新疆巩乃斯河水化学分析

通过对伊犁河支流巩乃斯河河水取样分析,结果表明:巩乃斯河河水阴离子中HCO3-占优势,阳离子中Ca2+占主要地位。主要离子含量表现为阴离子HCO3-C l-SO42-;阳离子Ca2+Na++K+Mg2+。巩乃斯河河水均属于HCO3-C l-Ca-Na型水。河水pH为7.56~8.01;矿化度为80~155 mg/L;总硬度为0.620~1.446 mmol/L;河水总碱度为0.778~1.676 mmol/L。另外,对离子浓度的空间变化及离子的来源分析研究表明,巩乃斯河流域的地形,地貌及气候的差异决定了河水主要离子浓度、pH和矿化度自河流上游至下游,基本呈现先逐步降低后显著升高的趋势;巩乃斯河河水主要离子来源于河水对基岩的溶滤作用,同时钠长石斑岩及人类活动所产生的物质也是主要离子的来源之一。     

Paleolimnology of McNearney lake: an acidic lake in northern Michigan

McNearney Lake is an acidic (pH=4.4) lake in the Upper Peninsula of Michigan with low acid neutralizing capacity (ANC=-38 eq L^-1) and high SO _inf4 ^sup2- and aluminium concentrations. Oligotrophy is indicated by high Secchi transparency and by low chlorophyll a, total phosphorus, and total nitrogen concentrations. The lake water is currently acidic because base cations are supplied to the lake water at a low rate and because SO _inf4 ^sup2- from atmospheric deposition was not appreciably retained by the lake sediments or watershed and was present in the water column.This interdisciplinary paleolimnological study indicates that McNearney Lake is naturally acidic and has been so since at least 4000 years B.P., as determined from inferred-pH techniques based on contemporary diatom-pH relationships. Predicted pH values ranged from 4.7 to 5.0 over the 4000-year stratigraphy. Considerable shifts in species composition and abundance were observed in diatom stratigraphy, but present-day distributions indicate that all abundant taxa most frequently occur under acidic conditions, suggesting that factors other than pH are responsible for the shifts. The diatom-inferred pH technique as applied to McNearney Lake has too large an uncertainly and is not sensitive enough to determine the subtle recent changes in lakewater pH expected from changes in atmospheric deposition because: (1) McNearney Lake has the lowest pH in the contemporary diatom data set in the region and confidence intervals for pH predictions increase at the extremes of regressions; (2) other factors in addition to pH may be responsible for the diatom species distribution in the lake and in the entire northern Great Lakes region; (3) McNearney Lake has a well-buffered pH as a consequence of its low pH and high aluminium concentrations and is not expected to exhibit a large pH change as a result of changes in atmospheric deposition; and (4) atmospheric deposition in the region is modest and would not cause a pH shift large enough to be discernable in McNearney Lake.Elevated atmospheric deposition is indicated in recent sediments by Pb, V, and polycyclic aromatic hydrocarbon accumulation rates and to a lesser extent by those of Cu and Zn; however, these accumulation rates are substantially lower than those observed for acidified lakes in the northeastern United States. Although atmospheric loadings of materials associated with fossil fuel combustion have recently increased to McNearney Lake and apparently are continuing, the present study of the diatom subfossil record does not indicate a distinct, recent acidification (pH decrease).Order of the first two authors is alphabetical     

Factors controlling the solubility of aerosol trace metals in the atmosphere and on mixing into seawater

Previous work has shown that the type and pH history of an aerosol governs trace metal solubility in rainwater. This study concentrates on the crustal elements Al, Fe and Mn and identifies additional processes which affect dissolution not only in the atmosphere but also on mixing into seawater. Aerosol dissolution experiments (at aerosol concentrations of about 30 mg 1^–1) show manganese exhibiting high solubility at the low pH values typical of clouds (54±2.5% at pH 2, with results expressed in mole percent units) with 85% of this increase occurring within 6 hours of acidification. The percentage dissolution decreases to 50% at pH values representative of rainwater (pH 5.5) and to 26±4% at pH 8, typical of seawater. No such dramatic solution phase removal occurs at pH 8 in the presence of inorganic anions (to a final solubility of 44±2%). Thus the extent of manganese dissolution depends strongly on whether aerosols are cycled through acidic environments and on subsequent inorganic complexation once rainwater mixes into sea. Aluminium shows highest dissolution (7.1±0.6%) at low pH with 78% of this increase occurring within 6 hours of acidification. Rapid solution phase removal occurs on increasing the pH to that representative of rainwater (to 0.9±0.4% with 87% of this decrease occurring within 15 min). As a consequence of acid cycling and aluminium's amphoteric nature, solubility is enhanced at seawater pH (2.3±0.3%) over that in rain. Iron shows a strong pH-solubility relationship with highest solubility at low pH (4.7±0.2%), 70% of this value being reached within 6 hours of acidification, and decreasing rapidly to 0.17% as pH is raised to 8. Addition of inorganic anions at pH 8 to simulate mixing into seawater causes a further decrease in solubility, perhaps due to anion induced colloid destabilisation. Photochemical reduction also effects solubility under low pH conditions with Fe(II) comprising 1% of the total iron in the Saharan Aerosol used and 8.4% in an Urban material at a pH of 2. This element shows rapid solution phase removal with increasing particulate load which is tentatively rationalised in terms of a simple Kd approach.     

