Features of acid–saline systems of Southern Australia

The discovery of layered, SO₄-rich sediments on the Meridiani Planum on Mars has focused attention on understanding the formation of acid–saline lakes. Many salt lakes have formed in southern Australia where regional groundwaters are characterized by acidity and high salinity and show features that might be expected in the Meridiani sediments. Many (but not all) of the acid–saline Australian groundwaters are found where underlying Tertiary sediments are sulfide-rich. When waters from the formations come to the surface or interact with oxidised meteoric water, acid groundwaters result. In this paper examples of such waters around Lake Tyrrell, Victoria, and Lake Dey-Dey, South Australia, are reviewed. The acid–saline groundwaters typically have dissolved solids of 30–60 g/L and pH commonly <4.5. Many contain high concentrations of Fe and other metals, leached from local sediments. The combination of acidity and salinity also releases Ra. Around salt-lakes, these acidic waters often emerge at the surface in marginal spring zones where the low density (ρ ∼ 1.04) regional water flows out over the denser (ρ ∼ 1.16) lake brines. In the spring zones examined, large amounts of Fe are commonly precipitated. In a few places minerals of the alunite-jarosite family are formed which can trap many other metals, including Ra. The studied groundwater systems were discovered by U exploration programs following up radiometric anomalies related to this Ra. Evaporation concentrates the lesser soluble salts (gypsum and some halite) on the surface of the lakes. The lake brines contain most of the more soluble salts and form a column within the porous sediments which is held in place by hydrostatic forces around the salt-lake. These brines are near-neutral in pH.     

Possibility of degradation of phenylarsonic acid in the presence of ferrihydrite

Although inorganic species are predominant in natural systems, but there are many kinds of organoarsenic species such as methylated and phenylated arsenic compounds. Phenylarsonic acid （PA） is a degradation product of organoarsenics used for chemical warfare agents, which has been detected in well water at the disposal site of the agents in Japan. There are few reports studying behavior of PA in soil. In this study, PA was adsorbed onto ferrihydrite and its chemical forms were determined using high performance liquid chromatography connected to inductivity-coupled plasma mass spectrometry （HPLC-ICP-MS）. 100 mg/kg of PA was mixed with 0.03 g of 2-line ferrihydrite. For each suspension, pH was adjusted by HNO3 or NaOH. Each sample was incubated for more than 19 hours and the final pH was measured. After filtration, the chemical form of arsenic in the filtrate was measured using HPLC-ICP-MS. In addition, ferrihydrite separated by filtration was dissolved by 3 ml of 0.5 M HCI and the arsenic species in the solution was detected by HPLC-ICP-MS （column： Tosoh TSKgel SuperlC-AP, eluent： 0.01 M HNO3）. It was verified that PA is not degraded by heating in 0.5 M HCl solution. At pH 3.1, any arsenic compounds were not detected from the solution, because almost all arsenic species were adsorbed onto ferrihydrite at lower pH. At pH= 12, however, 7%-10% of inorganic arsenic was detected in the solution. In solid phase, there are some problems to determine the precise ratio of inorganic and organic species. When the solution includes Fe ion at 0.01 M level, the retention time of arsenic species drifted compared to those in standard solution, which makes it difficult to determine precisely the arsenic species adsorbed on ferrihydrite. Therefore, more study is needed to determine the ratio of inorganic and organic species in the system.     

Influence of humic acid on bioavailability of heavy metals in sediments

The mimetic ocean environment and chemical method were used to research the bioavailability effect of humic acid on five heavy metals in sediment, including Cd, Cu, Zn, Pb and Ni. The sediment was separated into four containers with artificial seawater, and each of them had different concentrations of humic acid. The values of concentrations covered the whole range found in natural sediment （0.1%-10%）. According to the 48 hours LC50 of clam and distribution coefficient, metals were added in artificial seawater, and their speciation was determined at first and then after two days＇ incubation. It was found the bioavailability of heavy metals was reduced in the presence of humic acid. The obvious negative effect on Zn was observed, but the influence on Cd was not remarkable. In addition, the contents of Pb and Ni increased obviously in organic phase, and they are correlative with the concentrations of humic acid.     

