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1.
G. Darko M.Sc. S. O. Acquaah 《International Journal of Environmental Science and Technology》2007,4(4):521-524
Concentrations of organochlorine pesticides (Lindane, Aldrin, Dieldrin, Endosulfan, DDT and DDE) residues in beef samples from the Kumasi and Buoho abattoirs in Ghana were determined using gas chromatography. Organochlorine residues were found in all the samples. The average concentration of lindane in beef fat samples from Kumasi was 4.03 μg/kg and 1.79 μg/kg in beef fat from Buoho. The average levels of lindane were 2.07 μg/kg for lean meat samples from Kumasi abattoir and 0.60 μg/kg in lean meat samples from Buoho. Endosulfan concentration in meat samples from Buoho was 2.28 μg/kg in the fat and 0.59 μg/kg in the lean beef. 1,1-dichloro-2,2-bis(p-dichlorodiphenyl)ethylene (DDE) recorded mean concentrations of 118.45 μg/kg in beef fat and 42.93 μg/kg in lean beef samples from Kumasi abattoir. Beef samples from Buoho had DDE concentration of 31.89 μg/kg in the fat and 5.86 μg/ kg in the lean beef. 1, 1, 1-trichloro-2, 2-bis-(4′-chlorophenyl) ethane (DDT) recorded an average concentration of 545.22 μg/kg in beef fat and 18.85 μg/kg in lean beef samples from Kumasi abattoir. The average concentration of DDT in beef fat from Buoho was 403.82 μg/kg but lean meat samples from the same sampling site recorded mean concentration of 10.82 μg/kg for DDT. Although, most of the organochlorine residues detected were below the maximum limits set by the FAO/WHO, bioaccumulation of these residues is likely to pose health problems in higher organisms like human beings. 相似文献
2.
Hui Xie Lusheng Zhu Qifeng Xu Jun Wang Wei Liu Jinhui Jiang Yan Meng 《Environmental Earth Sciences》2011,62(1):93-99
A 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT)-degrading bacterium was isolated from soil samples that had been enriched
with DDT over a prolonged period of time; these samples were collected from the sewer sludge of a pesticide factory and from
DDT-contaminated fields. This consortium was acclimated by repeated passage through a mineral salt medium containing increasing
concentrations of DDT. We examined the effects of various factors such as the pH, temperature, concentration of DDT, and the
presence of an additional carbon source on the degradation rate of DDT. Based on the analysis of the phenotype, physiological
and biochemical characteristics, and 16S rDNA, the strain KK was identified to belong to the bacteria Alcaligenes. The results showed that at the end of 10 days, the rate of degradation of DDT by the strain KK was 66.5%. When the additional
carbon source concentration, pH, concentration of DDT, and cultivation temperature is 0.5%, 6, 10 mg l−1, and 30°C, respectively, the biodegradation rate peaks. The results also suggested that (1) bacterial growth increases positively
with an increase in the carbon source concentration; (2) the appropriate pH is between 8.0 and 10.0; and (3) the optimal temperature
and DDT concentration are 30°C and 10 mg l−1, respectively. 相似文献
3.
Chemical analyses were done on cores of bottom sediment from three locations in Lake Livingston, a reservoir on the Trinity
River in east Texas to identify trends in water quality in the Trinity River using the chemical record preserved in bottom
sediments trapped by the reservoir. Sediment cores spanned the period from 1969, when the reservoir was impounded, to 1992,
when the cores were collected. Chemical concentrations in reservoir sediment samples were compared to concentrations for 14
streambed sediment samples from the Trinity River Basin and to reported concentrations for soils in the eastern United States
and shale. These comparisons indicate that sediments deposited in Lake Livingston are representative of the environmental
setting of Lake Livingston within the Trinity River Basin. Vertical changes in concentrations within sediment cores indicate
temporal trends of decreasing concentrations of lead, sodium, barium, and total DDT (DDT plus its metabolites DDD and DDE)
in the Trinity River. Possible increasing temporal trends are indicated for chlordane and dieldrin. Each sediment-derived
trend is related to trends in water quality in the Trinity River or known changes in environmental factors in its drainage
basin or both.
Received: 6 October 1995 · Accepted: 13 October 1995 相似文献
4.
