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1.
Health hazards from heavy metal pollution in water systems are a global environmental problem. Of similar concern is sludge that results from wastewater treatment due to unsatisfactory sludge management technology. Therefore, the effectiveness of using Mg–Al-layered double hydroxide in the removal of heavy metals from mine wastewater was tested and compared with that of calcium hydroxide [Ca(OH)2], which is a common treatment method for heavy metal removal. Initially, the mine wastewater contained cations of the heavy metals iron (Fe), zinc (Zn), copper (Cu), and lead (Pb). The Mg–Al-layered double hydroxides were able to remove 371, 7.2, 121, and 0.4 mg/L of these pollutants, respectively, using the co-precipitation method. The removal of these metals is most effective using 0.5 g Mg–Al-layered double hydroxide (Mg/Al molar ratio 4) and 20 min of shaking. Zn was removed by the formation of Zn(NO3)(OH)·H2O and Zn5(NO3)2(OH)8 when LDH, Mg/Al molar ratios of 4 and 2, respectively, were used. Similarly, Fe, Cu, and Pb were removed by the formation of Fe–Al-layered double hydroxide, Cu2(OH)3·NO3 and Pb4(OH)4(NO3)4, respectively. While Ca(OH)2 is also capable of reducing the heavy metal concentrations below the Japanese recommended values, this analysis shows that using 0.5 g Mg–Al-layered double hydroxide is a better treatment condition for mine wastewater, because it generates lower sludge volumes than 0.1 g of Ca(OH)2. The measured sludge volume was 1.5 mL for Mg–Al-layered double hydroxide and 2.5 mL for Ca(OH)2, a nearly twofold further reduction.  相似文献   

2.
This study investigated the effect of cations and anions on the sorption and desorption of iron (Fe) and manganese (Mn) in six surface calcareous soil samples from Western Iran. Six 10 mM electrolyte background solutions were used in the study, i.e., KCl, KNO3, KH2PO4, Ca(NO3)2, NaNO3, and NH4NO3. NH4NO3 and NaNO3 increased the soil retention of Fe and Mn, whereas Ca(NO3)2 decreased the soil retention of Fe and Mn. Iron and Mn sorption was decreased by NO3 ? compared with H2PO4 ? or Cl?. The Freundlich equation adequately described Fe and Mn adsorption, with all background electrolytes. The Freundlich distribution coefficient (K F) decreased in the order H2PO4 ? > Cl? > NO3 ? for Mn and H2PO4 ? > NO3 ? > Cl? for Fe. The highest sorption reversibility was for Fe and Mn in competition with a Ca2+ background, indicating the high mobility of these two cations. A MINTEQ speciation solubility model showed that Fe and Mn speciation was considerably affected by the electrolyte background used. Saturation indices indicated that all ion background solutions were saturated with respect to siderite and vivianite at low and high Fe concentrations. All ion background solutions were saturated with respect to MnCO3(am), MnHPO4, and rhodochrosite at low and high Mn concentrations. The hysteresis indices (HI) obtained for the different ion backgrounds were regressed on soil properties indicating that silt, clay, sand, and electrical conductivity (EC) were the most important soil properties influencing Fe adsorption, while cation exchange capacity (CEC), organic matter (OM), and Mn-DTPA affected Mn adsorption in these soils.  相似文献   

3.
Tidal marshes act as a buffer system for nutrients in the pore water and play important roles in controlling the budget of nutrients and pollutants that reach the sea. Spatial and seasonal dynamics of pore water nutrients were surveyed in three tidal marshes (Chongming Island, Hengsha Island, and Fengxian tidal flat) near the Yangtze Estuary and Hangzhou Bay from August 2007 to May 2008. Nutrient variations in pore water closely followed seawater quality in the estuaries, while the average concentration of NH4 +–N, the main form of inorganic nitrogen in pore water, was over two orders of magnitude higher than that in seawater which was dominated by nitrate. NH4 +–N export (13.81 μmol m?2 h?1) was lower than the import of (NO3 ?+NO2 ?)–N (?24.17 μmol m?2 h?1) into sediment over the 1-year period, hence reducing N-eutrophication in coastal waters. The export of SiO3 2?–Si and PO4 3?–P from tidal marshes regulated nutrient level and composition and lifted the ratio beyond potentidal element limitation in the coastal system. Moreover, macrophyte plants (Spartina alterniflora and Phragmites australis) played significant roles in controlling nutrient concentration in pore water and its exchange between marshes and estuaries. Fengxian marsh was characterized by higher nutrient concentrations and fluxes than other marshes in response to the more serious eutrophication in Hangzhou Bay than in the Yangtze Estuary.  相似文献   

4.
The bank infiltration (BI) technique may be a viable option if the local climate, hydrological, and geological conditions are conducive. This study was specifically conducted to explore the possibility of using BI to source the polluted surface water in conjunction with groundwater. Three major factors were considered for evaluation: (1) investigation on the contribution of surface water through BI, (2) input of local groundwater, and (3) water quality characteristics of water supply. Initially, the geophysical method was employed to define the subsurface geology and hydrogeology, and isotope techniques were performed to identify the source of groundwater recharge and interaction between surface water and groundwater. The physicochemical and microbiological parameters of the local surface water bodies and groundwater were analyzed before and during water abstraction. Extracted water revealed a 5 %–98 % decrease in turbidity, as well as HCO3 +, SO4 ?, NO3 ?, Al, As, and Ca concentration reduction compared with those of Langat river water. However, water samples from test wells during pumping show high concentrations of Fe2+ and Mn2+. In addition, amounts of Escherichia coli, total coliform, and Giardia were significantly reduced (99.9 %). Pumping test results indicate that the two wells (DW1 and DW2) were able to sustain yields.  相似文献   

5.
Size distribution of PM10 mass aerosols and its ionic characteristics were studied for 2 years from January 2006 to December 2007 at central Delhi by employing an 8-stage Andersen Cascade Impactor sampler. The mass of fine (PM2.5) and coarse (PM10?2.5) mode particles were integrated from particle mass determined in different stages. Average concentrations of mass PM10 and PM2.5 were observed to be 306 ± 182 and 136 ± 84 μg m?3, respectively, which are far in excess of annual averages stipulated by the Indian National Ambient Air Quality Standards (PM10: 60 μg m?3 and PM2.5: 40 μg m?3). The highest concentrations of PM10?2.5 (coarse) and PM2.5 (fine) were observed 505 ± 44 and 368 ± 61 μg m?3, respectively, during summer (June 2006) period, whereas the lower concentrations of PM10?2.5 (35 ± 9 μg m?3) and PM2.5 (29 ± 13 μg m?3) were observed during monsoon (September 2007). In summer, because of frequent dust storms, coarse particles are more dominant than fine particles during study period. However, during winter, the PM2.5 contribution became more pronounced as compared to summer probably due to enhanced emissions from anthropogenic activities, burning of biofuels/biomass and other human activities. A high ratio (0.58) of PM2.5/PM10 was observed during winter and low (0.24) during monsoon. A strong correlation between PM10 and PM2.5 (r 2 = 0.93) was observed, indicating that variation in PM10 mass is governed by the variation in PM2.5. Major cations (NH4 +, Na+, K+, Ca2+ and Mg2+) and anions (F?, Cl?, SO4 2? and NO3 ?) were analyzed along with pH. Average concentrations of SO4 2? and NO3 ? were observed to be 12.93 ± 0.98 and 10.33 ± 1.10 μg m?3, respectively. Significant correlation between SO4 2? and NO3 ? in PM1.0 was observed indicating the major sources of secondary aerosol which may be from thermal power plants located in the southeast and incomplete combustion by vehicular exhaust. A good correlation among secondary species (NH+, NO3 ? and SO4 2?) suggests that most of NH4 + is in the form of ammonium sulfate and ammonium nitrate in the atmosphere. During winter, the concentration of Ca2+ was also higher; it may be due to entrainment of roadside dust particles, traffic activities and low temperature. The molar ratio (1.39) between Cl? and Na+ was observed to be close to that of seawater (1.16). The presence of higher Cl? during winter is due to western disturbances and probably local emission of Cl? due to fabric bleaching activity in a number of export garment factories in the proximity of the sampling site.  相似文献   

