The brine shrimp (Artemia parthenogenetica) as encapsulation organism for prophylactic chemotherapy of fish and prawn

Brine shrimp (Artemia parthenogenetica) which had ingested three water-insoluble antibacterial drugs i.e. sulfadiazine(SD), oxytetracycline (OTC) and erythromycin estolate (ERY-Es) were fed toTilapia and Mysis IIIof Penaeus orientalis K. The drug contents in the predators were then determined. After administration of drugs toTilapia and Mysis III, through the bio-encapsulation of the brine shrimp, efficacious therapeutical concentration of OTC and ERY-Es (but not SD) in the predators could be reached and maintained for more than 8 hours.     

The Removal of Dissolved Metals by Hydroxysulphate Precipitates during Oxidation and Neutralization of Acid Mine Waters, Iberian Pyrite Belt

This study examines the removal of dissolved metals during the oxidation and neutralization of five acid mine drainage (AMD) waters from La Zarza, Lomero, Esperanza, Corta Atalaya and Poderosa mines (Iberian Pyrite Belt, Huelva, Spain). These waters were selected to cover the spectrum of pH (2.2–3.5) and chemical composition (e.g., 319–2,103 mg/L Fe; 2.85–33.3 g/L SO₄⁼) of the IPB mine waters. The experiments were conducted in the laboratory to simulate the geochemical evolution previously recognized in the field. This evolution includes two stages: (1) oxidation of dissolved Fe(II) followed by hydrolysis and precipitation of Fe(III), and (2) progressive pH increase during mixing with fresh waters. Fe(III) precipitates at pH < 3.5 (stages 1 and 2) in the form of schwertmannite, whereas Al precipitates during stage 2 at pH 5.0 in the form of several hydroxysulphates of variable composition (hydrobasaluminite, basaluminite, aluminite). During these stages, trace elements are totally or partially sorbed and/or coprecipitated at different rates depending basically on pH, as well as on the activity of the SO₄⁼ anion (which determines the speciation of metals). The general trend for the metals which are chiefly present as aqueous free cations (Pb²⁺, Zn²⁺, Cu²⁺, Cd²⁺, Mn²⁺, Co²⁺, Ni²⁺) is a progressive sorption at increasing pH. On the other hand, As and V (mainly present as anionic species) are completely scavenged during the oxidation stage at pH < 3.5. In waters with high activities (> 10⁻¹) of the SO ₄⁼ ion, some elements like Al, Zn, Cd, Pb and U can also form anionic bisulphate complexes and be significantly sorbed at pH < 5. The removal rates at pH 7.0 range from around 100% for As, V, Cu and U, and 60–80% for Pb, to less than 20% for Zn, Co, Ni and Mn. These processes of metal removal represent a significant mechanism of natural attenuation in the IPB.     

黎平双江电站水库暴雨洪水设计

该文选用参证站资料的方法,对黎平县双江电站水库1954—2021年近68 a来逐年最大日降水量采用PearsonⅢ型研究方法和贵州省暴雨洪水计算公式进行研究。结果表明：黎平双江电站水库年最大日降水量年变化呈上升趋势,2010年以后上升趋势较显著。暴雨洪水设计以H_1d=119.29 mm、C_v=0.47、C_s/C_v=3.5作为研究成果,防洪标准按50 a一遇的暴雨洪水设计成果为P=2.0%,日最大降水量=277 mm、洪峰流量=2509 m³·s^-1;洪水校核按500 a一遇的暴雨洪水设计成果为P=0.2%,日最大降水量=391 mm、洪峰流量=3905 m³·s^-1;消能防冲设计标准按30 a一遇的设计成果为P=3.3%,日最大降水量=252 mm、洪峰流量=2209 m³·s^-1。研究成果对黎平双江电站水库预防灾害性强降水、安全渡汛和水库优化调度、提高产能具有十分重要...     

Photochemical activity and characterization of the complex of humic acids with iron(III)

This study examined the effects of humic acids (HA) and Fe(III)–HA complex on the photodegradation of atrazine, one of the most widely used herbicides. It was shown that the photolysis of atrazine proceeded via first-order reaction kinetics and that atrazine photodegradation was inhibited by the presence of HA, whereas the rate for atrazine photolysis was promoted in solutions containing both HA and Fe(III). Interactions of Fe(III) with HA were characterized by SEM, EDX, UV–Vis and FTIR, revealing that Fe(III)–HA complex was formed by ligand exchange between oxygen groups of HA and Fe(III). Using fluorescence spectrometry the stability constant (K_c) and the fraction of fluorophores available for complexation (f) were obtained as log K_c = 4.28 and f = 74%. Photoformed Fe(II) by ligand-to-metal charge-transfer (LMCT) within the Fe(III)–HA complex was the most important factor involved in photolysis of atrazine, since Fe(II) was the reactant to generate hydroxyl radical. Thus, the rate of atrazine photodegradation in natural sunlit waters is dependent on both the amount of iron present and the interaction between HA and iron.     

