sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

changes in the source of sedimentary organic matter in the marginal sea sediments of eastern hainan island in response to human activities during the past 200 years abstract marine sediments have been frequently used to reconstruct the records of environment change and human activities we collected four sediment cores from wanquan river estuary and the eastern continental shelf of hainan island in the south china sea and analyzed the down core physical and chemical properties of sub samples based on 210pb dating the longest core had a record of the most recent 200 years while the other three profiles were slightly younger the results show that both the toc tn ratios and fossil fuel corrected organic 13c of marine sediments for all four cores remained relatively constant before 1950 ad indicating relatively stable sedimentary material sources however after 1950 ad the toc tn ratios and organic 13c in all four sediment cores displayed decreasing and increasing trends respectively indicating that the proportion of marine derived material increased whereas the land derived materials that were mainly transported by the wanquan river decreased this is consistent with the obvious decrease in runoff and sediment discharges of the wanquan river due to the increase in human activities including industrial and agricultural production and domestic water use in hainan island since 1950 ad therefore we suggest that environmental changes on the land were recorded by changes in the source material of marine sediments collected from coasts and estuaries

the pacific meridional mode and the occurrence of tropical cyclones in the western north pacific abstractthis study investigates the association between the pacific meridional mode pmm and tropical cyclone tc activity in the western north pacific wnp it is found that the positive pmm phase favors the occurrence of tcs in the wnp while the negative pmm phase inhibits the occurrence of tcs there observed relationships are consistent with those from a long term preindustrial control experiment 1000 yr of a high resolution tc resolving geophysical fluid dynamics laboratory gfdl forecast oriented low ocean resolution flor coupled climate model the diagnostic relationship between the pmm and tcs in observations and the model is further supported by sensitivity experiments with flor the modulation of tc genesis by the pmm is primarily through the anomalous zonal vertical wind shear zvws changes in the wnp especially in the southeastern wnp the anomalous zvws can be attributed to the responses of the atmosphere to the anomalous warming in the northwestern part of the pmm pattern during th

large scale patterns associated with tropical cyclogenesis in the western pacific abstract five characteristic low level large scale dynamical patterns associated with tropical cyclogenesis in the western north pacific basin are examined along with their capacity to generate the type of mesoscale convective systems that precede genesis an 8 yr analysis set for the region is used to identify and create composites for the five characteristic patterns of monsoon shear line monsoon confluence region monsoon gyre easterly waves and rossby energy dispersion this brings out the common processes that contribute to tropical cyclogenesis within that pattern which are described in detail a 3 yr set of satellite data is then used to analyze the mesoscale convective system activity for all cases of genesis in that period and to stratify based on the above large scale patterns it is found that mesoscale convective systems develop in all cases of genesis except one seventy percent of cases developed mesoscale convective systems at more than one time during the genesis period and 44 of

mercury emissions and stable isotopic compositions at vulcano island italy abstract sampling and analyses methods for determining the stable isotopic compositions of hg in an active volcanic system were tested and optimized at the volcanic complex of vulcano aeolian islands italy condensed gaseous fumarole hg fum t plume gaseous elemental hg g 0 and plume particulate hg p ii were obtained at fumaroles f0 f5 f11 and fa the average total hg emissions based on hgt so2 in condensed fumarolic gases and plumes range from 2 5 to 10 1 kg y 1 in agreement with published values ferrara r mazzolai b lanzillotta e nucaro e pirrone n 2000 volcanoes as emission sources of atmospheric mercury in the mediterranean basin sci total environ 259 1 3 115 121 aiuppa a bagnato e witt m l i mather t a parello f pyle d m martin r s 2007 real time simultaneous detection of volcanic hg and so2 at la fossa crater vulcano aeolian islands sicily geophys res lett 34 l21307 plume hg p ii increases with distance from the fumarole vent at the expense of hg g 0 and indicates significant in plume oxidation and condensation of fumarole hg fum t relative to the nist srm 3133 hg standard the stable isotopic compositions of hg are 202hg fum t 0 74 0 18 2sd n 4 for condensed gaseous fumarole hg fum t 202hg g 0 1 74 0 36 2sd n 1 for plume gaseous elemental hg g 0 at the f0 fumarole and 202hg p ii 0 11 0 18 2sd n 4 for plume particulate hg p ii the enrichment of hg p ii in the heavy isotopes and hg g 0 in the light isotopes relative to the total condensed fumarolic hg fum t gas complements the speciation data and demonstrates a gas particle fractionation occurring after the gas expulsion in ambient t atmosphere a first order rayleigh equilibrium condensation isotope fractionation model yields a fractionation factor cond gas of 1 00135 0 00058

