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1.
This research investigates the adsorption mechanisms of fluoride (F) on four clay minerals (kaolinite, montmorillonite, chlorite, and illite) under different F ? concentrations and reaction times by probing their fluoride superficial layer binding energies and element compositions using X-ray photoelectron spectroscopy (XPS). At high F ? concentrations ( C 0 = 5?C1000 mg·L ?1), the amount of F ? adsorbed ( Q F), amount of hydroxide released by clay minerals, solution F ? concentration, and the pH increase with increasing C 0. The increases are remarkable at C 0>50 mg·L ?1. The QF increases significantly by continuously modifying the pH level. At C 0<5?C100 mg·L ?1, clay minerals adsorb H + to protonate aluminum-bound surface-active hydroxyl sites in the superficial layers and induce F ? binding. As the C 0 increases, F ?, along with other cations, is adsorbed to form a quasi-cryolite structure. At C 0>100 mg·L ?1, new minerals precipitate and the product depends on the critical Al 3+ concentration. At [Al 3+]>10 ?11.94 mol·L ?1, cryolite forms, while at [Al 3+]<10 ?11.94 mol·L ?1, AlF 3 is formed. At low C 0 (0.3?C1.5 mg·L ?1), proton transfer occurs, and the F ? adsorption capabilities of the clay minerals increase with time. 相似文献
2.
The effect of a tea plantation on soil basic properties, chemical and mineralogical compositions, and magnetic properties
of Alfisols from eastern China was studied. Under the tea plantation, acidification took place within a soil depth of 70 cm,
with the maximum difference in pH in the upper 17 cm (ΔpH = 2.80). Both the tea plantation and unused soil profiles were predominated
by free Fe and Al oxides, i.e. citrate/bicarbonate/dithionite extractable Fe (Fe d) and Al (Al d). Tea plantation soil was characterized by higher Al d and Fe d and lower Fe oxalate, Fe 2O 3 and Al 2O 3; CaO was depleted, whereas SiO 2 accumulated. Acidification induced by the tea plantation led to destruction of vermiculite followed by dissolution of the
hydroxy-Al interlayers within its structure. The data clearly demonstrated that significant soil weathering occurred with
acidification caused by tea cultivation. This acidification also resulted in decreased content of ferrimagnetic minerals due
to the dissolution of minerals and movement of Fe in the profile. 相似文献
3.
An area with extremely high incidence of urinary calculi was investigated in the view of identifying the relationship between the disease prevalence and the drinking water geochemistry. The prevalence of the kidney stone disease in the selected Padiyapelella–Hanguranketa area in Central Highlands of Sri Lanka is significantly higher compared with neighboring regions. Drinking water samples were collected from water sources that used by clinically identified kidney stone patients and healthy people. A total of 83 samples were collected and analyzed for major anions and cations. The anions in the area varied in the order HCO 3 ? > Cl ? > SO 4 2? > NO 3 ? and cations varied in the order Ca 2+ > Mg 2+ > Na + > K + > Fe 2+. The dissolved silica that occurs as silicic acid (H 4SiO 4) in natural waters varied from 8.8 to 84 mg/L in prevalence samples, while it was between 9.7 and 65 mg/L for samples from non-prevalence locations. Hydrogeochemical data obtained from the two groups were compared using the Wilcoxon rank-sum test. It showed that pH, total hardness, Na +, Ca 2+ and Fe 2+ had significant difference ( p < 0.005) between water sources used by patients and non-patients. Elemental ratio plots, Gibbs’ plot and factor analysis indicated that the chemical composition of water sources in this area is strongly influenced by rock–water interactions, particularly the weathering of carbonate and silicate minerals. This study reveals a kind of association between stone formation and drinking water geochemistry as evident by the high hardness/calcium contents in spring water used by patients. 相似文献
4.
The mineralogical and chemical characteristics of As solid phases in arsenic-rich mine tailings from the Nakdong As–Bi mine
in Korea was investigated. The tailings generated from the ore roasting process contained 4.36% of As whereas the concentration
was up to 20.2% in some tailings from the cyanidation process for the Au extraction. Thin indurated layers and other secondary
precipitates had formed at the surfaces of the tailings piles and the As contents of the hardened layers varied from 2.87
to 16.0%. Scorodite and iron arsenate (Fe 3AsO 7) were the primary As-bearing crystalline minerals. Others such as arsenolamprite, bernardite and titanium oxide arsenate
were also found. The amorphous As–Fe phases often showed framboidal aggregates and gel type textures with desiccation cracks.
Sequential extraction results also showed that 55.7–91.1% of the As in tailings were NH 4-oxalate extractable As, further confirmed the predominance of amorphous As–Fe solid phases. When the tailings were equilibrated
with de-ionized water, the solution exhibited extremely acidic conditions (pH 2.01–3.10) and high concentrations of dissolved
As (up to 29.5 mg L −1), indicating high potentials for As to be released during rainfall events. The downstream water was affected by drainage
from tailings and contained 12.7–522 μg L −1 of As. The amorphous As–Fe phases in tailings have not entirely been stabilized through the long term natural weathering
processes. To remediate the environmental harms they had caused, anthropogenic interventions to stabilize or immobilize As
in the tailings pile should be explored. 相似文献
5.
Amino acids, proteins, and peptides are found ubiquitously in waters. They can form harmful byproducts during water treatment by reaction with disinfectants. Chlorination and chloramination of water containing natural organic matter is known to result in the production of toxic substances, often referred to as disinfection byproducts. The main advantage of using chlorine dioxide (ClO 2) over other known chlorine-containing disinfectants is the minimization of the formation of harmful trihalomethanes. Because ClO 2 is a promising alternative to other chlorine-containing disinfectants, the chemistry of ClO 2 interactions with amino acids, proteins, and peptides should be understood to ensure the safety of potable water supplies. Here, we present an overview of the aqueous chemistry of ClO 2 and its reactivity with amino acids, peptides, and proteins. The kinetics and products of the reactions are reviewed. Only a few amino acids have been reported to be reactive with ClO 2, and they have been found to follow second-order kinetics for the overall reaction. The rate constants vary from 10 ?2 to 10 7?M ?1?s ?1 and follow an order of reactivity: cysteine?>?tyrosine?>?tryptophan?>?histidine?>?proline. For reactions of histidine, tryptophan, and tyrosine with ClO 2, products vary depending largely on the molar ratios of ClO 2 with the specific amino acid. Products of ClO 2 oxidation differ with the presence or absence of oxygen in the reaction mixture. Excess molar amounts of ClO 2 relative to amino acids are associated with the production of low molecular weight compounds. The oxidation of the biochemically important compounds bovine serum albumin and glucose-6-phosphate dehydrogenase by ClO 2 suggests a denaturing of proteins by ClO 2 by an attack on tryptophan and tyrosine residues and relates to the inactivation of microbes by ClO 2. 相似文献
6.
Quality of groundwater in the Yarmouk basin, Jordan has been assessed through the study of hydrogeochemical characteristics and the water chemistry as it is considered the main source for drinking and agriculture activities in the region. The results of the relationship between Ca 2+ + Mg 2+ versus HCO 3? + CO 32?, Ca 2+ + Mg 2+ versus total cations, Na + + K + versus total cations, Cl ? + SO 42? versus Na + + K +, Na + versus Cl ?, Na + versus HCO 3? + CO 32?, Na + versus Ca 2+, and Na +: Cl ? versus EC describe the mineral dissolution mechanism through the strong relationship between water with rocks in alkaline conditions with the release of Ca 2+, Mg 2+, Na +, K +, HCO 3?, CO 32?, SO 42?, and F ? ions in the groundwater for enrichment. Furthermore, evaporation processes, groundwater depletion, and ion exchange contribute to the increased concentration of Na + and Cl ? ions in groundwater. Anthropogenic sources are one of the main reasons for contamination of groundwater in the study area and for increasing the concentration of Mg 2+, Na +, Cl ?, SO 42?, and NO 3? ions. Results show the quality of groundwater in the study area is categorized as follows: HCO 3? + CO 32? > Cl ? > SO 42? > NO 3? > F ? and Na + > Ca 2+ > Mg 2+ > K +. In conclusion, the results of TDS, TH, and chemical composition showed that 26% of the groundwater samples were unsuitable for drinking. About 28% of groundwater samples in the study area have a high concentration of Mg 2+, Na +, and NO 3? above the acceptable limit. Also, based on high SAR, 10% of the groundwater samples were not suitable for irrigation purposes. 相似文献
7.
