Enhanced concentrations of PAHs in groundwater at a coal tar site

Concentrations of polycyclic aromatic hydrocarbons (PAHs) in groundwater at a coal tar site were elevated by factors ranging from 3 (pyrene) to 50 (indeno[1,2,3-cd]pyrene) over purely dissolved concentrations. Air-groundwater surface tension measurements (70.6 +/- 3 dyn/cm) were not sufficiently different from air-pure water measures (72.2 +/- 0.1 dyn/cm) to ascribe the observed enrichments to either cosolvents or surfactants in the groundwater. Excess pyrene was associated with colloids that passed an ultrafilter at ambient pH but became ultrafilterable when the groundwater pH was lowered to 1. This suggested pyrene association with humic acids. Given the decrease in groundwater total organic carbon (TOC) of 4 mgc/L upon acidification and ultrafiltration, a partition coefficient of 10(5) L/kgc was estimated for this pyrene association. Use of the results for pyrene and scaling for the differences in PAH hydrophobicities enabled good predictions of the observed enrichments of less water-soluble PAHs in the groundwater. This is strong field evidence indicating colloid-facilitated transport of HOCs in groundwater. Assuming that humic-bound PAHs were as mobile as the dissolved PAHs, the fluxes of individual PAHs (e.g., benzo[a]pyrene) from the tar source were as much as 20 times greater than estimates based solely on tarwater partitioning predictions.     

Modeling the impact of chlorine on the behavior of Listeria monocytogenes on ready-to-eat meats

Listeria monocytogenes (Lm) continues to pose a food safety hazard in ready-to-eat (RTE) meats due to potential cross-contamination. Chlorine is commonly used to sanitize processing equipment and utensils. However, Lm may survive the treatment and then contaminate food products. The objective of this study was to characterize the behavior of chlorine-exposed Lm on RTE ham during refrigerated storage. A two strain cocktail of Lm serotype 4b was pre-treated with chlorine (0, 25, and 50 ppm) for one hour, and then inoculated onto the surface of RTE ham to obtain an inoculum of about 3.0 log CFU/g. The inoculated ham samples were stored at 4, 8, and 16 °C, and Lm was enumerated periodically during the storage. The growth characteristics (lag time and growth rate) of Lm were estimated using the DMFit software. The results indicated that Lm growth was suppressed by the chlorine treatment. At 4 °C, the lag time of Lm with no (0 ppm) chlorine exposure (4.2 days) was shorter than those exposed to 25 ppm (5.4 days) and 50 ppm (6.8 days). The lag time decreased with the increase of temperature, e.g., at 25 ppm, the lag times were 5.2, 3.8 and 2.6 days for 4, 8 and 16 °C, respectively, and increased with the increase of chlorine concentration, e.g., at 16 °C, the lag times were 1.2, 2.6 and 4.0 days for 0, 25 and 50 ppm, respectively. However, growth rate increased with the increase of temperature and decreased with the increase of chlorine concentration. The lag time and growth rate as a function of chlorine concentration and temperature can be described using a modified Ratkowsky model and a modified Zwietering model, respectively. The results showed that the growth of Lm on RTE ham was delayed by pre-exposure to chlorine (at ≤50 ppm). The predictive models developed will contribute to microbial risk assessments of RTE meats.     

Small-volume releases of gasoline in the vadose zone: impact of the additives MTBE and ethanol on groundwater quality

A controlled gasoline spill experiment was performed under outdoor conditions typical for winter in temperate regions to study the fate of methyl tert-butyl ether (MTBE), ethanol, benzene, and selected other petroleum hydrocarbons. Artificial gasoline containing MTBE and ethanol (5% w/w of each) was placed at a defined depth into a 2.3 m thick unsaturated zone of alluvial sand overlying a gravel aquifer in a lysimeter. During an initial period of 41 days without recharge, MTBE and hydrocarbon vapors migrated by vapor-phase diffusion to groundwater, while ethanol vapors were naturally attenuated. In a subsequent period of 30 days with 5-mm daily recharge, all soluble compounds including ethanol were transported to the groundwater. Ethanol disappeared concomitantly with benzene and all other petroleum hydrocarbons except isooctane from the aerobic groundwater due to biodegradation. MTBE persisted for longer than 6 months at concentrations larger than 125000 microg L(-1). No evidence for MTBE biodegradation was found, whereas > 99.6% of ethanol removal from the lysimeter was due to biodegradation. It is concluded that MTBE-free gasoline would be less harmful for groundwater resources and that ethanol is an acceptable substitute.     

