Use of Large‐Scale Electrokinetic and ZVI Treatment for Chlorinated Solvent Remediation at an Active Industrial Facility

The combination of electrokinetic and zero‐valent iron (ZVI) treatments were used to treat soils contaminated with chlorinated solvents, including dense nonaqueous phase liquid (DNAPL), at an active industrial site in Ohio. The remediation systems were installed in tight clay soils under truck lots and entrances to loading docks without interruption to facility production. The electrokinetic system, called Lasagna^TM, uses a direct current electrical field to mobilize contaminant via electroosmosis and soil heating. The contaminants are intercepted and reduced in situ using treatment zones containing ZVI. In moderately contaminated soils around the Lasagna^TM‐treated source areas, a grid of ZVI filled boreholes were emplaced to passively treat residual contamination in decades instead of centuries. The remediation systems were installed below grade and did not interfere with truck traffic during the installation and three years of operation. The Lasagna^TM systems removed 80 percent of the trichloroethylene (TCE) mass while the passive ZVI borings system has reduced the TCE by 40 percent. The remediation goals have been met and the site is now in monitoring‐only mode as natural attenuation takes over. © 2014 Wiley Periodicals, Inc.     

Sociogenetic responses to ecological variation in the ant Myrmica punctiventris are context dependent

Models of social evolution predict a strong relationship between ecological factors and sociogenetic organization in social insects (e.g. queen number, nestmate relatedness and population structure). Despite a large body of coherent theory, empirical support for these predictions is weak. Here we report the results of an experiment that manipulated two ecological parameters, food and nestsite availability, thought to be important for a population of the forest ant Myrmica punctiventris. Earlier work had shown that the sociogenetic structure varies between two populations of this species, and an ecological experiment in one of the populations (in Vermont) revealed that food supplementation had the strongest effects on nestmate relatedness. We repeated the experiment in the second population (in New York) and obtained strikingly different results. We show that nestsite supplementation had the strongest effect in the New York population, and that adding both food and nestsites affected nestmate relatedness in a direction opposite to that reported from the Vermont study. These results show that the ecological context is critically important for understanding the determinants of colony structure in ants. Furthermore, comparison of our data with that of a previous study shows that social organization in New York is temporally unstable. Thus, not only do ecological factors strongly influence social organization, but their influence can vary over time. Our study underscores the need for detailed information on the natural history and ecology of social species.     

Diel Cycling of Zinc in a Stream Impacted by Acid Rock Drainage: Initial Results from a New in situ Zn Analyzer

Recent work has demonstrated that many trace metals undergo dramatic diel (24-h) cycles in near neutral pH streams with metal concentrations reproducibly changing up to 500% during the diel period (Nimick et al., 2003). To examine diel zinc cycles in streams affected by acid rock drainage, we have developed a novel instrument, the Zn-DigiScan, to continuously monitor in situ zinc concentrations in near real-time. Initial results from a 3-day deployment at Fisher Creek, Montana have demonstrated the ability of the Zn-DigiScan to record diel Zn cycling at levels below 100 μg/l. Longer deployments of this instrument could be used to examine the effects of episodic events such as rainstorms and snowmelt pulses on zinc loading in streams affected by acid rock drainage.     

Size and composition distributions of particulate matter emissions: part 2--heavy-duty diesel vehicles

Particulate matter (PM) emissions from heavy-duty diesel vehicles (HDDVs) were collected using a chassis dynamometer/dilution sampling system that employed filter-based samplers, cascade impactors, and scanning mobility particle size (SMPS) measurements. Four diesel vehicles with different engine and emission control technologies were tested using the California Air Resources Board Heavy Heavy-Duty Diesel Truck (HHDDT) 5 mode driving cycle. Vehicles were tested using a simulated inertial weight of either 56,000 or 66,000 lb. Exhaust particles were then analyzed for total carbon, elemental carbon (EC), organic matter (OM), and water-soluble ions. HDDV fine (< or =1.8 microm aerodynamic diameter; PM1.8) and ultrafine (0.056-0.1 microm aerodynamic diameter; PM0.1) PM emission rates ranged from 181-581 mg/km and 25-72 mg/km, respectively, with the highest emission rates in both size fractions associated with the oldest vehicle tested. Older diesel vehicles produced fine and ultrafine exhaust particles with higher EC/OM ratios than newer vehicles. Transient modes produced very high EC/OM ratios whereas idle and creep modes produced very low EC/OM ratios. Calcium was the most abundant water-soluble ion with smaller amounts of magnesium, sodium, ammonium ion, and sulfate also detected. Particle mass distributions emitted during the full 5-mode HDDV tests peaked between 100-180 nm and their shapes were not a function of vehicle age. In contrast, particle mass distributions emitted during the idle and creep driving modes from the newest diesel vehicle had a peak diameter of approximately 70 nm, whereas mass distributions emitted from older vehicles had a peak diameter larger than 100 nm for both the idle and creep modes. Increasing inertial loads reduced the OM emissions, causing the residual EC emissions to shift to smaller sizes. The same HDDV tested at 56,000 and 66,000 lb had higher PM0.1 EC emissions (+22%) and lower PM0.1 OM emissions (-38%) at the higher load condition.     