The objectives of this study were to elucidate the effects of soil amendments [Ferrous sulfate (Fe II), red mud, Fe II with calcium carbonate (Fe II/L) or red mud (RM/F), zero-valent iron (ZVI), furnace slag, spent mushroom waste and by-product fertilizer] on arsenic (As)
stabilization and to establish relationships between soil properties, As fractions and soil enzyme activities in amended As-rich
gold mine tailings (Kangwon and Keumkey). Following the application of amendments, a sequential extraction test and evaluation
of the soil enzyme activities (dehydrogenase and β-glucosidase) were conducted. Weak and negative relationships were observed between water-soluble As fractions (As WS) and oxalate extractable iron, while As WS was mainly affected by dissolved organic carbon in alkaline tailings sample (Kangwon) and by soil pH in acidic tailings sample
(Keumkey). The soil enzyme activities in both tailings were mainly associated with As WS. Principal component and multiple regression analyses confirmed that As WS was the most important factor to soil enzyme activities. However, with some of the treatments in Keumkey, contrary results
were observed due to increased water-soluble heavy metals and carbon sources. In conclusion, our results suggest that to simultaneously
achieve decreased As WS and increased soil enzyme activities, Kangwon tailings should be amended with Fe II, Fe II/L or ZVI, while only ZVI or RM/F would be suitable for Keumkey tailings. Despite the limitations of specific soil samples,
this result can be expected to provide useful information on developing a successful remediation strategy of As-contaminated
soils. 相似文献
8.
The distribution and mobility of heavy metals in the paddy soils surrounding a copper smelting plant in south China was investigated. We assessed the degree of metal contamination using an index of geoaccumulation. The metals were divided into two groups: (1) Cu, Zn, Pb and Cd, whose concentrations were heavily affected by anthropogenic inputs, and (2) Ni, Co and Cr, which were mainly of geochemical origin. Concentrations of Cu, Cd, Zn, and Pb in the polluted soils were higher than the Chinese soil quality criteria. The chemical partitioning patterns of Pb, Zn and Cu indicated that Pb was largely associated with the residual and NH 2OH HCl extractable fractions. In contrast, Cd was predominantly associated with the MgCl 2 extractable fraction. A large proportion of Cu was bound to the acidic H 2O 2 extractable fractions, while Zn was predominantly found in the residual phase. The fraction of mobile species, which potentially is the most harmful to the environment, was found to be elevated compared to unpolluted soils in which heavy metals are more strongly bound to the matrix. The mobility of the metals was studied by water extraction using a modification of Tessier’s procedure, and the order of mobility was Zn > Cd > Cu > Pb. 相似文献
9.
The lethal effects of aluminum ion (Al 3+) in tilapia ( Oreochromis niloticus) raised in concrete tanks were investigated. Tilapias were fed daily with commercial feed enriched with known concentrations of Al 3+ and analyzed by differential pulse anodic stripping voltammetry (DPASV). The concentrations of Al 3+ in feces, water, muscle tissue, viscera, and heads were determined every 3 months for a period of 365 days. The Tilapia head was the most affected tissue by Al 3+. In general, Al 3+ bioaccumulation reached the lethal dose (LD 50) after 335 days of experiment as follows: 34.9?mg?kg ?1 (muscle tissue), 88.2?mg?kg ?1 (viscera), and 126.9?mg?kg ?1 (head without gills). After determining Cu 2+, Zn 2+, and Ca 2+ by absorption spectrometry, a decrease in the Ca 2+ concentration was noted in the head during the experimental period. These observations were associated with the occurrence of a decalcification in the bone tissue in the presence of Al 3+. In contrast, it was found that Zn 2+ ions may act as a protective agent against Al 3+-induced contamination. 相似文献
10.
Carbon dioxide (CO 2), nitrous oxide (N 2O) and methane (CH 4) are important greenhouse gases (GHGs). The objective of this study is to quantify the aggregate GHG (CH 4, N 2O and CO 2) emissions and estimate economic losses of three ecosystems (marsh, paddy field and upland) in the Sanjiang Plain, excluding the Muling-Xiangkai Plain, south of Wanda Mountain. The results indicate the economic losses from GHG emissions of marshes were from 6.40 to 7.75?×?10 9 CNY (Chinese Yuan), those of paddy fields were from 1.41 to 3.20?×?10 9 CNY; and from uplands were from 0.26 to 0.49?×?10 9 CNY. Using linear trend analysis, the economic losses through GHG emissions of marshes fell between 1982 and 2005, but those from paddy fields and uplands increased. In our study, the sequence in magnitude of the economic losses from GHG emissions was: marshes > paddy fields > uplands. In fact, the economic value of GHG emissions was negative because of these adverse impacts on the environment. This article could provide a reference for calculation of GHG exchange. The results suggest that improvement of fertiliser use efficiency for more precise agricultural management and returning straw to cropland could mitigate GHG emissions and would help to achieve sustainable development. 相似文献
11.
The present investigation is the first in situ comparative study for the identification of Ni and Cu accumulation strategies involved in Odontarrhena obovata (syn. Alyssum obovatum (C.A. Mey.) Turcz.) growing in Cu-rich smelter-influenced (CSI) and non-Cu-influenced (NCI) sites. The total and Na2EDTA (disodium ethylenediaminetetraacetic acid)-extractable metal concentration in soils and plant tissues (roots, stem, leaves and flowers) were determined for CSI and NCI sites. High concentrations of total Ni, Cr, Co and Mg in the soil suggest serpentine nature of both the sites. In spite of high total and extractable Cu concentrations in CSI soil, majority of its accumulation was restricted to O. obovata roots showing its excluder response. Since the translocation and bioconcentration factors of Ni?>?1 and the foliar Ni concentration?>?1000 μg g?1, it can be assumed that O. obovata has Ni hyperaccumulation potential for both the sites. No significant differences in chlorophyll content in O. obovata leaves were observed between studied sites, suggesting higher tolerance of this species under prolonged heavy metal stress. Furthermore, this species from CSI site demonstrated rather high viability under extreme technogenic conditions due to active formation of antioxidants such as ascorbate, free proline and protein thiols. The presence of Cu in higher concentration in serpentine soil does not exert detrimental effect on O. obovata and its Ni hyperaccumulation ability. Thus, O. obovata could act as a putative plant species for the remediation of Cu-rich/influenced serpentine soils without compromising its Ni content and vitality. 相似文献
12.
Crandallite (Ca,Sr) Al 3 (PO 4) 2 (OH) 5 · H 2O crystallizes in the alunitecrystal lattice. Because of its open structure, the cations Ca 2+, Sr 2+, and Al 3+ can be replaced by various elements depending on their diadochial properties; the element entering into the crystal network thus becomes immobilized. Artificial amorphous crandallite has been shown to eliminate the heavy metal ions: Pb 2+>>Cu 2+>Hg 2+>>Cd 2+ from contamined water in the presence of lateritic phosphates. Pb 2+ could be removed nearly quantitatively in all cases. 相似文献
13.
The extraction of K + and SiO 2 from silicate minerals by Bacillus mucilaginosus in liquid culture was studied in incubation experiments. B. mucilaginosus was found to dissolve soil minerals and mica and simultaneously release K + and SiO 2 from the crystal lattices. In contrast, the bacterium did not dissolve feldspar. B. mucilaginosus also produced organic acids and polysaccharides during growth. The polysaccharides strongly adsorbed the organic acids and attached to the surface of the mineral, resulting in an area of high concentration of organic acids near the mineral. The polysaccharides also adsorbed SiO 2 and this affected the equilibrium between the mineral and fluid phases and led to the reaction toward SiO 2 and K + solubilization. These two processes led to the decomposition of silicate minerals by the bacterium. 相似文献
14.
