Dispersed methane flux to the water column from natural gas bubble streams at the Black Sea shelf

Gas bubble streams are detected in the water column by the presence of strong, flare shaped backscatter signals recorded during hydroacoustic single beam echosounder surveys (flares). Some of these flares even reach the sea surface. In motion bubbles get into an evolutionary process caused by a variety of effects, including gaseous exchange with surrounding water. Simplistically, kinetics of such a gas exchange can be described by the Fick’s law; the direction of the transfer of any given gas through the bubble depends on partial pressure of respective the gas in bubble, Henry’s law constants and the concentration of dissolved gas in the water. In general, methane gradually dissolves during the lifetime of a bubble, while other gases enter the bubble. Consequently, bubbles cause a vertical transfer of methane from the sea bottom to upper water layers and can be considered as sources of dispersed methane flux to the water column. In present work an attempt is made to trace the methane gas phase exhaustion in flares trough the water column at the Black Sea shelf.Our approach is based upon acoustic observations and measurements carried out in 2003 and 2004 with the scientific echosounder EK-500 onboard RV Vodianitskiy as part of the EU funded project CRIMEA. For the estimation of bubble size distributions our data from direct measurements of acoustic cross-section of single bubbles were used. Data for the relation between rising speed and shrinking rate vs. bubble size were obtained by tracking of single bubbles. Modelling was used to evaluate features of the gas transfer process induced by rising bubbles. Having initial bubble size, gas composition and water depth as starting conditions the model produces series of time based values of bubble size, gas composition, rising depth and rising speed. Acoustic observations were utilized to verify the chosen model parameters.For seeps detected at 90 - 95 m water depth hydroacoustically measured bubble sizes ranged from 1.3 to 11.3 mm in diameter. This bubble size range was confirmed by visual observations during video and submersible inspections.We assumed a gas content of 99% methane and small amounts of nitrogen and oxygen as initial gas composition according to geochemical analyses of gas bubbles sampled by submersible just above the sea floor. To determine the entire free methane flux from the sea floor into the water column and maybe into the atmosphere we run our model for several bubble sizes classes. Then simulation data were summed up with weighting coefficients according to the respective amount of bubbles per class. As a result, vertical profiles of molar content (mkmol) and methane flux (mkmol/s m) per average statistic bubble vs. depth were obtained. To get methane flux from the whole seepage simple multiplication is required by average statistic initial number of bubbles above the bottom per unit height. Depending on the spatial extension of the seep area, point or volume backscattering methods were used to quantify the bubble amount. Of great importance for both methods is the averaging of a high amount of data in space and time. We detected an average of 400 bubbles at high intensity seep sites within a water volume of 1m thickness above the bottom. The hydroacoustically determined amount of bubbles is again in very good agreement with direct visual observations. With an average initial rising speed of 0.25 m/s, 400 bubbles escaping from the sea floor cause a methane flux of 3.45 mmol/s using average bubble methane content of 34.5 mkmol (400 x 0.25 x 34.5 = 3.45 mmol/s). As final methane content of average bubble at the sea surface is 6.5 mkmol, only 6.5/34.5*100 = 18.8 % of methane can reach the atmosphere due to the methane flux into the water column on the way up to the sea surface

Microbial carbonate build-ups at methane seeps near the upper boundary of the gas-hydrate stability zone in the Black Sea: results of EU project CRIMEA

Extensive dredging carried out in May-June 2004 in the deeper parts of the Dnepr paleo-delta area (NW Black Sea) yielded for the first time chimney-shaped carbonate microbial build-ups, which occur at methane seeps close to upper boundary of the gas-hydrate stability zone (~ 700 m). Carbonate samples taken with a benthic trawl represent fragments of the uppermost, middle and lowest parts of the build-up, which are similar to those found previously at the shallower and deeper methane seeps in the Black Sea. At the same time, the holed, plate-like carbonates in the lowest parts of the build-up provide first indications that gas channels are formed during the earliest growth phase of these microbial structures. Stable carbon isotope analyses of the carbonates from the uppermost fragments gave the d13C values ranging from -33.7 to -36.6 pro mil, while the d13C values of the lowermost fragments are significantly lighter, varying between -42.0 and -44.6 pro mil. Both these types of carbonates indicate that a major portion of the carbonate carbon originates from bacterial oxidation of the seeping methane. Oxygen isotopic values also show differences between the more irregular and porous samples from the uppermost part of the build-up, which are composed of a mixture of aragonite and Mg-calcite (d18O = 0.7 to 0.94 pro mil, and the only Mg-calcite cemented thin slabs of lowermost carbonates (d18O = 1.35 to 1.57 pro mil. The difference in d13C/d18O ratio found in the upper and lower parts of the build-up may reflect the changing of the water temperature and salinity during the chimney growth

