Antimony derived from brake linings in roadside soils, road run-off, and affected streams

锑（Sb）及其化合物被国家和国际环境主管部门（如世卫组织、美国环保署、欧洲共同体理事会）视为具有致癌潜力的高度优先关注的污染物。然而，这种半金属被添加到制动衬片的摩擦材料中，并在制动过程中由于磨损而释放到环境中。本研究的目标是：(1)获得全面表征的路边土壤中总锑的空间分布模式的详细信息，以及(2)提供对锑的流动性和物种形成（三价锑与五价锑）及其空间分布模式的更好理解。除了用强矿物质酸微波消解法测定总锑外，还将采用连续提取程序来评估锑的流动性和生物利用度。该程序包括测定弱酸溶性、可还原性、可氧化性和残留部分。为了测定Sb（III）和Sb(V)，必须从样品基质中可靠地定量提取Sb，而不使其物种降解或转化，但仍具有代表性的提取效率。我们将应用和调整已经测试的提取方法，以更广泛的范围和变化的土壤样品，以开发较少的基质依赖程序。此外，还将研究（iii）道路径流中锑的形态和大小分异，以及（iv）排放的道路径流对排水流中锑的形态和大小分异的影响。pH、离子强度、氧化还原电位、温度和溶解氧等水质参数的变化对水生系统中金属形态的形成有影响。我们将通过在降雨期间的道路径流中进行物种形成和大小分异，以及在道路径流出口下游的排水系统中进行长期变化来研究这些影响。粒径分馏将提供更多关于Sb在水生系统中结合形式的信息。已知Sb主要存在于低分子质量（LMM）部分。这是非常值得关注的，因为LMM物种被认为比颗粒相关物种更具生物可利用性。然而，这两种分析方法从未在路边径流及其受影响的排水系统中进行过。所有这些目标都有一个共同的目的：更好地了解路边土壤和相关排水系统中由制动衬里产生的锑是如何存在的。锑在环境样品中的分布对毒性效应的评价至关重要，因为锑的毒性取决于其氧化态。

Antimony (Sb) and its compounds are considered as a pollutant of high priority interest by national and international environmental authorities (e.g., WHO, US E.P.A., Council of the European Communities) as they have carcinogenic potential. Nevertheless, this semimetal is added to friction material in brake linings and released into the environment due to abrasion during the braking process. The objectives of this proposal are (i) to yield detailed information about the spatial distribution patterns of total Sb in thoroughly characterized roadside soils, and (ii) to provide an improved understanding of Sb's mobility and speciation (tri- versus pentavalent Sb) and its spatial distribution patterns in those. Besides the determination of total Sb by microwave digestion using strong mineral acids, a sequential extraction procedure will be applied to assess the mobility and bioavailability of Sb. The procedure includes the determination of the weak acid-soluble, reducible, oxidizable, and residual fractions. To determine Sb(III) and Sb(V), a reliable quantitative extraction of Sb from the sample matrix must be applied without any degradation or transformation of its species, but still with representative extraction efficiency. We will apply and adjust already tested extraction methods to a wider range and variation of soil samples in order to develop a less matrix-dependent procedure. Moreover, the (iii) speciation and size fractionation of Sb in road run-off, and (iv) the effects of discharged road run-off on the speciation and size fractionation of Sb in a drainage stream will be investigated. Variations in water quality parameter such as pH, ionic strength, redox potential, temperature, and dissolved oxygen have an influence on metal speciation in aquatic systems. We will study these effects by conducting speciation and size fractionation in both road run-offs during rain events, and long-term variations in a drainage system downstream of an outlet of road run-off. Size fractionation will provide more information about binding forms of Sb in aquatic systems. It is known that Sb mainly remains in the low molecular mass (LMM) fraction. This is of great concern, as LMM species are believed to be more bioavailable than particle-associated species. Nevertheless, both analytical approaches have never been conducted in roadside run-off and its affected drainage system. All these objectives share a common purpose: to provide a better understanding of how brake-lining-derived Sb is present in roadside soils and related drainage systems. Distribution of Sb species in environmental samples is crucial for the evaluation of toxic effects, since Sb toxicity depends on its oxidation state.