ISSN:1058-8337    

DOI:10.1080/15320389709383540

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1058-8337    

DOI:10.1080/15320389709383541

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1058-8337    

DOI:10.1080/15320389709383542

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1058-8337    

DOI:10.1080/15320389709383543

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Rate‐limited sorption/desorption can have a profound effect upon the transport of sorbing contaminants. Numerical and analytical models used to predict chemical movement through the subsurface rarely incorporate the effects of nonlinear sorption and desorption kinetics, resulting in potentially large overestimates of mass extractability. Mass transfer characteristics of arsenic‐contaminated soils at the site of a former arsenical herbicide manufacturer in Houston, Texas, were examined in the laboratory using soil columns. Unaffected soils comprised of silty sands to coarse sands were collected from the uppermost aquifer. Two soil columns were loaded with a known mass of mixed organic and inorganic forms of arsenic resident in site ground water. A third control column was prepared with dry 20 × 30 mesh ASTM silica sand. Leachate samples were collected from each void volume until arsenic breakthrough was achieved. The dynamic test applied a continuing head of water, operating in an upflow mode through 4‐in. diameter by 12‐in. long soil columns repacked toin situdensity. A flow‐through velocity of one void volume per day was chosen for arsenic loading to the columns and 0.08 void volume per day during the desorption phase of the test. Uncontaminated ground water was then passed through the columns, and the tests were restarted in the desorption mode. Analysis of the leachate and resulting arsenic concentrations in the test columns allowed for the calculation of distribution coefficients that describe arsenic behavior. Measured distribution coefficients during desorption ranged from 0.26 after one void volume to 3.3 after six void volumes had been passed through the column.

ISSN:1058-8337    

DOI:10.1080/15320389709383544

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Radiation exposure received by individuals living and working on a farmland contaminated with radium was evaluated by measuring the technologically enhanced radiation background using portable survey instruments and a high‐pressure ionization chamber. Analysis of selected organic compounds, metals, and radioactive material in samples of soil and water obtained from the farm demonstrate a potential risk to inhabitants that needs to be evaluated, especially for future generations living and working on this land who may not be aware of the potential hazard. The distribution of radium and several other hazardous waste materials was found to be significantly elevated in areas where sludge ponds and waste pits were formerly located. Transport of these contaminants in soil was detected byin situmeasurement of radium, which may be a useful analog for determining the translocation of metals and other contaminants associated with oil well‐drilling activities. Conventional risk assessment models, using default input parameters, assume that exposure to radium in the soil is via the food chain and radon, and that inhalation of resuspended particles is less important. These models also assume that the chemical and physical characteristics of the radium contamination remain constant in time. However, under certain environmental conditions, the radium compounds will become more soluble with time, increasing their significance as a source of radiation exposure, especially as the radium will persist in soil for many thousands of years. Assessment of present and future risk to populations living and working on these contaminated lands must account for the potential change in radium solubility with time and the increased risk from both inhalation and ingestion of radium

ISSN:1058-8337    

DOI:10.1080/15320389709383545

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The purpose of the present study was to provide new methods that would increase the rates of biodegradation of petroleum hydrocarbons in soil, thus reducing the time required to achieve a satisfactory level of residual hydrocarbon in anex situbioremediation. Results of laboratory studies on several techniques were used to guide our implementation of these methods in controlled field studies. Soils contaminated with nonvolatile hydrocarbons were treated with various combinations of (1) an anionic surfactant guanidinium cocoate (CGS), (2) a consortium of hydrocarbon‐degrading microorganisms, (3) a slow‐release form of nitrogen:urea, and (4) the bulking agent vermiculite. Laboratory results describing the activity of CGS have been presented previously (Jain et al., 1992). The amount and rate of hydrocarbon loss in treated soil was compared with hydrocarbon lost in soil that received no amendment other than water (water only). We also used a sheen screen method (Nelson et al., 1995), to assess the effectiveness of our field application of microorganisms.

ISSN:1058-8337    

DOI:10.1080/15320389709383546

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The distribution of total Pb in surface and subsurface soil horizons at an outdoor shooting range in southeastern Michigan was determined by single extraction elemental analysis (AAS and ICP‐AES). Significant Pb enrichment of the site's soils coincides closely with Pb vapor and particulate matter produced from shot shell primers and the downfall of Pb/Sb pellets associated with the recreational shooting of skeet and trap. Surface concentrations in these locations are 10 to 100 times greater than the background concentration found on adjacent properties. The distribution of Pb in the subsurface soil horizons corresponds to the distribution of Pb at the surface, which suggests the Pb is mobilizing and migrating downward through the vadose zone. This mobilization appears to be occurring despite the clay‐rich nature of the soils, and may be due to the transformation of metallic Pb into soluble Pb compounds of carbonate and sulfate: Both compounds appear to be present in crust material found coating many of the pellets found at the site. The downward migration of soluble Pb is a potential threat to groundwater that is present at the site at a depth of less than 1 m. The protection of surface water quality is also a concern because Pb pellets from the shooting range have been found in the bed sediments of a nearby stream.

ISSN:1058-8337    

DOI:10.1080/15320389709383547

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

An integrated soil vacuum extraction/ biofiltration system has been designed and installed at a gasoline‐contaminated leaking underground storage tank (LUST) site in southern Delaware. The system remediates contaminated moisture entrained in the air stream, employs automatic water level controls in the filters, and achieves maximum vapor extraction and VOC destruction efficiency with an optimum power input. In addition, the valving and piping layout allows the sequence of air flow through the filters to be reversed at given time intervals, which minimizes biofouling, thereby increasing efficiency by decreasing system backpressure. This integrated system achieves VOC destruction rates of up to 69%. The modular design allows for easy mobilization, setup, and demobilization at LUST sites throughout Delaware.

ISSN:1058-8337    

DOI:10.1080/15320389709383548

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:1058-8337    

DOI:10.1080/15320389709383538

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor