Towards optimal sampling schedules for integral pumping tests

Ethanol use as a gasoline additive is increasing, as are the chances of groundwater contamination caused by gasoline releases involving ethanol. To evaluate the impact of ethanol on dissolved hydrocarbon plumes, a field test was performed in which three gasoline residual sources with different ethanol fractions (E0: no ethanol, E10: 10% ethanol and E95: 95% ethanol) were emplaced below the water table. Using the numerical model BIONAPL/3D, the mass discharge rates of benzene, toluene, ethylbenzene, xylenes, trimethylbenzenes and naphthalene were simulated and results compared to those obtained from sampling transects of multilevel samplers. It was shown that ethanol dissolved rapidly and migrated downgradient as a short slug. Mass discharge of the hydrocarbons from the E0 and E10 sources suggested similar first-order hydrocarbon decay rates, indicating that ethanol from E10 had no impact on hydrocarbon degradation. In contrast, the estimated hydrocarbon decay rates were significantly lower when the source was E95. For the E0 and E10 cases, the aquifer did not have enough oxygen to support complete mineralization of the hydrocarbon compounds to the extent suggested by the field-based mass discharge. Introducing a heterogeneous distribution of hydraulic conductivity did little to overcome this discrepancy. A better match between the numerical model and the field data was obtained assuming partial degradation of the hydrocarbons to intermediate compounds. Besides depending on the ethanol concentration, the impact of ethanol on hydrocarbon degradation appears to be highly dependent on the availability of electron acceptors.     

N deposition as a threat to the World's protected areas under the Convention on Biological Diversity

This paper combines the world’s protected areas (PAs) under the Convention on Biological Diversity (CBD), common classification systems of ecosystem conservation status, and current knowledge on ecosystem responses to nitrogen (N) deposition to determine areas most at risk. The results show that 40% (approx. 11% of total area) of PAs currently receive >10 kg N/ha/yr with projections for 2030 indicating that this situation is not expected to change. Furthermore, 950 PAs are projected to receive >30 kg N/ha/yr by 2030 (approx. twice the 2000 number), of which 62 (approx. 11,300 km²) are also Biodiversity Hotspots and G200 ecoregions; with forest and grassland ecosystems in Asia particularly at risk. Many of these sites are known to be sensitive to N deposition effects, both in terms of biodiversity changes and ecosystem services they provide. Urgent assessment of high risk areas identified in this study is recommended to inform the conservation efforts of the CBD.     

The impact of nitrogen deposition on acid grasslands in the Atlantic region of Europe

A survey of 153 acid grasslands from the Atlantic biogeographic region of Europe indicates that chronic nitrogen deposition is changing plant species composition and soil and plant-tissue chemistry. Across the deposition gradient (2-44 kg N ha⁻¹ yr⁻¹) grass richness as a proportion of total species richness increased whereas forb richness decreased. Soil C:N ratio increased, but soil extractable nitrate and ammonium concentrations did not show any relationship with nitrogen deposition. The above-ground tissue nitrogen contents of three plant species were examined: Agrostis capillaris (grass), Galium saxatile (forb) and Rhytidiadelphus squarrosus (bryophyte). The tissue nitrogen content of neither vascular plant species showed any relationship with nitrogen deposition, but there was a weak positive relationship between R. squarrosus nitrogen content and nitrogen deposition. None of the species showed strong relationships between above-ground tissue N:P or C:N and nitrogen deposition, indicating that they are not good indicators of deposition rate.     

Heterogeneous mercury reaction chemistry on activated carbon

Experimental and theory-based investigations have been carried out on the oxidation and adsorption mechanism of mercury (Hg) on brominated activated carbon (AC). Air containing parts per billion concentrations of Hg was passed over a packed-bed reactor with varying sorbent materials at 140 and 30 degrees C. Through X-ray photoelectron spectroscopy surface characterization studies it was found that Hg adsorption is primarily associated with bromine (Br) on the surface, but that it may be possible for surface-bound oxygen (O) to play a role in determining the stability of adsorbed Hg. In addition to surface characterization experiments, the interaction of Hg with brominated AC was studied using plane-wave density functional theory. Various configurations of hydrogen, O, Br, and Hg on the zigzag edge sites of graphene were investigated, and although Hg-Br complexes were found to be stable on the surface, the most stable configurations found were those with Hg adjacent to O. The Hg-carbon (C) bond length ranged from 2.26 to 2.34 A and is approximately 0.1 A shorter when O is a nearest-neighbor atom rather than a next-nearest neighbor, resulting in increased stability of the given configuration and overall tighter Hg-C binding. Through a density of states analysis, Hg was found to gain electron density in the six p-states after adsorption and was found to donate electron density from the five s-states, thereby leading to an oxidized surface-bound Hg complex.     

