Temperature sensitivity of soil respiration is dependent on readily decomposable C substrate concentration

International audienceTemperature acclimation of soil organic matter (SOM) decomposition is one of the major uncertainties in predicting soil CO2 efflux by the increase in global mean temperature. A reasonable explanation for an apparent acclimation proposed by Davidson and colleagues (2006) based on Michaelis-Menten kinetics suggests that temperature sensitivity decreases when both maximal activity of respiratory enzymes (Vmax) and half- saturation constant (Ks) cancel each other upon temperature increase. We tested the hypothesis of the canceling effect by the mathematical simulation of the data obtained in the incubation experiments with forest and arable soils. Our data confirm the hypothesis and suggest that concentration of readily decomposable C substrate as glucose equivalent is an important factor controlling temperature sensitivity. The highest temperature sensitivity was observed when C substrate concentration was much lower than Ks. Increase of substrate content to the half-saturation constant resulted in temperature acclimation associated with the canceling effect. Addition of the substrate to the level providing respiration at a maximal rate Vmax leads to the acclimation of the whole microbial community as such. However, growing microbial biomass was more sensitive to the temperature alterations. This study improves our understanding of the instability of temperature sensitivity of soil respiration under field conditions, explaining this phenomenon by changes in concentration of readily decomposable C substrate. It is worth noting that this pattern works regardless of the origin of C substrate: production by SOM decomposition, release into the soil by rhizodeposition, litter fall or drying-rewetting events

ОПРЕДЕЛЕНИЕ ПРИМЕСЕЙ В ОСОБО ЧИСТЫХ НАНОПОРОШКАХ ОКСИДА ИТТРИЯ, ЛЕГИРОВАННОГО НЕОДИМОМ, МЕТОДОМ АТОМНО-ЭМИССИОННОЙ СПЕКТРОМЕТРИИ С ИНДУКТИВНО СВЯЗАННОЙ ПЛАЗМОЙ

The technique of inductively coupled plasma atomic-emission spectrometry determination of Al, Ba, Be, Ca, Cd, Co, Cr, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sb, V and Zn in neodymium doped yttrium oxide nanopowders was developed. The limits of quantitation raged in diapason 10-5-10-4 % mass. Matrix effects were minimized using the standards and blank solutions with the same content of matrix (≈ 1 %mass.) as the samples solutions.Keywords: inductively coupled plasma atomic emission spectrometry, yttrium oxide, determination of impurities(Russian)DOI: http://dx.doi.org/10.15826/analitika.2013.17.2.006I.I. Yevdokimov, V.G. PimenovG.G. Devyatykh Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences, Nizhny Novgorod, Russian FederationРазработана методика атомно-эмиссионного с индуктивно связанной плазмой анализа особо чистых нанопорошков оксида иттрия, легированного неодимом, – прекурсоров оптической керамики – с пределами определения примесей Al, Ba, Be, Ca, Cd, Co, Cr, Fe, K, Li, Mg, Mn, Na, Ni, Pb, Sb, V и Zn на уровне 10-5-10-4 % мас. Матричные помехи при анализе 1 %-х растворов проб учитывали применением близких по матричному составу градуировочных растворов и растворов холостого опыта.Ключевые слова: атомно-эмиссионная спектрометрия с индуктивно связанной плазмой, оксид иттрия, определение примесейDOI: http://dx.doi.org/10.15826/analitika.2013.17.2.00

ГРАВИТАЦИОННОЕ РАЗДЕЛЕНИЕ В УСЛОВИЯХ СПЕЦИАЛЬНО ФОРМИРУЕМОГО ВЫСОКОГО СОДЕРЖАНИЯ МЕТАЛЛОВ В ИСХОДНОМ СЫРЬЕ

The article presents the results of researching metal-containing raw material preparation in two-compartment jigging machine, the distinctive feature of which is that the jigging concentrate is extracted in the first compartment, into which initial feed is loaded and the undersize from the second compartment is returned. The subject matter of a new aftertreatment diagram of heavy fraction on concentration tables is that the heavy fraction is divided into two equal parts, which are supplied to the installed parallel tables mixing the concentrate of one them with initial feed of another table where ready gravio-concentrate is produced. It is proved that the concurrent extraction of gold from copper-pyritic ores using the proposed flow sheet diagram allows increasing gold extraction from 5,12 to 9,89 %. As a result of pilot tests of the developed scheme of gravity separation with formation of high metal content in the head of the process, it is determined that its use for extracting lead from slag (4–6 %) from soda smelting of used battery scrap in rotary kilns allows increasing extraction of lead in concentrate by 7,7 % and its content in gravity concentrate by 14,7 %.Приведены результаты исследования обогащения металлсодержащего сырья на двухкамерной отсадочной машине, отличительной особенностью работы которой является то, что концентрат отсадки выделяют в первой камере машины, в которую загружают исходное питание и возвращают подрешетный продукт второй камеры машины. Сущность новой схемы перечистки на концентрационных столах тяжелой фракции отсадки состоит в том, что ее делят на 2 равные части и направляют на параллельно установленные столы, смешивая концентрат одного из них с исходным питанием другого, на котором получают готовый гравиоконцентрат. Доказано, что попутное выделение золота из медно-колчеданных руд с помощью предложенной схемы позволяет увеличить его извлечение с 5,12 до 9,89 %. В результате опытно-промышленных испытаний разработанной технологии гравитационной сепарации с формированием высокого содержания металла в голове процесса установлено, что ее использование для извлечения свинца из шлаков (4–6 %) от содовой плавки лома отработанных аккумуляторных батарей в короткобарабанных печах позволяет повысить извлечение свинца на 7,7 %, а его содержание в концентрате гравитации – на 14,7 %