Continuous, intermittent and passive sampling of airborne VOCs

Long sampling periods are often advantageous or required for measuring air quality and characterizing exposures. However, sampling periods exceeding 8 to 24 h using thermally desorbable adsorbent tube (TDT) samplers for the measurement of airborne volatile organic compounds (VOCs) face several challenges, including maintaining stable and low flow rates, and avoiding breakthrough of the adsorbent. These problems may be avoided using intermittent sampling; however, the literature contains few if any reports that have evaluated this technique in environmental, occupational or other applications. The purpose of this study is to evaluate continuous, intermittent and passive sampling methods using both laboratory and real-world tests. Laboratory tests compared continuous and intermittent (active) samplers in a controlled dynamic test gas generation system. Field tests used side-by-side active and passive samplers in an office, home workshop and four smokers' homes. All samples were analyzed for a wide range of VOCs by GC-MS. In most instances, intermittent sampling yielded better reproducibility (duplicate precision of 10 +/- 6%) than continuous low-flow sampling (18 +/- 5%), in part due to difficulty maintaining low flows. Concentrations obtained using intermittent sampling agreed with those for continuous sampling, with downward biases resulting primarily from errors in flow rate measurements. In the field, more VOC species were detected using active rather than passive sampling. Passive measurements were 12% lower than continuous measurements, a difference attributed to declining uptake rates at higher concentrations over the 3 to 4 d sampling period. Overall, most measurements obtained using the three sampling methods agreed within 20% for a wide range of concentrations (0.1 to 230 microg m(-3)). Both passive and intermittent sampling approaches are suitable for long sampling periods, but intermittent sampling provides greater flexibility with respect to sampling period, and permits the use of multi-bed adsorbents that can capture a wider range of VOCs.     

Screening and prioritisation of chemical risks from metal mining operations, identifying exposure media of concern

Metals have been central to the development of human civilisation from the Bronze Age to modern times, although in the past, metal mining and smelting have been the cause of serious environmental pollution with the potential to harm human health. Despite problems from artisanal mining in some developing countries, modern mining to Western standards now uses the best available mining technology combined with environmental monitoring, mitigation and remediation measures to limit emissions to the environment. This paper develops risk screening and prioritisation methods previously used for contaminated land on military and civilian sites and engineering systems for the analysis and prioritisation of chemical risks from modern metal mining operations. It uses hierarchical holographic modelling and multi-criteria decision making to analyse and prioritise the risks from potentially hazardous inorganic chemical substances released by mining operations. A case study of an active platinum group metals mine in South Africa is used to demonstrate the potential of the method. This risk-based methodology for identifying, filtering and ranking mining-related environmental and human health risks can be used to identify exposure media of greatest concern to inform risk management. It also provides a practical decision-making tool for mine acquisition and helps to communicate risk to all members of mining operation teams.     

Evaluating Spatio-temporal Complexities of Forest Management: An Integrated Agent-based Modeling and GIS Approach

The objective of this study is to integrate agent-based modeling and geographic information systems (GIS) for examining how interactions within forest management lead to patterns of land-cover change. Specifically, this study evaluates how management agents behave in the presence of variable timber prices, harvesting costs, and accessibility to timber and how their actions influence the spatial characteristics of the forest landscape over time. The GIS calculates the average harvested patch size, number of patches, and total harvested area as measures of emergent patterns resulting from agent actions. The results from the agent-based GIS model reveal that good economic conditions lead to few but large harvested patches, while deteriorating conditions will see more patches of smaller size if forest companies have access to high-quality timber. This study emphasizes the need for a complex systems approach to forest management as the model illustrates how system elements interact in a manner to produce emergent spatial patterns over time.     

