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1.
Dissolved and particulate concentrations of metals (Fe, Al, Mn, Co, Ni, Cu, Zn, Cd, Tl, Pb) and As were monitored over a 5 year period in the Amous River downstream of its confluence with a creek severely affected by acid mine drainage (AMD) originating from a former Pb–Zn mine. Water pH ranged from 6.5 to 8.8. Metals were predominantly in dissolved form, except Fe and Pb, which were in particulate form. In the particulate phase, metals were generally associated with Al oxides, whereas As was linked to Fe oxides. Metal concentrations in the dissolved and/or particulate phase were generally higher during the wet season due to higher generation of AMD. Average dissolved (size < 0.22 μm) metal concentrations (μg/L) were 1 ± 4 (Fe), 69 ± 49 (Al), 140 ± 118 (Mn), 4 ± 3 Co, 6 ± 4 (Ni), 1.3 ± 0.8 (Cu), 126 ± 81 (Zn), 1.1 ± 0.7 (Cd), 0.9 ± 0.5 (Tl), 2 ± 3 (Pb). Dissolved As concentrations ranged from 5 to 134 μg/L (30 ± 23 μg/L). During the survey, the concentration of colloidal metals (5 kDa < size < 0.22 μm) was less than 25% of dissolved concentrations. Dissolved metal concentrations were generally higher than the maximum concentrations allowed in European surface waters for priority substances (Ni, Cd and Pb) and higher than the environmental quality standards for other compounds. Using Diffusion Gradient in Thin Film (DGT) probes, metals were shown to be in potentially bioavailable form. The concentrations in Leuciscus cephalus were below the maximum Pb and Cd concentrations allowed in fish muscle for human consumption by the European Water Directive. Amongst the elements studied, only As, Pb and Tl were shown to bioaccumulate in liver tissue (As, Pb) or otoliths (Tl). Bioaccumulation of metals or As was not detected in muscle.  相似文献   

2.
Variations in the abundance of iron in the mantle may have important consequences for mantle dynamics and geochemistry. The abundance of iron in lavas derived from mantle source regions varies during partial melting and subsequent fractionation, so that source heterogeneities are not easily resolved in iron abundances alone. However, manganese is a geochemically similar element, so that the planetary Fe/Mn ratio is approximately constant. Here, we report new Fe/Mn results for mid-oceanic ridge basalts (MORBs), oceanic island basalts (OIBs) and komatiites using a precise inductively coupled plasma mass spectrometric (ICP-MS) method to measure Fe/Mn to better than 0.5% (2σ). As a measure of reproducibility of Fe/Mn, five olivine and five orthopyroxene grains from a Kilbourne Hole peridotite xenolith yielded Fe/Mn 69.8 ± 0.4 and 44.3 ± 0.2, respectively. To avoid ubiquitous secondary Fe-Mn oxides, Fe/Mn ratios in Pacific, Atlantic, and Indian MORBs were determined by Laser Ablation ICP-MS. MORB Fe/Mn (53-56) corrected for crystal fractionation yielded a value of 54.0 ± 1.2 (1σ). Icelandic basalts and picrites (MgO 10-29%) had Fe/Mn ratios 56-61, with a single exception. Six relatively fresh komatiites from Belingwe (MgO 20-29%) yielded Fe/Mn values of 58.3 ± 0.2 (1σ). Basalts from Tahiti and Reunion exhibited high Fe/Mn (>65), like Hawaii. This implies that the mantle source regions of Tahiti and Reunion lavas may have been enriched in Fe relative to other mantle reservoirs (e.g., MORBs, Iceland, Belingwe). Combined with previous results for Hawaii, we now find that Fe/Mn > 65 is characteristic of at least two plumes from the Pacific Superswell. It is conceivable that this is evidence for excess Fe due to core-mantle interaction in these mantle plumes, although partial melting of secondary pyroxenites may cause similar variations in Fe/Mn. Heterogeneity of Fe/Mn in mantle-derived lavas is now clearly documented.  相似文献   

3.
To understand the biogeochemical cycles of trace metals (Cd, Cu, Fe, Mn, Ni and Zn) in a hypersaline subtropical marsh, geochemical studies of both interstitial and solid phases were conducted on sediment cores from Chiricahueto marsh, SE Gulf of California. The sequential extraction procedure proposed by Tessier was used to estimate the percentages of the metals present in each geochemical phase of the sediment. Metal concentrations in the solid phase were found to be enriched in the upper layers and mainly associated with reactive fractions such as organic matter, Fe–Mn oxyhydroxides and carbonates (46–74% of Ni, Mn and Cd, and 11–19% of Cu and Zn). Principal factor analysis (PFA) and Spearman correlation analysis revealed a strong positive association of metals and their reactive phases with OC (the diagenetic component), and a negative or non-association with the mud content, Al, Fe and Li (the lithogenic component). Diagenetically released metals are mainly mobilized within hypersaline sediments by buoyancy transport (>90% of total flux) in response to an extreme salinity gradient by input of fresh groundwater (3–6 psu cm−1). The molecular diffusion due to the gradient of metals in porewater (maximum and higher levels at 5–7 and below 20 cm depth, respectively) is significantly less important to the advective transport. Most of the metals mobilized by diffusion–advection processes are re-precipitated in the sediments by authigenic minerals, only <10% of most metals are extruded out to the overlying water column. Authigenic accumulation rates were estimated as 1.42–7.09 mg m−2 a−1 for Cd; 58.8–378 for Cu; 6922–17,985 for Fe; 38.2–345 for Mn; 20.8–263 for Ni; and 282–2956 mg m−2 a−1 for Zn. The Mn–Fe oxyhydroxides (40–85% of reactive metals) in the upper oxic–suboxic layers (<5 cm below surface) and sulfide minerals (75–97%) in anoxic sediment layers (7–18 cm) constitute the main scavengers for metals.  相似文献   

4.
The distributions of particulate elements (Al, P, Mn, Fe, Co, Cu, Zn, Cd, and Pb), dissolved trace metals (Mn, Fe, Co, Cu, Zn, and Cd), and dissolved nutrients (nitrate, phosphate, and silicic acid) were investigated in the Gulf of the Farallones, a region of high productivity that is driven by the dynamic mixing of the San Francisco Bay plume, upwelled waters, and California coastal surface waters. Particulate metals were separated into >10 and 0.4-10 μm size-fractions and further fractionated into leachable (operationally defined with a 25% acetic acid leach) and refractory particulate concentrations. Dissolved metals (< 0.4 μm pore-size filtrate) were separated into colloidal (0.03-0.4 μm) and soluble (<0.03 μm) fractions. The percent leachable particulate fractions ranged from 2% to 99% of the total particulate concentration for these metals with Mn and Cd being predominantly leachable and Fe and Al being predominantly refractory. The leachable particulate Pb concentration was associated primarily with suspended sediments from San Francisco Bay and was a tracer of the plume in coastal waters. The particulate trace metal data suggest that the leachable fraction was an available source of trace metal micronutrients to the primary productivity in coastal waters. The dissolved trace metals in the San Francisco Bay plume and freshly upwelled surface waters were similar in concentration, with the exception of Cu and Co, which exhibited relatively high concentrations in plume waters and served as tracers of this water mass. The dissolved data and estimates of the plume dynamics suggest that the impact of anthropogenic inputs of nutrients and trace metals in the San Francisco Bay plume contributes substantially to the concentrations found in the Gulf of the Farallones (10-50% of estimated upwelled flux values), but does not greatly disrupt the natural stoichiometric balance of trace metal and nutrient elements within coastal waters given the similarity in concentrations to sources in upwelled water. In all, the data from this study demonstrate that the flux of dissolved nutrients and bioactive trace metals from the San Francisco Bay plume contribute to the high and relatively constant phytoplankton biomass observed in the Gulf of the Farallones.  相似文献   

