Carbon outflow from the active layer of thermokarst lake catchments in the Lena River delta

Nowadays due to climate change the interest to the hydrological processes in the permafrost affected regions is growing. Permafrost soil is important carbon pool and thawing can cause the increase of carbon outflow from Arctic river basins. During Russian-German expeditions Lena-2012 and 2013 some measurements were carried out on the catchment of the Fish Lake on Samoylovsky Island in the Lena River delta. Fish Lake is a thermokarstpolygonal lake, and the landscape of its catchment is typical for the Arctic polygonal tundra. These measurements were done in order to study the DOC income to the lake from an active layer of the catchment. Measurements of the DOC concentration in the pore water and the depth of seasonal thawing were made at 21 points in the 1,52 sq km catchment. The points were selected in different parts of the polygons to consider the heterogeneity of the landscape. Samples for DOC were analyzed in the field using a Spectro::lyser probe and in the lab with a Shimadzu TOC-L probe. In August the depth of the active layer was between 20 and 60 cm: 20-30 cm on the polygon rims, 30-60 cm in the polygon centers and near the lake. During the month when the measurements were made the depth increased by 10-15. For August the DOC concentration in the pore water of the active layer was 8-51 mg/l, for July – 5-30 mg/l, which correlates with the results of other researches in Arctic region. The changes in DOC concentration in pore water for the different thaw depth were examined. Maximum was observed on the depth 35-40 cm for July and 45-55 cm for August. So, for the same depth the variance in the concentration was the most significant. The DOC flux to the Fish Lake was calculated using the mean measured concentration and water runoff from the catchment (Ogorodnikova, 2011). The DOC daily flux to the lake is evaluated as about 0,8 kg per day and the flow rate is 0,5 kg/ km2*day, which is in ten time less than for the lake catchment of southern areas (Moore, 2003). Prolongation of field measurements is necessary for reasons clarifying and for better understanding of DOC flux formation processes under different conditions including thawing increase

Risk of hospitalization and death following prostate biopsy in Scotland

AbstractObjectiveTo investigate the risk of hospitalization and death following prostate biopsy.Study designRetrospective cohort study.MethodsOur study population comprised 10,285 patients with a record of first ever prostate biopsy between 2009 and 2013 on computerized acute hospital discharge or outpatient records covering Scotland. Using the general population as a comparison group, expected numbers of admissions/deaths were derived by applying age-, sex-, deprivation category-, and calendar year-specific rates of hospital admissions/deaths to the study population. Indirectly standardized hospital admission ratios (SHRs) and mortality ratios (SMRs) were calculated by dividing the observed numbers of admissions/deaths by expected numbers.ResultsCompared with background rates, patients were more likely to be admitted to hospital within 30 days (SHR 2.7; 95% confidence interval 2.4, 2.9) and 120 days (SHR 4.0; 3.8, 4.1) of biopsy. Patients with prior co-morbidity had higher SHRs. The risk of death within 30 days of biopsy was not increased significantly (SMR 1.6; 0.9, 2.7), but within 120 days, the risk of death was significantly higher than expected (SMR 1.9; 1.5, 2.4). The risk of death increased with age and tended to be higher among patients with prior co-morbidity. Overall risks of hospitalization and of death up to 120 days were increased both in men diagnosed and those not diagnosed with prostate cancer.ConclusionsHigher rates of adverse events in older patients and patients with prior co-morbidity emphasizes the need for careful patient selection for prostate biopsy and justifies ongoing efforts to minimize the risk of complications

Water extracts from Siberian thawing permafrost - from land to ocean

To better understand and quantify fluxes of dissolved elements upon permafrost thaw, water-soluble elements from Siberian permafrost samples covering a wide geographic range were determined by extraction. We measured the pH- and EC-values as well as the total dissolved major and secondary cation concentrations and anion concentrations for 270 water extracts from 12 different sites around the Laptev Sea. Cation concentrations were analyzed using inductively coupled plasma-optical emission spectrometry and anion concentrations by ion chromatography. Hydrogen carbonate concentrations were measured by potentiometric pH-value titration using an automatic titrator. Electrical conductivity and pH values were measured using a WTW MultiLab 540 multi-parameter device. As ground ice melts throughout Siberia with continued climate warming, drainage of the soils in many locations is improving and exposing mineral surfaces that were previously largely inert by their perennially frozen condition and unaffected by active weathering through seasonal wetting and drying cycles. Chemical analyses of water extracts allow an assessment of the potential interactions between mineral surfaces and pore melt water and the characteristics and biogeochemical and ecological consequences of the export of melt water from thawing permafrost. The (hydro-)chemical flux from permafrost sources into the riverine and marine realms is mainly defined by its source signatures and concentrations, which will be addressed in the present study. We compare our values with water data from lakes, rivers and the Arctic Ocean. The influence of terrestrial input from thawing permafrost including ground ice is expected to increase as coastal and river shore erosion as well as other permafrost degradation processes accelerate under Arctic warming and mobilize previously freeze-locked material. The increasing influx of dissolved elements influences transport and deposition processes in aquatic environments as well as nutrient supply, food chains and life cycles with largely understudied consequences for aquatic and coastal ecosystems in the Arctic

Contribution of permafrost degradation landforms to summer export of DOC from Yedoma-type Ice Complex

Thermo-erosional landforms (valleys, gullies) and their associated streams are the main connecting pathways between inland permafrost areas and rivers and coasts. Surface and ground waters are routed along these streams, which transport particulate and dissolved matter from the catchments to the rivers and coastal waters. Regions of ice-rich permafrost, such as the Yedoma-type Ice Complex, are not only characterized by a high abundance of thermo-erosional landforms, which formed during the Holocene, but are subject to extensive degradation under current arctic warming by processes such as thermal erosion, thermokarst, and active layer deepening. In the Siberian Lena River Delta Yedoma-type Ice Complex deposits occur on insular remnants of a Late-Pleistocene accumulation plain that has been dissected by Lena River branches and degraded by thermal erosion and thermokarst during the Holocene. This region serves as suitable exemplary study area for estimating the contribution of 1) different permafrost degradation landforms to the export of water and dissolved matter from Yedoma-type Ice Complex to the river and 2) active degradation of old permafrost versus seasonal runoff from the surface and active layer. In the summers of 2013 and 2014 we sampled surface and soil waters from streams and their watersheds in Yedomatype Ice Complex landscapes of the Lena River Delta and analyzed them for a range of hydrogeochemical parameters including electrical conductivity (EC), dissolved organic carbon (DOC) and stable isotopic composition.\ud The sampling sites were spread over an E-W-extent of about 150 km and are characterized by very diverse geomorphological and hydrological situations in terms of distance to the river branches, catchment size, discharge, degree of thermo-erosional activity, and connection to other permafrost degradation landforms (thermokarst lakes and basins). Three key sites were sampled three and four times from June to September 2013 and 2014, respectively, in order to analyze intra-seasonal changes. The results show large variances in EC (25 to 1205 μS/cm), DOC concentrations (2.9 to 119.0 mg/l), �18O (-29.8 to -14.6 ‰ vs. SMOW), and �D (-228.9 to -117.9‰ vs. SMOW) over the whole dataset, with distinct characteristics in the parameter combination for different degradation landform and water types. The temporal variability at the repeatedly sampled sites is low, which implies that there is not much change in the processes that determine the water composition throughout the summer season. By comparing differences in surface water chemistry between flow path systems that tap into varying amounts of source water (precipitation, surface and ground water, ground ice) and have differing residence times and extents, we explore the effect of future changes in thermokarst and thermo-erosional intensity and resulting changes in flow path hydrogeochemistry for thermoerosional features draining ice-rich permafrost

Eroding permafrost coasts release low amounts of dissolved organic carbon (DOC) from ground ice into the nearshore zone of the Arctic Ocean

Ice-rich permafrost coasts in the Arctic are highly sensitive to climate warming and erode at a pace that exceeds the global average. Permafrost coasts deliver vast amounts of organic carbon into the nearshore zone of the Arctic Ocean. Numbers on flux exist for particulate organic carbon (POC) and total or soil organic carbon (TOC, SOC). However, they do not exist for dissolved organic carbon (DOC), which is known to be highly bioavailable. This study aims to estimate DOC stocks in coastal permafrost as well as the annual flux into the ocean. DOC concentrations in ground ice were analyzed along the ice-rich Yukon coast (YC) in the western Canadian Arctic. The annual DOC flux was estimated using available numbers for coast length, cliff height, annual erosion rate, and volumetric ice content in different stratigraphic horizons. Our results showed that DOC concentrations in ground ice range between 0.3 and 347.0 mg L^-1 with an estimated stock of 13.6 ± 3.0 g m^-3 along the YC. An annual DOC flux of 54.9 ± 0.9 Mg yr^-1 was computed. These DOC fluxes are low compared to POC and SOC fluxes from coastal erosion or POC and DOC fluxes from Arctic rivers. We conclude that DOC fluxes from permafrost coasts play a secondary role in the Arctic carbon budget. However, this DOC is assumed to be highly bioavailable. We hypothesize that DOC from coastal erosion is important for ecosystems in the Arctic nearshore zones, particularly in summer when river discharge is low, and in areas where rivers are absent