6.
A series of natural omphacites from a wide range of P, T occurrences were investigated by electron microprobe (EMP), infrared (IR)-, Mössbauer (MS)- and optical spectroscopy in the UV/VIS spectral range (UV/VIS), secondary ion mass spectrometry (SIMS) and single crystal structure refinement by X-ray diffraction (XRD) to study the influence of hydrogen loss on valence state and site occupancies of iron. In accordance with literature data we found Fe2+ at M1 as well as at M2, and in a first approach assigned Fe3+ to M1, as indicated by MS and XRD results. Hydrogen content of three of our omphacite samples were measured by SIMS. In combination with IR spectroscopy we determined an absorption coefficient: ε i,tot = 65,000 ± 3,000 lmolH2O ?1 cm?2. Using this new ε i,tot value, we obtained water concentrations ranging from 60 to 700 ppm H2O (by weight). Hydrogen loss was simulated by stepwise heating the most water rich samples in air up to 800°C. After heat treatment the samples were analyzed again by IR, MS, UV/VIS, and XRD. Depending on the type of the OH defect, the grade of dehydration with increasing temperature is significantly different. In samples relatively poor in Fe3+ (<0.1 Fe3+ pfu), hydrogen associated with vacancies at M2 (OH bands around 3,450 cm?1) starts to leave the structure at about 550°C and is completely gone at 780°C. Hydrogen associated with Al3+ at the tetrahedral site (OH bands around 3,525 cm?1, Koch-Müller et al., Am Mineral, 89:921–931, 2004) remains completely unaffected by heat treatment up to 700°C. But all hydrogen vanished at about 775°C. However, this is different for a more Fe3+-rich sample (0.2 Fe3+ pfu). Its IR spectrum is characterized by a very intense OH band at 3,515 cm?1 plus shoulder at 3,450 cm?1. We assign this intense high-energy band to vibrations of an OH dipole associated with Fe3+ at M1 and a vacancy either at M1 or M2. OH release during heating is positively correlated with decrease in Fe2+ and combined with increase in Fe3+. That dehydration is correlated with oxidation of Fe2+ is indirectly confirmed by annealing of one sample in a gas mixing furnace at 700°C under reducing conditions keeping almost constant OH? content and giving no indication of Fe2+-oxidation. Obtained data indicate that in samples with a relatively high concentration of Fe2+ at M2 and low-water concentrations, i.e., at a ratio of Fe2+ M2/H > 10 dehydration occurs by iron oxidation of Fe2+ exclusively at the M2 site following the reaction: \( {\left[ {{\text{Fe}}^{{{\text{2 + [ M2]}}}}{\text{OH}}^{ - } } \right]} = {\left[ {{\text{Fe}}^{{{\text{3 + [ M2]}}}} {\text{O}}^{{{\text{2}} - }} } \right]} + {\text{1/2}}\;{\text{H}}_{{\text{2}}} \uparrow . \) In samples having relatively low concentration of Fe2+ at M2 but high-water concentrations, i.e., ratio of Fe2+ M2/H < 5.0 dehydration occurs through oxidation of Fe2+ at M1.  相似文献   

7.
In this study, it is determined physicochemical properties of the groundwater and the spatial variability of physicochemical properties of the groundwater in the Amik plain and as well as assess its suitability for drinking and irrigation. A total 92 groundwater samples were collected from drilled well in June 2012. In addition, the 42 of 92 drilled wells were also sampled in September 2012 to evaluate the changes of groundwater properties. According to t test values, the mean Ca2+, SO4 2?, Mg2+ and TH values in the June period were significantly lower than those of the September period. On the other hand, the mean (CO 3 2?  + HCO3 ?) and RSC and MR values in the June period were significantly higher than those of the September period. The order of relative abundance of major cations in the groundwater (in mg L?1) is in order Na+ > Mg2+ > Ca2+ > K+. The order of the anions abundance (mg L?1) is SO4 2? > Cl? > HCO3 ? > CO3 2? in this research. Log and square-root transformation were carried out for the most of the water properties before the calculation of semivariance. The nugget ratio showed all the variables were strongly spatial dependent except for K+ and Mg2+ and (CO3 2? + HCO3 ?) which showed moderate spatial dependence (ratio ranging from 28 to 49.9 %). Spatial distribution analysis of groundwater quality indicated that The EC, TDS values and Na and Cl? contents which is important water quality parameters increase from northern towards southern. The total hardness values increase also from northwestern towards southwestern.  相似文献   