万寿菊提取物中苯的污染来源分析

利用气相色谱-质谱联用法对印度和中国新疆万寿菊提取加工过程中的苯进行检测。结果表明,不同来源的万寿菊提取物中存在不同程度的苯(1.17~16.37 mg/kg)污染,对生产过程相关样品进行检测,发现提取溶剂中不同程度含有苯,从生产过程推理,提取溶剂应该是万寿菊提取物中苯的主要来源。在生产中要控制产品中苯的污染,首先应加强对提取溶剂的控制。     

Emission and atmospheric transport of particulate PAHs in Northeast Asia

The emission, concentration levels, and transboundary transport of particulate polycyclic aromatic hydrocarbons (PAHs) in Northeast Asia were investigated using particulate PAH measurements, the newly developed emission inventory (Regional Emission inventory in ASia for Persistent Organic Pollutants version, REAS-POP), and the chemical transport model (Regional Air Quality Model ver2 for POPs version, RAQM2-POP). The simulated concentrations of the nine particulate PAHs agreed well with the measured concentrations, and the results firmly established the efficacy of REAS/RAQM2-POP. It was found that the PAH concentrations in Beijing (China, source region), which were emitted predominantly from domestic coal, domestic biofuel, and other transformations of coal (including coke production), were approximately 2 orders of magnitude greater than those monitored at Noto (Japan, leeward region). In Noto, the PAH concentrations showed seasonal variations; the PAH concentrations were high from winter to spring due to contributions from domestic coal, domestic biofuel, and other transformations of coal, and low in summer. In summer, these contribution were decrease, instead, other sources, such as the on-road mobile source, were relatively increased compared with those in winter. These seasonal variations were due to seasonal variations in emissions from China, as well as transboundary transport across the Asian continent associated with meteorological conditions.     

多环芳烃（萘）在涤纶织物上的吸附行为

研究了多环芳烃之一的萘在涤纶织物上的吸附动力学、吸附等温线和吸附热力学,考察了温度对萘在涤纶织物上吸附的影响。实验结果表明,涤纶织物对萘的吸附量较大,拟二阶动力学方程可以较好地拟合吸附动力学过程;萘在涤纶织物上的等温吸附符合线性关系,可以用Linear方程描述,在实验测试的温度范围内,温度的升高使吸附量下降;萘在吸附过程中吸附热ΔH0为－16.494 kJ/mol,且吸附标准自由能改变量ΔG0＜0,表明萘在涤纶织物上的吸附是一放热过程,且为一自发进行的过程;萘在涤纶织物上的吸附主要是由偶极键力和氢键力起作用。     

Research Watch: Particulate transport of PAHs into the aquatic environment

Air.     

Modeling the probability of arsenic in groundwater in New England as a tool for exposure assessment

We developed a process-based model to predict the probability of arsenic exceeding 5 microg/L in drinking water wells in New England bedrock aquifers. The model is being used for exposure assessment in an epidemiologic study of bladder cancer. One important study hypothesis that may explain increased bladder cancer risk is elevated concentrations of inorganic arsenic in drinking water. In eastern New England, 20-30% of private wells exceed the arsenic drinking water standard of 10 micrograms per liter. Our predictive model significantly improves the understanding of factors associated with arsenic contamination in New England. Specific rock types, high arsenic concentrations in stream sediments, geochemical factors related to areas of Pleistocene marine inundation and proximity to intrusive granitic plutons, and hydrologic and landscape variables relating to groundwater residence time increase the probability of arsenic occurrence in groundwater. Previous studies suggest that arsenic in bedrock groundwater may be partly from past arsenical pesticide use. Variables representing historic agricultural inputs do not improve the model, indicating that this source does not significantly contribute to current arsenic concentrations. Due to the complexity of the fractured bedrock aquifers in the region, well depth and related variables also are not significant predictors.     

