Уточнить поиск
Результаты 311-320 из 424
Trace Element Concentrations in Saltmarsh Soils Strongly Affected by Wastes from Metal Sulphide Mining Areas
2008
Soil and water samples were analysed for trace metals and As in two watercourses and 14 sampling plots in a salt marsh polluted by mine wastes in SE Spain. Groundwater levels, soil pH and Eh were measured 'in situ' for a 12-month period in each sampling plot, and total calcium carbonate was also determined. Low concentrations of soluble metals (maximum Mn 1.089 mg L-¹ and maximum Zn 0.553 mg L-¹) were found in the watercourses. However, total metal contents were extremely high in the soils of a zone of the salt marsh (maximum 1,933 mg kg-¹ of Mn, 62,280 mg kg-¹ of Zn, 16,845 mg kg-¹ of Pb, 77 mg kg-¹ of Cd, 418 mg kg-¹ of Cu and 725 mg kg-¹ of As), and soluble metals in the pore water reached 38.7 mg L-¹ for Zn, 3.15 mg L-¹ for Pb, 48.0 mg L-¹ for Mn, 0.61 mg L-¹ for Cd and 0.29 mg L-¹ for As. Variable concentrations with depth indicate a possible re-mobilisation of the metals, which could be related to spatial and temporal variations of water table level, pH and Eh and to the presence of calcium carbonate. A tendency for the Eh to decrease in the warmest months and to increase in the coldest ones was found, especially, in plots that received water with a high content of dissolved organic carbon. Hence, the existence of nutrient effluent-enriched water may modify the physical-chemical conditions of the soil-water system and influence metal mobility.
Показать больше [+] Меньше [-]Mobility and Availability of Copper in Agricultural Soils Irrigated from Water Treated with Copper Sulfate Algaecide
2008
Salam, D. | El-Fadel, M.
In this paper, downward movement and availability of copper in soils irrigated with CuSO₄ algaecide treated water were examined using column leaching experiments. Two simulations considering 1 and 10 years irrigation period were conducted at copper application rate of about 18.7 kg CuSO₄/ha/year. Effluent copper concentrations and vertical distribution of acid and DTPA-extractable copper in the soil columns were determined. Nearly 99% of the applied copper was retained in the soil with a C e/C ₀ values on the order of 10⁻³. Retention profiles showed that copper was retained in the upper 2 to 3 cm of the soil. However, a significant fraction of the retained copper was detected in available form (DTPA-Cu) suggesting that plants toxicity could be a major limitation for the use of CuSO₄ treatment in irrigation water.
Показать больше [+] Меньше [-]Sources of Alkylphenols and Alkylphenol Ethoxylates in Wastewater--A Substance Flow Analysis in Stockholm, Sweden
2008
Månsson, N | Sörme, L | Wahlberg, C | Bergbäck, B
This is a study of the sources of alkylphenol and alkylphenol ethoxylates in wastewater, including the new observation that the main contribution is from textiles. Alkylphenols and alkylphenol ethoxylates are widely used chemicals in various applications that are partly under environmental restrictions within Europe. The study sets out to analyze the most important sources of this large group of organic compounds in an urban wastewater system. A substance flow analysis (SFA) of the technosphere in Stockholm, Sweden in 2004 was conducted, allowing a comparison of 13 groups of goods' emissions to wastewater. It was found that the groups of textiles and cleaning agents were the major sources to wastewater, while the group's personal care products and paint and lacquers give smaller contributions. The content of alkylphenol ethoxylates in goods, especially in textiles, is a most significant source and is probably valid for other urban areas as well.
Показать больше [+] Меньше [-]Effect of Cell-to-matrix Ratio in Polyvinyl Alcohol Immobilized Pure and Mixed Cultures on Atrazine Degradation
2008
Siripattanakul, Sumana | Wirojanagud, Wanpen | McEvoy, John | Khan, Eakalak
Atrazine biodegradation by immobilized pure and mixed cultures was examined. A pure atrazine-degrading culture, Agrobacterium radiobacter J14a (J14a), and a mixed culture (MC), isolated from an atrazine-contaminated crop field, were immobilized using phosphorylated-polyvinyl alcohol (PPVA). An existing cell immobilization procedure was modified to enhance PPVA matrix stability. The results showed that the matrices remained mechanically and chemically stable after shaking with glass beads over 15 days under various salt solutions and pH values. The immobilization process had a slight effect on cell viability. With the aid of scanning electron microscopy, a suitable microstructure of PPVA matrices for cell entrapment was observed. There were two porous layers of spherical gel matrices, the outside having an encapsulation property and the inside containing numerous pores for bacteria to occupy. J14a and MC were immobilized at three cell-to-matrix ratios of 3.5, 6.7, and 20 mg dry cells/mL matrix. The atrazine biodegradation tests were conducted in an aerobic batch system, which was inoculated with cells at 2,000 mg/L. The tests were also conducted using free (non-immobilized) J14a and MC for comparative purpose. The cell-to-matrix ratio of 3.5 mg/mL provided the highest atrazine removal efficiency of 40-50% in 120 h for both J14a and MC. The free cell systems, for both cultures, presented much lower atrazine removal efficiencies compared to the immobilized cell systems at the same level of inoculation.
