Comparative evaluation of four suspended particulate matter (SPM) sampling devices and their use for monitoring SPM quality.

Representative sampling of suspended particulate matter is fundamental for assessing river sediment quality, including the distribution and physicochemical characterisation of particles at different hydrological events. This study compares time-integrated samplers and discrete sampling methods, focusing on (a) the representativeness of the different methods and (b) the comparability between the various sampling techniques. The study investigates whether different sampling devices used under the same conditions can reproduce the annual mean. Two time-integrated sampling techniques (Binnensammler floating collector (BS); self-constructed Phillips sampler (PS)) and two discrete sampling systems (continuous-flow centrifuge (CFC); hydrocyclone (HC)) were compared. The monitoring program (August 2013 to August 2014) was conducted using a 4-week sampling frequency at two different monitoring stations in the Rhine river basin. The analysis of physicochemical parameters included total organic carbon (TOC), particulate phosphorus (PP), grain size distribution (GSD), metals, and organic pollutants (PCBs, HCB, PAH). A nested analysis of variance (ANOVA) was used to evaluate the dependence of suspended matter quality parameters on the sampling method, the sampling device, and the sampling station. According to ANOVA, physical and chemical parameters as well as persistent organic pollutants are homogenous for the time-integrated samplers PS and BS. Comparing PS and the reference technique CFC, only the mean annual concentration of TOC is significantly higher for CFC (5.91%; PS, 4.53%) due to degradation processes. With the exception of TOC, Ni, and GSD, data of BS was comparable with that of CFC. Comparing CFC and HC, there are significant differences for GSD, Zn, and Ni. An analysis of the time series of GSD < 63 µm and sum of PAHs confirms the findings of the nested ANOVA, showing that HC time series display significant differences compared with the other samplers.

Influence of near-to-nature stormwater management on the local water balance using the example of an urban development area.

Near-to-nature stormwater management aims at replicating the quasi-natural local water balance and preserving the ecosystem's integrity of affected waters. Surface waters in the urban areas of Trier-Petrisberg are managed by a separate sewer system in conjunction with a complex retention system. To investigate the effect of this alternative rainwater management practice on the local water balance, a differentiated discharge and groundwater monitoring network with a high spatio-temporal measurement resolution has been implemented within the watershed. Additional information regarding the proportion and spatial distribution of discharge-generating surfaces was provided through visual interpretation of aerial photographs. As a result of this analysis, groundwater levels were found to not be significantly affected by an increase of local sealed surfaces, and the ecologically-justifiable maximum discharge in the tributary was infrequently exceeded. Regarding further building development and climate change, the hydrological load capacity of the retention basins will provide effective rainwater management, even with respect to increasing precipitation intensities and frequencies.