Lead-contaminated mine tailings were bioremediated using microbial/phyto remediation. The optimum lead accumulation and tolerance capacity of the plant–microbe partnership were investigated, and their mechanisms were evaluated further under varied levels of lead contamination through a flowerpot experiment in a greenhouse. Enzymes activities revealed that bioremediation has improved fertility and metabolism of tailing soil. The removal efficiency of lead was in the order of microbial/phytoremediation?>?phytoremediation. Solanum nigrum L. was not shown to be a hyperaccumulator for lead. Mucor circinelloides significantly enhanced the growth response and lead accumulation in plants more than Mortierella and Trichoderma asperellum. Moreover, Mortierella was discovered to have good metal tolerance capacity under high Pb concentrations (1200 and 1600?mg?kg ?1). The results for lead bioavailability showed that phytostabilisation serves as a major repair pathway for S. nigrum L. Effective fractions were immobilised for decreased bioavailability by T. asperellum and M. circinelloides. On the contrary, an increased amount of lead was mobilised for increased bioavailability by Mortierella. This study provides new insights into the feasibility of using S. nigrum L. and the aforementioned indigenous fungus strains for large-scale bioremediation of mine tailings. 相似文献
15.
Surface sediments were collected from the Yangtze River Estuary (YRE) in May 2012, August 2012, November 2012 and February 2013 to analyse the seasonal and spatial distributions of acid-volatile sulphide (AVS), simultaneously extracted metals (SEM) and the sediment toxicity. An optimised method was used for the AVS and SEM analysis and the results showed that the seasonal variations of AVS were positively correlated with changes in water temperature and the position of higher AVS was relatively fixed. The average of SEM was gradually increased from May 2012 to February 2013 and there were abnormally high values of SEMCu and SEMNi in the YRE. Concentrations of the five SEM components were in the following order: Cd?相似文献
16.
Fe 3O 4 was supported on mesoporous Al 2O 3 or SiO 2 (50 wt.%) using an incipient wetness impregnation method, and Fe 3O 4/Al 2O 3 exhibited higher catalytic efficiency for the degradation of 2,4-dichlorophenoxyacetic acid and para-chlorobenzoic acid aqueous solution with ozone. The effect and morphology of supported Fe 3O 4 on catalytic ozonation performance were investigated based on the characterization results of X-ray diffraction, X-ray photoelectron spectroscopy, BET analysis and Fourier transform infrared spectroscopy. The results indicated that the physical and chemical properties of the catalyst supports especially their Lewis acid sites had a significant influence on the catalytic activity. In comparison with SiO 2, more Lewis acid sites existed on the surface of Al 2O 3, resulting in higher catalytic ozonation activity. During the reaction process, no significant Fe ions release was observed. Moreover, Fe 3O 4/Al 2O 3 exhibited stable structure and activity after successive cyclic experiments. The results indicated that the catalyst is a promising ozonation catalyst with magnetic separation in drinking water treatment. 相似文献
17.
Concentrations of eight trace metals (TMs) in road dust (RD) (particles?<?25 μm) from urban areas of Xinxiang, China, were determined by inductively coupled plasma mass spectrometry. The geometric mean concentrations of Zn, Mn, Pb, As, Cu, Cr, Ni and Cd were 489, 350, 114, 101, 60.0, 39.7, 31.6, and 5.1 mg kg ?1, respectively. When compared with TM levels in background soil, the samples generally display elevated TM concentrations, except for Cr and Mn, and for Cd the enrichment value was 69.6. Spatial variations indicated TMs in RD from park path would have similar sources with main roads, collector streets and bypasses. Average daily exposure doses of the studied TMs were about three orders of magnitude higher for hand-to-mouth ingestion than dermal contact, and the exposure doses for children were 9.33 times higher than that for adults. The decreasing trend of calculated hazard indexes (HI) for the eight elements was As?>?Pb?>?Cr?>?Mn?>?Cd?>?Zn?>?Ni?>?Cu for both children and adults. 相似文献
18.
