Remediation of 2,4-dichlorophenol-contaminated groundwater using nano-sized CaO2 in a two-dimensional scale tank

• Nano CaO₂ is evaluated as a remediation agent for 2,4-DCP contaminated groundwater. • 2,4-DCP degradation mechanism by different Fe²⁺ concentration was proposed. • 2,4-DCP was not degraded in the system for solution pH>10. • The 2,4-DCP degradation area is inconsistent with the nano CaO₂ distribution area. This study evaluates the applicability of nano-sized calcium peroxide (CaO₂) as a source of H₂O₂ to remediate 2,4-dichlorophenol (2,4-DCP) contaminated groundwater via the advanced oxidation process (AOP). First, the effect and mechanism of 2,4-DCP degradation by CaO₂ at different Fe concentrations were studied (Fenton reaction). We found that at high Fe concentrations, 2,4-DCP almost completely degrades via primarily the oxidation of •OH within 5 h. At low Fe concentrations, the degradation rate of 2,4-DCP decreased rapidly. The main mechanism was the combined action of •OH and O₂^•−. Without Fe, the 2,4-DCP degradation reached 13.6% in 213 h, primarily via the heterogeneous reaction on the surface of CaO₂. Besides, 2,4-DCP degradation was significantly affected by solution pH. When the solution pH was>10, the degradation was almost completely inhibited. Thus, we adopted a two-dimensional water tank experiment to study the remediation efficiency CaO₂ on the water sample. We noticed that the degradation took place mainly in regions of pH<10 (i.e., CaO₂ distribution area), both upstream and downstream of the tank. After 28 days of treatment, the average 2,4-DCP degradation level was ≈36.5%. Given the inadequacy of the results, we recommend that groundwater remediation using nano CaO₂: (1) a buffer solution should be added to retard the rapid increase in pH, and (2) the nano CaO₂ should be injected copiously in batches to reduce CaO₂ deposition.     

Recent advances in the photocatalytic reduction of carbon dioxide

Fossil fuels are currently the major energy source and are rapidly consumed to supply the increasing energy demands of mankind. CO₂, a product of fossil fuel combustion, leads to climate change and will have a serious impact on our environment. There is an increasing need to mitigate CO₂ emissions using carbon–neutral energy sources. Therefore, research activities are devoted to CO₂ capture, storage and utilization. For instance, photocatalytic reduction of CO₂ into hydrocarbon fuels is a promising avenue to recycle carbon dioxide. Here we review the present status of the emission and utilization of CO₂. Then we review the photocatalytic conversion of CO₂ by TiO₂, modified TiO₂ and non-titanium metal oxides. Finally, the challenges and prospects for further development of CO₂ photocatalytic reduction are presented.     

左氧氟沙星在蒙脱石存在条件下对大肠杆菌的毒性效应

采用批实验研究了蒙脱石对左氧氟沙星的吸附机理及对左氧氟沙星抗菌作用的影响。结果表明,中性条件下存在培养基时,左氧氟沙星在蒙脱石上前2 h即达到吸附平衡,吸附等温线符合Langmuir吸附方程,吸附率达90%以上;蒙脱石吸附左氧氟沙星存在阳离子交换作用、氢键作用、疏水作用、阳离子键桥作用、静电吸附作用等物理化学过程;蒙脱石本身不具有抑菌、杀菌活性,且由于蒙脱石增大了微生物附着的比表面积,在特定情况下可以促进微生物的生长;扣除其对微生物生长的促进作用后,蒙脱石吸附左氧氟沙星降低了后者的毒性效应,其抑菌率降低约25%。上述结果为进一步研究抗生素在环境中的毒理效应提供了基础依据。     

