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At least 955 records · Page 53Linked to original sources
PubMed2003

A mathematical model of phytoremediation for petroleum-contaminated soil: model development.

We present a simple model for root length density that combines the generally accepted spatial (exponential decrease with depth) and temporal (sinusoidal) variability of root length. Parameters in this model for root length density can be determined from assumed or measured information regarding the annual biomass turnover, maximum standing biomass, and maximum depth of root penetration. The root length density model, coupled with information regarding the average root lifespan, gives specific root growth and senescence functions that are the forcing functions for the phytoremediation model. We present a screening level mathematical model for phytoremediation that accounts for the growth and senescence of roots in the system. This is an important factor for recalcitrant, immobile compounds found in weathered crude oil contaminated soils. The phytoremediation model is based on variable volume compartments that have individual first-order degradation rate constants; as the roots move through the soil, the soil cycles through the rhizosphere zone, decaying root zone and bulk soil zone. Thus, although the oil is immobile, as the roots penetrate through the soil the oil is brought into contact with the rhizosphere.

Algorithms↗
PubMed2003

Stimulation of hybrid poplar growth in petroleum-contaminated soils through oxygen addition and soil nutrient amendments.

Hybrid poplar trees (Populus deltoides x nigra DN34) were grown in a green-house using hydrocarbon-contaminated soil from a phytoremediation demonstration site in Health, Ohio. Two independent experiments investigated the effect of nutrient addition on poplar growth and the importance of oxygen addition to root development and plant growth. Biomass measurements, poplar height, and leaf color were used as indicators of plant health in the selection of a 10/5/5 NPK fertilizer applied at 1121 kg/ha (112 kg-N, 24.4 kg-P, 46.5 kg-K per ha) to enhance hybrid poplar growth at the Health site. Five passive methods of oxygen delivery were examined, including aeration tubes, gravel addition, and an Oxygen Release Compound (ORC). When ORC was placed in coffee filters above hydrocarbon-contaminated soil, a statistically significant increase of 145% was observed in poplar biomass growth, relative to unamended controls. The ORC in filters also stimulated significant increases in root density. A 15.2-cm interval of soil directly below ORC addition exhibited an increase from 2.6 +/- 1.0 mg/cm3 to 4.8 +/- 1.0 mg/cm3, showing stimulation of root growth in hydrocarbon-stained soil. The positive response of hybrid poplars to oxygen amendments suggests that overcoming oxygen limitation to plants should be considered in phytoremediation projects when soil contamination exerts a high biochemical oxygen demand, such as in former refinery sites.

Biodegradation, Environmental↗
PubMed2004

Washing of soil contaminated with PAHs and heavy petroleum fractions using two nonionic [correction] and one ionic surfactant: effect of salt addition.

The aim of this work was to select the surfactant for washing an aged soil contaminated with PAHs and heavy hydrocarbons fraction, between two anionic and one ionic surfactant. The effect of the addition of salt when washing with the ionic surfactant was evaluated. Results of this work indicated the following. Soil contaminants concentration as g TPH kg soil(-1) was 17,200 mg kg(-1). All washing performances were dependent on the type of surfactant and applied doses. In general, best removal efficiencies were obtained with TW80 (59.57%), followed very near by E600 (57.67%), and at the en by SDS (39.0%), in comparison to the blank assessment (only water), where removal efficiency was about 12%. These removal efficiencies were correlated to the MW, CMC, and HLB values of every surfactant. SDS efficiencies were quite enhanced by the addition of 1% (60.36% removal efficiency) and 2% (70.28% removal efficiency) of NaCl. Its seems that there exist two reasons for this phenomena i.e., the diminution in the real value of SDS CMC (as reported by many authors) and, the capabilities of NaCl solutions to dissolve higher amounts of hydrocarbons than only tap water.

Environmental Pollution↗
PubMed2000

Effect of leachability on environmental risk assessment for naturally occurring radioactive materials in petroleum oil fields.

Elevated concentrations of naturally occurring radioactive material (NORM), including 238U, 232Th, and their progeny found in underground geologic deposits, are often encountered during crude oil recovery. Radium, the predominant radionuclide brought to the surface with the crude oil and produced water, co-precipitates with barium in the form of complex compounds of sulfates, carbonates, and silicates found in sludge and scale. These NORM deposits are highly stable and very insoluble under ambient conditions at the earth's surface. However, the co-precipitated radium matrix is not thermodynamically stable at reducing conditions which may enable a fraction of the radium to eventually be released to the environment. Although the fate of radium in uranium mill tailings has been studied extensively, the leachability of radium from crude oil NORM deposits exposed to acid-rain and other aging processes is generally unknown. The leachability of radium from NORM contaminated soil collected at a contaminated oil field in eastern Kentucky was determined using extraction fluids having wide range of pH reflecting different extreme environmental conditions. The average 226Ra concentration in the samples of soil subjected to leachability testing was 32.56 Bq g(-1) +/- 0.34 Bq g(-1). The average leaching potential of 226Ra observed in these NORM contaminated soil samples was 1.3% +/- 0.46% and was independent of the extraction fluid. Risk assessment calculations using the family farm scenario show that the annual dose to a person living and working on this NORM contaminated soil is mainly due to external gamma exposure and radon inhalation. However, waterborne pathways make a non-negligible contribution to the dose for the actual resident families living on farmland with the type of residual NORM contamination due to crude oil recovery operations.

