In the NFSI, the focus was on the so-called persistent organic pollutants (POPs), which are only broken down very slowly in the environment and accumulate in organisms, and are ecotoxic [18]. Although some of the organic pollutants such as polycyclic aromatic hydrocarbons can arise naturally under certain conditions (e.g., in forest fires), these occurrences are negligibly small in comparison to the technologically induced inputs. Most of the pollutants were deposited in forests through the air, or they got directly onto the forest floor as a result of the use of pesticides. In detail, it concerns the following substances:  
Polycyclic aromatic hydrocarbons (PAH) arise from incomplete combustion processes of organic substances, e.g., in power plants and by motor vehicles, but also in forest fires [19; 20; 21]. Polychlorinated biphenyls (PCB) have a wide range of technical applications, e.g., as components of plastics. They mainly reached the soil via atmospheric deposition and they can also be transported over long distances [1]. PCB were banned worldwide by the Stockholm Convention (UNEP 2001). A special group of organic pollutants are plant protection products, to which various chemical pesticides and herbicides belong. The following substance classes were examined within the framework of the NFSI: dieldrin, hexachlorobenzene (HCB), hexachlorocyclohexane (\(\alpha\)-HCH, \(\beta\)-HCH, \(\gamma\)-HCH) and dichlorophenyltrichloroethane (DDT) and its metabolites DDx (2,4\({}^{\prime}\)-DDT; 4,4\({}^{\prime}\)-DDT; 2,4\({}^{\prime}\)-DDE; 4,4\({}^{\prime}\)-DDE; 2,4\({}^{\prime}\)-DDD; 4,4\({}^{\prime}\)-DDD). Dieldrin is a pesticide that has not been used in Germany since 1971 [22]. Different sources are discussed for HCB [18]. In addition to its role as fungicide and the possible degradation product of \(\gamma\)-HCH (lindane, see below), there is also the possibility that HCB is released from chlorine-containing substances from industrial manufacturing processes and incomplete combustion processes. HCH are chemical compounds from the group of halogenated hydrocarbons. The most common is \(\gamma\)-HCH, which was used as an insecticide and is known under the name lindane. In the forest protection sector in Brandenburg, lindane preparations were used in combination with DDT applications in the early 1980s. In the former German Democratic Republic DDT was used until 1988, whereas its use in the old federal states was discontinued in 1972 [23]. The widespread use in the forests between 1982 and 1984 to combat nun moths (_Lynamtritia monacha_) and companion species (pine beauty moth (_Panolis flamnea_), European pine shoot moth (_Rhyacionia buoliana_), bark beetle (_Scolvitinae_), etc.) is particularly relevant here. The concentrations of inorganic pollutants, such as heavy metals like lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), zinc (Zn) and the metalloid arsenic (As), in the soil depends not only on the parent material and the soil-forming processes, but also on the anthropogenic inputs, especially caused by industrial emissions and car exhaust. In the humus layer and topsoil in particular, the inputs from the air can exceed the natural basic contents of the soil [17]. In many respects the NFSI sample from the state of Brandenburg is particularly suitable for an integrative study with regard to the significance of anthropogenic soil impact factors: A characteristic of this study area is that the natural geogenically determined levels of inorganic pollutants are particularly low due to the Pleistocene loose rock cover and, moreover, so far, no forest liming has been carried out in Brandenburg that would have affected the binding capacity for heavy metals [17]. Importantly, there was a high level of air pollution in the past. Particularly in southern Brandenburg high dust depositions (unfiltered fly ashes from brown coal-fired power plants) enriched the forest soils with base cations and various pollutants in the 1970s and 1980s [24; 25; 26; 27; 28; 29; 30].