Tillage and field scale controls on greenhouse gas emissions

There is a lack of understanding of how associations among soil properties and management-induced changes control the variability of greenhouse gas (GHG) emissions from soil. We performed a laboratory investigation to quantify relationships between GHG emissions and soil indicators in an irrigated agricultural field under standard tillage (ST) and a field recently converted (2 yr) to no-tillage (NT). Soil cores (15-cm depth) were incubated at 25 degrees C at field moisture content and 75% water holding capacity. Principal component analysis (PCA) identified that most of the variation of the measured soil properties was related to differences in soil C and N and soil water conditions under ST, but soil texture and bulk density under NT. This trend became more apparent after irrigation. However, principal component regression (PCR) suggested that soil physical properties or total C and N were less important in controlling GHG emissions across tillage systems. The CO2 flux was more strongly determined by microbial biomass under ST and inorganic N content under NT than soil physical properties. Similarly, N2O and CH4 fluxes were predominantly controlled by NO3- content and labile C and N availability in both ST and NT soils at field moisture content, and NH4+ content after irrigation. Our study indicates that the field-scale variability of GHG emissions is controlled primarily by biochemical parameters rather than physical parameters. Differences in the availability and type of C and N sources for microbial activity as affected by tillage and irrigation develop different levels and combinations of field-scale controls on GHG emissions.     

Energy use,blue water footprint,and greenhouse gas emissions for current food consumption patterns and dietary recommendations in the US

This article measures the changes in energy use, blue water footprint, and greenhouse gas (GHG) emissions associated with shifting from current US food consumption patterns to three dietary scenarios, which are based, in part, on the 2010 USDA Dietary Guidelines (US Department of Agriculture and US Department of Health and Human Services in Dietary Guidelines for Americans, 2010, 7th edn, US Government Printing Office, Washington, 2010). Amidst the current overweight and obesity epidemic in the USA, the Dietary Guidelines provide food and beverage recommendations that are intended to help individuals achieve and maintain healthy weight. The three dietary scenarios we examine include (1) reducing Caloric intake levels to achieve “normal” weight without shifting food mix, (2) switching current food mix to USDA recommended food patterns, without reducing Caloric intake, and (3) reducing Caloric intake levels and shifting current food mix to USDA recommended food patterns, which support healthy weight. This study finds that shifting from the current US diet to dietary Scenario 1 decreases energy use, blue water footprint, and GHG emissions by around 9 %, while shifting to dietary Scenario 2 increases energy use by 43 %, blue water footprint by 16 %, and GHG emissions by 11 %. Shifting to dietary Scenario 3, which accounts for both reduced Caloric intake and a shift to the USDA recommended food mix, increases energy use by 38 %, blue water footprint by 10 %, and GHG emissions by 6 %. These perhaps counterintuitive results are primarily due to USDA recommendations for greater Caloric intake of fruits, vegetables, dairy, and fish/seafood, which have relatively high resource use and emissions per Calorie.     

Religion and environmental politics in the US House of Representatives

Does religion affect legislators’ behavior on environmental policy in the US? Studies of environmental policy making have not examined this question, although the literature suggests that religion might affect legislative behavior on environmental policy. This study examines the relationship between US House members’ religion and roll-call voting on environmental legislation from 1973 to 2009. It finds significant differences across religious traditions. Legislators’ party and characteristics of constituencies relevant to environmental politics increasingly, but not entirely, mediate these differences.     

Coupling fishery dynamics,human health and social learning in a model of fish-borne pollution exposure

Pollution-induced illnesses are caused by toxicants that result from human activity and are often entirely preventable. However, where industrial priorities have undermined responsible governance, exposed populations must reduce their exposure by resorting to voluntary protective measures and demanding emissions abatement. This paper presents a coupled human–environment system model that represents the effects of water pollution on the health and livelihood of a fishing community. The model is motivated by an incident from 1949 to 1968 in Minamata, Japan, where methylmercury effluent from a local factory poisoned fish populations and humans who ate them. We model the critical role of risk perception in driving both social learning and the protective feedbacks against pollution exposure. These feedbacks are undermined in the presence of social misperceptions such as stigmatization of the injured. Through numerical simulation and scenario analysis, we compare our model results with historical datasets from Minamata, and find that the conditions for an ongoing pollution epidemic are highly unlikely without social misperception. We also find trade-offs between human health outcomes, the viability of the polluting industry and the survival of the fishery. We conclude that an understanding of human–environment interactions and misperception effects is highly relevant to the resolution of contemporary pollution problems, and merits further study.     

