Loss of subsurface particulate and truly dissolved phosphorus during various flow conditions along a tile drain-ditch-brook continuum

Nina Siebers; Jens Kruse; Yunsheng Jia; Bernd Lennartz; Stefan Koch

doi:10.1016/j.scitotenv.2023.161439

Loss of subsurface particulate and truly dissolved phosphorus during various flow conditions along a tile drain-ditch-brook continuum

Sci Total Environ. 2023 Mar 25:866:161439. doi: 10.1016/j.scitotenv.2023.161439. Epub 2023 Jan 6.

Authors

Nina Siebers¹, Jens Kruse², Yunsheng Jia³, Bernd Lennartz⁴, Stefan Koch⁴

Affiliations

¹ Institute of Bio and Geosciences-Agrosphere (IBG-3), Forschungszentrum Jülich, D-52425 Jülich, Germany. Electronic address: n.siebers@fz-juelich.de.
² Institute of Bio and Geosciences-Agrosphere (IBG-3), Forschungszentrum Jülich, D-52425 Jülich, Germany; Institute of Crop Science and Resource Conservation (INRES), Soil Science and Soil Ecology, University of Bonn, Nussallee 13, 53115 Bonn, Germany.
³ Institute of Bio and Geosciences-Agrosphere (IBG-3), Forschungszentrum Jülich, D-52425 Jülich, Germany.
⁴ Faculty of Agricultural and Environmental Sciences, University of Rostock, Justus-von-Liebig-Weg 6, D-18051 Rostock, Germany.

PMID: 36623669
DOI: 10.1016/j.scitotenv.2023.161439

Abstract

Subsurface losses of colloidal and truly dissolved phosphorus (P) from arable land can cause ecological damage to surface water. To gain deeper knowledge about subsurface particulate P transport from inland sources to brooks, we studied an artificially drained lowland catchment (1550 ha) in north-eastern Germany. We took daily samples during the winter discharge period 2019/2020 at different locations, i.e., a drain outlet, ditch, and brook, and analyzed them for total P (TP_unfiltered), particulate P >750 nm (TP_{>750 nm}), colloidal P (TP_colloids), and truly dissolved P (truly DP) during baseflow conditions and high flow events. The majority of TP_unfiltered in the tile drain, ditch, and brook was formed by TP_{>750 nm} (54 to 59 %), followed by truly DP (34 to 38 %) and a small contribution of TP_colloids (5 to 6 %). During flow events, 63 to 66 % of TP_unfiltered was present as particulate P (TP_{>750 nm} + TP_colloids), whereas during baseflow the figure was 97 to 99 %; thus, truly DP was almost negligible (1 to 3 % of TP_unfiltered) during baseflow. We also found that colloids transported in the water samples have their origin in the water-extractable nanocolloids (0.66 to 20 nm) within the C horizon, which are mainly composed of clay minerals. Along the flow path there is an agglomeration of P-bearing nanocolloids from the soil, with an increasing importance of iron(III) (hydr)oxides over clay particles. Event flow facilitated the transport of greater amounts of larger particles (>750 nm) through the soil matrix. However, the discharge did not exhaust colloid mobilization and colloidal P was exported through the tile-drainage system during the complete runoff period, even under baseflow conditions. Therefore, it is essential that the impact of rainfall intensity and pattern on particulate P discharge be considered more closely so that drainage management can be adjusted to achieve a reduced P export from agricultural land.

Keywords: Asymmetric flow field-flow fractionation; Colloid transport; Flow component separation; Lowland catchment; Phosphorus leaching.