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1.
Analysis of river, estuary and marine sediments from the Atlantic coast of Spain using thermogravimetry–differential scanning calorimetry–quadrupole mass spectrometry–isotope ratio mass spectrometry (TG–DSC–QMS–IRMS) was used to (a) distinguish bulk chemical hosts for C within a sediment and humic acid fraction, (b) track C pools with differing natural C isotope ratios and (c) observe variation with distance from the coast. This is the first application of such a novel method to the characterisation of organic matter from marine sediments and their corresponding humic acid fractions. Using thermal analysis, a labile, a recalcitrant and a refractory carbon pool can be distinguished. Extracted humic fractions are mainly of recalcitrant nature. The proportion of refractory carbon is greatest in marine sediments and humic acid fractions. Quadrupole mass spectrometry confirmed that the greatest proportion of m/z 44 (CO2) and m/z 18 (H2O) were detected at temperatures associated with recalcitrant carbon (510–540 °C). Isotope analysis detected progressive enrichment in δ13C for the sediment samples with an increase in marine influence. Isotopic heterogeneity in the refractory organic matter in marine sediments could be due to products of anthropogenic origin or natural combustion products. Isotope homogeneity of humic acids confirms the presence of terrigenous C in marine sediments, allowing the terrestrial input to be characterised.  相似文献   

2.
Lignite samples from two deposits located in the Megalopolis Basin, Southern Greece, were evaluated for their potential applicability as raw materials for the production of organomineral fertilizers. Fundamental chemical analyses were carried out to demonstrate high humic substances and metal contents. To determine their relative distribution in the Megalopolis lignite extract, eight elements, namely Na, K, Cd, Mn, Mg, Pb, Zn, and Cu, were studied both in H2O and in Na4P2O7/NaOH solutions. The behavior of these metals showed significant variations; Zn, Pb, Cd, and Cu associate mostly to the humic substances and proved scarce in the water extract. Contrarily, K and Mg gave a significantly low total yield in the Na4P2O7/NaOH solution, while Mn was classified among the least extracted elements. Further enrichment of Megalopolis humic substances in these metals was achieved; Pb and Mg proved the most and least retained metal, respectively. Decomplexation titration curves of humic matter saturated with these metal ions demonstrated that novel organomineral fertilizing materials may develop based on optimized metal ion and humate contents, which can retain metals in a soluble form within a wide pH range. Formation of complexes between humic substances and Zn, Cd, and Mg was clearly indicated.  相似文献   

3.
Major and trace elements, organic matter, carbonates, loss of ignition, grain size, gravel, sand, silt, clay, and qualitative mineralogical composition were determined on surficial marine sediments sampled during the stormy (February), dry (May), and rainy (September) seasons in the coastal area adjacent to Panuco River discharges into the Gulf of Mexico. The sediments supplied by the river move in a north-east direction, and are deposited in the north-east extreme of the studied area. Terrigenous sediments show a strong association of Al2O3 with Fe2O3, Na2O, K2O, P2O5, Rb, Cu, Zn, organic matter, clay, and grain size (Mz). Mineralogical analysis shows that they are formed by quartz, kaolinite, montmorillonite, illite-montmorillonite and biotite. The highest metal concentration of Cu (25 mg/kg), Zn (155 mg/kg), Pb (50 mg/kg) and organic matter (1.26%) was observed in the sampling points located very close to the river mouth. A statistical analysis was done with the information contained in the variables. Five significant factors explain 77% of the total variance: factor 1 is due to sediments from a terrigenous source, factor 2 corresponds to sediments from a biogenous source, factor 3 is associated to sediments with heavy minerals, factor 4 is due to Co concentration, and factor 5 is due to Ni concentration. The sediments supplied from the river had a short-term local impact on the sediment distribution, as observed by the carbonate and heavy mineral concentration of the sediments.  相似文献   

