摘要:

This screening modeling analysis examines mercury sources and fate in the upper canals of the South Florida Everglades. Mass balance modeling techniques are applied along with available data to examine the relative importance of external sources and internal cycling of mercury and the relative influence of several transport and transformation processes. WASP5, a general dynamic mass balance model for aquatic systems, was modified to represent elemental mercury, divalent mercury, and methyl mercury. A new soil mercury mass balance model was developed to track the transport of these mercury components from soil surfaces to the water via surface runoff. Subsurface flow (drainage) loads were estimated on a seasonal basis using information from a modified simulation model for muck soil hydraulics and transport. Predicted mercury concentrations in the Everglades Agricultural Area (EAA) canals were compared to observed data provided by a region‐wide statistical sampling program. The modeling system reproduced the average mercury dynamics observed in the EAA canals during four surveys within a 2‐year period. Results indicate that despite the complexity of the upper South Florida Everglades ecosystem, the modeling system provides a plausible description of the average mercury dynamics in the EAA canals. Mercury concentrations in the canals appear to be dominated by runoff loading events from the EAA during the wet season, and by subsurface flow (drainage) loading between events and during the dry season. Predicted mercury concentrations in water leaving the EAA are similar to or slightly less than average concentrations in downstream marsh environments for most of the year. Predicted concentrations following large rainfall events, however, are significantly higherthan concentrations in the downstream marsh. These results must be considered as tentative due to the screening‐level character of the modeling study. They point to more detailed field monitoring and process studies which could confirm these findings.

ISSN:1093-4529    

DOI:10.1080/10934529809376746

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The effect of chromium (Cr) and lead (Pb) on degradation of South Louisiana Crude oil in sediment collected from a produced water discharge site was measured in laboratory microcosms under oxidized and reduced conditions. Chromium was added to the sediment at rates of 0 to 5,000μ,g, g‐1sediment. Lead was added at rates from 0 to 2,500μ,g, g‐1sediment. The effect on degradation of alkane petroleum hydrocarbon fractions was determined over time. Metal content had no impact on total hydrocarbon degradation content based on changes in concentration. Even on a percentage basis, which normalizes for differences in hydrocarbon concentrations no statistical influence of Cr (5,000μ,g, g‐1) and Pb (2,500μ,g, g‐1) on degradation could be measured under reducing conditions. A more sensitive analysis of metal impact on degradation depicted by an analysis of reduction of selected alkane fractions also showed little effect on degradation. Only degradation of octadecane was shown to be statistically inhibited at 5,000μ,g g‐1of added Cr and only under reducing conditions. The sediment, due to the clay content, sequested much of the added metals. Under reducing conditions, 25 percent of water soluble and exchangeable Cr and Pb remained in solution at the highest Pb (2,500μg, g‐1) and Cr (5,000μg, g‐1) levels compared to oxidized sediments. The amount in solution was not great enough to impact hydrocarbon degradation. The study demonstrates that Cr and Pb entering sediment at this produced water site would have minimal impact on degradation rates unless extremely high levels were added.

ISSN:1093-4529    

DOI:10.1080/10934529809376747

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Nitroglycerin or glycerol trinitrate (GTN) is an energetic and toxic substance with a wide range of military and pharmaceutical applications. Studies conducted with activated sludge showed that GTN is amenable to aerobic degradation only in the presence of a primary carbon source, such as glucose. Kinetic experiments indicated that GTN is an inhibitory substrate whose presence during biodegradation, reduces substantially the microbial yield and the apparent maximum specific growth rate coefficient of primary substrates. However, in the range of concentrations tested (50 to 200 mg/L of GTN) its inhibitory effects are reversible. The biodegradation mechanism proceeds via a set of successive denitration reactions to form isomers of glycerol dinitrate (1,2‐GDN and 1,3‐GDN) and glycerol mononitrate (1‐GMN and 2‐GMN), which are subsequently degraded. Significant regioselectivity was observed during denitration of GTN and 1,2‐GDN favoring production of 1,3‐GDN and 1‐GMN. The rates of degradation of the metabolic products of GTN were slower at each denitration step with 2‐GMN exhibiting the lowest denitration rate. Aerobic GTN degradation ceased upon exhaustion of the primary substrate. Although, cosubstrate requirements during aerobic bioconversion of GTN were relatively high, in field applications the need for addition of external carbon sources will be minimal since GTN waste streams usually contain high amounts of BOD.

ISSN:1093-4529    

DOI:10.1080/10934529809376748

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Sludge from the Sipraya treatment plant (Thailand) was mixed at 1090, 1340, and 2680 ton/ha with two representative Thai soils (Rangsit and Thonburi) to study sludge‐soil chemistry (heavy metals and nutrients solubility and availability). Mean concentrations of cadmium (Cd), copper (Cu), zinc (Zn), iron (Fe), and manganese (Mn) in this sewage sludge were within the norms for application to agricultural soils as reported by the US Environmental Protection Agency; both soils contained low indigenous concentrations of heavy metals. Soil‐solution data indicated that chemical properties of a sludge‐soil mixture depended not only on the soil, sludge, and its application rate, but also on the sludge‐soil interactions. Soil pH increased and tended to hold steady near neutrality in the Rangsit soil; pH value more suitable for plant growth than the initial one. Sludge application significantly increased available concentrations of plant macronutrients: phosphorus (P), potassium (K) and heavy metals: Cd, Cu, Zn, Fe, and Mn in both soils; it is important to point out the fact that Cu, Zn, Fe, and Mn are also essential plant nutrients. When heavy metal fractionation was studied, most of these chemical elements initially present as easily mobile pools were later (12 weeks of incubation) converted into sparingly mobile fractions, decreasing risks of heavy metal toxicity.