the multidecadal variability of the asymmetric mode of the boreal autumn hadley circulation and its link to the atlantic multidecadal oscillation abstractprevious studies show that the first principal mode of the variability of the seasonal mean hadley circulation hc is an equatorial asymmetric mode am with long term trend this study demonstrates that the variability of the boreal autumn september november son hc is also dominated by an am but with multidecadal variability the son am has ascending and descending branches located at approximately 20 n and 20 s respectively and explains about 40 of the total variance further analysis reveals that the am is closely linked to the atlantic multidecadal oscillation amo which is associated with a large cross equatorial sea surface temperature sst gradient and sea level pressure slp gradient the cross equatorial thermal contrast further induces an equatorial asymmetric hc anomaly numerical simulations conducted on an atmospheric general circulation model also suggest that amo associated sst anomalies can also induce a cross equatorial slp gradient and anomalous vertical shear of the

intensified interannual relationship between tropical cyclone genesis frequency over the northwest pacific and the sst gradient between the southwest pacific and the western pacific warm pool since the mid 1970s abstractthe sea surface temperature gradient sstg between the southwest pacific swp 40 20 s 160 e 170 w and the western pacific warm pool wwp 0 16 n 125 165 e in boreal spring was revealed to contribute significantly to the interannual variability of tropical cyclone tc genesis frequency over the western north pacific wnp since 1980 the present study extends the analysis back to 1951 results show that the interannual relationship between the sstg and wnp tc genesis frequency is statistically significant only after the mid 1970s while insignificant prior to 1974 further analyses show that the sstg is strongly negatively correlated with the sst anomaly ssta in the central pacific cp in the recent period while with the ssta in the equatorial eastern pacific ep in the prior period in the prior period the spring positive negative ep ssta induces an anticyclonic cyclonic circulation over the wnp this partly offsets the impact of the sstg anomaly on the atmospheric circulation ov

spatial and temporal variation in the isotopic composition of mercury in the south river va abstract historic point source mercury hg inputs from industrial processes on the south river waynesboro virginia ended many decades ago but sediment and surface water hg concentrations remain elevated relative to the regional background to understand hg sources mobility and fate in the south river we analyzed total hg concentrations and hg stable isotope compositions of streambed sediments bank soils suspended particles filtered surface waters and channel margin hyporheic zone pore waters hg isotopes allow for the identification of three distinct hg end member inputs to the south river consisting of a regional background source and two isotopically distinct contaminant sources hydrologic conditions are demonstrated to have an influence on within channel hg isotope fractionation and hg partitioning with no observed isotopic discrimination between suspended particulate hg and filtered surface water hg during elevated flow conditions channel margin hyporheic zone porewaters had significantly higher 202hg values than surface waters 202hg 0 52 0 44 and 202hg 0 89 0 20 respectively mean 1sd a subset of porewaters exhibited mass independent fractionation signatures 199hg 0 33 0 06 200hg 0 19 0 03 mean 1sd that are suggestive of a precipitation derived origin for the dissolved hg pool sediments from a floodplain profile were analyzed to explore the temporal variation in hg isotopic composition within the south river indicating brief excursions up to 202hg 0 61 from the average composition observed in modern samples 202hg 0 52 0 09 by improving understanding of the spatial temporal and hydrologic conditions that contribute to variations in hg isotopic composition this study provides insights into the processes that control hg isotopic end member sources hg loading to the channel during elevated flows and hg fate in the south river

decadal changes in tropical cyclone activity over the western north pacific in the late 1990s a pronounced decadal change in tropical cyclone tc activity over the western north pacific wnp in the late 1990s was identified based on a comparison of the two epochs that occurred before and after the late 1990s the tc genesis number exhibited an evident decrease over the southern wnp s wnp 5 20 n 105 170 e and an increase over the northern wnp n wnp 20 25 n 115 155 e which partly corresponded to a significant northward migration in the seasonal mean latitudinal location of tc genesis i e from 17 2 n to 18 7 n after the late 1990s the northwestward moving track became the most dominant track mode accompanied by the weakening of both the westward moving track and the northeastward recurving track meanwhile the tc occurrence frequency tcf experienced evident increases over southeastern china and the okinawa islands while prominent decreases occurred over the south china sea the philippine sea japan and east of japan changes in the tcf were determined by tc genesis changes tc track shifts and variations in regional tc durations which were all ascribed to the decadal change in tropical indo pacific sea surface temperature the full picture on the decadal changes in the wnp tc activity revealed in this study may provide useful guidance for regional tc seasonal forecasts and future projections

interhemispheric thermal gradient and tropical pacific climate 1 we explore the impact of interhemispheric thermal gradients forcing on the tropical pacific ocean atmosphere climate in an intermediate coupled model the equatorial zonal sea surface temperature sst gradient strengthens with an increased northward interhemispheric thermal gradient the increase arising from earlier onset and later retreat of the seasonal cold tongue and intensification during the peak cold season when the mean interhemispheric thermal gradient is reversed the central equatorial pacific sst annual cycle abruptly reverses in phase with its cold season in mar may rather than sep nov while startling this response is consistent with a prevailing hypothesis that ties the cold tongue sst annual cycle phase to the hemispheric mean asymmetry of the intertropical convergence zone el nino southern oscillation activity is also sensitive to the interhemispheric thermal gradient with peak activity occurring when the mean gradient is small reducing rapidly as the mean gradient increases in either direction