Pyrite and other iron sulfides are readily oxidized by dissolved oxygen in aqueous phase, producing acidity and Fe 2+, which causes significant environmental problems. Applications of surface coating agents (Na 2SiO 3 and KH 2PO 4) were conducted at Boeun (Chungbuk, South Korea) outcrop site, and their efficiencies to inhibit the oxidation of sulfide minerals were monitored for a long-term period (449 days). The rock sample showed positive Net Acid Production Potential (NAPP = 20.23) and low Net Acid Generation pH (NAGpH = 2.42) values, suggesting that the rock sample was categorized in the potential acid-forming group. For the monitored time period (449 days), field study results showed that the application of Na 2SiO 3 effectively inhibited the pyrite oxidation as compared to KH 2PO 4. Na 2SiO 3 as a surface coating agent maintained pH 5–6 and reduced oxidation of pyrite surface up to 99.95 and 97.70 % indicated by Fe 2+ and SO 4 2? release, respectively. The scanning electron microscope and energy-dispersive X-ray spectrometer analysis indicated that the morphology of rock surface was completely changed attributable to formation of iron silicate coating. The experimental results suggested that the treatment with Na 2SiO 3 was highly effective and it might be applicable on field for inhibition of iron sulfide oxidation. 相似文献
19.
In Tunisia, the water resources are limited, partially renewable and unequally distributed between the wet north and the dry south of the country. The Sminja aquifer in Zaghouan city is located in north-east of Tunisia, between latitudes 36°38′ and 36°47′ and longitudes 9°95′ and 10°12′. This aquifer is used to satisfy the population needs for their domestic purposes and agricultural activities. Water analyses results are expressed by many methods, among which are geochemical methods combined with the geographic information system (GIS) (all schematic presentations of the diagram software (Piper, Riverside, Wilcox…), which can be used to assess the suitability of the Sminja aquifer groundwater for human consumption and irrigation purposes. A total of 23 wells were sampled in January 2013, and the concentrations of major cations (Na +, Ca 2+, Mg 2+ and K +), major anions (Cl ?, SO 4 2? and HCO 3 ?), electrical conductivity and total dissolved solids were analysed. In the Sminja groundwater, the order of the cations dominance was Na > Ca > Mg > K and that of the anions was Cl > HCO 3 > SO 4. All of the analysed samples of the study area exceed chemical values recommended by the World Health Organisation guidelines and Tunisian Standards (NT.09.14) for potability but with different percentages. The aquifer spatial distribution of saturation indices reveals that all groundwater samples are under-saturated with gypsum, halite and anhydrite and are over-saturated with respect to calcite and dolomite based on water quality evaluation parameters for irrigation purposes; here, 87 % of samples in Sminja aquifer groundwater are suitable, whereas 13 % are unsuitable for irrigation uses. 相似文献
20.
The seasonal variation in biogenic fluxes of NH 4 +, PO 4 3? and SiO2 calculated from the nutrient excretion rates of dominant bivalves ( Ruditapes philippinarum and Arcuatula [= Musculista] senhousia), and pore-water nutrient (NH 4 +, PO 4 3?, SiO2 and NO 3 ? + NO 2 ?), sedimentary acid-volatile sulfide (AVS) and benthic chlorophyll- a (Chl- a) concentrations was assessed on an intertidal sandflat in the Seto Inland Sea (Japan) from summer 1994 to autumn 1995. In spite of the large variability between sampling dates and stations, significant correlations between biogenic nutrient fluxes and pore-water nutrient concentrations were found, suggesting a seasonal linkage between bivalve-mediated biological processes and chemical features of sediments. This linkage was stronger in surface (0–0.5 cm) than subsurface (0.5–2 cm) sediments, consistent with the autoecological characteristics of R. philippinarum and A. senhousia inhabiting the uppermost sediment layer. Significant temporal variation in pore-water NO 3 ? + NO 2 ?, sedimentary AVS and benthic Chl- a concentrations was also found, which was related to both occasional extreme events ( e.g., dystrophy) and alternating periods of production and decomposition. This study may serve twofold in (1) contributing to unravel the ecological structure and functioning of natural tidal flats, and the scale of seasonal variability in biotic and sedimentary parameters and (2) providing useful information for assessing the effectiveness of the physico-chemical and biological structure of artificial tidal flats which are growing in number and extension worldwide. 相似文献
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