David W. Rice

The Transport and Fate of Ethanol and BTEX in Groundwater Contaminated by Gasohol

Ethanol is used a component in all gasoline in Brazil, and its use could increase significantly in the U.S. to meet the requirements of the Clean Air Act Amendments. Recent problems with ground water contamination by methyl tert-butyl ether (MTBE) have made policymakers more cognizant of the need to consider the overall impact of gasoline oxygenates in the environment. Therefore, a thorough understanding of the impact of incorporating ethanol as a gasoline component on the fate and transport of gasoline releases is required. This article provides a comprehensive review of the transport of ethanol and monoaromatic hydrocarbons (BTEX) in the subsurface following a gasohol spill. Two mechanisms related to the presence of ethanol are generally considered to impact BTEX transport. Ethanol can increase the aqueous concentration of BTEX compounds due to a cosolvent effect, and it can inhibit BTEX biodegradation by preferentially consuming electron acceptors and nutrients. Our review illustrates that cosolvent effects should be minor at the ethanol concentrations expected from gasohol spills. Nevertheless, the inhibition of BTEX biodegradation and the possible decrease in sorption-related retardation suggests that ethanol is likely to increase BTEX plume lengths. The net effect of ethanol on natural attenuation of BTEX is likely to be system specific, depending largely on the release scenario and the assimilative capacity of the aquifer.

Reproductive success, xenobiotic contaminants and hepatic mixed-function oxidase (MFO) activity in Platichthys stellatus populations from San Francisco Bay

To identify some specific effects of organic contaminants on fisheries in an urbanized estuary we compared the reproductive success of starry flounder from San Francisco Bay with concentrations of tissue contaminants and hepatic mixed-function oxidase (MFO) activity. We found significantly lower (P < 0·05) sediment concentrations of total identified polynuclear aromatic hydrocarbons (PAHs) in the less urbanized San Pablo Bay (SP) area (Fig. 1) than in the more urbanized central bay (CB) stations (Table 1). For flounder in early gametogenesis (August and September) the SP fish (n = 20) had significantly lower (P < 0·01) liver concentrations of Aroclor 1260 (0·34 ± 0·14 μg/g) than those at the CB stations: Berkeley (BK, n = 20, 1·6 ± 1·6 μg/g); Oakland (OK, n = 16, 2·3 ± 2·8 μg/g); and Alameda (AL, n = 4, 2·2 ± 1 μg/g). A similar pattern existed for DDT concentrations: SP = 0·2 ± 0·16 μg/g; BK = 0·1 ± 0·34 μg/g; OK = 0·4 ± 0·53 μg/g; and AL = 0·4 ± 0·33 μg/g. Total PAHs in livers were as follows: SP = 0·14 μg/g; BK = 2·6 μg/g; OK = 1·4 μg/g; and AL = 14 μg/g. Although gonad index, liver index, and presence of fin rot are inversely related to aryl hydrocarbon hydroxylase (AHH) activity, healthy fish in a similar reproductive state have lower AHH activities in the SP area. For example, in August and September, 1984, mean AHH activities were as follows: SP = 203 ± 89, and CB = 355 ± 200 pmol 3-OH-B[a]P mg microsomal protein min. We found a log-linear relationship for AHH activity and its percent inhibition by 7,8-benzoflavone (10−4m) and only a few fish from SP showed enhanced AHH activity after addition of 7,8-benzoflavone. This suggests that most of the starry flounder in San Francisco Bay are induced.

Seasonal and annual distribution of organic contaminants in marine sediments from Elkhorn slough, moss landing harbor and nearshore Monterey Bay, California.

This 3-year study provides data on the spatial, seasonal and annual variability of hydrocarbons and total organic carbon present in marine sediments at three sites: Elkhorn Slough, Moss Landing Harbor and nearshore Monterey Bay in the vicinity of Moss Landing, California. The study provides baseline information that could be used to evaluate the potential impacts of future fuel oil releases occuring in the Moss Landing area. Groups of hydrocarbons were chosen to represent the hydrocarbon inputs into the Moss Landing area. These included the pesticide dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyl (PCB), phthalic acid ester (PAE), polycyclic aromatic hydrocarbon (PAH) and combustion PAHs (SigmaCOMBs). For SigmaDDTs, SigmaPCBs, SigmaPAEs, SigmaPAHs and SigmaCOMBs, the major sources of variability were between sites and random effects. Subsites within each site contributed little variability. No significant seasonal differences in any chemical contaminant group were found at any site. Significant seasonal differences in total organic carbon (TOC) and significant annual differences in SigmaPCBs, SigmaPAHs, SigmaCOMBs and SigmaPAEs were found at the nearshore Monterey Bay site. Significant annual differences in SigmaPAEs and TOC were found within Moss Landing Harbor, and significant annual differences in SigmaPAEs were found within the Elkhorn Slough site. Implications for future sampling designs in the Moss Landing area are that given the current baseline conditions (a stable, low rate of hydrocarbon input), a variability of 75-150 m(2) may not need to be heavily sampled. Spatial variability, not seasonal or annual variability, is the major source of hydrocarbon variability in Moss Landing sediments, although 3 years may not be long enough to establish long-term annual trends. Further research to determine the SigmaPAH spatial sampling scale for oil spills is needed.