4.
Eighty-six surface sediments collected from the northwestern continental shelf of the South China Sea (SCS) were analyzed for grain size distribution, calcium carbonate, organic carbon, and major and trace element compositions to investigate sediment provenance and factors controlling their geochemical composition. Sediments from the eastern continental shelf of Hainan Island have higher sand and lower clay content, while the samples from the nearshore Hainan Island have higher contents of gravel and clay. Calcium carbonate contents in samples show a positive correlation with water depth in northwestern shelf of SCS, suggesting that it is related to biological factors. However, the nearshore sediments have higher contents of organic carbon compared to those of the outer shelf, possibly suggesting that the terrigenous organic matter usually deposited in nearshore environments such as bays and estuaries. Compared with the upper continental crust, the samples have relatively lower contents of SiO2 and Al2O3, higher than those of the Pearl and Red river sediments. The low contents of K2O and Na2O in sediments from the northwestern continental shelf are consistent with intense chemical weathering in the river basin due to the seasonally hot and humid climate regime. The sediments mainly consist of three components, including the gravel fraction composed of calcareous debris, the sand fraction composed of quartz, and the silt and clay fractions mainly composed of clay minerals. The content of each component depends on grain size, sediment source, biogenesis, and hydrodynamic conditions, which finally controls the chemical composition of the sediments. The distributions of Co/Al2O3, Cr/Al2O3, and Zr/Sc ratios for sediments in the northwestern continental shelf suggest that source rocks are mainly composed of felsic rocks rather than mafic rocks. There is a distinct difference in sediment source between eastern and western shelf sediments; the eastern shelf sediments are characterized by high Zr/Sc ratios mainly derived from the Pearl River, while the western shelf sediments have relatively low values of Zr/Sc indicating a main contribution possibly sourced from the Red River Basin. Terrigenous materials from Hainan Island usually influence the geochemistry of sediments deposited in the nearshore area.  相似文献   

5.
Sixty sediment samples with a wide range of heavy‐metal concentrations and sediment textures were collected from Sydney Harbour. The samples were extracted with 1M HCl, 0.05M EDTA and HClO4/HNO3 and analysed by flame atomic absorption spectrometry for Zn, Pb, Cu and Cd. 1M HCl extracted a large proportion of heavy metals in oxic sediments (60–100%), whereas the extractability of metals with 0.05M EDTA was generally lower (by ～20%). Extractability was unrelated to the level of contamination or to sediment texture. The extractability of Cu in anoxic sediments was substantially lower with 1M HCl (～20%) and 0.05M EDTA (～10%) than with HClO4/HNO3. The extractability of Pb with 0.05M EDTA was also reduced in anoxic sediments (to ～70%). The use of weak extractants, in particular 1M HCl, is recommended by the recently introduced ANZECC and ARMCANZ interim sediment‐quality guidelines. These extractants are believed to provide a better measure of the bioavailable metal content than strong acid extractants. In this study, anoxic, sulfidic environments had a major influence on metal extractability with weak extractants. The implication of this is that the number of samples requiring further testing, as stipulated by the guidelines, would be significantly reduced in anoxic sediments.  相似文献   

6.
Lithium, boron, copper and zinc have been determined on cored and surface sediments from the delta and the drainage valley of the Nile River. The clay size fraction separated from the samples consists of montmorillonite and kaolinite as the predominant clay components, followed by illite and chlorite. Quartz and calcite are the non-clay admixtures.Lithium content varies between 7 and 48 ppm in the bulk sediments and between 28 and 61 ppm in the clay fractions, being clearly enriched in the clay material. In the clay fractions, concentration of lithium in kaolinite is indicated by a close relation between the lithium and kaolinite contents and is further supported by a close correlation with A12O3.Boron in the clay fraction (62–112 ppm) appears to be concentrated in detrital illite.The concentrations of copper (26–900 ppm) and zinc (65–333 ppm) in the clay fractions correlate positively with the CO2 percentage. Both elements tend to occur in or on the claysized grains of caleite.  相似文献   