5.
We report seawater boron concentration (mg kg−1) and chlorinity (‰) values measured in seawater samples (n = 139) collected at various depths in the North Pacific and North Atlantic oceans and the East/Japan Sea (located in the western temperate North Pacific). Our results indicate that variations in seawater boron concentration are strongly coupled to variations in chlorinity (and salinity), yielding a mean boron to chlorinity ratio of 0.2414 ± 0.0009 mg kg−1 ‰−1 (boron to salinity ratio = 0.1336 ± 0.0005 mg kg−1 ‰−1). This ratio was surprisingly universal throughout the water column in the three marine basins and across widely different ocean surface regimes, but differs from the generally accepted ratio of 0.232 ± 0.005 mg kg−1 ‰−1 determined by Uppström (1974), which was based on only 20 measurements at four sites in the tropical Pacific Ocean. In converting total alkalinity to carbonate alkalinity (and vice versa) for thermodynamic calculations, the difference between these two ratios leads to a difference of 5 μmol kg−1 in estimates for ocean surface waters, where the contribution of borate to total alkalinity is typically greatest. We suggest the use of the new boron to chlorinity ratio for predicting seawater boron concentrations using chlorinity (or salinity) data.  相似文献   

6.
Vertical and horizontal distributions of dissolved and suspended particulate Fe and Mn, and vertical fluxes of these metals (obtained with sediment traps) were determined throughout the Pacific Ocean. In general, dissolved Fe is low in surface and deep waters (0.1 to 0.7 nmol/kg), with maxima associated with the intermediate depth oxygen minimum zone (2.0 to 6.6 nmol/kg). Vertical distributions of dissolved Mn are similar to previous reports, exhibiting a surface maximum, a subsurface minimum, a Mn maximum layer coincident with the oxygen minimum zone, and lowest values in deep waters.Near-shore removal processes are more intense for dissolved Fe than for dissolved Mn. Dissolved Mn in the surface mixed layer remains elevated much farther offshore than dissolved Fe. Elevated near-surface dissolved Mn concentrations occur in the North Pacific Equatorial Current, suggesting transport from the eastern boundary. Near-surface mixed-layer dissolved Mn concentrations are higher in the North Pacific gyre reflecting enhanced northern hemisphere aeolian sources.Residence time estimates for the settling of refractory paniculate Fe and Mn from the upper water column are 62–220 days (Fe), and 105–235 days (Mn). In contrast, residence times for the scavenging of dissolved Fe and Mn are 2–13 years (Fe) and 3–74 years (Mn). Scavenging residence times for dissolved Mn based on horizontal mixing in the surface mixed layer of the northeast Pacific are 0.4 years (nearshore) to 19 years (1000 km offshore).There is no evidence for in situ Fe redox dissolution within sub-oxic waters in the eastern tropical North Pacific. Dissolved Fe appeared to be controlled by dissolution from sub-oxic sediments, with oxidative scavenging in the water column or upper sediment layers. However, in situ Mn dissolution within the oxygen minimum zone was evident.  相似文献   

7.
The HCl-soluble Fe, Mn, and Cu contents of Recent Indian Ocean Sediments off the eastern Coast of Somalia increases progressively away from the coast with decreasing grain size and carbonate content. The average Mn and Cu contents of the Indian Ocean deep-sea clay (0.56% Mn, 0.025% Cu, recalculated on a carbonate-free base) are between those of the Atlantic (0.40% Mn, 0.013% Cu) and the Pacific Ocean (0.94% Mn, 0.040% Cu).
Zusammenfassung In den rezenten Sedimenten des Indischen Ozeans vor der Ostküste Somalias nehmen die salzsäurelöslichen Eisen-, Mangan- und Kupfergehalte vom Küstenbereich zur Tiefsee hin bei abnehmendem Karbonatgehalt und geringer werdender Korngröße kontinuierlich zu. Die durchschnittlichen Mn- und Cu-Konzentrationen des Tiefseetons aus dem Indischen Ozean (bezogen auf karbonatfreies Material) liegen mit 0,56 bzw. 0,025% zwischen denjenigen des Atlantischen (0,40% Mn, 0,013% Cu) und des Pazifischen (0,94% Mn, 0,040% Cu) Ozeans.