Mixed-function oxidase-specific activity in wild and caged speckled sanddabs Citharichthys stigmaeus in Elkhorn Slough, Moss Landing Harbor and nearshore Monterey Bay, California

The goal of this study was to characterize the spatial, seasonal and annual hepatic activities of mixed-function oxidase (MFO) in the speckled sanddab Citharichthys stigmaeus, the most common fish in the Moss Landing area. In addition, techniques to monitor MFO activities in caged speckled sanddabs were developed and tested. Once the relationship between MFO activities in caged and wild fish populations is determined, caged fish could be used to monitor potential hydrocarbon impacts at Moss Landing, or other marine sites. During each of the spatial, seasonal and annual sediment samplings conducted in 1985-1987 as part of a separate hydrocarbon variability study at Moss Landing, 12 wild speckled sanddabs were collected from Moss Landing Harbor, Elkhorn Slough and nearshore Monterey Bay sites. In addition, four locations were chosen for a 14-day field caged fish experiment. The caged fish experiments successfully demonstrated the feasibility of using caged sanddabs as indicators of hydrocarbon exposure. The major source of variability in hepatic aryl hydrocarbon hydroxylase activity in wild speckled sanddabs from the Moss Landing area is due to seasonal rather than site differences. Significant relationships between caged fish MFO response and sediment hydrocarbon concentrations were found. It is possible that caged fish could be used in place of costly sediment sampling and analysis, and provide a more direct method to assess biological impacts. Many of the caging techniques demonstrated in this study can easily be transferred to other benthic flatfish, and other marine and freshwater environments.

“Smart” pump and treat

Abstract Lawrence Livermore National Laboratory (LLNL) is approaching the final phase of the Superfund decision-making process for site restoration and will soon initiate full-scale clean-up. Despite some well-publicized perceived failings of the pump and treat approach, we have concluded that intelligent application of this strategy is the best choice for ground water restoration at LLNL. Our proposed approach differs sufficiently from the pump-and-treat methods implemented at other sites that we call it “smart” pump and treat. Smart pump and treat consists of four distinct, but interrelated, elements: three pre-remediation strategies and one applying to the active management of the extraction process. Together, these techniques constitute an integrated program that embodies crucial aspects of contaminant flow and transport to speed up the remediation of contaminated aquifers. The four elements are: (1) a spatially detailed site characterization, linked with regional hydrogeologic simulations; (2) directed extraction, where the extraction and recharge locations are controlled by field-determined hydrogeologic parameters; (3) field-validated simulations that match the complexity of the collected data; and (4) adaptive pumping and reinjection where spatial positions and rates vary with time. Together, these techniques minimize the cost and the time to reach regulatory-directed cleanup goals and maximize the rate of contaminant removal.

Evaluating Chlorinated Hydrocarbon Plume Behavior Using Historical Case Population Analyses

A nationwide survey of chlorinated volatile organic compound (CVOC) plumes was conducted across a spectrum of sites from diverse hydrogeologic environments and contaminant release scenarios. The goal was to evaluate significant trends in the data that relate plume behavior to site variables (e.g., source strength, mean groundwater velocity, reductive dehalogenation regime) through correlation and population analyses. Data from 65 sites (government facilities, dry cleaners, landfills) were analyzed, yielding 247 individual CVOC plumes by compound. Data analyses revealed several trends, notably correlations between plume length and maximum observed concentration (presumably reflecting the source term) and mean groundwater velocities. Reductive dehalogenation, indicated by daughter products and groundwater geochemistry, appears to exert a relatively subtle effect on plume length, apparent only after the contributions of source strength and groundwater velocity are factored out. CVOC properties (K oc , Henrys Law constant) exert significant effects on variability in maximum observed concentrations between sites but hold little influence on plume length. Probabilistic plume modeling, entailing Monte Carlo simulation of an analytical solution for average plume behavior with parameter distributions derived from site data, was used to produce a synthetic plume set for comparison with field data. Modeling results exhibited good agreement with field data in terms of parameter sensitivity.