7.
Spatial and temporal variation of heavy metals in a tropical estuary   总被引：6，自引：0，他引：6  
The lower part of the Coatzacoalcos River has great industrial development in which high pollution has been reported. Surface sediments of this area were studied over a year to observe spatial and seasonal sedimentological and chemical variations. Higher metal concentrations were found during the dry season, Pajaritos Dock and Teapa sampling points showing the highest values. Ni (182 ppm) and Co (37 ppm) concentrations are elevated relative to other estuarine areas. Metal normalization against Al2O3 content shows contaminant input in areas where urban and industrial discharges exist. A cluster analysis of the data separates sediment samples from the different sampling trips, suggesting the dynamic nature of the sediments. Through the statistical t-test, metal enrichment of Cd, Cu, Cr, Ni, Pb, and Zn was evaluated and compared with metal concentration in sediments of the river higher parts. The percentage of bioavailable metals is a function of the physicochemical characteristics of the system.  相似文献   

8.
Partitioning of transition elements in Pacific pelagic sediments (35 samples) was performed by sequential chemical leaching with barium chloride/triethanolamine (easily extractable fraction), acidic cation exchange resin (carbonate phases), and hydroxylamine hydrochloride and dilute hydrochloric acid solutions (hydrous oxides). Residual metal percentages are highest in red-brown clays and siliceous ooze, intermediate in calcareous materials and low in micronodules (2 samples, > 125 μm): residual metal contents seem to be controlled predominantly by the rate of admixture of volcanoclastic materials. At higher bulk metal concentrations, the non-residual fractions of Mn, Cu, Ni and Zn generally increase both in red-brown pelagic clays and in siliceous ooze. Mn, Ni, and Co concentrations are mainly associated with the easily reducible fraction (0.1 M NH2OH·HCl), whereas Fe, Cu, and Zn exhibit higher percentages in the hydrochloric acid soluble fractions (0.3 M HCl); Zn and Cu are associated to some extent with the carbonate phase, copper with the easily extractable fraction.  相似文献   

9.
River water (Water of Luce, Scotland) is used in laboratory experiments designed to investigate physical and chemical properties of Fe. Mn, Cu, Ni, Co, Cd and humic acids in riverine and estuarine systems. Using NaCl, MgCl2 and CaCl2 as coagulating agents, coagulation of dissolved (0.4 μm filtered) Fe, Cu, Ni, Cd and humic acids increases in a similar matter with increasing salt molarily: Ca2+ is the most dominant coagulating agent. Removal by coagulation with Ca2+ at seawater concentrations ranges from large (Fe-80%. HA-60%, Cu-40%) to small (Ni, Cd-15%) to essentially nothing (Cd, Mn-3%). Destabilization of colloids is the indicated mechanism. Solubility-pH measurements show that between a pH of 3 and 9, Fe, Cu, Ni, Mn, Co and Cd are being held in the dissolved phase by naturally occurring organic substances. Between pH of 2.2 and 1.2 a large proportion of dissolved Fe, Cu. Ni and Cd (72, 35,44 and 36% respectively) is precipitated along with the humic acids; in contrast, Mn and Co show little precipitation (3%). Adsorption-pH experiments, using unfiltered river water spiked with Cu, indicate that adsorption of Cu onto suspended particles is inhibited to a large extent by the formation of dissolved Cu-organic complexes.The experimental results demonstrate that solubilities and adsorption properties of certain trace metals in freshwaters can be opposite to those observed with artificial solutions or predicted with chemical models. Interaction with organic substances is a critical factor.  相似文献   

