The soils, tropical climate, and network of canals and rivers of southern Vietnam have created one of the most diverse tropical jungles and intensely cultivated landscapes of Southeast Asia. This paradise has a long h...The soils, tropical climate, and network of canals and rivers of southern Vietnam have created one of the most diverse tropical jungles and intensely cultivated landscapes of Southeast Asia. This paradise has a long history of numerous wars, foreign occupations, and most recently the Second Indochina War (aka the Vietnam War 1965-1972) which defoliated rain forests and ancient wetland mangroves and left behind contaminated soil and sediment hotspots. During this war, the United States (US) military sprayed 80 million liters of Agent Orange contaminated with the dioxin TCDD in a guerrilla war against communist insurgents. Agent Orange was a synthetic plant growth regulator comprised of equal amounts of two herbicides 2,4-dichloro phenoxyacetic acid C8H6Cl2O3 (2,4-D) and 2,4,5-trichlorophenoxyacetic acid C8H5Cl3O3 (2,4,5-T). TCDD, the dioxin, 2,3,7,8-tetrachlorodibenzodioxin (C12H4Cl4O2) was an unintended byproduct of the accelerated combustion process used in the manufacture of herbicides containing 2,4,5-T. Agent Orange has frequently been blamed for soil and sediment contamination and long-term human health problems;however, the true source of harm is the dioxin TCDD. Agent Orange has a short half-life of days and weeks after application to vegetation, and has not been found to persist, after 50 years, in the water or soils of southern Vietnam. However, the half-life of dioxin TCDD depends on where it is deposited and varies from 1 to 3 years on soil surfaces that have been fully exposed to sunlight, to as long as 20 to 50 years or more when buried in tropical subsoils, and more than 100 years in river and sea sediments. Dioxin TCDD was heavily concentrated in the US Air Force bases in Vietnam where the herbicides were stored, loaded on planes and helicopters for aerial spraying, and used extensively around military base perimeter fences as a security measure to prevent surprise attacks. Bien Hoa Air Force base, 40 km northeast of Ho Chi Minh City, continues to be one of the mega-hotspots where after 48 years th展开更多
Bio remidiation possibility of soil contaminated by oil mud,and the optimization of the technological conditions for the bioremediation were studied using bio slurry reactor in pilot scale.A group of micro orgamism wh...Bio remidiation possibility of soil contaminated by oil mud,and the optimization of the technological conditions for the bioremediation were studied using bio slurry reactor in pilot scale.A group of micro orgamism which are addicted to oil and rich in both amount and species in oil contaminated soil was discovered. Fusarium sp.was screeded for its high crude oil degradation rate.Oil mud with high concentration of crude oil was mixed with clean soil in the ratio of 1∶1,and 10% complex organic fertilizer and inorganic nutrients in proper proportion were added before treatment. Particularly,microbiological agent of indigenous superior strains for crude oil degradation was applied. Other operative conditions of the reactor included 25℃ for temperature and intermittent venting. After 75 days operation,the contents of total petroleum hydrocarbon (TPH) in oil mud was decreased from 43.39 to 0.72g·kg -1 .The degradation rate of TPH reached 98.3% under optimal conditions.展开更多
Soil moisture collected from three locations, namely University of Calabar (UNICAL), Calabar municipal solid waste dumpsite (MSWD) and a mechanic workshop (MW) all within Calabar metropolis, Nigeria, were analyzed qua...Soil moisture collected from three locations, namely University of Calabar (UNICAL), Calabar municipal solid waste dumpsite (MSWD) and a mechanic workshop (MW) all within Calabar metropolis, Nigeria, were analyzed quarterly in a one year study at different depths (0.5 m and 1 m) for some physicochemical parameters. UV-visible spectrophotometer, titration and atomic absorption spectrophotometer (AAS) were the employed analytical techniques. With the exception of chloride, all other parameters showed higher values with depth. Higher values for the analyzed parameters were generally reported for MSWD and this was largely the result of the presence of a variety of contaminants in this location. Microbial analysis of soil samples from the locations revealed the presence of SRB in MW, which could have possibly influenced the soil moisture chemistry of the location. Corrosion rate was calculated from weight loss measurements and the quarterly results were all for follow the trend: UNICAL < MW < MSWD. At the end of the 4th quarter, the corrosion rates at 0.5 m depth were 0.0057, 0.0070, and 0.0101 mm/hour for UNICAL, MW, and MSWD, respectively, while their corresponding values at 1 m depth were 0.0087, 0.0114, and 0.0128 μm/hour. The values were shown to increase with depth. R-mode factor analysis identified some important factors which could have been responsible for the variation in the chemistry of the soil moisture.展开更多