从风险认知到风险数量化分类

伴随着社会经济和科技的发展,对风险问题的研究成为风险管理的重要一环,风险分类是进行风险保险、风险管理以及建立风险信息数据库的基础。拟从风险认知的角度,通过人们目前比较关注的41种风险构建了风险0 1判断矩阵,用Hayashi数量化理论III,通过Matlab软件,对构建的0 1风险矩阵进行判断计算,得到风险分类图。通过验证,用Hayashi数量化理论Ⅲ对风险的聚类可以取得很好的类别区分效果,类内的风险种类组合与现有的几种政策管理分类框架中的风险类别组合吻合;该方法为风险的数值分类提供了新的思路。     

UV-Vis spectrophotometric and XAFS studies of ferric chloride complexes in hyper-saline LiCl solutions at 25-90 °C

The speciation and thermodynamic properties of ferric chloride complexes in hydrothermal solutions and hypersaline brines are still poorly understood, despite the importance of this element as a micronutrient and ore-component. Available experimental data are limited to room temperature and relatively low chloride concentrations. This paper reports results of UV-Vis spectrophotometric and synchrotron XAFS experiments of ferric chloride complexes in chloride concentrations up to 15 m and at temperatures of 25-90 °C. Qualitative interpretation of the UV-Vis spectra shows that FeCl²⁺, FeCl₂⁺, FeCl_3(aq) and FeCl₄⁻ were present in the experimental solutions. As chloride concentrations increase, higher ligand number complexes become important with FeCl₄⁻ predominating in solutions containing more than 10 m at 25 °C. The predominance fields of FeCl_3(aq) and FeCl₄⁻ expand to lower Cl concentrations with increasing T. Both XANES and UV-Vis spectra reveal a major change in the geometry of the complex between FeCl₂⁺ and FeCl_3(aq). EXAFS data confirm that the number of chloride ligands increases with increasing chloride concentration and show that Fe³⁺, FeCl²⁺ and FeCl₂⁺ share an octahedral geometry. FeCl_3(aq) could be either tetrahedral or trigonal dipyramidal, while FeCl₄⁻ is expected to be tetrahedral. EXAFS data support a tetrahedral geometry for FeCl₄⁻, especially at 90 °C, but do not allow to distinguish between a tetrahedral or trigonal dipyramidal geometry for FeCl_3(aq) because of similar Fe-Cl distances. At room temperature, EXAFS data suggest that FeCl_3(aq) may be a mixture of octahedral and tetrahedral or trigonal dipyramidal forms.The room temperature formation constants for three ferric chloride complexes (FeCl₂⁺, FeCl_3(aq) and FeCl₄⁻) determined from the UV data are generally in good agreement with previous studies. Calculations based on the properties extrapolated to 300 °C show that hematite solubility is much higher than previously estimated, and that the high orders complexes FeCl_3(aq) and FeCl₄⁻ are important at high temperatures even in solutions with low chloride concentrations. The accuracy of these properties is limited by a poor understanding of activity-composition relationships in concentrated electrolytes, and by limitations in the available experimental techniques and extrapolation algorithms; however, the inclusion of higher order complexes in numerical models of ore transport and deposition allows for a more accurate qualitative prediction of Fe behaviour in hydrothermal and hypersaline systems.     

Treatment of arsenic rich waters by the HDS process

Arsenic contaminated waters are not uncommon; indeed from naturally occurring contaminated waters through to those that are a direct consequence of human activities such as mining, all are affecting the quality of water resources worldwide. The ever increasing demands on natural water resources mean that the effective control of this toxic contaminant is paramount and this is reflected in the ever increasing global legislation.There are currently three mechanisms by which arsenic is commercially treated in effluents. These are physical separation processes such as reverse osmosis, precipitation/adsorption processes, some of which are bacterially assisted, and a whole variety of ion exchange processes, again with some bacterial enhancement. The choice of treatment is not only driven by cost but by the chemistry of the water and the water quality standard to be met.In this study a very high arsenic enriched groundwater, containing in excess of 25,000 µg/L arsenic, was treated by a typical treatment method through a continuously operated pilot plant. In the treatment, iron III salts were added to the influent in order to form precipitates with the arsenic and to form an adsorptive surface that would assist with treatment of the enriched water. This addition of iron III salts for the removal of arsenic is common practice in the water treatment industry as the resulting iron III arsenates are highly stable.However, results from the pilot plant show that the process was further enhanced by the addition of small amounts of hydrogen peroxide. Hydrogen peroxide is a powerful oxidising reagent and assists in ensuring the complete conversion of any arsenic III to arsenic V that was then effectively removed in the pilot plant. After treatment residual arsenic levels of 10 µg/L were obtained compared to 68 µg/L without oxidation reagent addition.     

