Thomas Neumann

Hazardous concentrations of selenium in soil and groundwater in North-West India

Soil and groundwater samples were collected for bulk elemental analyses in particular for selenium (Se) concentrations from six agricultural sites located in states of Punjab and Haryana in North-West India. Toxic concentrations of Se (45-341 μg L(-1)) were present in groundwater (76 m deep) of Jainpur and Barwa villages in Punjab. Selenium enrichments were also found in top soil layers (0-15 cm) of Jainpur (2.3-11.6 mg kg(-1)) and Barwa (3.1 mg kg(-1)). Mineralogical analyses confirmed silicates and phyllosilicates as main components of these soils, also reflected by the high content of SiO(2) (40-62 wt.%), Al(2)O(3) (9-21 wt.%) and K(2)O (2.2-3.2 wt.%). Prevailing intensive irrigation practices in Punjab with Se enriched groundwater may be the cause of Se accumulation in soils. Sequential extraction revealed >50% Se bioavailability in Jainpur soils. Appearance of selenite was observed in some of the batch assays with soil slurries under reducing conditions. Although safe Se concentrations were found in Hisar, Haryana, yet high levels of As, Mo and U present in groundwater indicated its unsuitability for drinking purposes. Detailed biogeochemical studies of Se in sediments or groundwater of Punjab are not available so far; intensive investigations should be started for better understanding of the problem of Se toxicity.

Early diagenetic processes during Mn-carbonate formation: evidence from the isotopic composition of authigenic Ca-rhodochrosites of the Baltic Sea

The formation of authigenic Ca-rich rhodochrosite (ACR) in sapropelic sediments of the Gotland Basin, Baltic Sea, is governed by deepwater renewal processes whereby saline water from the North Atlantic flushes the brackish anoxic Baltic Deeps. The carbon and oxygen isotopic compositions of these Mn- carbonates suggest that ACR formation takes place just below the sediment surface and that dissolved compounds from the deepwater column, such as water and bicarbonate molecules, were incorporated in ACR during authigenesis. Porewaters near the sediment surface display 18 O values of 5.4‰ (VSMOW) and are generally depleted in 18 O, compared to the oxygen isotopic composition of water in equilibrium with Mn-carbonate solid solutions (ACR 18 O values are 4.6‰). This suggests that early burial diagenetic processes significantly modify the initial isotopic composition of water during Mn-carbonate formation. The reduction of sulfate having 18 O values of 8.4‰ accounts for a permanent enrichment of porewater 18 O and observed 18 O values at depth equal to 4.6‰. However, this process does not explain the observed disequilibrium in the oxygen isotopic composition between water and ACR close to the sediment surface where Mn-carbonate formation takes place. Based on isotopic mass balance calculations, we suggest that MnO2 with 18 O values of 8.9‰ released oxygen enriched in 18 O into the anoxic porewaters close below the sediment surface. This process should occur after oxygenation events during deepwater renewal when MnO2 accumulates at the surface of anoxic sediments. Manganese carbonates formed in these waters display 18 O values of 1.0‰ heavier than values expected solely from the initial deepwater composition. This quantitatively explains the discrepancy between paleosalinities calculated from ACR 18 O based on Mn- carbonate/water isotopic equilibrium fractionation and direct observations for the same period. Our results emphasize the important role of microbial MnO2 reduction during rhodochrosite authigenesis and suggest that Mn(II) activity, rather than alkalinity, is the limiting component for sedimentary Mn-carbonate formation. Copyright

Stable isotopes in recent sediments of Lake Arendsee, NE Germany: Response to eutrophication and remediation measures

