The risk may not be limited to the flooding – Polluted high flood sediments pose a health threat to the unaware public

Abstract

Background Because of global climate change, extreme flood events will increase in quantity and intensity in the upcoming decades. In catchments affected by ore mining, flooding leads to the deposition of fine sediments enriched in trace metal(loid)s. Depending on their concentration, trace metal(loid)s can be a health hazard. Therefore, the exposure of the local population to flood sediments, either by ingestion (covering direct ingestion and consuming food grown on these sediments) or via inhalation of dried sediments contributing to atmospheric particulate matter, is of concern. Results The extreme flood of July 2021 deposited enormous amounts of sediment across the town of Eschweiler (western Germany), with the inundation area exceeding previously mapped extreme flood limits (HQextreme). These sediments are rich in fine material (with the < 63 µm fraction making up 32% to 96%), which either can stick to the skin and be ingested or be inhaled. They are moderately to heavily enriched in Zn>Cu>Pb>Cd>Sn compared to local background concentrations. The concentrations of Zn, Pb, Cd, Cu, and As in flood sediments exceed international trigger action values. A simple assessment of uptake reveals that the tolerable daily intake is exceeded for Pb. Despite the enrichment of other trace elements like Zn, Cu, Cd, and Sn, they presumably do not pose a risk to human well-being. However, exposure to high dust concentrations may be a health risk. Conclusions In conclusion, flood sediments, especially in catchments impacted by mining, may pose a risk to the affected public. Hence, we propose to (I) improve the flood mapping by incorporating potential pollution sources, (II) extend warning messages to incorporate specific guidance, (III) use appropriate clean-up strategies in the aftermath of such flooding events, (IV) provide medical support, and (V) clue the public and medical professionals in on this topic accordingly.

Inventory of aqueous and sediment-associated organic pollutants released by the 2021 flood in the Vicht–Inde catchment, Germany

“…2, Table 1). Alongside of the sampling, infrastructural damages, eyewitness accounts, flood marks, and distribution of over-wash deposits were documented during the field survey of this study and other studies of this special issue (e.g., [62,99,110]). To investigate the flood-related pollutant inventory based on a non-target screening, the samples collected from the study area represent four environments, each characterized by attributes influencing the release, type, and accumulation of pollutants.…”

“…All flood sediments sampled for this study are composed primarily of silt with various amounts of debris (e.g., building material and fragments, plastics, and household items, particularly in and downstream of urban areas, e.g., Fig. 1D; for grain size data see [110]-this issue. Some floodplain sediments exhibit a higher content of the sand fraction.…”

“…Well-documented examples of smaller rivers with a long history of mining-related and industrial pollution that were also affected by the 2021 floods are the Inde and the Vicht (e.g., [110]-this issue). In particular, man-made heavy metal contamination since the Medieval times has been known to pollute the Vicht and Inde catchments (e.g., [28,87,92]).…”

“…In particular, man-made heavy metal contamination since the Medieval times has been known to pollute the Vicht and Inde catchments (e.g., [28,87,92]). The 2021 flood provided unpredictable forces and prompted the remobilization of old burdens and the distribution of heavy metals (Zn, Pb, Cd, Cu, and As) across the inundated floodplains and urban areas of the catchment (e.g., [62,110]-this issue). In addition, organic contaminants in the aqueous phase or associated with flood sediments have been released (through destruction or flooding), remobilized, and spread across the catchment areas (e.g., [62]).…”

Evaluation of the high-energy flood of mid-July 2021 as a morphologic driver in the anthropogenically developed Ahr Valley, Germany, in interaction with infrastructures

“…Heavy rainfall events and resulting riverine flooding are expected to occur more often with climate change [16,34]. These events also tend to bring excess mud deposits to the riverbed [32,34], potentially containing pollutants [35][36][37] and leading to riverbed clogging [38]. Furthermore, excess mud deposition and erosion hotspots can lead to stagnant water pools on floodplains which potentially require the attention of watercourse maintenance.…”