Periodic Reporting for period 2 - HypoTRAIN (Hyporheic Zone Processes – A training network for enhancing the understanding of complex physical, chemical and biological process interactions)
Reporting period: 2017-01-01 to 2018-12-31
For many parent compounds the transformation products are not identified so far. We contributed to this by developing and validating a method for the analysis of 26 parent compounds and 35 transformation products.
Sorption of molecules to the river sediments plays an important role in the attenuation of pollutants. However, for a lot of these components sorption characteristics are not fully known yet. We contributed to that by batch and column experiments to determine sorption isotherms and sorption rate constants for different micropollutants.
The degradation mechanisms of compounds with different physicochemical properties were investigated. Biodegradation was determined to be a major attenuation mechanism of most compounds while sorption and other physicochemical processes only played a minor role.
The multiple expertise of HypoTRAIN was fully exploited in two joint experiments where biogeochemical, hydrological and ecological approaches were coupled to quantify attenuation/degradation on both reach and local scales. An interactive map gives an overview on the datasets generated during the field experiments at a lowland river fed by treated wastewater in Germany:
A flume experiment which provided controlled external conditions aimed at comparing the effects of hyporheic microbial diversity and varying bedforms on reduction of pollutants (Fig. 3). Preliminary results for one micropollutant showed increased degradation in flumes with most hyporheic exchange and highest bacterial diversity.
A video describes the setup of the flume study:
Our results will be published in more than 50 peer-reviewed articles of which 14 are already published:
Furthermore, key microbial taxa associated with degradation of several organic micropollutants of interest have been identified using biological molecular techniques (qPCR, Next Generation Illumina sequencing). Their interaction with hyporheic geochemical parameters revealed that oxygen distribution directly influences the microbial guilds occupying particular HZ compartments. This in turn influences the degradation pathway of micropollutants reaching these microzones. Due to relatively low concentrations of micropollutants compared to other growth substrates, cometabolism is predictably an important biodegradation process in the HZ, compounded by an inadequate enzyme catalogue to degrade the ever-dynamic generation of new anthropogenic compounds. The data on the microbial community structure and response to micropollutants form a basis for optimization of conventional wastewater treatment and/or manipulations of receiving rivers.
We improved approaches to sample hyporheic water on extremely small vertical scales (e.g. mini-point samplers and an innovative passive sampling method). Analytical methods were advanced to quantify very low micropollutant concentrations. The development of “enantiomeric fractionation” enabled the differentiation of biodegradation processes from sorption and dilution. Furthermore, the performance of models describing and predicting hyporheic processes and the fate of pollutants was improved. At best, our results will facilitate the generation of better tools for assessing the effectiveness of restoration measures, river regulation, and the impact of climate change on hyporheic processes.