Abstract Recent sediments of Lake Arendsee, a small eutrophic lake in NE Germany, were examined in high temporal resolution in order to investigate the applicability of stable isotopes as proxies to trace paleoenvironmental conditions. The age model of the sediment core is based on varve counting and 137Cs/210Pb dating and reveals that the sedimentary record covers the last 70 years, during which the lake has undergone major changes in productivity and eutrophication in response to nutrient loading. Since 1965, TOC, TIC, TN and TP accumulation rates in general reflect the change from oligo-/mesotrophic to eutrophic level. The isotopic compositions of autochthonous organic matter and authigenic calcite (whitings) demonstrate that carbon isotope fractionation takes place in a CO2-limited pool. In accordance with the historical limnological observations, enhanced eutrophication is reflected by δ13CTOC increases of over 3‰ from 1934 to 1985 as a result of less 12C/13C fractionation by photosynthesis during intense primary productivity. Decreasing δ13CTIC values indicate that biogenically induced calcite formation occurred during enhanced primary production accompanied by CO2 limitation. The gradual trend to more light nitrogen isotopic signatures towards the sediment surface reflects the dominance of air nitrogen fixation of cyanobacteria blooms during the last decades. The δ18OTIC distribution suggests that plankton blooms between 1934 and 1978 had shifted towards the early season with lower temperatures as a result of increasing nutrient level, which subsequently favor plankton blooms even in colder waters. Since the mid 1980s, decreasing δ13CTOC and increasing δ13CTIC values since 1985 indicate a more efficient 12C/13C fractionation during photosynthesis with no CO2 limitation. This improvement in water quality is in accordance with several remediation measures carried out since the late 1970s. Linear isotopic trends are interrupted by high TIC, TOC, TN and TP accumulation rates in the early 1970s, which can be clearly attributed to the artificial drainage of a nearby wetland carried out during that time. This event can be considered an important external source for nutrient-loaded water and particulate matter and is displayed by significantly heavier δ13CTIC and δ18OTIC values in the sedimentary record.

Land use-related chemical composition of street sediments in Beijing.

BackgroundMore than 10 million people are currently living in Beijing. This city faces severe anthropogenic air pollution caused by an intense vehicle increase (11% per year in China), coal combusting power plants, heavy industry, huge numbers of household and restaurant cookers, and domestic heating stoves. Additionally, each year dust storms are carrying particulate matter from the deserts of Gobi and Takla Makan towards Beijing, especially in spring. Other geogenic sources of particulate matter which contribute to the air pollution are bare soils, coal heaps and construction sites occurring in and around Beijing. Streets function as receptor surfaces for atmospheric dusts. Thus, street sediments consist of particles of different chemical compositions from many different sources, such as traffic, road side soils and industry.MethodsDistributions and concentrations of various chemical elements in street sediments were investigated along a rural-urban transect in Beijing, China. Chemical elements were determined with X-ray fluorescence analysis. Factor analysis was used to extract most important element sources contributing to particulate pollution along a main arterial route of the Chinese capital.Results and DiscussionThe statistical evaluation of the data by factor analysis identifies three main anthropogenic sources responsible for the contamination of Beijing street sediments. The first source is a steel factory in the western part of Beijing. From this source, Mn, Fe, and Ti were emitted into the atmosphere through chimneys and by wind from coal heaps used as the primary energy source for the factory. The second source is a combination of traffic, domestic heating and some small factories in the center of Beijing discharging Cu, Pb, Zn and Sn. Calcium and Cr characterize a third anthropogenic element source of construction materials such as concrete and mortar. Beside the anthropogenic contamination, some elements like Y, Zr, Nb, Ce, and Rb are mainly derived from natural soils and from the deserts. This is supported by mineral phase analysis, which showed a clear imprint of material in road dusts coming from the West-China deserts.ConclusionsOur results clearly show that the chemical composition of urban road dusts can be used to identify distinct sources responsible for their contamination. The study demonstrates that the chemistry of road dusts is an important monitor to assess the contamination in the urban environment. Chemical composition of street sediments in Beijing comprises the information of different sources of atmospheric particles.Recommendations and OutlookThis study is only a small contribution to the understanding of substance fluxes related to Beijing’s dust. More effort is required to assess Beijings dust fluxes, since the dust harms the living quality of the inhabitants. Especially the measurable superimposing of long scale transported dust from dry regions with the anthropogenic polluted urban dust makes investigations of Beijing’s dust scientifically valuable.