Seismic and hydro-acoustic evidence for subsurface controls of methane seepage in the Dnepr paleo-delta, Black Sea

The Dnepr paleo-delta in the NW Black Sea is characterized by an abundant presence of methane gas seeps. The presence of these seeps was first registered by Polikarpov et al. in 1989. During the CRIMEA 2003 expedition 1062 new plumes were detected using a SIMRAD EK 500 echosounder. All newly found plumes are located on the transition zone of the continental shelf and continental slope in water depths between 70 and 725 meters. A further exploration of the area included the collection of hydro-acoustic and geophysical datasets. For this presentation we have used these new data to get a better insight in the relation between the presence of gas seeps, seafloor morphology and subsurface structures.From the integration of the new datasets (multibeam bathymetric map, side-scan sonar mosaic, seep locations and several sparker, GI-gun and sub-bottom profiles) we could make some interesting observations:seeps are often located at crests of sediment ridges and at edges of canyons;seeps are located in areas characterised by high sea-floor backscatter values;the depth limit for the presence of seeps (725 m) almost coincides with the stability boundary of pure methane hydrate;there is a clear correlation between the depth of gas fronts within the sediments and the presence of seeps at the seafloor.These observations and the apparent absence of major faults on our seismic data suggest that the subsurface controls on methane seepage in our study area are mainly stratigraphic/sedimentary in nature.Whether the presence of seeps at the crest lines of the sediment ridges is due to the presence of more resistant coarse sediments (i.e. location of seeps is controlled by morphology) or whether these crest lines stand out due to enhanced methane-derived carbonate cementation (i.e. the morphology is controlled by the location of the seeps) is still unclear. The exact cause of the high backscatter values in the seep areas (i.e. higher degree of cementation, presence of free-gas bubbles, slightly coarser sediment due to blow-out of the finer fraction by the gas escape) is at present still unclear and awaits further ground-truthing

Возможность реализации концепции устойчивого развития рекреационного прибрежья города Ялта в отношении биогенных элементов, радионуклидов, тяжёлых металлов и хлорорганических соединений (Крым, Чёрное море)

Проведено гидроакустическое зондирование, определены площадь и объём вод приустьевой зоны реки Водопадная до глубины 40 м в акватории города Ялта (Крым, Чёрное море). Концентрации биогенных элементов (NO2, NO3, NH4 и PO4) и тяжёлых металлов (Cu, Zn, Fe, Co, Ni, Mo, Cd, Pb и Hg) в пресной воде устья реки превышают их концентрации в прибрежной морской воде в 3–64 раза. Выявлено влияние стока реки на эвтрофикацию вод изучаемой морской акватории. С использованием постчернобыльских радиоизотопов 90Sr и 137Cs выполнена датировка донных осадков и определена скорость седиментации с исследованной площади акватории региона. Рассчитаны потоки поступления загрязняющих веществ со стоком реки и периоды их оборота в рекреационном прибрежье города Ялта. Полученные результаты использованы для обоснования концепции устойчивого развития рекреационной зоны города Ялта по факторам загрязнения морской среды

EFFECT OF THE GAS MEDIA AND TEMPERATURE REGIMES OF ANNEALING ON THE PHASE COMPOSITION OF IRON BORATE FeBO3

Iron borate FeBO3 crystals are annealed in neutral, oxidizing, and reducing gas media on a specially designed setup. The effect of the chemical medium and annealing modes on the surface morphology and phase composition of the samples is established.Исследования выполнены при финансовой поддержке РФФИ, проект № 19-29-12016-мк, в части разработки экспериментальной установки и получения кристаллических образцов. Рентгеновские и электронно-микроскопические измерения проведены при под-держке Министерства науки и высшего образования РФ в рамках выполнения работ по Государственному заданию ФНИЦ «Кристаллография и фотоника» с использованием оборудования ЦКП (проект RFMEFI62119X0035)

Программное обеспечение исследований струйных метановых газовыделений акустическим методом