10.
The composition of humic acids (HAs) isolated from an agricultural soil and a lignite deposit was examined via H2O2 and RuO4 oxidation. The oxidation digests were separated into lipophilic and hydrophilic components. Information with regard to the source, degree of humification and preservation of easily degradable constituents of the HAs was obtained and results were compared with those obtained earlier for base hydrolysates of solvent-extracted fractions.H2O2 oxidation of both HAs afforded lipophilic fractions containing high molecular weight compounds. The composition of the base hydrolysates of the lipophilic fractions strongly differed with the origin of the HA. The lipophilic components of the soil HA derived mainly from the higher plant polyesters cutin and suberin. The lipophilic components of the lignite HA predominantly comprised long chain alkanoic acids and alkanols. The patterns for the hydrophilic components released upon H2O2 oxidation were found to be identical irrespective of the origin of the HA. The hydrophilic fractions comprised aliphatic (poly)carboxylic acids related to carbohydrate moieties and benzene polycarboxylic acids. The relative abundance of benzene polycarboxylic acids increased with the degree of humification.For both HAs, RuO4 oxidation resulted in a lipophilic fraction containing low molecular weight products identical to those found in the base hydrolysate of the lipophilic fraction released upon H2O2 oxidation. The hydrophilic components released upon RuO4 oxidation were independent of the HA origin and consisted mainly of monosaccharides and disubstituted aromatic compounds. In agreement with the greater aromaticity of lignite HA, the aromatic compound/carbohydrate ratio was higher for lignite HA than soil HA. The results show that the fused aromatic structures had a small size and that carbohydrates could escape degradation during the humification process.  相似文献   

11.
《Applied Geochemistry》1998,13(5):607-617
Distribution and forms of transition metals (Ti, Zn, Ni, Co, Mn, Fe, Cu, V and Cr) were investigated in oxidised, partly oxidised and reduced zones of sulphide-bearing fine-grained sediments located in the coastal areas of western Finland. Samples for the analysis and study of vertical distribution of elements were taken from each vertical 10 cm section in pits ranging in depth between 2 and 3 metres, while bulk samples for characterisation of species and forms of metals were taken from 3 zones in each pit: the acid sulphate soil (characterised by acid and oxidising conditions), transition zone (characterised by a steep pH gradient and partly oxidising conditions) and the reduced zone (pH >6). The former samples were digested in aqua regia (3:1:2 HCl:HNO3:H2O), while the latter were digested in aqua regia and hot concentrated acids (HClO4–HNO3–HCl–HF) and were subjected to extractions with acid ammonium acetate, H2O2 and acid ammonium oxalate. Each leachate was analysed for metals with ICP–AES.The vertical variation in the concentrations of Ti were small at all the studied sites indicating that the sediments are homogeneous and that the total losses of other elements from the soil profiles (acid sulphate soil+transition zone) are not extensive. Field observations, extractions with ammonium oxalate, and concentration–variation patterns indicated that Fe-oxide is largely precipitated and retained also in these acid soils. There are, however, indications of redistribution of Fe within the soil profiles. The results also demonstrated that Mn, Ni, Zn, Co and Cu have been lost in considerable amounts from the acid sulphate soils. However, whereas Mn in general has been lost throughout the soil profile, part of the Zn, Ni and Co released in the acid sulphate soils have migrated downward and been reimmobilised in the transition zone immediately above the reduced zone. Also Cu has been lost from the acid sulphate soil, but generally in smaller proportions than Mn, Zn, Ni and Co. Dissolved metal sulphides seem to be major sources of the mobilised metal fractions. A main part of the V and Cr in the sediments are associated with weathering-resistant minerals. These metals are therefore, like Ti, only to a limited extent mobilised by the oxidation of the sulphide-bearing sediments.  相似文献   

12.
The composition of river water, sediments, and pore waters (down to 30 cm below the bed) of Las Catonas Stream was studied to analyze the distribution of trace elements in a peri-urban site. The Las Catonas Stream is one of the main tributaries of Reconquista River, a highly polluted water course in the Buenos Aires Province, Argentina. The semi-consolidated Quaternary sediments of the Luján Formation are the main source of sediments for Las Catonas Stream. The coarse-grained fraction in the sediments is mainly composed of tosca (calcretes), intraclasts, bone fragments, glass shards, quartz, and aggregates of fine-grained sediments together with considerably amounts of vegetal remains. The clay minerals are illite, illite–smectite, smectite, and kaolinite. For the clay-sized fraction, the external surface area values are mostly between 70 and 110 m2g?1, although the fraction at 15 cm below the bottom of the river shows a lower surface area of 12 m2g?1. The N2 adsorption–desorption isotherms at 77 K for this sample display a behavior indicative of non-porous or macroporous material, whereas the samples above and below present a typical behavior of mesoporous materials with pores between parallel plates (slit-shaped). As, Cr, Cu, and Cd concentrations increase down to 15 cm depth in the sediments, where the highest trace element and total organic carbon (TOC) concentrations were found, and then decrease toward the bottom of the core. Except for As, the levels of the other heavy metals show higher concentration in surficial waters than in pore waters. Distribution coefficients between the sediments, pore water, and surficial water phases indicate that As is released from the sediments to the pore and surficial waters. Cu content strongly correlates with TOC (mainly from vegetal remains), suggesting that this element is mainly bound to the organic phase.  相似文献   