Understanding the fate and transport of petroleum hydrocarbons from coal tar within gasholders

Coal tars have been identified as posing a threat to human health due to their toxic, mutagenic and carcinogenic characteristics. Workers involved in former gasholders decommissioning are potentially exposed to relevant concentrations of volatile and semi-volatile hydrocarbons upon opening up derelict tanks and during tar excavation/removal. While information on contaminated sites air-quality and its implications on medium-long term exposure is available, acute exposure issues associated with the execution of critical tasks are less understood. Calculations indicated that the concentration of a given contaminant in the gasholder vapour phase only depends on the coal tar composition, being only barely affected by the presence of water in the gasholder and the tar volume/void space ratio. Fugacity modelling suggested that risk-critical compounds such as benzene, naphthalene and other monocyclic and polycyclic aromatic hydrocarbons may gather in the gasholder air phase at significant concentrations. Gasholder emissions were measured on-site and compared with the workplace exposure limits (WELs) currently in use in UK. While levels for most of the toxic compounds were far lower than WELs, benzene air-concentrations where found to be above the accepted threshold. In addition due to the long exposure periods involved in gasholder decommissioning and the significant contribution given by naphthalene to the total coal tar vapour concentration, the adoption of a WEL for naphthalene may need to be considered to support operators in preventing human health risk at the workplace. The Level I fugacity approach used in this study demonstrated its suitability for applications to sealed environments such as gasholders and its further refining could provide a useful tool for land remediation risk assessors.     

An Approach for Evaluating the Repeatability of Rapid Wetland Assessment Methods: The Effects of Training and Experience

We sampled 92 wetlands from four different basins in the United States to quantify observer repeatability in rapid wetland condition assessment using the Delaware Rapid Assessment Protocol (DERAP). In the Inland Bays basin of Delaware, 58 wetland sites were sampled by multiple observers with varying levels of experience (novice to expert) following a thorough training workshop. In the Nanticoke (Delaware/Maryland), Cuyahoga (Ohio), and John Day (Oregon) basins, 34 wetlands were sampled by two expert teams of observers with minimal protocol training. The variance in observer to observer scoring at each site was used to calculate pooled standard deviations (SD_pool), coefficients of variation, and signal-to-noise ratios for each survey. The results showed that the experience level of the observer had little impact on the repeatability of the final rapid assessment score. Training, however, had a large impact on observer to observer repeatability. The SD_pool in the Inland Bay survey with training (2.2 points out of a 0–30 score) was about half that observed in the other three basins where observers had minimal training (SD_pool = 4.2 points). Using the results from the survey with training, we would expect that two sites assessed by different, trained observers who obtain DERAP scores differing by more than 4 points are highly likely to differ in ecological condition, and that sites with scores that differ by 2 or fewer points are within variability that can be attributed to observer differences.     

Quantitative arsenic speciation in two species of earthworms from a former mine site

