Geochemical reactions resulting from in situ oxidation of PCE-DNAPL by KMnO4 in a sandy aquifer

Although the potential for KMnO4 to destroy chlorinated ethenes in situ was first recognized more than a decade ago, the geochemical processes that accompany the oxidation have not previously been examined. In this study, aqueous KMnO4 solutions (10-30 g/L) were injected into an unconfined sand aquifer contaminated by the dense non-aqueous-phase liquid (DNAPL) tetrachloroethylene (PCE). The effects of the injections were monitored using depth-specific, multilevel groundwater samplers, and continuous cores. Two distinct geochemical zones evolved within several days after injection. In one zone where DNAPL is present, reactions between KMnO4 and dissolved PCE resulted in the release of abundant chloride and hydrogen ions to the water. Calcite and dolomite dissolved, buffering the pH in the range of 5.8-6.5, releasing Ca, Mg, and CO2 to the pore water. In this zone, the aqueous Ca/Cl concentration ratio is close to 5:12, consistent with the following reaction for the oxidation of PCE in a carbonate-rich aquifer: 3C2Cl4 + 5CaCO3(s) + 4KMnO4 + 2H+ --> 11CO2 + 4MnO2(s) + H2O + 12Cl- + 5Ca2+ + 4K+. In addition to Mg from dolomite dissolution, increases in the concentration of Mg as well as Na may result from exchange with K at cation-exchange sites. In the second zone, where lesser amounts of PCE were present, KMnO4 persisted in the aquifer for more than 14 months, and the porewater pH increased graduallyto between 9 and 10 as a resultof reaction between KMnO4 and H2O. A small increase in SO4 concentrations in the zones invaded by KMnO4 suggests that KMnO4 injections caused oxidation of sulfide minerals. There are important benefits of carbonate mineral buffering during DNAPL remediation by in situ oxidation. In a carbonate-buffered system, Mn(VII) is reduced to Mn(IV) and is immobilized in the groundwater by precipitating as insoluble manganese oxide. Energy-dispersive X-ray spectroscopy analyses of the manganese oxide coatings on aquifer mineral grains have detected the impurities Al, Ca, Cl, Cu, Pb, P, K, Si, S, Ti, U, and Zn indicating that, similar to natural systems, precipitation of manganese oxide is accompanied by coprecipitation of other elements. In addition, the consumption of excess KMnO4 by reaction with reduced minerals such as magnetite will be minimized because the rates of these reactions increase with decreasing pH. Aquifer cores collected after the KMnO4 injections exhibit dark brown to black bands of manganese oxide reaction products in sand layers where DNAPL was originally present. Mineralogical investigations indicate that the manganese oxide coatings are uniformly distributed over the mineral grains. Observations of the coatings using transmission electron microscopy indicate that they are on the order of 1 microm thick, and consequently, the decrease in porosity through the formation of the coatings is negligible.     

Geochemical and geophysical examination of submarine groundwater discharge and associated nutrient loading estimates into Lynch Cove, Hood Canal, WA

Geochemical tracer data (i.e., 222Rn and four naturally occurring Ra isotopes), electromagnetic (EM) seepage meter results, and high-resolution, stationary electrical resistivity images were used to examine the bi-directional (i.e., submarine groundwater discharge and recharge) exchange of a coastal aquifer with seawater. Our study site for these experiments was Lynch Cove, the terminus of Hood Canal, WA, where fjord-like conditions dramatically limit water column circulation that can lead to recurring summer-time hypoxic events. In such a system a precise nutrient budget may be particularly sensitive to groundwater-derived nutrient loading. Shore-perpendicular time-series subsurface resistivity profiles show clear, decimeter-scale tidal modulation of the coastal aquifer in response to large, regional hydraulic gradients, hydrologically transmissive glacial terrain, and large (4-5 m) tidal amplitudes. A 5-day 222Rn time-series shows a strong inverse covariance between 222Rn activities (0.5-29 dpm L(-1)) and water level fluctuations, and provides compelling evidence for tidally modulated exchange of groundwater across the sediment/water interface. Mean Rn-derived submarine groundwater discharge (SGD) rates of 85 +/- 84 cm d(-1) agree closely in the timing and magnitude with EM seepage meter results that showed discharge during low tide and recharge during high tide events. To evaluate the importance of fresh versus saline SGD, Rn-derived SGD rates (as a proxy of total SGD) were compared to excess 226Ra-derived SGD rates (as a proxy for the saline contribution of SGD). The calculated SGD rates, which include a significant (>80%) component of recycled seawater, are used to estimate associated nutrient (NH4+, Si, PO4(3-), NO3 + NO2, TDN) loads to Lynch Cove. The dissolved inorganic nitrogen (DIN = NH4 + NO2 + NO3) SGD loading estimate of 5.9 x 10(4) mol d(-1) is 1-2 orders of magnitude larger than similar estimates derived from atmospheric deposition and surface water runoff, respectively.     