Eighty surface sediment samples taken in 1978 from Lake Geneva, together with two cores sampled in 1976 and 1980, and 30 samples (1978) from the Rhone River were analyzed for organochlorine compounds. DDT, its metabolites (DDE, TDE), HCB, and PCB were found. No other organochlorine compound was identified at the detection level of 0.5 ppb. DDT metabolites were widespread and indicated residual DDT sources in the Rhone watershed and other minor lake tributaries, particularly on the Swiss coast. DDT levels have declined since an apparent peak usage in 1957. HCB was found in almost all samples. It first appeared about 1962 with consistent usage to the present. Use is widespread with the major source being the Rhône River. PCB was found in all samples at levels comparable to levels in the North American Great Lakes. Sources appear to be diffuse urban/industrial, with major inputs on the Swiss shore between Vevey and Morges. Peak use of PCB occurred in 1972 and was followed by a decline to 1978, with some evidence for a second increase to 1980, the latest sample available. Both HCB and PCB were found at high levels in the most upstream samples of the Rhône River which may be indicative of substantial atmospheric loadings of these two compounds to the Lake Geneva Basin. 相似文献
5.
Yi-Zhang Zhang Chang-Yuan Tang Xian-Fang Song Yu Dun Wei Meng Yuan Zhang 《Environmental Earth Sciences》2013,70(5):2237-2247
Levels and distributions of organochlorine pesticides (OCPs) and phenolic endocrine-disrupting chemicals (EDCs) in surficial sediments of the Shaying River, the largest tributary of the Huaihe River in eastern China, were investigated to understand their relationship with the hydrodynamics. Concentrations of total hexachlorocyclohexane isomers (ΣHCHs) and dichlorodiphenyltrichloroethanes (ΣDDT) were in the range of 26.7–119 and 9.64–214 ng g?1 with mean values of 104 and 80.7 ng g?1, respectively. Residues of HCHs in sediments can be considered as originating from the application of both technical mixtures and lindane in the past. According to the spatial distribution of (DDD + DDE)/ΣDDT ratios, the influence of recent DDT inputs was dominant upstream, whereas DDD prevailed downstream, due to anaerobic degradation. Concentrations of total phenolic EDCs (ΣEDCs) including nonylphenol (NP), octylphenol (OP) and bisphenol A (BPA) ranged widely from 425 to 3,953 ng g?1 with the highest level occurring in the middle reach. This accumulation could be attributed to the retransfer of surficial sediment from upstream, where the main sources are located. Spatial distribution of contaminants indicated that riverine hydrodynamics can significantly affect their behavior and fate in sediment. This evidence was further verified by multivariate statistical techniques such as Cluster Analysis (CA), Principle Component Analysis (PCA) and Discriminant Analysis (DA). The CA identified three distinct clusters reflecting the large complexity of river system like geography setting, hydrodynamic condition, etc. This finding was also confirmed by the DA. Furthermore, a PCA demonstrated that about 80.8 % of total spatial variance can be explained by the first three factors, which also indicated that contaminant spatial distributions are driven by local inputs, biodegradation and riverine hydrodynamics. 相似文献
6.
Graham Bird Paul A. Brewer Mark G. Macklin Mariyana Nikolova Tsvetan Kotsev Mihail Mollov Catherine Swain 《Applied Geochemistry》2010
Lead isotope signatures (207Pb/206Pb, 208Pb/206Pb, 208Pb/204Pb, 206Pb/204Pb), determined by magnetic sector ICP-MS in river channel sediment, metal ores and mine waste, have been used as geochemical tracers to quantify the delivery and dispersal of sediment-associated metals in the lower Danube River catchment. Due to a diverse geology and range of ore-body ages, Pb isotope signatures in ore-bodies within the lower Danube River catchment show considerable variation, even within individual metallogenic zones. It is also possible to discriminate between the Pb isotopic signatures in mine waste and river sediment within river systems draining individual ore bodies. Lead isotopic data, along with multi-element data; were used to establish the provenance of river sediments and quantify sedimentary contributions to mining-affected tributaries and to the Danube River. Data indicate that mining-affected tributaries in Serbia and Bulgaria contribute up to 30% of the river channel sediment load of the lower Danube River. Quantifying relative sediment contributions from mining-affected tributaries enables spatial patterns in sediment-associated metal and As concentrations to be interpreted in terms of key contaminant sources. Combining geochemical survey data with that regarding the provenance of contaminated sediments can therefore be used to identify foci for remediation and environmental management strategies. 相似文献
7.