Evaluation of the impact of fuel hydrocarbons and oxygenates on groundwater resources

The environmental behavior of fuel oxygenates (other than methyl tert-butyl ether [MTBE]) is poorly understood because few data have been systematically collected and analyzed. This study evaluated the potential for groundwater resource contamination by fuel hydrocarbons (FHCs) and oxygenates (e.g., tert-butyl alcohol [TBA], tertamyl methyl ether [TAME], diisopropyl ether [DIPE], ethyl tert-butyl ether [ETBE], and MTBE) by examining their occurrence, distribution, and spatial extent in groundwater beneath leaking underground fuel tank (LUFT) facilities, focusing on data collected from over 7200 monitoring wells in 868 LUFT sites from the greater Los Angeles, CA, region. Excluding the composite measure total petroleum hydrocarbons as gasoline (TPHG), TBA has the greatestsite maximum (geometric mean) groundwater concentration among the study analytes; therefore, its presence needs to be confirmed at LUFT sites so that specific cleanup strategies can be developed. The alternative ether oxygenates (DIPE, TAME, and ETBE) are less likely to be detected in groundwater beneath LUFT facilities in the area of California studied and when detected are present at lower dissolved concentrations than MTBE, benzene, or TBA. Groundwater plume length was used as an initial indicator of the threat of contamination to drinking water resources. Approximately 500 LUFT sites were randomly selected and analyzed. The results demonstrate MTBE to pose the greatest problem, followed by TBA and benzene. The alternative ether oxygenates were relatively localized and indicated lesser potential for groundwater resource contamination. However, all indications suggest the alternative ether oxygenates would pose groundwater contamination threats similar to MTBE if their scale of usage is expanded. Plume length data suggest that in the absence of a completely new design and construction of the underground storage tank (UST) system, an effective management strategy may involve placing greater emphasis on UST program for ensuring adequate enforcement and compliance with existing UST regulations.     

Abundance, composition, and vertical transport of PAHs in marsh sediments

Petroleum-derived hydrocarbons continue to persist in Wild Harbor, West Falmouth, MA, following a spill of No. 2 fuel oil in 1969 from the barge Florida. Recent analysis of marsh sediments revealed that residues of degraded oil are present with concentrations of total petroleum hydrocarbons as high as approximately 9 mg g(-1). Polycyclic aromatic hydrocarbons (PAHs) constitute only a minor fraction of these residues with maximum concentrations of 134 mirog g(-1), but their fate is of interest because of their potential toxicity to organisms. As compared to typical unweathered No. 2 fuel oil, the current distribution of PAHs in the sediments reflects substantial weathering by abiotic and biotic processes, specifically a preferential loss of naphthalenes relative to phenanthrenes, as well as isomer-specific biodegradation of alkylated PAHs. Based on comparison to results from an earlier study, it appears that little or no change has occurred to the distribution of PAHs since 1989, indicating that weathering at this site has stalled or is now proceeding at a significantly slower rate. To assess whether sediment-water partitioning and molecular diffusion in the interstitial medium are now the dominant processes controlling the vertical distribution of PAHs, downcore profiles were compared to a numerical model. While in some cases the model accurately reproduced the measured data, there were instances where the distribution of PAHs was slightly under or overestimated. Reasons for these discrepancies are discussed and are likely due to bioturbation, colloid-facilitated transport, or both. Assessment of the influence of these processes on the spilled oil expands our understanding of the overall fate of these compounds and their potential long-term effects on the environment.     

基于制革工业浅析地下水环境影响评价

制革和毛皮加工是继造纸、酿造后轻工业领域第三大污染行业,造成了严重的环境问题,特别是水污染问题.环境影响评价是拟对人为活动可能造成的环境影响进行分析论证,并提出采取污染防治措施和对策,为生态环境主管部门及审批部门提供审批、决策依据.本文主要在结合实际工作经验和以往研究成果的基础上,总结阐述了制革工业对地下水环境影响评价...     

危废填埋场地下水环境影响评价研究

危险废物具有各种危害性,不仅对人体健康有着威胁,对于环境治理来说也有着极大的消极影响.就目前来说,虽然安全填埋技术已经较为成熟,但在实际实施过程中还是容易出现渗漏事故,渗漏液在地下容易穿透防渗层,从而影响地下水,所以这也是我们需要重视的问题之一.     