Influence of net groundwater discharge on the chemical composition of a coastal environment: Flanders Bay, Long Island, New York

Seasonal (October 1997 and May 1998) concentrations of dissolved (< 0.45 micron) trace metals (Ag, Al, Cd, Cu, Fe, Mn), inorganic nutrients (NO3, PO4, Si), DOC and DON were measured at seven wells during periods of low and high groundwater flow, in the aquifer around Flanders Bay in Eastern Long Island, New York. Similar measurements were made in surface waters of Flanders Bay, a shallow coastal embayment with restricted water flushing and river input. Dissolved constituents in the groundwater were classified according to their behavior under different flow conditions as follows: (1) peak during high flow (DOC, pH, Si, NO3, Al and Cu); (2) peak during low flow (salinity, DON, Ag, Cd, Mn); and (3) concentrations independent of flow conditions (PO4 and Fe). The primarily urban and agricultural land use on the North Fork of Long Island was reflected in higher concentrations of nutrients, Cu and Cd in groundwater, compared to samples from the South Fork which is mostly open parkland. Principal component analysis indicated that groundwater seepage could influence the chemical composition of Flanders Bay with respect to the major geochemical carriers (e.g. Fe and Mn). However, mass balance estimates for Cu indicated that, during low flow conditions, net groundwater Cu input was about 10% of the total input. In contrast, during high flow, net groundwater flow could account for up to 58% of all Cu inputs. Nevertheless, a large imbalance, which accounted for up to 70% of the outflux during low aquifer recharge, suggested that the Cu budget of the Bay was not adequately described by the inputs considered (river, net groundwater flow, atmospheric deposition, and tidal exchange). Important missing components of the Cu mass balance in Flanders Bay may include groundwater circulation driven by tides and waves as well as diffusive benthic fluxes.     

正交试验优化蔬菜中水溶态阳离子的离子色谱法提取工艺

目的：研究蔬菜中的Na+、NH4+、K+、Mg2+、Ca2+5 种阳离子的最佳提取工艺条件。方法：用正交试验优化提取工艺条件,并在优化条件下利用离子色谱仪同时测定蔬菜中Na+、NH4+、K+、Mg2+、Ca2+ 离子的含量。结果：影响5 种阳离子同时提取工艺的因素顺序为提取时间、提取功率、溶剂量,提取时间和提取功率对试验有显著性影响;最佳工艺条件为提取时间20min、提取功率160W、溶剂量25mL。对Na+、NH4+、K+、Mg2+、Ca2+5 种阳离子做加标回收实验,得平均加标回收率为89.2%、89.9%、82.7%、87.3%、84.2%。     

GeoChip-based analysis of microbial functional gene diversity in a landfill leachate-contaminated aquifer

The functional gene diversity and structure of microbial communities in a shallow landfill leachate-contaminated aquifer were assessed using a comprehensive functional gene array (GeoChip 3.0). Water samples were obtained from eight wells at the same aquifer depth immediately below a municipal landfill or along the predominant downgradient groundwater flowpath. Functional gene richness and diversity immediately below the landfill and the closest well were considerably lower than those in downgradient wells. Mantel tests and canonical correspondence analysis (CCA) suggested that various geochemical parameters had a significant impact on the subsurface microbial community structure. That is, leachate from the unlined landfill impacted the diversity, composition, structure, and functional potential of groundwater microbial communities as a function of groundwater pH, and concentrations of sulfate, ammonia, and dissolved organic carbon (DOC). Historical geochemical records indicate that all sampled wells chronically received leachate, and the increase in microbial diversity as a function of distance from the landfill is consistent with mitigation of the impact of leachate on the groundwater system by natural attenuation mechanisms.     