The exceptional Oder flood in summer 1997 — distribution patterns of the oder discharge in the Pomeranian Bight

The exceptional Oder flood in summer 1997 was a unique event in order to investigate the impacts on and the consequences for the ecosystem of the Baltic Sea of about 6.5 km3 additional water loaded with nutrients and contaminants and discharged within only 5 weeks. About 15 institutions participated in this investigation in both the Szczecin Lagoon and the Pomeranian Bight. The Baltic Sea Research Institute Warnemunde studied the water and nutrient inflow, the spreading of the Oder discharge, and the impact of the discharge on the ecosystem. The main topic of the presented investigations is a detailed study of the spatial and temporal spreading of the extreme river discharge in the Pomeranian Bight and the southern Baltic Sea by satellite data, ship observations and continuous buoy measurements as well as numerical modelling.

Zebra Mussel Farming in the Szczecin (Oder) Lagoon: Water-Quality Objectives and Cost-Effectiveness

The Oder (Szczecin) Lagoon in the southern Baltic Sea is a heavily eutrophicated and degraded coastal ecosystem. We applied a systems approach framework to critically evaluate whether existing water-management measures achieve waterquality objectives for the river and lagoon systems. Our simulations reveal that the existing water-quality objectives for the river and the coastal waters are not sufficiently complementary. We suggest new water-quality threshold concentrations, which are in agreement with the European Water Framework Directive, and we calculate acceptable maximum nutrient loads for the Oder River. These calculations suggest that external nutrient-load reductions in the river basin alone seem insufficient to achieve good water quality in the lagoon. A comprehensive eutrophication management approach should also include internal nutrientretention and nutrient-removal measures in the lagoon. We focus on mussel farming, i.e., that of zebra mussels, Dreissena polymorpha, because they are efficient in removing nutrients and improving water transparency in the Oder Lagoon. For this purpose, the ecosystem model ERGOM is extended by a mussel module and an economic model. The economic model describes costs and benefits of mussel cultivation depending on the the farm size. We included additional potential sources of income such as water-quality tax or emission certificates. The simulations show that mussel farming in the lagoon is a suitable supportive measure and, at a load-reduction target of 50% or more, it is a cost-efficient measure for removing nutrients and for implementing the Baltic Sea Action Plan. In the Oder Lagoon, mussel farming could potentially remove nearly 1000 t of N (70 t of P)/year, or about 2% of the present N and P loads, and it would have the additional benefit of improving water transparency.

Plasma Neutrophil Gelatinase-Associated Lipocalin Is Primarily Related to Inflammation during Sepsis: A Translational Approach

Acute kidney injury (AKI) during sepsis is common and underestimated. Plasma neutrophil gelatinase-associated lipocalin (plasma-NGAL) is discussed as new biomarker for AKI diagnosis, but during inflammation its function and diagnostic impact remain unclear. The association between plasma-NGAL and inflammatory markers in septic patients, but also in healthy controls and patients with chronic inflammation before and after either maximum exercise test or treatment with an anti-TNF therapy were investigated. In-vitro blood stimulations with IL-6, lipopolysaccharide, NGAL or its combinations were performed to investigate cause-effect-relationship. Plasma-NGAL levels were stronger associated with inflammation markers including IL-6 (Sepsis: r=0.785 P<0.001; chronic inflammation after anti-TNF: r=0.558 P<0.001), IL-8 (Sepsis: r=0.714 P<0.004; healthy controls after exercise r=0.786 P<0.028; chronic inflammation before anti-TNF: r=0.429 P<0.041) and IL-10 (healthy controls before exercise: r=0.791 P<0.028) than with kidney injury or function. Correlation to kidney injury or function was found only in septic patients (for creatinine: r= 0.906 P<0.001; for eGFR: r= -0.686 P=0.005) and in patients with rheumatic disease after anti-TNF therapy (for creatinine: r= 0.466 P<0.025). In stimulation assays with IL-6 and lipopolysaccharide plasma-NGAL was increased. Co-stimulation of lipopolysaccharide with plasma-NGAL decreased cellular injury (P<0.05) and in trend IL-10 levels (P=0.057). Septic mice demonstrated a significantly improved survival rate after NGAL treatment (P<0.01). Plasma-NGAL seams to be strongly involved in inflammation. For clinical relevance, it might not only be useful for AKI detection during severe inflammation - indeed it has to be interpreted carefully within this setting - but additionally might offer therapeutic potential.