利用大型土柱自然淋溶条件下研究土壤重金属的迁移及形态转化

为研究不同重金属在土壤中的迁移和形态转化,通过分层填装土柱,在土柱0~5 cm深度范围内添加Pb、Ag、Bi、In、Sb和Sn等重金属污染土壤,并在自然条件下淋溶4 a,分析各重金属在红壤、潮土、黑土和砂土中的迁移速率及其形态组成. 结果表明:①在>30 cm深度范围内,红壤、潮土和黑土中各重金属质量分数与其相应本底值相比变化不大;与试验前土壤相比,砂土整个剖面中6种重金属质量分数均较高. ②6种重金属在4种土壤中的残留率表现为砂土<潮土<黑土<红壤;对于0～10 cm土壤中Pb的残留率,在潮土中大于Ag和Sb,在黑土中大于Ag,在红壤中大于In,在砂土中则大于Sn. ③模拟试验后残留在土柱中的重金属主要分布在土壤表层(0～30 cm),而深层(>30 cm)较少;6种重金属在红壤、潮土、黑土和砂土中的残留率平均值分别为98.0%、65.1%、65.9%和56.5%. ④与添加污染土壤之前相比,试验后土壤中残渣态等稳定形态重金属质量分数较低,其中Pb、In和Sb均以碳酸盐结合态和有机金属络合态为主,Ag和Sn分别以有机金属络合态、双氧水可提取有机结合态和有机金属络合态、无定形铁锰氧化物结合态为主,而Bi则以碳酸盐结合态和双氧水可提取有机结合态为主. 结果显示,红壤中Pb的迁移风险较低,潮土和黑土中Ag、Sb的迁移风险较高,而砂土中Sn和Sb的迁移风险需要格外关注.      

Effects of water quality on the coagulation performances of humic acids irradiated with UV light

The presence of humic acid in drinking water treatment has received significant attention in recent years because of its adverse effects on the removal of many pollutants in coagulation. In this paper, the effects of water quality including pH, turbidity, alkalinity, and hardness on the removal of humic acid were investigated in a UV light hybridized coagulation process. Our results suggested that UV light radiation could effectively improve the removal rate of humic acid in coagulation under both neutral and basic conditions, and the variations of the selected water quality parameters had little adverse effect on the function of UV light. After UV light radiation, the removal rate of the nitro-humic acid (NHA) increased from 20% to 60% in coagulation, and increased further to 75% and 85% for the raw waters with 10.0 NTU kaolin and 100 mg·L^-1 hardness, respectively. In addition to NHA, the removal rates of the humic acid extracted from peat coal (PHA) and the humic acid provided by Japan metals and chemicals company (JHA) in coagulation were also improved, both in the range of 80%–90% after undergoing UV light radiation. By changing the radiation location from prior to coagulation to the flocculation process, similar experimental results were obtained. The formation of positive charged sites after UV light radiation was considered to be the primary factor that led to an enhanced removal of the humic acid in coagulation.     

基于过程的农户土地利用行为模型的设计与模拟研究

通过基于过程的方式来研究农户决策行为已经成为学者们关注的焦点问题之一。论文依据Belief、Desire、Intention（BDI）决策框架,设计基于过程的农户土地利用行为决策模型。模型以农户实际决策而非效益最大化作为行为模拟的假设,对陕西省米脂县高渠乡的典型村落马蹄洼和姜兴庄土地利用变化进行模拟。模拟可以再现农户决策的动态性和反馈性,展示农户学习行为的过程及其影响,揭示农户决策变化的内在机理。利用该模型,对3 种情景下农户土地利用行为进行模拟,对比分析3 种情景的优劣,指出政府未来应当在降低市场风险、规范合作社经营、提高市场预测方面多做工作。文章最后对该种方法的优点和不足进行总结,并指出今后需要加强的方向。     