Landfill-stimulated iron reduction and arsenic release at the Coakley Superfund Site (NH)

Arsenic is a contaminant at more than one-third of all Superfund Sites in the United States. Frequently this contamination appearsto resultfrom geochemical processes rather than the presence of a well-defined arsenic source. Here we examine the geochemical processes that regulate arsenic levels at the Coakley Landfill Superfund Site (NH), a site contaminated with As, Cr, Pb, Ni, Zn, and aromatic hydrocarbons. Long-term field observations indicate that the concentrations of most of these contaminants have diminished as a result of treatment by monitored natural attenuation begun in 1998; however, dissolved arsenic levels increased modestly over the same interval. We attribute this increase to the reductive release of arsenic associated with poorly crystalline iron hydroxides within a glaciomarine clay layer within the overburden underlying the former landfill. Anaerobic batch incubations that stimulated iron reduction in the glaciomarine clay released appreciable dissolved arsenic and iron. Field observations also suggest that iron reduction associated with biodegradation of organic waste are partly responsible for arsenic release; over the five-year study period since a cap was emplaced to prevent water flow through the site, decreases in groundwater dissolved benzene concentrations at the landfill are correlated with increases in dissolved arsenic concentrations, consistent with the microbial decomposition of both benzene and other organics, and reduction of arsenic-bearing iron oxides. Treatment of contaminated groundwater increasingly is based on stimulating natural biogeochemical processes to degrade the contaminants. These results indicate that reducing environments created within organic contaminant plumes may release arsenic. In fact, the strong correlation (>80%) between elevated arsenic levels and organic contamination in groundwater systems at Superfund Sites across the United States suggests that arsenic contamination caused by natural degradation of organic contaminants may be widespread.     

Field measurements of aerosol particle dry deposition on tropical foliage at an urban site

This paper presents dry deposition of major ions on tropical foliage (leaves of Ashok (Polyalthia longifolia) and Cassia (Cassia siamea)) at St. John's, Agra, an urban site of tropical India on nonrainy, nondewy, and nonfoggy days. The deposition flux was higher on Cassia leaf than Ashok leaf probably due to a rougher surface as shown by scanning electron microscopy. Dry deposition of cations varies from 0.46 to 12.16 mg m(-2) day(-1) while anions vary from 0.04 to 3.24 mg m(-2) day(-1). The percentage contribution of alkaline components is greater than that of acidic components, indicating the alkaline nature of dry deposition. Two-way analysis of variance results reveal significant seasonal variation only for K+, SO4(2-), and F-; however, values varied season to season for Na+, Ca2+, Mg2+, Cl-, NO3-, and NH4+ also. The large seasonal variation in deposition flux may be due to meteorological conditions, diameter of particles, and variation in atmospheric level. SO42- and NO3- show significant correlation, indicating their origin from similar sources while significant correlation between Ca2+ and Mg2+ implies their origin from soil. Poor correlation between Ca2+ and SO4(2-), Ca2+ and NO3-, and Mg2+ and SO4(2-) indicates that in addition to soil other sources also contribute to dry deposition. Low dry deposition fluxes of SO2- and NO3- compared to Ca2+ and Mg2+ may be due to low mass medium diameters of SO4(2-) and NO3- and may be due to uptake through the stomatal pores abundant on leaf surfaces. Factor analysis was employed to identify the sources. F-, Cl, SO4(2-), NO3-, and K+ are grouped together in the first factor, indicating their probable contribution from combustion, Ca2+, Mg2+, and NH4+ are grouped in factor II, which may be attributed to road dust and soil, and factor III includes mainly Na+ and F-, probably contributed from brick-kiln industries. Atmospheric concentrations of F-, Cl-, NOs-, SO4(2-), Na+, K+, Ca2+, Mg2+, and NH4+ were found to be 0.38, 2.28, 1.31, 2.74, 0.44, 0.59, 1.21, 1.2, and 2.29 microg m(-3), respectively.     

Noble gas excess air applied to distinguish groundwater recharge conditions

The application of geochemical tracers in groundwater studies can provide valuable insights into the rates and sources of groundwater recharge, residence times, and flow dynamics that are of significant value in the management of this important natural resource. This paper demonstrates the application of noble gas excess air to distinguish groundwater bodies with different recharge histories in a layered sandstone aquifer system in the east of England. The sampled groundwaters are all supersaturated with respect to neon, indicating the presence of excess air. The lowest excess air concentrations occur where the aquifer is unconfined (deltaNe, the proportion of neon in excess of saturation, = 12-26%) and recharge occurs directly to the outcrop. Groundwater in the confined part of the aquifer can be divided into two hydrochemical types based upon the dissolved ion chemistry: Type 1 groundwaters contain more excess air (deltaNe = 115-120%) than Type 2(deltaNe = 22-62%). The difference in excess air concentrations confirms that groundwater enters the confined aquifer along two discrete pathways. Furthermore, excess neon concentrations predicted from the magnitude of annual water table fluctuation observed in the different recharge areas are in good agreement with those measured in the corresponding groundwaters. We therefore recommend that excess air may be usefully employed as a direct indicator of the volume of long-term net annual groundwater recharge.     

Organic matter and modeling redox reactions during river bank filtration in an alluvial aquifer of the Lot River, France

A 3 year study of the infiltration of Lot River water into a well field located in an adjacent gravel and clay alluvial aquifer was conducted to assess the importance of organic matter regarding the redox processes which influence groundwater quality in a positive (denitrification) or negative (Mn dissolution) manner. Chloride was used to quantify the mixing of river water with groundwater. According to modeling with PHREEQC, the biodegradation of the infiltrated dissolved organic carbon (DOCi) is not sufficient to explain the observed consequences of the redox reactions (dissolved O2 depletion, denitrification, Mn dissolution). Another electron donor source must therefore be involved: we propose solid organic carbon (SOC) as a likely candidate, if made available for degradation by prior hydrolysis. Its contribution to redox reactions could be significant (30-80% of the total organic carbon consumed by redox reactions during river bank filtration). We show here also that even though the first few meters of infiltration are highly reactive, significant redox reactions can take place further in the aquifer, possibly affecting groundwater quality away from the river bank.     

Cyanogen bromide formation from the reactions of monobromamine and dibromamine with cyanide ion

Cyanide ion (CN-) was found to reactwith monobromamine (NH2Br) and dibromamine (NHBr2) according to the reactions NH2Br + CN- + H20 --> NH3 + BrCN + OH- and NHBr2 + CN- + H20 --> NH2Br + BrCN + OH- with respective reaction rate constants of 2.63 x 10(4) M9-10 s(-1) and 1.31 x 10(8) M(-1) s(-1). These values were found to be 10(5)-10(6) times greater than those for the corresponding reactions between chloramine species and CN-. As a result, bromamines, even if present at relatively low concentrations, would tend to outcompete chloramines in reacting with CN-, and thus, the formation of BrCN would predominate that of ClCN through these reaction mechanisms. The NH2Br reaction was found to be general-acid-catalyzed. The third-order catalysis rate constants for H+, H2PO4-, HPO4(2-), H3BO3, and NH4+ correlated linearly with their corresponding acid dissociation constants, consistent with the Br?nsted-Pedersen relationship. The NHBr2 reaction did not undergo catalysis. A model was developed to predict the concentrations of bromamines over time on the basis ofthe above two reactions with CN- and bromamine formation/decomposition reactions previously reported.     