Advanced report to Meteor-Forschungsergebnisse, Indian Ocean Expedition 1964/65, to be published in 1967/68  相似文献   

8.
In order to assess pollutants and impact of environmental changes along the Egyptian Red Sea coast, seven recent and Pleistocene coral species have been analyzed for Zn, Pb, Mn, Fe, Cr, Co, Ni, and Cu. Results show that the concentration of trace elements in recent coral skeletons is higher than those of Pleistocene counterpart except for Mn and Ni. In comparison with recent worldwide reefs, the present values are less than those of Central America coast (iron), Gulf of Aqaba, Jordan (lead, copper), Gulf of Mannar, India (chromium, zinc, manganese), Costa Rica, Panama (chromium, nickel), North-west coast of Venezuela and Saudi Arabia (copper). The present values are higher than those of Gulf of Aqaba, Jordan (iron, zinc, manganese), Gulf of Mannar, India (lead, cobalt, nickel), North-west coast of Venezuela (lead, zinc, chromium, manganese), Australia (copper, nickel, zinc, manganese). The highest values were recorded in Stylophora pistillata (iron, lead and copper), Acropora cytherea (cobalt), Pocillopora verrucosa (zinc) and the lowest concentrations were recorded in Goniastrea pectinata (iron, chromium, copper and nickel), Favites pentagona (lead, zinc and manganese), and Porites lutea (cobalt). The differences in metals content among the studied species are attributed to differences in microstructure and microarchitecture.  相似文献   

9.
We explore Fe/Mn and Nb/Ta ratios of basalts as potential tracers for differentiating melts of recycled mafic crustal lithologies from peridotitic melts. Trace elements and Fe/Mn ratios of the Mesozoic and Cenozoic basalts from East China were analyzed by ICP-MS. Low Nb/Ta ratios (15.4 ± 0.3 (2σ, n = 45)), high Nb and Ta contents (60.1 and 4.01 ppm) and high Fe/Mn ratios (64.7 ± 1.5 (2σ, n = 45)) characterize the <110 Ma basalts. Mesozoic basalts with ages >110 Ma are characterized by superchondritic Nb/Ta ratios (20.1 ± 0.3 (2σ, n = 25)), low Nb and Ta contents (10.8 and 0.54 ppm) and slightly lower Fe/Mn ratios (60.0 ± 1.1 (2σ, n = 25)). Both the Mesozoic and Cenozoic basalts have Fe/Mn ratios higher than basaltic melt formed by partial melting of peridotite at the same MgO and CaO levels. Although both the Mesozoic and Cenozoic basalts are characterized by highly fractionated REE patterns, the >110 Ma basalts have island arc-type trace element patterns (i.e., depletion in Nb and Ta), whereas OIB-type trace element patterns (e.g., no depletion in Nb and Ta) are characteristic of the <110 Ma basalts. Based on DFe/Mn values for olivine, clinopyroxene, orthopyroxene and garnet, high Fe/Mn ratios and negative correlations of Fe/Mn with Yb (Y) of the <110 Ma basalts suggest clinopyroxene/garnet-rich mantle sources. The lower Fe/Mn ratios and positive correlations of Fe/Mn with Y and Yb in the >110 Ma basalts suggest orthopyroxene/garnet-rich mantle sources. Combining these data with Sr-Nd isotopes, we present a conceptual model to explain the Nb/Ta ratios and PM-normalized trace element patterns of the >110 and <110 Ma basalts. Preferential melting of recycled ancient lower continental crust during Mesozoic lithospheric thinning resulted in (1) peridotite-melt/fluid reaction that formed the orthopyroxene/garnet-rich mantle sources for the >110 Ma basalts, and (2) peridotite + rutile-bearing eclogite mixing that formed the clinopyroxene/garnet-rich mantle sources for the <110 Ma basalts. The choice of models may indeed be arbitrary and non-unique, but the goal is to seek relatively simple forward models that explain the characteristics of the lavas, and the differences between the >110 and <110 Ma basalts, in a relatively consistent geodynamic framework.  相似文献   