Emission factors for high-emitting vehicles based on on-road measurements of individual vehicle exhaust with a mobile measurement platform

Fuel-based emission factors for 143 light-duty gasoline vehicles (LDGVs) and 93 heavy-duty diesel trucks (HDDTs) were measured in Wilmington, CA using a zero-emission mobile measurement platform (MMP). The frequency distributions of emission factors of carbon monoxide (CO), nitrogen oxides (NO(x)), and particle mass with aerodynamic diameter below 2.5 microm (PM2.5) varied widely, whereas the average of the individual vehicle emission factors were comparable to those reported in previous tunnel and remote sensing studies as well as the predictions by Emission Factors (EMFAC) 2007 mobile source emission model for Los Angeles County. Variation in emissions due to different driving modes (idle, low- and high-speed acceleration, low- and high-speed cruise) was found to be relatively small in comparison to intervehicle variability and did not appear to interfere with the identification of high emitters, defined as the vehicles whose emissions were more than 5 times the fleet-average values. Using this definition, approximately 5% of the LDGVs and HDDTs measured were high emitters. Among the 143 LDGVs, the average emission factors of NO(x), black carbon (BC), PM2.5, and ultrafine particle (UFP) would be reduced by 34%, 39%, 44%, and 31%, respectively, by removing the highest 5% of emitting vehicles, whereas CO emission factor would be reduced by 50%. The emission distributions of the 93 HDDTs measured were even more skewed: approximately half of the NO(x) and CO fleet-average emission factors and more than 60% of PM2.5, UFP, and BC fleet-average emission factors would be reduced by eliminating the highest-emitting 5% HDDTs. Furthermore, high emissions of BC, PM2.5, and NO(x) tended to cluster among the same vehicles.     

Correction methods for organic carbon artifacts when using quartz-fiber filters in large particulate matter monitoring networks: the regression method and other options

Sampling and handling artifacts can bias filter-based measurements of particulate organic carbon (OC). Several measurement-based methods for OC artifact reduction and/or estimation are currently used in research-grade field studies. OC frequently is not artifact-corrected in large routine sampling networks (e.g., U.S. Environmental Protection Agency (EPA)'s Chemical Speciation Network). In some cases, the OC artifact has been corrected using a regression method (RM) for artifact estimation. In this method, the gamma-intercept of the regression of the OC concentration on the fine particle (PM2.5) mass concentration is taken to be an estimate of the average OC sampling artifact (net of positive and negative artifacts). This paper discusses options for artifact correction in large routine sampling networks. Specifically, the goals are to (1) articulate the assumptions and limitations inherent to the RM, (2) describe other artifact correction approaches, and (3) suggest a cost-effective method for artifact correction in large monitoring networks. The RM assumes a linear relationship between measured OC and PM mass: a constant slope (OC mass fraction) and a constant intercept (RM artifact estimate). These assumptions are not always valid. Additionally, outliers and other individual data points can have a large influence on the RM artifact estimates. The RM yields results within the range of measurement-based methods for some datasets and not for others. Given that the adsorption of organic gases increases with atmospheric concentrations of organics, subtraction of an average artifact from all samples (e.g., across multiple sites) will underestimate OC for lower-concentration samples (e.g., clean sites) and overestimate OC for higher-concentration samples (e.g., polluted sites). For relatively accurate, simple, and cost-effective artifact OC estimation in large networks, the authors suggest backup filter sampling on at least 10% of sampling days at all sites with artifact correction on a sample-by-sample basis as described herein.     