再生新闻纸生产过程中循环白水的DCS分析

对再生新闻纸生产过程循环白水中的溶解和胶体物质（DCS）进行了分析,并与未经循环的白水进行了对比。结果表明：由于白水封闭循环使用,致使系统中的DCS不断积聚,使其溶解物质含量、灰分、电导率、浊度、CODCr都有所升高,而胶体物质含量、Zate电位、平均粒径、木素含量降低。白水循环使用后DCS中的Na＋、K＋含量大幅增加;而Ca2＋、Mg2＋、Fe3＋、Al3＋的含量则有所降低。GC-MS分析表明,循环白水DCS的成分更复杂,含有较多的脂肪酸和树脂酸类物质。其中脱氢枞酸、邻苯二甲酸酯、胆甾醇等含量较高。     

无机离子对酸性蛋白酶活性的影响

研究了Na^＋，K^＋，NH4^＋，Mg^2＋,Ba2^＋,Sr^2＋＇Zn^2＋，Ni^2＋，Cd^2＋,Cu^2＋,Hg^2＋,Fe^3＋，Cr^3＋，Al^3＋等无机离子对酸性蛋白酶活性的影响。随着这些离子浓度的变化，对酶活性的激活或抑制均有变化。其结果对酸性蛋白酶的利用提供了一定的实验依据。     

Flushing history as a hydrogeological control on the regional distribution of arsenic in shallow groundwater of the Bengal Basin

Whereas serious health consequences of widespread consumption of groundwater elevated in As have been documented in several South Asian countries, the mechanisms responsible for As mobilization in reducing aquifers remain poorly understood. We document here a previously unrecognized and consistent relationship between dissolved As concentrations in reducing groundwater and the phosphate-mobilizable As content of aquifer sediment for a set of precisely depth-matched samples from across Bangladesh. The relationship holds across nearly 3 orders of magnitude in As concentrations and suggests that regional as well as local patterns of dissolved As in shallow groundwater are set by the solid phase according to a remarkably constant ratio of approximately 250 microg/L dissolved As per 1 mg/kg P-mobilizable As. We use this relationship in a simple model of groundwater recharge to propose that the distribution of groundwater As in shallow aquifers of the Bengal Basin could primarily reflect the different flushing histories of sand formations deposited in the region over the past several thousand years.     

Natural humics impact uranium bioreduction and oxidation

Although humic substances occur ubiquitously in soil and groundwater, their effect on the biological reduction of uranium(VI) and subsequent reoxidation of U(IV) is poorly understood. This study investigated the role of humics in enhancing the bioreduction of U(VI) in laboratory kinetic studies, in field push-pull tests, and in the presence or absence of metal ions such as Ca2+ and Ni2+, which are known to inhibit the biological reduction of U(VI). Results from laboratory experiments indicate that, under strict anaerobic conditions, the presence of humic materials enhanced the U(VI) reduction rates (up to 10-fold) and alleviated the toxicity effect of Ni2+ on microorganisms. Humic acid was found to be more effective than fulvic acid in enhancing the reduction of U(VI). Such an enhancement effect is attributed to the ability of these humics in facilitating electron-transfer reactions and/or in complexing Ca2+ and Ni2+ ions. Similarly, field push-pull tests demonstrated a substantially increased rate of U(VI) reduction when humic acid was introduced into the site groundwater. However, humics were also found to form complexes with reduced U(IV) and increased the oxidation of U(IV) (when exposed to oxygen) with an oxidation halflife on the order of a few minutes. Both of these processes render uranium soluble and potentially mobile in groundwater, depending on site-specific and dynamic geochemical conditions. Future studies must address the stability and retention of reduced U(IV) under realistic field conditions (e.g., in the presence of dissolved oxygen and low concentrations of complexing organics).     