10.
Three vertical profiles of seawater concentration and isotopic composition of Nd were determined for the western to central North Pacific Ocean.In the subarctic oceanic region, at depths greater than 500 m, one vertical profile of Nd isotopic composition was indistinguishable from most previously reported profiles from here. The data indicate a rather homogeneous Nd isotopic composition in the subarctic oceanic region at middle to deep depths (>500 m). Two stations in the subtropical oceanic region exhibited similar Nd isotopic composition profiles to those previously reported. The maxima εNd values at depths of 800-1000 m (εNd = −3.4 to −2.7), which correspond to the North Pacific Intermediate Water (NPIW), are found at both subtropical stations. This implies a ubiquitous distribution of NPIW showing a radiogenic εNd value in the North Pacific. The subsurface minimum at a depth of ∼200 m, which indicates the penetration of the North Pacific Tropical Water (NPTW) with an unradiogenic Nd isotopic signal, was observed at one station in the western Pacific. This station had much lower εNd than the central station at depths around 5000 m, suggesting the greater prominence of Antarctic Bottom Water (AABW) in the western subtropical Pacific than in the central to eastern subtropical Pacific.Results of a model calculation assuming boundary exchange indicate that the Hawaiian Islands play an important role in supplying radiogenic Nd to the central Pacific, similar to some continental margins.We show that Nd isotopic composition is a versatile tracer for ocean circulation and the geochemical cycle of Nd in the North Pacific. Further studies on the distribution of Nd isotopic composition in the Pacific Ocean, including the Southern Pacific, will better elucidate the circulation and geochemical cycle of Nd in the Pacific.  相似文献   

11.
Hafnium isotopes in Arctic Ocean water   总被引：1，自引：0，他引：1  
The first isotopic compositions of dissolved hafnium in seawater from across the Arctic Ocean are reported. Most samples from the four sub-basins of the Arctic Ocean have values within error of an average of εHf = +0.8. Combined Hf-Nd isotope compositions do not fall on the well-established positive correlation for mantle and crustal rocks. Instead, Arctic waters have Hf that is more radiogenic than that typically found in rocks with similar Nd isotope compositions, a feature previously found in ferromanganese crusts and waters from the Pacific Ocean. Arctic seawater samples generally fall on the lower part of the ferromanganese crust array, reflecting influences of inputs from Arctic rivers and interactions of shelf waters with underlying sediments. Arctic rivers have much higher Hf concentrations (7-30 pM) than Arctic seawater (0.36-4.2 pM). Water from the Mackenzie River has the least radiogenic Hf, with εHf = −7.1 ± 1.7, and plots furthest away from the ferromanganese crust array, while waters from the Ob, Yenisey, and Lena Rivers have values that are indistinguishable from most Arctic waters. In the Amundsen, Makarov, and Canada basins, Hf concentrations are highest at the surface and lowest in the deeper waters, reflecting the influences of riverine inputs and of waters that have flowed over the extensive Siberian continental shelves and have Nd and Hf characteristics that reflect water-sediment interactions. This is in contrast to the relatively low near surface Hf concentrations reported for locations elsewhere. The Pacific water layer in the Canada Basin exhibits the highest value of εHf = +6.8 ± 1.8, reflecting the Hf isotopic composition of waters entering the Arctic from the Pacific Ocean. Mixing relationships indicate that a substantial fraction of the Hf in the Mackenzie River is lost during estuarine mixing; the behaviour of Hf from other rivers is less constrained.  相似文献   

12.
The concentrations of Sc, Ti, Fe, Mn, Co, Ni, Cu, La, Th and U have been measured in several Pacific pelagic clays having widely different accumulation rates, 0.4–9.0 mm/103 yr. The authigenic fractions and deposition rates of these elements have been estimated from the measured concentrations using various models. The results show that in Pacific clays about 90% Mn, 80% Co and Ni and 50% Cu are authigenic whereas the major fraction (?90%) of Sc, Ti, Fe, La, Th and U are of detrital origin.Anticorrelation between the clay accumulation rates and the concentrations of Mn, Co, Ni and Cu is observed. This suggests a uniform authigenic deposition of these elements superimposed on varying amounts of detrital materials. The concentrations of Sc, Ti and Th are almost independent of sedimentation rates, indicating that their authigenic deposition is small compared to their detrital contribution.Comparison of the authigenic deposition and river input rates shows that Mn, Co and Ni are accumulating in excess of their supply by factors of 2–10, whereas the converse is true for Cu and U. Additional sources to account for the budgetary discrepancies of Mn, Co and Ni are discussed, with particular reference to in situ leaching of detrital phases transported to the oceans via rivers.  相似文献   