A three-dimensional, finite-element flow model was used to assess the hydrogeological effects of depressurizing coalbeds
lying in the Weary Creek exploration block, Elk River valley, southeastern British Columbia, Canada. The simulation results
permit, at an early stage, assessment of the environmental and economic implications of how the flow system may respond to
depressurization.
Estimated reservoir conditions for the coal-seam gas targets lying within the Upper Jurassic–Lower Cretaceous Mist Mountain
Formation indicate that the coalbeds must be depressurized by up to 350 m to attain the critical gas desorption pressure.
The simulations suggest that depressurizing has little effect on groundwater flux to the Elk River. Simulated water production
for three depressurizing wells operating under steady-state, single-phase flow for initial reservoir conditions of 13 and
16.5 cm3/g is 645 m3/d (4,057 barrels/d) and 355 m3/d (2,233 barrels/d), respectively.
Groundwaters collected from monitoring wells have relatively low salinity, ranging from about 250–1,300 mg/L. The groundwater
is supersaturated with respect to Ca–Mg–Fe carbonates (calcite, dolomite, and siderite) and Al-bearing silicates, including
kaolinite and illite. Dissolved trace-metal concentrations are low; only Fe, Cd, Cr, and Zn exceed Canadian water-quality
guidelines for aquatic life. Groundwaters were devoid of the more soluble monocyclic aromatic organic compounds, including
benzene, toluene, ethylbenzene, and polycyclic aromatic compounds, including naphthalene.
Electronic Publication 相似文献
8.
H. El Bakouri A. Aassiri J. Morillo J. Usero M. Khaddor A. Ouassini 《Applied Geochemistry》2008,23(12):3487-3497
This study evaluates pesticide occurrence in Tangier agricultural soil (northern Morocco). Soil samples were measured for alpha endosulfan, beta endosulfan, endosulfan sulfate, alpha HCH, beta HCH, gamma HCH, aldrin, dieldrin, endrin, o,p′ DDT, p,p′ DDD, p,p′ DDE and p,p′ DDT. The analyses were performed by gas chromatography coupled with mass spectrometry (GC/MS). Endosulfan isomers (alpha and beta) and endosulfan sulfate were detected in soil samples, in which the beta isomer showed the highest concentrations. Some DDT metabolites (o,p′ DDT and p,p′ DDE) and alpha HCH were also detected in the analyzed soil. The lipid fraction of the soil samples was extracted by accelerated solvent extraction and fractionated using chromatographic techniques. The principal biomarkers obtained were alcohols, esters, ketones, aldehydes, fatty acids and hydrocarbons. Lipid biomarkers were characterized to determine soil organic matter sources. Experimental results showed that the organic matter was mainly of plant origin, although the bacterial contribution was significant. 相似文献
9.
Compositional fractionation of polyaromatic hydrocarbons in the karst soils, South China 总被引:1,自引:0,他引:1
Yinghui Wang Rui Xue Jie Li Hongxiang Zhu Yiyin Xu Baoming Xue Shihua Qi Daoxian Yuan Oramah I. Theodore 《Environmental Earth Sciences》2012,66(7):2013-2019
This study aims to explore the condensation and fractionation trends of persistent organic pollutants (POPs) in the karst soils. The tiankeng is a karst surface expression that can act as a focal point for introduction of contaminants to a karst aquifer, which may serve both as condenser for vapor phase POPs and as barrier/sink for particulate associated less volatile POPs. The fractionation of POPs in soils from the upper rim and floor of tiankeng is of interest in understanding the role of tiankeng in the long-distance transport of POPs. In the present study, polycyclic aromatic hydrocarbons (PAHs) in the surface soils from the upper rim and floor of Dashiwei tiankeng in Southern China were analyzed. The total PAH concentrations in soils were 23.40–190 ng g−1, with phenanthrene being the most abundant. The distribution patterns of PAH compounds in the soil samples matched well with their properties. It indicated the heavy PAHs were susceptible to retention by the floor soils of tiankeng than light PAHs. A plot of Cfloor/Crim against PAH molecular weight gave a good positive relationship in the molecular weight range of 152–276. It is suggested that the floor soils can be focal points of more concentrated PAH and deserve attention. The concentrations of total PAHs in the floor soils (43.40–190 ng g−1, mean 87.76 ng g−1) were higher than those in the upper rim (23.40–88.94 ng g−1, mean 57.74 ng g−1). In addition, there was a shift in compound pattern with an increase in the proportion of light PAHs (2–3 rings), a decrease in heavy PAHs (5–6 rings) and a relatively stable content of 4-ring PAHs. A combination of particulate scavenging and cold condensation is proposed as the major mechanism for the compositional fractionation of PAHs in the soils from the upper rim and floor of tiankeng. 相似文献
10.
Recharge source and hydrogeochemical evolution of shallow groundwater in a complex alluvial fan system,southwest of North China Plain 总被引:4,自引:0,他引:4
Fadong Li Guoying Pan Changyuan Tang Qiuying Zhang Jingjie Yu 《Environmental Geology》2008,55(5):1109-1122
Many cities around the world are developed at alluvial fans. With economic and industrial development and increase in population,
quality and quantity of groundwater are often damaged by over-exploitation in these areas. In order to realistically assess
these groundwater resources and their sustainability, it is vital to understand the recharge sources and hydrogeochemical
evolution of groundwater in alluvial fans. In March 2006, groundwater and surface water were sampled for major element analysis
and stable isotope (oxygen-18 and deuterium) compositions in Xinxiang, which is located at a complex alluvial fan system composed
of a mountainous area, Taihang Mt. alluvial fan and Yellow River alluvial fan. In the Taihang mountainous area, the groundwater
was recharged by precipitation and was characterized by Ca–HCO3 type water with depleted δ18O and δD (mean value of −8.8‰ δ18O). Along the flow path from the mountainous area to Taihang Mt. alluvial fan, the groundwater became geochemically complex
(Ca–Na–Mg–HCO3–Cl–SO4 type), and heavier δ18O and δD were observed (around −8‰ δ18O). Before the surface water with mean δ18O of −8.7‰ recharged to groundwater, it underwent isotopic enrichment in Taihang Mt. alluvial fan. Chemical mixture and ion
exchange are expected to be responsible for the chemical evolution of groundwater in Yellow River alluvial fan. Transferred
water from the Yellow River is the main source of the groundwater in the Yellow River alluvial fan in the south of the study
area, and stable isotopic compositions of the groundwater (mean value of −8.8‰ δ18O) were similar to those of transferred water (−8.9‰), increasing from the southern boundary of the study area to the distal
end of the fan. The groundwater underwent chemical evolution from Ca–HCO3, Na–HCO3, to Na–SO4. A conceptual model, integrating stiff diagrams, is used to describe the spatial variation of recharge sources, chemical
evolution, and groundwater flow paths in the complex alluvial fan aquifer system. 相似文献
11.
Speciation and phytoavailability of heavy metals in sediments in Nanjing section of Changjiang River 总被引:3,自引:1,他引:2
Heavy metal pollution and their fractionations in the sediments of Changjiang River in Nanjing Reach was monitored for cadmium
(Cd), lead (Pb), zinc (Zn), chromium (Cr), and copper (Cu). Moreover, the biological enrichment of metals by riverine plants
was studied. The results demonstrated there were highly significant variations among different sampling stations for the concentrations
of tested metals. The highest range was for Cu (38.8–120.4 mg kg−1), followed by Cr (74.4–120.0 mg kg−1), Zn (80.9–121.1 mg kg−1), Ni (26.0–55.5 mg kg−1), Pb (15.8–46.7 mg kg−1) and Cd (0.28–0.48 mg kg−1). Cd was the element with highest biological enrichment factor (BEF). The highest BEF of Cd in Erigeron bonariensis reached 3.0, indicating a significant Cd enrichment in this aquatic plant. In addition, 60% of Cd was found in reducible
fraction and exchangeable and acid-soluble fraction, which was consistent with its high mobility. The consistency of Cd fraction
in sediment and suspended particle indicated they came from the same source. Accumulated Cd concentration calculated according
to the release curve showed significant relativity with the total Cd concentration in the sediment. 相似文献
12.
Pei Sun Loh Chen-Tung Arthur Chen Jiann-Yuh Lou Gusti Z. Anshari Houng-Yung Chen Jough-Tai Wang 《Aquatic Geochemistry》2012,18(2):141-158
The Kaoping (Taiwan) and Kapuas (Indonesia) Rivers differ in hydrological cycle, topography and landscape. These differences
strengthen the use of 14C dating, lignin-derived phenols, δ13C values and C/N ratios to determine the sources and diagenesis of surface sedimentary organic carbon (OC) in both rivers.