Показать больше [+] Меньше [-]Substance Flow Analyses of Organic Pollutants in Stockholm
2008
Jonsson, A | Fridén, U | Thuresson, K | Sörme, L
This paper summarizes substance flow analyses for four organic substances in the City of Stockholm, Sweden: diethylhexyl phthalate (DEHP), alkylphenolethoxylates (APEO), polybrominated diphenylethers (PBDE) and chlorinated paraffins (CP). The results indicate that the stocks of APEO, PBDE and CP all are approximately 200-250 tonnes, whereas the DEHP stock is two orders of magnitude larger. Emissions can be linked to imported consumer goods such as electronics (PBDE) and textiles (APEO), and to construction materials (DEHP, CP). For several of the substances considerable amounts remain in the technosphere for a long time, even after use of the substance in new products has been eliminated. For example, the use of DEHP as plasticizer for PVC plastics in cables and floorings has more or less been phased-out, but still these applications make up a stock of some 20,000 tonnes (85% of the total DEHP stock in Stockholm) and emit 28 tonnes of DEHP annually (93% of overall emissions). Likewise, the use of chlorinated paraffins in sealants has been radically reduced, but there are 170 tonnes of CP in sealants in Stockholm making up 75% of the stock, and causing half of the emissions to water and air. These emissions are likely to continue for decades, and the stocks therefore have to be considered when analysing and managing the impact of urban substance flows on the environment.
Показать больше [+] Меньше [-]A Multiscale Approach for Assessing the Interactions of Environmental and Biological Systems in a Holistic Health Risk Assessment Framework
2008
Georgopoulos, Panos G
Advances in computing processing power and in availability of environmental and biological data have allowed the development and application of comprehensive modeling systems that utilize a holistic, integrated, approach for assessing the interactions of environmental and biological systems across multiple scales of spatiotemporal extent and biological organization. This approach allows mechanism-based environmental health risk assessments in a person-oriented framework, which accounts for simultaneous exposures to contaminants from multiple media, routes, and pathways. The conceptual basis and example applications of the Modeling ENvironment for TOtal Risk (MENTOR), and the DOse-Response Information ANalysis system (DORIAN) are presented.
Показать больше [+] Меньше [-]Biomass and Cu and Zn Uptake of Two Turfgrass Species Grown in Sludge Compost-soil Mixtures
2008
Hua, Li | Wang, Yunlong | Wu, Weixiang | McBride, Murray B. | Chen, Yingxu
Two kinds of common turfgrass, fescue and ryegrass, were grown in soils amended with 20 x 80% sludge compost (SC) in this research. The effects of SC on two kinds of soil and response of fescue and ryegrass to the SC amendment were studied. The results showed that urease activity, extractable content of Cu and Zn and Electrical conductivity of both soils increased while pH decreased with the increase of SC amendment. However, the change of these parameters also depended strongly on soil characteristics. Sludge compost at the <=40 and <=60% levels can improve growth of fescue and ryegrass, respectively. The biomass of fescue grown in substrate with 40% SC increased 27% in a red soil and 44% in a yellow loamy soil compared to the control. The biomass of ryegrass grown in substrate with 60% SC increased 120% in the red soil and 86% in the yellow loamy soil. Sludge compost amendment at these levels did not significantly affect soluble salt contents of soil or Cu and Zn in plant tissue. Therefore, rational use of sludge compost can take advantage of its beneficial effect as a nutrient source for plant production while avoiding the potential deleterious effects on soil and plant.