Sources of sulfate supporting anaerobic metabolism in a contaminated aquifer

Field and laboratory techniques were used to identify the biogeochemical factors affecting sulfate reduction in a shallow, unconsolidated alluvial aquifer contaminated with landfill leachate. Depth profiles of 35S-sulfate reduction rates in aquifer sediments were positively correlated with the concentration of dissolved sulfate. Manipulation of the sulfate concentration in samples revealed a Michaelis-Menten-like relationship with an apparent Km and Vmax of approximately 80 and 0.83 microM SO4(-2) x day(-1), respectively. The concentration of sulfate in the core of the leachate plume was well below 20 microM and coincided with very low reduction rates. Thus, the concentration and availability of this anion could limit in situ sulfate-reducing activity. Three sulfate sources were identified, including iron sulfide oxidation, barite dissolution, and advective flux of sulfate. The relative importance of these sources varied with depth in the alluvium. The relatively high concentration of dissolved sulfate at the water table is attributed to the microbial oxidation of iron sulfides in response to fluctuations of the water table. At intermediate depths, barite dissolves in undersaturated pore water containing relatively high concentrations of dissolved barium (approximately 100 microM) and low concentrations of sulfate. Dissolution is consistent with the surface texture of detrital barite grains in contact with leachate. Laboratory incubations of unamended and barite-amended aquifer slurries supported the field observation of increasing concentrations of barium in solution when sulfate reached low levels. At a deeper highly permeable interval just above the confining bottom layer of the aquifer, sulfate reduction rates were markedly higher than rates at intermediate depths. Sulfate is supplied to this deeper zone by advection of uncontaminated groundwater beneath the landfill. The measured rates of sulfate reduction in the aquifer also correlated with the abundance of accumulated iron sulfide in this zone. This suggests that the current and past distributions of sulfate-reducing activity are similar and that the supply of sulfate has been sustained at these sites.     

Use of strontium isotopes to identify buried water main leakage into groundwater in a highly urbanized coastal area

Previous studies indicate that the local aquifer systems in the Mid-Levels, a highly urbanized coastal area in Hong Kong, have commonly been affected by leakage from water mains. The identification of leakage locations was done by conventional water quality parameters including major and trace elements. However, these parameters may lead to ambiguous results and fail to identify leakage locations especially where the leakage is from drinking water mains because the chemical composition of drinking water is similar to that of natural groundwater. In this study, natural groundwater, seepage in the developed spaces, leakage from water mains, and parent aquifer materials were measured for strontium isotope (87Sr/86Sr) compositions to explore the feasibility of using these ratios to better constrain the seepage sources. The results show that the 87Sr/86Sr ratios of natural groundwater and leakage from water mains are distinctly different and thus, they can provide additional information on the sources of seepage in developed spaces. A classification system based on the aqueous 87Sr/86Sr ratio is proposed for seepage source identification.     

Nitrate contamination in groundwater on an urbanized dairy farm

Urbanization of rural farmland is a pervasive trend around the globe, and maintaining and protecting adequate water supplies in suburban areas is a growing problem. Identification of the sources of groundwater contamination in urbanized areas is problematic, but will become important in areas of rapid population growth and development. The isotopic composition of NO3 (delta15N(NO3) and delta18O NO3), NH4 (delta15N(NH4)), groundwater (delta2H(wt) and delta18O(wt)) and chloride/bromide ratios were used to determine the source of nitrate contamination in drinking water wells in a housing development that was built on the site of a dairy farm in the North Carolina Piedmont, U.S. The delta15N(NO3) and delta18O NO3 compositions imply that elevated nitrate levels at this site in drinking well water are the result of waste contamination, and that denitrification has not significantly attenuated the groundwater nitrate concentrations. delta15N(NO3) and delta18O(NO3) compositions in groundwater could not differentiate between septic effluent and animal waste contamination. Chloride/ bromide ratios in the most contaminated drinking water wells were similar to ratios found in animal waste application fields, and were higher than Cl/Br ratios observed in septic drain fields in the area. delta18O(wt) was depleted near the site of a buried waste lagoon without an accompanying shift in delta2H(wt) suggesting water oxygen exchange with CO2. This water-CO2 exchange resulted from the reduction of buried lagoon organic matter, and oxidation of the released gases in aerobic soils. delta18O(wt) is not depleted in the contaminated drinking water wells, indicating that the buried dairy lagoon is not a source of waste contamination. The isotope and Cl/Br ratios indicate that nitrate contamination in these drinking wells are not from septic systems, but are the result of animal waste leached from pastures into groundwater during 35 years of dairy operations which did not violate any existing regulations. Statutes need to be enacted to protect the health of the homeowners that require well water to be tested prior to the sale of homes built on urbanized farmland.     

