In-situ measurement of photosynthetic oxygen production in the water column

A novel hardware device is described to determine photosynthetic and respiratory oxygen uptake and release, respectively, in organisms in their natural habitat even under the rough conditions of their marine environment. Both macroalgae and phytoplankton can be utilized and oxygen exchange can be determined in solar radiation. The chamber can be used at or above the water surface or can be lowered into the water column. The data of oxygen concentration, irradiance and temperature are constantly monitored by a laptop computer and stored in disk files. The experimental data measured in some macroalgae as well as in phytoplankton indicate that the irradiance window for positive net photosynthetic oxygen production is fairly limited under natural conditions; at too low irradiances respiration exceeds photosynthesis and at too high irradiances photosynthesis is shut down by photoinhibition, at least in species not adapted to unattenuated solar radiation.     

Dioxin-/Furan-‘Verbrennungsprofile’ in Abgasen aus Hochtemperaturprozessen

Different mechanisms operating downstream from high temperature processes lead to the formation of polychlorinated dibenzo(p) dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Independent of the level of concentration, these mechanisms lead to comparable PCDD/F patterns, as has been observed from the proportion of single congeners to the total of 17 2,3,7,8-Cl-substituted congeners or to the individual homologous groups related to the sum of the homologous tetra to octa CDD/F groups. A comparison of these so-called “combustion profiles” with the congeners Heats of Formation (HoF), as calculated via semiempirical molecular orbital methods, may provide an idea of the course of thermodynamical forced reaction.     

Defining Chlorophyll-a Reference Conditions in European Lakes

The concept of “reference conditions” describes the benchmark against which current conditions are compared when assessing the status of water bodies. In this paper we focus on the establishment of reference conditions for European lakes according to a phytoplankton biomass indicator—the concentration of chlorophyll-a. A mostly spatial approach (selection of existing lakes with no or minor human impact) was used to set the reference conditions for chlorophyll-a values, supplemented by historical data, paleolimnological investigations and modelling. The work resulted in definition of reference conditions and the boundary between “high” and “good” status for 15 main lake types and five ecoregions of Europe: Alpine, Atlantic, Central/Baltic, Mediterranean, and Northern. Additionally, empirical models were developed for estimating site-specific reference chlorophyll-a concentrations from a set of potential predictor variables. The results were recently formulated into the EU legislation, marking the first attempt in international water policy to move from chemical quality standards to ecological quality targets.     

Influence of nocturnal vertical stability on daytime chemistry: A one-dimensional model study

Nocturnal chemistry can play an important role in determining the initial morning conditions for daytime chemistry in urban areas. However, the impact on daytime O₃ levels is difficult to assess as the suppression of vertical trace gas transport leads to highly altitude dependent nocturnal chemistry, in particular with respect to the removal and conversion of nitrogen oxides (NO_x) and volatile organic compounds (VOC). One-dimensional (1-D) chemical transport model calculations for different nighttime vertical stabilities and different ozone formation regimes (i.e. NO_x- vs. VOC-sensitive) were performed assuming a 1000 m high daytime boundary layer and a growing nocturnal boundary layer reaching 200 m height at the end of the night. Exclusion of NO₃ chemistry from the model leads to daytime O₃ concentration changes from ?4% to +16% for different O₃ sensitivities. In all cases strong nocturnal vertical concentration profiles of NO_x, O₃, NO₃ and N₂O₅ and a dependence of these profiles on vertical stability were found at night. The nocturnal NO_x loss averaged over the lowest 1000 m changes by 9–24% for different vertical stabilities and ozone sensitivities. The impact of nocturnal vertical stability leads to 7–12% difference in O₃ concentration in the morning and ～0–2.5% in the afternoon.     

Fate of PCBs, PAHs and their source characteristic ratios during composting and digestion of source-separated organic waste in full-scale plants

Composting and digestion are important waste management strategies. However, the resulting products can contain significant amounts of organic pollutants such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs). In this study we followed the concentration changes of PCBs and PAHs during composting and digestion on field-scale for the first time. Concentrations of low-chlorinated PCBs increased during composting (about 30%), whereas a slight decrease was observed for the higher chlorinated congeners (about 10%). Enantiomeric fractions of atropisomeric PCBs were essentially racemic and stable over time. Levels of low-molecular-weight PAHs declined during composting (50-90% reduction), whereas high-molecular-weight compounds were stable. The PCBs and PAHs concentrations did not seem to vary during digestion. Source apportionment by applying characteristic PAH ratios and molecular markers in input material did not give any clear results. Some of these parameters changed considerably during composting. Hence, their diagnostic potential for finished compost must be questioned.     

Tributylzinn auf dem Weg zu den ‘Top of the POPs’?