ISSN:1093-4529    

DOI:10.1080/10934529809376749

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Sulfate status in soil solution at various depths in the vadose zone and in surficial groundwater were evaluated in sandy soils under intensive citrus production in central Florida. Sulfate in the vadose zone was evaluated using soil solution sampled from suction lysimeters at 60, 120, and 240 cm depths. Sulfate distribution and movement in the soil profile were closely monitored following the fertilizer application by weekly profile soil sampling up to the depth of soil groundwater interface. Sulfate status was evaluated by sampling the surficial aquifer either using a monitor well at the top 150 cm depth or using a multi‐level sampler at 60 cm intervals at the top 600 cm depth. The sulfate concentrations in the soil solution occasionally exceeded the maximum contaminant level (MCL), i.e., 500 mg SO4‐2L‐1Soil profile sulfate distribution data indicated rapid downward movement of sulfate following the application of fertilizer mixture containing sulfate as sulfate of potash magnesia. However, sulfate concentrations in the surficial groundwater collected from depth‐specific monitoring wells and multi‐level sampling wells ranged from 60 to 240 and 6 to 325 mg SO42‐L‐1respectively. Therefore, the sulfate loading from the vadose zone was diluted in the surficial groundwater.

ISSN:1093-4529    

DOI:10.1080/10934529809376750

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Diesel fuel oil A, which approximates ASTM No. 2D oil was used as the test oil to investigate the influences of the content of sodium sulfate in diesel oils on the combustion and emission characteristics of industrial furnaces. An emulsifying and homogenizing machine was employed to stir the Na2SO4powder and the oil to constitute a homogeneous oil mixture. The oil mixture was there after injected by an oil pump of a small‐sized industrial burner, atomized with inlet air, and burned within a furnace made of stainless steel 316 in turn. The results show that the existence of sodium sulfate in the oil would incur a less extent of chemical reaction, leading to decreased heat release, a lower attainable gas temperature and a lower combustion efficiency. In contrast, the concentrations of excess oxygen, carbon monoxide in the combustion products increased with the existence of sodium sulfate. Larger formations of sulfur dioxide and carbon dioxide were also observed. In addition, the existence of sodium sulfate resulted in lower nitrogen oxides emission probably due to both the lower burning gas temperature and the larger suppression effect of SO2.

ISSN:1093-4529    

DOI:10.1080/10934529809376751

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The kinetics of ammonia oxidation by ferrate(VI) was determined as a function of pH (7.5–11.0) and temperature (10–35 °C). The rates decrease with increase in pH. The pH dependence is probably related to protonation of ferrate(VI) and ammonia. The theoretical curve through data gave the rate constants; k7(HFeO4‐+ NH4+) = 8.46±0.50x10‐1M‐1s‐1; kg(FeO42‐+ NH4+) = 1.26±0.11x10‐1M‐1s‐1; k10(FeO42‐+ NH3) = 1.19±0.10x10‐1M‐1s‐1. The activation parameters, ?H?and ?S?were found to be 67.3 ± 3.5 kJ/mol and 33.1 ± 0.2 J/mol.K, respectively. When ferrate(VI) was used in excess relative to ammonia in the oxidation reaction, 22 % of ammonia removal was achieved. The usefulness of ferrate(VI) to remove ammonia from wastewater is discussed.

ISSN:1093-4529    

DOI:10.1080/10934529809376752

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this work the treatment of leachate originating from an old landfill was compared using a variety of methods both singularly and in combination. Aerobic biological treatment gave a COD removal ranging from 32–35%, but it was very effective for BOD and ammonia removal (97% and 99%, respectively). By using chemical oxidation a COD reduction up to 33% was achieved. The application of chemical precipitation gave a COD removal in the range of 36–42%. The combination of biological and chemical oxidation, biological oxidation and chemical precipitation or chemical oxidation and chemical precipitation, led to a COD reduction up to 57%. The best results were obtained when a biological oxidation was applied in two stages combination with chemical oxidation and chemical precipitation reducing COD concentration values up to 87%.

ISSN:1093-4529    

DOI:10.1080/10934529809376753

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Scapania undulata, (an aquatic liverwort) growing under various pH conditions was analysed for metals. Concentrations of Al and Mn were higher in plants from neutral habitats than in those from acidic habitats. Localization of Al in the leaves of the liverworts was observed by staining. Al was found to be associated with the cell wall of 5.undulata, from neutral habitats. These results indicate the presence of binding sites on the leaf surface for which metal ions compete with H+.

ISSN:1093-4529    

DOI:10.1080/10934529809376754

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The surfactant wastewater treatment by electro‐chemical oxidation with or without peroxide hydrogen was investigated. The two anionic surfactants studied here were alkylbenzene sulfonate (ABS) and linear alkylbenzene sulfonate (LAS), both of them being widely used in the household and industrial detergents. Experiments were conducted to examine the effects of pH, electrolyte concentration, time of electrochemical oxidation, power input and amount of hydrogen peroxide (H2O2) on the surfactant removal and other water quality parameters. Optimum operating conditions were experimentally determined. The enhanced version of electrochemical oxidation (i.e. with addition of hydrogen peroxide) was found to be significantly more efficient than that without.

ISSN:1093-4529    

DOI:10.1080/10934529809376755

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor