Humic substances. Part III. sorptive interactions with environmental chemicals†

The formation of covalent binding to DNA of a carcinogen is now widely accepted to represent a classical mechanism of tumour induction in mammals. This mechanism does not operate with metals since no covalent binding of these agents to DNA does occur. Nevertheless, somatic mutations as typical consequences of DNA‐damage have been reported to be induced by metals in various model systems. Beside DNA‐alkylation such damages can be caused by changes in the conformation of DNA or in the fidelity of DNA‐repair. The activity of the repair enzymes DNA‐polymerases is indeed impaired by many metal ions at least in vitro. It is not yet established whether these mechanisms are also important in the intact mammalian organism. Much evidence has accumulated during the last years that a disturbance of the balance of cations and especially metal ions represents another possible mechanism of tumour induction. The tumours found with high doses of chelating agents such as nitrilo‐triacetic acid (NTA) have to be discussed in this context. Since most—if not—all of the speculative mechanisms of metal carcinogenesis resemble classical pharmacological reactions the existence of a threshold level is likely. So metal carcinogenesis will not be a problem of the environmental contamination at trace levels but a problem of occupational medicine.     

苯胺在铂电极上电解特征的研究

采用循环伏安法考察了苯胺在铂电极上不同浓度、pH值和不同扫描速率等条件下的电化学反应特性。结果表明:在酸性条件下出现明显的氧化峰而中性和碱性条件下没有;在循环初期只有1个氧化峰,峰电势Ep≈1.0V,随着扫描的进行出现2个氧化峰,Ep≈1.0V,0.5V。     

Distribution of Platinum group elements in road dust in Beijing metropolitan area, China

Dust samples collected from the Beijing metropolitan area (China) were evaluated to determine the distribution and the concentration of platinum group elements (PGEs). The dust particles that were smaller than 100 mesh size fraction (150 μm) were analyzed after aqua regia digestion. Concentrations[RL2] of Pt, Rh, and Pd were found to be between 3.96 and 356.3 ng/g, 2.76 and 97.11 ng/g, and 0.1 and 124.9 ng/g, respectively, in the urban areas of Beijing, whereas for the background samples collected from the suburbs of Beijing, the concentration of Pt, Pd, and Rh were very low and ranged from 0.1 to 0.9 ng/g, 0.5 to 1.4 ng/g, and 0.8 to 2.2 ng/g, respectively. The[RL3] distributions of PGEs in road dust were an accurate reflection of the levels of pollution and were found to match with the local traffic conditions. A strong positive correlation was established among all the elements found in road dust. This suggests that emissions of abraded fragments from vehicle exhausts may be the source of the high concentration of Pt, Rh, and Pd in road dust along the main roads of Beijing.     

道路灰尘PGEs时间变化特征

为了研究道路灰尘铂族元素（PGEs）时间变化规律及其影响机制,以上海市为研究区,共采集季节样品24个、年际样品18个.用王水消解制样,ICP-MS测定.结果表明,灰尘PGEs春、夏、秋、冬含量分别为,Rh：10.40（6.06～17.28）ng/g、11.60（5.52～20.11）ng/g、32.91（18.53～6...     

掺杂ZrO_2、TiO_2、γ－Al_2O_3对Pt、Pd／Al_2O_3燃烧

运用ＸＲＤ、ＢＥＴ、ＤＴＡ等测试技求，研究并考察了掺杂ＺｒＯ＿２、ＴｉＯ＿２、ｒ－Ａｌ＿２Ｏ＿３对Ｐｔ－Ｐｄ／Ａｌ＿２Ｏ＿３燃烧催化剂性能的影响，结果表明，ＺｒＯ＿２对Ａｌ＿２Ｏ＿３晶相的γ型转为α型有明显的抑制作用，而ＴｉＯ＿２的添入则起促进作用；高温引起催化剂活性下降的主要原因是作为第一载体的Ａｌ＿２Ｏ＿３的比表面积和孔容减少以及Ａｌ＿２Ｏ＿３晶态从γ型转为α型所造成的。     

Influence of micro-organisms on the dissolution of metallic platinum emitted by automobile catalytic converters

Platinum emitted by automotive catalyst converters mainly exists in the metallic form, which is not bioavailable. Several investigations showed that finely dispersed metallic platinum is dissolved in organic matrices to a significantly high degree [1,2]. In an exclusion experiment, observations were made as to whether the transformation of Pt(0) and other platinum compounds is mainly of a chemical nature or is influenced by micro-organisms. A previous experiment [2], concerning the interaction of several platinum compounds with a clay-like humic soil was repeated under sterile conditions to rule out the influence of micro-organisms. During the time of interaction (3–60 d), no significant differences were observed between the sterile and non-sterile modes. Thus, the dissolution of metallic platinum into soluble species, observed previously within this time period [2], seems to be mainly of a chemical nature. On leave from Liaoning University, Department of Chemistry, 110036 Shenyang, PR China     

Platinum emission rate of automobiles with catalytic converters

Inconsistent data presently available on the platinum emission rate of cars in Germany equipped with catalytic converters are evaluated. Automobile sources of Pt other than autocatalysts are quantified and found to be 1–6 orders of magnitudes lower than the Pt emissions attributed to catalytic converters. A transfer of emission rates derived from test stand experiments to more realistic street conditions reaches 0.8 μg Pt/km. In this manner, data from test stand experiments and from environmental investigations meet in the range of 0.5–0.8 μg Pt/km.     

土壤氧化还原电位测定方法的探讨与研究

是选用铂电极直接测定法来测定土壤的氧化还原电位,该方法是采用铂电极作为氧化还原电极,饱和甘汞电极作为参比电极,两者之间存在电位差的原理而测得的。通过大量的试验数据,表明该方法是简便易行的,对于一般的土壤都有实际参考价值。最后,对此过程中遇到的问题进行了深入的探讨和研究,并提出了具体解决方案。     

Pt负载的铈锆固溶体的催化性能与表征

用柠檬酸法制备了CexZr1-xO(2x=0.5～1.0)铈锆固溶体,用浸渍法分别在铈锆固溶体上负载0.5%的Pt。用热重法(TG)测试了催化剂对碳烟的催化活性,Pt/Ce0.8Zr0.2O2显示了最高的催化活性。采用比表面(BET),X-射线衍射仪(XRD)和红外仪(FTIR)对催化剂进行了测试。结果表明:催化剂催化燃烧碳烟的活性与催化剂比表面积大小有关,可能是由于Pt在比表面积大的固溶体表面分散得更好,有利于氧溢出,促进碳烟的燃烧。     

道路环境PGEs多介质累积规律

为了研究道路环境PGEs多介质累积规律,选择上海市5条道路,同步采集灰尘、土壤及植物样品,对其中铂族元素(PGEs)含量水平进行分析.结果表明,灰尘中Rh、Pd、Pt平均浓度分别为24.92、88.39、22.28 ng/g,土壤中Rh、Pd、Pt平均浓度分别为3.64、17.45、0.97 ng/g,植物中Rh、Pd、Pt平均浓度仅分别达到2.66、6.39、0.57 ng/g,灰尘PGEs浓度远高于土壤及植物,土壤与植物中Pt、Rh浓度水平较接近;道路环境PGEs分布呈现一定规律性,但与交通流量关系并不密切;路边植物对道路灰尘PGEs吸附能力表现为Pt>Pd>Rh,其中,对Pt、Pd吸附作用非常明显,对Rh几乎不存在吸附作用,路边植物对土壤PGEs的吸收能力为Pd>Rh>Pt,Pd的生物有效性最大;多介质PGEs比例值很接近或部分重合,且均在上海市道路灰尘PGEs比值范围内,反映出上海市道路环境PGEs来源相同且均来自汽车VECs.