Two groups of pollutants established during the past years, the impact of which on the eco-system gave cause for concern and legislative reaction: Persistent Organic Pollutants (POPs) and Endocrine Disrupters. At present, only the 12 POPs (‘Dirty Dozen’) are subject to serious international bans as long as they do not belong as well to potential endocrine disrupters, such as the PCDDs/PCDFs (Polychlorinated Dibenzo(p)dioxins and furans). But there are endocrine disrupters which fulfil, the POP-criteria stated in the Stockholm Convention. The organotin compounds are part of them, especially the tributyltin (TBT), since the toxicity increases with increasing alkylation. The present investigations may contribute to the discussion on the POP-potential of TBT on the basis of the results from GfA-internal and literature findings.     

Water quantity and quality dynamics of the THC — Tuyamuyun Hydroengineering Complex — And implications for reservoir operation

Background In the Aral Sea basin, safe water resources are scarce and steadily becoming scarcer. Particularly high quality water is going to become a rare good. The object of the study was the Tuyamuyun Hydroengineering Complex (THC), a complex of artificial water reservoirs located in the lower Amu Darya River, which provides water for irrigation, industry, and drinking for the lower Amu Darya region. The focus was on operation of one of its four reservoirs, the Kaparas, which is mainly used for drinking water supply. The objective includes the investigation of impacts of conventional operation schemes on the reservoir water quality for improving drinking water quality (salinity). Basic operation rules for Kaparas, which can be considered as representative for conventional dam operation under dry year conditions, had to be identified and improved operation schemes derived. Methods Existing data archives were analysed, and further data were acquired from field surveys, data processing and modelling studies. Historical data were identified, which are appropriate to determine representative schemes for the conventional operation. For the simulation of time-dependent and depth-dependent changes of reservoir salinisation, the reservoir water quality model Lac was used and linked with the THC model. Results and Discussion Modelling results for the simulation of temperature dynamics and density stratification showed a sufficient congruence with the measured temperature profiles. The conformity of measured and calculated salt concentration is basically ensured. The reservoir, which fill with higher saline water at the end of the summer, aggravates the entrainment of high saline water in the entire water column. Conclusions The current conventional operation regime mainly leads to filling the Kaparas reservoir with high saline water during the winter months. Even in the event of starting with comparable low salinity levels, the simulation demonstrates the rapid deterioration of the reservoir water quality. Under dry year conditions, the WHO standards for drinking water will be exceeded by 30% after two years, so that the impact of dry years in the context of water stress becomes visible. Recommendations and Outlook Processed data and results are now available to identify enhanced reservoir operation strategies for salinity reduction by changing the period of reservoir filling and release, as well as to initiate a detailed analysis of how water deficits in dry years may be reduced by improved operation regimes. Using adapted and enhanced operation rules for THC reservoirs, the local population within the lower Aral Sea basin might be supplied with more potable water of higher quality in future.     

A Top-Down Regional Assessment of Urban Greenhouse Gas Emissions in Europe

This paper provides an account of urban greenhouse gas (GHG) emissions from 40 countries in Europe and examines covariates of emissions levels. We use a “top-down” analysis of emissions as spatially reported in the Emission Dataset for Global Atmospheric Research supplemented by Carbon Monitoring for Action from 1153 European cities larger than 50 000 population in 2000 (comprising >81 % of the total European urban population). Urban areas are defined spatially and demographically by the Global Rural Urban Mapping Project. We compare these results with “bottom-up” carbon accounting method results for cities in the region. Our results suggest that direct (Scopes 1 and 2) GHG emissions from urban areas range between 44 and 54 % of total anthropogenic emissions for the region. While individual urban GHG footprints vary from bottom-up studies, both the mean differences and the regional energy-related GHG emission share support previous findings. Correlation analysis indicates that the urban GHG emissions in Europe are mainly influenced by population size, density, and income and not by biophysical conditions. We argue that these data and methods of analysis are best used at the regional or higher scales.     

Partitioning of persistent organic pollutants (POPs) between human serum and breast milk: A literature review

The literature was reviewed to assess the relationship between the lipid adjusted concentration in human serum and breast milk (expressed as the serum/milk ratio) of a broad range of POPs in paired samples. Thirteen studies were identified, including seven studies that reported serum/milk ratios for polychlorinated dibenzo-dioxins and -furans (PCDD/Fs), ten for polychlorinated biphenyls (PCBs), five for polybrominated diphenyl ethers (PBDEs), and five for organochlorine pesticides (OCPs). Mean serum/milk ratios ranged between 0.7 and 25 depending on the compound and congener. For PCDD/Fs, PCBs and PBDEs, a clear trend of increasing mean serum/milk ratio by increasing molar volume, hydrophobicity and number of halogen substitutes was observed. The mean serum/milk ratios reported by the 13 studies summarized here will aid comparison between human POPs exposure studies using either serum or milk samples. More studies are needed to allow a valid comparison between data obtained from analysis of breast milk and serum samples for a broader range of POPs. Furthermore such studies may shed light on compound specific factors as well as other determinants that may affect the partitioning and partition kinetics of POPs between serum and breast milk.