TY - JOUR A1 - Busch, Jan Philip A1 - Meissner, Tobias A1 - Potthoff, Annegret A1 - Oswald, Sascha T1 - Transport of carbon colloid supported nanoscale zero-valent iron in saturated porous media JF - Journal of contaminant hydrology N2 - Injection of nanoscale zero-valent iron (nZVI) has recently gained great interest as emerging technology for in-situ remediation of chlorinated organic compounds from groundwater systems. Zero-valent iron (ZVI) is able to reduce organic compounds and to render it to less harmful substances. The use of nanoscale particles instead of granular or microscale particles can increase dechlorination rates by-orders of magnitude due to its high surface area. However, classical nZVI appears to be hampered in its environmental application by its limited mobility. One approach is colloid supported transport of nZVI, where the nZVI gets transported by a Mobile colloid. In this study transport properties of activated carbon colloid supported nZVI (c-nZVI; d(50) = 2.4 mu m) are investigated in column tests using columns of 40 cm length, which were filled with porous media. A suspension was pumped through the column under different physicochemical conditions (addition of a polyanionic stabilizer and changes in pH and ionic strength). Highest observed breakthrough was 62% of the injected concentration in glass beads with addition of stabilizer. Addition of mono- and bivalent salt, e.g. more than 0.5 mM/L CaCl2, can decrease mobility and changes in pH to values below six can inhibit mobility at all. Measurements of colloid sizes and zeta potentials show changes in the mean particle size by a factor of ten and an increase of zeta potential from -62 mV to -80 mV during the transport experiment. However, results suggest potential applicability of c-nZVI under field conditions. (C) 2014 Elsevier B.V. All rights reserved. KW - Nanoscale zero-valent iron (nZVI) KW - Nanomaterial KW - Carbo-Iron (R) KW - Colloid transport KW - Mobility KW - In-situ remediation Y1 - 2014 U6 - https://doi.org/10.1016/j.jconhyd.2014.05.006 SN - 0169-7722 SN - 1873-6009 VL - 164 SP - 25 EP - 34 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Rudolph-Mohr, Nicole A1 - Vontobel, Peter A1 - Oswald, Sascha T1 - A multi-imaging approach to study the root-soil interface JF - Annals of botany N2 - Background and Aims Dynamic processes occurring at the soil-root interface crucially influence soil physical, chemical and biological properties at a local scale around the roots, and are technically challenging to capture in situ. This study presents a novel multi-imaging approach combining fluorescence and neutron radiography that is able to simultaneously monitor root growth, water content distribution, root respiration and root exudation. Methods Germinated seeds of white lupins (Lupinus albus) were planted in boron-free glass rhizotrons. After 11 d, the rhizotrons were wetted from the bottom and time series of fluorescence and neutron images were taken during the subsequent day and night cycles for 13 d. The following day (i.e. 25 d after planting) the rhizotrons were again wetted from the bottom and the measurements were repeated. Fluorescence sensor foils were attached to the inner sides of the glass and measurements of oxygen and pH were made on the basis of fluorescence intensity. The experimental set-up allowed for simultaneous fluorescence imaging and neutron radiography. Key Results The interrelated patterns of root growth and distribution in the soil, root respiration, exudation and water uptake could all be studied non-destructively and at high temporal and spatial resolution. The older parts of the root system with greater root-length density were associated with fast decreases of water content and rapid changes in oxygen concentration. pH values around the roots located in areas with low soil water content were significantly lower than the rest of the root system. Conclusions The results suggest that the combined imaging set-up developed here, incorporating fluorescence intensity measurements, is able to map important biogeochemical parameters in the soil around living plants with a spatial resolution that is sufficiently high enough to relate the patterns observed to the root system. KW - Roots KW - soil-root interaction KW - root distribution KW - Lupinus albus KW - lupin KW - pH dynamics KW - oxygen dynamics KW - soil water distribution KW - rhizosphere KW - fluorescence imaging KW - neutron radiography Y1 - 2014 U6 - https://doi.org/10.1093/aob/mcu200 SN - 0305-7364 SN - 1095-8290 VL - 114 IS - 8 SP - 1779 EP - 1787 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Villarreyes, Carlos Andres Rivera A1 - Baroni, Gabriele A1 - Oswald, Sascha T1 - Inverse modelling of cosmic-ray soil moisture for field-scale soil hydraulic parameters JF - European journal of soil science N2 - We used inverse modelling techniques and soil moisture measured by the cosmic-ray neutron sensing (CRS) to estimate root-zone soil hydraulic properties at the field scale. A HYDRUS-1D model was developed for inverse modelling and calibrated with parameter estimation software (PEST) using a global optimizer. Integral CRS measurements recorded from a sunflower farm in Germany comprised the model input. Data were transformed to soil water storage to enable direct model calibration with a HYDRUS soil-water balance. Effective properties at the CRS scale were compared against local measurements and other inversely estimated soil properties from independent soil moisture profiles. Moreover, CRS-scale soil properties were tested on the basis of how field soil moisture (vertical distribution) and soil water storage were reproduced. This framework provided good estimates of effective soil properties at the CRS scale. Simulated soil moisture at different depths at the CRS scale agreed with field observations. Moreover, simulated soil water storage at the CRS scale compared well with calculations from point-scale profiles, despite their different support volumes. The CRS-scale soil properties estimated with the inverse model were within the range of variation of properties identified from all inverse simulations at the local scale. This study demonstrates the potential of CRS for inverse estimation of soil hydraulic properties. Y1 - 2014 U6 - https://doi.org/10.1111/ejss.12162 SN - 1351-0754 SN - 1365-2389 VL - 65 IS - 6 SP - 876 EP - 886 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Busch, Jan Philip A1 - Meissner, Tobias A1 - Potthoff, Annegret A1 - Oswald, Sascha T1 - Investigations on mobility of carbon colloid supported nanoscale zero-valent iron (nZVI) in a column experiment and a laboratory 2D-aquifer test system JF - Environmental science and pollution research : official organ of the EuCheMS Division for Chemistry and the Environment, EuCheMS DCE N2 - Nanoscale zero-valent iron (nZVI) has recently gained great interest in the scientific community as in situ reagent for installation of permeable reactive barriers in aquifer systems, since nZVI is highly reactive with chlorinated compounds and may render them to harmless substances. However, nZVI has a high tendency to agglomerate and sediment; therefore it shows very limited transport ranges. One new approach to overcome the limited transport of nZVI in porous media is using a suited carrier colloid. In this study we tested mobility of a carbon colloid supported nZVI particle "Carbo-Iron Colloids" (CIC) with a mean size of 0.63 mu m in a column experiment of 40 cm length and an experiment in a two-dimensional (2D) aquifer test system with dimensions of 110x40x5 cm. Results show a breakthrough maximum of 82 % of the input concentration in the column experiment and 58 % in the 2D-aquifer test system. Detected residuals in porous media suggest a strong particle deposition in the first centimeters and few depositions in the porous media in the further travel path. Overall, this suggests a high mobility in porous media which might be a significant enhancement compared to bare or polyanionic stabilized nZVI. KW - Carbon colloid KW - Nanoscale zero-valent iron (nZVI) KW - Aquifer systems Y1 - 2014 U6 - https://doi.org/10.1007/s11356-014-3049-7 SN - 0944-1344 SN - 1614-7499 VL - 21 IS - 18 SP - 10908 EP - 10916 PB - Springer CY - Heidelberg ER -