Sensitivity of a molecular marker based positive matrix factorization model to the number of receptor observations

To investigate the impact of the number of observations on molecular marker-based positive matrix factorization (MM-PMF) source apportionment models, daily PM_2.5 samples were collected in East St. Louis, IL, from April 2002 through May 2003. The samples were analyzed for daily 24-h average concentrations of elemental and organic carbon, trace elements, and speciated particle-phase organic compounds. A total of 273 sets of observations were used in the model and consisted of all valid sets of observations from the year long data set minus one sixth of the measurements, which were collected every 6th day and were analyzed by different chemical analysis techniques. In addition to the base case of 273 samples, systematic subsets of the data set were analyzed by PMF. These subsets of data included 50% of the observations (135–138 days), 33% of the observations (90–92 days) and 20% of the observations (52–56 days). In addition, model runs were also examined that used 48-h, 72-h, 6-day, and weekly average concentrations as model inputs. All MM-PMF model runs were processed following the same procedures to explore the stability of the source attribution results. Consistent with previous MM-PMF results for East St. Louis, the main sources of organic aerosol were found to be mobile sources, secondary organic aerosols (SOAs), resuspended soil and biomass combustions, as well as an n-alkane dominated point source and other combustion sources. The MM-PMF model was reasonably stable when the number of observations in the input was reduced to ninety, or approximately 33% of observations present in the base case. In these cases, the key factors including resuspended soil, mobile and secondary factors, which accounted for more than 70% of the measured OC concentrations, were stable as defined by a relative standard deviation (RSD) of less than 30%. Similar results were obtained from the smaller data subsets, but resulted in larger uncertainties, with several of these factors yielding RSD of greater than 30%. The three factors with the largest OC contributions were more stable than the other minor factors, even when the number of observations was nominally 50 days. Secondary organic aerosol (SOA) was the most stable factor observed in the model runs. Since it is unclear if these results can be broadly applied to all MM-PMF models, additional studies of this nature are needed to assess the broader applicability of these conclusions. Until such studies are implemented, this paper provides a foundation to design future studies in sampling strategies for source apportionment using MM-PMF.     

Source apportionment of primary and secondary organic aerosols using positive matrix factorization (PMF) of molecular markers

Monthly average ambient concentrations of more than eighty particle-phase organic compounds, as well as total organic carbon (OC) and elemental carbon (EC), were measured from March 2004 through February 2005 in five cities in the Midwestern United States. A multi-variant source apportionment receptor model, positive matrix factorization (PMF), was applied to explore the average source contributions to the five sampling sites using molecular markers for primary and secondary organic aerosols (POA, SOA). Using the molecular makers in the model, POA and SOA were estimated for each month at each site. Three POA factors were derived, which were dominated by primary molecular markers such as EC, hopanes, steranes, and polycyclic aromatic hydrocarbons (PAHs), and which represented the following POA sources: urban primary sources, mobile sources, and other combustion sources. The three POA sources accounted for 57% of total average ambient OC. Three factors, characterized by the presence of reaction products of isoprene, α-pinene and β-caryophyllene, and displaying distinct seasonal trends, were consistent with the characteristics of SOA. The SOA factors made up 43% of the total average measured OC. The PMF-derived results are in good agreement with estimated SOA concentrations obtained from SOA to tracer yield estimates obtained from smog chamber experiments. A linear regression comparing the smog chamber yield estimates and the PMF SOA contributions had a regression slope of 1.01 ± 0.07 and an intercept of 0.19 ± 0.10 μg OC m^?3 (adjusted R² of 0.763, n = 58).     