Oxidative–reductive photodecomposition of perfluorooctanoic acid in water

This article aims to elucidate on usefulness of vacuum ultraviolet (VUV) for photoreductive degradation of perfluorooctanoic acid (PFOA), a representative perfluorinated compound (PFC), in water for the first time. Bench-scale tests were conducted on oxidative and reductive (with aquated electron: e _aq ^? ) mineralization of PFOA using low-pressure UV (LPUV) lamps and potassium iodide. Unlike with 254 nm wavelength (UVC), the reductive mineralization with VUV was very inefficient compared to the corresponding oxidative mineralization. The inefficiency is attributed to low reactivity of e _aq ^? with PFOA and its fluorinated products than that of 185 nm photons. Direct VUV photolysis of PFOA and its products in reductive reaction conditions was not apparent due to a very big difference in reactivity of 185 and 254 nm photons with iodide. The results demonstrated that highly energetic VUV photons are not suitable for photoreductive degradations of PFCs involving e _aq ^? , but they can be best used for oxidative degradations. These findings should serve as an important reference on VUV usage to decompose refractory micropollutants.     

Solution thermochemistry of humic substances—I. Acid-base equilibria of humic acid

The technique of titration calorimetry has been used to characterize the acidic functional groups of humic acid. Both the concentrations of acidic functional groups and the thermodynamic parameters (pK_a, ΔH_a, etc.) for ionization of these functional groups were determined. The calculated values confirm the generally accepted opinion that humic acid contains both carboxyl and phenolic hydroxyl groups. Furthermore, at least one-third of the phenolic hydroxyl groups are not ortho to carboxyl groups and thus cannot participate in chelation of metal ions via salicylate-like complexing sites. The nature of the remaining two-thirds of the phenolic hydroxyl groups is still unknown.     

The acid lakes and rivers of Copahue Volcano, Argentina

Copahue is an active volcano in the Andes （Argentina, 37.5 S, 71 W） with an acid crater lake, acid chloride-sulfate hot springs feed the Upper Rio Agrio River that discharges into glacial Lake Caviahue. The Lower Rio Agrio outlet mixes with non-acidic meteoric waters, which leads to abundant precipitation of poorly crystalline yellow flocs. Further dilution and neutralization downstream lead to the precipitation of Al-rich material. This river and lake system is an extreme example of a naturally acidified watershed with similarities to streams impacted by acid mine drainage. We determined the chemistry and element fluxes of the Copahue-Caviahue system between 1997 and 2006, and this time series carries data from before, during and after the 2000 Copahue eruptions. The crater lake and hot springs had pH〈0.5 prior to the eruption with up to 6.5 % sulfate and 1% chloride. The fluids were saturated relative to gypsum/anhydrite and copper sulfides. Sulfur isotope studies suggested that the sulfate and associated acidity of the water formed from the disproportionation of magmatic SO2 at about 300℃. Just prior to the eruption, the fluids became saturated with additional minerals, including jarosite and hematite. The Upper Rio Agrio bed became coated with bright red hematite in 2004. Mixing with glacial meltwater increases the pH of the Upper Rio Agrio to values of 1-2, and the input of the Upper Rio Agrio has gradually acidified Lake Caviahue to pHi2.5. Annual element fluxes through the Upper Rio Agrio before the eruption were on the order of 15000 tounes Cl, 25000 tounes SOn and 1500 tounes F, with large outputs of dissolved rock contents as well. Annual volcanogenic trace element fluxes through the river include 7.5 tounes As, 5 tounes B and 0.6 tounes Li. After the eruption, the system became more dilute, the element fluxes decreased and Lake Caviahue became less acidic （pH≈2.8）. In the spring of 2006, the hot springs and crater lake had pH values〈 0.5 once again, suggesting that the system is becoming more active again.     

The impact of acid rain on China’s socioeconomic vulnerability

Acid rain has been a great threat to socioeconomic sustainable development of China; therefore, we develop an indicator system based on the sensitivity and adaptive capacity perspectives and employ the TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) approach to investigate the impact of acid rain on socioeconomic vulnerability of China. Some empirical findings are obtained. First, there is significant provincial difference of socioeconomic vulnerability caused by acid rain in China. Specifically, Tibet, Qinghai, and Shanghai are the top three provinces with the largest vulnerability but Inner Mongolia, Xinjiang, and Jilin are bottom of the rankings. Second, adaptive capacity indicators overall appear more important than sensitivity indicators to measure the vulnerability of acid rain, and the most important indicators are population density and output value of agriculture, forestry, animal husbandry, and fishery while GDP per capita ranks the last. Third, upgrading energy structure and reducing outdated capacity in China prove to be effective means to mitigate vulnerability of acid rain, which has been validated in Guizhou and Hunan provinces. Finally, great attention should be attached to the population increase so as to curb the acid rain vulnerability, especially in Beijing and Tianjin. These results present a basis for future acid rain prevention planning and economic development in China.     