8.
Groundwater is a vital source for domestic and irrigation purposes in the loess area of Northwest China where climate is arid. However, the quality of groundwater in this area is deteriorating due to intensive industrial and agricultural activities, and this has a great adverse impact on human health. In order to better understand the pollution status of groundwater and the health risks to local residents, comprehensive water quality index was applied to assess the quality of drinking water in Yulin City, Northwest China, and sodium adsorption ratio, sodium percentage, residual sodium carbonate and permeability index were used to evaluate the quality of irrigation water. Moreover, the health risks caused by ingestion of groundwater were evaluated using the model proposed by the Ministry of Environmental Protection of the PR China. The results show that all groundwater samples for irrigation will not induce soil salinization, but more than half of them are not suitable for drinking, and Fe, Mn, TH, Mg2+ and NO3–N are the common contaminants which are mainly from natural processes, industrial and agricultural activities. The health risk assessment indicates that children face greater non-carcinogenic risk than adults. The order of contribution of contaminants to non-carcinogenic risk is NO3 ? > As > F? > Fe > Mn > Ba2+ > Cr6+ > Zn > NO2 ?. The average carcinogenic risk of carcinogens (Cr6+ and As) is 1.17 × 10?4 and 1.37 × 10?4 for adults and children, respectively, which surpasses the permissible level (1 × 10?6) stipulated by the Ministry of Environmental Protection of the PR China. Hence, effective measures are highly demanded to manage groundwater pollution and reduce the risks to human health.  相似文献   

9.
Rainwater plays an important role in scavenging of aerosols and gases from atmosphere, and its chemistry helps to understand the relative contributions of atmospheric pollution sources. The present work is aimed to understand and explain the sources, seasonal patterns and the processes thereof affecting rainwater chemistry in an urban environment of Delhi, India. Rainwater samples (n = 111) collected throughout the year in New Delhi showed alkalinity in general. Eight rainwater samples, collected in late monsoon and winter season, had pH less than 5.6 indicating that Delhi continues to face the prospects of acid rain despite the introduction of compressed natural gas as the clean fuel in city transport. Organic acids could be the possible contributors of acidity in rainwater samples having the fractional acidity (FA) value of 0.174, which is greater than the annual average FA (0.011) and the (Ca2+ + Mg2+ + NH4 +)/(SO4 2? + NO3 ?) ration of more than one. Average acid neutralization factors of cations decrease in the order Ca2+ (1.01) > NH4 + (0.77) > Mg2+ (0.10). However, neutralization by Ca2+ dominates only in summer season as cation-rich dust is transported from the Great Indian Thar Desert to this region by strong summer S–SW winds, while NH4 + dominates in rainwater of other three sampling seasons. Identified dominant sources for soluble ions in rainwater are (1) non-silicate crustal source for carbonates and sulfates of Ca and Mg, (2) emissions from catalytic convertor-fitted vehicles and agriculture fields for NH3 and (3) mixed anthropogenic sources for SO4 2?, NO3 ? and Cl?. Rainwater chemistry showed significant seasonal variations. This could be due to the changes in relative proportions of natural and anthropogenic sources of soluble ions to rainwater. Dominance of anthropogenic sources over crustal sources can result in acidic rains, which can adversely affect the environment and human health in this region.  相似文献   

10.
Mine water samples collected from different mines of the North Karanpura coalfields were analysed for pH, electrical conductivity, total dissolved solids (TDS), total hardness (TH), major anions, cations and trace metals to evaluate mine water geochemistry and assess solute acquisition processes, dissolved fluxes and its suitability for domestic, industrial and irrigation uses. Mine water samples are mildly acidic to alkaline in nature. The TDS ranged from 185 to 1343 mg L?1 with an average of 601 mg L?1. Ca2+ and Mg2+ are the dominant cations, while SO4 2? and HCO3 ? are the dominant anions. A high concentration of SO4 2? and a low HCO3 ?/(HCO3 ? + SO4 2?) ratio (<0.50) in the majority of the water samples suggest that either sulphide oxidation or reactions involving both carbonic acid weathering and sulphide oxidation control solute acquisition processes. The mine water is undersaturated with respect to gypsum, halite, anhydrite, fluorite, aluminium hydroxide, alunite, amorphous silica and oversaturated with respect to goethite, ferrihydrite, quartz. About 40% of the mine water samples are oversaturated with respect to calcite, dolomite and jarosite. The water quality assessment shows that the coal mine water is not suitable for direct use for drinking and domestic purposes and needs treatment before such utilization. TDS, TH, F?, SO4 2?, Fe, Mn, Ni and Al are identified as the major objectionable parameters in these waters for drinking. The coal mine water is of good to suitable category for irrigation use. The mines of North Karanpura coalfield annually discharge 22.35 × 106 m3 of water and 18.50 × 103 tonnes of solute loads into nearby waterways.  相似文献   

