@misc{klein_occurrence_and_2022, 
author={Klein, O., Zimmermann, T., Ebeling, A., Kruse, M., Kirchgeorg, T., Pröfrock, D.},
title={Occurrence and Temporal Variation of Technology-Critical Elements in North Sea Sediments - A Determination of Preliminary Reference Values},
year={2022},
howpublished = {journal article},
doi = {https://doi.org/10.1007/s00244-022-00929-4},
abstract = {As interest in the investigation of possible sources and environmental sinks of technology-critical elements (TCEs) continues to grow, the demand for reliable background level information of these elements in environmental matrices increases. In this study, a time series of ten years of sediment samples from two different regions of the German North Sea were analyzed for their mass fractions of Ga, Ge, Nb, In, REEs, and Ta (grain size fraction < 20 µm). Possible regional differences were investigated in order to determine preliminary reference values for these regions. Throughout the investigated time period, only minor variations in the mass fractions were observed and both regions did not show significant differences. Calculated local enrichment factors ranging from 0.6 to 2.3 for all TCEs indicate no or little pollution in the investigated areas. Consequently, reference values were calculated using two different approaches (Median + 2 median absolute deviation (M2MAD) and Tukey inner fence (TIF)). Both approaches resulted in consistent threshold values for the respective regions ranging from 158 µg kg−1 for In to 114 mg kg−1 for Ce. As none of the threshold values exceed the observed natural variation of TCEs in marine and freshwater sediments, they may be considered baseline values of the German Bight for future studies.},
note = {Online available at: \url{https://doi.org/10.1007/s00244-022-00929-4} (DOI). Klein, O.; Zimmermann, T.; Ebeling, A.; Kruse, M.; Kirchgeorg, T.; Pröfrock, D.: Occurrence and Temporal Variation of Technology-Critical Elements in North Sea Sediments - A Determination of Preliminary Reference Values. Archives of Environmental Contamination and Toxicology. 2022. vol. 82, no. 4, 481-492. DOI: 10.1007/s00244-022-00929-4}}
@misc{ebeling_analysis_of_2022, 
author={Ebeling, A., Zimmermann, T., Klein, O., Irrgeher, J., Pröfrock, D.},
title={Analysis of Seventeen Certified Water Reference Materials for Trace and Technology-Critical Elements},
year={2022},
howpublished = {journal article},
doi = {https://doi.org/10.1111/ggr.12422},
abstract = {Concentrations of elements in the aquatic environment are a key parameter for various scientific fields such as biogeochemistry, biology and environmental science. Within this context, the scientific community asks for new analytical protocols to be able to quantify more and more elements of the periodic table. Therefore, the requirements for aqueous reference materials have increased drastically. Even though a wide variety of CRMs of different water matrices are available, certified values of many elements (e.g., rare earth elements, technology-critical elements, such as Ga and In, and generally those elements which are not part of current monitoring regulations) do not yet exist. Therefore, the scientific community relies on published elemental concentrations of many CRMs provided by other researchers. Some elements of interest, such as the rare earth elements, are well studied and plenty of literature values exist. However, less studied elements, such as Ga and In, are rarely studied. In this study, an 'externally' calibrated quantification method based on an optimised online pre-concentration method, coupled with ICP-MS/MS, is used for the quantification of thirty-four elements. The method is applied to seventeen water CRMs covering freshwater, brackish water and seawater. The measured data is combined with a comprehensive literature review on non-certified values in selected water CRMs and new consensus values are suggested for various non-certified elements.},
note = {Online available at: \url{https://doi.org/10.1111/ggr.12422} (DOI). Ebeling, A.; Zimmermann, T.; Klein, O.; Irrgeher, J.; Pröfrock, D.: Analysis of Seventeen Certified Water Reference Materials for Trace and Technology-Critical Elements. Geostandards and Geoanalytical Research. 2022. vol. 46, no. 2, 351-378. DOI: 10.1111/ggr.12422}}