The Kapuas River is surrounded by forest, resulting in sedimentary OC with a 14C age between 600 and 740 years, Λ (total lignin expressed as mg/100 mg OC) values from 0.94 to 3.70, δ13C values from −27.87 to −30.00‰, C/N ratios from 6.7 to 30.8, %OC from 0.63 to 9.24% and vanillic acid to vanillin ratio,
(Ad/Al)v, values from 0.73 to 2.09, all of which indicate the presence of recent plant-derived organic matter. The tributaries
and three locations upstream of the Kaoping River are also surrounded by forests, resulting in Λ values (0.51–4.80), δ13C values (−23.85 to −27.08‰), C/N ratios (14.1–28.7), %OC (1.01–7.86%) and (Ad/Al)v values (0.86–1.88), which are indicative
of a terrestrial signal. No lignin oxidation products were detected in the mainstream of the Kaoping River or its coastal
zone, hence the surface sediments OC with a 14C age between 4,915 and 15,870 years, enriched δ13C values (−23.30 and −26.54‰), lower C/N ratios (6.0–17.5) and lower %OC (0.15–2.24%) likely represent old rock and soil material.
Massive floods during typhoons most probably cause plant materials from the Kaoping River and its coastal zone to be transported
into the deep sea. 相似文献
13.
Oyster and sediment samples collected from six sites in Galveston Bay from 1986 to 1998 were analyzed for polynuclear aromatic hydrocarbons (PAHs). Total concentrations of parent PAHs in oysters ranged from 20 ng g−1 at one site to 9,242 ng g−1 at another and varied randomly with no clear trend over the 13 year period at any site. Concentrations of alkylated PAHs, which are indications of petroleum contamination, varied from 20 to 80,000 ng g−1 in oysters and were in higher abundance than the parent PAHs, indicating that one source of the PAH contaminants in Galveston Bay was petroleum and petroleum products. Four to six ring parent PAHs, which are indicative of combustion source , were higher than those of 2–3 ring parent PAHs, suggesting incomplete combustion generated PAHs was another source of PAHs into Galveston Bay. Concentrations of parent PAHs in sediments ranged from 57 to 670 ng g−1 and were much lower than those in oysters. Sediments from one site had a high PAH concentration of 5,800 ng g−1. Comparison of the compositions and concentrations of PAHs between sediment and oysters suggests that oysters preferentially bioaccumulate four to six ring PAHs. PAH composition in sediments suggests that the sources of PAH pollution in Galveston Bay were predominantly pyrogenic, while petroleum related PAHs were secondary contributions into the Bay. 相似文献
14.
The technique of competitive ligand-exchange/anodic stripping voltammetry (CLE-SV) was used to investigate effects of pH and Ca concentration on cadmium complexation by fulvic acid (FA), as well as Cd speciation in two different freshwaters, a hardwater Lake Greifen and a softwater River Wyre. Binding of Cd to Suwannee river FA (10 mg/l) was determined at different pH (7–8.5) and in the presence of various concentration of Ca2+ (0–2 mmol/l). The results from one-ligand discrete models were compared to simulations by the WHAM VI model. In Lake Greifen, the determined dissolved [Cd2+] ranged from 10−13 to 10−12 mol/l, and the conditional stability constant with natural ligands was log K
CdL about 9.5–10.5 (pH 8.6–8.8) with ligand concentrations of 1.2–7.8 × 10−6 mol/g C. In the softwater River Wyre, dissolved [Cd2+] ranged from 4 × 10−12 to 1 × 10−11 mol/l, and the ligands were weaker (log K
CdL 8.9–9.8, pH 8.0) with lower ligand concentrations (0.9–2.3 × 10−6 mol/g C). The titration curves of FA samples were close to the simulated curves by the WHAM VI model at pH 8.0–8.5, but deviated more from the model at lower pH, indicating that the results determined with CLE-SV for Cd-FA complexation are relevant to the data base in the model. Calculation of the Ca competition for Cd binding by FA showed a competition effect of similar strength as the measured one, but indicated a systematic difference between measured and modeled data at pH 7.5. Using the WHAM model for comparison with FA, the complexation of Cd by the River Wyre ligands was close to that of FA, whereas stronger complexation was observed in the Lake Greifen water. These differences may originate from different ligand composition in the lake and the river. 相似文献
15.