11.
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12.
Atmospheric dust is considered to be the major cause of poor air quality due to its contribution to high particulate levels, but their interaction with the acidic gases helps in controlling the level of SO2 and NO2 through ambient neutralization reactions. In the present study, the interaction of acidic gases such as SO2 and NO2 with alkaline dust was investigated during October, 2013–July, 2014 at a site named as Babarpur located at the Trans-Yamuna region of Delhi. The concentration of SO2 ranged from 10 to 170 μg/m3 with an average of 36 μg/m3 while that of NO2 ranged from 15 to 54 μg/m3 with an average of 26?±?8 μg/m3. The results were observed to be well within the National Ambient Air Quality Standard (NAAQS) limits prescribed by the Central Pollution Control Board (CPCB). The average concentrations of SO2 during day and night time were recorded as 31?±?18 and 43?±?53 μg/m3 respectively while the mean concentrations of NO2 during day and night time were recorded as 26?±?7 and 27?±?12 μg/m3 respectively. A positive correlation between SO42? and NO3? was also observed indicating their secondary aerosol formation. In aerosol phase, average concentrations of SO42? during day and night time were 3.9?±?0.3 and 6.5?±?2.3 μg/m3 respectively while that of NO3? were 9.5?±?1.5 and 7.3?±?0.5 μg/m3 respectively. Molar ratios of Ca2+/SO42?, NH4+/SO42?, and NH4+/NO3? were observed as 8, 5, and 1.7 during daytime and 1.5, 0.4, and 0.8 during nighttime respectively. Such molar ratios confirmed high concentrations of sulphate (SO4)2? and low concentrations of nitrate (NO3?) during night time, thereby indicating different pathway of aerosol formation during day and night time. Surface morphology and elemental composition of aerosol samples showed various oval, globular, and platy shapes where the diameter varied from few nm to ~5 μm depending on their precursors. There were certain shapes like grossularite, irregular aggregate, grape-like, triangular, and flattened which indicate the crustal origin of aerosols and their possible role in SO2 and NO2 adsorption.  相似文献   

13.
The physicochemical properties and major ion chemistry of the groundwater sources from alluvial aquifers along the stretch (60 km) of Jhelum River in Kashmir Himalaya were determined in order to identify hydro-geochemical processes and their suitability for drinking purposes. The data depicted that calcium and bicarbonates were dominating among the cations and anions. The results indicate the trend of cation dominance as Ca2+ > Na+ > Mg2+ > K+, whereas anion dominance was in the order of HCO3 ? > Cl? > SO4 2?. Ratio of calcium to magnesium indicated the dissolution of Ca2+ from CaCO3, which results in an increased levels of Ca2+ in the groundwater. Interpretation of Piper Trilinear plot understands the various geochemical processes affecting the groundwater quality and shows groundwater was dominated by Ca–HCO3 type. The pH was recorded in the slightly alkalinity range 7.2–7.8 and was showing positive correlation with HCO3 ?. The chloro-alkaline indices revealed 86% of the sources exchange by a type of base-exchange reactions, rest by cation–anion exchange. Gibbs diagram revealed groundwater sources fall in the category of rock dominance. The concentration of the nitrogen compounds was in the progression of NO3–N > NH4–N > NO2–N, and the PO4 ? fluctuated from 0.12 to 0.22 mg/L. Moreover, corrosivity ratio indicated that water from the majority of sources (71%) is safe to supply using pipes without any corrosive effects, while 29% of sources are corrosive in nature and need non-corrosive pipes for transporting and lifting of groundwater. The results revealed, groundwater samples were within permissible limits as prescribed by International and National standards, for drinking purposes. The State government and NGO’s can show their interest in utilizing such water resources to overcome the shortage of drinking water in a sustainable way for the daily consumption of the people living in the vicinity of Jhelum River.  相似文献   