@misc{logemann_assessing_the_2022, 
author={Logemann, A., Reininghaus, M., Schmidt, M., Ebeling, A., Zimmermann, T., Wolschke, H., Friedrich, J., Brockmeyer, B., Pröfrock, D., Witt, G.},
title={Assessing the chemical anthropocene – Development of the legacy pollution fingerprint in the North Sea during the last century},
year={2022},
howpublished = {journal article},
doi = {https://doi.org/10.1016/j.envpol.2022.119040},
abstract = {The North Sea and its coastal zones are heavily impacted by anthropogenic activities, which has resulted in significant chemical pollution ever since the beginning of the industrialization in Europe during the 19th century. In order to assess the chemical Anthropocene, natural archives, such as sediment cores, can serve as a valuable data source to reconstruct historical emission trends and to verify the effectiveness of changing environmental legislation. In this study, we investigated 90 contaminants covering inorganic and organic pollutant groups analyzed in a set of sediment cores taken in the North Seas' main sedimentation area (Skagerrak). We thereby develop a chemical pollution fingerprint that records the constant input of pollutants over time and illustrates their continued great relevance for the present. Additionally, samples were radiometrically dated and PAH and PCB levels in porewater were determined using equilibrium passive sampling. Furthermore, we elucidated the origin of lead (Pb) contamination utilizing non-traditional stable isotopic analysis. Our results reveal three main findings: 1. for all organic contaminant groups covered (PAHs, OCPs, PCBs, PBDEs and PFASs) as well as the elements lead (Pb) and titanium (Ti), determined concentrations decreased towards more recent deposited sediment. These decreasing trends could be linked to the time of introductions of restrictions and bans and therefor our results confirm, amongst possible other factors, the effectiveness of environmental legislation by revealing a successive change in contamination levels over the decades. 2. concentration trends for ΣPAH and ΣPCB measured in porewater correspond well with the ones found in sediment which suggests that this method can be a useful expansion to traditional bulk sediment analysis to determine the biologically available pollutant fraction. 3. Arsenic (As) concentrations were higher in younger sediment layers, potentially caused by emissions of corroded warfare material disposed in the study area after WW II.},
note = {Online available at: \url{https://doi.org/10.1016/j.envpol.2022.119040} (DOI). Logemann, A.; Reininghaus, M.; Schmidt, M.; Ebeling, A.; Zimmermann, T.; Wolschke, H.; Friedrich, J.; Brockmeyer, B.; Pröfrock, D.; Witt, G.: Assessing the chemical anthropocene – Development of the legacy pollution fingerprint in the North Sea during the last century. Environmental Pollution. 2022. vol. 302, 119040. DOI: 10.1016/j.envpol.2022.119040}}
@misc{hildebrandt_a_metrologically_2020, 
author={Hildebrandt, L., von der Au, M., Zimmermann, T., Reese, A., Ludwig, J., Pröfrock, D.},
title={A metrologically traceable protocol for the quantification of trace metals in different types of microplastic},
year={2020},
howpublished = {journal article},
doi = {https://doi.org/10.1371/journal.pone.0236120},
abstract = {The presence of microplastic (MP) particles in aquatic environments raised concern about possible enrichment of organic and inorganic pollutants due to their specific surface and chemical properties. In particular the role of metals within this context is still poorly understood. Therefore, the aim of this work was to develop a fully validated acid digestion protocol for metal analysis in different polymers, which is a prerequisite to study such interactions. The proposed digestion protocol was validated using six different certified reference materials in the microplastic size range consisting of polyethylene, polypropylene, acrylonitrile butadiene styrene and polyvinyl chloride. As ICP-MS/MS enabled time-efficient, sensitive and robust analysis of 56 metals in one measurement, the method was suitable to provide mass fractions for a multitude of other elements beside the certified ones (As, Cd, Cr, Hg, Pb, Sb, Sn and Zn). Three different microwaves, different acid mixtures as well as different temperatures in combination with different hold times were tested for optimization purposes. With the exception of Cr in acrylonitrile butadiene styrene, recovery rates obtained using the optimized protocol for all six certified reference materials fell within a range from 95.9% ± 2.7% to 112% ± 7%. Subsequent optimization further enhanced both precision and recoveries ranging from 103% ± 5% to 107 ± 4% (U; k = 2 (n = 3)) for all certified metals (incl. Cr) in acrylonitrile butadiene styrene. The results clearly show the analytical challenges that come along with metal analysis in chemically resistant plastics. Addressing specific analysis tools for different sorption scenarios and processes as well as the underlying kinetics was beyond this study’s scope. However, the future application of the two recommended thoroughly validated total acid digestion protocols as a first step in the direction of harmonization of metal analysis in/on MP will enhance the significance and comparability of the generated data. It will contribute to a better understanding of the role of MP as vector for trace metals in the environment.},
note = {Online available at: \url{https://doi.org/10.1371/journal.pone.0236120} (DOI). Hildebrandt, L.; von der Au, M.; Zimmermann, T.; Reese, A.; Ludwig, J.; Pröfrock, D.: A metrologically traceable protocol for the quantification of trace metals in different types of microplastic. PLoS One. 2020. vol. 15, no. 7, e0236120. DOI: 10.1371/journal.pone.0236120}}
@misc{zimmermann_substituting_hf_2020, 
author={Zimmermann, T., von der Au, M., Reese, A., Klein, O., Hildebrandt, L., Pröfrock, D.},
title={Substituting HF by HBF4 – an optimized digestion method for multi-elemental sediment analysis via ICP-MS/MS},
year={2020},
howpublished = {journal article},
doi = {https://doi.org/10.1039/D0AY01049A},
abstract = {Determination of elemental mass fractions in sediments plays a major role in evaluating the environmental status of aquatic ecosystems. Herewith, the optimization of a new total digestion protocol and the subsequent analysis of 48 elements in different sediment reference materials (NIST SRM 2702, GBW 07313, GBW 07311 and JMC-2) based on ICP-MS/MS detection is presented. The developed method applies microwave acid digestion and utilizes HBF4 as fluoride source for silicate decomposition. Similar to established protocols based on HF, HBF4 ensures the dissolution of the silicate matrix, as well as other refractory oxides. As HBF4 is not acutely toxic; no special precautions have to be made and digests can be directly measured via ICP-MS without specific sample inlet systems, evaporation steps or the addition of e.g. H3BO3, in order to mask excess HF. Different acid mixtures with and without HBF4 were evaluated in terms of digestion efficiency based on the trace metal recovery. The optimized protocol (5 mL HNO3, 2 mL HCL, 1 mL HBF4) allows a complete dissolution of the analyzed reference materials, as well as quantitative recoveries for a wide variety of certified analytes. Low recoveries for e.g. Sr, Ba and rare earth elements due to fluoride precipitation of HF-based digestions protocols, can be avoided by the usage of HBF4 instead. Based on the usage of high purity HBF4 all relevant trace, as well as matrix elements can be analyzed with sufficiently low LOQs (0.002 μg L−1 for U up to 6.7 μg L−1 for Al). In total, 34 elements were within a recovery range of 80%–120% for all three analyzed reference materials GBW 07313, GBW 07311 and JMC-2. 14 elements were outside a recovery range of 80%–120% for at least one of the analyzed reference materials.},
note = {Online available at: \url{https://doi.org/10.1039/D0AY01049A} (DOI). Zimmermann, T.; von der Au, M.; Reese, A.; Klein, O.; Hildebrandt, L.; Pröfrock, D.: Substituting HF by HBF4 – an optimized digestion method for multi-elemental sediment analysis via ICP-MS/MS. Analytical Methods. 2020. vol. 12, no. 30, 3778-3787. DOI: 10.1039/D0AY01049A}}
@misc{reese_characterization_of_2020, 
author={Reese, A., Voigt, N., Zimmermann, T., Irrgeher, J., Proefrock, D.},
title={Characterization of alloying components in galvanic anodes as potential environmental tracers for heavy metal emissions from offshore wind structures},
year={2020},
howpublished = {journal article},
doi = {https://doi.org/10.1016/j.chemosphere.2020.127182},
abstract = {The impact of offshore constructions on the marine environment is unknown in many aspects. The application of Al- and Zn-based galvanic anodes as corrosion protection results in the continuous emission of inorganic matter (e.g. >80 kg Al-anode material per monopile foundation and year) into the marine environment. To identify tracers for emissions from offshore wind structures, anode materials (Al-based and Zn-based) were characterized for their elemental and isotopic composition. An acid digestion and analysis method for Al and Zn alloys was adapted and validated using the alloy CRMs ERM®-EB317 (AlZn6CuMgZr) and ERM®-EB602 (ZnAl4Cu1). Digests were measured for their elemental composition by ICP-MS/MS and for their Pb isotope ratios by MC ICP-MS. Ga and In were identified as potential tracers. Moreover, a combined tracer approach of the elements Al, Zn, Ga, Cd, In and Pb together with Pb isotope ratios is suggested for a reliable identification of offshore-wind-farm-induced emissions. In the Al anodes, the mass fractions were found to be >94.4% of Al, >26200 mg kg−1 of Zn, >78.5 mg kg−1 of Ga, >0.255 mg kg−1 of Cd, >143 mg kg−1 of In and >6.7 mg kg−1 of Pb. The Zn anodes showed mass fractions of >2160 mg kg−1 of Al, >94.5% of Zn, >1.31 mg kg−1 of Ga, >254 mg kg−1 of Cd, >0.019 mg kg−1 of In and >14.1 mg kg−1 of Pb. The n(208Pb)/n(206Pb) isotope ratios in Al anodes range from 2.0619 to 2.0723, whereas Zn anodes feature n(208Pb)/n(206Pb) isotope ratios ranging from 2.0927 to 2.1263.},
note = {Online available at: \url{https://doi.org/10.1016/j.chemosphere.2020.127182} (DOI). Reese, A.; Voigt, N.; Zimmermann, T.; Irrgeher, J.; Proefrock, D.: Characterization of alloying components in galvanic anodes as potential environmental tracers for heavy metal emissions from offshore wind structures. Chemosphere. 2020. vol. 257, 127182. DOI: 10.1016/j.chemosphere.2020.127182}}
@misc{zimmermann_zinc_isotopic_2020, 
author={Zimmermann, T., Mohammed, F., Reese, A., Wieser, M., Kleeberg, U., Pröfrock, D., Irrgeher, J.},
title={Zinc isotopic variation of water and surface sediments from the German Elbe River},
year={2020},
howpublished = {journal article},
doi = {https://doi.org/10.1016/j.scitotenv.2019.135219},
abstract = {Recent studies suggested the use of the isotopic composition of Zn as a possible tracer for anthropogenic Zn emissions. Nevertheless, studies mainly focused on sampling areas of a few km2 with well-characterized anthropogenic Zn emissions. In contrast, this study focused on analyzing a large sample set of water and sediment samples taken throughout the course of the Elbe River, a large, anthropogenically impacted river system located in Central Europe. The primary objective was to evaluate the use of the isotopic composition of Zn to trace anthropogenic Zn emission on a large regional scale. In total 18 water and 26 surface sediment samples were investigated, covering the complete course of over 700 km of the German Elbe between the German/Czech border and the German North Sea, including six tributaries. Stable isotope abundance ratios of Zn were assessed by multi-collector inductively coupled plasma mass spectrometry (MC ICP-MS) in water filtrates (<0.45 µm) and total digests of the sieved surface sediment fraction (<63 µm) after analyte/matrix separation using Bio-Rad AG MP-1 resin via a micro-column approach and application of a 64Zn/67Zn double spike. Measured isotopic compositions of δ66Zn/64ZnIRMM-3702 ranged from −0.10 ‰ to 0.32 ‰ for sediment samples, and from −0.51 ‰ to 0.45 ‰ for water samples. In comparison to historical data some tributaries still feature high mass fractions of anthropogenic Zn (e.g. Mulde, Triebisch) combined with δ66Zn/64ZnIRMM-3702 values higher than the lithogenic background. The dissolved δ66Zn/64ZnIRMM-3702 values showed a potential correlation with pH. Our results indicate that biogeochemical processes like absorption may play a key role in natural Zn isotopic fractionation making it difficult to distinguish between natural and anthropogenic processes.},
note = {Online available at: \url{https://doi.org/10.1016/j.scitotenv.2019.135219} (DOI). Zimmermann, T.; Mohammed, F.; Reese, A.; Wieser, M.; Kleeberg, U.; Pröfrock, D.; Irrgeher, J.: Zinc isotopic variation of water and surface sediments from the German Elbe River. Science of the Total Environment. 2020. vol. 707, 135219. DOI: 10.1016/j.scitotenv.2019.135219}}
@misc{hildebrandt_evaluation_of_2019, 
author={Hildebrandt, L., Voigt, N., Zimmermann, T., Reese, A., Proefrock, D.},
title={Evaluation of continuous flow centrifugation as an alternative technique to sample microplastic from water bodies},
year={2019},
howpublished = {journal article},
doi = {https://doi.org/10.1016/j.marenvres.2019.104768},
abstract = {The scientific and public interest regarding environmental pollution with microplastic has considerably increased within the last 15 years. Nevertheless, up to now there is no widely applied standard operation procedure for microplastic sampling, resulting in a lack of inter-study comparability. In addition, many studies on microplastic occurrences do not indicate a sound methodological validation of the applied methods and procedures. This study presents an alternative volume-reduced sampling technique to sample the entire load of suspended particulate matter including microplastic particles in natural waters, based on continuous flow centrifugation. For the lab-scale validation of the proposed instrumental setup, six different microplastic types (PE, PET, PS, PVDC, EPS and PP) were used. The particles covered a size range from 1 μm to 1 mm and a density range from 0.94 g mL−1 to 1.63 g mL−1. Recoveries ranged from 95.0% ± 2.3%–99.1% ± 0.3% for virgin powders and from 96.1% ± 0.6%–99.4% ± 0.2% (1 SD, n = 2–3) for microplastic suspended in river water for 40 days. Gravimetric and microscopic analysis of the effluent indicates efficient removal of microplastic from the suspensions. Static light scattering analysis of the microplastic suspensions prior to and after centrifugation confirmed that no change of the particle size distribution has occurred – neither through aggregation nor through size-discrimination during centrifugation. Moreover, the system was tested in the field and used twice to sample suspended particulate matter from the Elbe estuary directly on site. Based on these first lab-scale experiments, continuous flow centrifugation proves a promising technique bearing potential to alleviate drawbacks such as contamination, filter clogging and particle size-discrimination of commonly used volume-reduced microplastic sampling approaches.},
note = {Online available at: \url{https://doi.org/10.1016/j.marenvres.2019.104768} (DOI). Hildebrandt, L.; Voigt, N.; Zimmermann, T.; Reese, A.; Proefrock, D.: Evaluation of continuous flow centrifugation as an alternative technique to sample microplastic from water bodies. Marine Environmental Research. 2019. vol. 151, 104768. DOI: 10.1016/j.marenvres.2019.104768}}
@misc{reese_extreme_spatial_2019, 
author={Reese, A., Zimmermann, T., Proefrock, D., Irrgeher, J.},
title={Extreme spatial variation of Sr, Nd and Pb isotopic signatures and 48 element mass fractions in surface sediment of the Elbe River Estuary - Suitable tracers for processes in dynamic environments?},
year={2019},
howpublished = {journal article},
doi = {https://doi.org/10.1016/j.scitotenv.2019.02.401},
abstract = {This study indicates the general potential of combined element fingerprinting and isotope tracer approaches to elucidate processes in complex river systems. Furthermore, it represents an initial characterization of the catchment area of the Elbe River as basis for future studies on river and harbor management.},
note = {Online available at: \url{https://doi.org/10.1016/j.scitotenv.2019.02.401} (DOI). Reese, A.; Zimmermann, T.; Proefrock, D.; Irrgeher, J.: Extreme spatial variation of Sr, Nd and Pb isotopic signatures and 48 element mass fractions in surface sediment of the Elbe River Estuary - Suitable tracers for processes in dynamic environments?. Science of the Total Environment. 2019. vol. 668, 512-523. DOI: 10.1016/j.scitotenv.2019.02.4