Показать больше [+] Меньше [-]Characteristic Variation of Concentration and Chemical Form in Sulfur, Nitrate, Ammonium, and Chloride Species Observed at Urban and Rural Sites of Japan
2008
Aikawa, Masahide | Hiraki, Takatoshi | Mukai, Hitoshi | Murano, Kentaro
A field survey on the concentration of chemical species in particulate matter and gaseous compounds at two monitoring sites with different site classifications (urban and rural) was conducted over three years. Total (particulate matter + gaseous compounds) concentrations at the rural site were significantly lower than those at the urban site for all species (sulfur [graphic removed] and SO₂(g)), nitrate [graphic removed] and HNO₃(g)), ammonium [graphic removed] and ammonia (NH₃(g)), and chloride (Cl⁻ (p) and HCl (g))), which is thought to reflect classification of the site. The difference in the sulfur concentration at the urban and rural sites was characterized by the difference in SO₂ (g) concentration. Further, a clear seasonality was observed for the nitrate species. The HNO₃ (g) concentration was high in the summer compared with other seasons at both the urban and rural sites. The [graphic removed] concentration levels were approximately the same as those of NH₃ (g) at both sites. The molar ratios of the particulate matter concentration to the total concentration showed different characteristics; the nitrate, ammonium and ammonia, and chloride species showed a clear seasonal variation: low in summer and high in winter and the values were similar regardless of the site. On the other hand, the sulfur species showed constant values at both the urban and rural sites, however the concentrations were significantly different for the two sites. Ammonium accounted for the largest proportion of cations in the particulate matter, regardless of the site classification. In contrast, [graphic removed] accounted for the largest proportion of anions at the rural site, whereas [graphic removed] was comparable to [graphic removed] at the urban site. Ammonia accounted for the largest proportion of all chemical species at both sites. Seasonal analysis of the proportional distribution in particulate matter and gaseous compounds provides information on atmospheric conditions.
Показать больше [+] Меньше [-]100 years of Sediment History of Heavy Metals in Daya Bay, China
2008
Du, J. Z. | Mu, H. D. | Song, H. Q. | Yan, S. P. | Gu, Y. J. | Zhang, J.
The estuarine and coastal system plays an important role of sedimentation deposition which acts as sink of particle associated contaminants such as heavy metals and polycyclic aromatic hydrocarbons. Sediments conserve important information about past conditions of its aquatic environments. The chronology was developed by using the accumulation rates determined previously from ²¹⁰Pb analyses of the same core. Then, the concentrations of Cr, Cu, Fe, Hg, Mn, Ni, Pb, V and Zn were determined in dated (²¹⁰Pb chronology) sediment cores from four stations (W₀, W₂, W₆, W₉) around the Daya Bay of Guangdong Province (China), where the first nuclear power station of China has been running from 1994. Based on sediment flux (g·cm⁻²·year⁻¹) obtained from the chronologies of ²¹⁰Pbex, the flux of heavy metals were calculated. The increasing of both sediment flux and pollution concentration resulted in the increasing of heavy metals flux (mg·cm⁻²·year⁻¹) from last century. The experimental data showed that the average values of heavy metals are 18.6, 0.035, 32.9, 38.1, 10.6, 74.9, 4.1, 29.1 x 10³ and 543 mg/kg for As, Cd, Cr, Pb, Cu, Zn, Co, Fe and Mn, respectively. The concentration of As, Pb, Zn, total organic carbon (TOC) and total nitrogen (TN) in cores are clearly higher than those of natural abundance. Those results indicate that there is pollutant of As, Pb, Zn, TOC and TN in the studying area. The significant relationships between organic C and As, Cr, Pb, Zn, N indicated that such metals are mainly delivered to Daya Bay sediments from a common source.
Показать больше [+] Меньше [-]Dissolved Silica Retention and Its Impact on Eutrophication in a Complex of Mountain Reservoirs
2008
Koszelnik, Piotr | Tomaszek, Janusz A.
This paper reports on studies conducted during 2005 in the ecosystem of the Solina-Myczkowce mountain complex of mesotrophic reservoirs on the San River, SE Poland. Of the 1,950 t of dissolved silica calculated to flow into the reservoirs in the course of the year, c. 20% of the load was retained in the reservoirs. However, most of this retention took place in the lower Myczkowce Reservoir. Far-reaching depletion to below 10 μM L-¹ of silicate was noted during the summer in the epilimnetic waters of the two reservoirs. In turn, the hypolimnion was seen to go through an enrichment process connected with sedimentation and releases from sediment. The observed depletion causes a decrease in the DSi:DIP ratio in the euphotic zone of the reservoirs, with simultaneous growth of non-siliceous algae expressed as chl a concentration.
Показать больше [+] Меньше [-]