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1.
Soil and water samples were collected from farmsteads and provincial towns across the provinces of La Pampa and San Juan in Argentina. Inductively coupled plasma mass spectrometry was used for the determination of iodine in water following addition of TMAH to 1% v/v and soils extracted with 5% TMAH. Iodine in agricultural soils was in the range of 1.3–20.9 mg/kg in La Pampa located in central Argentina and 0.1–10.5 mg/kg in San Juan located in the northwest Andean region of Argentina, compared to a worldwide mean of 2.6 mg/kg. Mean selenium concentrations for soils from both provinces were 0.3 mg/kg, compared to a worldwide mean of 0.4 mg/kg. The majority of soils were slightly alkaline at pH 6.7 to 8.8. The organic content of soils in La Pampa was 2.5–5.9% and in San Juan 0.1–2.3%, whilst, mobile water extractable soil-iodine was 1–18% for La Pampa and 2–42% for San Juan. No simple relationship observed for pH and organic content, but mobile iodine (%) was highest when organic content was low, higher for lower total iodine concentrations and generally highest at pH > 7.5. Water drawn for drinking or irrigation of a variety of crops and pasture was found to range from 52 to 395 µg/L iodine and 0.8 to 21.3 µg/L selenium in La Pampa and 16–95 µg/L iodine and 0.6 to 8.2 µg/L selenium in San Juan. The water samples were all slightly alkaline between pH 8 and 10. Water–iodine concentrations were highest at pH 7.8 to 8.8 and in groundwaters positively correlated with conductivity. Raw water entering water treatment works in La Pampa was reduced in iodine content from approximately 50 µg/L in raw water to 1 µg/L in treated drinking water, similar to levels observed in regions experiencing iodine deficiency.  相似文献   

2.
To improve the usefulness and accuracy of modeling Earth's anthrobiogeochemical metal cycles, global maps at approximately 1° × 1° are produced of the concentrations and masses of Fe, Al, Cu, and Zn contained in continental sediments and soils. The maps generated utilize inverse distance weighting (IDW) and cokriging to generate new estimates for geospatially weighted mean global concentrations for these metallic micronutrients. Sediment metal concentration maps are generated from IDW of sediment samples; global soil maps are produced via cokriging upon an underlying parent rock dataset composed of both surface bedrock and sediment samples. Derived are independent estimates for the global mean concentrations in continental sediments (Fe = 3.1 wt.%, Al = 6.1 wt.%, Cu = 45 μg/g, Zn = 86 μg/g) and soils (Fe = 2.5 wt.%, Al = 3.9 wt.%, Cu = 17 μg/g, Zn = 50 μg/g). While continental sediment concentrations for Cu are within the range of previous estimates, Zn concentrations are relatively higher, ~ 20 μg/g above previous estimates. Fe and Al are slightly depleted (~ 1 wt.%) in continental sediments relative to previous estimates, likely ascribable to sampling bias and error inherent in the comparative methodologies. Besides an estimated global mean, metal concentrations in soils are also broken down by FAO soil group. Metal masses in sediments and soils remain within 30% of previous, non-spatial estimates. These maps also illustrate the discernable spatial variability across the Earth's surface. Despite data gaps, maps of metal mass show regional patterns such as the high quantities of Al in the soils and biomass of the Amazonia and Congo regions. Concentrations of metals are relatively high in the anthrosols of China. Finally, this analysis highlights those areas for which generating and providing publically available geochemical data should be prioritized. For instance, gypsisols, lixisols, and nitisols have little to no analytical data available on metal contents. A sensitivity analysis suggests that the most poorly constrained soil metal concentrations occur in the thick, old tropical soils of central Africa and the anthrosols of eastern China.  相似文献   

3.
There is a lack of information in the literature regarding Tl exposure from naturally occurring Tl enrichment. This paper draws attention to the potential health risk posed by high concentrations of naturally occurring Tl in the environment. The inhabitants of a rural area in SW Guizhou Province, China, reside within a natural Tl accumulated environment resulting from Tl-rich sulfide mineralization, and they face ongoing severe Tl exposure. High Tl concentrations were detected in urine of the local residents. Urinary Tl concentrations are as high as 2668 μg/L, with most subjects surpassing the accepted world urinary Tl concentration at <1 μg/L for “non-exposed” humans. The urinary Tl concentrations show significant differences among three communities (n = 21, p = 0.001), but no significant difference in either sex or age groups (n = 21, p = 0.7806). However, there is a positive statistical relationship between the extent of Tl exposure from Tl concentrations in soil and crops in the immediate environment and the concentrations of Tl detected in urine. A majority of the volunteer subjects from the communities have urinary Tl concentrations above 4.5–6 μg/L, implying early adverse health effects, and some of them have over 500 μg/L urinary Tl, considered to be at/about the level of clinical intoxication. This study has been able to identify that the elevated urinary Tl concentrations are mainly attributable to Tl accumulation in locally grown vegetables, which acquire Tl from the soil. This study also shows that Tl in urine of the local population represents a steady-state condition with long-term exposure, and that urinary Tl concentrations can be taken as a bio-marker of total dose based upon total daily dietary intake. This study demonstrates that natural sources of elevated Tl pose a potential health risk to the population, and that monitoring the urinary Tl concentration is a reliable and accurate way of bio-marking Tl exposure.  相似文献   

4.
Lake Constance is one of Europe’s largest oligotrophic lakes and provides a water source for more than 4.5 million people in Germany and Switzerland. We present here a 12 month study on iodine concentrations, speciation and fluxes to and from the lake to gain a quantitative understanding of the limnic iodine cycle. Monthly water samples were obtained from all major tributaries (14) and the outflow to construct a mass-balance model. Sediment traps were also deployed in the lake for two years at two different stations. Total soluble iodine (TSI) in aqueous samples were analysed by ICP-MS and speciation (iodide, iodate and soluble organically bound iodine, SOI) by ion chromatography-ICP-MS. Iodine concentrations in the Alpine tributaries (1-2 μg l−1) decreased over the summer months due to increasing proportions of snow and glacial melt water from the Alps, while iodine levels in the lowland rivers (∼2-10 μg l−1) increased over the summer. Deposition of TSI to the catchment (16,340 kg I yr−1) was similar to the TSI out-flux by rivers (16,000 kg I yr−1). By also including the particulate riverine iodine flux out of the catchment (∼12,350 kg I yr−1) it is shown that the catchment is a net source of iodine, with the highest particulate fluxes coming from the Alpine rivers. The total TSI flux to the lake was 16,770 kg I yr−1, the largest proportion coming from the Alpenrhein (43%), followed by the Schussen (8%) and Bregenzer Ach (7.7%). Overall the mass-balance for TSI in the lake was negative, with more iodine flowing out of the lake than in (−2050 kg I yr−1; 12% of TSI in-flux). To maintain mass-balance, 8.8 μg I m−2 d−1 from the Obersee and 23 μg I m−2 d−1 from the Untersee must be released from the sediments into the water column. Thus, in comparison with the total iodine flux to the sediments measured by the sediment traps (4762-8075 kg I yr−1), up to 39% of the deposited iodine may be mobilised back into the lake. SOI was the dominant iodine fraction entering the lake, with a total flux of 10,290 kg I yr−1 (64% of TSI input), followed by iodate (3120 kg I yr−1) and iodide (2760 kg I yr−1). Net formation of SOI from iodide and iodate was also noted within the lake, with an estimated production of 6560 kg I yr−1, suggesting a strong role for biology in iodine cycling. In conclusion, organically bound iodine was the dominant iodine species in aqueous and solid phases in Lake Constance, despite low DOC concentrations (<2 mg l−1), and thus is expected to play an important role in iodine cycling in most freshwater environments.  相似文献   

5.
离子色谱法测定碘在地甲病环境地质调研中的应用   总被引：2，自引：0，他引：2  
钟展环  方容 《岩矿测试》1997,16(2):145-149
收集了安徽省某地区地甲病流行患者的血、尿、发样，病区的饮水样、谷物、蔬菜样和环境地质样共计６９９个，同时收集了该地非病区水样和环境地质样２８２个。水样直接进样，其它样品经湿法分解后，用离子色谱法测定其中的碘和溴的含量。统计分析表明，病区地甲病患病率与饮水中碘的含量密切相关，也与环境地质如地貌、地质构造及水文地球化学等条件密切相关。碘含量低的石灰岩地区，地甲病患病率高。  相似文献   

6.
The distribution of Cu, Co, As and Fe was studied downstream from mines and deposits in the Idaho Cobalt Belt (ICB), the largest Co resource in the USA. To evaluate potential contamination in ecosystems in the ICB, mine waste, stream sediment, soil, and water were collected and analyzed for Cu, Co, As and Fe in this area. Concentrations of Cu in mine waste and stream sediment collected proximal to mines in the ICB ranged from 390 to 19,000 μg/g, exceeding the USEPA target clean-up level and the probable effect concentration (PEC) for Cu of 149 μg/g in sediment; PEC is the concentration above which harmful effects are likely in sediment dwelling organisms. In addition concentrations of Cu in mine runoff and stream water collected proximal to mines were highly elevated in the ICB and exceeded the USEPA chronic criterion for aquatic organisms of 6.3 μg/L (at a water hardness of 50 mg/L) and an LC50 concentration for rainbow trout of 14 μg/L for Cu in water. Concentrations of Co in mine waste and stream sediment collected proximal to mines varied from 14 to 7400 μg/g and were highly elevated above regional background concentrations, and generally exceeded the USEPA target clean-up level of 80 μg/g for Co in sediment. Concentrations of Co in water were as high as in 75,000 μg/L in the ICB, exceeding an LC50 of 346 μg/L for rainbow trout for Co in water by as much as two orders of magnitude, likely indicating an adverse effect on trout. Mine waste and stream sediment collected in the ICB also contained highly elevated As concentrations that varied from 26 to 17,000 μg/g, most of which exceeded the PEC of 33 μg/g and the USEPA target clean-up level of 35 μg/g for As in sediment. Conversely, most water samples had As concentrations that were below the 150 μg/L chronic criterion for protection of aquatic organisms and the USEPA target clean-up level of 14 μg/L. There is abundant Fe oxide in streams in the ICB and several samples of mine runoff and stream water exceeded the chronic criterion for protection of aquatic organisms of 1000 μg/L for Fe. There has been extensive remediation of mined areas in the ICB, but because some mine waste remaining in the area contains highly elevated Cu, Co, As and Fe, inhalation or ingestion of mine waste particulates may lead to human exposure to these elements.  相似文献   

7.
The solubility and partitioning of Pt in a S-free vapor - brine - rhyolite melt - Pt metal assemblage has been quantified at 800 °C, fO2=NNO and pressures of 100 and 140 MPa. Vapor and brine were sampled at run conditions by trapping these phases as glass-hosted fluid inclusions as the melt cooled through the glass transition temperature. The vapor and brine were in equilibrium with the melt at the time of trapping and, thus, represent fluids which were sampled at the termination of each experimental run. The microthermometrically determined salinities of vapor and brine are ∼2 and ∼63 wt.% NaCl eq. and ∼9 and ∼43 wt.% NaCl eq. at 100 and 140 MPa, respectively. Platinum solubilities in vapor, brine and glass (i.e., quenched melt) were quantified by using laser ablation - inductively coupled plasma - mass spectrometry (LA-ICP-MS). Equilibrium is discussed with reference to the major and trace element concentrations of glass-hosted fluid inclusions as well as the silicate melt over run times that varied from 110 to 377 h at 140 MPa and 159 to 564 h at 100 MPa. Platinum solubility values (±1σ) in H2O-saturated felsic melt are 0.28 ± 0.13 μg/g and 0.38 ± 0.06 μg/g at 140 and 100 MPa, respectively. Platinum solubility values () at 140 and 100 MPa, respectively, in aqueous vapor are 0.91 ± 0.29 μg/g and 0.37 ± 0.17 μg/g and in are brine 16 ± 10 μg/g and 3.3 ± 1.0 μg/g. The measured solubility data were used to calculate Nernst-type partition coefficients for Pt between vapor/melt, brine/melt and vapor/brine. The partition coefficient values () for vapor/melt, brine/melt and vapor/brine at 140 MPa are 2.9 ± 1.0, 67 ± 27, and 0.13 ± 0.05 and at 100 MPa are 1.0 ± 0.2, 6.8 ± 2.4, and 0.15 ± 0.05. The partitioning data were used to model the Pt-scavenging capacity of vapor and brine during the crystallization-driven degassing (i.e., second boiling) of a felsic silicate melt over a depth range (i.e., 3-6 km) consistent with the evolution of magmatic-hydrothermal ore deposits. Model calculations suggest that aqueous vapor and brine can scavenge sufficient quantities of Pt, and by analogy other platinum group elements (PGE), to produce economically important PGE-rich magmatic-hydrothermal ore deposits in Earth’s upper continental crust.  相似文献   

8.
Very limited research has been conducted on selenium (Se) in Lebanese soils and forage crops but no work has been done on Se in water and locally produced vegetables and grains. This research was conducted in order to quantify Se levels and its availability in agricultural soils, vegetables and grains in Lebanon. Sixty-six (66) soil samples were collected from 33 selected sites in Lebanon: the Bekaa Valley, coastal and mountainous regions. Thirteen (13) different plant types (86 samples) were sampled from the same locations. Also, 13 spring water and 10 bottled water samples were collected. Soil samples were analyzed for their physical and chemical properties. Selenium was extracted from soils with: deionized–distilled water (Soluble-Se), KH2PO4-0.1 M (MKP-Se) and concentrated (HNO3 + HCl) mixture (acid-Se). Plant Se was extracted by acid digestion on a hotplate. Selenium concentrations were measured by the inductively coupled plasma-mass spectrophotometer (ICP-MS). The values of Soluble-Se, MKP-Se and acid-Se ranged between 47 and 142, 147 and 400, and 1749 and 4713 μg/kg, respectively, with average values of 95, 306, and 3118 μg/kg and at a ratio of 1:3:30. Thus, Se extracted with deionized–distilled water is a good indicator for Se availability in the studied soils. The average Se concentration in plants was in the following order: radish > lettuce > cucumber > cabbage > parsley > alfalfa > onion (leaves) > broccoli > tomato > mint > chickpeas > wheat > onion (bulbs). The Se levels in water samples were in the safe range (less than 50 μg/L) and ranged between 2.14 and 17.6 μg/L. The levels of Se in the three soil extractants were positively correlated with each other and with organic matter content, salinity and phosphorus (P). Selenium levels in plant samples were positively correlated at a 0.01 significance level with clay and P content.  相似文献   

9.
Iodine is one of the most problematic radioisotopes in the context of nuclear waste geological disposal due to its high mobility. Considerable effort has been dedicated to the measurement of its potential retardation during diffusive transport leading to conflicting results, from no retardation to significant retardation, leading in turn to considerable debate. The present study aims at providing new insights into this aspect of the iodine problem by careful quantification of iodine reservoirs in the Callovian-Oxfordian (COx) clay rock taken here as model material for these studies. The present study confirmed the ubiquitous presence of iodine at 1-5 mg kg−1 level in the COx clayey formation. The iodide concentration level in the porewater is also confirmed at a value in the range ∼20-40 μmol L−1, i.e. higher than the expected range of radio-iodine concentration in the far-field of the storage. Surprisingly, most of the iodine was found not to be associated with organic matter but rather in an inorganic form associated with carbonate minerals. This result has potentially significant implications for the fate of radio-iodine. In undisturbed far-field conditions, most natural iodine would not be accessible for isotopic exchange with radioactive iodine, reducing the effective Kd to negligible values. During laboratory experiments, good monitoring of the geochemical parameters (at least the Eh, pH, PCO2, [Ca] and [Mg]) is mandatory to avoid iodine-bearing carbonate precipitation and to enable rigorous interpretation of the iodide diffusion/retention experiments.  相似文献   

10.
Indigofera melanadenia and Tephrosia longipes plant species, collected from Cu–Ni mining area, were evaluated for accumulation of Cu and Ni. The total and bioavailable concentrations of Cu and Ni in the host soils were also determined. Flame Atomic Absorption Spectrometry was used for all metal determinations. The total and bioavailable concentrations of Cu in the soils were in the range 900–9000 μg/g and 200–2000 μg/g respectively. For Ni, the total and bioavailable concentrations were in the range 900–2000 μg/g and ∼ 40–100 μg/g respectively. The concentrations of Cu and Ni in the leaves of I. melanadenia were higher than in the roots with a range 80–130 μg/g in the leaves and 20–80 μg/g in the roots for Cu and a range of 150–200 μg/g in the leaves and 20–60 μg/g in the roots for Ni. Concentration of Cu in T. longipes was in the range of 37–240 μg/g and 150–200 μg/g in the leaves and roots respectively while the concentration of Ni was 80–140 μg/g in the leaves and 25–100 μg/g in the roots. Results indicate that both species have a potential for accumulating Cu and Ni. Translocation factor, a ratio of shoots to roots metal concentration, was used to evaluate the translocation properties of the plants from roots to shoots. Translocation factors of the plants were ≥ 1 suggesting efficient translocation of metals from roots to shoots.  相似文献   

11.
The fate of potentially harmful metals (PHM) after their entry into an unpolluted fresh water body depends on the physicochemical and biological parameters of the aquatic ecosystem. This paper considers the effect of pH and suspended particles (SP) on the behavior of Cu, Zn and Cd when they enter a fresh water reservoir. In a field experiment, four mesocosms were constructed in the Novosibirskoye Reservoir to allow systematic variation of SP concentration (15 or 250 mg/L) and pH (8.5 or 6.5). The initial concentrations of Cu, Zn and Cd in the mesocosms were 1000, 1000 and 200 μg/L, respectively. Natural bottom sediments were used to provide additional mineral SP, and water hyacinth was used as a floating plant species. Over 11 days, measurements were made of several indicators: residual metal concentration in solution ([PHM]w); metal concentration in SP ([PHM]s); primary productivity of the phytoplankton community; mass of settled SP; PHM concentration in settled SP; and PHM bioaccumulation by water hyacinth. The ratio [PHM]w/[PHM]s in the water varied in the order Cu < Zn < Cd and was higher at pH 6.5 than at pH 8.5. This observation reflects different PHM sorption (Cu > Zn > Cd) onto mineral SP and PHM biosorption by planktonic organisms. Phytoplankton acts as a renewable source of organic SP and plays an important role in metal removal from the water in the mesocosms. After 11 days the residual concentrations of Cu, Zn and Cd in the mesocosm without SP addition (initial SP concentration was 15 mg/L) were 272, 355 and 84 μg/L, respectively. The residual concentrations of Cu, Zn and Cd in mesocosms with SP addition were 57, 100 and 14 μg/L at pH 8.5 and 80, 172 and 20 μg/L at pH 6.5, respectively. Therefore, addition of SP resulted in faster and more complete removal of metals into the bottom sediments. Floating plants (water hyacinth) accumulated PHM (Cu > Zn > Cd) more effectively at pH 8.5 than at pH 6.5, and PHM concentrations in the roots were higher than in settling SP. The general trends of PHM removal from contaminated water via sedimentation and bioaccumulation are compared with changes of metal speciation in solution.  相似文献   

12.
Zinc smelting is currently regarded as one of the most important atmospheric Hg emission sources in the world. In order to assess the potential environmental impacts of Hg from Zn smelting in China, the distribution of total Hg concentration (HgT) in Zn concentrates (ZCs) from 100 Zn deposits in China was investigated. It was found that HgT varies depending on the ore types and their geneses. Zinc concentrates from sedimentary-exhalative deposits (SEDEX, geometric mean = 48.2 μg/g) have the highest HgT. The possible explanation is that the sources of mineralizing solutions for SEDEX deposits are deep formational brines in contact with sedimentary rocks, and there are much higher background Hg contents in sedimentary rocks. Zinc concentrates from volcanic hosted massive sulfide deposits (VMS, geometric mean = 11.5 μg/g) and Mississippi Valley-Type (MVT, geometric mean = 10.1 μg/g) deposits have intermediate HgT. VMS may receive most of their Hg from fluid–rock interaction and/or by direct input of gaseous Hg from a mantle source. However, the source of metals within MVTs may be the low-temperature hydrothermal solution formed by diagenetic recrystallization of the carbonates. Intrusion related deposits (IRs) have the lowest HgT (Geomean = 2.4 μg/g), and the dispersion of Hg in the IRs seems to be influenced by the temperature of ore formation and/or the nature of wall–rock alteration. Finally, it was estimated that the annual Hg emission to the atmosphere from Zn smelting in China was about 107.7 tons in 2006.  相似文献   

13.
This study focused on the analysis of As levels in human hair samples collected from six villages in the Kandal Province of Cambodia. Of interest were the influence of, and interactions among, certain factors affecting As intake into the human body: As concentrations in groundwater, period of groundwater consumption, age and gender. The results revealed As levels in human hair ranging from 0.06 to 30 μg g−1 with median and arithmetic mean values of 0.61 and 3.20 μg g−1 (n = 68), respectively. Furthermore, a linear relationship was found between As concentrations in human hair and in the local groundwater. Arsenic (III) is the dominant species in Kandal groundwater, constituting in most cases at least 60% of the total As. Arsenic concentration ranged from 5 to 1543 μg L−1, with the median value 348 μg L−1 and arithmetic mean 454 μg L−1. In large rural, poor areas holding most of Kandal’s 1.1 million people, up to 2 in 1000 people are believed to be at risk of cancer through the As-enriched water they drink. A toxicity risk assessment provides a hazard quotient (HQ) equaling 5.12, also a clear indication of non-carcinogenic exposure risk. On the authors’ visit to Kampong Kong commune, Kandal Province, cases of arsenicosis were diagnosed in patients as a result of drinking As-enriched groundwater.  相似文献   

14.
Batch and column experiments were conducted to examine the capability of naturally formed hematite and siderite to remove As from drinking water. Results show that both minerals were able to remove As from aqueous solutions, but with different efficiencies. In general, each material removed arsenate much more efficiently than As–DMA (dimethylarsinic acid), with the lowest adsorption efficiency for arsenite. The best removal efficiency for As species was obtained using a hematite, with a grain size range between 0.25 and 0.50 mm. The adsorption capacity for inorganic As(V) reached 202 μg/g. The pH generally had a great impact on the arsenate removal by the Fe minerals studied, while arsenite removal was slightly dependent on the initial pH of between 3 and 10. The presence of phosphate always had a negative effect on arsenate adsorption, due to competitive adsorption between them. A column packed with hematite in the upper half and siderite in the lower half with a grain size range of 0.25–0.5 mm proved to be an efficient reactive filter for the removal of all As species, causing a decrease in As concentration from 500 μg/L (including 200 μg/L As(V) as arsenate, 200 μg/L As(III) as arsenite and 100 μg/L As(V) as DMA) to less than 10 μg/L after 1055 pore volumes of water were filtered at a flow rate of 0.51 mL/min. After 2340 pore volumes passed through the column filter, the total inorganic As in the effluent was less than 5 μg/L. The total As load in the column filter was estimated to be 0.164 mg/g. Results of μ-synchrotron X-ray fluorescence analysis (μ-XRFA) suggest that coatings of fresh Fe(III) oxides, formed on the surface of the siderite grains after two weeks of operation, greatly increased the adsorption capacity of the filling material towards As.  相似文献   

15.
The fractionation of P in Pandoh Lake surface sediments has been investigated for the first time in order to understand its environmental availability and sources, and the eutrophication status of this lake. Inorganic-P is present mainly as authigenic-P (step-III). The authigenic P concentration is higher in winter relative to the summer and monsoon seasons and ranged from 35.9 to 46.9 μg/g. The loosely sorbed or exchangeable-P (step-I), Fe(III)-bound-P (step-II) and detrital inorganic-P (step-IV) were higher in the monsoon season and varied from 3.70 to 11.1 μg/g, 16.9 to 32.0 μg/g and 9.89 to 17.0 μg/g, respectively. Organic-P reached a maximum in the summer season and ranged from 8.00 to 14.9 μg/g. Authigenic-P and detrital inorganic-P show seasonal changes, as pH influences the interaction between P and CaCO3 in the water column. In the winter season, phosphate is precipitated out of the water column and fixed in the sediments as a result of an increase in pH. Calcite-bound-P in the sediments may be redissolved by decreasing pH in the summer season. Relatively high rates of mineralization during the monsoon results in the seasonal pattern of organic-P fractionation to sediment as follows: monsoon = winter < summer. Iron, Ca, organic matter and silt and clay contents seem to play a significant role in regulating the seasonal P budget. Principal component analysis (PCA) was used to identify the factors which influence sedimentary P in the different seasons.  相似文献   

16.
We report experimentally determined 1 atm olivine/melt DNa partitioning data for low fO2, a variety of melt compositions and a temperature range of 1325-1522 °C. We demonstrated that high-current electron microprobe analyses (EPMA, I = 500 nA, 600 s on the peak) allow quantitative determination of Na2O in olivine down to ∼10 μg/g. The mean olivine/melt DNa from 12 experimental runs is 0.0031 ± 0.0007 (1σ). This is the recommended value for low pressures and a wide range of natural compositions.This result is applied to the problem of the origin of alkalis in chondrules and the formation of chondritic refractory forsterite grains. The data on Semarkona (LL3.0) chondrules show that Na2O is primordial and was present during olivine crystallization. For refractory forsterite grains from Murchison (CM2), we demonstrate that high CaO contents are not a result of equilibration with Na2O-rich melts, but require high activities of CaO during their formation.  相似文献   

17.
Fifty soil samples collected from agricultural land in four regions of Poland with different anthropopressure were analysed for their content of 16PAHs by GC/MS. The regions correspond to Polish administrative units (voievodeships): Podlaskie and Lubelskie are situated in the rural East part of the country and more industrialised Slaskie and Dolnoslaskie voievodeships – in the South-West part. Basic physicochemical properties as well as the content of selected potentially harmful metals (Pb and Zn) were included in the soil analysis. Overall accumulation of Σ16PAHs in the upper soil layer was within the range 73–1800 μg kg−1 with a geometric mean (GM) of 252 μg kg−1, while the mean benzo(a)pyrene (BaP) load was 20 μg kg−1. This corresponds with data for other European countries. Carcinogenic compounds contributed nearly in 50% to the total PAHs loads. In uncontaminated rural regions the mean Σ16PAHs and BaP contents were 113–159 μg kg−1 and 11–13 μg kg−1, respectively. Regional conditions strongly influenced the accumulation of PAHs ?4-rings, which were highly dependent (over 95%) on local anthropopressure expressed as dust and 4PAHs emission indexes. Soil acidity was the main soil parameter related to the accumulation of higher molecular weight PAHs in soils. In more contaminated regions a significant link between soil OM and PAH loads was noted. The same regions were characterised by associations between PAHs and potentially harmful metals implying common sources of pollution. Those relationships were not observed in the uncontaminated part of the country. The lower molecular weight PAHs contributed to a smaller extent (about 20%) to the total PAHs content in soils, and were less affected by anthropogenic factors.  相似文献   

18.
Environmental contamination with As and Sb caused by past mining activities at Sb mines is a significant problem in Slovakia. This study is focused on the environmental effects of the 5 abandoned Sb mines on water, stream sediment and soil since the mines are situated in the close vicinity of residential areas. Samples of mine wastes, various types of waters, stream sediments, soils, and leachates of the mine wastes, stream sediments and selected soils were analyzed for As and Sb to evaluate their geochemical dispersion from the mines. Mine wastes collected at the mine sites contained up to 5166 mg/kg As and 9861 mg/kg Sb. Arsenic in mine wastes was associated mostly with Fe oxides, whereas Sb was present frequently in the form of individual Sb, Sb(Fe) and Fe(Sb) oxides. Waters of different types such as groundwater, surface waters and mine waters, all contained elevated concentrations of As and Sb, reaching up to 2150 μg/L As and 9300 μg/L Sb, and had circum-neutral pH values because of the buffering capacity of abundant Ca- and Mg-carbonates. The concentrations of Sb in several household wells are a cause for concern, exceeding the Sb drinking water limit of 5 μg/L by as much as 25 times. Some attenuation of the As and Sb concentrations in mine and impoundment waters was expected because of the deposition of metalloids onto hydrous ferric oxides built up below adit entrances and impoundment discharges. These HFOs contained >20 wt.% As and 1.5 wt.% Sb. Stream sediments and soils have also been contaminated by As and Sb with the peak concentrations generally found near open adits and mine wastes. In addition to the discharged waters from open adits, the significant source of As and Sb contamination are waste-rock dumps and tailings impoundments. Leachates from mine wastes contained as much as 8400 μg/L As and 4060 μg/L Sb, suggesting that the mine wastes would have a great potential to contaminate the downstream environment. Moreover, the results of water leaching tests showed that Sb was released from the solids more efficiently than As under oxidizing conditions. This might partly explain the predominance of Sb over As in most water samples.  相似文献   

19.
The magnitude and sources of lead (Pb) pollution in the Gulf of California Ecoregion (GCE) in northwest Mexico were evaluated using various samples collected from urban and rural areas around two typical subtropical coastal ecosystems. Lead concentrations and isotopic compositions (206Pb/207Pb, 208Pb/207Pb, 206Pb/204Pb and 208Pb/204Pb) were measured using high resolution inductively-coupled plasma mass spectrometry (HR-ICP-MS) and thermal ionization mass spectrometry (TIMS). Urban street dust (157 ± 10.1 μg g− 1) was heavily enriched with Pb, compared to the Pb enrichment of agricultural soils (29.0 ± 16.0 μg g− 1) and surface estuary sediments (35.6 ± 15.4 μg g− 1), all of which contained higher Pb concentrations than found in the natural bedrock (16.0 ± 5.0 μg g− 1). Pb concentrations in SPM (> 95% of total Pb) were significantly higher in sewage effluent (132 ± 49.9 μg g− 1) than in agricultural effluents (29.3 ± 5.9 μg g− 1), and river runoff (7.3 ± 4.2 μg g− 1). SPM in estuary water column averaged 68.3 ± 48.0 μg g−1. The isotopic composition of Pb (206Pb/207Pb, 208Pb/207Pb) in rural samples of aerosols (1.181 ± 0.001, 2.444 ± 0.003) and soil runoff (1.181 ± 0.003, 2.441 ± 0.004) was comparable to that of natural Pb-bearing bedrock (1.188 ± 0.005, 2.455 ± 0.008); while urban samples of aerosols, street dust, and sewage (1.190–1.207, 2.452–2.467) showed a significant contribution from automotive emissions from past leaded gasoline combustion (1.201 ± 0.006, 2.475 ± 0.005). The absence of lead from fertilizer (1.387 ± 0.008, 2.892 ± 0.005) suggests that this mixture is not representative of the GCE. A mixing model revealed that the Pb content in the environmental samples is predominantly derived from natural weathering and the past leaded gasoline combustion with the later influence of inputs from a more radiogenic source related with anthropogenic lead of North American origin (1.21 ± 0.02; 2.455 ± 0.02).  相似文献   

20.
Smelting slags associated with base-metal vein deposits of the Sierra Almagrera area (SE Spain) show high concentrations of Ag (<5–180 ppm), As (12–750 ppm), Cu (45–183 ppm), Fe (3.2–29.8%), Pb (511–2150 ppm), Sb (22–620 ppm) and Zn (639–8600 ppm). The slags are mainly composed of quartz, fayalite, barite, melilite, celsian, pyrrhotite, magnetite, galena and Zn–Pb–Fe alloys. No glassy phases were detected. The following weathering-related secondary phases were found: jarosite–natrojarosite, cotunnite, cerussite, goethite, ferrihydrite, chalcanthite, copiapite, goslarite, halotrichite and szomolnokite. The weathering of slag dumps near the Mediterranean shoreline has contaminated the soils and groundwater, which has caused concentrations in groundwater to increase to 0.64 mg/L Cu, 40 mg/L Fe, 0.6 mg/L Mn, 7.6 mg/L Zn, 5.1 mg/L Pb and 19 μg/L As. The results of laboratory leach tests showed major solubilization of Al (0.89–12.6 mg/L), Cu (>2.0 mg/L), Fe (0.22–9.8 mg/L), Mn (0.85–40.2 mg/L), Ni (0.092–2.7 mg/L), Pb (>2.0 mg/L) and Zn (>2.5 mg/L), and mobilization of Ag (0.2–31 μg/L), As (5.2–31 μg/L), Cd (1.3–36.8 μg/L) and Hg (0.2–7 μg/L). The leachates were modeled using the numerical code PHREEQC. The results suggested the dissolution of fayalite, ferrihydrite, jarosite, pyrrhotite, goethite, anglesite, goslarite, chalcanthite and cotunnite. The presence of secondary phases in the slag dumps and contaminated soils may indicate the mobilization of metals and metalloids, and help to explain the sources of groundwater contamination.  相似文献   

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