tracing anthropogenic hg and pb input using stable hg and pb isotope ratios in sediments of the central portuguese margin abstract three short marine sediment cores from the cascais submarine canyon csc cores 252 32 and 252 35 and the estremadura spur core 252 16 on the central portuguese margin were analysed for hg pb al and mn concentrations and both pb and hg stable isotope compositions in order to reconstruct trends in hg and pb sources and accumulation sediment ages were determined based on 210pb measurements the studied cores reveal increasing hg and pb concentration independent of grain size variations since the middle of the 19th century towards the present concomitantly a decreasing trend of 206pb 207pb to less radiogenic values towards the surface was found indicating increasing anthropogenic inputs the lowest values of 202hg were generally observed in the older sediments characterized by low hg and pb concentrations suggesting a low input of anthropogenic metals odd mass number 199hg and 201hg hg isotopes in sediment samples from core 252 16 were characterized by positive mass independent fractionation mif while recent sediments from cores 252 32 and 252 35 did not reveal significant mif probably reflecting both the proximity to the source of anthropogenic hg contamination tagus estuary and the importance of the csc as a particle carrier the multi tracer approach based on both stable hg and pb isotopic signatures confirms anthropogenic hg and pb enrichment in recent marine sediments and also allows us to distinguish between areas dominated by detrital e g csc versus hemipelagic estremadura spur sedimentation

isotope geochemistry of mercury and its relation to earthquake in the wenchuan earthquake fault scientific drilling project hole 1 wfsd 1 abstract based on the wenchuan earthquake fault scientific drilling project wfsd we first investigated the distribution of the total mercury thg from 600 m to 1035 m of wfsd hole 1 core wfsd 1 the concentrations of thg in the fault gouge are significantly higher than in the sandstone shale siltstone and cataclasite in wfsd 1 the thg concentrations in the main seismic fault zone range from 9 9 to 73 5 ng g while those under the main fault range from 20 5 to 36 ng g to determine the source of hg typical rocks from different depths were chosen for hg isotope analysis the results show that 202hg in the main seismic fault zone range from 0 11 to 2 68 and below the seismic fault zone 202hg are from 0 64 to 1 33 the seismic fault rocks are more enriched in thg and have a larger variation of 202hg compared to the other rocks mercury has different isotopic compositions and fractionation mechanisms in the fault zone which are mainly affected by the earthquake and the fluid the mercury isotope compositions reflect the fluid activities at the main fault zone we demonstrate that mercury stable isotope ratios could serve as an effective tool for tracing mercury sources and monitoring and predicting earthquakes

mercury distributions and mercury isotope signatures in sediments of dongjiang the pearl river delta china abstract the pearl river delta prd is one of the most industrialized and urbanized regions in china in order to assess the pollution status of mercury hg in prd river system the distribution of total mercury hgt and methylmercury me hg in sediment from a large river named dongjiang dj was for the first time investigated hgt concentrations in sediment increased from the upstream to downstream of dongjiang area and at most sites of dj were significantly higher than the background values which suggested that the dj was contaminated with hg especially in the downstream of dj me hg concentrations in sediment of dj ranged from 0 56 to10 62 ng g and were significantly correlated with hgt and organic matter in order to determine the potential hg contamination sources typical sediments from different parts of dj were chosen for hg isotope analysis the results showed that the mass dependent fraction mdf in the sediments varied significantly 202hg 2 35 to 0 60 and the mass independent fraction mif in the sediments also varied considerably 199hg 0 02 to 0 27 the samples with the highest hgt located in the industrial area had the highest 202hg 1 14 to 0 60 measured values and insignificant mif 199hg 0 04 to 0 01 meanwhile the samples with the lowest hgt located in the background area had the lowest 202hg 2 16 to 1 55 and 199hg 0 20 to 0 27 measured values unlike the above two cases are the samples located in the urban area which have relative lower mdf 202hg 2 35 to 1 96 and small but significant mif 199hg 0 10 to 0 08 with relative higher hgt we demonstrated that the dominant hg sources in dj sediments could be categorized as the regional background urban and industrial sources in our study we demonstrated that hg stable isotope method could serve as an effective tool for tracing mercury contamination sources in the environment

impacts of tropical north atlantic sst on western north pacific landfalling tropical cyclones abstractthis study examines the impacts of tropical north atlantic tna sea surface temperature anomaly ssta on western north pacific wnp landfalling tropical cyclones tcs the authors find that tna ssta has significant negative correlations with the frequency of tcs making landfall in china vietnam the korean peninsula and japan and the entirety of east asia tna ssta influences the frequency of tc landfalls in these regions by regulating tc genesis location and frequency associated with modulated environmental conditions during cold tna sst years larger low level relative vorticity and weaker vertical wind shear lead to more tc formations over the south china sea scs and western philippine sea wps and larger low level relative vorticity higher midlevel relative humidity and weaker vertical wind shear result in more tc formations over the eastern part of wnp ewnp more tcs forming over different regions are important for more tc landfalls in vietnam mainly forming over the scs and w