The relationship between the total arsenic concentration and the chemical speciation of arsenic in two species of earthworm (Lumbricus rubellus and Dendrodrilus rubidus) in relation to the host soil, was investigated for 13 sites of varying arsenic content, including a background level garden soil and a former mine site at the Devon Great Consols, UK. Earthworms were collected with the host soil (As soil concentration range 16-12, 466 mg kg(-1) dry weight) and measured for their total arsenic (concentration range 7-595 mg kg(-1) dry weight) using inductively coupled plasma mass spectrometry (ICP-MS). A methanol-water mixture was used to extract arsenic species from the earthworms prior to determination of the individual arsenic species by a combination of anion and cation exchange high performance liquid chromatography coupled to inductively coupled plasma mass spectrometry (HPLC-ICP-MS). A gradient elution anion exchange method is presented whereby nine arsenic species could be measured in one sample injection. Arsenic species were identified by comparison of retention times and sample spiking with known standards and a fully characterised seaweed extract. Arsenic was generally present in the earthworm as arsenate (As(V)) or arsenite (As(III)) and arsenobetaine (AB). Methylarsonate (MA), dimethylarsinate (DMA) and three arsenosugars (glycerol, phosphate, sulfate) were present as minor constituents. These results are discussed in relation to the mechanisms for coping with exposure to soil bound arsenic.     

The response of hydrophobic organics and potential toxicity in streams to urbanization of watersheds in six metropolitan areas of the United States

Semipermeable membrane devices (SPMDs) were deployed in streams along a gradient of urban land-use intensity in and around six metropolitan areas: Atlanta, Georgia; Raleigh-Durham, North Carolina; and Denver-Fort Collins, Colorado, in 2003; and Dallas-Fort Worth, Texas; Milwaukee-Green Bay, Wisconsin; and Portland, Oregon, in 2004 to examine relations between percent urban land cover in watersheds and the occurrence, concentrations, and potential toxicity of hydrophobic compounds. Of the 142 endpoints measured in SPMD dialysates, 30 were significantly (alpha = 0.05) related to the percent of urban land cover in the watersheds in at least one metropolitan area. These 30 endpoints included the aggregated measures of the total number of compounds detected and relative toxicity (Microtox(R) and P450RGS assays), in addition to the concentrations of 27 individual hydrophobic compounds. The number of compounds detected, P450RGS assay values, and the concentrations of pyrogenic polycyclic aromatic hydrocarbons (PAHs) were significantly related to percent urban land cover in all six metropolitan areas. Pentachloroanisole, the most frequently detected compound, was significantly related to urban land cover in all metropolitan areas except Dallas-Fort Worth. Petrogenic PAHs and dibenzofurans were positively related to percent urban land cover in Atlanta, Raleigh-Durham, Denver, and Milwaukee-Green Bay. Results for other endpoints were much more variable. The number of endpoints significantly related to urban land cover ranged from 6 in Portland to 21 Raleigh-Durham. Based on differences in the number and suite of endpoints related to urban intensity, these results provide evidence of differences in factors governing source strength, transport, and/or fate of hydrophobic compounds in the six metropolitan areas studied. The most consistent and significant results were that bioavailable, aryl hydrocarbon receptor agonists increase in streams as basins become urbanized. Potential toxicity mediated by this metabolic pathway is indicated as an important factor in the response of aquatic biota to urbanization.     

Critical technical elements of state bioassessment programs: a process to evaluate program rigor and comparability

We developed a systematic process to evaluate state/tribal bioassessment programs to provide information about the rigor of the technical approach. This is accomplished via on-site interviews to produce an evaluation that assigns one of four levels of rigor as an outcome. Level 4 is the most rigorous and reflects a technical capacity to accurately determine incremental condition and support management programs. The remaining three levels are less able to assess incremental condition and are appropriate for only some management support needs. Accurately determining impairment and diagnosing pollution-specific stressors are fundamental tasks that states/tribes must accomplish to provide management support. This goal is fulfilled to varying degrees by most states/tribes. The evaluation employs a checklist and a sliding scale of rigor for 13 technical elements. Feedback is provided to each state/tribe via a technical memorandum that describes the technical components of the monitoring program, highlights strengths, and recommends improvements for specific technical issues. This can be used to refine the bioassessment and monitoring programs to better support management programs. The results of 14 state/tribal evaluations are included here. The majority (nine states, one tribe) revealed that most operate at level 2 with developmental activities that will elevate the level of program rigor already underway. Two states operate level 4 programs and each have numeric biocriteria and refined designated uses in their water quality standards. This is the ultimate goal of the process of engaging states in the development of bioassessment programs in the U.S.