13.
《Applied Geochemistry》1996,11(4):605-616
Lake Valencia is a tropical lowland lake in north-central Venezuela. Lake bottom sediments were collected from 25 locations in April, 1988. At 2 locations water pH, conductivity, dissolved O2 and temperature were measured at successive depths. After drying, 5 sediment samples were sieved into 5 mechanical fractions. Each was extracted with 1 M HNO3 and analysed for AI, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb and Zn. The <63 μm fraction of all samples was similarly analysed. Water temperatures declined with depth (1°C/25 m) from approximately 26°C. Conductivity varied little with depth but dissolved O2 contents indicated anoxic conditions < 25 m. Water pH (8.8–9.4) was consistent with high dissolved carbonates. There was little consistent relationship between grain size and sediment metal contents. Approximate baseline metal contents were calculated from 21 of 25 samples. The average composition of the sediments corresponded to an ideal mixture of shales/carbonate rocks as 0.5–0.7/0.5-0.3. Five samples from alluvial fans near the mouths of rivers traversing urban-industrial zones had compositions different from the other sediments. Generally, Ph, Zn, Ni, Cd and Cu were anthropogenically enriched by factors of 2–16. The major sources of pollutants were identified as domestic and industrial activities affecting the rivers that traverse the lakeside cities of Maracay and Valencia. Sodium, Mg, Ca, Mn and CO3− showed natural enrichment arising from carbonate precipitation following a physical mixing of 2 sedimentary components (biogenic carbonate and terrigenous material). Low geochemical mobility of metallic elements in neutral-basic and reducing waters, a processes of bury and mixture of sediments and precipitation of carbonate result in only 10% of the lake area being affected by contamination. Isoline plots of elements in the bottom sediments supported a hypothesis that material mixing, physical transport and carbonate precipitation are the main controls of spatial distribution patterns.  相似文献   

14.
Dongping Lake area, located in the lower reaches of Yellow River, is an ideal place to study the changes of modern river and lake sedimentary environment. The sediment samples of Dawen River, Yellow River, and Dongping Lake were collected, and the major elements, trace elements and organic matter geochemical composition of the samples were analyzed. Cluster analysis, characteristic element ratio method and graphic method were used to explore the geochemical characteristics of sediments and their environmental implication. The results show that the contents of SiO_2, Na_2O, TiO_2 and Zr in sediments of Dawen River and Yellow River are relatively high, and the contents of iron and manganese oxides, organic matter, CaO, P_2O_5 and Sr in lake sediments are relatively high. That reveals the differences of sedimentary environments between the rivers and the lake. The contents of Sr and Zr in Dawen River are affected by the rapid migration of clastic materials in the upstream carbonate source area during the flood season; the δCe,ΣREE and REE's ratios in the sediments of the Yellow River reflect the influence of the Loess source; and the distribution of elements changes along the flow direction during the flood season. The characteristics of p H, element composition and LREE HREE fractionation of the lake sediments indicate that the sediment source is complex, and the lake environment is affected by the flood season. The study shows that the geochemical content and its variation characteristics of sediments effectively reveal the sedimentary environment, material composition and characteristics of flood season of rivers and the lake in the study area.  相似文献   

