摘要:

Reduction of sulfate found in barite (BaSO4), sodium sulfate (Na2SO4) and phosphogypsum (CaSO4• xH2O) and the significance of sulfide production in the sequester of selected heavy metals and trace elements were studied. Suspensions of Mississippi River alluvial sediment were equilibrated under controlled redox (‐250 mV) conditions. Sodium sulfate and phosphogypsum additions resulted in a large increase in sulfide levels in the sediment suspensions. Water soluble barium (Ba), cadmium (Cd), iron (Fe), and manganese (Mn) concentrations decreased significantly when sodium sulfate and phosphogypsum were the sulfate sources. Solubility of heavy metals and trace elements was substantially affected. Barite addition did not significantly affect the concentrations of water soluble sulfate and sulfide formation. This was attributed to the low solubility of barite as compared to the two other sulfate sources.

ISSN:1093-4529    

DOI:10.1080/10934529809376715

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Dissolved concentrations of seven metals (As, Pb, Cd, Zn, Ni, Cu, Cr) were determined monthly at six sampling stations in Lake Chapala, Mexico, between November 1990 and December, 1991. Lake Chapala is the largest lake in Mexico, and serves as a source of drinking water and an economically important fishery and center for tourism. Historically, Lake Chapala has received poorly characterized domestic, industrial, and agricultural wastes. As, Cd, Pb, Cr, and Zn displayed peaks in concentration during the period before the rainy season due, presumably, to evaporation. Comparison of inflow and outflow concentrations also indicated a direct source of As to the lake. During this period, the concentrations of both Cd and Pb were above the freshwater chronic criteria values recommended by the United States Environmental Protection Agency for protection of aquatic ecosystem health. The metals As, Cr, Zn, Ni, and Cu also showed concentration peaks following the rainy season in August and September, perhaps due to increased input from the watershed or resuspension of metals in the lake driven by changes in water circulation patterns. Concentration data for the lake also suggested that a portion of the inflow water does not immediately mix with the lake as a whole, creating spatial gradients depending on the concentration of metals in the source water. Determination of metals in water hyacinth (Eichornia crassipes,) plant tissue showed large partitioning of metals into root tissue, indicating that plants may be an important temporal sink for metals. In addition, copper and zinc accumulated to very high levels in Tilapia and Carp livers, indicating that some of the metal contaminants are entering the food chain.

ISSN:1093-4529    

DOI:10.1080/10934529809376716

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This study reports on the uptake, potential bioavailability and phytotoxicity of arsenic (As) to an important wetland plant species growing in the vicinity of produced water discharge. The effects caused by As chemical form and concentration on growth, tissue concentrations and distribution of As and nutrient elements were studied inSpartina patens, growing in hydroponic conditions. A 4 × 3 factorial experiment was conducted with treatments consisting of four As chemical forms [arsenite, As(III); arsenate, As(V); monomethyl arsonic acid, MMAA; and dimethyl arsinic acid, DMAA] and four As concentrations (0, 0.2, 0.8, and 2.0 mg As.L‐1). Arsenic phytoavailability and phytotoxicity were primarily determined by the As chemical form present in the nutrient solution. DMAA was the most phytotoxic species to this marsh grass. As(V) and MMAA significantly increased total dry biomass production at low As rates of application. Arsenic availability followed the trend DMAA << MMAA ? As(V) < As(III). The As concentrations in root and shoot were significantly increased by increasing As application rates (all four species) to the rooting medium. Inorganic arsenicals and MMAA were mainly accumulated in roots, while DMAA was readily translocated to shoots. Arsenic chemical form and concentration significantly affected macro‐and micro‐nutrient concentrations in plant tissue. Plants treated with As(V) had an improved growth compared to control plants; this seemed to be associated to an increase in plant P concentrations. Organic arsenicals caused the highest Na root concentrations and simultaneously the lowest plant K levels (antagonism K‐Na). A significant decreased in leaf Ca concentrations was found in practically all As treatments. Organic arsenicals significantly decreased the concentrations of root Cu, Fe, and Mn and shoot B and Cu. The high phytotoxicity of the DMAA treatments appears to be related to the significant reductions in the concentrations of several essential macronutrients P, K, Ca, and Mg and micronutrients B, Cu, Fe, and Mn.

ISSN:1093-4529    

DOI:10.1080/10934529809376717

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Phosphorus (P) losses to surface bodies of water both via surface runoff and via drainage tiles is considered a very important environmental issue because it is the nutrient limiting agent for aquatic vegetation. Therefore, understanding the mechanisms by which P is transported to the aquatic environment is a very vital subject. Movement of phosphorus and bromide (Br) was studied in seven undisturbed soil monolith lysimeters containing clay soil collected at Oxelby near Stockhohn, Sweden. They were exposed to natural climatical conditions for the period 30 November 1993 through 6 May 1996. Drainage samples were collected on a weakly basis and flow discharge was measured at the same time. Results showed that preferential flow processes dominated the loss of Br through all seven lysimeters. Phosphorus losses, mainly in the particulate form, showed high variability and was shown to be flux dominated as well. The results indicated that rainstorms had to reach a certain intensity to initiate total P and particulate P losses which was a proof for dependency of P losses to flux in this heavy textured soil.

