Minimal biomass deposition in banded iron formations inferred from organic matter and clay relationships.

The cycling of iron and organic matter (OM) is thought to have been a major biogeochemical cycle in the early ferruginous oceans which contributed to the deposition of banded iron formations (BIF). However, BIF are deficient in OM, which is postulated to be the result of near-complete oxidation of OM during iron reduction. We test this idea by documenting the prevalence of OM in clays within BIF and clays in shales associated with BIF. We find in shales >80% of OM occurs in clays, but <1% occurs in clays within BIF. Instead, in BIF OM occurs with 13C-depleted carbonate and apatite, implying OM oxidation occurred. Conversely, BIF which possess primary clays would be expected to preserve OM in clays, yet this is not seen. This implies OM deposition in silicate-bearing BIF would have been minimal, this consequently stifled iron-cycling and primary productivity through the retention of nutrients in the sediments.

Using stable isotopes to resolve transit times and travel routes of river water: a case study from southern Finland.

The stable isotopic composition of two rivers, the Vantaanjoki River and the Kokemäenjoki River, in southern and southwestern Finland was studied to resolve the transit times and travel routes of the river water in the two different catchments. The Kokemäenjoki River is dominated by great lake basins whereas the Vantaanjoki River has been reported having a significant groundwater component. The mean residence time of the young surface flow component could be resolved by sine function fitting onto the annual fluctuations of the isotopic signal, and the amount of base flow was estimated by using the isotopic composition of the river and groundwater. In this study, we found that the methods work for simple two component catchments. In more complex cases with three different components mixing, the solution becomes increasingly difficult and requires more study.

Echoes from the past: a healthy Baltic Sea requires more effort.

Integrated sediment multiproxy studies and modeling were used to reconstruct past changes in the Baltic Sea ecosystem. Results of natural changes over the past 6000 years in the Baltic Sea ecosystem suggest that forecasted climate warming might enhance environmental problems of the Baltic Sea. Integrated modeling and sediment proxy studies reveal increased sea surface temperatures and expanded seafloor anoxia (in deep basins) during earlier natural warm climate phases, such as the Medieval Climate Anomaly. Under future IPCC scenarios of global warming, there is likely no improvement of bottom water conditions in the Baltic Sea. Thus, the measures already designed to produce a healthier Baltic Sea are insufficient in the long term. The interactions between climate change and anthropogenic impacts on the Baltic Sea should be considered in management, implementation of policy strategies in the Baltic Sea environmental issues, and adaptation to future climate change.

Comparison of the epidemiology, risk factors, outcome and degree of organ failures of patients with candidemia acquired before or during ICU treatment.

INTRODUCTION: The aim of this study was to compare the epidemiology, risk factors, severity and outcome of two types of ICU-treated candidemias: namely, ICU-acquired candidemia (acquired after 48-hour ICU stay) (ICUAC group), and those needing ICU treatment for candidemia acquired before ICU admission or during the first 48-hour ICU stay (non-ICUAC group). METHODS: A retrospective cohort study was conducted between 2000 and 2009 in a mixed tertiary ICU among patients with blood-culture-confirmed candidemia. RESULTS: The study involved 82 patients (53 men). The ICUAC group consisted of 38 patients (46.3%) and the non- ICUA group included 44 patients (53.6). The ICUAC group had undergone previous surgery more often and had ICU stays that were 3.7 times longer than the non-ICUAC group, whose members more often had co-morbidities (95.6% versus 73.7%, P = 0.001). The ICUAC group had significantly more frequent organ failures with cardiovascular, renal, central nervous and coagulation systems than the non-ICUAC group. ICU, hospital and one-year mortality rates did not differ between the groups (23%, 36.8% and 65.8%, respectively, in the ICUAC group and 26%, 44.4% and 64.4%, respectively, in the non-ICUAC group). Among patients with APACHE II scores greater than 25, the ICUAC group had lower one-year mortality (65.0% versus 87.5%). Among patients with APACHE II scores of 25 or less, the ICUAC group had higher mortality (66.7% versus 50.0). Candida albicans was most common cause of candidemia in both groups (76.3% and 68.9%, respectively). CONCLUSIONS: More than half of the ICU-treated candidemias were acquired prior to admission to the ICU. Patients with ICU- and non-ICU-acquired candidemias had different risk factors and different needs for ICU resources. Hospital mortality was similar in both groups; however, the groups had different mortality rates when the severity of disease and underlying diseases were taken into account.

Indications for the past redox environments in deep groundwaters from the isotopic composition of carbon and oxygen in fracture calcite, Olkiluoto, SW Finland.

In paleohydrogeological studies, the geochemical and isotope geochemical composition of fracture calcites can be utilised to gain information about the evolution of the composition of deep groundwaters in crystalline bedrock. The aim of our study was to investigate the latest hydrogeochemical evolution of groundwaters in the crystalline bedrock at Olkiluoto, which is the planned site for deep geological disposal of spent nuclear fuel. Samples were collected from drill cores intercepting water-conducting fractures at the upper ~500 m of the bedrock. The latest fracture calcite generations were identified using optical microscopy and electron microprobe. They occur as thin ~10-200 µm crusts or small euhedral crystals on open fracture surfaces. These latest calcite fillings were carefully sampled and analysed for the isotopic composition on carbon and oxygen. In addition, fluid inclusion homogenisation temperatures were determined on selected calcite samples. Fluid inclusion data indicated a low temperature of formation for the latest fracture calcite fillings. The δ(18)O values of calcite in these fracture fillings vary only slightly, from-7.3 to-11.5 ‰ (Vienna Pee Dee Belemnite, VPDB), whereas the δ(13)C values fluctuate widely, from-30 to+31 ‰ (VPDB). The δ(13)C values of latest calcite fillings show a systematic pattern with depth, with high and variable δ(13)C values below 50 m. The high δ(13)C values indicate active methanogenesis during the formation of the latest calcite fillings. In contrast, the present-day methanic redox environment is restricted to depths below 200-300 m. It is possible that the shift in the redox environment at Olkiluoto has occurred during infiltration of SO2-(4)-rich marine waters, the latest of such events being the infiltration of brackish waters of the Littorina Sea stage of the Baltic Sea at ~8000-3000 BP.

Quantitative analysis of environmental factors in differential weighing of blank Teflon filters.

Mass differences less than 100 microg must be correctly measured in gravimetric analysis of particles collected on filters. Even small variations in mass measurement may contribute significant errors to calculated concentrations. In addition to the collected particles, a number of other factors affect the observed mass difference between the measurements before and after sampling. The most often controlled of these factors are static charge, temperature, and humidity. Using 951 laboratory blank filter weights, we have statistically analyzed these and other factors that affect the observed filter weight. Some of these are controllable or correctable; others are not and enter into the final results as errors. The standard deviation of differential blank filter weighing after applying all corrections was 2.7 microg. The most important correctable factors are air buoyancy variation and filter storage time. When weighing blank Teflon filters at relative humidity < 50%, these are an order of magnitude more important than weighing-room humidity. Using field blank filters in each weighing batch could control these three factors but also doubles the errors caused by balance random variation and filter handling contamination, because four weighing measurements and the handling of two filters are needed to obtain one corrected differential mass result.