22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

Hydrological tracers for assessing transport and dissipation processes of pesticides in a model constructed wetland system

24 Sep 2019, 16:00
1h
Trade Fairs and Congress Center (FYCMA)

Trade Fairs and Congress Center (FYCMA)

Av. de José Ortega y Gasset, 201 29006 Malaga, Spain
Poster Topic 8 - Groundwater quality and pollution processes Poster with refreshments

Speaker

Elena Fernández Pascual (Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany)

Description

Constructed wetlands have become widespread for pesticide mitigation. Fate and transport of reactive compounds inside these systems involves complex physical, chemical and biological processes that are still not fully understood. Hydrological tracers have been proven to be cost-effective tools to investigate pesticide transport and associated risks in these environments. However, most studies have considered constructed wetlands as "black box" systems. Here we present a novel approach that combines the use of hydrological tracers and high vertical-resolution sampling and monitoring to evaluate pesticide transport and dissipation processes within a wetland system on a long term basis and detailed spatial scale. Three tracers with different sorptive and reactive properties (bromide (Br), uranine (UR) and sulforhodamine B (SRB)) were applied together with three selected pesticides (boscalid, penconazole and metazachlor). The influence of vegetation and alternating different hydrologic conditions on pesticide transport and dissipation were evaluated by comparing a vegetated with a non-vegetated section of the system and by alternating periods of saturation and drying, respectively. Breakthrough curves obtained at different sampling depths revealed that the solutes were not equally distributed within the constructed wetland. Pre-injection conditions, i.e., system at field capacity, probably caused heterogeneities as a result of the existence of water-filled pores in the areas adjacent to the sampling ports of the sandy layers, especially in the middle sections. This was evidenced by a delay in the arrival of the breakthrough peaks. Data also revealed that a higher mass of solutes was transported to the vegetated part of the uppermost layer. We hypothesized that the plant roots could have acted as a shortcut. The strong temporal and spatial correlation found between Br, UR and metazachlor suggested that these solutes experienced greater transport than SRB, boscalid and penconazole, which judging by their rapid decrease in their concentration mostly underwent sorption. This was later confirmed by their similar gradual increase in accumulated mass recovery at the outlet during the flushing phase. Biochemical transformation contributed to the dissipation of metazachlor, as evidenced by the measurement of its transformation products, whose peaks were detected when the aerobic conditions were promoted. This study represents a first approximation to the joint use of hydrological tracers and high vertical-resolution sampling and monitoring to study pesticide behavior inside constructed wetlands with great spatial and temporal detail. Further experiments need to be done under field conditions coupled with mathematical modeling to provide additional insights into the complex phenomena related to transport and dissipation of pollutants in wetland systems.

Primary author

Elena Fernández Pascual (Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany)

Co-authors

Marcus Bork (Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany) Birte Hensen (Institute of Sustainable and Environmental Chemistry, Leuphana University Lüneburg, Lüneburg, Germany) Prof. Jens Lange (Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany)

Presentation Materials

There are no materials yet.
Your browser is out of date!

Update your browser to view this website correctly. Update my browser now

×