Recent progress in the identification and determination of freshwater phytoplankton in the natural environment

The biomass of the phytoplankton and its composition is one of the most important factors in water quality control. Determination of the phytoplankton assemblage is usually done by microscopic analysis (Utermöhl's method). Quantitative estimations of the biovolume, by cell counting and cell size measurements, are time-consuming and normally are not done in routine water quality control. Several alternatives have been tried: computer-based image analysis, spectral fluorescence signatures, flow cytometry and pigment fingerprinting aided by high performance liquid chromatography (HPLC). The latter method is based on the fact that each major algal group of taxa contains a specific carotenoid which can be used for identification and relative quantification of the taxa in the total assemblage. This article gives a brief comparative introduction to the different techniques available and presents some recent results obtained by HPLC-based pigment fingerprinting, applied to three lakes of different trophic status. The results show that this technique yields reliable results from different lake types and is a powerful tool for studying the distribution pattern of the phytoplankton community in relation to water depth. However, some restrictions should be taken into account for the interpretation of routine data

Prediction of the number of cloud droplets in the ECHAM GCM

In this paper a prognostic equation for the number of cloud droplets (CDNC) is introduced into the ECHAM general circulation model. The initial CDNC is based on the mechanistic model of Chuang and Penner [1995], providing a more realistical prediction of CDNC than the empirical method previously used. Cloud droplet nucleation is parameterized as a function of total aerosol number concentration, updraft velocity, and a shape parameter, which takes the aerosol composition and size distribution into account. The total number of aerosol particles is obtained as the sum of marine sulfate aerosols produced from dimethyl sulfide, hydrophylic organic and black carbon, submicron dust, and sea-salt aerosols. Anthropogenic sulfate aerosols only add mass to the preexisting aerosols but do not form new particles. The simulated annual mean liquid water path, column CDNC, and effective radius agree well with observations, as does the frequency distributions of column CDNC for clouds over oceans and the variations of cloud optical depth with effective radius

Elastic scattering of intermediate-energy electrons from C_(60) molecules

Experimental and calculated differential cross sections for elastic scattering of electrons by C_(60) molecules at collision energies of 100 to 500 eV are reported. The elastic differential cross sections were measured in a standard crossed-beam apparatus, while the calculations were performed employing the Schwinger multichannel technique at the static-exchange level. Diffraction effects, some due to the overall spherical-cage structure and some to scattering by individual C atoms, are observed in both the measured and calculated cross sections

Private Schools in Germany: Attendance up, but Not Among the Children of Less Educated Parents

The percentage of children attending private school in Germany has increased sharply in recent years. According to data of the German Socio-Economic Panel (SOEP), 7% of all students now attend private school. The SOEP, which contains a range of household data, shows that the children of parents with a university entry degree ("Abitur") are more likely to attend private school than those with less educated parents. This trend has become more pronounced in recent years: between 1997 and 2007, the percentage of students with better-educated parents attending private school increased by 77%. By contrast, the corresponding increase for students with less-educated parents was only 12%. Multivariate analyses demonstrate that increasing selection in favor of better-educated groups is particularly evident at the secondary school level. At the primary school level, full-time employment of the mother and regional factors significantly increase the chances of private school attendance. Educational policy should focus on preventing children from better-educated groups from leaving the public school system. If competition among schools is to be encouraged as a matter of policy, efforts should also be made to ensure less educated families consider sending their children to private schools.Private schools, Selection

Modelling mid-Pliocene climate with COSMOS

In this manuscript we describe the experimental procedure employed at the Alfred Wegener Institute in Germany in the preparation of the simulations for the Pliocene Model Intercomparison Project (PlioMIP). We present a description of the utilized Community Earth System Models (COSMOS, version: COSMOS-landveg r2413, 2009) and document the procedures that we applied to transfer the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) Project mid-Pliocene reconstruction into model forcing fields. The model setup and spin-up procedure are described for both the paleo- and preindustrial (PI) time slices of PlioMIP experiments 1 and 2, and general results that depict the performance of our model setup for mid-Pliocene conditions are presented. The mid-Pliocene, as simulated with our COSMOS setup and PRISM boundary conditions, is both warmer and wetter in the global mean than the PI. The globally averaged annual mean surface air temperature in the mid-Pliocene standalone atmosphere (fully coupled atmosphere-ocean) simulation is 17.35 °C (17.82 °C), which implies a warming of 2.23 °C (3.40 °C) relative to the respective PI control simulation

Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM

The double-moment cloud microphysics scheme from ECHAM4 has been coupled to the size-resolved aerosol scheme ECHAM5-HAM. ECHAM5-HAM predicts the aerosol mass and number concentrations and the aerosol mixing state. This results in a much better agreement with observed vertical profiles of the black carbon and aerosol mass mixing ratios than with the previous version ECHAM4, where only the different aerosol mass mixing ratios were predicted. Also, the simulated liquid, ice and total water content and the cloud droplet and ice crystal number concentrations as a function of temperature in stratiform mixed-phase clouds between 0 and –35°C agree much better with aircraft observations in the ECHAM5 simulations. ECHAM5 performs better because more realistic aerosol concentrations are available for cloud droplet nucleation and because the Bergeron-Findeisen process is parameterized as being more efficient. The total anthropogenic aerosol effect includes the direct, semi-direct and indirect effects and is defined as the difference in the top-of-the-atmosphere net radiation between present-day and pre-industrial times. It amounts to –1.8 W m^−2 in ECHAM5, when a relative humidity dependent cloud cover scheme and present-day aerosol emissions representative for the year 2000 are used. It is larger when either a statistical cloud cover scheme or a different aerosol emission inventory are employed

Why the oxygen isotopic composition of sea water changes with time

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94773/1/grl4282.pd

Non‐linear mixing effects on mass‐47 CO2 clumped isotope thermometry: Patterns and implications

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/110849/1/rcm7175.pd

Polychlorinated biphenyls in air and water of the North Atlantic and Arctic Ocean.

Air and seawater samples were collected on board the R/V Polarstern during a scientific expedition from Germany to the Arctic Ocean during June–August 2004. The air data show a strong decline with latitude with the highest polychlorinated biphenyl (PCB) concentrations in Europe and the lowest in the Arctic. ΣICES PCBs in air range from 100 pg m−3 near Norway to 0.8 pg m−3 in the Arctic. A comparison with other data from previous and ongoing land-based air measurements in the Arctic region suggests no clear temporal decline of PCBs in the European Arctic since the mid-1990s. Dissolved concentrations of Σ6PCBs (28/31, 52, 101, 118, 138, 153) in surface seawater were <1 pg L−1. Dominant PCBs in seawater were 28/31 and 52 (0.1–0.44 pg L−1), with PCBs 101, 118, and 138 < 0.1 pg L−1. In seawater, PCB 52 displayed the highest concentrations in the northernmost samples, while PCBs 101, 118, and 138 showed slightly decreasing trends with increasing latitude. Fractionation was observed for PCBs in seawater with the relative abundance of PCBs 28 and 52 increasing and that of the heavier congeners decreasing with latitude. However, in air only 15–20% of the variability of atmospheric PCBs can be explained by temperature. Owing to large uncertainties in the Henry's Law constant (HLC) values, fugacity quotients for PCBs were estimated using different HLCs reported in the literature. These indicate that on average, deposition dominates over volatilization for PCBs in the Arctic region with a strong increase in the middle of the transect near the marginal ice zone (78–79°N). The increase in fugacity ratio is mainly caused by an increase in air concentration in this region (possibly indirectly caused by ice melting being a source of PCBs to the atmosphere)