13.
The Gulf of Mannar along the Tuticorin coast is a coral base of the southeast coast of India. To obtain a preliminary view of its environmental conditions, geochemical distribution of major elements (Si, Al, Fe, Ca, Mg, Na, K, P), trace elements (Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) and acid leachable elements (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) were analyzed in surface sediment samples from two seasons. Geochemical fractionation confirmed the lithogenic origin of metals, which were mainly associated with the detrital phase. The sediments in the gulf are sandy with abundant calcareous debris, which controls the distribution of total and acid leachable elements. Enrichment factors relative to crust vary by a magnitude of two to three and the presence of trace metals indicates the input of Cr, Pb, Cd, Cu and Zn in both forms through industrial activities. Factor analysis supports the above observation with higher loadings on acid leachable elements and its association with CaCO3. The increase in concentration of trace metals (Cr, Pb, Cd, Cu, Co, Ni, Zn) along the Gulf of Mannar indicates that the area has been contaminated by the input from riverine sources and the industries nearby. The present study indicates that other sources should be evaluated in the long-term monitoring program.  相似文献   

14.
Oceanic surface and deep iron distribution and size fractionation were investigated on three cruises in the sub-tropical and tropical Atlantic Ocean. Detailed profiles and transects were collected and analyzed for “dissolved” Fe (DFe, 0.4 μm filtered) and “soluble” Fe (SFe, 0.02 μm filtered). The difference between DFe and SFe is inferred to be the “colloidal” fraction of Fe (CFe). SFe concentration distributions and profiles showed little variability in the Atlantic Ocean with slightly lower concentrations of SFe in the upper ocean than the relatively uniform concentrations observed in deep-water (≈0.3 to 0.4 nmol/kg). In contrast, variability in the Atlantic DFe was dominated by variability in CFe. DFe and CFe followed dust deposition trends, and observed surface maxima in DFe profiles were always due to maxima in the CFe fraction. Where dust deposition and surface DFe were low (i.e., the South Atlantic), the CFe fraction of DFe was low and frequently negligible in surface waters. Below the surface maxima in CFe and DFe, CFe always decreased to negligible levels at 30-80 m, remained low or negligible throughout the pycnocline, and increased with depth below the pycnocline. At a site located on the edge of the equatorial system (10°N), high DFe and CFe concentrations were associated with an oxygen minimum zone (OMZ) at depths of 130 to 1100 m. Deep-water DFe and CFe concentrations varied between water masses depending on the source, age, and path of the water masses. DFe in NADW decreased by 30% from the North Atlantic to the South Atlantic site with most of the decrease due to loss of CFe. At the South Atlantic site, NADW had higher DFe and a higher fraction of CFe than the Antarctic water masses.  相似文献   

15.
The Ni geochemistry of limonite and saprolite laterite ores from Pujada in the Philippines has been investigated using a mixture of laboratory and synchrotron techniques. Nickel laterite profiles are typically composed of complicated mineral assemblages, with Ni being distributed heterogeneously at the micron scale, and thus a high degree of spatial resolution is required for analysis. This study represents the first such analysis of Philippine laterite ores. Synchrotron bulk and microprobe X-ray absorption spectroscopy (XAS), comprising both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies, together with synchrotron microprobe X-ray fluorescence microscopy (XFM) and diffraction (XRD) have been applied to provide quantitative analysis of the mineral components and Ni speciation.Synchrotron microprobe EXAFS spectroscopy suggests that the limonite Ni is associated with phyllomanganate via adsorption onto the Mn oxide layers and substitution for Mn within these layers. Laboratory scanning electron microscopy, coupled to electron dispersive spectroscopy analyses, indicates that Ni is also associated with concentrated Fe containing particles and this is further confirmed by synchrotron bulk and microprobe investigation. Linear combination fitting of the bulk EXAFS limonite data suggests 60 ± 15% of the Ni is associated with phyllomanganate, with the predominant fraction adsorbed above vacancies in the MnO6 layers with the remainder being substituted for Mn within these layers. The remaining 40 ± 10% of the Ni in the limonite ore is incorporated into goethite through replacement of the Fe. In the saprolite ore, 90 ± 23% of the Ni is associated with a serpentine mineral, most likely lizardite, as a replacement for Mg. The remaining Ni is found within phyllomanganate adsorbed above vacancies in the MnO6 layers.  相似文献   

