A base for building codes and construction methods in karst-prone regions

The history of the development of methodical and regulatory documents relative to construction in karst-prone areas is cited. The basic content of existing regulatory documents is presented, and attention is focused on some of their deficiencies. Specific approaches to the development of a standard for construction in karst-prone areas are proposed. __________ Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 6, pp. 21–24, November–December, 2006.     

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.     

Organochlorine insecticides and PCB'S in sediments of Lake St. Claire (1970 and 1974) and Lake Erie (1971).

Sediments were collected on a grid from Lake St. Clair in 1970 and 1974 and from Lake Erie in 1971 and analysed for organochlorine insecticides and PCBs. Suspended solids were centrifuged from pumped water in the Detroit River in 1974. Residues of DDE, TDE and DDT were highest in sediment from the Western Basin (70.3 ppb) Lake Erie and lowest in sediment from Lake St. Clair (6.6 ppb in 1970 and 2.6 ppb in 1974). The Central and Eastern Basins of Lake Erie contained residues that fell about mid-way between these means. TDE was the predominant component of ΣDDT and was followed by DDE at approximately half this residue. While DDT represented the lowest component in lake sediments, it was the highest component in suspended solids from the Detroit River.HEOD was present in the entire lake system but at only a fraction of the level of ΣDDT. The mean residue in Lake St. Clair was only 0.1 ppb while Lake Erie sediments contained 1–2 ppb. The highest mean residue (3.6 ppb) was in suspended solids in the Detroit River. Other organochlorine insecticides were only occasionally identified.PCB residues in sediment were approximately 3 times higher than the total organochlorine insecticide residue, being highest in the Western Basin (252 ppb) and lowest in Lake St. Clair (19 ppb in 1970 and 10 ppb in 1974). The Detroit River and Central and Eastern Basins of Lake Erie had intermediate residues.Residues in Lake St. Clair indicated a decline in ΣDDT, HEOD, and PCB residues between 1970 and 1974, and this coincided with the restrictions on the materials. A core sample from the Western Basin of Lake Erie indicated that ΣDDT, HEOD and PCB began to accumulate in sediments in 1958, 1953, and 1956, respectively. This appeared to indicate a lag period of 2–5 years after wide-spread use occurred.     

Biodegradation of urea in river waters under controlled laboratory conditions

The biodegradation of urea in river waters has been evaluated under laboratory conditions. Urea will degrade to ammonia at a rate depending on the bacterial state of the river water and on the water temperature. Under normal conditions no breakdown may be expected to occur at temperatures below 8°C for 14 days contact. In river waters with a high suspended solids content, simulating extreme winter river conditions, a maximum breakdown of 3–6 per cent daily of the original urea levels was found for temperatures not exceeding 8°C during the first 7 days contact.     

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.     

Congratulations to Valerii Viktorovich Mikheev

Anniversaries and Memorable Dates

Congratulations to Valerii Viktorovich Mikheev Candidate of Technical Sciences, honorable builder of the Russian Federation, and recipient of the prize awarded by the Council of Ministers of the USSR     

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 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.