海洋沉积物中异化铁还原细菌还原重金属Cr(VI)研究

利用异化铁还原细菌处理Cr（VI）是重金属污染修复领域的一个新兴研究方向。本文以海洋沉积物中异化铁还原混合菌群为研究对象,分析铁还原细菌异化铁还原性质对重金属Cr（VI）还原效率的影响。菌群异化铁还原性质的实验结果表明,以柠檬酸铁和氢氧化铁为不同电子受体时,菌群异化铁还原的效率存在差异,培养体系累积Fe（Ⅱ）浓度分别为85.08 ±5.85 mg/L和32.55 ±4.78 mg/L。电子受体对混合菌群组成的影响主要表现在,以柠檬酸铁和氢氧化铁为电子受体时,混合菌群多样性Shannon指数分别是4.615和4.158,较对照组高（Shannon指数3.735）。异化还原Fe（Ⅲ）培养体系中,细菌种群的优势菌属是Clostridium,属于梭菌目Clostridiales,表明梭菌是参与Fe（Ⅲ）还原的主要优势菌。菌群异化铁还原性质对Cr（VI）还原效率影响的实验结果表明,柠檬酸铁为电子受体,细菌在Fe（Ⅲ）浓度为1 120 mg/L时异化铁还原效率高,并且还原Cr（VI）达100%。氢氧化铁为电子受体,Fe（Ⅲ）浓度1 680 mg/L时,异化铁还原Cr（VI）效率高（72%）,是对照组4倍。研究结果为进一步应用微生物治理重金属Cr（VI）污染提供理论依据。     

Oxidation mechanisms and chemical bioavailability of chromium in agricultural soil – pH as the master variable

Chromium (Cr) is a heavy metal that exists in soils in two stable oxidation states, +III and +VI. The trivalent species is an essential nutrient, whereas the hexavalent species is highly toxic. This study investigated the environmental impact of Cr^III potentially released into soil from wastes and various materials by determining the risk of oxidation of initially soluble inorganic Cr^III into hazardous Cr^VI. The principal aim was to describe the pH-dependent mechanisms that regulate 1) the formation of Cr^VI from the easily soluble Cr^III and 2) the potential bioavailability of Cr^III and that of Cr^VI species produced in the oxidation of Cr^III in agricultural soil (fine sand, organic carbon 3.2%). The amount of Cr^VI formed in oxic soil conditions was regulated by two counteracting reactions: 1) oxidation of Cr^III into Cr^VI by manganese oxide (Mn^IVO₂) and 2) the subsequent reduction of Cr^VI by organic matter back to Cr^III. The effect of pH on this net-oxidation of Cr^III and on the chemical availability of both Cr^III and Cr^VI species was investigated in soil samples incubated with or without excessive amounts of synthetic MnO₂, over the chemically adjusted pH range of 3.9–6.3 (+22 °C, 47 d). In soil subsamples without added MnO₂, the net-oxidation of Cr^III into Cr^VI (1 mM CrCl₃ in soil suspensions, 1:10 w/V) was negligible. As for the MnO₂-treated soils, at maximum only 4.7% of added Cr^III was oxidized – regardless of the high oxidation potential of these subsamples. The lowest production of Cr^VI was observed under acidic soil conditions at pH ∼4. At low pH, the net-oxidation diminished as result of enhanced reduction of Cr^VI back to Cr^III. At higher pHs, the oxidation was limited by enhanced precipitation (or adsorption) of Cr^III, which lowered the overall amount of Cr^III susceptible for oxidation. Moreover, the oxidation reactions by MnO₂ were inhibited by formation of Cr(OH)₃ coverage on its surface. The pH-dependent chemical bioavailability of added Cr^III differed from that of the Cr^VI formed. At elevated pHs the chemical availability of Cr^III decreased, whereas that of Cr^VI produced increased. However, the risk of Cr^VI formation through oxidation of the easily soluble inorganic Cr^III was considered to be low in agricultural soils high in organic matter and low in innate MnO₂.