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1.
The vertical variation of P forms in sediments of urban shallow lakes in China, Xuanwu Lake, Daming Lake and Mochou Lake, were sequentially extracted and measured with the method of SEDEX. The results indicated the TP content in the sediment profiles ranged from 371.94 to 777.25 mg kg−1 for Xuanwu Lake, 1,308.14 to 4,632.63 mg kg−1 for Daming Lake, and 995.49 to 1,860.71 mg kg−1 for Mochou Lake. The results of sequential extraction showed that Ca-P and Fe-P were the main fractions. Meanwhile, the proportions of Bio-P to TP were 35.24% for Xuanwu Lake, 29.57% Daming lake, and 25.26%, for Mochou Lake, indicating a high potential of P releasing. The content of Bio-P was significantly and positively correlated with TP (r = 0.978, P < 0.01). Lake hydrations conditions played an important role in the distribution and contents of Bio-P and TP. In the region with macrophytes, the contents of TP and Bio-P were relatively low. Physicochemical properties of sediments were significantly related to the fraction distribution and P contents, and might play an important role in controlling P activity and mobility. Moreover, Fe showed an evident influence on P fraction and the ratio Fe/P might be good indicator to the contents and composition of active P in sediments.  相似文献   

2.
We investigated the effects on phosphorus (P) release of the addition of potato, wheat, and sunflower residues and fruit compost to five calcareous soils. Residue was added at the rate of 20 g kg−1. After 2 months of incubation, P values in control and amended soils were used for kinetic studies and fractionated by a sequential extraction procedure. The relative contribution of available P fraction (KCl-P) increased from 1.4% in control soils to 1.8%, 1.9%, 2.2%, and 2.3% in soils amended by fruit, wheat, potato, and sunflower residue addition, respectively, indicating that organic residues increased P in this fraction. In soils amended with different residues, the percentage of Olsen-P released over 86-h successive extractions with 0.01 M CaCl2 ranged from 57.6% for fruit residue addition (average of five soils) to 60.5% for potato residue addition. The ability of residues to release P depended on the soil properties, with 21.9 mg kg−1 (average of all residues) released to soil 2 and 77.4 mg kg−1 released to soil 4. Also residues behaved differently, with 31.5 mg kg−1 (average of five soils) released by fruit residues and 40.0 mg kg−1 released by sunflower residues. Release of P was best described by a parabolic diffusion model. The corresponding rate constant (mg kg−1 h−1/2) for P release for amended soils, defined as the release rate averaged for five soils, was found to decrease in the order: potato (2.73) > sunflower (2.61) > wheat (2.56) > fruit (2.50). The present study demonstrates that addition of residues improves P availability of these calcareous soils by increasing extractable P and the release rate and could be an alternative, indigenous source of P. However, the increase in P availability and the release rate following organic residue application suggests high potential mobility to water sources.  相似文献   

3.
 Sediments in the rivers and basins around Washington, DC, have high concentrations of phosphorus, which, based on geographic distributions, is largely derived from urban runoff and municipal sewage. Dissolved-particulate phosphate exchange reactions and biological uptake of dissolved phosphorus from the water column may be an added source of phosphorus to the sediments. Concentrations of total sedimentary phosphorus ranged from 24 to 56 μm P/g-dw, and were highest in areas near combined sewer outfalls. As a part of this study, sedimentary phosphorus was fractionated into Fe-P, Ca-P, Al-P, and organic phases using a selective-sequential leaching procedure. The distribution of the phases in all sediments analyzed follow the order , Fe-P>Ca-P>Al-P. Spatial variations in the amounts of phosphorus in the different phases is related to the sources of phosphorus to the area. The proportions of occluded Al-P and organic P are 10–20% of the total P, respectively. This suggests that phosphorus from natural sources is small compared to anthropogenic inputs in this area. The high leachable Fe-P and Ca-P in these sediments might contribute a substantial amount of P to the water column under conditions of remobilization. Received: 20 February 1996 · Accepted: 2 April 1996  相似文献   

4.
The Sarcheshmeh copper mine smelter plant is one of the biggest copper producers in Iran. Long-time operation of about 25 years of the smelter plant causes release of potentially toxic heavy metals into the environment. In this paper, geochemical distribution of toxic heavy metals in 28 soil samples was evaluated around the Sarcheshmeh smelter plant. Soils developed over the nonmineralized and uncontaminated areas have an average background concentration of 41.25 mg kg−1 Cu, 26.6 mg kg−1 As, 12.7 mg kg−1 Pb, 0.9 mg kg−1 Sb, 1.9 mg kg−1 Mo, 1.7 mg kg−1 Sn, 0.2 mg kg−1 Cd, 0.15 mg kg−1 Bi, 235 mg kg−1 S and 73.4 mg kg−1 Zn, respectively. As a result of smelting process, the upper soil layers (0–5 cm) were polluted by Cu (>1,397 mg kg−1), Cd (>3.42 mg kg−1), S (>821 mg kg−1), Mo (>10.3 mg kg−1), Sb (>11.7 mg kg−1), As (>120.6 mg kg−1), Pb (>83.8 mg kg−1), Zn (>214.9 mg kg−1), and Sn (>3.7 mg kg−1), respectively. These values are much higher than the normal concentration of the elements in the uncontaminated soil layers. The elemental values decrease with distance travelled away of the smelter plant, especially at minimum wind direction. Furthermore, high contaminated values of Cu (8,430 mg kg−1), As (500 mg kg−1), Pb (331 mg kg−1), Mo (61 mg kg−1), Sb (56.2 mg kg−1), Zn (664 mg kg−1), Cd (17.2 mg kg−1), Bi (13.4 mg kg−1), and S (3,780 mg kg−1) were observed in the upper soil layers close to the smelting waste dumps. Sequential extraction analysis shows that about 270 mg kg−1 Cu, 28 mg kg−1 Pb, 50.33 mg kg−1 Zn, and 47.84 mg kg−1 As were adsorbed by Fe and Mn oxides. The carbonate phases include 151 mg kg−1 Cu, 28 mg kg−1 Pb, 25 mg kg−1 Zn, and 32.99 mg kg−1 As. Organic matter adsorbed 314.6 mg kg−1 Cu and 29.18 mg kg−1 Zn.  相似文献   

5.
An investigation was carried out to survey the magnitude and spatial distribution of heavy metals, as well as their relation with soil series, in a valley plain in Southeastern China. Soil was sampled at 159 sites by combining a squared grid and nested sampling strategies along the transect perpendicular to the Qujiang River in Zhejiang Province, China. Total concentrations of six metals, namely Cu, Fe, Mn, Ni, Pb and Zn, were measured. Classical statistics and geostatistics were used to quantify their spatial characteristics. There was a considerable variation in many of these parameters. The total concentrations ranged from 6.8 to 29.3 mg kg−1 for Cu, 6,784 to 18,678 mg kg−1 for Fe, 94 to 385 mg kg−1 for Mn, 6.1 to 20.3 mg kg−1 for Ni, 25.0 to 49.5 mg kg−1 for Pb, and 12 to 160 mg kg−1 for Zn. Pearson correlation coefficients among total metal concentrations and selected soil properties showed a number of strong associations. By virtue of analysis of variance, a predominant influence of soil series on the spatial variability of metal concentrations was observed. All metals were spatially correlated. The semivariograms of Cu, Fe, Mn, Ni and Zn were dominated by short range correlation (600 or 700 m), and that of Pb by long range (1200 m). Block kriging maps of total metal concentrations and soil properties showed strip distributions, perpendicular to the river, in the manner similar to the soil series. Principal component analysis was run to identify common distribution patterns of heavy metals and soil properties. These results illustrate that soil series information of valley plain may be useful for developing management zones for site-specific agriculture.  相似文献   

6.
Xiamen Bay (XMB) has received substantial loadings of pollutants from industrial and municipal wastewater discharged since the 1980s. To assess ecological risks and the current spatial changes of metal contaminants in bottom surface sediments, 12 samples were collected. Samples were subjected to a total digestion technique and analyzed by ICP–OES for Cu, Pb, Zn, Cr, and Cd, and by AFS for Hg and As. Among these metals, Zn had the highest values (68–268 mg kg−1), followed by Pb (27–71 mg kg−1), and lower concentrations were found for Cd (42–1,913 μg kg−1) and Hg (0–442 μg kg−1). In comparison with the average crustal abundance values, the results indicated that nearly half of the sediment samples of XMB and its adjacent areas were contaminated by Cd, Pb, Zn, and As. Furthermore, based on the modified BCR sequential extraction procedure, the chemical speciation of heavy metals (Cd, Cr, Cu, Pb, Zn, Hg, and As) in selected sediment samples were evaluated in this study. Data from BCR sequential extractions indicated that Cd posed a medium ecological risk, whereas, Cr posed low risk since its exchangeable and carbonate fractions were below 4%, and the mobility of heavy metals in XMB decreased in the order Cd > Pb > Cu > Zn > Hg > As > Cr. By applying mean effects range median quotients (mERMQ), the results showed that Yuandang Lagoon with mERMQ value >0.5 would be expected to have the greatest potential toxic risk in amphipod within XMB and its adjacent areas.  相似文献   

7.
Ten highly weathered soils in southeastern Nigeria were sampled from their typical A and B horizons for analyses. The objectives were to determine the different forms of Fe and Al oxides in the soils and relating their occurrence to phosphate availability and retention in the soils. The soils are deep and often physically degraded but are well drained and coarse in the particle size distribution. They are mostly dominated by kaolinite in their mineralogy with very high values of SiO2. The soils are acidic with low soil organic carbon (SOC) contents. The elements in the exchange complex are also low thus reflecting in the low CEC of the soil. Available phosphorus (P) in the soils are generally low while total P ranged from 157 to 982 mg kg−1 with an overall average of 422 mg kg−1. Total Fe in the soil is highest and their order represented as follows: Fet > Fed > Feox ≥ Fep. The pyrophosphate extractable Fe was always higher in the top soil than in the subsoil and was attributed to the fact that these forms of Fe are associated with organic matter which is more abundant in topsoil than in subsoil. Like in Fe forms, the order of Al occurrence could generally be presented as; Alt > Ald > Alox > Alp. More Fe and Al oxides in the soils are strongly crystalline while a small quantity is poorly crystalline Fe forms. The amorphous forms of both Fe and Al are very low in the soils when compared with the crystalline forms. The oxides that show very strong affinity to total P are Fed–Feox, Fed, Ald, Fet, Feox and Alox/Ald. To overcome this problem of P retention in the soil, we recommend constant liming of these soils to neutralize them, application of organic matter and of high dosage of phosphate fertilizer to the soils.  相似文献   

8.
Phosphorus (P) is the limiting macronutrient for primary production in most lakes. Sediment characteristics are strongly correlated to the internal P loading in lakes. This study investigated speciation of P, Fe, Al, and Ca in sediments of six sampling sites with varying trophic status in Baiyangdian Lake of North China during the period of July 2008 and March 2009. The results of sequential extraction experiments of the top sediments showed that total extractable P ranged approximately from 13 to 28 μmol g−1 for all sampling sites and the rank order of P-fractions was HCl–P > NaOH85–P > NaOH25–P > BD–P > NH4Cl–P. BD–P and BD–Fe had a consistent change with seasons. Their concentrations were both much higher in early spring and mid-autumn. BD–Fe, Al extracted with NaOH at 25°C and 85°C affected corresponding P concentration in sediments, while high concentration of extractable Ca from sediments showed no direct effects. According to the Kopáček et al. model of the molar ratios of Al:Fe and [NaOH25–Al]:[NH4Cl–P + BD–P], there was potential P release from sediments twice a year for some hypereutrophic sites in early spring and mid-autumn, especially in the former season.  相似文献   

9.
Vertical profiles of trace metal (Cd, Pb, Zn, Cu, Ni) concentrations, organic matter content, carbonate content and granulometric composition were determined in two sediment cores from the submarine pit Dragon Ear (Middle Adriatic). Concentrations of the analyzed metals (Cd: 0.06–0.12 mg kg−1, Pb: 28.5–67.3 mg kg−1, Zn: 17.0-65.4 mg kg−1, Cu: 21.1–51.9 mg kg−1, Ni: 27.8–40.2 mg kg−1) were in usual range for Adriatic carbonate marine sediments. Nevertheless, concentrations of Cu, Zn, and especially Pb in the upper layer of sediments (top 12 cm) were higher than in bottom layer, while Cd and Ni concentration profiles were uniform. Regression analysis and principal component analysis were used to interpret distribution of trace metals, organic matter and carbonate content in sediment cores. Results of both analysis showed that concentrations of all trace metals in the core below the entrance to the pit were significantly positively correlated with organic matter and negatively correlated with carbonate, while in the core more distant from the entrance only Pb showed significant positive correlation with organic matter. Obtained results indicated that, except for lead which was enriched in surface sediment, in the time of sampling (before the building of the nautical marina) investigated area belonged to unpolluted areas.  相似文献   

10.
The rare earth elements (REEs) in the sediments of the Xianghai wetlands were measured by inductively coupled plasma spectrometry. The REEs accumulation rates in two sedimentation cores derived from the riparian and depressional marshes were determined by 210Pb method. The results showed that REEs concentrations in the Xianghai wetland sediments (∑REEs, 116 mg kg−1) were lower than the corresponding values in Chinese soils (181 mg kg−1) and river sediments (∑REEs, 158–191 mg kg−1). Under alkaline conditions (with pH, 8.2–10.3), the light REEs were more enriched than the heavy REEs. Cerium is the predominant element, and accounts for 30–33% of the total REEs. REEs in the depressional marsh sediments were relatively high (∑REEs, 127 vs. 104 mg kg−1), especially light REEs contents. A significantly positive correlation was found between the neighboring elements except Pr and Dy. The different types of vertical distribution of REEs between the riparian and the depressional marsh can partly result from long-term differing hydrological regimes. Generally, depressional marsh had accumulated much more REEs than riparian marsh (the mean accumulation rates of ∑REEs, 102.98 vs. 48.89 μg cm−2 year−1).  相似文献   

11.
The release of Phosphorus (P) from river sediments has been identified as a contributing factor to waters failing the criteria for ‘Good Ecological Status’ under the EU Water Framework Directive (WFD). To identify the contribution of sediment-P to river systems, an understanding of the factors that influence its distribution within the entire non-tidal system is required. Thus the aims of this work were to examine the (i) total (PTotal) and labile (PLabile) concentrations in sediment, (ii) the sequestration processes and (iii) the interactions between sediment P and the river water in the six non-tidal water bodies of the River Nene, U.K. Collection of sediments followed a long period of flooding and high stream flow. In each water body, five cores were extracted and homogenised for analysis with an additional core being taken and sampled by depth increments. Comparing the distribution of sediment particle size and PTotal data with soil catchment geochemical survey data, large increases in PTotal were identified in sediments from water body 4–6, where median concentrations of PTotal in the sediment (3603 mg kg−1) were up to double those of the catchment soils. A large proportion of this increase may be related to in-stream sorption of P, particularly from sewage treatment facilities where the catchment becomes more urbanised after water body 3. A linear correlation (r = 0.8) between soluble reactive phosphate (SRP) and Boron in the sampled river waters was found suggesting increased STW input in water bodies 4–6.PLabile concentrations in homogenised cores were up to 100 mg kg−1 PO4–P (generally < 2% of PTotal) and showed a general increase with distance from the headwaters. A general increase in Equilibrium Phosphate Concentrations (EPC0) from an average of 0.9–∼1.7 μm L−1 was found between water bodies 1–3 and 4–6. Fixation within oxalate extractable phases (Al, Fe and Mn) accounted for ∼90% of P binding in water bodies 4–6, but only between 31 and 74% in water bodies 1–3. Statistical models predicting PTotal (R2 = 0.78), oxalate extractable P (R2 = 0.78) and Olsen P (R2 = 0.73) concentrations in river sediments identified Mn oxy-hydroxides (MnOx) as a strong predictive variable along with the location within the river system. It is suggested that MnOx within model predictions is identifying a pool of mixed Fe–Mn oxy-hydroxides (MnOx–FeOOH) or Fe oxy-hydroxide (FeOOH) from the wider FeOxalate pool that are particularly effective at sorbing and fixing P. The findings demonstrate how sediment and P may accumulate along a 100 km non-tidal river system, the extent to which a range of processes can fix P within mineral phases and how natural flooding processes may flush sediment from the river channel. The processes identified in this study are likely to be applicable to similar river systems over their non-tidal water bodies in eastern England.  相似文献   

12.
The Cu–Co–Ni Texeo mine has been the most important source of Cu in NW Spain since Roman times and now, approximately 40,000 m3 of wastes from mine and metallurgical operations, containing average concentrations of 9,263 mg kg−1 Cu, 1,100 mg kg−1 As, 549 mg kg−1 Co, and 840 mg kg−1 Ni, remain on-site. Since the cessation of the activity, the abandoned works, facilities and waste piles have been posing a threat to the environment, derived from the release of toxic elements. In order to assess the potential environmental pollution caused by the mining operations, a sequential sampling strategy was undertaken in wastes, soil, surface and groundwater, and sediments. First, screening field tools were used to identify hotspots, before defining formal sampling strategies; so, in the areas where anomalies were detected in a first sampling stage, a second detailed sampling campaign was undertaken. Metal concentrations in the soils are highly above the local background, reaching up to 9,921 mg kg−1 Cu, 1,373 mg kg−1 As, 685 mg kg−1 Co, and 1,040 mg kg−1 Ni, among others. Copper concentrations downstream of the mine works reach values up to 1,869 μg l−1 and 240 mg kg−1 in surface water and stream sediments, respectively. Computer-based risk assessment for the site gives a carcinogenic risk associated with the presence of As in surface waters and soils, and a health risk for long exposures; so, trigger levels of these elements are high enough to warrant further investigation.  相似文献   

13.
Riverbank sediment cores and pore waters, shallow well waters, seepage waters and river waters were collected along the Meghna Riverbank in Gazaria Upazila, Bangladesh in Jan. 2006 and Oct.–Nov. 2007 to investigate hydrogeochemical processes controlling the fate of groundwater As during discharge. Redox transition zones from suboxic (0–2 m depth) to reducing (2–5 m depth) then suboxic conditions (5–7 m depth) exist at sites with sandy surficial deposits, as evidenced by depth profiles of pore water (n = 7) and sediment (n = 11; diffuse reflectance, Fe(III)/Fe ratios and Fe(III) concentrations). The sediment As enrichment zone (up to ∼700 mg kg−1) is associated with the suboxic zones mostly between 0 and 2 m depth and less frequently between 5 and 7 m depth. The As enriched zones consist of several 5–10 cm-thick dispersed layers and span a length of ∼5–15 m horizontally from the river shore. Depth profiles of riverbank pore water deployed along a 32 m transect perpendicular to the river shore show elevated levels of dissolved Fe (11.6 ± 11.7 mg L−1) and As (118 ± 91 μg L−1, mostly as arsenite) between 2 and 5 m depth, but lower concentrations between 0 and 2 m depth (0.13 ± 0.19 mg L−1 Fe, 1 ± 1 μg L−1 As) and between 5 and 6 m depth (1.14 ± 0.45 mg L−1 Fe, 28 ± 17 μg L−1 As). Because it would take more than a few hundred years of steady groundwater discharge (∼10 m yr−1) to accumulate hundreds of mg kg−1 of As in the riverbank sediment, it is concluded that groundwater As must have been naturally elevated prior to anthropogenic pumping of the aquifer since the 1970s. Not only does this lend unequivocal support to the argument that As occurrence in the Ganges-Brahmaputra-Meghna Delta groundwater is of geogenic origin, it also calls attention to the fate of this As enriched sediment as it may recycle As into the aquifer.  相似文献   

14.
The pollution and deterioration of most important vital rivers in the Katanga region, Democratic Republic of Congo (DRC) are mainly due to the discharge of untreated industrial effluents as well as to the mining and artisanal mineral exploitation activities. In this study, the concentrations of metals (Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, and Pb) and major elements (Na, Mg, and K) in mining effluents, water and sediment samples of two main rivers of the district of Kolwezi (Katanga, DRC) were subjected to analysis by Inductive Coupled Plasma-Mass Spectroscopy (ICP-MS). The results showed that, in general, the metal concentrations in the sampling sites from the mining effluent and river waters exceed largely the World Health Organization and the Aquatic Quality Guidelines for the Protection of Aquatic Life recommendation limits. The highest metal concentrations in water and sediment samples were detected surrounding the mining effluents discharge. In the surface sediments of Luilu River, the values of 47,468 and 13,199 mg kg−1 were observed for Cu and Co, respectively. For the sediment samples from Musonoie River, the maximum values of 370.8 and 240.6 mg kg−1 for Cu and Co, respectively were observed. The results of this study suggest that the mining effluents being discharged into the rivers and the accumulation of pollutants in sediments might represent a source of toxicity for aquatic living organisms and could pose significant human health risks. The measures to establish a monitoring program and the application of wastewater treatment techniques to the mining effluents prior to discharge are recommended to reduce the load of contaminants into the receiving systems.  相似文献   

15.
We studied the mobility of silver, heavy metals and europium in waste from the Las Herrerías mine in Almería (SE Spain). The most abundant primary mineral phases in the mine wastes are hematite, hydrohematite, barite, quartz, muscovite, anorthite, calcite and phillipsite. The minor phase consisted of primary minerals including ankerite, cinnabar, digenite, magnesite, stannite, siderite and jamesonite, and secondary minerals such as glauberite, szomolnokite, thenardite and uklonscovite. The soils show high concentrations of Ag (mean 21.6 mg kg–1), Ba (mean 2.5%), Fe (mean 114,000 mg kg–1), Sb (mean 342.5 mg kg–1), Pb (mean 1,229.8 mg kg–1), Zn (mean 493 mg kg–1), Mn (mean 4,321.1 mg kg–1), Cd (mean 1.2 mg kg–1) and Eu (mean 4.0 mg kg–1). The column experiments showed mobilization of Ag, Al, Ba, Cu, Cd, Eu, Fe, Mn, Ni, Sb, Pb and Zn, and the inverse modelling showed that the dissolution of hematite, hausmannite, pyrolusite and anglesite can largely account for the mobilization of Fe, Mn and Pb in the leaching experiment. The mobility of silver may be caused by the presence of kongsbergite and chlorargyrite in the waste, while the mobility of Eu seems to be determined by Eu(OH)3, which controls the solubility of Eu in the pH–Eh conditions of the experiments. The mineralogy, pH, Eh and geochemical composition of the mine wastes may explain the possible mobilization of heavy metals and metalloids. However, the absence of contaminants in the groundwater may be caused by the carbonate-rich environment of “host-rocks” that limits their mobility.  相似文献   

16.
In a typical modern agricultural Zone of southeastern China, Haining City, 224 topsoil samples were collected from paddy fields to measure the total concentrations of copper (Cu), lead (Pb), zinc (Zn), cadmium (Cd), chromium (Cr), mercury (Hg), arsenic (As) and cobalt (Co). The total concentrations ranged from 15.30 to 78.40 mg kg−1 for Cu, 20.10 to 41.40 mg kg−1 for Pb, 54.98 to 224.4 mg kg−1 for Zn, 0.04 to 0.24 mg kg−1 for Cd, 54.90 to 197.1 mg kg−1 for Cr, 0.03 to 0.61 mg kg−1 for Hg, 3.44 to 15.28 mg kg−1 for As, and 7.17 to 19.00 mg kg−1 for Co. Chemometric techniques and geostatistics were utilized to quantify their spatial characteristics and define their possible sources. All eight metals had a moderate spatial dependency except that Pb had a strong spatial dependency. Both factor analysis and cluster analysis successfully classified the eight metals into three groups or subgroups, the first group included Cu, Zn and Cr, the second group included Cd, As and Co, and the last group included Pb and Hg. The Cu, Zn and Cr concentrations in majority samples were higher than their local background concentrations and they were highly correlated (r > 0.80), indicating that they had similar pollution source and anthropic factor controlled their spatial distribution; the Cd, As and Co concentrations in majority samples were lower than their local background concentrations, indicating that the source of these elements was mainly controlled by natural factors; the mean concentration of Pb exhibited generally low level, close to its local background concentration, the Hg concentration in about half of samples was higher than its local background concentration, and they were poor correlated with the other metals, indicating that the source of Pb and Hg was common controlled by natural factor and anthropic factor.  相似文献   

17.
An attempt was made to evaluate background concentrations of Cd, Cu, Pb and Zn by means of geochemical and statistical approach. As many as 753 samples taken from 51 profiles located in Eastern Poland were analysed. For the estimation of geochemical background values, direct geochemical methods and a statistical analysis for the whole population of samples were applied. Average values of heavy metal concentration in loess sediments (bedrock) as well as in profiles not affected by human activity were measured. The iterative 2σ technique and calculated distribution function were chosen as statistical methods. The resulting values (background concentrations range) were as follows: Cd 0.5–0.9 mg kg−1, Cu 5–16 mg kg−1, Pb 12–26 mg kg−1 and Zn 31–47 mg kg−1. All the methods applied gave similar results. The highest deviation of the background was noted for Cu and the lowest for Zn. The lowest values of background were obtained for loess sediments and the highest in the case of the multiple 2σ method.  相似文献   

18.
Mercury (Hg) is one of the elements with increasing environmental significance. A total of 22 samples (soils, rocks and gels) were collected along a 6 km transect around the Valdeazogues River valley in the southwest of the Iberian Peninsula (Almadén, Spain). Samples were characterized by different soil types of depositional sequences associated with mining tailings, type and system tracts: 15 surface soil samples included in the transect; 3 of a Haploxerept soil profile developed on slates; 2 of quartzite and slates rocks (reference rocks in the area). Moreover, two of a gel substance (in the lower tract of the river). Soil samples were analyzed for Hg, Cu, Ni, Cr, V, Pb, Cd and As, as well as for organic matter, pH abrasion and calcium carbonate content. All samples were collected from the Almadén mining district. The level of occurrence of the elements (especially Hg) and the effect of some properties on its concentration distributions were investigated. The total mercury contents varied in the range 7,315–3.44 mg kg−1. The mean concentration of total mercury in soils and rocks was 477.03 mg kg−1dry mass. This value is very high compared to the regional background value of other areas. Only rarely is it higher than 1%: in one sample (7,315 mg kg−1) it was almost eight times in comparison with the affected zones, with a high value of 1,000 mg kg−1. Significant differences between samples were found in the total content of mercury. A large percentage of the samples registered detectable levels of V, Cr, Ni, Pb, As and Cu. Cd readings were below the detectable range for all samples tested. Cr mean concentration was 216.95 mg kg−1 (minimun concentration 86, maximun 358); V mean concentration was 119.09 mg kg−1 (minimun concentration 69, maximun 1,209); As mean concentration was 51.24 mg kg−1 (minimun 13.3 and maximun 319.4); Ni mean concentration was 45.64 mg kg−1 (minimun concentration 21.2 and maximun 125.6); Cu mean concentration was 33.25 mg kg−1 (minimun concentration 19.3 and maximun 135); Pb mean concentration was 15.19 mg kg−1 (minimun 1.12 and maximun 1013). Metal distribution generally showed spatial variability ascribed to significant anthropogenic perturbation by mining tailing type. Hg showed vertical profile characterized by surface enrichment, with concentrations in the upper layer (93.7–82.2 mg kg−1 in front of 3.4 of the rock value) exceeding, in several occasions, the background value. The results obtained denote a potential toxicity of some heavy metals in some of the studied samples. Water-soluble mercury could enter the aquatic system and accumulate in sediments. Mercury and other heavy metals contamination depended on the duration and intensity of mining activities.  相似文献   

19.
Physiological responses and metal accumulation in Vallisneria spiralis L. exposed to copper and cadmium contaminated sediment were examined at different metal concentrations and the influence of humic acids on copper and cadmium accumulation was also studied. The plants of V. spiralis accumulated high amount of copper and cadmium. The maximum accumulation of 396 and 114 mg kg−1 DW copper were found in the roots and shoots, respectively, at 614 mg kg−1 DW after 21 days’ copper exposure; they were 63.8 and 48.0 mg kg−1 DW for cadmium at 88.69 mg kg−1 DW. The plants showed decrease in chlorophyll content with the increasing concentration of copper/cadmium in sediment. With addition of humic acids from 3.09 to 7.89 g kg−1 DW, both copper and cadmium accumulation in V. spiralis were significantly inhibited (p < 0.01). The cadmium concentrations of roots and shoots of plant decreased 26.4–50.3 and 14.3–33.0% under cadmium treatments, respectively; copper accumulation decreased much more with 44.0–77.0 and 35.0–62.7%, respectively. It was concluded that V. spiralis appeared to be an ideal candidate for the phytoremediation of copper and cadmium polluted sediments, and humic acids had an important role in regulating copper and cadmium bioavailability and toxicity in sediments.  相似文献   

20.
Historic Hg mining in the Cache Creek watershed in the Central California Coast Range has contributed to the downstream transport of Hg to the San Francisco Bay-Delta. Different aspects of Hg mobilization in soils, including pedogenesis, fluvial redistribution of sediment, volatilization and eolian transport were considered. The greatest soil concentrations (>30 mg Hg kg−1) in Cache Creek are associated with mineralized serpentinite, the host rock for Hg deposits. Upland soils with non-mineralized serpentine and sedimentary parent material also had elevated concentrations (0.9–3.7 mg Hg kg−1) relative to the average concentration in the region and throughout the conterminous United States (0.06 mg kg−1). Erosion of soil and destabilized rock and mobilization of tailings and calcines into surrounding streams have contributed to Hg-rich alluvial soil forming in wetlands and floodplains. The concentration of Hg in floodplain sediment shows sediment dispersion from low-order catchments (5.6–9.6 mg Hg kg−1 in Sulphur Creek; 0.5–61 mg Hg kg−1 in Davis Creek) to Cache Creek (0.1–0.4 mg Hg kg−1). These sediments, deposited onto the floodplain during high-flow storm events, yield elevated Hg concentrations (0.2–55 mg Hg kg−1) in alluvial soils in upland watersheds. Alluvial soils within the Cache Creek watershed accumulate Hg from upstream mining areas, with concentrations between 0.06 and 0.22 mg Hg kg−1 measured in soils 90 km downstream from Hg mining areas. Alluvial soils have accumulated Hg released through historic mining activities, remobilizing this Hg to streams as the soils erode.  相似文献   

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