Pollinators,pests, and predators: Recognizing ecological trade-offs in agroecosystems

Ecological interactions between crops and wild animals frequently result in increases or declines in crop yield. Yet, positive and negative interactions have mostly been treated independently, owing partly to disciplinary silos in ecological and agricultural sciences. We advocate a new integrated research paradigm that explicitly recognizes cost-benefit trade-offs among animal activities and acknowledges that these activities occur within social-ecological contexts. Support for this paradigm is presented in an evidence-based conceptual model structured around five evidence statements highlighting emerging trends applicable to sustainable agriculture. The full range of benefits and costs associated with animal activities in agroecosystems cannot be quantified by focusing on single species groups, crops, or systems. Management of productive agroecosystems should sustain cycles of ecological interactions between crops and wild animals, not isolate these cycles from the system. Advancing this paradigm will therefore require integrated studies that determine net returns of animal activity in agroecosystems.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-015-0696-y) contains supplementary material, which is available to authorized users.     

Arsenic in North Carolina: public health implications

Arsenic is a known human carcinogen and relevant environmental contaminant in drinking water systems. We set out to comprehensively examine statewide arsenic trends and identify areas of public health concern. Specifically, arsenic trends in North Carolina private wells were evaluated over an eleven-year period using the North Carolina Department of Health and Human Services database for private domestic well waters. We geocoded over 63,000 domestic well measurements by applying a novel geocoding algorithm and error validation scheme. Arsenic measurements and geographical coordinates for database entries were mapped using Geographic Information System techniques. Furthermore, we employed a Bayesian Maximum Entropy (BME) geostatistical framework, which accounts for geocoding error to better estimate arsenic values across the state and identify trends for unmonitored locations. Of the approximately 63,000 monitored wells, 7712 showed detectable arsenic concentrations that ranged between 1 and 806 μg/L. Additionally, 1436 well samples exceeded the EPA drinking water standard. We reveal counties of concern and demonstrate a historical pattern of elevated arsenic in some counties, particularly those located along the Carolina terrane (Carolina slate belt). We analyzed these data in the context of populations using private well water and identify counties for targeted monitoring, such as Stanly and Union Counties. By spatiotemporally mapping these data, our BME estimate revealed arsenic trends at unmonitored locations within counties and better predicted well concentrations when compared to the classical kriging method. This study reveals relevant information on the location of arsenic-contaminated private domestic wells in North Carolina and indicates potential areas at increased risk for adverse health outcomes.     

Biochar produced from anaerobically digested fiber reduces phosphorus in dairy lagoons

This study evaluated the use of biochar produced from anaerobic digester dairy fiber (ADF) to sequester phosphorus (P) from dairy lagoons. The ADF was collected from a plugged flow digester, air-dried to <8% water content, and pelletized. Biochar was produced by slow pyrolysis in a barrel retort. The potential of biochar to reduce P in the anaerobic digester effluent (ADE) was assessed in small-scale filter systems through which the effluent was circulated. Biochar sequestered an average of 381 mg L P from the ADE, and 4 g L ADF was captured as a coating on the biochar. There was an increase of total (1.9 g kg), Olsen (763 mg kg), and water-extractable P (914 mg kg) bound to the biochar after 15 d of filtration. This accounted for a recovery of 32% of the P in the ADE. The recovered P on the biochar was analyzed using P nuclear magnetic resonance for P speciation, which confirmed the recovery of inorganic orthophosphate after liquid extraction of the biochar and the presence of inextractable Ca-P in the solid state. The inorganic phosphate was sequestered on the biochar through physical and weak chemical bonding. Results indicate that biochar could be a beneficial component to P reduction in the dairy system.     

The view from below: ‘lock-in’ and local procurement in the African gold mining sector

Through linkage creation, commodity extraction has the capacity to support local industrial production and capabilities building. Drawing on the experience of supplying inputs into the East African gold mining industry, this paper examines the constraints experienced by local suppliers arising from the purchasing procedures of large mining corporations and specialist construction companies contracted to construct these mines. Lead firms become locked-in to particular ways of working which minimise the opportunities that local suppliers have in providing products and services. After reviewing the situation for local mining suppliers in East Africa, the paper examines ways in which lead firms, the suppliers themselves and others (governments and industry associations) can better support local supplier involvement.     