interdecadal variation of tropical cyclone genesis and its relationship to the convective activities over the central pacific using the outgoing longwave radiation olr data from the national oceanic and atmospheric administration archives this paper analyzes the interdecadal variation of convective activities over the central pacific cp from july to october of 1979 2013 and its impact on tropical cyclone tc genesis in the western north pacific wnp concurrent with the interdecadal decrease of tc genesis the tropical convection underwent a significant interdecadal change in the late 1990s overall the first leading empirical orthogonal function mode of the tropical olr during july october turned from a zonal dipole pattern during 1979 1997 to a tripole pattern during 1998 2013 concomitant to this change the boreal part of the walker circulation shrank westward with its downdraft branch located over the cp the downward motion anomalies over the cp increased after the late 1990s as did the trade easterlies consistent with the cp convective activity anomalies the negative low level relative vorticity anomalies and upper level divergence anomalies positive vertical wind shear anomalies and anomalous abundant water vapor can be observed over the southeastern part of the wnp additionally the tropical depression td type waves associated with the cp convective activities are significantly different before and after the late 1990s before the late 1990s the off equatorial td type waves could be distinctly observed with clear transitions located along the wnp monsoon trough however these transitions were vague after the late 1990s therefore the convective activities over the cp may have played an important role in affecting the interdecadal change of tc genesis by affecting the genesis of td type waves

mercury distribution and transport in a contaminated river system in kazakhstan and associated impacts on aquatic biota abstract the river nura in central kazakhstan has been heavily polluted by hg originating from an acetaldehyde plant a number of studies were undertaken to investigate the transport fate and bioavailability of hg in this river system the sediments within a 20 km section of the river downstream of the effluent outfall canal are highly polluted and are acting as a strong source of surface water contamination mercury transport in the river is dominated by the remobilization of contaminated bed sediments and river bank erosion during the annual spring flood peak hg concentrations in unfiltered surface water samples during a larger than usual flood event in 2004 were in the order of 1600 4300 ng l 1 the majority of the particulate bound hg appears to be sedimented in the shallow intumak reservoir 75 km downstream of the source of the pollution leading to a drop in aqueous hg concentrations by an order of magnitude nevertheless background concentrations of hg in surface water are not reached until at least 200 km downstream and during the flood period hg is also detected in the terminal wetlands of the river mercury concentrations in sediment cores taken from the river bed in the most contaminated section of the nura ranged from 9 95 to 306 mg kg 1 methylmercury mehg levels in shallow sediment cores were highest in surface sediments and ranged between 4 9 and 39 g kg 1 but were generally less than 0 1 of total hg thg a significant inverse relationship was found between thg concentrations and the percentage of mehg formed in the sediments irrespective of the sampling depth the observed relationship was confirmed by comparison with results from a different river system indicating that it may be true also for other highly contaminated aquatic systems it is hypothesized that at high thg levels in severely contaminated sediments the accumulation of mehg may be limited by increasingly efficient demethylation processes and that this underlying trend in sediments is the reason why mehg levels in surface water are often found to be higher at less contaminated sites compared to upstream sites mercury concentrations in biota in the most contaminated section of the river were 15 20 times higher than background levels fish were found to be impacted for more than 125 km downstream from the source indicating significant transport of dissolved mehg to downstream areas and or in situ mehg production in less contaminated downstream reaches there were also indications that impoundments may increase the bioavailability of hg

identification of contamination in a lake sediment core using hg and pb isotopic compositions lake ballinger washington usa abstract concentrations and isotopic compositions of hg and pb were measured in a sediment core collected from lake ballinger near seattle washington usa lake ballinger has been affected by input of metal contaminants emitted from the tacoma smelter which operated from 1887 to 1986 and was located about 53 km south of the lake concentrations and loadings of hg and pb in lake ballinger increased by as much as three orders of magnitude during the period of smelting as compared to the pre smelting period concentrations and loadings of hg and pb then decreased by about 55 and 75 respectively after smelting ended isotopic compositions of hg changed considerably during the period of smelting 202 hg 2 29 to 0 38 mean 1 23 n 9 compared to the pre smelting period 202 hg 2 91 to 2 50 mean 2 75 n 4 variations were also observed in 206 pb 207 pb and 208 pb 207 pb isotopic compositions during these periods data for 199 hg and 201 hg indicate mass independent fractionation mif of hg isotopes in lake ballinger sediment during the smelting and post smelting period and suggest mif in the ore smelted during the smelting process or chemical modification at some point in the past negative values for 199 hg and 201 hg for the pre smelting period are similar to those previously reported for soil peat and lichen likely suggesting some component of atmospheric hg variations in the concentrations and isotopic compositions of hg and pb were useful in tracing contaminant sources and the understanding of the depositional history of sedimentation in lake ballinger

iron biogeochemistry in holocene palaeo and actual salt marshes in coastal areas of the pampean plain argentina in salt marshes the hydrodynamics and the availability of iron organic matter and sulphate influence the formation and or dissolution of iron sulfides and iron oxyhydroxides therefore they constitute key factors affecting the iron biogeochemical processes in these environments the aim of this work is to evaluate the physico chemical and mineralogical variations associated to iron biogeochemistry in palaeo and actual salt marshes in the area of influence of the mar chiquita coastal lagoon pampean plain argentina in soils of exhumed palaeo marshes the iron contents are 56 95 mol g 1 whereas these contents decrease to 36 75 mol g 1 in actual marsh soils the presence of framboidal and poliframboidal pyrites associated with gypsum barite calcite halite and iron oxyhydroxides defines the conditions of the pedosedimentary sequences of the holocene paleomarshes sequences of pyrite formation sulfidization and degradation sulfuricization were observed these processes were evidenced by a sequential extraction reflecting that the largest proportion of iron is in the form of crystalline iron oxides 28 76 and lepidocrocite 6 16 while the proportion associated with ferrihydrite and pyrite is low 0 9 and 1 17 respectively these facts could be partly explained by the complex redox processes characteristic of these environments such as aeration generated by the rhizosphere and intense bioturbation by invertebrates these iron biomineralizations have been useful because they allow paleoenvironmental interpretations and characterization of paleomarshes and environmental inferences related to the management of actual salt marshes

pyritization a palaeoenvironmental and redox proxy reevaluated abstract pyrite as a proxy for the redox states of bottom waters was evaluated in the context of modern salt marsh sediments two sites 40 m apart with very different physicochemical properties were sampled seasonally the sites differed from each other in 1 the amount of tidal flushing 2 vegetation 3 redox condition below the sediment water interface 4 carbon content and 5 solid phase iron oxyhydroxide and iron sulfide content of the sediment the calculated degree of pyritization dop varies between 0 44 and 1 0 depending on the site and the season different dop values were obtained for the same samples when different techniques were applied for extraction of reactive iron framboidal pyrite was dominant however other textural forms of pyrite were also observed the size distribution of the individual pyrite crystals and the framboids was fairly narrow with the majority of them having diameters

mercury isotopic composition of hydrothermal systems in the yellowstone plateau volcanic field and guaymas basin sea floor rift abstract to characterize mercury hg isotopes and isotopic fractionation in hydrothermal systems we analyzed fluid and precipitate samples from hot springs in the yellowstone plateau volcanic field and vent chimney samples from the guaymas basin sea floor rift these samples provide an initial indication of the variability in hg isotopic composition among marine and continental hydrothermal systems that are controlled predominantly by mantle derived magmas fluid samples from ojo caliente hot spring in yellowstone range in 202hg from 1 02 to 0 58 0 11 2sd and solid precipitate samples from guaymas basin range in 202hg from 0 37 to 0 01 0 14 2sd fluid samples from ojo caliente display mass dependent fractionation mdf of hg from the vent 202hg 0 10 0 11 2sd to the end of the outflow channel 202hg 0 58 0 11 2sd in conjunction with a decrease in hg concentration from 46 6 pg g to 20 0 pg g although a small amount of hg is lost from the fluids due to co precipitation with siliceous sinter we infer that the majority of the observed mdf and hg loss from waters in ojo caliente is due to volatilization of hg0 aq to hg0 g and the preferential loss of hg with a lower 202hg value to the atmosphere a small amount of mass independent fractionation mif was observed in all samples from ojo caliente 199hg 0 13 1 0 06 2sd but no significant mif was measured in the sea floor rift samples from guaymas basin this study demonstrates that several different hydrothermal processes fractionate hg isotopes and that hg isotopes may be used to better understand these processes

intensified impact of east indian ocean sst anomaly on tropical cyclone genesis frequency over the western north pacific abstracta recent finding is the significant impact of the sea surface temperature anomaly ssta over the east indian ocean eio on the genesis frequency of tropical cyclones tcs over the western north pacific wnp in this study it is shown that such an impact is significant only after the late 1970s the results based on both data analysis and numerical model experiments demonstrate that prior to the late 1970s the eio ssta is positively correlated with the equatorial central pacific ssta and the latter produces an opposite atmospheric circulation response over the wnp to the former as a result the impact of the eio ssta on the tc genesis over the wnp is largely suppressed by the latter after the late 1970s the area coverage of the eio ssta is expanding this considerably enhances the large scale circulation response over the wnp to the eio ssta and significantly intensifies the impact of the eio ssta on tc genesis frequency over the wnp the results from this study have great implications for s