Yellowstone's acid waters: A plethora of chemical and biological activity

Yellowstone National Park contains numerous thermal and non-thermal acid waters with pH=1.23–5.0. These acid-sulfate waters are produced from the microbial oxidation of elemental sulfur which is formed from abiotic oxidation of hydrogen sulfide. Metal co…     

Environmental significance of acid sulfate “clays” as waste covers

The current regulatory requirement for cover soils in landfills and surface impoundments is that the soils attain, upon compaction, a very low hydraulic conductivity of 10^–7 cm/s or less. Although the influence of the interaction between waste chemicals and clay soil on waste migration has been extensively studied, attempts to incorporate as design components the effects of sulfidic (sulfide-bearing) clays on the integrity of clay caps have largely been ignored. These influences may include increasing the permeability of the cover to percolating moisture, enhancing erosion of clay covers, and killing of vegetation on downslopes of the cover. Consequently, it is suggested that clay cap designers test the acid-generating capabilities of potential clay cap materials before exploiting these earth formations. This can be done by incubating a sample of the candidate capping material (with pH > 3.5) under moist aerobic conditions (field capacity) at room temperature. The soil will be said to contain sulfidic materials if it shows a drop in pH (1 1 by weight in water) of 0.5 or more units to a pH value of 4.0 or less within eight weeks. Decisions should then be made as to whether the soil should be avoided or used with amendments to the cap design.Although some of the authors of this article are employees of the United States Enviornmental Agency, the paper has not been subjected to Agency review and no official endorsement should be inferred.     

Geochemical features of the utilization of buried wastes of the Tyrnyauz Tungsten–Molybdenum Plant using acid leaching

The decontamination of buried wastes of the Tyrnyauz Tungsten–Molybdenum Plant is complicated by the geochemical features of the waste composition: low sulfide and high carbonate content, polyelemental composition, and considerable amounts of technogenic admixtures (kerosene, oils, soda, and soluble glasses). These circumstances result in sufficient complication of the suggested technology of waste treatment, including the sulfuric-acid leaching and separate sorption recovery of hazardous and useful elements from the working solution.     

Study on treatment of wastewater from acid in-situ leaching of uranium ore with sulfate reducing bacteria

Synthetic surfactants are among the most widely used chemicals in the world （around 10 millions of tons are produced per year）, mainly as key components in detergent formulation, apart from other applications such as wetting agents or emulsifiers. Coastal ecosystems receive large quantities of these compounds and, after a relatively fast partial degradation in water, the remaining quantities end up in the sediments due to their high affinity for organic carbon in the particulate phase. We therefore focused our studies on sediments because they can be assumed to play an important environmental role acting as a sink for these contaminants. Moreover, because of their widespread use and source specificity, surfactants can usefully be employed as molecular indicators in sediments for more general contamination caused by human activities. This work deals with the vertical distribution in sediment cores of the main anionic surfactants, both linear alkylbenzene sulfonates （LAS） and alkyl ethoxysulfates （AES）, and non-ionic surfactants, including nonylphenol polyethoxylates （NPEOs） and alcohol polyethoxylates （AEOs）. In the case of LAS their degradation metabolites sulfophenyl carboxylic acids （SPCs） are also studied. The processes considered are degradation, sorption and diffusion occurring along the sedimentary column for the different homologues contained in the commercial surfactant mixtures. The most hydrophobic surfactants such as NPEOs and AEOs remain strongly attached to the particulate phase whereas polar metabolites such SPCs tend to be present in the pore water. Highest values of surfactants are found near the surface and, in most cases, there is a decrease in their concentration down the sediment core. Furthermore, the reduction in the average length of the ethoxylated chain in polyethoxylated surfactants, as well as the increase in the concentrations of SPCs at depths showing redox potential from -300 to -400 mV, suggests that surfactants may be degraded anaerobically in the sediment. In the case of LAS, these field results are compared with the data from laboratory experiments carried out in order to determine sorption capacity and anaerobic degradation.     