文摘The soils, tropical climate, and network of canals and rivers of southern Vietnam have created one of the most diverse tropical jungles and intensely cultivated landscapes of Southeast Asia. This paradise has a long history of numerous wars, foreign occupations, and most recently the Second Indochina War (aka the Vietnam War 1965-1972) which defoliated rain forests and ancient wetland mangroves and left behind contaminated soil and sediment hotspots. During this war, the United States (US) military sprayed 80 million liters of Agent Orange contaminated with the dioxin TCDD in a guerrilla war against communist insurgents. Agent Orange was a synthetic plant growth regulator comprised of equal amounts of two herbicides 2,4-dichloro phenoxyacetic acid C8H6Cl2O3 (2,4-D) and 2,4,5-trichlorophenoxyacetic acid C8H5Cl3O3 (2,4,5-T). TCDD, the dioxin, 2,3,7,8-tetrachlorodibenzodioxin (C12H4Cl4O2) was an unintended byproduct of the accelerated combustion process used in the manufacture of herbicides containing 2,4,5-T. Agent Orange has frequently been blamed for soil and sediment contamination and long-term human health problems;however, the true source of harm is the dioxin TCDD. Agent Orange has a short half-life of days and weeks after application to vegetation, and has not been found to persist, after 50 years, in the water or soils of southern Vietnam. However, the half-life of dioxin TCDD depends on where it is deposited and varies from 1 to 3 years on soil surfaces that have been fully exposed to sunlight, to as long as 20 to 50 years or more when buried in tropical subsoils, and more than 100 years in river and sea sediments. Dioxin TCDD was heavily concentrated in the US Air Force bases in Vietnam where the herbicides were stored, loaded on planes and helicopters for aerial spraying, and used extensively around military base perimeter fences as a security measure to prevent surprise attacks. Bien Hoa Air Force base, 40 km northeast of Ho Chi Minh City, continues to be one of the mega-hotspots where after 48 years th
文摘Bio remidiation possibility of soil contaminated by oil mud,and the optimization of the technological conditions for the bioremediation were studied using bio slurry reactor in pilot scale.A group of micro orgamism which are addicted to oil and rich in both amount and species in oil contaminated soil was discovered. Fusarium sp.was screeded for its high crude oil degradation rate.Oil mud with high concentration of crude oil was mixed with clean soil in the ratio of 1∶1,and 10% complex organic fertilizer and inorganic nutrients in proper proportion were added before treatment. Particularly,microbiological agent of indigenous superior strains for crude oil degradation was applied. Other operative conditions of the reactor included 25℃ for temperature and intermittent venting. After 75 days operation,the contents of total petroleum hydrocarbon (TPH) in oil mud was decreased from 43.39 to 0.72g·kg -1 .The degradation rate of TPH reached 98.3% under optimal conditions.
文摘Soil moisture collected from three locations, namely University of Calabar (UNICAL), Calabar municipal solid waste dumpsite (MSWD) and a mechanic workshop (MW) all within Calabar metropolis, Nigeria, were analyzed quarterly in a one year study at different depths (0.5 m and 1 m) for some physicochemical parameters. UV-visible spectrophotometer, titration and atomic absorption spectrophotometer (AAS) were the employed analytical techniques. With the exception of chloride, all other parameters showed higher values with depth. Higher values for the analyzed parameters were generally reported for MSWD and this was largely the result of the presence of a variety of contaminants in this location. Microbial analysis of soil samples from the locations revealed the presence of SRB in MW, which could have possibly influenced the soil moisture chemistry of the location. Corrosion rate was calculated from weight loss measurements and the quarterly results were all for follow the trend: UNICAL < MW < MSWD. At the end of the 4th quarter, the corrosion rates at 0.5 m depth were 0.0057, 0.0070, and 0.0101 mm/hour for UNICAL, MW, and MSWD, respectively, while their corresponding values at 1 m depth were 0.0087, 0.0114, and 0.0128 μm/hour. The values were shown to increase with depth. R-mode factor analysis identified some important factors which could have been responsible for the variation in the chemistry of the soil moisture.