impacts of the boreal spring indo pacific warm pool hadley circulation on tropical cyclone activity over the western north pacific abstractthis study investigated the impacts of the interannual variability in the boreal spring regional hadley circulation over the indo pacific warm pool ipwp on the tropical cyclone tc activity over the western north pacific wnp the principal modes of the interannual variability in the ipwp hadley circulation were calculated using empirical orthogonal function eof analysis the leading mode eof 1 features cross equatorial southerly wind anomalies over the indian ocean and maritime continent and has an evident impact on wnp tc activity during summer in the summer following a positive phase of the eof 1 a cyclonic circulation anomaly with upward motion positive relative vorticity anomalies and weak sea level pressure dominates the wnp and this favors increased tc genesis however large positive vertical wind shear anomalies over the south china sea and philippine sea inhibit the tc intensification a positive wind sea surface temperature sst precipitation feedback was found to facili

contributions of sst anomalies in the indo pacific ocean to the interannual variability of tropical cyclone genesis frequency over the western north pacific abstractthis study attempts to evaluate quantitatively the contributions of sea surface temperature sst anomalies in the indo pacific ocean to the interannual variability of tropical cyclone tc

mercury isotope fractionation in fossil hydrothermal systems the hg isotopic compositions of samples throughout the vertical extent of two fossil hydrothermal systems were analyzed by multicollector inductively coupled plasma mass spectrometry results show 5 2 0 2 hg 1 9 8 hg relative to nist 3133 fractionation more than 50 times greater than the 0 1 2 external reproducibility of the analyses the hg isotope compositions from both hydrothermal systems can be grouped by dominant mineralogy and position 2 0 2 hg 1 9 8 hg values at the tops of the systems are 3 5 to 0 4 in cinnabar dominant sinter and 0 2 to 2 1 in metacinnabar dominant sinter and the underlying veins have 2 0 2 hg 1 9 8 hg values of 1 4 to 1 3 these differences probably resulted from the combination of boiling of the hydrothermal fluid oxidation near the surface and kinetic effects associated with mineral precipitation the natural variation in hg isotopic compositions observed in this study is higher than that expected from the trend of decreasing mass dependent fractionation with increasing mass extrapolated from stable isotope systems up to z 26 fe confirming that even the heaviest elements undergo significant stable isotope fractionation in hydrothermal systems

geochemistry of iron and manganese in soils and sediments of a mangrove system island of pai matos cananeia sp brazil abstract five zones along a transect of 180 m were selected for study on the island of pai matos sao paulo brazil four of the zones are colonised by vascular plants spartina sp laguncularia lg avicennia av and rhizophora rh and were denominated soils and the other zone which lacks vegetation was denominated sediment sd the geochemical conditions differed significantly in soils and sediment and also at different depths the soils were oxic eh 350 mv or suboxic eh 350 100 mv at the surface and anoxic eh

possible linkage between the monsoon trough variability and the tropical cyclone activity over the western north pacific abstractthe present study investigates the influence of the monsoon trough mt on the interannual variability of tropical cyclone tc activity over the western north pacific during july november for the period 1979 2007 it is shown that the tc activity is closely related to the mt location during the years when the mt extends eastward retreats westward more less tcs form within the southeastern quadrant of the western north pacific such a relationship can be explained by the changes in large scale environmental factors associated with the movement of the mt an eastward extension of the mt coincides with warmed ocean surface enhanced convection increased relative humidity in the lower and midtroposphere reduced vertical shear of zonal wind intensified upper level divergence and low level anomalous cyclonic vorticity over the southeast quadrant of the western north pacific these conditions associated with the eastern extension of the mt are favorable for tc genesis while those associated w

authigenic kaolinite and associated pyrite in chalk of the cretaceous niobrara formation eastern colorado abstract cores from the smoky hill chalk member of the cretaceous niobrara formation have several zones containing authigenic kaolinite as spherical moldic polycrystalline aggregates that occur within single or multichambered foraminiferal tests and are commonly associated with framboidal pyrite such kaolinite is inferred to result from volcanic ash deposited during chalk sedimentation shortly after burial a colloidal aluminous gel or solution formed from the unstable ash and moved into organic rich foraminiferal tests where sulfate reducing bacteria created a favorable microenvironment for the simultaneous crystallization of kaolinite and pyrite

modulation of tropical cyclogenesis location and frequency over the indo western north pacific by the intraseasonal indo western pacific convection oscillation during the boreal extended summer abstractthe influence of the intraseasonal indo western pacific convection oscillation ipco on tropical cyclone tc genesis location and frequency over the indo western north pacific wnp during the boreal extended summer may october is explored observational analysis shows that the impacts of the intraseasonal ipco on tcs over the indo wnp include an evident phase lock of tc genesis location and distinct differences in tc frequency in the wnp in the positive intraseasonal ipco phase the atmosphere gains heat through the release of latent heat in cumulus convective condensation and the anomalous cyclonic circulation weakens the western pacific subtropical high wpsh and enhances tc genesis thereby tending to produce many more tcs moreover the diminished wpsh and the westward shift of the centers of anomalous cyclonic circulations lock tc genesis locations to the west wnp and lower latitudes around 5 20 n especially in the south china sea the almost opposite situation occurs in a nega

