Time filter

Source Type

Straub W.,Karlsruhe Institute of Technology | Straub W.,North Rhine Westphalia State Agency for Nature | Beheng K.D.,Karlsruhe Institute of Technology | Seifert A.,German Weather Service | And 2 more authors.
Journal of the Atmospheric Sciences | Year: 2010

Results of numerically investigated binary collisions of 32 drop pairs presented in Part I of this study are used to parameterize coalescence efficiencies and size distributions of breakup fragments of large raindrops. In contrast to the well-known results of Low and List, it is shown that coalescence efficiencies Ec can be described best by means of the Weber number We yielding Ec = exp(-1.15We). The fragment size distributions gained from our numerical investigations were parameterized by fitting normal, lognormal, and delta distributions and relating the parameters of the distribution functions to physical quantities relevant for the breakup event. Thus, this parameterization has formally a substantial similarity to the one of Low and List, although no reference is made to breakup modes such as filament, disk, and sheet. Additionally, mass conservation is guaranteed in the present approach. The parameterizations from Low and List, as well as the new parameterizations, are applied to compute a stationary size distribution (SSD) from solving the kinetic coagulation-breakup equation until a time-independent state is reached. Although with the parameterizations of Low and List, the SSD shows an often-reported three-peak structure, with the new parameterizations the second peak vanishes completely. © 2010 American Meteorological Society. Source

Diehl K.,Johannes Gutenberg University Mainz | Wurzler S.,North Rhine Westphalia State Agency for Nature
Atmospheric Environment | Year: 2010

The effects of bacteria acting as immersion ice nuclei were investigated in numerical sensitivity studies and compared to the efforts of other ice nuclei such as mineral dust and soot particles. An adiabatic air parcel model was employed simulating convective situations with different initial aerosol particle distributions. The maximum fractions of active ice nuclei were based on field measurements of the proportioning of atmospheric aerosol particle types in continental and marine air masses. Recent field measurements of bacteria concentrations in cloud water and in snow samples were used. From the concentrations in bulk samples the concentration in mean sized cloud droplets was estimated. Immersion freezing was described based on laboratory measurements to constrain the freezing fraction versus temperature. The results indicated that the effects of diminutive amounts of bacteria on ice formation in convective clouds, while being significantly less than the effects of mineral dust particles, might be comparable to the expected effects of soot particles acting as ice nuclei. It can be predicted that bacterial ice nuclei would have to be enriched by at least 10 4 times reported concentrations in cloud water in order to equate to the impact of mineral dust ice nuclei present in 20-25% of all cloud droplets. © 2010 Elsevier Ltd. Source

Fromme H.,Bavarian Health and Food Safety Authority | Fromme H.,Ludwig Maximilians University of Munich | Schutze A.,Ruhr University Bochum | Lahrz T.,Berlin Brandenburg State Laboratory | And 7 more authors.
International Journal of Hygiene and Environmental Health | Year: 2016

Plasticizers have been widely used for decades as additives in diverse applications, including consumer and building products, toys, cables, and floorings. Due to toxicological concerns and restrictions of different dialkyl ortho-phthalates, other plasticizers have been increasingly used in recent years. Therefore, di-isononyl cyclohexane-1,2-dicarboxylate (DINCH), di(2-ethylhexyl) terephthalate (DEHT), di(2-ethylhexyl) adipate (DEHA), acetyl tri-. n-butyl citrate (ATBC), and trioctyl trimellitate (TOTM) plasticizer levels in indoor air and dust samples from 63 daycare centers in Germany were measured. Moreover, the urine samples of 208 children who attend 27 of these facilities were analyzed for the presence of four DINCH metabolites.DINCH, DEHT, and DEHA were present in indoor air with median values of 108ng/m3, 20ng/m3, and 34ng/m3, respectively. Median values of 302mg/kg for DINCH, 49mg/kg for DEHA, 40mg/kg for DEHT, and 24mg/kg ATBC were found in dust. In the urine samples, the three secondary metabolites of DINCH were observed with median values (95th percentiles) of 1.7μg/l (10.0μg/l) for OH-MINCH, 1.5μg/l (8.0μg/l) for oxo-MINCH, and 1.1μg/l (6.1μg/l) for cx-MINCH. Overall, these metabolite levels are orders of magnitude lower than the current HBM I values set by the German Human Biomonitoring Commission.Using general exposure assumptions, the intake resulting from dust ingestion and inhalation is low for children. The total daily DINCH intake calculated from biomonitoring data was 0.5. μg/kg b.w. using median values and 9.8. μg/kg b.w. as the maximum value. At present, non-phthalate plasticizers, especially DINCH, can be found in considerable amounts in dust samples from daycare centers and as DINCH metabolites in the urine of children. In relation to previous studies, the concentrations of DINCH in dust and urine have an increasing time trend. Compared with tolerable daily intake values, the total daily intake of DINCH reached only 1% of its maximum value to date; however, due to its increased use, higher exposure of DINCH is expected in the future. © 2015 Elsevier GmbH. Source