Facile synthesis of hexamine–silicotungstic acid hybrid and its photocatalytic activity toward degradation of dyes

A new organic hybrid of silicotungstic acid was prepared by means of an easily available, very cheap, and non-toxic amine via a facile precipitation method. Characterization of hybrid was carried out by elemental analyses, Fourier transform infrared spectroscopy, powder X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. Dye adsorption and photocatalytic properties of the prepared water-insoluble hybrid were examined by studying the decolorization of model dyes such as methylene blue and methyl, orange and their mixture solutions under ultraviolet, visible, and sunlight irradiation. The effect of different factors containing the initial concentration, pH, catalyst dosage, H₂O₂ dosage, and salt adding was investigated on the decolorization of dyes. The results showed that the hybrid is a good heterogeneous photocatalyst in the degradation of methylene blue, methyl orange and their mixture and can be recovered and reused. The methylene blue is removed via combination of adsorption and photocatalytic degradation under ultraviolet, visible, and sunlight through direct oxidation by hybrid. The methyl orange is removed via ultraviolet and solar photocatalytic degradation through indirect oxidation by ^·OH radicals. While the visible light is not able to degrade methyl orange solution alone in the presence of hybrid, it degrades the methyl orange mixed with methylene blue solution.     

The acid neutralizing capacity (ANC) of South Africa's freshwater ecosystems

Acidification is considered the most important one of the primary chemical stress factors that impact on freshwater ecosystems. In unpolluted freshwater systems, the primary controls on the degree of acidification are factors such as the geological substr…     

Yellowstone＇s acid waters： A plethora of chemical and biological activity

Yellowstone National Park contains numerous thermal and non-thermal acid waters with pH=1.23-5.0. These acid-sulfate waters are produced from the microbial oxidation of elemental sulfur which is formed from abiotic oxidation of hydrogen sulfide. Metal concentrations are usually very low in these waters so that H^＋ is often the major cation and greater in concentration than Al or Fe.Concentrations of Cu, Zn, Cd, Pb, Co, Ni, and Cr are frequently at or below detection limits. Many of these waters closely approximate pure sulfuric acid solutions. Thermal acid waters have been sampled in Norris Geyser Basin, Gibbon Geyser Basin, Lemonade Creek, and Washburn Springs. Non-thermal acid waters frequently contain high arsenic concentrations. Acid-sulfate waters life： numerous Bacteria, Archaea, and Eukarya. Chemoautotrophs, have been sampled in Brimstone Basin. The thermal acid waters contain an abundance of microbial life from all three domains of phototrophs, and heterotrophs are also common in these waters. Several of these microbes are responsible for the rapid oxidation of iron and arsenic in thermal spring overflows and within large pools. Measured oxidation rates are faster by many orders of magnitude than the abioitic oxidation rates. Common archaea in acid waters include Sulfolobus and Thermoplasma. Common bacteria include Acidithiobacillus, Acidimicrobium, Hydrogenobaculum, and Thiomonas. Common eukarya are algae such as Cyanidium, Euglena, Chlorella, Chlamydomonas, Ulothrix, and Zygogonium. Although aquatic life in acid-sulfate waters is dominated by microbes, insect larvae are also found.     

Production of monoclonal antibody and development of an enzyme-linked immunosorbent assay for the determination of okadaic acid in shellfish from China

An indirect competitive enzyme-linked immunosorbent assay（idc-ELISA） for quantitation of okadaic acid （OA） ,a marine biotoxin associated red tide, was developed by preparation of the monoclonal antibody against OA using cell-fused method.OA was coupled to KLH and OVA using carbodiimide reaction. OA-KLH used as immunogen were injected into Balb/C mice. Titres of the antisera against OA were determinated using OA-OVA as coating ligand by ELISA method. The spleen cells of immunized mice were fused with Sp2/O cells. Clones secreting specific monoclonal antibody were screened by indirect ELISA. After cloning, three hybridoma cell clones stably producing anti-OA monoclonal antibody were obtained. The detection of OA concentrations by indirect competitive ELISA was established. Under excellent condition, the detection limit of OA was 0.781 ng/mL. The level of OA in shellfishes from China was 0.001. A good correlation （R=0.7963） was observed between idc-ELISA and HPLC-MS/MS.     