Permutation/randomization-based inference for environmental data

Quantitative inference from environmental contaminant data is almost exclusively from within the classic Neyman/Pearson (N/P) hypothesis-testing model, by which the mean serves as the fundamental quantitative measure, but which is constrained by random sampling and the assumption of normality in the data. Permutation/randomization-based inference originally forwarded by R. A. Fisher derives probability directly from the proportion of the occurrences of interest and is not dependent upon the distribution of data or random sampling. Foundationally, the underlying logic and the interpretation of the significance of the two models vary, but inference using either model can often be successfully applied. However, data examples from airborne environmental fungi (mold), asbestos in settled dust, and 1,2,3,4-tetrachlorobenzene (TeCB) in soil demonstrate potentially misleading inference using traditional N/P hypothesis testing based upon means/variance compared to permutation/randomization inference using differences in frequency of detection (Δf _d). Bootstrapping and permutation testing, which are extensions of permutation/randomization, confirm calculated p values via Δf _d and should be utilized to verify the appropriateness of a given data analysis by either model.     

Use of continuous monitoring to assess stream nitrate flux and transformation patterns

Delivery of nitrogen from farmed fields to the stream network is an ongoing water quality issue in central North America and other parts of the world. Although fertilization and other farming practices have been refined to produce environmental improvements, stemming loss of nitrogen, especially in the soluble nitrate form, is a problem that has seemingly defied solution. The Iowa Nutrient Reduction Strategy is a policy initiative designed to implement conservation and other farm management practices to produce reductions in nitrate loading. The strategy does not focus on how the streams themselves may or may not be processing nitrogen and reducing downstream loading. We used continuous high-frequency nitrate and discharge monitoring over 3 years at two sites separated by 18 km in a low-order, agricultural stream in eastern Iowa to estimate how nitrogen is processed, and whether or not these processes are reducing downstream loading. We conclude that the upstream to downstream nitrate concentration decline between the two sites was not driven by denitrification. These data also show that nitrate concentrations are closely coupled to discharge during periods of adequate moisture, but decoupling of concentration from discharge occurs during dry periods. This decoupling is a possible indicator of in-stream nitrate processing. Finally, nitrate concentrations are likely diluted by water sourced from non-row crop land covers in the lower reaches of the watershed.     

Land application of tylosin and chlortetracycline swine manure: Impacts to soil nutrients and soil microbial community structure

The land application of aged chortetracycle (CTC) and tylosin-containing swine manure was investigated to determine associated impacts to soil microbial respiration, nutrient (phosphorus, ammonium, nitrate) cycling, and soil microbial community structure under laboratory conditions. Two silty clay loam soils common to southeastern South Dakota were used. Aerobic soil respiration results using batch reactors containing a soil-manure mixture showed that interactions between soil, native soil microbial populations, and antimicrobials influenced CO₂ generation. The aged tylosin treatment resulted in the greatest degree of CO₂ inhibition, while the aged CTC treatment was similar to the no-antimicrobial treatment. For soil columns in which manure was applied at a one-time agronomic loading rate, there was no significant difference in soil-P behavior between either aged CTC or tylosin and the no-antimicrobial treatment. For soil-nitrogen (ammonium and nitrate), the aged CTC treatment resulted in rapid ammonium accumulation at the deeper 40cm soil column depth, while nitrate production was minimal. The aged CTC treatment microbial community structure was different than the no-antimicrobial treatment, where amines/amide and carbohydrate chemical guilds utilization profile were low. The aged tylosin treatment also resulted in ammonium accumulation at 40 cm column depth, however nitrate accumulation also occurred concurrently at 10 cm. The microbial community structure for the aged tylosin was also significantly different than the no-antimicrobial treatment, with a higher degree of amines/amides and carbohydrate chemical guild utilization compared to the no-antimicrobial treatment. Study results suggest that land application of CTC and tylosin-containing manure appears to fundamentally change microbial-mediated nitrogen behavior within soil A horizons.