Mercury emissions from flooded soils and sediments in Germany are an underestimated problem: challenges for reliable risk assessments and management strategies

Abstract

Abstract.Environmental pollution by mercury is a world-wide problem. Particularly floodplain ecosystems are frequently affected. One example is the Elbe River in Germany and its catchment areas; large amounts of Hg from a range of anthropogenic and geogenic sources have been accumulated in the soils of these floodplains. They serve as sink for Hg originating from the surface water of adjacent river. Today, the vastly elevated Hg contents of the floodplain soils at the Elbe River often exceed even the action values of the German Soil Conservation Law. This is especially important as Hg polluted areas at the Elbe River achieve several hundred square kilometres. Thus, authorities are coerced by law to conduct an appropriate risk assessment and to implement practical actions to eliminate or reduce environmental problems. A reliable risk assessment particularly with view to organisms (vegetation as green fodder and hay production, grazing and wild animals) to avoid the transfer of Hg into the human food chain, requires an authentic determination of Hg fluxes and their dynamics since gaseous emissions from soil to atmosphere are an important pathway of Hg. However, reliable estimates of Hg fluxes from the highly polluted floodplain soils at the Elbe River and its tributaries, and its influencing factors are scarce. For this purpose, we have developed a new method to determine mercury emissions from soils at various sites. Our objectives were i) to quantify seasonal variations of total gaseous mercury (TGM) fluxes for floodplain soils at the Elbe River, ii) to provide insights into physico-chemical processes regulating these TGM fluxes, and iii) to quantify the impacts of the controlling factors soil temperature and soil water content on Hg volatilization from a typical contaminated floodplain soil within soil microcosm experiments under various controlled temperature and moisture conditions. Our study provides insight into TGM emissions from highly Hg-polluted floodplain soils in Germany and that those emissions are an underestimated problem. Current needs for reliable risk assessments, the induced implications for authorities, and future challenges will be discussed. The presented data will contribute to a better understanding of seasonal dynamics of Hg fluxes and its controlling factors. This presentation should be of large interest for a wide international audience, such as environmental scientists and managers, applied ecologists, and authorities.

The impact of increased flooding occurrence on the mobility of potentially toxic elements in floodplain soil – A review

“…Much of the work conducted to date (see Table S1) has been undertaken in Europe, America, Canada, China, Indonesia, Australia and New Zealand. Just over half of the studies cited in Table S1 were undertaken in Germany and Belgium (52%), with a particular research effort around the River Elbe and Wupper River in Germany (Du Laing et al, 2009;Förstner, 2004;Frohne et al, 2011;Overesch et al, 2007;Rennert et al, 2017;Rinklebe et al, 2013;. However, research examining the relationship between PTEs mobility and flooding in other parts of the world that are expected to see an increase in the frequency and magnitude of flooding events, for example in Asia, Africa and India, is limited.…”

Elevated mercury concentrations in biota despite reduced sediment concentrations in a contaminated coastal area, Harboøre Tange, Denmark

“…Secondly, there might be a possibility that the divalent mercury has been reduced to elemental mercury and evaporated as such. It is known from studies on River Elbe's mercury-contaminated floodplains that divalent mercury is reduced to elemental mercury that may evaporate to the atmosphere (During et al, 2009;Rinklebe et al, 2010;Rinklebe et al, 2009;Rinklebe et al, 2013).…”