How polluted is the Elbe?

Germany's rivers and streams are polluted by inputs from outside sources such as industry, agriculture and sewage treatment plants. However, the type and severity of pollution changes over the course of the river - due to many sources of pollutants and because degradation processes change the substances. In a joint measurement campaign, researchers from several Helmholtz Centres now want to analyse in more detail how environmental chemicals, nano- and microplastic particles and nutrients enter the Elbe and then the sea, and in what concentrations and quantities, and how they are degraded and changed along the way. This year's Elbe cruise as part of the research initiative „MOSES“ begins at the end of June in the Czech Republic and ends in the German Bight in mid-September. From 3 to 11 July, the research vessel "Albis" from the Helmholtz Centre for Environmental Research (UFZ) will be travelling between Schmilka on the Czech-German border and Geesthacht.

The Elbe runs for 1,094 kilometres from its source in the Czech Giant Mountains to its mouth near Cuxhaven through the Czech Republic and Germany. It flows through major cities such as Dresden and Magdeburg, receives inflows from heavily polluted rivers such as the Saale, Havel and Mulde as well as countless smaller rivers, takes on discharges from sewage treatment plants and passes through farmland and meadows. This means that much of what is released into the environment in the river's catchment area ends up in the Elbe in one form or another. These include environmental chemicals, nano- and microplastic particles and nutrients. "The aim is to measure the material inputs and their concentrations from the source of the Elbe to the German Bight. We want to develop a model that takes into account the distribution and dilution of pollutants in the river in order to draw conclusions as to which processes the pollutants are subject to," says Dr Ute Weber. She heads the MOSES research initiative at the UFZ, in which nine Helmholtz research centres are analysing the consequences of extreme hydro-meteorological events on the earth and the environment.

A special feature of this year's Elbe campaign is that, in addition to the UFZ as the coordinating research institution, three other Helmholtz centres are involved, which are travelling on individual river sections and coastal areas of the North Sea with their research vessels: The Helmholtz Centre Hereon, the GEOMAR Helmholtz Centre for Ocean Research Kiel and the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). This cooperation was first tested during the MOSES dress rehearsal "Elbe 2020". "Back then, we successfully tested the cooperation between the coordinated sensor and measurement systems as well as the logistics and organisation from Schmilka to the German Bight," says Ute Weber. The deployment logistics have been continuously refined in the subsequent campaigns so that they can now be used again and again for new research objectives.

Logging pollutants along the entire course of the river
New this year is that the pollutants will be analysed for the first time along the entire gradient from the source of the Elbe to the North Sea estuary. From 27 to 29 June, the Institute of Hydrobiology of the Academy of Sciences of the Czech Republic will be sampling the approximately 370-kilometre section from the source to the Czech-German border on the Czech side. However, because the Elbe is dammed on the Czech side, unlike in Germany, no research vessel is travelling there. The water and sediment samples are therefore taken from bridges or at barrages. From the border to the Geesthacht barrage, the UFZ research vessel "Albis" will be deployed in the first two weeks of July, followed by the Hereon research vessel "Ludwig Prandtl" from Geesthacht to Cuxhaven (end of August). In addition to the "Ludwig Prandtl", the GEOMAR research vessel "Littorina" and the AWI research vessel "Uthörn II" will cover the coastal area of the North Sea at the beginning of September.

Contents of the "Elbe 2023" measurement programme
The UFZ environmental chemist Prof. Dr Werner Brack is responsible for the investigations into environmental chemicals. "We want to record and analyse a range of different organic chemicals that are dissolved in the water or bound to suspended matter downstream from the Czech Republic to the German Bight," he says. These include more than 600 substances, including pharmaceutical residues, hormonally active substances, preservatives, polyfluoroalkyl substances (PFAS), pesticides, industrial chemicals and surfactants. They are degraded, converted, overlaid by inputs from various sources or their concentrations are diluted. "The aim is to determine the inputs from agriculture, sewage treatment plants, industry and residential areas into the Elbe and thus the pollution of the river more precisely," says Werner Brack. In order to determine this so-called chemical footprint, the researchers are taking water samples - both in the Czech Republic from the banks of the Elbe and in Germany at 22 locations in the Elbe as well as from land at six inlets and eight sewage treatment plants. Using non-target analyses, the researchers also want to identify compounds in the water samples based on the molecular mass that are not already known or suspected to be pollutants in these waters. "Our aim is to determine chemical mixtures as typical pollution patterns that can be clearly assigned to sources such as agriculture, industrial operations, road traffic or settlements," says Brack. So far, this research approach has mainly been pursued in laboratory tests, but the measurement programme in the Elbe offers much more realistic conditions

UFZ environmental chemist Prof. Dr Annika Jahnke coordinates a research team focusing on the transport and distribution of nano- and microplastics and related chemicals such as plasticisers or UV stabilisers. "The main sources for the frequent occurrence of plastics in the oceans are on land, and rivers play an important role in their distribution. We suspect that many nano- and microplastic particles are transported into the North Sea by the Elbe and therefore want to investigate how the particles and associated chemicals are distributed from the source to the North Sea," she says. For the Elbe, for example, the aim is to quantify how much plastic enters the sea in this way. In addition to particle analysis, her team has selected around 150 substances for the measurement and analysis programme. "These persistent substances are potentially toxic to humans, organisms and the environment, as they are suspected of having an effect on the hormone system, for example, and tend to accumulate in living organisms," says Annika Jahnke. She is having around 30 sediment and numerous water samples taken along the Elbe and the German Bight, which will be analysed in the Helmholtz research laboratories.

As a third thematic focus, the researchers are interested in nutrients. A team coordinated by UFZ river scientist Dr Norbert Kamjunke wants to measure the concentrations of nutrients such as nitrate, phosphate or silicon as well as organic compounds such as carbohydrates and humic substances and determine the nutrient uptake by algae, which is subject to strong fluctuations over the course of the river: First, the algae grow in masses in the inland Elbe and absorb nutrients, as a result of which the concentrations of nitrate and phosphate in the water fall. The algae produce a lot of oxygen through photosynthesis and the pH value rises. "In the estuary below the Port of Hamburg, the flow rate decreases, the algae sediment and decomposition processes lead to an oxygen minimum. Liquid nutrients are released again and transported into the North Sea, where they can potentially lead to algae growth again," explains Norbert Kamjunke, who is leading the Elbe cruise on the "Albis" for the UFZ and coordinating the entire campaign. The aim of the measurements is to quantify the export of nutrients from the land into the Elbe and into the coastal waters by taking a total of 70 water and sediment samples. "We want to describe a gradient for the distribution of nutrients from the source to the sea," says the UFZ researcher. The first preliminary results for the three focal points are expected by the end of the year at the earliest.

The research initiative
MOSES stands for "Modular Observation Solutions for Earth Systems". In this initiative coordinated by the UFZ, nine research centres of the Helmholtz Association jointly developed mobile and modular observation systems between 2017 and 2021. This will enable them to investigate the effects of temporally and spatially limited dynamic events, such as extreme precipitation and runoff events or periods of drought, on the long-term development of earth and environmental systems. MOSES has been in regular operation since 2022.
Up-to-date information can be found at: http://www.moses-helmholtz.de

Article from "LABO" dated 28 June 2023