Flux and Seasonality of Dissolved Organic Matter From the Northern Dvina (Severnaya Dvina) River, Russia

Pan‐Arctic riverine dissolved organic carbon (DOC) fluxes represent a major transfer of carbon from land‐to‐ocean, and past scaling estimates have been predominantly derived from the six major Arctic rivers. However, smaller watersheds are constrained to northern high‐latitude regions and, particularly with respect to the Eurasian Arctic, have received little attention. In this study, we evaluated the concentration of DOC and composition of dissolved organic matter (DOM) via optical parameters, biomarkers (lignin phenols), and ultrahigh resolution mass spectrometry in the Northern Dvina River (a midsized high‐latitude constrained river). Elevated DOC, lignin concentrations, and aromatic DOM indicators were observed throughout the year in comparison to the major Arctic rivers with seasonality exhibiting a clear spring freshet and also some years a secondary pulse in the autumn concurrent with the onset of freezing. Chromophoric DOM absorbance at a350 was strongly correlated to DOC and lignin across the hydrograph; however, the relationships did not fit previous models derived from the six major Arctic rivers. Updated DOC and lignin fluxes were derived for the pan‐Arctic watershed by scaling from the Northern Dvina resulting in increased DOC and lignin fluxes (50 Tg yr−1 and 216 Gg yr−1, respectively) compared to past estimates. This leads to a reduction in the residence time for terrestrial carbon in the Arctic Ocean (0.5 to 1.8 years). These findings suggest that constrained northern high‐latitude rivers are underrepresented in models of fluxes based from the six largest Arctic rivers with important ramifications for the export and fate of terrestrial carbon in the Arctic Ocean

СОПОСТАВЛЕНИЕ ТЕСТОВ С АНТИГЕНАМИ ESAT6-CFP10 IN VIVO И IN VITRO ПРИ ЛАТЕНТНОЙ ИНФЕКЦИИ И ЛОКАЛЬНЫХ ФОРМАХ ТУБЕРКУЛЕЗА У ДЕТЕЙ

Study aimed to compare the results of skin test with allergen tuberculosis recombinant (ATR), containing proteins ESAT-6 and CFP-10 and QuantiFERON test (QFT) in children with different forms of tuberculosis infection. The results of test with ATR and QFT coincided with 164 (82.4%) children. Both tests were positive in 140 (70.4%) patients, both tests were negative in 24 (12.0%). The opposite results were obtained in 35 (17.6%) children. The most common combination was ATR -positive/QFT-negative – 23 (11.6%), the less common type was ATR-negative/QFT-positive – 12 (6.0%). It was concluded that test with ATR has advantages in screening children for tuberculosis since it is simpler and cheaper. Additionally, the use of QFT is indicated in difficult diagnostic cases, with a recent infection, in young children, in the presence of immunodeficiency.Исследование посвящено сравнению результатов кожного теста с аллергеном туберкулезным рекомбинантным (АТР), содержащим белки ESAT-6 и CFP-10 и теста QuantiFERON (QFT) у детей с различными формами туберкулезной инфекции. Результаты пробы с АТР и QFT совпадали у 164 детей (82,4%) случаев. Оба теста были положительны у 140 (70,4%) пациентов, оба отрицательны – у 24 (12,0%). Противоположные результаты наблюдались у 35 (17,6%) детей. Наиболее частой была комбинация результатов АТР-положительный/QFT-отрицательный – 23 (11,6%), реже встречалось сочетание АТР-отрицательный/QFT-положительный – 12 (6,0%). Сделано заключение, что тест с АТР предпочтителен при скрининге детей на туберкулез как более простой и дешевый. Дополнительно применение QFT показано в сложных диагностических случаях, при недавнем сроке заражения, у детей раннего возраста, при наличии иммунодефицито

Small Boreal Lake Ecosystem Evolution under the Influence of Natural and Anthropogenic Factors: Results of Multidisciplinary Long-Term Study

Small aquatic ecosystems of the boreal zone are known to be most sensitive indicators of on-going environmental change as well as local anthropogenic pressure, while being highly vulnerable to external impacts. Compared to rather detailed knowledge of the evolution of large and small lakes in Scandinavia and Canada, and large lakes in Eurasia, highly abundant small boreal lakes of northwest Russia have received very little attention, although they may become important centers of attraction of growing rural population in the near future. Here we present the results of a multidisciplinary, multi-annual study of a small boreal humic lake of NW Russia. A shallow (3 m) and a deep (16 m) site of this lake were regularly sampled for a range of chemical and biological parameters. Average multi-daily, summer-time values of the epilimnion (upper oxygenated) layer of the lake provided indications of possible trends in temperature, nutrients, and bacterio-plankton concentration that revealed the local pollution impact in the shallow zone and overall environmental trend in the deep sampling point of the lake. Organic phosphorus, nitrate, and lead were found to be most efficient tracers of local anthropogenic pollution, especially visible in the surface layer of the shallow site of the lake. Cycling of trace elements between the epilimnion and hypolimnion is tightly linked to dissolved organic matter speciation and size fractionation due to the dominance of organic and organo-ferric colloids. The capacity of lake self-purification depends on the ratio of primary productivity to mineralization of organic matter. This ratio remained >1 both during winter and summer periods, which suggests a high potential of lake recovery from the input of allochthonous dissolved organic matter and local anthropogenic pollution

The evolution of the ecosystems of thermokarst lakes of the Bolshezemelskaya tundra in the context of climate change

In the conditions of climate warming, the thawing of permafrost can provoke the formation of new thermokarst lakes and subsidence, which facilitates the removal of organic matter from thawed peat into natural waters. Hydrochemical studies of surface waters of the Bolshezemelskaya tundra have demonstrated the exponential dependence of the physicochemical parameters on the size of the water body (peat subsidence, thaw ponds, small lakes, thermokarst lakes). The hydrochemical features of thermokarst lakes of the Bolshezemelskaya tundra are determined by high content of DOC, surface runoff and the thickness of peat deposits. Measurements of concentrations and fluxes of methane showed that all studied water bodies of the Bolshezemelskaya tundra are oversaturated with CH4, and depressions, subsidence, and small water bodies (<100 m2) are characterized by the highest concentrations of DOCs. The contribution of these small reservoirs to the total coverage of the surface of the Bolshezemelskaya tundra area is significant, and their consideration can greatly change the assessment of methane fluxes from the arctic tundra