title: Monitoring of event-based mobilization of hydrophobic pollutants in rivers: calibration of turbidity as a proxy for particle facilitated transport in field and laboratory.
abstract: Transport of many pollutants in rivers is coupled to mobilization of suspended particles which typically occurs during floods. Since the amount of total suspended solids (TSS) in rivers can be monitored by turbidity measurements this may be used as a proxy for the total concentration of particle associated pollutants such as PAHs, PCBs, etc. and several heavy metals. Online turbidity measurements (e.g. by optical backscattering sensors) would then also allow for an assessment of particle and pollutant flux dynamics if once calibrated against TSS and total pollutant concentrations for a given catchment. In this study, distinct flood and thus turbidity events were sampled at high temporal resolution in three contrasting sub-catchments of the River Neckar in Southwest Germany (Ammer, Goldersbach, Steinlach) as well as in the River Neckar itself and investigated for the total amount of PAHs and TSS in water; turbidity (NTU) and grain size distributions of suspended solids were determined as well. Laboratory experiments were performed with natural river bed sediments from different locations (Ammer) to investigate PAH concentrations, TSS and turbidity during sedimentation of suspended particles under controlled conditions (yielding smaller and smaller suspended particles and TSS with time). Laboratory and field results agreed very well and showed that turbidity and TSS were linearly correlated over an extended turbidity range up to 2000 NTU for the field samples and up to 8000 NTU in lab experiments. This also holds for total PAH concentrations which can be reasonably well predicted based on turbidity measurements and TSS vs. PAHs relationships - even for high turbidity values observed during flood events (>2000 NTU). Total PAH concentrations on suspended solids were independent of grain size of suspended particles. This implies that for the rivers investigated the sorption capacity of particles did not change significantly during the observed events.
authors.affiliation: Water & Earth System Science (WESS) Competence Cluster, c/o Eberhard Karls University of Tübingen, Hölderlinstr. 12, 72074 Tübingen, Germany. Electronic address: h.ruegner@uni-tuebingen.de.
authors.forename: Hermann
authors.initials: H
authors.lastname: Rügner
authors.affiliation: Water & Earth System Science (WESS) Competence Cluster, c/o Eberhard Karls University of Tübingen, Hölderlinstr. 12, 72074 Tübingen, Germany.
authors.forename: Marc
authors.initials: M
authors.lastname: Schwientek
authors.affiliation: Center of Applied Geoscience, Eberhard Karls University of Tübingen, Hölderlinstr. 12, 72074 Tübingen, Germany.
authors.forename: Marius
authors.initials: M
authors.lastname: Egner
authors.affiliation: Water & Earth System Science (WESS) Competence Cluster, c/o Eberhard Karls University of Tübingen, Hölderlinstr. 12, 72074 Tübingen, Germany; Center of Applied Geoscience, Eberhard Karls University of Tübingen, Hölderlinstr. 12, 72074 Tübingen, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Grathwohl
mesh_terms: D004784:Environmental Monitoring / Q000379:methods*; D055868:Floods / Q000706:statistics & numerical data; D019015:Geologic Sediments / Q000737:chemistry; D057927:Hydrophobic and Hydrophilic Interactions; D008956:Models, Chemical; D011078:Polychlorinated Biphenyls / Q000032:analysis; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis; D045483:Rivers / Q000737:chemistry*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D011084:Polycyclic Aromatic Hydrocarbons; D014874:Water Pollutants, Chemical; D011078:Polychlorinated Biphenyls
keywords: Particle facilitated transport; Pollutant fluxes in rivers; Polycyclic aromatic hydrocarbons; Total suspended solids; Turbidity