14.
A new occurrence of Mn-rich rocks was discovered within the high-pressure/low-temperature metamorphic rocks on the Palos peninsula of Syros (Greece). Near the summit of Mount Príonas, a meta-conglomerate consists of calcite (~63 wt%), pink manganian phengite, blue–purple manganian aegirine–jadeite, microcline, albite and quartz. In addition, it contains abundant braunite-rich aggregates (up to ~1.5 cm in diameter) that include hollandite [(Ba0.98–1.02K<0.01Na<0.02Ca<0.03) (Mn 1.02–1.52 3+ Fe 0.38–0.88 3+ Ti0.29–0.92Mn 5.11–5.76 4+ )O16], barite and manganian hematite. Due to metamorphic recrystallization and deformation, the contacts between clasts and matrix are blurred and most clasts have lost their identity. In back-scattered electron images, many aegirine–jadeite grains appear patchy and show variable jadeite contents (Jd10–67). These pyroxenes occur in contact with either quartz or albite. Manganian phengite (3.41–3.49 Si per 11 oxygen anions) is of the 3T type and contains 1.4–2.2 wt% of Mn2O3. At the known P–T conditions of high-pressure metamorphism on Syros (~1.4 GPa/ 470 °C), the mineral sub-assemblage braunite + quartz + calcite (former aragonite) suggests high oxygen fugacities relative to the HM buffer (+7 ≤ ?fO2 ≤ + 17) and relatively high CO2 fugacities. The exact origin of the conglomerate is not known, but it is assumed that the Fe–Mn-rich and the calcite-rich particles originated from different sources. Braunite has rather low contents of Cu (~0.19 wt%) and the concentrations of Co, Ni and Zn are less than 0.09 wt%. Hollandite shows even lower concentrations of these elements. Furthermore, the bulk-rock compositions of two samples are characterized by low contents of Cu, Co and Ni, suggesting a hydrothermal origin of the manganese ore. Most likely, these Fe–Mn–Si oxyhydroxide deposits consisted of ferrihydrite, todorokite, birnessite, amorphous silica (opal-A) and nontronite. Al/(Al + Fe + Mn) ratios of 0.355 and 0.600 suggest the presence of an aluminosilicate detrital component.  相似文献   

15.
Bank infiltration (BI) is one of the solutions to providing raw water for public supply in tropical countries. This study in Malaysia explores the use of BI to supplement a polluted surface-water resource with groundwater. Three major factors were investigated: (1) contribution of surface water through BI to the resulting abstraction, (2) input of local groundwater, and (3) water-quality characteristics of the resulting water supply. A geophysical method was employed to define the subsurface geology and hydrogeology, and isotope techniques were performed to identify the source of groundwater recharge and the interaction between surface water and groundwater. The physicochemical and microbiological parameters of the local surface-water bodies and groundwater were analyzed before and during water abstraction. Extracted water revealed a 5–98 % decrease in turbidity, as well as reductions in HCO3 ?, Cl?, SO4 2?, NO3 ?, Ca2+, Al3+ and As concentrations compared with those of Langat River water. In addition, amounts of E. coli, total coliform and Giardia were significantly reduced (99.9 %). However, water samples from test wells during pumping showed high concentrations of Fe2+ and Mn2+. Pumping test results indicate that the two wells used in the study were able to sustain yields.  相似文献   

16.
The hydrogeochemistry and isotope geochemistry of groundwater from 85 wells in fractured dolomite aquifers of Central Slovenia were investigated. This groundwater represents waters strongly influenced by chemical weathering of dolomite with an average of δ13CCARB value of +2.2 ‰. The major groundwater geochemical composition is HCO3 ? > Ca2+ > Mg2+. Several differences in hydrogeochemical properties among the classes of dolomites were observed when they were divided based on their age and sedimentological properties, with a clear distinction of pure dolomites exhibiting high Mg2+/Ca2+ ratios and low Na+, K+ and Si values. Trace element and nutrient concentrations (SO4 2?, NO3 ?) were low, implying that karstic and fractured dolomite aquifers are of good quality to be used as tap water. Groundwater was generally slightly oversaturated with respect to calcite and dolomite, and dissolved CO2 was up to 46 times supersaturated relative to the atmosphere. The isotopic composition of oxygen (δ18OH2O), hydrogen (δDH2O) and tritium ranged from ?10.3 to ?8.4 ‰, from ?68.5 to ?52.7 ‰ and from 3.5 TU to 10.5 TU, respectively. δ18O and δD values fell between the GMWL (Global Meteoric Water Line) and the MMWL (Mediterranean Meteoric Water Line) and indicate recharge from precipitation with little evaporation. The tritium activity in groundwater suggests that groundwater is generally younger than 50 years. δ13CDIC values ranged from ?14.6 to ?9.3 ‰ and indicated groundwater with a contribution of degraded organic matter/dissolved inorganic carbon in the aquifer. The mass balances for groundwater interacting with carbonate rocks suggested that carbonate dissolution contributes from 43.7 to 65.4 % and degradation of organic matter from 34.6 to 56.3 %.  相似文献   