Geochemical changes in individual sediment grains during sequential arsenic extractions

High concentrations of As in groundwater frequently occur throughout the world. The dissolved concentration, however, is not necessarily determined by the amount of As in the ambient sediment but rather by the partitioning of As between different minerals and the type of fixation. Sequential extractions are commonly applied to determine associations and binding forms of As in sediments. Due to the operational nature of the extracted fractions, however, the results do not provide insight into how and where precisely As is bound within mineral grains and no information about elemental associations or involved mineral phases can be gained. Furthermore, little is known about possible geochemical alterations that actually occur within a single grain during sequential extraction. Therefore, micro-synchrotron X-ray fluorescence analysis was applied to study the micro-scale distribution of As and other elements in single sediment grains. Arsenic was found to be mainly enriched in Fe oxy-hydroxide coatings along with other heavy metals resulting in high correlations. Phosphate leached 34-66% of As from the studied grains. The release of As in this leaching step was accompanied by the disappearance of correlations between As and Fe as well as by a higher Fe/As ratio compared to untreated samples. During the Fe-leaching step the coatings were largely dissolved leading to much lower concentrations of As and Fe. The correlation between As and Fe was preserved only in association with K, indicating the presence of both elements in silicate structures. Several distinctive features were observed such as the release of Fe, Mn and Cr during phosphate leaching as well as the lowering of mean K concentrations due to the Fe-leaching which indicates that not only target mineral phases were dissolved in these extraction steps. The importance of re-precipitation processes during sequential extraction was indicated by a consistently observed increase of the Fe/As ratio from the untreated to the Fe-leached samples.

Synthesis and incorporation of selenide in pyrite and mackinawite

Abstract According to performance assessment reports for high-level radioactive waste repositories, 79Se is a radionuclide that could represent a potential threat to the biosphere. Therefore knowledge of its geochemical behavior during its transport in aqueous solutions is fundamental to assess the safety of repository sites. Selenium is often associated with sulfides such as pyrite, a frequent minor constituent of host rocks and bentonite backfills considered for radioactive waste disposal. In this study, we investigated the uptake of Se by Fe sulfides synthesized in batch experiments under anoxic conditions. Results from X-ray diffraction and scanning electron microscopy analyses reveal the formation of pyrite and mackinawite. More than 98% of the Se added to solutions (initial concentration: 10−3–10−6 mol/l) was taken up by the Fe sulfide minerals. Focused ion beam analysis shows an inhomogeneous Se distribution with a higher accumulation in the center of the pyrite grains, probably due to the progressive depletion of Se from solution with regard to S. The results imply that pyrite and its most important precursor phase, mackinawite, are efficient in removing selenium from solution, which may contribute in reducing the mobility of 79Se released from radioactive waste.

The exceptional Oder Flood in summer 1997 — the fate of nutrients and particulate organic matter in the Baltic Sea

The distribution of dissolved inorganic nutrients, particulate organic matter and phytoplankton pigments in the Oder plume was investigated at peak discharge of the Oder River during the exceptional flood event in summer 1997. Mixing diagrams of dissolved inorganic nutrients (NO3-, PO43-, SiO44-) reveal a nearly complete removal of nitrate during the first steps of estuarine mixing, whereas phosphate and silicate were still available over the entire salinity range. In contrast to silicate and phosphate, the nitrate riverine end-member concentration was about 3–4 times lower than during peak discharge in spring. It appears that during the summer flooding event inorganic nitrogen was not as available as in spring due to a stronger dilution effect and the advanced retention of nitrogen by land vegetation within the drainage area in summer. Therefore, algal biomass production in the Pomeranian Bight was most certainly nitrogen limited and significant removal of other dissolved inorganic nutrients by phytoplankton blooming did not occur.