Animal Feed↗
PubMed1980

Mortality among workers employed in petroleum refining and petrochemical plants.

The cause-specific mortality experience of 3,105 members of the Oil, Chemical and Atomic Workers International Union was examined to determine if there were unusual patterns of fatal disease that may be indicative of hazardous agents in the work environment. Deaths among active Union members that were reported by locals in Texas between 1947 and 1977 were identified through membership records, and proportionate mortality was analyzed in several broad industrial categories. PMRs for cancers of the liver and biliary passages, pancreas, lung and skin were elevated among refinery and petrochemical plant workers; however, risks did not increase with length of membership. Increased relative frequencies of stomach cancer, cancer of the brain, leukemia and multiple myeloma were confined to white males in the same category who had been Union members for 10 or more years. Excess deaths from stomach cancer and brain cancer were found among white male members employed at one specific oil refinery and petrochemical plant. Observed numbers of deaths from cancer of the stomach were greater than expected among whites and nonwhites, and an elevated PMR for lung cancer among nonwhites was found at an additional plant. Findings suggest that workers in this industry may be at increased risk of certain cancers and indicate areas for further investigation.

Adult↗
PubMed2001

Updated mortality study of workers at a petroleum refinery in Torrance, California, 1959 to 1997.

The updated cohort consisted of 3328 workers who were employed at the Mobil (now ExxonMobil) Torrance, California, refinery for at least 1 year between 1959 and 1997. The vital status of the cohort was determined through a variety of sources, including company employment or retirement records, the Social Security Administration's Death Master File, and the National Death Index. The updated study covered an observation period of 38 years from 1960 to 1997, with a total of 60,612 person-years of observation. A total of 705 (21.2%) cohort members were identified as having died. Mortality data were analyzed in terms of cause-specific standardized mortality ratios (SMRs) and 95% confidence intervals (95% CIs), with expected deaths based on US national cause-, gender-, race-, year-, and age-specific mortality rates. The overall mortality of the cohort was significantly lower than expected when compared with the US general population (SMR, 81.9; 95% CI, 76.0 to 88.2). Overall cancer mortality was also lower than expected (SMR, 79.8; 95% CI, 67.9 to 93.1). For specific cancer sites, significant mortality deficits were observed for cancer of the digestive system (SMR, 70.9; 95% CI, 49.4 to 98.6) and cancer of the respiratory system (SMR, 74.1; 95% CI, 55.5 to 97.0). No significant increase was reported for any site-specific cancer. For nonmalignant diseases, no significant increase was observed for any cause. In particular, significant mortality deficits were reported for ischemic heart disease (SMR, 87.7; 95% CI, 77.2 to 99.3), chronic endocardial disease and other myocardial insufficiencies (SMR, 8.3; 95% CI, 0.2 to 46.0), all other heart disease (SMR, 64.2; 95% CI, 43.0 to 92.2), and influenza and pneumonia (SMR, 59.2; 95% CI, 33.1 to 97.6). Detailed analysis by length of employment did not reveal any significant mortality excess or upward trend. Analyses of male employees by job classification (process and maintenance) were conducted. Among maintenance workers, mortality from cirrhosis of the liver (SMR, 190.1; 95% CI, 101.2 to 325.1) and suicide (SMR, 208.6; 95% CI, 111.1 to 356.7) were significantly elevated. However, these mortality excesses did not seem to be related to employment at the refinery. No other causes of death showed significant increase among maintenance workers. A similar separate analysis was conducted for process workers, and no significant excess was detected for any cause. The findings from the present study are discussed in conjunction with results from previous investigations of employees at the Torrance refinery and with results from other refinery studies. Potential limitations of the study are also discussed.

Adult↗
PubMed2003

A petroleum company's experience in implementing a comprehensive medical fitness for duty program for professional truck drivers.

Aggregate health risk appraisal data from Chevron Texaco's truck driver workforce revealed that approximately 50% of the truck drivers who completed a health risk appraisal were found to be at risk for a back injury. Lost time records revealed that this population had 65% more lost workdays attributed to cumulative trauma injuries compared with acute trauma injuries. Chevron Texaco addressed the issue by implementing a medical fitness for duty program consisting of three components: physical examination (physical examination mandated by the Department of Transportation and a functional capacity evaluation), education (on safe body mechanics), and physical fitness. After a 1-year development period, the fitness for duty program was implemented for Chevron Texaco's professional truck drivers in North America. In the first year of the program, 109 functional capacity evaluations were completed by trained clinicians, and 88% of candidates were found "able to work without restrictions," whereas 6% were found "able to work with caution." The article describes the program results to date, and also describes the follow-up program for drivers found to be at risk for a back injury.

Absenteeism↗