Total nitrogen (TN), total phosphorus (TP), and total suspended solids (TSS) loadings [log (kg ha−1 yr−1)] were regressed against seagrass depth limits (percent of depth-limit targets) to back-predict the load limits or allocations
(kg ha−1 yr−1 or kg yr−1) necessary to meet targeted seagrass depth limits in the Indian River and Banana River (IRBR) lagoons, Florida. Because the
load allocations can be applied as total maximum daily loads (TMDL) for the IRBR (U.S. Environmental Protection Agency mandate),
the method and results are developed and presented toward that end. The regression analyses indicate that the range of surface-discharge
load limits (nonpoint + point source), per watershed area, required to achieve the desired depth limits for seagrass in the
IRBR are approximately 2.4–3.2 kg ha−1 yr−1 TN, 0.41–0.64 kg ha−1 yr−1 TP, and 48–64 kg ha−1 yr−1 TSS. This simple regression method may have application to other shallow estuarine lagoons or bays where seagrass growth
is limited by light and water transparency, water transparency is strongly affected by watershed pollutant loadings, water
residence times are sufficiently long to allow seagrass coverage to respond to and covary with total load inputs, and multiyear
monitoring has yielded sufficient variability in both pollutant loadings and seagrass coverages to develop a statistically
meaningful relationship. 相似文献
16.
Determination of HCH and DDT in soils following Wenchuan 5.12 Violent Earthquake in China 总被引:1,自引:0,他引:1
Weiwei Cui Qiangbin Zhang Xianlei Zhu Yunyang Wan Zhihuan Zhang Zhihua Fan Tieguan Wang 《中国地球化学学报》2011,30(1):125-131
A large number of disinfectants and insecticides were used on a large scale after the Wenchuan 5.12 Violent Earthquake. The disinfectants and insecticides, including HCH (hexachlorocyclohexane) and DDT (dichlorodiphenyltrichoroethane) as representative OCPs, could lead to serious environmental problems. In order to disclose the residues of HCH and DDT in soils following the Wenchuan 5.12 Violent Earthquake, surface soils in Dujiangyan City and Beichuan County were sampled in 2009. The samples were analyzed by GC/MS after pre- treatment by ultrasonic solvent extraction. It has been found that the concentra-tions of γ-HCH, β-HCH and 4,4’-DDT in soils of Beichuan County were 94–102.4, 14.1–36.1 and 2.9–4.3 times high their concentrations in those of the Wolong Nature Reserve, and the concentrations in soils of Dujiangyan City were 52.4–61.6, 8.8 –45.3 and 5.4–6.2 times high their concentrations in soils of the Wolong Nature Reserve, respectively. According to the isomers of HCHs and metabolites of DDTs, it could be concluded that these areas may have additional inputs of lindane and 4,4’-DDT. 相似文献
17.
Thomas H Giordano 《Geochemical transactions》2002,3(1):56-17
It is well established through field observations, experiments, and chemical models that oxidation (redox) state and pH exert a strong influence on the speciation of dissolved components and the solubility of minerals in hydrothermal fluids. log –pH diagrams were used to depict the influence of oxygen fugacity and pH on monocarboxylate- and dicarboxylate-transport of Pb and Zn in low-temperature (100°C) hydrothermal ore fluids that are related to diagenetic processes in deep sedimentary basins, and allow a first-order comparison of Pb and Zn transport among proposed model fluids for Mississippi Valley-type (MVT) and red-bed related base metal (RBRBM) deposits in terms of their approximate pH and conditions. To construct these diagrams, total Pb and Zn concentrations and Pb and Zn speciation were calculated as a function of log and pH for a composite ore-brine with concentrations of major elements, total sulfur, and total carbonate that approximate the composition of MVT and RBRBM model ore fluids and modern basinal brines. In addition to acetate and malonate complexation, complexes involving the ligands Cl-, HS-, H2S, and OH- were included in the model of calculated total metal concentration and metal speciation. Also, in the model, Zn and Pb are competing with the common-rock forming metals Ca, Mg, Na, Fe, and Al for the same ligands. Calculated total Pb concentration and calculated total Zn concentration are constrained by galena and sphalerite solubility, respectively. Isopleths, in log –pH space, of the concentration of Pb and concentration of Zn in carboxylate (acetate + malonate) complexes illustrate that the oxidized model fluids of T. H. Giordano (in Organic Acids in Geological Processes, ed. E. D. Pittman and M. D. Lewan, Springer-Verlag, New York, 1994, pp. 319–354) and G. M. Anderson (Econ. Geol., 1975, 70, 937–942) are capable of transporting sufficient amounts of Pb (up to 10 ppm) and Zn (up to 100 ppm) in the form of carboxylate complexes to form economic deposits of these metals. On the