异噻唑啉酮类杀菌剂对黑斑蛙胚胎和蝌蚪的急性毒性

异噻唑啉酮类杀菌剂1,2-苯并异噻唑-3-酮（BIT）和甲基异噻唑啉酮（MIT）虽已在多种行业中广泛使用,但目前有关其毒性尤其对水体中生物毒性的数据还较少。鉴于BIT和 MIT在水体中普遍存在,本文研究了这两种污染物对两栖动物黑斑蛙胚胎和蝌蚪的急性毒性。黑斑蛙胚胎和蝌蚪分别暴露系列浓度的BIT和 MIT,观察化学品对其生长、发育和运动的影响,计算96小时半数致死浓度（96 h-LC₅₀）和96小时半数致畸浓度（96 h-TC₅₀）,确定最小生长抑制浓度（MCIG）。结果发现,BIT对黑斑蛙胚胎的96 h-LC₅₀和96 h-TC₅₀分别为2.99 mg?L^-1和0.60 mg?L^-1,MCIG小于0.40 mg?L^-1,对蝌蚪的96 h-LC₅₀为6.44 mg?L^-1。MIT对黑斑蛙胚胎的96 h-LC₅₀和96 h-TC₅₀分别为5.30 mg?L^-1和2.36 mg?L^-1,MCIG为2.59 mg?L^-1,对蝌蚪的96 h-LC₅₀为7.58 mg?L^-1。根据《化学农药环境安全评价准则报批稿》中两栖动物蝌蚪急性毒性的分级标准,判定BIT和MIT的毒性等级为中等。该毒性数据为异噻唑啉酮类杀菌剂的环境管理提供参考。     

宝钢特种设备计算机管理系统的研究与应用

简述了宝钢特种设备安全管理理念,提出了宝钢特种设备计算机管理系统的总体思路,并对该系统的应用作了一定描述。     

用EXAFS研究Zn在水锰矿上的吸附-解吸机理

用延展X光吸收精细结构光谱(EXAFS)研究了重金属Zn(Ⅱ)在水锰矿(γ-MnOOH)上吸附产物的微观结构及其吸附机理.结果表明,Zn(Ⅱ)-水锰矿体系中(pH 7.5,0.1mol/LNaNO₃介质,25℃),Zn²⁺主要是通过共用水合Zn²⁺的O原子及水锰矿表面上的O原子形成Zn-O键,从而结合到水锰矿固体表面上的.平均Zn-O原子间距为1.998±0.010 A(n=3).这个Zn-O键键长是六配位的Zn(H₂O)²⁺₆及其水解产物四配位的Zn(OH)₂或Zn(OH)₄^2-各以一定比例混合吸附于水锰矿表面而形成的.同时,对第二配位层(Zn-Mn相互作用)的EXAFS图谱分析证明存在2个典型的Zn-Mn原子间距,即R₁=3.08±0.024A(n=3)和R2=3.54±0.018 A(n=3).这2个Zn-Mn原子距分别对应于水锰矿结构单元MnO6八面体与Zn水合离子ZnO多面体结合的2种方式,即共用2个O原子的边-边结合与共用1个O原子的角-角结合.边-边结合是较强的吸附位,Zn-Mn原子距较短(R₁=3.08A),吸附较不可逆.角-角结合是较弱的吸附位,Zn-Mn原子距较长(R₂=3.54A),吸附较为可逆.这一结果从微观上证明了亚稳平衡态吸附理论(MEA理论)的基本假设,即具有相同吸附密度的同一吸附质由于吸附力强弱以及微观构型的不同可具有不同的化学位,因而证明了修正传统吸附热力学的基本假设(吸附密度为热力学状态函数)的必要性.宏观的吸附-解吸热力学实验表明Zn(Ⅱ)在水锰矿上的吸附是不可逆的,EXAFS结果指出这种不可逆性主要是由Zn水合离子中ZnO多面体与水锰矿结构单元MnO₆八面体之间的边-边结合所导致的.     

中国浏阳农村地区人群暴露参数

以湖南省浏阳市农村地区人群为研究对象,采用问卷调查的方式对研究地区人群的暴露参数进行研究,结果表明:研究地区成人男性、女性的平均体质量分别为62.45和53.71kg,平均体表面积分别为1.710和1.546m2;成人日均饮水摄入量为1428 mL,P₉₅(第95百分位数)为3350mL,其中,日均直接饮水量为1035mL,P₉₅为2500mL;调查地区大米、面粉、鱼类、猪肉、鸡肉、蛋类(鸡蛋和鸭蛋合计)日均摄入量,成人男性为335.54、89.28、15.41、18.48、14.18和21.70g/d,成人女性为269.28、68.45、14.89、16.73、13.11和18.07g/d. 研究还发现,调查地区人群饮用水源以泉水和井水为主,分别占52.42%和36.31%,也有个别人群饮用河水和湖水等地表水. 研究结果与美国和日本暴露参数推荐值相比有较大差异,与我国同类研究相比也存在一定的差异,说明暴露参数具有区域性、种族性等特征.