Inoculation of a DNAPL source zone to initiate reductive dechlorination of PCE

The ability to inoculate a PCE-NAPL source zone with no prior dechlorinating activity was examined using a near field-scale simulated aquifer. A known mass of PCE was added to establish a source zone, and the groundwater was depleted of oxygen using acetate and lactate prior to culture addition. An active and stable dechlorinating culture was used as an inoculum, and dechlorination activity was observed within 2 weeks following culture transfer. PCE reduction to TCE and cis-DCE was observed initially, and the formation of these compounds was accelerated by the addition of a long-term source of hydrogen (Hydrogen Releasing Compound). cis-DCE was the predominant chlorinated ethene present in the effluent after 225 days of operation, and production of VC and ethene lagged the formation of TCE and cis-OCE. However, dechlorination extent continued to improve over time, and VC eventually became a major product, suggesting that reinoculation was unnecessary. The detection of Dehalococcoides species in the source culture and in the simulated aquifer postinoculation indicated that the metabolic capability to dechlorinate beyond cis-DCE (t = 86 days and t = 245 days) was present. Elevated levels of TCE and cis-DCE were present in the source zone, but neither VC nor ethene were detected in the vicinity of NAPL. The results of this research indicated that adding dechlorinating cultures may be useful in the application of source zone bioremediation but that dechlorination beyond cis-DCE may be limited to regions downgradient of the source zone.     

Regional modeling of the atmospheric fate and transport of benzene and diesel particles

The Community Multiscale Air Quality model (CMAQ) was modified to simulate the atmospheric fate and transport of benzene and diesel particles. We simulated the July 11-15, 1995 period over a domain covering the eastern United States with a 12-km horizontal resolution and a finer (4 km) resolution over a part of the northeastern United States that includes Washington, DC and New York City. The meteorological fields were obtained from a simulation conducted earlier with the mesoscale model MM5. Gridded emission files for benzene and diesel particles were developed using the SMOKE modeling system. The results of the model simulations showed that benzene concentrations were commensurate with available measurements. Over the 4-km resolution domain, a comparison between simulated and measured 24-h average concentrations showed a fractional error of 0.46, a fractional bias of 0.14, and a coefficient of determination (r2) of 0.25. A comparison between simulated benzene hourly concentrations in New York City and in the Brigantine Wilderness Area, NJ, showed that urban concentrations were greater than the remote area concentrations by a factor of 2-5. The results of the diesel particle simulations showed spatial and temporal patterns that were similar to those obtained for benzene. However, because of the lesser contribution of on-road mobile sources to diesel particle emissions compared to benzene emissions, diesel particle concentrations showed stronger gradients between urban areas and remote areas. A comparison between diesel particle concentrations in New York City and in the Brigantine Wilderness Area, NJ, showed that the urban concentrations were greater than the remote area concentrations by a factor of 2-10. Assuming that diesel particles consist of 50% "elemental" carbon (EC), the simulated EC concentrations were in close agreement (within 10%) with the measured concentration in the urban area (Washington, DC) but were significantly lower than the measured EC concentrations in the remote area (Brigantine Wilderness Area). This result suggests that other sources beside diesel fuel engines contribute to atmospheric EC concentrations and that EC may not be a good surrogate for diesel particles. A comparison of both benzene and diesel particle simulated concentrations between an urban area (New York City) and a remote area (Brigantine Wilderness Area) shows that, at a spatial resolution of 4 km, the regional background may contribute from 10 to 20% to the peak concentrations. These results suggest that the regional background may not be negligible and should be taken into account in urban air toxics studies.     

Persistent source influences on the trailing edge of a groundwater plume, and natural attenuation timeframes: the F-Area Savannah River Site

At the Savannah River Site's F-Area, wastewaters containing radionuclides were disposed into seepage basins for decades. After closure and capping in 1991, the U.S. Department of Energy (DOE) has being monitoring and remediating the groundwater plume. Despite numerous studies of the plume, its persistence for over 20 years has not been well understood. To better understand the plume dynamics, a limited number of deep boreholes were drilled to determine the current plume characteristics. A mixing model was developed to predict plume tritium and nitrate concentrations. We found that the plume trailing edges have emerged for some contaminants, and that contaminant recharge from the basin's vadose zone is still important. The model's estimated time-dependent basin drainage rates combined with dilution from natural recharge successfully predicted plume tritium and nitrate concentrations. This new understanding of source zone influences can help guide science-based remediation, and improve predictions of the natural attenuation timeframes.     

