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941.
Chemical and bacterial changes during laboratory conditioning of formulated and natural sediments 总被引:3,自引:0,他引:3
Within the framework of toxicity testing using formulated sediment, a conditioning treatment prior to toxic contamination has been examined. This preliminary step enables the bacterial colonisation of the sediment, the initiation of organic matter degradation, and the establishment of stable biological and physico-chemical conditions. The treatment involved in keeping the formulated sediment under water in conditions similar to that chosen for toxicity tests. The behaviour of a formulated sediment was compared with a natural sediment. The monitoring of physico-chemical and biological parameters of sediment and water column was carried out over a 30-day incubation in two laboratories. The parameters of pH and redox, dissolved organic carbon (DOC), NH4 and NO2, total organic carbon (TOC) were measured. The bacterial community was characterised by the determination of bacterial density, in total bacteria number or colony forming units (CFU), several exoenzymatic activities (P-glucosidase, xylosidase, leucine-amino-peptidase phosphatase and sulfatase activities), and three gas productions (CO2, N2O and CH4). The same experiment was carried out with a natural sediment. A 10- to 15-day conditioning allowed a physico-chemical stabilisation and corresponded to kinetic changes in hydrolysis activities. As compared to data of the natural sediment, the biological activity of the formulated sediment showed a different dynamic with lower activity levels. For both sediments, an important decrease of activities levels was observed after 15 days because of a substrate limitation. The work showed that a preliminary conditioning treatment of a formulated sediment provides the stabilisation of parameters that can affect toxicant bioavailability. Additional research is needed to determine the real influence of conditioning on the bioavailability of contaminants. The possible advisability of organic matter input, to maintain the sediment bacterial activity, has to be studied. 相似文献
942.
Heavy metal extractable forms in sludge from wastewater treatment plants 总被引:17,自引:0,他引:17
The analysis of heavy metals is a very important task to assess the potential environmental and health risk associated with the sludge coming from wastewater treatment plants (WWTPs). However, it is widely accepted that the determination of total elements does not give an accurate estimation of the potential environmental impact. So, it is necessary to apply sequential extraction techniques to obtain a suitable information about their bioavailability or toxicity. In this paper, a sequential extraction scheme according to the BCR's guidelines was applied to sludge samples collected from each sludge treatment step of five municipal activated sludge plants. Al. Cd, Co, Cu, Cr, Fe, Mn, Hg, Mo, Ni, Pb, Ti and Zn were determined in the sludge extracts by inductively coupled plasma atomic emission spectrometry. In relation to current international legislation for the use of sludge for agricultural purposes none of metal concentrations exceeded maximum permitted levels. In most of the metal elements under considerations, results showed a clear rise along the sludge treatment in the proportion of two less-available fractions (oxidizable metal and residual metal). 相似文献
943.
Bioaccumulation and elimination of 14C-lindane in Enchytraeus albidus was studied in artificial OECD soil and a silty loam from an agricultural field in Central West Portugal. Results showed that enchytraeids were able to bioaccumulate the chemical with a kinetic pattern similar to that of earthworms: fast uptake within a few days and a biphasic elimination pattern. A 10 day period to study uptake was sufficient, but a few more days were probably necessary for elimination. Bioaccumulation was influenced by soil type. The authors suggest that higher organic matter (OM) content and also the higher content on sand particles in the OECD soil may have led to a faster elimination: hydrophobic chemicals tend to adsorb to OM being in this way less bioavailable and therefore less bioaccumulated having bioaccumulation factor value around 6 while in natural soil is 10; the sand could act as abrasive particles (helpers) in the elimination process leading to an elimination of 90% of the chemical in two days while in natural soil 67% was eliminated in the same period of time. 相似文献
944.
Huijbregts MA Thissen U Guinée JB Jager T Kalf D van de Meent D Ragas AM Sleeswijk AW Reijnders L 《Chemosphere》2000,41(4):541-573
Toxicity potentials are standard values used in life cycle assessment (LCA) to enable a comparison of toxic impacts between substances. In most cases, toxicity potentials are calculated with multi-media fate models. Until now, unrealistic system settings were used for these calculations. The present paper outlines an improved model to calculate toxicity potentials: the global nested multi-media fate, exposure and effects model USES-LCA. It is based on the Uniform System for the Evaluation of Substances 2.0 (USES 2.0). USES-LCA was used to calculate for 181 substances toxicity potentials for the six impact categories freshwater aquatic ecotoxicity, marine aquatic ecotoxicity, freshwater sediment ecotoxicity, marine sediment ecotoxicity, terrestrial ecotoxicity and human toxicity, after initial emission to the compartments air, freshwater, seawater, industrial soil and agricultural soil, respectively. Differences of several orders of magnitude were found between the new toxicity potentials and those calculated previously. 相似文献
945.
