Microbial activity and distribution during enhanced contaminant dissolution from a NAPL source zone

Laboratory experiments were conducted to assess microbial reductive dechlorination in one-dimensional sand columns containing a 10 cm long source zone of uniformly distributed residual tetrachloroethene (PCE) nonaqueous phase liquid (NAPL), a 10 cm long transition zone directly down-gradient of the source zone containing some nonuniformly distributed NAPL ganglia, and a 40 cm long plume region down-gradient of the transition zone. The activity and distribution of Sulfurospirillum multivorans, a PCE-to-1,2-cis-dichloroethene (cis-DCE) dechlorinating bacterium, was evaluated in columns containing either a mixed-NAPL (0.25 mol/mol PCE in hexadecane) or pure PCE-NAPL. Significant dechlorination of PCE to cis-DCE was observed in the mixed-NAPL column, resulting in 53% PCE-NAPL mass recovery in the effluent with PCE-NAPL dissolution enhanced by up to 13.6-fold (maximum) and 4.6-fold (cumulative) relative to abiotic dissolution. Quantitative real-time PCR targeting pceA, the PCE reductive dehalogenase gene of S. multivorans, revealed that S. multivorans cells were present in the NAPL source zone, and increased in numbers (i.e., grew) throughout the source and transition zones. In contrast, minimal reductive dechlorination and microbial growth were observed in the column containing pure PCE-NAPL, where aqueous-phase PCE concentrations reached saturation. These results demonstrate that microbial growth within NAPL source zones is possible, provided that contaminant concentrations remain below levels toxic to the dechlorinating organisms, and that microbial growth can result in significant bioenhanced NAPL dissolution.     

Radionuclide contamination of foods imported into Iraq following the Chernobyl nuclear reactor accident

Since early 1986, a monitoring program for radionuclides in imported foods has been carried out by the Iraqi Atomic Energy Commission. After the Chernobyl nuclear reactor accident in the Soviet Union, the program was expanded; our laboratory was officially designated by the Iraqi Government to measure radionuclide activity concentrations in foodstuff imported from countries known to be severely contaminated by Chernobyl radioactive fallout. Gamma-spectrometric analysis was used. Food items such as powdered milk, lamb meat, poultry, cereals and grains imported into Iraq before the Chernobyl accident did not contain any detectable fission products. However, all lamb meat, 81% of the lentil, 44% of the powdered milk and chick-pea, and 17% of the roast beef samples were contaminated with 137Cs or 134Cs and 137Cs. The highest 137Cs contamination levels found were 82, 147, 420, 6 and 4 Bq kg-1, respectively. Contamination by 134Cs was approximately 50% of the values given above.     

A new mathematical model to evaluate simazine removal in three different immobilized-biomass reactors

A new mathematical model based on the cinetical Langmuir equation is developed to interpret and predict the effectiveness of simazine (SZ) removal in immobilized-biomass reactor (IBR), to consider herbicide-support affinity (Cx), and herbicide-cell affinity (Cy). Three solid supports: sepiolite monolith, granular sepiolite, and alginate were used in pilot-scale reactors that were inoculated with Klebsiella planticola DSZ. The abiotic process was analysed by measuring the SZ sorption capacity of the reactor supports. Sepiolite monolith showed the maximum value for herbicide-support affinity (28.02+/-0.9%). The effectiveness of the biotic process was estimated considering the formation of biomass and SZ biodegradation. Granular sepiolite showed either higher affinity with SZ and viability rate (0.90) throughout the process, and SZ removal rate was 3.39+/-0.06 mg/h. The mathematical model presented in this paper provides useful insights into the interpretation of experimental data as well as prediction for the implementation of biological reactors.     

Metal concentrations in a shallow groundwater aquifer underneath petrochemical complex

Duplicate groundwater samples were collected from 104 monitoring wells (piezometers) from shallow aquifers underneath an industrial city in the Eastern Province of Saudi Arabia. Concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Ti, V, Zn, Ca, Mg, K, Na, Cl, SO₄, alkalinity, salinity, total dissolved salts, and pH were determined in these samples. Analysis of variance showed significantly (p < 0.05) wide variations in the concentrations of the above parameters. The contour maps of metal concentrations indicated that these variations were related to important landmarks in the study area. The results of correlation analyses suggest that geographical as well as chemical factors may influence metal distribution in the groundwater samples. To investigate the geographical effects, the analytical data were normalized (element/Cl ratios were calculated) for chemical variability. As expected, contour mapping of the ratio data of element/Cl of Na, Ca, Mg, K, SO₄, alkalinity, salinity, total dissolved salts, and Sr vary in a relatively small range and did not show a particular geographical trend. The groundwater sample from the industrial-dust area contained higher ratios between concentrations of Cl and Co, Cr, Cu, Fe, Mn, Mo, Ni, Pb, and Zn. These observations clearly suggest an extraneous contamination source, probably industrial dust, in the area. Another geographical area where metal (As, Cd, Cu, Mo, Ni, Ti,and V)/Cl ratios were found to be large was in the vicinity of an oil-refinery. Groundwater samples collected from the vicinity of a fertilizer plant and green-belt area contained relatively higher ratios of Al, Cd, Cr, Co, and Ni. The results of this study suggest that leachate from the industrial dust, leakage from the oil refinery and fertilizer plant, and drainage of irrigation water are some of the important pollution sources in the industrial city.     