pH effect on Re(VII) and Se(IV) diffusion in compacted GMZ bentonite

In a high-level radioactive waste (HLW) repository, pH has an impact on the solubility, migration, and adsorption of radionuclides. Thus, understanding the effects of pH on the diffusion of radionuclides is essential for long-term disposal of HLW. In this work, the diffusion behaviors of Re(VII) and Se(IV) in compacted Gaomiaozi (GMZ) bentonite at different pH have been investigated by a through-diffusion method. The effective diffusion coefficient, i.e., D_e values of Re(VII) and Se(IV) were in the range of (1.0–2.4) × 10⁻¹¹ m²/s at pH 3.0–10.0 and (0.38–2.3) × 10⁻¹¹ m²/s at pH 3.0–9.0. In the case of Re(VII), the D_e values remained almost unchanged probably because ReO₄⁻ was the dominant species in the pH range of 3.0–10.0. In the case of Se(IV), whose predominant species were HSeO₃⁻ at pH < 9.0 and SeO₃²⁻ at pH ≥ 9.0, the D_e values decreased by a factor of 3–6 at pH 9.0, i.e., D_e (pH < 9.0)/D_e (pH 9.0) ≈ 3–6, implying that the species with a higher valence state had a stronger anion exclusion effect. The decrease in D_e values can be explained by the diffusion species of Se(IV). Additionally, the rock capacity factor α decreased with the increase of pH. HSeO₃⁻ was absorbed on GMZ bentonite with distribution coefficient K_d values in the range of (1.0–2.5) × 10⁻⁴ m³/kg at pH ≤ 8.0, whereas SeO₃²⁻ was negligibly sorbed at pH > 8.0.     

南大洋表层海水酸化研究进展

海洋酸化是全球变化的一个关注点,南大洋CO2吸收量占海洋对人为CO2的吸收量的30%—40%,同时,南大洋是缓冲能力较低、生态系统脆弱的高纬海域,所以,理解南大洋海水酸化过程及其控制因素就显得尤为重要。海水酸化引起海水中碳酸根离子(CO2-3)的浓度、碳酸钙饱和度(Ω)降低,这对成钙类生物碳酸钙(包括文石和方解石)的形成有害,最终可能对生态系统造成危害。了解海洋酸化的影响、预测酸化对海水碳酸盐体系和生态系统的影响具有重要意义。因此,本文对目前南大洋的开阔大洋区以及两个具有代表性的边缘海和海湾的酸化研究概况进行了梳理,试图对南大洋表层海水酸化的研究进行概述、展望未来南大洋海洋酸化研究趋势并提出一些亟须解决的问题。     

胶印含铬废水化学处理工艺条件应用研究

实验研究了胶印含铬废水化学处理的方法及工艺条件。经化学法处理 ,Cr( )和总 Cr的浓度均能达到国家工业污水排放标准 ;研究结果表明 ,废水中 Cr( )还原成 Cr( )的反应 ,还原剂 Na HSO3 投加量应是 Cr( )重量的 7倍以上 ;Cr(OH) 3 的沉淀反应的适宜 p H范围在 7.5～ 8.5 ,以 p H 8.0时为最佳 ;Cr(OH) 3 的沉淀反应的搅拌时间应在 2 0 min以上为宜 ;沉淀反应的烘干沉渣量为废水总 Cr量的 11倍。该实验研究结果可为含铬废水化学处理法的工艺设计提供理论依据     

Influence of Salinity on pH and Aluminum Concentration on the Interaction of Acidic Red Soil with Seawater

Contamination of acidic red soil in the coastal areas of Okinawa Islands is a serious environmental problem. This study was conducted to examine the effects of the salinity on pH and aluminum concentration when the acidic red soil interacts with seawater. Acidic red soil from Gushikawa recreation center was fractionated into bulk soil, coarse sand and silt + clay. Different weights of each fraction were equilibrated with seawater solutions. The pH and concentrations of Al³⁺, Na⁺, K⁺, Ca²⁺ and Mg²⁺ were then analyzed in the extracts. The results showed a decreasing trend of pH with increasing soil to solution ratio while the extracted Al³⁺ revealed an increasing trend. The lowest pH values were 3.85, 4.06, 4.41, 4.66 and their corresponding highest Al³⁺ concentrations were 2.50, 1.01, 0.062 and 0.036 mmolL⁻¹ in the seawater extracts, one-tenth seawater extracts, one-hundredth seawater extracts and one-thousandth seawater solution extracts, respectively. Mostly, the concentrations of Na⁺, Ca²⁺, Mg²⁺ and especially K⁺ decreased with increasing soil weight in the high salinities but showed the opposite trend in the low salinity samples. Potassium concentration decreased by 39%, 53% and 40% in the seawater extracts, one-tenth and one-hundredth seawater extracts but increased by 200% in one-thousandth seawater extracts. The coincidence of the increase in Al³⁺ and H⁺ concentrations, and the decrease of Na⁺, K⁺, Ca²⁺ and Mg²⁺ concentrations in the solutions suggests ion exchange/adsorption, while the increased patterns, particularly at low salinity could be attributed to the dissolution of the species from the soils.