Transport behavior of organic micropollutants in sandy soils – a lysimeter study

Climate change leads to increased water scarcity in many regions worldwide and thus forces many farmers to irrigate with reclaimed water (RW). Yet, due to incomplete elimination of pollutants during the treatment process, pollutants contained in the RW (e.g. organic micropollutants) can be introduced to the soil and may possibly be further transferred to groundwater and/or into eatable plants. To better understand the associated risks, observations of transport and transformation of organic micropollutants in soils is mandatory.

Lysimeter experiments were conducted from June 2021 to November 2023. Four lysimeters  with 1 m² surface area and 1 m depth were filled with sandy soil obtained from an agricultural field (two undisturbed, two disturbed). They were equipped with 9 suction cups inserted every 10 cm. During the vegetation periods, lysimeters were irrigated with RW. Additionally, RW irrigation was done as simulated aquifer recharge during winter time. Regularly, soil pore water (extracted via suction cups) and drainage water were sampled and subsequently analyzed for concentrations of fifteen organic micropollutants.

In this contribution, we exemplary discuss the results for , as two candidates of very different transport behavior.

CBZ concentrations above the limit of quantification were found solely in the depth of 10 cm depth. These findings suggest, that CBZ is either strongly sorbed and/or microbially transformed within the first few centimeters of the soil. In general, these findings are rather contradictive to findings in literature describing CBZ as a mobile substance (e.g. Ternes et al. 2007, Paz et al. 2016).

DZA showed very mobile behavior in the lysimeter in contrast to CBZ and percolated through the start (after 130 – 150 L of percolating water, depending on the lysimeter). In summer, DZA concentrations were significantly higher than those of the inflow, which we attribute to high evaporation and root water uptake combined with no DZA uptake by the plant roots. In autumn and winter, the seepage rates increased and DZA was transported towards the lower boundary.

Results of this study show that the organic micropollutants contained in typical RW may show very different transport behavior. While for some substances enhanced contamination of groundwater might be possible, others might be greatly retarded or even decayed. 

 

References

Paz, Anat, Galit Tadmor, Tomer Malchi, Jens Blotevogel, Thomas Borch, Tamara Polubesova, and Benny Chefetz. 2016. “Fate of Carbamazepine, Its Metabolites, and Lamotrigine in Soils Irrigated with Reclaimed Wastewater: Sorption, Leaching and Plant Uptake.” Chemosphere 160 (October): 22–29. https://doi.org/10.1016/j.chemosphere.2016.06.048.

Ternes, Thomas A., Matthias Bonerz, Nadine Herrmann, Bernhard Teiser, and Henrik Rasmus Andersen. 2007. “Irrigation of Treated Wastewater in Braunschweig, Germany: An Option to Remove Pharmaceuticals and Musk Fragrances.” Chemosphere 66 (5): 894–904. https://doi.org/10.1016/j.chemosphere.2006.06.035.