The long-term evolutions and the regional characteristics of atmospheric methane concentrations in Nagoya, 1983-1997

This study provides information on the long-term evolutions of the atmospheric methane (CH4) concentrations in Nagoya City, Japan, which were analyzed by using the continuous monitoring data observed at the eight observatory stations for 1983-1997. The 15-year records of the atmospheric CH4 concentrations were examined by means of a time-series analysis using a fast Fourier transform with a low-pass filter to elucidate the seasonal cycles and the long-term trends. The annual averages of the CH4 concentrations in Nagoya were 1.85 ppmv (parts per million by volume), 1.91 ppmv, and 1.90 ppmv in 1988, 1995 and 1997, respectively. Moreover, the annual average growth rate showed a drastic decrease from 17 ppbv (parts per billion by volume) year(-1) in 1992 to 2 ppbv year(-1) in 1993, and further down to 7 ppbv year(-1) in 1997. Comparison of the atmospheric CH4 records in Nagoya with those in global air of the northern hemisphere observed at Mauna Loa observatory in Hawaii, USA, allows us to estimate the excess concentration of CH4 in the urban atmosphere of Nagoya, which was 0.17 ppmv in 1988 and 0.15 ppmv in 1997. On a local scale, the atmospheric CH4 concentrations in the northern part of Nagoya City increased until 1992 and then gradually decreased from 1993 to 1997, although those in the south-western urban areas constantly increased at the averaged growth rate of 13 ppbv year(-1) for 1988-1997. The variation of the long-term trends of the CH4 concentrations in Nagoya may be ascribed to the emission changes from the CH4 sources due to the human activities such as waste dumping and landfills.     

Contamination of soils and plants by mercury as influenced by the proximity to industries in Alexandria,Egypt

The amounts of total Hg in the soils and the edible parts of seven vegetable plant crops grown in unpolluted and polluted soils were studied.The highly polluted soils contained higher levels of Hg (495 ppb) than those in the unpolluted (35 ppb). The topsoil was highly enriched with Hg than the subsoil as the result of the deposition of Hg particulates produced from the industries.Plants grown in soils near industries contained high levels of Hg up to 362 ppb. The amounts of Hg in the plant species which grown in winter were higher than those grown in summer.     

The uptake of chemical elements from coal ash and settling basin effluent by primary producers II. Relation between concentrations in ash deposits and tissues of grasses growing on the ash

A number of reports of biomagnification of trace metals by plants indicate that elements are selectively concentrated within certain tissues when plants grow on coal ash. This study determined the uptake by, and tissue bioaccumulation of, 15 chemical elements within broom sedge and nut grass growing in the drainage system of a coal ash basin. Biomagnification of these elements by the grasses was compared to concentrations of these elements found in duckweed within the same system.Aluminium, arsenic, barium, cadmium, cobalt, chromium, copper, iron, mercury, manganese, molybdenum, selenium, strontium, titanium, and zinc were measured by neutron activation analysis in roots, stems, leaves and fruit of the grasses which grew in sediments within the effluent. Mercury and zinc were biomagnified in both grasses and duckweed to a level exceeding the concentration in sediment. All elements were biomagnified above the water concentration in all parts of the plants. Bioaccumulation of elements in the leaves and fruit of these plants provides a concentrated source of potentially toxic chemical elements for passage to animals which may consume these plants. The mechanisms of movement of potentially toxic elements from coal ash or water into food webs need additional study as utilization of coal is increased.     

The effect of depositional history on contaminated bed sediment stability

Experiments were conducted in an annular flume using a commercially available kaolinite clay as well as contaminated bed sediment from Hamilton Harbour (Ontario) to assess their stability against erosion. Critical shear stress for erosion was measured under different conditions of bed formation (quiescently deposited beds and shear deposited beds) as well as with and without the presence of a biostabilized bed. Results suggest that a biostabilized bed and a bed formed under a flowing condition, similar to a river scenario, will be more resistant against erosion than will a non-biostabilized bed and a bed formed under quiescent conditions. Up to three cycles of erosion and flocculation/deposition were observed to occur within one experiment. These results suggest that the depositional history and biostabilization of river bed sediments need to be seriously considered within sediment and contaminant transport models if meaningful estimates of sediment and contaminant source, fate and effect are to be generated and used for the management of our aquatic ecosystems.     

Gas chromatographic determination of aliphatic amines and quantitative analysis of small amounts of dimethylamine in wastewater

A gas chromatographic procedure has been developed for the determination of small amounts of aliphatic amines in wastewater. Pennwalt 223 was employed as a liquid phase which is selective to amines. Kováts' retention indices are presented for C₁---C₄ mono-, di-, and trialkylamines. Response factors for dialkylamines using the FID detector are given. The linearity of the FID detector over the concentration range 10–4000 mg 1⁻¹ for dimethylamine was also established.