Wilhelm M.,Ruhr University Bochum | Bergmann S.,North Rhine Westphalia State Agency for Nature | Dieter H.H.,Federal Environment Agency Umweltbundesamt of Germany
International Journal of Hygiene and Environmental Health | Year: 2010

After detection of perfluorooctanoate (PFOA) in drinking water at concentrations up to 0.64μg/l in Arnsberg, Sauerland, Germany, the German Drinking Water Commission (TWK) assessed perfluorinated compounds (PFCs) in drinking water and set for the first time worldwide in June 2006 a health-based guide value for safe lifelong exposure at 0.3μg/l (sum of PFOA and perfluorooctanesulfonate, PFOS). PFOA and PFOS can be effectively removed from drinking water by percolation over granular activated carbon. Additionally, recent EU-regulations require phasing out use of PFOS and ask to voluntarily reduce the one of PFOA. New and shorter-chained PFCs (C4-C7) and their mixtures are being introduced as replacements. We assume that some of these " new" compounds could be main contributors to total PFC levels in drinking water in future, especially since short-chained PFCs are difficult to remove from drinking water by common treatment techniques and also by filtration over activated carbon. The aims of the study were to summarize the data from the regularly measured PFC levels in drinking water and in the drinking water resources in North Rhine-Westphalia (NRW) for the sampling period 2008-2009, to give an overview on the general approach to assess PFC mixtures and to assess short-chained PFCs by using toxicokinetic instead of (sub)chronic data. No general increase of substitutes for PFOS and PFOA in wastewater and surface water was detected. Present findings of short-chained PFC in drinking waters in NRW were due to extended analysis and caused by other impacts. Additionally, several PFC contamination incidents in drinking water resources (groundwater and rivers) have been reported in NRW. The new approach to assess short-chained PFCs is based on a ranking of their estimated half-lives for elimination from the human body. Accordingly, we consider the following provisional health-related indication values (HRIV) as safe in drinking water for lifelong exposure: perfluorobutanoate (PFBA) 7μg/l, perfluoropentanoate (PFPA) 3μg/l, perfluorohexanoate (PFHxA) 1μg/l, perfluoroheptanoate (PFHpA) 0.3μg/l, perfluorobutanesulfonate (PFBS) 3μg/l, perfluoropentanesulfonate (PFPS) 1μg/l, perfluorohexanesulfonate (PFHxS) 0.3μg/l and perfluoroheptanesulfonate (PFHpS) 0.3μg/l. For all PFCs the long-term lowest maximal quality goal (general precautionary value, PVg) in drinking water is set to -0.1μg/l. © 2010 Elsevier GmbH. Source

Schollnhammer T.,Ruhr University Bochum | Schollnhammer T.,North Rhine Westphalia State Agency for Nature | Hebbinghaus H.,North Rhine Westphalia State Agency for Nature | Wurzler S.,North Rhine Westphalia State Agency for Nature | Schulz T.,North Rhine Westphalia State Agency for Nature
Meteorologische Zeitschrift | Year: 2014

Road traffic is one of the main causes of poor air quality in European cities. Electric vehicles (EV) are often presented as climate friendly and as a solution for air quality problems in cities. The aim of this study is to investigate how much of this claim is true and to find out the necessary shares of electric vehicles of different types needed to solve air quality problems in street canyons. For example, the German government has formulated the ambitious goal of increasing the amount of electric vehicles in Germany to 1 million in 2020 and 6 million in 2030. Will this improve the air quality significantly? The focus of the present study is the air quality in street canyons, with a focus on PM10 and NO2 concentrations. We concentrate our investigation on road traffic, taking the fleet composition into account. A sensitivity study with a dispersion model was carried out for two street canyons in North Rhine-Westphalia, typical for moderately polluted street canyons in European cities. It is shown that the reduction potential is larger for NO2 than for PM10. The necessary share of electric vehicles to comply with the limit values lies at about 40 % for NO2 and 100 % for PM10, respectively. Thus, the share of electric vehicles needed to comply with the limit values is far above the goal of the German government. © 2014 The authors. Source

Discover hidden collaborations