零价锌降解四氯乙烯的反应动力学模型研究

对零价锌(Zn(0))降解四氯乙烯(PCE)进行批实验,在假设各化学反应符合准一级反应的前提下,建立了多级链式平行反应数学模型,并使用混合函数遗传算法进行了动力学参数的反演.结果表明,在106h后残留物基本上为C2H4和C2H2.计算显示,氯代烃的反应活性大小为C2Cl2＞C2HCl＞t-DCE(反二氯乙烯)＞1,1-DCE(1,1-二氯乙烯)＞TCE(三氯乙烯)＞c-DCE(顺二氯乙烯)＞PCE;在4条重要的反应路径中,最重要的是PCE→TCE→t-DCE→C2H2→C2H4和PCE→C2Cl2→t-DCE→C2H2→C2H4;最终94.77%的PCE转化为C2H4,5.23%的PCE转换成了氯乙烯(VC).     

南京北郊降水无机离子和有机酸的化学特征及来源分析

连续收集2016年12月至2017年11月期间的南京降水样品,分析主要无机离子和有机酸的化学特征及季节变化,运用正交矩阵因子模型法(PMF)进行源解析.结果表明,南京地区降水pH均值为5.6,离子总浓度雨量加权平均值为297.3μmol·L^-1,阳离子浓度依序为NH⁺₄> Ca²⁺> K⁺> Na⁺> Mg²⁺,阴离子浓度则为NO^-₃> SO^2-₄> Cl^-> F^-.总有机酸浓度雨量加权平均值为2.86μmol·L^-1,占总阴离子的2.2%. CHO^-₂、C₂H₃O^-₂和C₂O^2-...     

天津市高校夏季道路扬尘PM2.5中水溶性离子污染特征及来源

为研究天津市高校道路扬尘PM_2.5中水溶性离子的污染特征、来源及校内外差异,于2018年7—8月采集天津市9所高校道路扬尘样品,用离子色谱法对其中8种水溶性离子(Ca²⁺、K⁺、Mg²⁺、Na⁺、Cl^-、NH⁺₄、NO^-₃、SO₄^2-)进行分析.结果显示:①水溶性离子占PM_2.5的11.65%,PM_2.5中占比大于1%的离子有Ca²⁺和SO₄^2-,其中Ca²⁺最多,占到总水溶性无机离子的65.75%;②入校道路离子含量(12.76%)稍高于校内道路(11.11%),其中8种离子含量的差异均无统计学意义;CE/AE(阴阳离子当量浓度比)值为9.59(远大于1),PM_2.5呈较强...     

金属离子和氧化剂对3,5-二氯酚光化学降解的影响

在实验条件下 ,Fe2 +、KCl O3、KCl O4 、KBr O3、KIO4 对 3 ,5 -二氯酚光化学降解起加速作用 ,且随其浓度增大 ,加速作用也在增强。KIO4 的加速作用比较强。光照时 ,KIO4 +Mn2 +对 3 ,5 -二氯酚光化学降解的加速作用非常显著。无光照时 ,当 KMn O4 浓度增加时 ,3 ,5 -二氯酚被迅速氧化 ;KIO4 +Mn2 + /Fe2 + 能够使 3 ,5 -二氯酚发生化学降解 ,尤其是 KIO4 +Mn2 + 的作用。     

宿迁市PM2.5中水溶性无机离子的季节特征和来源分析

为了研究宿迁市PM_2.5中水溶性无机离子的季节特征和来源,于2017年5月至2018年1月在宿迁市水汽通道上的3个监测点位采集了171份PM_2.5样品,分析了PM_2.5质量浓度以及9种水溶性无机离子含量.结果表明,宿迁市PM_2.5中水溶性无机离子的年均浓度为(44.08±34.61)μg·m^-3,占PM_2.5质量的41.8%, 9种水溶性离子浓度大小排序为ρ(NO^-₃)>ρ(SO₄^2-)>ρ(NH⁺₄)>ρ(Cl^-)>ρ(Na⁺)>ρ(Ca²⁺)>ρ(K⁺)>ρ(F^-)>ρ(Mg²⁺),其中NO^-₃、 SO...     