РАЗРАБОТКА НОВОЙ СХЕМЫ И СПОСОБА ФЛОТАЦИИ РУД ОЛИМПИАДИНСКОГО МЕСТОРОЖДЕНИЯ

The article presents the results of sulfide ore beneficiation of the «Olympiad» deposit according two flow sheets – the existing plant and the new one according to which the concentrate is produced in two stages: roughing I stream flow concentrate is extracted from 1/2 of raw materials and mixed with another 1/2 part of the raw materials and finished roughing II streamflow concentrate is produced. Mixture of the air (t = 15÷20 °С) with water vapor (t = 104 °С, р = 0,12 MPa) is used in II streamflow as gas phase during flotation. A device for measurement of steam bubble size has been developed. Bubble size is shown to be reduced 2,0–2,5 times under the conditions simulating the air-vapor flotation process. In using streamflow air-vapor flotation flow sheet, the concentrate yield decreases from 4,01 to 2,98 % while maintaining the reached level of gold recovery thus reducing the burden and cost for the subsequent operations of bio-oxidation and cyanidation of the concentrate.Приведены результаты обогащения сульфидных руд Олимпиадинского месторождения по двум схемам – действующей фабрики и новой, по которой черновой концентрат получают в два приема: из 1/2 части исходного сырья выделяют черновой концентрат I-й струи обогащения, смешивают его с другой 1/2 частью исходного сырья и выделяют готовый черновой концентрат II-й струи обогащения. Во II-й струе при флотации в качестве газовой фазы применяют смесь воздуха (t = 15÷20 °С) с водяным паром (t = 104 °С, р = 0,12 МПа). Разработано устройство для измерения размера пузырьков пара. Показано, что в условиях, моделирующих процесс паровоздушной флотации, размер пузырьков сокращается в 2,0– 2,5 раза. При использовании схемы струйной паровоздушной флотации выход концентрата уменьшается с 4,01 до 2,98 % при сохранении достигнутого уровня извлечения золота, что снижает нагрузку и затраты на последующие операции биоокисления и цианирования концентрата

Temperature response of soil respiration is dependent on concentration of readily decomposable C

International audienceTemperature acclimation of soil organic matter (SOM) decomposition is one of the major uncertainties in predicting soil CO2 efflux associated with the increase in global mean temperature. A reasonable explanation for an apparent acclimation proposed by Davidson and colleagues (2006) based on Michaelis-Menten kinetics suggests that temperature sensitivity decreases when both maximal activity of respiratory enzymes (Vmax) and half-saturation constant (Ks) cancel each other upon temperature increase. We tested the hypothesis of the canceling effect by the mathematical simulation of data obtained in incubation experiments with forest and arable soils. Our data support the hypothesis and suggest that concentration of readily decomposable C substrate (as glucose equivalents) and temperature dependent substrate release are the important factors controlling temperature sensitivity of soil respiration. The highest temperature sensitivity of soil respiration was observed when substrate release was temperature dependent and C substrate concentration was much lower than Ks. Increase of substrate content to the half-saturation constant by glucose addition resulted in temperature acclimation associated with the canceling effect. Addition of the substrate to the level providing respiration at a maximal rate Vmax leads to the acclimation of the whole microbial community as such. However, growing microbial biomass was more sensitive to the temperature alterations. This study improves our understanding of the instability of temperature sensitivity of soil respiration under field conditions, attributing this phenomenon to changes in concentration of readily decomposable C substrate

Two modes of longe-range orientation of DNA bases realized upon compaction.

Formation of compact particles from linear DNA-anthracycline complexes is accompanied by appearance of intense bands in the CD spectra in the region of absorption of DNA bases (UV-region) and in the region of absorption of anthracycline chromophores (visible region). The intense (positive or negative) bands in the region of anthracycline absorption demonstrate an ordered helical location of anthracycline molecules on the DNA template. This fact, in its turn, is related to formation of the DNA superstructure in PEG-containing water-salt solutions with a long-range orientation of nitrogen bases. Possible types of DNA superstructures and the relation between the local- and the long-range order of bases in the DNA superstructure are discussed