15.
 Heavy metal and metalloid concentrations within stream-estuary sediments (<180-μm size fraction) in north-eastern New South Wales largely represent natural background values. However, element concentrations (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn) of Hunter River sediments within the heavily industrialized and urbanized Newcastle region exceed upstream background values by up to one order of magnitude. High element concentrations have been found within sediments of the Newcastle Harbour and Throsby Creek which drains into urbanized and light industry areas. Observed Pb enrichments and low 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb ratios are likely caused by atmospheric deposition of Pb additives from petrol and subsequent Pb transport by road run-off waters into the local drainage system. Sediments of the Richmond River and lower Manning, Macleay, Clarence, Brunswick and Tweed River generally display no evidence for anthropogenic heavy metal and metalloid contamination (Ag, As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, Zn). However, the rivers and their tributaries possess localized sedimentary traps with elevated heavy metal concentrations (Cu, Pb, Zn). Lead isotope data indicate that anthropogenic Pb provides a detectable contribution to investigated sediments. Such contributions are evident at sample sites close to sewage outlets and in the vicinity of the Pacific Highway. In addition, As concentrations of Richmond River sediments gradually increase downstream. This geochemical trend may be the result of As mobilization from numerous cattle-dip sites within the region into the drainage system and subsequent accumulation of As in downstream river and estuary sediments. Received: 5 September 1997 · Accepted: 4 November 1997  相似文献   

16.
《Applied Geochemistry》2002,17(8):1159-1164
Fly ash was modified by hydrothermal treatment with 7 M NaOH. The resultant product displayed an 8-fold increase in surface area. The primary crystalline component of the modified fly ash was identified by X-ray diffraction to be hydroxysodalite (Na6Al6Si6O248H2O). The cation exchange capacity of the modified ash was significantly increased over that of the raw fly ash (188 vs 2 meq g−1). Adsorption experiments showed that the modified fly ash adsorbed a cationic dye (methylene blue) to a much greater extent than an anionic dye (alizarin sulfonate). Saturation adsorption revealed that the capacity of the ash for methylene blue had increased 10-fold during modification when compared to the raw ash. Adsorption is thus ascribed to be a surface effect rather than involving incorporation into the channels of the hydroxysodalite structure.  相似文献   

17.
The early diagenetic environment of intertidal sandy sediments (sands) and muddy sediments (muds) is described and compared from two cores taken from an unpolluted part of the Manukau Harbour, New Zealand. Extraction techniques characterized the form of the trace elements (Fe, Mn, S, C, Pb, Zn, Cu) at different depths in the sediment. Dissolved forms of Fe, Mn, and S were measured in interstitial water. Nonresidual metal concentrations, humic acid, FeS, and FeS2 are an order of magnitude higher in the muds than in the sands because of dilution by unreactive sand particles. Muds contain a larger proportion of metals in the mobile fractions; exchangeable (Mn), carbonate (Mn, Fe, Zn), and easily-reducible oxide (Fe, Mn, Zn, Pb). This is due to greater surface area (for Mn adsorption); the favorable conditions for MnCO3, FeCO3, and FeS precipitation; and higher concentrations of easily reducible iron oxide and humic acid. Therefore, compared to the sands, muds are more important as reservoirs for toxic metals, both in terms of quantity and availability. At either site there was very little difference between the forms of Zn, Pb or Cu identified by sequential extraction as sediments changed from oxic to anoxic conditions. One reason for this is that the amounts and proportions of some of the important components that bind metals, viz., amorphous iron hydrous oxides, humic acids, and FeS2, do not change much. Other components that do change with redox conditions, for example, manganese phases and FeS, are only minor components of the sediment. Redox conditions, then, have relatively little effect on trace-metal partitioning in the sediment matrix of these unpolluted sediments.  相似文献   