16.
Passive treatment systems are widely used for remediation of acid mine drainage (AMD), but existing designs are prone to clogging or loss of reactivity due to Al- and Fe-precipitates when treating water with high Al and heavy metal concentrations. Dispersed alkaline substrate (DAS) mixed from a fine-grained alkaline reagent (e.g. calcite sand) and a coarse inert matrix (e.g. wood chips) had shown high reactivity and good hydraulic properties in previous laboratory column tests. In the present study, DAS was tested at pilot field scale in the Iberian Pyrite Belt (SW Spain) on metal mine drainage with pH near 3.3, net acidity 1400–1650 mg/L as CaCO3, and mean concentrations of 317 mg/L Fe (95% Fe(II)), 311 mg/L Zn, 74 mg/L Al, 20 mg/L Mn, and 1.5–0.1 mg/L Cu, Co, Ni, Cd, As and Pb. The DAS-tank removed an average of 870 mg/L net acidity as CaCO3 (56% of inflow), 25% Fe, 93% Al, 5% Zn, 95% Cu, 99% As, 98% Pb, and 14% Cd, but no Mn, Ni or Co. Average gross drain pipe alkalinity was 181 mg/L as CaCO3, which increased total Fe removal to 153 mg/L (48%) in subsequent sedimentation ponds. Unfortunately, the tank suffered clogging problems due to the formation of a hardpan of Al-rich precipitates. DAS lifetime could probably be increased by lowering Al-loads.  相似文献   

17.
The authors determine the composition of a river that is impacted by acid-mine drainage, evaluate dominant physical and geochemical processes controlling the composition, and assess dissolved metal speciation and toxicity using a combination of laboratory, field and modeling studies. Values of pH increase from 3.3 to 7.6 and the sum of dissolved base metal (Cd + Co + Cu + Ni + Pb + Zn) concentrations decreases from 6270 to 100 μg/L in the dynamic mixing and reaction zone that is downstream of the river’s confluence with acid-mine drainage. Mixing diagrams and PHREEQC calculations indicate that mixing and dilution affect the concentrations of all dissolved elements in the reach, and are the dominant processes controlling dissolved Ca, K, Li, Mn and SO4 concentrations. Additionally, dissolved Al and Fe concentrations decrease due to mineral precipitation (gibbsite, schwertmannite and ferrihydrite), whereas dissolved concentrations of Cd, Co, Cu, Ni, Pb and Zn decrease due to adsorption onto newly formed Fe precipitates.  相似文献   

18.
The technique of diffusive gradients in thin films (DGT) was applied to obtain high-resolution vertical profiles of trace metals in sediment porewater of a eutrophic lake, Lake Chaohu. All sampling sediments were under anaerobic conditions with Eh values below 0, the redox potential profile in M4 was relatively stable, and higher Eh values in M4 than that in M1 were observed due to hydrodynamic effects. Fe, Mn and As exhibited closely corresponding profiles due to the co-release of Fe and Mn oxides and the reduction of As. Higher Fe and Mn concentrations and lower As concentrations were observed in M1 of the western half-lake than those in M4 of the eastern half-lake due to different sources and metal contamination levels in the two regions. Cu and Zn showed increasing concentrations similar to Mn and Fe at 1–2 cm depth of sediments, while DGT measured Co, Ni, Cd and Pb concentrations decreased down to 3–4 cm in the profiles. Co, Ni, Cu, Zn, Cd and Pb showed insignificant regional concentration variances in the western and eastern half-lakes. According to the R(C DGT/C centrifugation) values, the rank order of metal labilities decrease as follows: Fe (>1) > Cu, Pb, Zn (>0.9) > Co, Ni, Cd (>0.3) > Mn, As (>0.1).  相似文献   

