TY - JOUR A1 - Khurana, Swamini A1 - Hesse, Falk A1 - Kleidon-Hildebrandt, Anke A1 - Thullner, Martin T1 - Should we worry about surficial dynamics when assessing nutrient cycling in the groundwater? JF - Frontiers in water N2 - The fluxes of water and solutes in the subsurface compartment of the Critical Zone are temporally dynamic and it is unclear how this impacts microbial mediated nutrient cycling in the spatially heterogeneous subsurface. To investigate this, we undertook numerical modeling, simulating the transport in a wide range of spatially heterogeneous domains, and the biogeochemical transformation of organic carbon and nitrogen compounds using a complex microbial community with four (4) distinct functional groups, in water saturated subsurface compartments. We performed a comprehensive uncertainty analysis accounting for varying residence times and spatial heterogeneity. While the aggregated removal of chemical species in the domains over the entire simulation period was approximately the same as that in steady state conditions, the sub-scale temporal variation of microbial biomass and chemical discharge from a domain depended strongly on the interplay of spatial heterogeneity and temporal dynamics of the forcing. We showed that the travel time and the Damkohler number (Da) can be used to predict the temporally varying chemical discharge from a spatially heterogeneous domain. In homogeneous domains, chemical discharge in temporally dynamic conditions could be double of that in the steady state conditions while microbial biomass varied up to 75% of that in steady state conditions. In heterogeneous domains, the interquartile range of uncertainty in chemical discharge in reaction dominated systems (log(10)Da > 0) was double of that in steady state conditions. However, high heterogeneous domains resulted in outliers where chemical discharge could be as high as 10-20 times of that in steady state conditions in high flow periods. And in transport dominated systems (log(10)Da < 0), the chemical discharge could be half of that in steady state conditions in unusually low flow conditions. In conclusion, ignoring spatio-temporal heterogeneities in a numerical modeling approach may exacerbate inaccurate estimation of nutrient export and microbial biomass. The results are relevant to long-term field monitoring studies, and for homogeneous soil column-scale experiments investigating the role of temporal dynamics on microbial redox dynamics. KW - reactive transport modeling KW - spatio-temporal heterogeneity KW - uncertainty KW - geomicrobial activity KW - nutrient export Y1 - 2022 U6 - https://doi.org/10.3389/frwa.2022.780297 SN - 2624-9375 VL - 4 PB - Frontiers Media CY - Lausanne ER - TY - JOUR A1 - Barkow, Isolde S. A1 - Oswald, Sascha Eric A1 - Lensing, Hermann Josef A1 - Munz, Matthias T1 - Seasonal dynamics modifies fate of oxygen, nitrate, and organic micropollutants during bank filtration BT - temperature-dependent reactive transport modeling of field data JF - Environmental science and pollution research : official organ of the EuCheMS Division for Chemistry and the Environment, EuCheMS DCE N2 - Bank filtration is considered to improve water quality through microbially mediated degradation of pollutants and is suitable for waterworks to increase their production. In particular, aquifer temperatures and oxygen supply have a great impact on many microbial processes. To investigate the temporal and spatial behavior of selected organic micropollutants during bank filtration in dependence of relevant biogeochemical conditions, we have set up a 2D reactive transport model using MODFLOW and PHT3D under the user interface ORTI3D. The considered 160-m-long transect ranges from the surface water to a groundwater extraction well of the adjacent waterworks. For this purpose, water levels, temperatures, and chemical parameters were regularly measured in the surface water and groundwater observation wells over one and a half years. To simulate the effect of seasonal temperature variations on microbial mediated degradation, we applied an empirical temperature factor, which yields a strong reduction of the degradation rate at groundwater temperatures below 11 degrees C. Except for acesulfame, the considered organic micropollutants are substantially degraded along their subsurface flow paths with maximum degradation rates in the range of 10(-6) mol L-1 s(-1). Preferential biodegradation of phenazone, diclofenac, and valsartan was found under oxic conditions, whereas carbamazepine and sulfamethoxazole were degraded under anoxic conditions. This study highlights the influence of seasonal variations in oxygen supply and temperature on the fate of organic micropollutants in surface water infiltrating into an aquifer. KW - bank filtration KW - aerobic and anaerobic conditions KW - pharmaceuticals and KW - personal care products KW - reactive transport modeling KW - degradation Y1 - 2020 U6 - https://doi.org/10.1007/s11356-020-11002-9 SN - 0944-1344 SN - 1614-7499 VL - 28 IS - 8 SP - 9682 EP - 9700 PB - Springer CY - Heidelberg ER -