are mangrove forest substrates sediments or soils a case study in southeastern brazil abstract morphological and analytical data corresponding to several profiles from two mangrove systems in the brazilian state of sao paulo were examined for evidence of pedogenetic processes plant activity exerted a strong effect on the processes occurring in mangrove substrates especially on the intensity of these processes and therefore constitutes one of the major factors involved in the differentiation of sediments and soils colonization of substrates by vascular plants leads to drastic changes in physicochemical conditions the redox processes were much more diverse in the soil than in the sediment substrate without vegetation in the former they varied with depth with oxic or suboxic conditions being observed at the surface and anoxic conditions observed below 30 cm whereas in the sediment anoxic conditions were observed throughout likewise the acid base conditions were more variable in the soils ranging from strongly acid to neutral and in the sediment they were close to neutral furthermore different pedogenetic processes were identified 1 addition of organic matter by accumulation of vegetable debris and dead roots with formation in some cases of a histic epipedon 2 transfer of soluble iron fe2 towards the surface and precipitation in the form of fe oxyhydroxide and transfer of the mineral particles due to the bioturbation caused by activity of crabs 3 transformation of elements such as iron gleization and sulphur sulphidization changes undergone in the mangrove substrates were also characterized by simultaneity and intergradations between pedogenesis and diagenesis especially in the lowermost layers in which authigenesis appears to intensify thus the presence of smectite minerals in the clay fraction may be attributed to authigenic processes that take place in both soils and sediments

the sst gradient between the southwestern pacific and the western pacific warm pool a new factor controlling the northwestern pacific tropical cyclone genesis frequency abstractthe sea surface temperature gradient sstg between the southwestern pacific ocean 40 20 s 160 e 170 w and the western pacific warm pool 0 16 n 125 165 e in boreal spring has been identified as a new factor that controls the interannual variability of tropical cyclone tc frequency over the western north pacific ocean wnp this sstg can explain 53 of the total variance of the wnp tc genesis frequency during the typhoon season for the period 1980 2011 the positive sstg anomaly produces an anomalous cross equatorial pressure gradient and thus anomalies in low level southward cross equatorial flow and tropical easterlies over the central western pacific the anomalous easterlies further produce local equatorial upwelling and seasonal cooling in the central pacific which in turn maintains the easterly anomalies throughout the typhoon season these dynamical thermodynamical effects induced by the positive sstg anomaly lead to a reduced low level cyclonic shear increased vertical wind sh

modulation of tropical cyclone tracks over the western north pacific by intra seasonal indo western pacific convection oscillation during the boreal extended summer this study investigates the effect of the intra seasonal indo western pacific convection oscillation ipco on tropical cyclone tc tracks over the western north pacific wnp during the boreal extended summer may october the number of west and northwest moving tc tracks is found to sharply increase over the wnp in the positive intra seasonal ipco phase recurving tracks have greater weight in the negative intra seasonal ipco phase possible physical mechanisms are further examined in terms of steering flow energy conversion and energy propagation when the intra seasonal ipco phase is positive the first order moment term of perturbation potential energy ppe1 converts into perturbation kinetic energy pke at lower latitudes the pressure trough spreads farther to the east meanwhile rossby waves emanating from the convective centers of the intra seasonal ipco over the wnp wavewnp and eeio waveeeio travel into the trough region thereby deepening the trough these features enhance the westward and northwestward steering flow between 20 n and about 30 n sharply increasing the number of straight west and northwest moving tc tracks over the wnp when the intra seasonal ipco is in a negative phase conversion from ppe1 to pke at lower latitudes is suppressed and the trough weakens more ppe1 converts to pke in the climatological western pacific subtropical high wpsh region and the wpsh is intensified moreover waveeeio intensifies the north south ridge of the wpsh over the southern indian peninsula meanwhile part wavewnp propagate northeastward these features favor northeastward motion of tcs over the wnp

mass dependent and mass independent variations in the isotope composition of mercury in a sediment core from lake ontario as related to pollution history and biogeochemical processes abstract historical variations in the isotope composition of mercury hg in lake ontario were examined for the purpose of characterising the isotope signatures of the sources of hg contamination and investigating their fate in the environment the lake has been polluted with hg organochlorine compounds and other contaminants from industrial and urban sources chlor alkali plants being historically the principal sources of hg the pollutants were discharged into the niagara river transported to the lake by fluvial action and deposited in fine grained sediments analysis of a dated sediment core from the lake revealed that the hg concentration increased sharply in the 1890s peaked in the 1930s 1940s and 1960s and then declined levelling off in the late 1900s the values of the 198 hg 202 hg 199 hg 202 hg 200 hg 202 hg and 201 hg 202 hg ratios of the hg that formed the peaks decreased with increasing total hg concentration thus the isotope signature of the anthropogenic hg was formed by mass dependent fractionation mdf which caused preferential depletion in the lighter isotopes suggesting evaporation from hg 0 electrodes in the chlor alkali plants the background hg above and below the peaks also showed inverse correlations with total hg but formed separate regression lines reflecting the fact that its origins and pre depositional history were different the isotope signatures were altered appreciably by both mdf and mass independent fractionation mif attributable to natural processes in the lake mdf caused secondary enrichment in lighter isotopes and mif caused intermittent 201 hg enrichment associated with episodes of fe and mn oxyhydroxide precipitation feooh abundance showed a marked dip coinciding with maximum concentrations of organochlorine compounds in the 1960s but 201 hg enrichment by mif increased significantly with the concentrations of certain chlorobenzene compounds these findings suggest that mif was mediated by bacteria including oxyhydroxide precipitating species and that organochlorines inhibited feooh producing bacteria whereas the chlorobenzenes stimulated bacterial enzyme activity involved in mif