Long-term natural attenuation of carbon and nitrogen within a groundwater plume after removal of the treated wastewater source

Disposal of treated wastewater for more than 60 years onto infiltration beds on Cape Cod, Massachusetts produced a groundwater contaminant plume greater than 6 km long in a surficial sand and gravel aquifer. In December 1995 the wastewater disposal ceased. A long-term, continuous study was conducted to characterize the post-cessation attenuation of the plume from the source to 0.6 km downgradient. Concentrations and total pools of mobile constituents, such as boron and nitrate, steadily decreased within 1-4 years along the transect. Dissolved organic carbon loads also decreased, but to a lesser extent, particularly downgradient of the infiltration beds. After 4 years, concentrations and pools of carbon and nitrogen in groundwater were relatively constant with time and distance, but substantially elevated above background. The contaminant plume core remained anoxic for the entire 10-year study period; temporal patterns of integrated oxygen deficit decreased slowly at all sites. In 2004, substantial amounts of total dissolved carbon (7 mol C m(-2)) and fixed (dissolved plus sorbed) inorganic nitrogen (0.5 mol N m(-2)) were still present in a 28-m vertical interval at the disposal site. Sorbed constituents have contributed substantially to the dissolved carbon and nitrogen pools and are responsible for the long-term persistence of the contaminant plume. Natural aquifer restoration at the discharge location will take at least several decades, even though groundwater flow rates and the potential for contaminant flushing are relatively high.     

Formation of chlorinated aromatics by reactions of Cl*, Cl2, and HCl with benzene in the cool-down zone of a combustor

Conversion of benzene to chlorobenzenes and monochlorophenols by reaction with chlorine radicals (Cl*) in the cool-down zone of a plug-flow combustor has been studied, and a mechanistic analysis of the initial steps of the oxy-chlorination process is proposed. Superequilibrium concentrations of Cl* are formed during combustion of chlorocarbon species and persist at significant concentration levels even after a substantial reduction in the flue gas temperature (T = 500-700 degrees C). At these temperatures, Cl* attack on benzene present in trace concentrations (initial benzene concentration of 300 ppmv or 1080 ppmv were used for the experiments) in the post-flame gas is shown to result in stable chlorinated products (chlorobenzenes and chlorophenols) and loss of benzene. These results suggest that Cl* attack on trace level aromatics and possibly other organic species may be the initial step in the formation of a broad class of chlorinated and oxy-chlorinated pollutants in the post combustion zone.     

Modeling the dynamics of fermentation and respiratory processes in a groundwater plume of phenolic contaminants interpreted from laboratory- to field-scale

A biodegradation model with consecutive fermentation and respiration processes, developed from microcosm experiments and simulated mathematically with microbial growth kinetics, has been implemented into a field-scale reactive transport model of a groundwater plume of phenolic contaminants. Simulation of the anaerobic plume core with H2 and acetate as intermediate products of biodegradation allows the rates and parameter values forfermentation processes and individual respiratory terminal electron accepting processes (TEAPS) to be estimated using detailed, spatially discrete, hydrochemical field data. The modeling of field-scale plume development includes consideration of microbial acclimatization, substrate toxicity toward degradation, bioavailability of mineral oxides, and adsorption of biogenic Fe(ll) species in the aquifer, identified from complementary laboratory process studies. The results suggest that plume core processes, particularly fermentation and Fe(lll)-reduction, are more important for degradation than previously thought, possibly with a greater impact than plume fringe processes (aerobic respiration, denitrification, and SO4-reduction). The accumulation of acetate as a fermentation product within the plume contributes significantly to the mass balance for carbon. These results demonstrate the value of quantifying fermentation products within organic contaminant plumes and strongly suggest that the conceptual model selected for reactive processes plays a dominant role in the quantitative assessment of risk reduction by naturally occurring biodegradation processes.