other hand, the reduced ore fluid models of D. A. Sverjensky (Econ. Geol., 1984, 79, 23–37) and T. H. Giordano and H. L. Barnes (Econ. Geol., 1981, 76, 2200–2211) can at best transport amounts of Pb and Zn, as carboxylate complexes, that are many orders of magnitude below the 1 to 10 ppm minimum required to form economic deposits. Lead and zinc speciation (mol% of total Pb or Zn) in the model ore fluid was calculated at specific log –pH conditions along the 100, 0.01, and 0.001 ppm total Pb and total Zn isopleths. Along the 100 ppm isopleth conditions are oxidized (∑SO4 >> ∑H2S) with Pb and Zn predominantly in the form of chloride complexes under acid to mildly alkaline conditions (pH from 3 to approximately 7.5), while hydroxide complexes dominate Pb and Zn speciation under more alkaline conditions. Sulfide complexes are insignificant under these oxidized conditions. For more reduced conditions along the 0.01 and 0.001 ppm isopleths chloride complexes dominate Pb and Zn speciation in the SO4 2- field and near the SO4 2--reduced sulfur boundary from pH = 4 to approximately 7.5, while hydroxide complexes dominate Pb and Zn speciation under alkaline conditions above pH = 7.5 in the SO4 2- field. In the most reduced fluids (∑H2S >> ∑SO4) along the 0.01 and 0.001 isopleths, sulfide complexes account for almost 100% of the Pb and Zn in the model fluid. Acetate (monocarboxylate) complexation is significant only under conditions of chloride and hydroxide complex dominance and its effect is maximized in the pH range 5 to 7, where it complexes 2 to 2.6% of the total Pb and 1 to 1.25% of the total Zn. Malonate (dicarboxylate) complexes are insignificant along all isopleths. The speciation results from this study show that deep formation waters characterized by temperatures near 100°C, high oxidation states and ∑H2S < 0.03 mg L-1 (), high chlorinities (~ 100000 mg L-1), and high but reasonable concentrations of carboxylate anions can mobilize up to 3% of the total Pb and up to 1.3% of the total Zn as carboxylate complexes. Furthermore, these percentages, under the most favorable conditions, correspond to approximately 1 to 100 ppm of these metals in solution; concentrations that are adequate to form economic deposits of these metals. However, the field evidence suggests that all of these optimum conditions for carboxylate complexation are rarely met at the same time. A comparison of the composite ore fluid compositions from this study and modern brine data shows that the ore brines, corresponding to log –pH conditions based on the Anderson (1975) and Giordano (1994) model fluids, are similar in many respects to modern, high trace-metal petroleum-field brines. The principal differences between modern high trace-metal brines and the composite ore fluids of Anderson (1975) and Giordano (1994) relate to their carboxylate anion content. The reported concentrations of monocarboxylate anions (∑monocbx) and dicarboxylate anions (Edicbx) in high trace-metal petroleum-field brines (< 1 to 300 mg L-1 and < 1 mg L-1, respectively) are significantly lower than the concentrations assumed in the modelled brines of this study (∑monocbx = 7 700 mg L-1 and ∑dicbx = 300 mg L-1). There are also major differences in the corresponding total chloride to carboxylate ratio (∑m Cl/∑m cbx) and monocarboxylate to dicarboxylate ratio (∑m monocbx/∑m dicbx). Modern high trace-metal brines have much higher ∑m Cl/∑m cbx values and, therefore, the contribution of carboxylate complexes to the total Pb and Zn content in these modern brines is likely to be significantly less than the 1 to 3 percent for the composite ore fluids of Anderson (1975) and Giordano (1994). The composite ore-brine based on the Giordano and Barnes (1981) MVT ore fluid is comparable to the high salinity (> 170 000 mg L-1 TDS) subset of modern brines characterized by low trace-metal content and high total reduced sulfur (∑H2S). A comparison of the Sverjensky (1984) composite ore-brine with modern petroleum-field brines in terms of ∑H2S and Zn content, reveals that this ore fluid corresponds to a "border-type" brine, between modern high trace-metal brines and those with low trace-metal content and high ∑H2S. A brine of this type is characterized by values of ∑H2S, ∑Zn, and/or ∑Pb within or near the 1 to 10 mg L-1 range. Based on brine-composition data from numerous references cited in this paper, border-type brines do exist but are rare. The model results and field evidence presented in this study are consistent with other chemical simulation studies of carboxylate complexation in modern petroleum-field brines. Thus, it appears that carboxylate complexation plays a minor, if not insignificant, role as a transport mechanism for Pb and Zn in high salinity Na–Cl and Na–Ca–Cl basinal brines and related ore fluids. 相似文献
18.