Природные газовыделения из морского дна, обычно, идентифицируются акустически методом по наличию в толще воды участков повышенного уровня эхо-сигнала, формой напоминающих факелы пламени. В этих акустических образах, составленных из эхо-откликов от многочисленных пузырьков газа, содержится разнообразная информация об индивидуальных свойствах пузырьков и всего газовыделяющего участка морского дна в целом. При изучении экологической роли струйных метановых газовыдений представляется важной задачей получение такой информации, в особенности: данных о размерах газовыделяющего участка; общем количество пузырьков, выделяющихся за определенный период времени; размерном составе и скорости подъема пузырьков на различных глубинах. Использование калиброванного эхолота и цифровых технологий регистрации и обработки данных представляется адекватным подход к количественному анализу акустического сигнала. В статье приводится общее описание подхода к обработке акустической информации и частная реализация этого подхода, адаптированного к исследованию струйных газовыделений при использовании научного эхолота SIMRAD EK-500 в качестве акустического инструмента. Разработанное программное обеспечение включает в себя ряд специализированных процедур, расширяющих возможности применения акустического метода для исследования струйных газовыделений. Работа этих процедур рассматривается на конкретных примерах, полученных в ряде научных экспедиций на НИС «Профессор Водяницкий».The natural gas seepages from the sea floor are commonly recognized acoustically by the flare shaped acoustic images, spreading vertically through the water column. These acoustic images, which are made up of echoes from numerous gas bubbles, convey a lot of information about features of individual bubbles and bubbling vents in whole. To study the ecological role of methane gas bubble streams it is important to obtain such data, especially: the area of a venting site; total number of bubbles, released per a time period; size spectrum and rise velocity of bubbles at different depths through the water column. An approach based on the use of calibrated echo-sounder, digital data recording and processing techniques can provide adequate quantitative analysis of the backscattering signal. This paper describes the concepts for processing of acoustic information and particular realization of these concepts, adapted to the investigation of gas bubble streams with the use of scientific echo sounder SIMRAD EK-500 as a hydroacoustic instrument. The developed software includes a number of specialized procedures expanding performance capabilities of an acoustic method for the study of natural methane seepages. The work of these procedures is demonstrated by examples, obtained during a number of scientific cruises on board the RV “Professor Vodyanitsky”

Эмиссия метана в гидро и атмосферу струйными газовыделениями в районе палео-дельты р. Днепр в Черном море

Для оценки потока метана от струйных газовыделений (сипов) применен комбинированный подход, включающий проведение детальной акустической съемки исследуемого района и анализ данных с использованием специализированного программного обеспечения, технологии ГИС и методов математического моделирования. Получена подробная карта распределения метановых сипов в районе палео-русла р. Днепр. Всего на площади 387.1 км², обследованной в этом районе, идентифицировано 2200 сипов, выделяющих 16.7 10⁶ м³ при атмосферном давлении (STP), или 12.0 10⁻³ тераграмм (Тг) метана в год. Статистическое распределение индивидуальных потоков метана от сипов соответствует логнормальному закону. По нашим оценкам, 1.9 % метана струйных газовыделений достигает атмосферы в газообразном состоянии, а 98.1% растворяется в водном столбе. Таким образом, подавляющая часть метана остается в морской воде и включается в физические, химические и биологические процессы трансформации углеродсодержащих соединений.To estimate methane flux from natural gas bubble streams (seepages) a combined approach was applied, inclusive of detailed echo survey of investigated area and data analysis with the use of specialized software, GIS technique and mathematic simulation. A precise location map of methane seepages in the Dnieper paleo-delta region was obtained. In total 2200 seepages were identified at the investigated area of 387.1 km², which release 16.74 10⁶ m³ at atmospheric pressure (STP), or 12.0 10⁻³ teragram (Tg) methane a year. Statistical distribution of individual seepage methane flux rates conforms to the lognormal law. We found that 1.9% of methane from gas bubble streams reaches the atmosphere in gas phase, while 98.1% dissolves in the water column. Thus, the most part of methane remains in sea water and enters into physical, chemical and biological transformation processes of carbon-containing compounds

Application of mitomycin in the treatment of cicatricial complications after radical prostatectomy

At a choice of a way of treatment of the localized prostate cancer not the last place is occupied by an assessment of possible complications after the executed operation. In structure of all postoperative complications cicatricial changes take only the third place, however at calculation of absolute figures are represented as a serious world problem. The article presents the global data and our own data for the prevention of complications after performing open radical prostatectomy and also experience with Mitomycin.</em