17.
Microprobe analysis, single crystal X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, and X-ray absorption spectroscopy were applied on Fe-rich osumilite from the volcanic massif of Mt. Arci, Sardinia, Italy. Osumilite belongs to the space group P6/mcc with unit cell parameters a = 10.1550(6), c = 14.306(1) Å and chemical formula (K0.729)C (Na0.029)B (Si10.498 Al1.502)T1 (Al2.706 Fe 0.294 2+ )T2 (Mg0.735 Mn0.091 Fe 1.184 2+ )AO30. Structure refinement converged at R = 0.0201. Unit cell parameter a is related to octahedral edge length as well as to Fe2+ content, unlike the c parameter which does not seem to be affected by chemical composition. The determination of the amount of each element on the mineral surface, obtained through X-ray photoelectron spectroscopy high-resolution spectra in the region of the Si2p, Al2p, Mg1s and Fe2p core levels, suggests that Fe presents Fe2+ oxidation state and octahedral coordination. Two peaks at 103.1 and 100.6 eV can be related to Si4+ and Si1+ components, respectively, both in tetrahedral coordination. The binding energy of Al2p, at 74.5 eV, indicates that Al is mostly present in the distorted T2 site, whereas the Mg peak at 1,305.2 eV suggests that this cation is located at the octahedral site. X-ray absorption at the Fe L2,3-edges confirms that iron is present in the mineral structure, prevalently in the divalent state and at the A octahedral site.  相似文献   

18.
Hydrogeochemical controlling factors for high rate of groundwater contamination in stressed aquifer of fractured, consolidated rocks belonging to semi-arid watershed are examined. The groundwater in mid-eastern part of Prakasam district confining to Musi-Gundlakamma sub-basins is heavily contaminated with nitrate and fluoride. Distinct water chemistry is noticed among each group of samples segregated based on concentration of these contaminants. The nitrate is as high as 594 mg/l and 57 % of the samples have it in toxic level as per BIS drinking water standards, so also the fluoride which has reached a maximum of 8.96 mq/l and 43 % of samples are not fit for human consumption. Nitrate contamination is high in shallow aquifers and granitic terrains, whereas fluoride is in excess concentration in deeper zones and meta-sediments among the tested wells, and 25 % of samples suffer from both NO3 ? and F? contamination. Na+ among cations and HCO3 ? among anions are the dominant species followed by Mg2+ and Cl?. The NO3 ?-rich groundwater is of Ca2+–Mg2+–HCO3 ?, Ca2+–Mg2+–Cl? and Na+–HCO3 ? type. The F?-rich groundwater is dominantly of Na+–HCO3 ? type and few are of Na+–SO4 2? type, whereas the safe waters (without any contaminants) are of Ca2+–Mg2+–HCO3 ?– and Na+–HCO3 ? types. High molecular percentage of Na+, Cl?, SO4 2? and K? in NO3 ? rich groundwater indicates simultaneous contribution of many elements through domestic sewerage and agriculture activity. It is further confirmed by analogous ratios of commonly associated ions viz NO3 ?:Cl?:SO4 2? and NO3 ?:K+:Cl? which are 22:56:22 and 42:10:48, respectively. The F? rich groundwater is unique by having higher content of Na+ (183 %) and HCO3 ? (28 %) than safe waters. The K+:F?:Ca2+ ratio of 10:5:85 and K+:F?: SO4 2? of 16:7:77 support lithological origin of F? facilitated by precipitation of CaCO3 which removes Ca2+ from solution. The high concentrations of Na+, CO3 ? and HCO3 ? in these waters act as catalyst allowing more fluorite to dissolve into the groundwater. The indices, ratios and scatter plots indicate that the NO3 ? rich groundwater has evolved through silicate weathering-anthropogenic activity-evapotranspiration processes, whereas F? rich groundwater attained its unique chemistry from mineral dissolution-water–rock interaction-ion exchange. Both the waters are subjected to external infusion of certain elements such as Na+, Cl?, NO3 ? which are further aggravated by evaporation processes leading to heavy accumulation of contaminants by raising the water density. Presence of NO3 ? rich samples within F? rich groundwater Group and vice versa authenticates the proposed evolution processes.  相似文献   