Impact of different plants on the gas profile of a landfill cover

Methane is an important greenhouse gas emitted from landfill sites and old waste dumps. Biological methane oxidation in landfill covers can help to reduce methane emissions. To determine the influence of different plant covers on this oxidation in a compost layer, we conducted a lysimeter study. We compared the effect of four different plant covers (grass, alfalfa + grass, miscanthus and black poplar) and of bare soil on the concentration of methane, carbon dioxide and oxygen in lysimeters filled with compost. Plants were essential for a sustainable reduction in methane concentrations, whereas in bare soil, methane oxidation declined already after 6 weeks. Enhanced microbial activity - expected in lysimeters with plants that were exposed to landfill gas - was supported by the increased temperature of the gas in the substrate and the higher methane oxidation potential. At the end of the first experimental year and from mid-April of the second experimental year, the methane concentration was most strongly reduced in the lysimeters containing alfalfa + grass, followed by poplar, miscanthus and grass. The observed differences probably reflect the different root morphology of the investigated plants, which influences oxygen transport to deeper compost layers and regulates the water content.     

Impact of increased collection rates and the use of commingled collection systems on the quality of recovered paper. Part 1: increased collection rates

The recovery and utilization of recovered paper have increased over past decades all over the world due to economic, environmental, and social issues. However, it is well known that an extended recovered paper collection is detrimental to its quality, either by the exploitation of lower quality sources such as households, or the spreading of commingled systems instead of selective collection systems. The influence of these two factors was assessed by analyzing the quality of different recovered paper grades used as raw material in a mill located in Madrid (Spain) producing newsprint and light weight coated paper from recovered paper. Part 1 of the paper deals with the impact of increased collection rates on the quality of recovered paper and Part 2 with the use of commingled collection systems. Results of Part 1 show that increased collection rates have a large impact on the quality of the recovered paper. The quality, measured as total unusable material and moisture contents, had deteriorated very rapidly in only 4 years (2005–2008) as a consequence of increased collection rates. Collection rates increased in Spain from 58.5% to 68.6% during this period, resulting in more than 50% increase of total unusable material and 25% of moisture content. The downgrading of the quality of recovered paper is one of the major threats for extending the current limits of paper recycling. Therefore, future challenge is to increase its availability but maintaining its quality.     

Multiple use of waste catalysts with and without regeneration for waste polymer cracking

Waste plastics contain a substantial number of valuable chemicals. The wastes from post-consumer as well as from industrial production can be recycled to valuable chemical feedstock, which can be used in refineries and/or petrochemical industries. This chemical recycling process is an ideal approach in recycling the waste for a better environment. Polymer cracking using a laboratory fluidised bed reactor concentrated on the used highly contaminated catalyst, E-Cat 2. Even though E-Cat 2 had low activity due to fewer acid sites, the products yielded were similar with amorphous ASA and were far better than thermal cracking. The high levels of heavy metals, namely nickel and vanadium, deposited during their lifetime as an FCC catalyst, did not greatly affect on the catalyst activity. It was also shown that E-Cat 2 could be used with and without regeneration. Although there was more deactivation when there was no regeneration step, the yield of gases (C₂-C₇) remained fairly constant. For the first time, these results indicate that “waste” FCC catalyst (E-Cat) is a good candidate for future feedstock recycling of polymer waste. The major benefits of using E-Cat are a low market price, the ability to tolerate reuse and regeneration capacity.     

A preliminary categorization of end-of-life electrical and electronic equipment as secondary metal resources

End-of-life electrical and electronic equipment (EEE) has recently received attention as a secondary source of metals. This study examined characteristics of end-of-life EEE as secondary metal resources to consider efficient collection and metal recovery systems according to the specific metals and types of EEE. We constructed an analogy between natural resource development and metal recovery from end-of-life EEE and found that metal content and total annual amount of metal contained in each type of end-of-life EEE should be considered in secondary resource development, as well as the collectability of the end-of-life products. We then categorized 21 EEE types into five groups and discussed their potential as secondary metal resources. Refrigerators, washing machines, air conditioners, and CRT TVs were evaluated as the most important sources of common metals, and personal computers, mobile phones, and video games were evaluated as the most important sources of precious metals. Several types of small digital equipment were also identified as important sources of precious metals; however, mid-size information and communication technology (ICT) equipment (e.g., printers and fax machines) and audio/video equipment were shown to be more important as a source of a variety of less common metals. The physical collectability of each type of EEE was roughly characterized by unit size and number of end-of-life products generated annually. Current collection systems in Japan were examined and potentially appropriate collection methods were suggested for equipment types that currently have no specific collection systems in Japan, particularly for video games, notebook computers, and mid-size ICT and audio/video equipment.