Evaluating the Performance of Volunteers in Mapping Invasive Plants in Public Conservation Lands

Citizen science programs are touted as useful tools for engaging the public in science and for collecting important data for scientists and resource managers. To accomplish the latter, it must be shown that data collected by volunteers is sufficiently accurate and reliable. We engaged 119 volunteers over three years to map and estimate abundance of invasive plants in New York and New Jersey parklands. We tested their accuracy via collected pressed samples and by subsampling their transect points. We also compared the performances of volunteers and botanical experts. Our results support the notion that volunteer participation can enhance the data generated by scientists alone. We found that the quality of data collected might be affected by the environment in which the data are collected. We suggest that giving consideration to how people learn can not only help to achieve educational goals but can also help to produce more data to be used in scientific study.     

Exhibition

The objective of this critical review is to evaluate and summarize the literature on economic tools used to improve environmental decision making. Environmental decisions are complicated by pervasive uncertainty, and the lack of consensus on goals and on tradeoffs, such as air versus water pollution and versus loss of coal mining jobs. Five decision frameworks are used by regulatory agencies to simplify decision making. Congress’ choice of a decision framework designates the amount of data and analysis that will be required and the range and depth of social values that must be considered. Economic incentives have worked well for phasing out lead in gasoline, for increasing recycling and for reducing the volume of municipal solid waste. Congress has mandated incentives for acid rain and CFCs, and several countries have implemented carbon taxes to abate greenhouse gas emissions. Economic tools have become more central to the analysis and implementation of environmental policies; their role should continue to increase. We conclude that economic tools are extremely valuable, although their application is difficult.     

Workplace offense and victims' reactions: the effects of victim‐offender (dis)similarity,offense‐type,and cultural differences

This study examined the effects of workplace offenders' characteristics and offense‐type on victims' reactions. Responses from 352 employed graduate students in the U.S. and South Korea to a hypothetical offense incident revealed that employees from the U.S. and Korea differ in their expressed desirability of avoiding, seeking revenge against, and reconciling with an offending coworker depending on the offenders' similarity/dissimilarity to the victim and on the type of offense. As expected, Koreans (but not U.S. Americans) were more likely to avoid and to seek revenge on a coworker whose offensive remark was group‐ rather than personally‐directed. In addition, Koreans were most motivated to reconcile when an offensive remark came from a similar rather than dissimilar coworker and when the offense targeted them personally (not their group). However, U.S. Americans were most motivated to reconcile when an offensive remark came from a similar rather than dissimilar other and when the offense targeted their group (not them personally). Copyright © 2008 John Wiley & Sons, Ltd.     

Fungicide leaching from golf greens: effects of root zone composition and surfactant use

Soil water repellency in golf putting greens may induce preferential "finger flow," leading to enhanced leaching of surface applied fungicides. We examined the effects of root zone composition, treatment with a non-ionic surfactant, and the use of the fungicide iprodion or a combination of azoxystrobin and propiconazole on soil water repellency, soil water content distributions, fungicide leaching, and turf quality during 1 yr. Soil water repellency was measured using the water drop penetration time (WDPT) test and tension infiltrometers. Our study was made on a 3-yr-old experimental green seeded with creeping bentgrass (Agrostis stolonifera L.) 'Penn A-4' at Landvik in southeast Norway. The facility consists of 16 lysimeters with two different root zone materials: (i) straight sand (1% gravel, 96% sand, 3% silt and clay, 4 g kg(-1) organic matter) (SS) and (ii) straight sand mixed with garden compost to an organic matter content of 21 g kg(-1) (Green Mix [GM]). Surfactant treatment resulted in 96% lower average WDPTs at 1 cm depth, three times higher water infiltration rates at the soil surface, and reduced spatial variation in soil water contents. Fungicide leaching was close to zero for the GM lysimeters probably due to stronger sorption. Concentrations in the drainage water from SS lysimeters often exceeded surface water guideline values for all three fungicides, but surfactant treatment dramatically reduced fungicide leaching from these lysimeters. In autumn and winter, surfactant-treated plots were more infected with fungal diseases probably because of higher water content in the turfgrass thatch layer.