18.
Fresh flood deposits were sampled in the flood-plains of two river systems, the River Meuse, with a catchment area of 33,000 km2 and the River Geul, with a catchment area of 3,000 km2. As a result of industrial and mining activities, both rivers have a history of severe metal pollution, especially with zinc, lead, and cadmium. The flood deposits of both rivers are heterogeneous mixtures of contaminated bottom sediments (with relatively long residence times in the river) and clean sediments derived from soil erosion on agricultural cropland (with very short residence times). An additional source of sediment is formed by erosion of older, locally highly contaminated streambank deposits. These older sediments are polluted as a result of solid waste disposal containing metalliferous ore and tailings in the sand fraction. This is especially the case in the River Geul, which drains an old zinc and lead mining area. The metal content of the Meuse sediments, however, originates largely from liquid industrial wastes and occurs mainly in the clay fraction. For this reason, the positive correlation between textural composition, organic matter content, and heavy metal concentration, which is often reported, was not observed, and normalization of the metal content was not possible. Nevertheless, a clear decrease of contamination was noticed along the River Geul; this trend was absent along the River Meuse. An attempt has been made to model the longitudinal decay pattern for each of the investigated havey metals.  相似文献   

19.
Mobility of heavy metals from coal fly ash   总被引：7，自引：0，他引：7  
The mobility of Cd, Co, Cu, Ni, Pb, Sb, and Zn from six different coal-fired power plant fly ashes that show a wide compositional range was examined using a sequential extraction procedure in order to assess their mobility when these wastes are ponded or landfilled. The extraction sequence was as follows: (1) water extractable, (2) cation exchangeable (CH3COONH4 at pH 7), (3) surface oxide-bound cations (CH3COONH4 at pH 5), (4) Fe oxide-bound cations (HONH3Cl), and (5) residual (HF, HCl, HNO3, 211). The heavy metal contents in the extraction solutions were determined by anodic (Cd, Cu, Pb, Sb, and Zn) and cathodic (Ni and Co) stripping voltammetry. The results reveal differences in the total contents of the selected trace elements among the fly ash samples, which must be related to differences in coal composition and combustion technology. The extractable fraction under natural conditions ranges from 1.5 to 36.4 percent of the total element content. Cadmium, Co, Cu, and Zn show the highest extractable fraction (10.8–18.9 percent on average). Cadmium is the most easily water-extractable element, while Co, Cu, and Zn increase their mobility as the severity of the extraction increases. Cobalt, Ni, Pb, and Zn are mainly associated with the surface oxide-bound and Fe oxide-bound fractions. Nickel, Pb, and Sb have low mobility potentials (5.3–6.6 percent as extractable fraction), but Sb presents a relatively high water-extractable fraction.  相似文献   

20.
Pu  Wanqiu  Sun  Jiaqi  Zhang  Fangfang  Wen  Xingyue  Liu  Wenhu  Huang  Chengmin 《中国地球化学学报》2019,38(5):753-773

Metallic ore mining causes heavy metal pollution worldwide. However, the fate of heavy metals in agrosystems with long-term contamination has been poorly studied. Dongchuan District (Yunnan, southwest China), located at the middle reaches of the Xiaojiang River, is a well-known 2000-year-old copper mining site. In this work, a survey on soil heavy metal contents was conducted using a handheld X-ray fluorescence instrument to understand the general contamination of heavy metals in the Xiaojiang River Basin. Furthermore, river water, soil, and rice samples at six sites along the fluvial/alluvial fans of the river were collected and analyzed to implement an environmental assessment and an evaluation of irrigated agrosystem. V, Zn, and Cu soil levels (1724, 1047, and 696 mg·kg−1, respectively) far exceeded background levels. The geo-accumulation indexes (Igeo) showed that cultivated soils near the mining sites were polluted by Cd and Cu, followed by Zn, V, Pb, Cr, Ni, and U. The pollution index (Pi) indicated that rice in the area was heavily polluted with Pb, Cr, Cd, Ni, Zn, and Cu. The difference in orders of metal concentrations between the soil and rice heavy metal contamination was related to the proportion of bioavailable heavy metals in the soil. The crop consumption risk assessment showed that the hazard quotient exceeded the safe threshold, indicating a potential carcinogenic risk to consumers. The Nemerow integrated pollution index and health index indicated that the middle of the river (near the mining area) was the heaviest polluted site.

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