不同饮用水对惠明茶茶汤品质的影响

分别用纯净水（PW）、瓶装天然水（TR1,TR2）、瓶装矿泉水（MW1,MW2）和城市自来水（TW）冲泡惠明茶,比较了6种水冲泡茶汤的理化指标、生化成分以及感官品质,并用固相微萃取与气相色谱-质谱联用技术分析了茶汤香气成分。结果表明:不同水样对惠明茶茶汤中理化性质有明显影响,Ca2+、Mg2+浓度较高的MW1、MW2和TW冲泡茶汤中Ca2+浓度明显降低,Mg2+、电导率增加量均小于TR1、TR2和PW。呈味物质上,不同水样茶汤中游离氨基酸与Ca2+、Mg2+、pH可溶性总糖与pH,茶多酚与Ca2+、Mg2+、pH、电导率存在极显著相关性（P<0.01）。呈香物质上,TR1（7429 μg·kg-1）、PW （7422 μg·kg-1）茶汤香气物质含量远高于其他水样（约5100 μg·kg-1）,并且大部分香气物质与水样Ca2+、pH之间存在显著负相关性（P<0.05）,与可溶性总糖、游离氨基酸存在显著正相关性（P<0.05）。感官品质上,TR1、TR2明显优于其他水样,其中TR2的汤色和滋味较好,TR1的香气评价最好。因此,水样的pH、Ca2+浓度越低,茶汤香气物质含量越多,香气品质越好。     

Potential impacts of leakage from deep CO2 geosequestration on overlying freshwater aquifers

Carbon Capture and Storage may use deep saline aquifers for CO(2) sequestration, but small CO(2) leakage could pose a risk to overlying fresh groundwater. We performed laboratory incubations of CO(2) infiltration under oxidizing conditions for >300 days on samples from four freshwater aquifers to 1) understand how CO(2) leakage affects freshwater quality; 2) develop selection criteria for deep sequestration sites based on inorganic metal contamination caused by CO(2) leaks to shallow aquifers; and 3) identify geochemical signatures for early detection criteria. After exposure to CO(2), water pH declines of 1-2 units were apparent in all aquifer samples. CO(2) caused concentrations of the alkali and alkaline earths and manganese, cobalt, nickel, and iron to increase by more than 2 orders of magnitude. Potentially dangerous uranium and barium increased throughout the entire experiment in some samples. Solid-phase metal mobility, carbonate buffering capacity, and redox state in the shallow overlying aquifers influence the impact of CO(2) leakage and should be considered when selecting deep geosequestration sites. Manganese, iron, calcium, and pH could be used as geochemical markers of a CO(2) leak, as their concentrations increase within 2 weeks of exposure to CO(2).     

Has submarine groundwater discharge been overlooked as a source of mercury to coastal waters?

We measured the mercury (Hg) in groundwater, aquifer sediments, and surface water in Waquoit Bay (Massachusetts) and found that this toxic metal (range: <3.2-262 pM) was being released within the subterranean estuary, with similarly high levels (range: 18-256 pM) found in the surface waters of the bay. None of the dissolved species (DOC, chloride, and Fe) normally observed to influence Hg partitioning correlated well with the observed Hg concentrations. It was hypothesized that this was in part due to the variable loading in time and space of Hg onto the aquifer sands in combination with the seasonality of groundwater flow through the aquifer. Aquifer sediment samples from the study site ranged from <1 to 12.5 pmol of Hg/g of sediment, suggesting log Kd values on the order of 1. We hypothesize that this was due to the low organic carbon content typical of the aquifer sediments. Last, itwas estimated that submarine groundwater discharge supplied 0.47-1.9 nmol of Hg m(-2) day(-1) to the bay, which is an order of magnitude higher than the atmospheric deposition rate for the northeastern U.S.