Effects of simulated acid rain on cation release in soils of South China

This paper deals with the release of base cations and Al3+ at the treatment with simulated acid rain (SAR) in main soil types collected from South China. Results showed that the amounts of base cations increased obviously when the pH value of simulated acid rain was lower than 3.0 or 3.5. Compared with the leaching of K+ and Na+, the leaching of Ca2+ and Mg2+ was affected by the pH value of SAR. Only when the amounts of base cations leached from soils exceeded the cation exchange capacity, the pH value of leaching solutions decreased sharply and the amounts of released Al3+ increased. The H+ buffering mechanisms, which were affected notonly by the pH values of SAR, but also by the types and solid components of soils, were proposed for the main soils studied.     

Effects of metal cations on sorption-desorption of p-nitrophenol onto wheat ash

The mutual e ects of metal cations (Cu2+, Pb2+, Zn2+, and Cd2+) and p-nitrophenol (NP) on their adsorption desorption behavior onto wheat ash were studied. Results suggested that Cu2+, Pb2+, and Zn2+ diminished the adsorption and increased the desorption of NP remarkably, while Cd2+ had no such e ect. In contrast, NP diminished the adsorption of Cu2+, Pb2+, and Zn2+ onto ash, however, this suppression e ect depended on the initial concentrations of metal cations. NP had no e ect on Cd2+ adsorption on ash. Fourier transform infrared (FT-IR) and X-ray absorption spectroscopic (XAS) studies suggested the following mechanisms responsible for the metal suppression e ect on NP adsorption: (1) large hydrated Cu2+, Pb2+, and Zn2+ shells occupied the surface of ash and prevent nonspecific adsorption of NP onto ash surface; (2) Cu2+, Pb2+, and Zn2+ may block the micropores of ash, resulting in decreased adsorption of NP; (3) complexation of Cu2+, Pb2+, and Zn2+ was likely via carboxyl, hydroxylic and phenolic groups of wheat ash and these same groups may also react with NP during adsorption. As a “soft acid”, Cd2+ is less e cient in the complexation of oxygencontaining acid groups than Cu2+, Pb2+, and Zn2+. Thus, Cd2+ had no e ect on the adsorption of NP on wheat ash.     

常规金属离子对Fe3O4磁性纳米颗粒悬浮和沉降的影响

水体中的有机质、无机盐及酸碱度是影响纳米材料迁移转化的主要因素.考察了Na~+、Mg~(2+)、Ca~(2+)、Sr~(2+)和Ba~(2+)对Fe_3O_4磁性纳米材料(Magnetic Nanoparticles,MNPs)的沉降作用.结果表明,Fe_3O_4MNPs的沉降作用是水体pH、金属离子化合价、离子强度共同影响的结果.整体上,碱土金属离子较Na~+更能加速Fe_3O_4MNPs的沉降.当pH为5.0时,浓度低于1.0 mmol·L~(-1)的Na~+、Mg~(2+)和Ca~(2+)有助于Fe_3O_4MNPs的悬浮;当浓度大于1.0 mmol·L~(-1)时,较强的离子强度促使Fe_3O_4MNPs团聚,发生沉降.当pH为9.0时,碱土金属离子较Na~+更能促使Fe_3O_4MNPs聚沉.因此,纳米颗粒在水体中的扩散和聚沉需要综合考虑金属离子种类和浓度.     

Evidence for Acidification-Driven Ecosystem Collapse of Danish Erica tetralix Wet Heathland

We report observations of disappearance of Erica tetralix in wet heathland, which is unlikely to be caused by competition, as E. tetralix is dying before its place is taken up by other species. To investigate the causes, we used both old and new data. Results showed that presence of Molinia caerulea and Calluna vulgaris were substantial in the former E. tetralix dominated areas. Measurements of the C/N ratio in the morlayer were between 21 and 26 under the E. tetralix stands. As the expected C/N ratio in a healthy nutrient poor ecosystem like the E. tetralix wet heathland is around 30, this indicates that the ratio is probably decreasing and, correspondingly, the probability of nitrogen leaching from the ecosystem is increasing. The morlayer pH was extremely low—between 3.03 and 3.78. This represents a pH decline since the 1960s, where pH values generally were above 4. This supports the hypothesis that the decrease in morlayer pH is the major factor explaining the disappearance of E. tetralix and that measures to increase pH should be considered as part of the recommendations for relevant future management.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-012-0251-z) contains supplementary material, which is available to authorized users.     