ISSN:1093-4529    

DOI:10.1080/10934529809376718

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This study was undertaken to measure the aerobic biodegradation of phenol using poultry litter and to compare the toxicity of the parent compound with the end product(s). Phenol was aerobically treated with a water extract of the untreated litter or of irradiated litter in order to differentiate between the effects of the microorganisms and other chemical species present in the litter on the biodegradation of phenol. Two concentrations of phenol (10 ppm and 100 ppm) were each treated with three concentrations of leachate (0.2%, 0.5% and 1%). The litter leachate (1%) degraded 10 ppm and 100 ppm phenol by 88% in 8 h and 24 h, respectively. Lag phases were observed for all treatments except with 1% leachate. The lag phase increased as the concentration of phenol increased and decreased with an increase in the leachate concentration. No degradation was observed using the leachate of the irradiated litter. Experiments usingCeriodaphnia dubia, (LD50) andVibrio fischeri, (EC50) showed that the degradation end product (s) were non‐toxic compared with the parent compound.

ISSN:1093-4529    

DOI:10.1080/10934529809376719

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Conventional biological treatment of intermittently flowing wastewaters is one of the significant problems of regions having seasonal activities. A system consisting of an downflow aerated packed reactor (DAPR) followed by inclined tube settler (ITS) was tried to overcome the difficulties for the above mentioned wastes. The DAPR‐ITS system can be regarded as a combination of activated sludge and trickling filter process followed by a high rate sedimentation unit (ITS). Three different no‐feed periods ranging from 3 to 26 weeks were used to characterize the off‐season activities. After this no‐feed period the system was started using different flow rates. The performance of the system was evaluated using chemical oxygen demand (COD), biochemical oxygen demand (BOD), nitrogen (N), phosphate (P) and total suspended solids (TSS) parameters. The results showed that DAPR‐ITS achieved about 80 % COD removal efficiency from the time of starting the system and reached steady state conditions within a few days. The removal efficiencies of other parameters had similar trends as COD. Thus, DAPR‐ITS system has been proven to be a satisfactory method for intermittently flowing wastewaters.

ISSN:1093-4529    

DOI:10.1080/10934529809376720

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A step‐by‐step design approach for sizing anoxic/oxic single‐sludge activated sludge systems is presented. A computer model utilizing an EXCEL spreadsheet was also developed which simulates the pre‐denitrification single‐sludge activated sludge process. The biokinetic equations developed by Lawrence and McCarty are utilized in the model. The model was calibrated using data from a full‐scale, pre‐denitrification activated sludge process. Two‐tailed, paired comparison Student's “t‐test”; performed on effluent BOD5, SS, TKN, NH3‐N, NO3‐‐N, and TN indicated there was no significant difference between the actual effluent concentrations and those predicted by the model at a 95 percent confidence level.

ISSN:1093-4529    

DOI:10.1080/10934529809376721

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The early effects of chronic low level exposure to gasoline vapours and organic solvents on kidney function have been difficult to identify. This study has attempted to identify markers, indicating a risk of kidney dysfunction, which might be useful tools for alerting occupational physicians to the early reversible changes so that preventive measures can be introduced to halt irreversible kidney damage. The exposed group in this study comprised 86 workers occupationally exposed to gasoline vapours and organic solvents in garages; the non‐exposed group was 86 workers not occupationally exposed to the same substances. Exposed workers were matched with non‐exposed by age and nationality. The mean age of the sampled population was 37.4±7.63 years. Current smokers formed 40.7% of the whole population and the percentages among exposed and non‐exposed were broadly similar.

ISSN:1093-4529    

DOI:10.1080/10934529809376722

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Volatile organic compound (VOC) emissions from the combustion of household refuse were investigated in a 20 kW experimental boiler with a stationary grate. Swedish household refuse from kitchens was manually fed into the combustion chamber. The oxygen fraction ranged from 0.068 to 0.136 on dry basis. The gas temperature in the chamber center ranged from 860 to 980 K. The measurements made included volatile organic compounds (VOCs), carbon monoxide and carbon dioxide. The identification and analysis of organic pollutants were performed by thermal desorption Gas Chromatography and Mass Spectrometry (GC/MS) with a Tenax sampling train. The major organic emissions identified were toluene and various benzenes. Total volatile organic compound (TVOC) emissions were between 2.85 and 8.31 mg/Nm3. The concentration of toluene was up to 93.82 μg/Nm3, which corresponded to the lowest oxygen fraction, 0.068, and highest carbon monoxide emission, 606 mg/Nm3on average. In general, the emissions of organic pollutants increase with the decrease in oxygen fraction. This may have been due to oxygen deficiency which results in incomplete combustion. For naphthalene and phenol, the concentration were very low, in a range between 0.12 and 0.60 μg/Nm3. The emission pattern was not so clear and more data are needed.

ISSN:1093-4529    

DOI:10.1080/10934529809376723

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1093-4529    

DOI:10.1080/10934529809376714

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor