Calibration of tracer concentration measurement and results

A reliable assessment of relevant substance flows is very important for environmental risk assessments and efficiency analysis of measures to reduce or avoid emissions of micropollutants like drugs to water systems. Accordingly, a detailed preparation of monitoring campaigns should include an accuracy check for the sampling configuration to prove the reliability of the monitoring results and the subsequent data processing. The accuracy of substance flow analyses is expected to be particularly weak for substances having high short-term variations of concentrations in sewage. This is especially the case linked to the observation of substance flows close to source in waste water systems. The verification of a monitoring configuration in a hospital sewer in Luxembourg is in the centre of interest of the case study presented here. A tracer test in the sewer system under observation is an essential element of the suggested accuracy check and provides valuable information for an uncertainty analysis. The results illustrate the importance of accuracy checks as an essential element of the preparation of monitoring campaigns. Moreover the study shows that continuous flow proportional sampling enables a representative observation of short-term peak loads of the iodinated x-ray contrast media iobitridol close to source.

Calibration and application of B/Ca, Cd/Ca, and d11B in Neogloboquadrina pachyderma (sinistral)

The North Atlantic and Norwegian Sea are prominent sinks of atmospheric CO2 today, but their roles in the past remain poorly constrained. In this study, we attempt to use B/Ca and d11B ratios in the planktonic foraminifera Neogloboquadrina pachyderma (sinistral variety) to reconstruct subsurface water pH and pCO2 changes in the polar North Atlantic during the last deglaciation. Comparison of core-top results with nearby hydrographic data shows that B/Ca in N. pachyderma (s) is mainly controlled by seawater [B(OH)4]?/[HCO3]? with a roughly constant partition coefficient (KD =([B/Ca]of CaCO3)/([B(OH)4]-/[HCO3]-)of seawater) of 1.48 ± 0.15 * 10**-3 (2sigma), and d11B in this species is offset below d11B of the borate in seawater by 3.38 ± 0.71 per mil (2sigma). These values represent our best estimates with the sparse available hydrographic data close to our core-tops. More culturing and sediment trap work is needed to improve our understanding of boron incorporation into N. pachyderma (s). Application of a constant KD of 1.48 * 10**-3 to high resolution N. pachyderma (s) B/Ca records from two adjacent cores off Iceland shows that subsurface pCO2 at the habitat depth of N. pachyderma (s) (~50 m) generally followed the atmospheric CO2 trend but with negative offsets of ~10-50 ppmv during 19-10 ka. These B/Ca-based reconstructions are supported by independent estimates from low-resolution d11B measurements in the same cores. We also calibrate and apply Cd/Ca in N. pachyderma (s) to reconstruct nutrient levels for the same down cores. Like today's North Atlantic, past subsurface pCO2 variability off Iceland was significantly correlated with nutrient changes that might be linked to surface nutrient utilization and mixing within the upper water column. Because surface pCO2 (at 0 m water depth) is always lower than at deeper depths and if the application of a constant KD is valid, our results suggest that the polar North Atlantic has remained a CO2 sink during the calcification seasons of N. pachyderma (s) over the last deglaciation.

Contiunous surface water uncorrected and quench-corrected active fluorescence and derived chlorophyll a concentration using calibration by HPLC pigments during POLARSTERN cruise ANT-XXV/1

The relationship between phytoplankton assemblages and the associated optical properties of the water body is important for the further development of algorithms for large-scale remote sensing of phytoplankton biomass and the identification of phytoplankton functional types (PFTs), which are often representative for different biogeochemical export scenarios. Optical in-situ measurements aid in the identification of phytoplankton groups with differing pigment compositions and are widely used to validate remote sensing data. In this study we present results from an interdisciplinary cruise aboard the RV Polarstern along a north-to-south transect in the eastern Atlantic Ocean in November 2008. Phytoplankton community composition was identified using a broad set of in-situ measurements. Water samples from the surface and the depth of maximum chlorophyll concentration were analyzed by high performance liquid chromatography (HPLC), flow cytometry, spectrophotometry and microscopy. Simultaneously, the above- and underwater light field was measured by a set of high spectral resolution (hyperspectral) radiometers. An unsupervised cluster algorithm applied to the measured parameters allowed us to define bio-optical provinces, which we compared to ecological provinces proposed elsewhere in the literature. As could be expected, picophytoplankton was responsible for most of the variability of PFTs in the eastern Atlantic Ocean. Our bio-optical clusters agreed well with established provinces and thus can be used to classify areas of similar biogeography. This method has the potential to become an automated approach where satellite data could be used to identify shifting boundaries of established ecological provinces or to track exceptions from the rule to improve our understanding of the biogeochemical cycles in the ocean.

Revised calibration of the MBT-CBT paleotemperature proxy

The MBT-CBT proxy for the reconstruction of paleotemperatures and past soil pH is based on the distribution of branched glycerol dialkyl glycerol tetraether (brGDGT) membrane lipids. The Methylation of Branched Tetraether (MBT) and the Cyclisation of Branched Tetraether (CBT) indices were developed to quantify these distributions, and significant empirical relations between these indices and annual mean air temperature (MAT) and/or soil pH were found in a large data set of soils. In this study, we extended this soil dataset to 278 globally distributed surface soils. Of these soils, 26% contains all nine brGDGTs, while in 63% of the soils the seven most common brGDGTs were detected, and the latter were selected for calibration purposes. This resulted in new transfer functions for the reconstruction of pH based on the CBT index: pH = 7.90-1.97 × CBT (r**2 = 0.70; RMSE = 0.8; n = 176), as well as for MAT based on the CBT index and methylation index based on the seven most abundant GDGTs (defined as MBT'): MAT = 0.81-5.67 × CBT + 31.0 × MBT' (r**2 = 0.59; RMSE = 5.0 °C; n = 176). The new transfer function for MAT has a substantially lower correlation coefficient than the original equation (r**2 = 0.77). To investigate possible improvement of the correlation, we used our extended global surface soil dataset to statistically derive the indices that best describe the relations of brGDGT composition with MAT and soil pH. These new indices, however, resulted in only a relatively minor increase in correlation coefficients, while they cannot be explained straightforwardly by physiological mechanisms. The large scatter in the calibration cannot be fully explained by local factors or by seasonality, but MAT for soils from arid regions are generally substantially (up to 20 °C) underestimated, suggesting that absolute brGDGT-based temperature records for these areas should be interpreted with caution. The applicability of the new MBT'-CBT calibration function was tested using previously published MBT-CBT-derived paleotemperature records covering the last deglaciation in Central Africa and East Asia, the Eocene-Oligocene boundary and the Paleocene-Eocene thermal maximum. The results show that trends remain similar in all records, but that absolute temperature estimates and the amplitude of temperature changes are lower for most records, and generally in better agreement with independent proxy data.