水体中常见无机阳离子对TiO2薄膜光催化还原Cr（Ⅵ）的影响

选择了6种水体中常见的阳离子（Na^＋、Mg^2＋、Ca^2＋、Al^3＋、Cu^2＋、Ni^2＋）,分别考查了其对TiO2薄膜光催化还原Cr（Ⅵ）的影响;从光吸收、无机离子本身的性质对光生电子的捕获及传递等讨论了上述离子影响TiO2薄膜光催化还原Cr（Ⅵ）的反应速率的原因。结果表明：由于其不能捕获光生电子,Na^＋、Mg^2＋、Ca^2＋本身对TiO2薄膜光催化还原Cr（Ⅵ）的反应速率影响不大;Al^3＋吸引电子能力较强,成为光生电子和Cr（Ⅵ）之间的桥梁,促进了Cr（Ⅵ）的还原;浓度为1 mmmol/L时,Cu^2＋显著地促进了Cr（Ⅵ）的光催化还原,其主要原因是Cu^2＋捕获光生电子的能力很强,起到了催化剂的作用,而浓度大于10 mmol/L时,Cu^2＋形成单质Cu以及对紫外光的吸收都使促进作用降低;Ni^2＋未充满的d轨道具有获得并传递光生电子的能力,也促进了Cr（Ⅵ）的还原;在浓度同为1mmol/L时,对Cr（Ⅵ）光催化还原的促进作用依次为：Cu^2＋〉Al^3＋〉Ni^2＋〉Na^＋、Ca^2＋、Mg^2＋。     

Assessment of Uncertainty in Long-Term Mass Balances for Acidification Assessments: A MAGIC Model Exercise

Long-term (1860–2010) catchment mass balance calculations rely on models and assumptions which are sources of uncertainty in acidification assessments. In this article, we report on an application of MAGIC to model acidification at the four Swedish IM forested catchments that have been subject to differing degrees of acidification stress. Uncertainties in the modeled mass balances were mainly associated with the deposition scenario and assumptions about sulfate adsorption and soil mass. Estimated base cation (BC) release rates (weathering) varied in a relatively narrow range of 47–62 or 42–47 meq m⁻² year⁻¹, depending on assumptions made about soil cation exchange capacity and base saturation. By varying aluminum solubility or introducing a dynamic weathering feedback that allowed BC release to increase at more acidic pHs, a systematic effect on predicted changes in acid neutralizing capacity (ΔANC ca. 10–41 μeq l⁻¹) and pH (ca. ΔpH = 0.1–0.6) at all sites was observed. More robust projections of future changes in pH and ANC are dependent on reducing uncertainties in BC release rates, the timing, and extent of natural acidification through BC uptake by plants, temporal changes in soil element pools, and fluxes of Al between compartments.     

苯并三唑在土壤中的吸附特性

为了解苯并三唑(BTA)在水-土系统中的迁移转化,通过批实验方法研究了BTA在华北平原土样(GSS13)中的吸附,考察了平衡时间、土壤投加量、溶液初始p H以及共存阳离子对吸附的影响。结果表明,在初始阶段,土壤对BTA的吸附速率较快,之后随着吸附点位的减少,吸附逐渐变慢;吸附过程符合准二级反应动力学方程。土壤对BTA的平衡吸附为非线性吸附,吸附等温线为Freundlich型;随着土壤投加量的增大,单位质量土壤吸附BTA的量减少,可能原因是所选土壤对BTA的吸附存在"固体浓度效应"。溶液的p H通过改变BTA的存在形式和土壤表面的带电性而影响吸附,当溶液p H在BTA的p Ka2(8.6)附近时,土壤对BTA的吸附效果最好。此外,溶液中共存阳离子对土壤吸附BTA有不同的影响,Na+对吸附影响不明显,而不同浓度Ca2+对BTA的吸附有不同程度的促进作用。     

金属离子对长期污染土壤中多环芳烃解吸的影响

研究了离子强度、不同金属离子对土壤中PAHs表观解吸水平的影响.根据Pearson原理计算了菲、荧蒽、芘和苯并[k]荧蒽等几种PAHs的碱性特征参数并据此分析了其酸碱性类型.结果表明:实验条件下,解吸液中离子强度并非影响土壤中PAHs解吸的控制要素;不同硬度酸性金属离子与PAHs之间的酸碱作用是影响土壤中PAHs解吸水平变化的关键.硬酸性金属离子Ba2+、Al3+、Ca2+对土壤中PAHs的解吸具有促进作用,软酸性离子Hg2+、Ag+则具有抑制作用,比较而言交界酸性金属离子Cu2+、Fe2+、Zn2+在提高土壤中PAHs解吸上作用更加明显.     

天然浑浊水中共存无机阳离子的电动化学特征

引入流动电流这一重要电动化学参量，研究了在天然浑浊水中ＳＣ的基本模式，撮了ＳＣ与水中悬浮胶体颗凿表面电荷量及无机阳离子之间的理论关系，探讨了离子的浓度，性质，存在环境等对体系电动特性的影响，并对水中常见８种阳离子共存条件下的电动化学特性进行了实验分析，从而建立了无机阳离子对胶体的聚沉能力与电动响应特性之间的实际联系。