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Guidance for assessing the soil vapor-to-indoor air exposure pathway continues to evolve with documents being drafted by regulatory agencies, industry, and industry-regulatory collaborations. While variable across the federal, sta...
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Guidance for assessing the soil vapor-to-indoor air exposure pathway continues to evolve with documents being drafted by regulatory agencies, industry, and industry-regulatory collaborations. While variable across the federal, state, and local levels, guidance is converging toward a multiple- lines-of-evidence-based paradigm that involves combinations of indoor air sub- slab soil gas, deeper soil gas, groundwater, and soil sampling in addition to screening-level modeling. There are concerns about implementing this type of guidance due to questions about current data collection methods, possible indoor air sources, a lack of knowledge about temporal behavior, not knowing how to deal with conflicting lines of evidence, and pathway assessment costs. This talk will provide an overview of current issues with pathway assessment and tie those to ongoing studies and opportunities for future research, and discuss alternate pathway assessment paradigms.
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In situ permeable treatment barriers (PTBs) are designed such that contaminated groundwater flows through an engineered treatment zone within which contaminants are eliminated or the concentrations are significantly reduced. These...
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In situ permeable treatment barriers (PTBs) are designed such that contaminated groundwater flows through an engineered treatment zone within which contaminants are eliminated or the concentrations are significantly reduced. These systems are often considered for the containment of dissolved contaminant plumes, or for controlling the discharge and larger-scale impact of dissolved contaminants from source zones to aquifers. Previous studies have concluded that a better understanding of the subsequent improvement in down- gradient groundwater quality with time is needed. The objectives of this project were to: a) propose a practicable approach that can be used to project reasonable order-of magnitude estimates of groundwater quality improvements with time down-gradient of a PTB, b) conduct detailed monitoring and characterization down-gradient of a well-understood PTB site, and c) illustrate and reflect on the use of the proposed approach for the PTB system studied in this project.
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摘要 :
In situ permeable treatment barriers (PTB) are designed so that contaminated groundwater flows through an engineered treatment zone within which contaminants are eliminated or the concentrations are significantly reduced. These sy...
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In situ permeable treatment barriers (PTB) are designed so that contaminated groundwater flows through an engineered treatment zone within which contaminants are eliminated or the concentrations are significantly reduced. These systems are often considered for the containment of dissolved groundwater contaminant plumes or for controlling the discharge and larger scale impact of dissolved contaminants from source zones to aquifers. The performance of a PTB is typically judged by short-term changes in groundwater concentrations with time within the treatment zone and also in wells located some distance downgradient. The objectives of this project were to: (a) propose a practicable approach that can be used to project reasonable order-of- magnitude estimates of groundwater quality improvements with time downgradient of a PTB, (b) conduct detailed monitoring and characterization downgradient of a well-understood PTB site, and (c) illustrate and reflect on the use of the proposed approach for the PTB system studied in this project. These objectives were met by this demonstration project. A PTB is installed to prevent further downgradient discharge of impacted groundwater and to meet prescribed numerical standards for groundwater cleanup downgradient of the PTB. When selecting a PTB system, it is critical that all stakeholders understand how groundwater quality changes will occur with time and distance downgradient of the PTB and how long it might take to achieve standards at different distances downgradient of the PTB. Detailed monitoring and characterization of groundwater concentration changes with time downgradient of a full-scale methyl tert-butyl ether (MTBE) biobarrier PTB system were conducted at the Naval Base Ventura County (NBVC). The recommended site-specific assessment approach for PTB systems is one that focuses on characterization of vertical variations in horizontal hydraulic conductivity.
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Air sparging generally involves the injection of air into an aquifer through vertical or horizontal wells. In situations where contaminant vapor recovery is necessary (e.g., as required by regulation, or in situations where vapor ...
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Air sparging generally involves the injection of air into an aquifer through vertical or horizontal wells. In situations where contaminant vapor recovery is necessary (e.g., as required by regulation, or in situations where vapor migration could cause adverse impacts), air sparging systems are coupled with soil vapor extraction (SVE) systems. Historically, practitioners have installed air sparging systems to: (1) treat immiscible contaminant source zones at or below the capillary fringe; (2) remediate dissolved contaminant plumes; and (3) provide barriers to prevent dissolved contaminant plume migration. Air sparging systems are also now being incorporated into novel aquifer bioremediation schemes for the delivery of other gases (e.g., oxygen, hydrogen, propane), and they have also been used as a means of improving air distribution for bioventing applications targeting near-capillary fringe soils. Some practitioners implement a variation of air sparging that they term biosparging. In practice, the term biosparging is frequently used to refer to air sparging systems when the intent is to operate without an SVE system. The helium air recovery tests discussed above can be used to quantify the efficiency of vapor capture during combined IAS and SVE operation, and can provide valuable insight to the areal distribution of IAS treatment zones. The ease and speed with which these tests can be conducted and interpreted makes them well suited for IAS pilot tests (even 1-day tests).