Mobilization of arsenic from acid deposition – The Elbe River catchment,Czech Republic

Temporal changes of As concentration in surface waters were observed in some areas of the Czech Republic. Mobilized As originates from past atmospheric deposition. To understand the factors influencing As aqueous concentration and mobility the chemistry and runoff generation of a number of brooks, springs and rivers in the central part of the Elbe River catchment, Czech Republic, were monitored. Seasonal variations of As (from 0.5 to 10.5 μg L⁻¹), Fe (from 0.05 to 3.9 mg L⁻¹) and DOC (dissolved organic C – from 1.2 to 17.5 mg L⁻¹) were observed in monitored stream waters with maximum values of As and Fe in the summer months at pH values 7.6–7.8. The concentration of As in particles with a diameter < 60 μm correlates with the Fe concentration. There is no correlation between Fe and As in filtered samples (<0.45 μm). The As concentration in stream water colloids depends on an increase in DOC concentration and a decrease in ionic strength. The DOC stabilizes As in solution and reduces its re-adsorption on Fe colloids and consequently As concentration in the stream increases.     

The acid neutralizing capacity （ANC） of South Africa＇s freshwater ecosystems

Acidification is considered the most important one of the primary chemical stress factors that impact on freshwater ecosystems. In unpolluted freshwater systems, the primary controls on the degree of acidification are factors such as the geological substrate of the catchment area, the presence of organic acids secreted by vegetation in the river system, and equilibrium exchange of carbon dioxide with the atmosphere. Anthropogenic factors that can impact on the degree of acidification of freshwater systems include agricultural, mining and industrial activities, either through direct runoff into river systems or through deposition of atmospheric pollutants from these sources. The capacity factors alkalinity and acidity, which represent the acid- and base-neutralizing capacity （ANC and BCN） of an aqueous system, have been used as more reliable measures of the acidic character of freshwater systems than pH. Unlike pH, ANC and BNC are not affected by parameters such as temperature and pressure. Therefore, ANC has been employed as a predictor of biological status in critical load assessments. Freshwater systems with ANC＇s eq/L isμeq/L are considered sensitive to acidification, ANC=0 μbelow 150 commonly used as the predictor for fish species such as trout in lakes, and an eq/L as more realistic for streams. Acid-neutralizing capacity μANC value of 40 （ANC） can be determined by titration with a strong acid to a preselected equivalence point. Alternatively, it can be calculated as the difference between base cations （[BC]） and strong acid anions （[SAA]）： ANC=[BC]- [SAA]=[Ca^2＋]＋[Mg^2＋]＋[Na^＋]＋[K^＋]-[SO4^2-]-[NO3^-]-[Cl^-] To date, there has been no attempt to establish the ANC of South Africa＇s freshwater ecosystems or variability therein, despite the fact that long-term water quality monitoring data exist for all the parameters needed to calculate it according to the above equations. As a result, the relationship between the acid neutralizing capacity of freshwater ecosystems in South Africa and biodiversity factors, such as fish status, is unknown. Results of the first comprehensive （country-wide scale） evaluation of the acid neutralizing capacity of river systems in South Africa will be presented. Long-term monitoring data obtained from the Department of Water Affairs and Forestry （DWAF） from most of South Africa＇s river systems were used to establish geographic and temporal variabilities in ANC. The results show that the Berg and Breede River systems are most susceptible to acidification, and that geological substrate appears to explain most of the geographic variabilities observed.     

Biochemical, chromatographic and spectroscopic analyses of Suwannee River fulvic acid—Evidence for the presence of a DNA-like material

Naturally occurring organic compounds are complicated materials that are hard to fractionate into individual components. Organic materials from lakes, rivers and oceans often contain biological molecules related to proteins and DNA, and have global enviro…     

Effects of acid rain on physical,mechanical and chemical properties of GGBS–MgO-solidified/stabilized Pb-contaminated clayey soil

Acta Geotechnica - Reactive magnesia (MgO)-activated ground granulated blast furnace slag (GGBS) is a newly developed binder for soil stabilization/solidification. It can be used as an alternative...