GcBÜK400 - Lead in the topsoil

Lead is a toxic heavy metal and is ubiquitous in the environment due to its multiple industrial uses. The input sources are not limited to the area of ore deposits (mainly lead sulfide and its oxidation minerals). Lead is also introduced into the soil through the smelting of lead, copper and zinc ores, the long-range exhaust gas pollution of motor vehicles (up to 60% of atmospheric pollution until the introduction of lead-free petrol), lead scrap recycling plants, the use of sewage sludge and compost containing heavy metals, and coal incineration plants. For unpolluted soils, a Pb content of 2 to 60 mg/kg is given depending on the initial rock. The average Pb concentration of the upper continental crust (clarke value) is 17 mg/kg, the area-related mean Pb content for the Saxon main rock types is 20 mg/kg. The rocks of Saxony have no or little geochemical specialisation with regard to lead. In the northern and northeastern part of Saxony, relatively low Pb levels occur in the upper soils above the loose sediments of the Cenozoic period (periglacian sands, gravel, loess) and the granodiorites of Lusatia. In the case of loose sediments, the Pb content increases slightly with increasing clay content. The weathered soils above the solid rocks of the Ore Mountains, Vogtland and partly the Elbe zone usually have significantly higher lead contents, which are caused by a relative enrichment in the soil starting rocks. The highest lead-contaminated area in Saxony is the Freiberg area. Due to the economically important polymetallic mineralizations (Pb-Zn-Ag), which are also relatively widespread in terms of area, there was a particularly strong Pb enrichment in the secondary rocks and consequently also in the formation of the soils over the gneiss. In addition, enormous anthropogenic pressures have arisen from the centuries-long smelting of primary ores and, more recently, from the recycling of lead-acid batteries. Particularly high Pb contents occur in the immediate vicinity of the smelter sites, including the main wind directions, in the central part of the quartz-sulphide mineralization and in the floodplains. Further areas with large-scale elevated Pb contents are mainly located in the Osterzgebirge, in an area that extends from Freiberg in a south-easterly direction to the national border in the Altenberg area and in the ore regions of the Central and Westerzgebirge, such as Seiffen, Marienberg - Pobershau, Annaberg, Schneeberg, Schwarzenberg and Pöhla. However, the proportion of Pb minerals in the ores of these regions is significantly lower. Due to the frequent socialization of Pb and As in the mineralizations, the distribution area of the elevated Pb contents in the Osterzgebirge and subordinate in the Westerzgebirge as well as in the floodplains of the Freiberger and Vereinigte Mulde is similar to that of the arsenic. The floodplain soils of the Freiberger Mulde lead extremely high lead contents from the Freiberger reservoir area, which continue into the floodplain soils of the United Mulde in northwestern Germany. The floodplains of the Elbe and the Zwickauer Mulde also have areas with higher lead contents due to geogenous or anthropogenic sources (storage sites, industry) in the catchment area. The lead content of the soils in the Freiberg area and in the floodplain soils of the Freiberger and Vereinigte Mulde exceeds the test and action values of the Federal Soil Protection and Contaminated Sites Ordinance (BBodSchV) in some cases.

铅（Lead）是一种有毒重金属，因其多领域工业用途而广泛存在于环境中。土壤中铅的输入源不限于矿床区域（主要为硫化铅及其氧化矿物）。铅还可通过以下途径进入土壤：铅、铜、锌矿石冶炼，机动车尾气的长距离大气污染（无铅汽油推广前，机动车尾气铅污染占大气总铅污染的60%），废铅回收厂，含重金属的污泥与堆肥的施用，以及燃煤焚烧设施。

对于未受污染的土壤，其Pb含量介于2~60 mg/kg之间，具体数值取决于母岩类型。上层大陆地壳的铅平均浓度为17 mg/kg（克拉克值，clarke value）；萨克森州主要岩石类型的区域平均Pb含量为20 mg/kg。萨克森州的岩石在铅元素方面不存在或仅存在极弱的地球化学分异。

在萨克森州北部与东北部地区，新生代松散沉积物（冰缘砂、砾石、黄土）之上的表层土壤，以及卢萨蒂亚地区的花岗闪长岩出露区，其Pb含量相对较低。对于松散沉积物，Pb含量随黏土占比升高而略有提升。厄尔士山脉、福格特兰以及部分易北河区的基岩之上的风化土壤，Pb含量通常显著更高，这源于原岩中铅元素的相对富集。

萨克森州铅污染最严重的区域为弗莱贝格地区。该区域拥有具有重要经济价值的多金属矿化带（Pb-Zn-Ag矿），且这类矿化带分布相对广泛，致使次生岩石中Pb元素发生显著富集，进而导致片麻岩之上发育的土壤Pb含量升高。此外，数百年的原生矿石冶炼活动，以及近年来的铅酸蓄电池回收活动，均给当地带来了极强的人为铅污染压力。冶炼厂周边区域（包括主风向影响范围）、石英硫化物矿化带中部以及漫滩地区，Pb含量尤其高。

其他存在大范围Pb含量超标的区域主要包括东厄尔士山脉，以及从弗莱贝格向东南延伸至阿尔滕贝格地区国境线的区域，还有中厄尔士山脉与西厄尔士山脉的矿区，例如赛芬、马里恩贝格-波伯尔绍、安娜贝格、施内贝格、施瓦岑贝格与波赫拉地区。但这些区域矿石中的铅矿物占比显著更低。

由于矿化带中Pb与砷频繁共生，东厄尔士山脉、次要的西厄尔士山脉，以及弗莱贝格穆德河与联合穆德河漫滩地区的Pb含量超标区域分布，与砷超标区域分布高度相似。弗莱贝格穆德河的漫滩土壤Pb含量极高，其污染源来自弗莱贝格库区，该污染带还延伸至德国西北部的联合穆德河漫滩土壤中。易北河与茨维考穆德河的漫滩区域同样存在Pb含量偏高的区域，其污染源来自流域内的天然地质来源或人为活动（如存储场地、工业活动）。

弗莱贝格地区的土壤，以及弗莱贝格穆德河与联合穆德河的漫滩土壤，其Pb含量在部分点位已超出《联邦土壤保护和污染场地条例》（BBodSchV）规定的检测阈值与行动阈值。