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Officials and administrators who are responsible for DoD information systems should read this report. The report explains the extent of transmitting user passwords in plain text while accessing software development environments an...
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Officials and administrators who are responsible for DoD information systems should read this report. The report explains the extent of transmitting user passwords in plain text while accessing software development environments and the vulnerabilities associated with it. A Central Design Activity is defined as a designated organization within a Component that has responsibility for designing, converting, programming, testing, documenting, or subsequently maintaining computer operating or applications software for use at more than one location. We evaluated authentication protection at an Army, a Navy, and an Air Force Central Design Activity. Central Design Activities use software development environments to develop and maintain the software for which they are responsible. A software development environment is an integrated suite of tools to aid the development of software in a particular programming language or for a particular application. Logging on to the vast majority of computing systems, including software development environments, is protected by passwords. The person logging on must supply a user name plus the password associated with that user name. The system evaluates the password to verify the user's identity claim. This process is called authentication. Password authentication mechanisms work if passwords are kept secret at all stages. During a previous evaluation, we confirmed at one central design activity that user names and passwords were transmitted in plain text to software development environments located at the Defense Information Systems Agency Defense Enterprise Computing Centers. Readily available software would permit an attacker to capture the transmitted user name and password for possible unauthorized accesses.
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In June 1994, the State Water Resource Control Board (SWRCB) contracted with the Lawrence Livermore National Laboratory University of California (LLNL/UC) Leaking Underground Fuel Tank (LUFT) Team to study the cleanup of LUFTs in ...
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In June 1994, the State Water Resource Control Board (SWRCB) contracted with the Lawrence Livermore National Laboratory University of California (LLNL/UC) Leaking Underground Fuel Tank (LUFT) Team to study the cleanup of LUFTs in California. The study consisted of data collection and analysis from LUFT cases and a review of other studies on LUFT cleanups. Two final reports were submitted to the SWRCB in October and November 1995. These reports were entitled: Recommendations To Improve the Cleanup Process for California's Leaking Underground Fuel Tanks (LUFTs), and California Leaking Underground Fuel Tank (LUFT) Historical Case Analysis. The U.S. Environmental Protection Agency (EPA) has reviewed both LLNL/UC reports and issued a fact sheet supporting the findings and recommendations. Data were collected primarily from the alluvial geologic settings typical of the San Francisco Bay Area, Los Angeles Basin, and the Central Valley. These data represent California's highly populated areas where most gas stations are found and most LUFT releases occur. Study results can be applied to similar settings throughout California. The length of dissolved benzene plumes in groundwater at LUFT releases were evaluated over time to determine how plumes behave. Over 1,200 LUFT cases were evaluated. Benzene was analyzed because it is the human carcinogen of greatest concern in fuel. It is relatively soluble in water, and cleanup standards are generally tied to benzene concentrations. Ninety percent of the dissolved benzene plumes were less than 280 ft. in length. Most of these plumes were either stable or shrinking in length. Seventy percent of the plumes in the study sites were found in shallow groundwater, less than 25 ft. below the ground surface. The study concluded that with rare exceptions, petroleum fuel releases will naturally degrade (passive bioremediation) in California's subsurface conditions. Removing the source of the release will speed the cleanup time.
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An experiment conducted on the 10-day Spacelab 1 mission aboard the ninth Space Shuttle flight in November to December 1983 was designed to measure factors involved in the control of erythrocyte turnover that might be altered duri...
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An experiment conducted on the 10-day Spacelab 1 mission aboard the ninth Space Shuttle flight in November to December 1983 was designed to measure factors involved in the control of erythrocyte turnover that might be altered during weightlessness. Blood samples were collected before, during, and after the flight. Immediately after landing, red cell mass showed a mean decrease of 9.3 percent in the four astronauts. Neither hyperoxia nor an increase in blood phosphate was a cause of the decrease. Red cell survival time and iron incorporation postflight were not significantly different from their preflight levels. Serum haptoglobin did not decrease, indicating that intravascular hemolysis was not a major cause of red cell mass change. An increase in serum ferritin after the second day of flight may have been caused by red cell breakdown early in flight. Erythropoietin levels decreased during and after flight, but preflight levels were high and the decrease was not significant. The space flight-induced decrease in red cell mass may result from a failure of erythropoiesis to replace cells destroyed by the spleen soon after weightlessness is attained.
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Current life sciences concepts relating to Space Station are presented including the following: research, extravehicular activity, biobehavioral considerations, medical care, maintenance of dental health, maintaining health throug...
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Current life sciences concepts relating to Space Station are presented including the following: research, extravehicular activity, biobehavioral considerations, medical care, maintenance of dental health, maintaining health through physical conditioning and countermeasures, protection from radiation, atmospheric contamination control, atmospheric composition, noise pollution, food supply and service, clothing and furnishings, and educational program possibilities. Information on the current status of Soviet Space Stations is contained.
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