19.
Groundwater of an aquifer located in the vicinity of a large coal washery near Zarand City, Iran consists of two hydrochemically differing facies, which have been informally designated as groundwater (A) and groundwater (B). Groundwater (A) is native, brackish in composition and is characterized by Na+ > Mg2+ > Ca2+ > K+ and SO4 2? > HCO3 ? > Cl? > NO3 ?. Spearman’s rank correlation coefficient matrices, factor analysis data, and values of chloro-alkaline indices, C ratio and Na+/Cl? molar ratio indicate that in the groundwater (A), the ionic load of Ca2+, Mg2+, Na+, K+, SO4 2? and HCO3 ? is derived essentially from weathering of both carbonates and aluminosilicates and direct cation and reverse cation–anion exchange reactions. Groundwater (B) is the polluted variant of the groundwater (A), brackish to saline in composition, and unlike the groundwater (A), consists of HCO3 ? as the dominant anion. In comparison with the groundwater (A), the groundwater (B) contains higher concentrations of all ions, and its average ionic load (av. = 59.74 me/L) is 1.43 times higher than that of the groundwater (A) (av. = 41.54 me/L). Additional concentrations of Ca2+, Mg2+, K+, SO4 2?, Cl? and HCO3 ? in the groundwater (B) are provided mainly by downward infiltrating water from the coal washery tailings pond and reverse cation–anion exchange reaction between tailings pond water and exchanger of the aquifer matrix during non-conservative mixing process of groundwater (A) and tailings pond water. Certain additional concentrations of Na+, K+ and NO3 ? in the groundwater (B) are provided by other anthropogenic sources. Quality wise, both groundwaters are marginally suitable for cultivation of salt-tolerant crops only.  相似文献   

20.
Sediment-water oxygen and nutrient (NH4 +, NO3 ?+NO2 ?, DON, PO4 3?, and DSi) fluxes were measured in three distinct regions of Chesapeake Bay at monthly intervals during 1 yr and for portions of several additional years. Examination of these data revealed strong spatial and temporal patterns. Most fluxes were greatest in the central bay (station MB), moderate in the high salinity lower bay (station SB) and reduced in the oligohaline upper bay (station NB). Sediment oxygen consumption (SOC) rates generally increased with increasing temperature until bottom water concentrations of dissolved oxygen (DO) fell below 2.5 mg l?1, apparently limiting SOC rates. Fluxes of NH4 + were elevated at temperatures >15°C and, when coupled with low bottom water DO concentrations (<5 mg l?1), very large releases (>500 μmol N m?2 h?1) were observed. Nitrate + nitrite (NO3 ?+NO2 ?) exchanges were directed into sediments in areas where bottom water NO3 ?+NO2 ? concentrations were high (>18 μM N); sediment efflux of NO3 ?+NO2 ? occurred only in areas where bottom water NO3 ?+NO2 ? concentrations were relatively low (<11 μM N) and bottom waters well oxygenated. Phosphate fluxes were small except in areas of hypoxic and anoxic bottom waters; in those cases releases were high (50–150 μmol P m?2 h?1) but of short duration (2 mo). Dissolved silicate (DSi) fluxes were directed out of the sediments at all stations and appeared to be proportional to primary production in overlying waters. Dissolved organic nitrogen (DON) was released from the sediments at stations NB and SB and taken up by the sediments at station MB in summer months; DON fluxes were either small or noninterpretable during cooler months of the year. It appears that the amount and quality of organic matter reaching the sediments is of primary importance in determining the spatial variability and interannual differences in sediment nutrient fluxes along the axis of the bay. Surficial sediment chlorophyll-a, used as an indicator of labile sediment organic matter, was highly correlated with NH4 ?, PO4 3?, and DSi fluxes but only after a temporal lag of about 1 mo was added between deposition events and sediment nutrient releases. Sediment O:N flux ratios indicated that substantial sediment nitrification-denitrification probably occurred at all sites during winter-spring but not summer-fall; N:P flux ratios were high in spring but much less than expected during summer, particularly at hypoxic and anoxic sites. Finally, a comparison of seasonal N and P demand by phytoplankton with sediment nutrient releases indicated that the sediments provide a substantial fraction of nutrients required by phytoplankton in summer, but not winter, especially in the mid bay region.  相似文献   

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