重庆市大气TSP中水溶性无机离子的化学特征

于2001至2002年在重庆市7个采样点采集了TSP,进行了水溶性无机离子分析。结果发现,SO42-离子浓度最高,其浓度范围为6.32~20.96μg/m3;Ca2 次之,其浓度范围0.78~7.47μg/m3;SO42-、NO3-和NH4 三种离子占TSP质量的8.05%~20.96%。Ca2 、K 与SO42-和NO3-都有很好的相关性,[NO3-]/[SO42-]比值较低(均值为0.4),说明重庆市区普遍使用含硫燃煤。SO42-浓度冬季最高,主要与冬季燃煤的消耗增大有关,NO3-季节明显,与NO3-的形成环境温度密切相关。水溶性无机离子质量浓度有较明显的区域差异,中心城区采样点离子质量浓度高于距离中心城区较远的采样点。     

南京江北新区冬季PM2.5中化学组分的昼夜变化特征及其来源解析

为更好地了解南京江北新区大气气溶胶中水溶性离子的昼夜变化特征,冬季连续采集了2个月的PM_2.5样品,研究其水溶性离子昼夜变化特征及来源解析.结果表明,观测期间水溶性离子质量浓度变化范围为17. 07～168. 43μg·m^-3,均值为(59. 01±30. 75)μg·m^-3,且白天的水溶性离子平均质量浓度高于夜晚. NO₃^-和NH₄⁺的浓度占离子总浓度的比值在夜晚偏高,而SO₄^2-和Cl^-则在白天偏高. SO₄^2-、NO₃^-和NH₄⁺(SNA)是南京市PM_2.5中最重要的水溶性离子,其质量浓度在污染天要高于清洁天.白天和夜晚的阴阳离子平衡比值(AE/CE)大于1,说明PM_2.5呈酸性.相关性分析...     

电镀废水中硫氰酸根离子含量的自动电位滴定

研究了用自动电位滴定测定硫氰酸根离子的条件和方法。实验结果表明,选用银电极为指示电极,217型双液接电极为参比电极,在硝酸介质中滴定硫氰酸根离子,方法具有高选择性; 应用于电镀废水分析,方法简便快捷,在4min内能打印出分析结果。     

Calcium alginate accelerates elimination of environmental lead in preschool children

Environmental lead poses a serious threat for public health, particularly, for children. The use of substances with metal-binding properties, such as natural alginates, may be a potentially effective method for elimination of toxic metal ions from human body. In present study, effect of calcium alginate isolated from brown algae on distribution of the lead ions in preschool children was investigated. In the beginning of the study, lead concentration in urine, feces, and hair was determined. Then these children were administered a dietary supplement containing calcium alginate for four weeks. The results showed that all children participated in the study had a high baseline median lead level in urine (1.1 µg/L), feces (4.6 µg/g), and hair (5.0 µg/g). Administration of calcium alginate resulted in twofold increase of the urine lead level within two weeks from the start of the treatment. At the end of alginate administration, significant decrease of lead concentration in hair was registered. These results suggest that calcium alginate can potentially prevent accumulation of the lead ions in the body and may be used as an active agent for elimination of this toxic metal from human body.     

Dissolution of different zinc salts and Zn uptake by Sedum alfredii and maize in mono- and co-cropping under hydroponic culture

Previous soil pot and field experiments demonstrated that co-cropping the hyperaccumulator Sedum alfredii with maize increased Zn phytoextraction by S. alfredii and decreased Zn uptake by maize shoots. This hydroponic experiment was conducted to investigate whether the facilitation of Zn phytoextraction by S. alfredii resulted from improved dissolution in this co-cropping system and its relation to root exudates. S. alfredii and maize were mono-and co-cropped (without a root barrier) in nutrient solution spiked with four Zn compounds, ZnS, ZnO, Zn3(PO4)2 and 5ZnO·2CO3·4H2O (represented as ZnCO3 ) at 1000 mg/L Zn for 15 days without renewal of nutrient solution after pre-culture. The root exudates were collected under incomplete sterilization and analyzed. The results indicated that the difference in Zn salts had a greater influence on the Zn concentration in maize than for S. alfredii, varying from 210-2603 mg/kg for maize shoots and 6445-12476 mg/kg for S. alfredii in the same order: ZnCO3 > ZnO >Zn3(PO4)2 > ZnS. For the four kinds of Zn sources in this experiment, co-cropping with maize did not improve Zn phytoextraction by S. alfredii. In most cases, compared to co-cropped and mono-cropped maize, mono-cropped S. alfredii resulted in the highest Zn2+ concentration in the remaining nutrient solution, and also had a higher total concentration of low molecular weight organic acids (LMWOA) and lower pH of root exudation. Root exudates did partly influence Zn hyperaccumulation in S. alfredii.