19.
In laboratory experiments, we investigated the effect of five individual Fe-binding ligands: phaeophytin, ferrichrome, desferrioxamine B (DFOB), inositol hexaphosphate (phytic acid), and protoporphyrin IX (PPIX) on the Fe(II) photoproduction using seawater of the open Southern Ocean. Addition of 10-100 nM Fe(III) to open Southern Ocean seawater without the model ligands and containing; 1.1 nM dissolved Fe(III), 1.75 ± 0.28 equivalents of nM Fe of natural ligands with a conditional stability constant (log K′) of 21.75 ± 0.34 and a concentration DOC of 86.8 ± 1.13 μM C leads to the formation of amorphous Fe(III) hydroxides. These amorphous Fe(III) hydroxides are the major source for the photoproduction of Fe(II). The addition of the model ligands changed the Fe(II) photoproduction considerably and in various ways. Phaeophytin showed higher Fe(II) photoproduction than ferrichrome and the control, i.e., amorphous Fe(III) hydroxides. Additions of phytic acid between 65 and 105 nM increased the concentration of photoproduced Fe(II) with 0.16 nM Fe(II) per nM phytic acid, presumably due to the co-aggregation of Fe(III) and phytic acid leading via an increasing colloidal surface to an increasing photoreducible Fe(III) fraction. DFOB and PPIX strongly decreased the photoproduced Fe(II) concentration. The low Fe(II) photoproduction with DFOB confirmed reported observations that Fe(III) complexed to DFOB is photo-stable. The PPIX hardly binds Fe(III) in the open Southern Ocean seawater but decreased the photoproduced Fe(II) concentration by complexing the Fe(II) with a binding rate constant of kFe(II)PPIX = 1.04 × 10−4 ± 1.53 × 10−5 s−1 nM−1 PPIX. Subsequently, PPIX is suggested to act as a photosensitizing producer of superoxide, thus increasing the dark reduction of Fe(III) to Fe(II). Our research shows that the photochemistry of Fe(III) and the resulting photoproduced Fe(II) concentration is strongly depending on the identity of the Fe-binding organic ligands and that a translation to natural conditions is not possible without further characterization of the natural occurring ligands.  相似文献   

20.
Globally, the ongoing retreat of mountain glaciers will ultimately diminish fresh water supplies. This has already begun in watersheds with greatly reduced glacial coverage. Still unknown are the affects of glacial retreat on downstream water quality, including the threats to human and ecosystem health. In the Cordillera Blanca, retreating glaciers have exposed sulfide-rich rock outcrops, negatively affecting the quality of the glacial meltwater. This study has evaluated glacial melt stream hydrogeochemistry in the sulfide-bearing Rio Quilcay watershed (∼9°27′S, ∼77°22′W) during the 2008 dry season. Surface water samples were collected from the upper 12 km of the watershed during the 2008 dry season. Dissolved (0.4 μm) and unfiltered acidified (pH < 2) Al, Co, Cu, Fe, Ni, Mn, Pb, Zn and dissolved major ions and organic C (DOC) concentrations were quantified and pH and temperature were measured in the field. Twenty of 22 stream samples had pH values below 4, generating significantly (p < 0.01, α = 0.05) greater cation denudation normalized to discharge than other worldwide glacier-fed streams. Additionally, dissolved trace and minor element concentrations were comparable to acid mine drainage. Non-conservative dissolved element behaviors resulted from adsorption/desorption reactions in tributary mixing zones. At low pH values, hydrous Fe oxides acted as the dominant sorption surfaces. The poor water quality observed in Cordillera Blanca headwaters coupled with the likely exposure of additional sulfide-rich outcrops from ongoing glacial retreat may pose water quality challenges.  相似文献   

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