenomenology of historic Charleston and the nearby new-urbanist community of I'On

While the age of physical environments is the central tenet of historic preservation, there is a lack of empirical evidence about how everyday people actually value, perceive, and experience age as an intrinsic part of an urban environment. In order to ameliorate this knowledge deficit, this study employs phenomenology to understand the lived experience of being in a “new” versus an “old” or “historic” urban residential environment. The new environment is the I'On new urbanist development in Mt. Pleasant, South Carolina, and the old environment is the location of the United States' first historic district in Charleston, South Carolina. These locations are approximately within five miles of each other. In both places, the physical characteristics of the built environment are remarkably similar in density, form, layout, and design, but the age is dramatically different. Through photo elicitation techniques and interviews, the results of this study reveal that residents of historic Charleston and I'On value their built environments in remarkably similar ways. Surprisingly, elements that evoke a strong sense of attachment tend to be landscape features, such as gates, fountains, trees, and gardens rather than buildings. The informants valued the “mystery” that they felt was part of the landscape and which consisted of layered elements such as fences, gates, and paths, such that these features (including buildings) had to be “discovered.” Lastly, the informants strongly valued landscapes that showed “people care” through regular maintenance. The essential difference in people's experience and valuation of the new environment (I'On) and the old environment (historic Charleston) is in the older environment's ability to instill creative fantasies in the minds of the informants based on a hypothetical past of their own creation. The informants in I'On did not share these kinds of meanings.     

Plant and Soil Responses to High and Low Diversity Grassland Restoration Practices

The USDA’s Conservation Reserve Program (CRP) has predominantly used only a few species of dominant prairie grasses (CP2 practice) to reduce soil erosion, but recently has offered a higher diversity planting practice (CP25) to increase grassland habitat quality. We quantified plant community composition in CP25 and CP2 plantings restored for 4 or 8 years and compared belowground properties and processes among restorations and continuously cultivated soils in southeastern Nebraska, USA. Relative to cultivated soils, restoration increased soil microbial biomass (P = 0.033), specifically fungi (P < 0.001), and restored soils exhibited higher rates of carbon (C) mineralization (P = 0.010). High and low diversity plantings had equally diverse plant communities; however, CP25 plantings had greater frequency of cool-season (C₃) grasses (P = 0.007). Older (8 year) high diversity restorations contained lower microbial biomass (P = 0.026), arbuscular mycorrhizal fungi (AMF) biomass (P = 0.003), and C mineralization rates (P = 0.028) relative to 8 year low diversity restorations; older plantings had greater root biomass than 4 year plantings in all restorations (P = 0.001). Low diversity 8 year plantings contained wider root C:N ratios, and higher soil microbial biomass, microbial community richness, AMF biomass, and C mineralization rate relative to 4 year restorations (P < 0.050). Net N mineralization and nitrification rates were lower in 8 year than 4 year high diversity plantings (P = 0.005). We attributed changes in soil C and N pools and fluxes to increased AMF associated with C₄ grasses in low diversity plantings. Thus, reduced recovery of AMF in high diversity plantings restricted restoration of belowground microbial diversity and microbially-mediated soil processes over time.     

Hg Reactions in the Presence of Chlorine Species: Homogeneous Gas Phase and Heterogeneous Gas-Solid Phase

Abstract

The kinetics of Hg chlorination (with HCl) was studied using a flow reactor system with an online Hg analyzer, and speciation sampling using a set of impingers. Kinetic parameters, such as reaction order (α), overall rate constant (k′ ), and activation energy (E _a), were estimated based on the simple overall reaction pathway. The reaction order with respect to C _Hg, k′, and E _a were found to be 1.55, 5.07 x 10^-2exp(-1939.68/T) [(μg/m³)^-0.55(s)^-1], and 16.13 [kJ/mol], respectively. The effect of chlorine species (HCl, CH₂Cl₂) on the in situ Hg capture method previously de-veloped²⁸ was also investigated. The efficiency of capture of Hg by this in situ method was higher than 98% in the presence of chlorine species. Furthermore, under certain conditions, the presence of chlorine enhanced the removal of elemental Hg by additional gas-phase oxidation.     

Farmers’ market governance and its role on consumer motives and outcomes

Local food systems and farmers' markets across the USA have experienced unprecedented growth and development in the past 20 years. While scholarship has examined participant demographics and motives for engaging in farmers' markets, few studies have considered the coupled nature of those attending the markets with institutional governance systems used for market coordination. This study examined participation in farmers' markets under the framework of high and low market governance systems, specifically considering the demographics, values for local foods, motives for attending farmers' markets, and outcomes of the experience based on the dichotomous governance classification. Governance was characterized using four attributes: market rules or policies, paid employee(s), a rule governing geography of food origin, and affiliation with an organisation or agency. Our results suggest that market governance may impact (1) which consumers attend the market, (2) motives among those who attend the market, and (3) satisfaction outcome levels among market participants. By better understanding how the emerging governance system impacts who ultimately attends the market (and the outcomes of the experience), agencies coordinating farmers' markets and market managers can ultimately improve the market's reach and experience with greater intentionality.     

Just and Sustainable? Examining the Rhetoric and Potential Realities of UK Food Security

The dominant discourse in 20th century UK food and agricultural policies of a liberal, free trade agenda was modified at the turn of the 21st to embrace ecological sustainability and “food security.” The latter term has a long international history; the relationship between issues of technical production and equality of distributional access are also much debated. The paper examines shifts in UK policy discourse in the context of international research, policy, and initiatives to promote food security, and highlights the implications for social justice in and through the food system.     

Evaluating pollution-related damage and restoration success in urban forests with participatory monitoring and digital tools

Peri-urban forest monitoring requires indicators of vegetation damage. An example is the sacred fir (Abies religiosa) forests surrounding Mexico City, which have been heavily exposed to tropospheric ozone, a harmful pollutant, for over 4 decades. We developed a participatory monitoring system with which local community members and scientists generated data on ozone tree damage. Santa Rosa Xochiac rangers (13) used the digital tool KoboToolBox to record ozone damage to trees, tree height, tree ages, tree condition, tree position, and whether the tree had been planted. Thirty-five percent of the trees (n = 1765) had ozone damage. Younger trees had a lower percentage of foliage damaged by ozone than older trees (p < 0.0001), and asymptomatic trees tended to be younger (p < 0.0001). Symptomatic trees were taller than asymptomatic trees of the same age (R²_c = 0.43, R²_m = 0.27). Involving local communities facilitated forest monitoring and using digital technology improved data quality. This participatory system can be used to monitor forest condition change over time and thus aids restoration efforts driven by government or local communities’ interests, facilitating local decision-making.