Two experiments were performed to assess the impact of cadmium on the sewage lagoon wastewater treatment process. For each one, three laboratory-scale pilot plants with one tank receiving the same raw effluent were used; one plant served as control and the other two were contaminated once only with cadmium. In the first study, the effects of a shock load of two concentrations of cadmium chloride (60 and 300 micrograms/l) on the plant performance, microbial populations (protists and bacteria) and enzyme activities were determined. Initially, most of the performance parameters were affected concentration-dependently. A reduction in the protist population density and some influence on the total bacterial population were observed, and the potential enzymatic activities were also modified. A second experiment with a lower cadmium concentration (30 micrograms/l), supplied as chloride or sulphate, still perturbed most of the parameters studied, and the effects of the two cadmium salts were identical. 相似文献
946.
The fate of pyrimidine-2-14C-rimsulfuron in a rendzina soil was investigated using a laboratory microcosm approach. Measurement of CO2 evolution suggested that rimsulfuron applied at 5 times the recommended dose did not affect soil respiration. Under abiotic conditions, no mineralization of 14C-rimsulfuron into 14C-CO2 occurred and under biotic ones it was very low reaching 0.75% of the applied 14C-rimsulfuron after 246 days of incubation. The analysis of data showed that a three-half order model provided the best fit for the mineralization curve. Extractable 14C-residues decreased over time to 70-80% of the applied 14C-rimsulfuron at the end of the incubation. After 246 days of incubation, non extractable residues (NER) accounted for up to 24.7% of the applied 14C-rimsulfuron and were distributed according to organic carbon in soil size fractions, suggesting a progressive incorporation process of NER to soil humus. 相似文献
947.
Pérez-Coll CS Herkovits J Fridman O Daniel P D'Eramo JL 《Environmental pollution (Barking, Essex : 1987)》1999,106(3):443-448
Bufo arenarum embryos at the end of their embryonic development were acclimated to cadmium (Cd) by means of a 10-day treatment protocol. Embryos were processed for metallothionein (Mt) isolation and Cd and zinc (Zn) contents were measured. The results showed that: (1) the uptake of Cd in the experimental embryos was 7 microg/g embryo (wet weight) representing a bioaccumulation of Cd 255 times higher than in the maintaining medium; (2) a major Mt-like fraction was Cd-induced 7.8 times that in control embryos; two other protein fractions also bound Cd and Zn but were induced by Cd only about 2 and 1.4 times; (3) the Zn concentration was about 44 microg Zn/g embryo (wet weight) and did not change significantly (p>0.01) in the experimental embryos with respect to controls, but in acclimated embryos the essential metal was released from the Mts. The enhanced Mt synthesis and release of Zn from the native Mts are discussed in relation to the acclimation phenomenon. 相似文献
948.
Ana B. Payá-Pérez Mohammed S. Rahman Helle Skejø-Andresen Bo R. Larsen 《Environmental science and pollution research international》1996,3(4):183-188
The soil/water partition coefficient (Kd) of hexachlorobenzene (HCB) ranged from 220 1/kg to 1800 1/kg for eight soils having a wide range of physico-chemical properties. Kd normalised to soil organic carbon (Koc) was found to be 28000 ± 4800 1/kg. Anionic surfactant dodecylsulphate (DS) present at concentrations above the critical micellar concentration (CMC) caused reductions in the apparent soil/water partition coefficient (Kd *) in the range of 3–26 times for most soils and up to 36–91 times for sandy soils. Below CMC, at environmentally relevant surfactant concentrations, Kd * was reduced by a factor of 1–13. For clay and calcareous soils significant adsorption/complexation/precipitation of DS occurred. At the lowest DS concentration this produced a two-fold increase in Kd *. At increasing DS concentrations this effect was shielded by the solubihzing effect from DS. Monomer (Kmn) and micellar (Kmc) surfactant/water partition coefficients for HCB were determined to be, 980 ± 190 1/kg and 21000 ± 1600 1/kg, respectively. 相似文献
949.
Sjödin A Cooper DA Andréasson K 《Journal of the Air & Waste Management Association (1995)》1995,45(3):186-190
Ambient air measurements of N2O, NOx, CO, and HC based on grab sampling were conducted in a major traffic tunnel in Sweden, that carries up to 4,000 vehicles per hour, in order to estimate real-world emissions of N2O for road traffic. Two different methods--relative and mass balance-were used to calculate a N2O emission factor for the mixed vehicle fleet, which gave an average emission factor, at average speeds of 30-70 km/h, of approximately 25 mg N2O/ km, with a range of 7-56 mg/km. 相似文献
950.
Forsberg A Söderlund S Frank A Petersson LR Pedersén M 《Environmental pollution (Barking, Essex : 1987)》1988,49(4):245-263
Concentrations of eleven metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V and Zn) were determined in the brown seaweed Fucus vesiculosus collected from the Archipelago of Stockholm. Several factors which influence the metal content in the seaweed have been studied, including errors caused by epiphytes, sea exposure and differences depending on which part of the seaweed is analysed. It is concluded that, if all these factors are considered, Fucus vesiculosus plants are excellent bio-indicators of metal pollution. This is also demonstrated by a significant increase in metal content in transplanted Fucus vesiculosus near the city of Stockholm. The results from this investigation also indicate increasing metal concentrations, especially Cd, in samples from the northern parts of the Archipelago and the reason for this is discussed. 相似文献