Maya G. Kopylova John J. Gurney Leon R. M. Daniels 《Contributions to Mineralogy and Petrology》1997,129(4):366-384
More than 99% of mineral inclusions in diamonds from the River Ranch pipe in the Late Archean Limpopo Mobile Belt (Zimbabwe),
are phases of harzburgitic paragenesis, namely olivine (Fo92–93), orthopyroxene (Mg# = 93), G10 garnets and chromites. The diamond inclusion (DI) chemistry demonstrates a limited overlap
with River Ranch kimberlite macrocrysts: the DI garnets are more Ca-undersaturated, and DI spinel and garnet are more Mg-rich.
Most River Ranch diamond inclusions were equilibrated at T = 1080–1320 °C, P = 47–61 kbar, and f
O2 between IW and WM buffers. The P/T profile beneath the Limpopo Mobile Belt (LMB) is consistent with a paleo-heat flow of 41–42 mW/m2, similar to calculations for Roberts Victor, but hotter than for the Finsch, Kimberley, Koffiefontein and Premier Mines.
This is ascribed to the younger tectonothermal age of the LMB and its proximity to Late Archean oceans. Like diamond inclusions
from all other kimberlites studied, the River Ranch DI have a lithospheric affinity and therefore indicate that an ancient,
chemically depleted, thick (at least 200 km) mantle root existed beneath the Limpopo Mobile Belt 530–540 Ma ago. The mantle
root might have developed beneath the continental Central Zone of the LMB as early as the Archean, and could be alien to the
overthrust allochthonous sheet of the Limpopo Belt. Oxygen fugacity estimates for diamond inclusions at River Ranch are similar
to other diamondiferous harzburgites beneath the Kaapvaal craton, indicating that the Kaapvaal mantle as a whole was well
buffered and homogeneous with respect to f
O2 at the time of peridotitic diamond crystallization.
Received: 11 January 1995 / Accepted: 10 June 1997 相似文献
19.
Tidal freshwater marshes exist at the interface between watersheds and estuaries, and thus may serve as critical buffers
protecting estuaries from anthropogenic metal pollution. Bi-weekly samples of newly deposited marsh sediments were collected
and analyzed for Cu, Zn, and Fe concentrations over 21 months from July 1995 to March 1997 in five distinct habitats at the
head of Bush River, Maryland. Bi-weekly anthropogenic metal enrichments ranged from 0.9–4.7. Anthropogenic excess metal loadings
averaged over 1996 ranged from 6–306 and 25–1302 μg cm−2 year−1 between sites for Cu and Zn, respectively. Based on Fe-normalized trace metal signatures, Susquehanna River sediment does
not significantly contribute to upper Bush River. Organic matter was found to dilute total metal concentrations, whereas past
studies suggested organics enhance labile metal content. Analysis of metal input pathways shows that marsh metals are primarily
imported from nearby subtidal accumulations of historic watershed material by tidal flushing.
Received: 29 April 1999 / Accepted: 7 December 1999 相似文献
20.
We report the dissolved major element, organic carbon, and δ13CDOC, δ13CPOC, δD, δ18O, and 87Sr/86Sr composition of 19 summer samples from the Amur River. The Amur transported 2.6 Tg C/year of total organic carbon to the
Sea of Okhotsk. The physical weathering rate (PWR) based on suspended particulate material was 13 (1.4–14) tons/(km2 year), and the chemical weathering rate based on total dissolved solids was 7 (4.3–46) tons/(km2 year). We further quantified the sources of the dissolved cations using an inverse model: rain accounted for 2 (0.6–5)%,
evaporite 3 (0.7–7)%, carbonate 51 (29–74)%, and silicate 45 (25–64)%. The silicate weathering rate (SWR) in the Amur basin
was 23 (15–98) × 103 mol/(km2 year) or 0.67 (0.40–2.81) tons/(km2 year), comparable to those of the Siberian rivers and the Mackenzie at higher latitudes. The SWR of the Amur was negatively
correlated with elevation and relief, and positively correlated with runoff. 相似文献