new oceanic proxies for paleoclimate environmental variables such as temperature and salinity cannot be directly measured for the past such variables do however influence the chemistry and biology of the marine sedimentary record in a measurable way reconstructing the past environment is therefore possible by proxy such proxy reconstruction uses chemical and biological observations to assess two aspects of earth s climate system the physics of ocean atmosphere circulation and the chemistry of the carbon cycle early proxies made use of faunal assemblages stable isotope fractionation of oxygen and carbon and the degree of saturation of biogenically produced organic molecules these well established tools have been complemented by many new proxies for reconstruction of the physical environment these include proxies for ocean temperature mg ca sr ca 44ca and ocean circulation cd ca radiogenic isotopes 14c sortable silt for reconstruction of the carbon cycle they include proxies for ocean productivity 231pa 230th u concentration nutrient utilization cd ca 15n 30si alkalinity ba ca ph 11b carbonate ion concentration foraminiferal weight zn ca and atmospheric co2 11b 13c these proxies provide a better understanding of past climate and allow climate model sensitivity to be tested thereby improving our ability to predict future climate change proxy research still faces challenges however as some environmental variables cannot be reconstructed and as the underlying chemistry and biology of most proxies is not well understood few proxies have been applied to pre pleistocene times another challenge for future research only by solving such challenges will proxies provide a full understanding of the range of possible climate variability on earth and of the mechanisms causing this variability

contribution of the interdecadal pacific oscillation to the recent abrupt decrease in tropical cyclone genesis frequency over the western north pacific since 1998 abstractprevious studies have documented an abrupt decrease of tropical cyclone tc genesis frequency over the western north pacific wnp since 1998 in this study results from an objective clus

the geochemical behavior and isotopic composition of hg in a mid pleistocene western mediterranean sapropel abstract the concentrations of mercury hg and other trace metals ni cu zn mo ba re u and the hg isotopic composition were examined across a dramatic redox and productivity transition in a mid pleistocene mediterranean sea sapropel sequence characteristic trace metal enrichment in organic rich layers was observed with organic rich sapropel layers ranging in hg concentration from 314 to 488 ng g avg 385 with an average enrichment in hg by a factor of 5 9 compared to organic poor background sediments which range from 39 to 94 ng g hg avg 66 comparison of seawater concentrations and sapropel accumulations of trace metals suggests that organic matter quantitatively delivers hg to the seafloor near complete scavenging of hg from the water column renders the sapropel hg isotopic composition representative of mid pleistocene mediterranean seawater sapropels have an average 202hg value of 0 91 0 15 n 5 1 sd and 199hg value of 0 11 0 03 n 5 1 sd background sediments have an average 202hg of 0 76 0 16 n 5 1 sd and 199hg of 0 05 0 01 n 5 1 sd which is indistinguishable from the sapropel values we suggest that the sapropel isotopic composition is most representative of the mid pleistocene tyrrhenian sea

mass independent fractionation of mercury isotopes in the environment 1 the toxicity of mercury s methylated species and its biomagnification in aquatic food chains and global dispersion by the atmosphere are the cause of worldwide health problems recent reports have observed natural mass dependent fractionation in mercury isotopes and recent theoretical work has demonstrated that isotopic separation in mercury is due primarily to nuclear field shifts nuclear volume effect and the magnetic spin effect gives rise to mass independent fractionation mif of odd neutron number isotopes now we present analytical evidence of mass independent isotopic variations in mercury produced by both nuclear volume and magnetic isotope processes even mass number isotopes exhibit a pattern indistinguishable from that produced by mass dependent fractionation with both positive and negative 199hg and 201hg anomalies mif is easier to reliably determine in hg isotopes than mass dependent fractionation alone and thus it provides a potentially important key in constraining models of mercury sources and pathways in the environment

isotope geochemistry of mercury in source rocks mineral deposits and spring deposits of the california coast ranges usa abstract we present here the first study of the isotopic composition of mercury in rocks ore deposits and active spring deposits from the california coast ranges a part of earth s crust with unusually extensive evidence of mercury mobility and enrichment the franciscan complex and great valley sequence which form the bedrock in the california coast ranges are intruded and overlain by tertiary volcanic rocks including the clear lake volcanic sequence these rocks contain two types of mercury deposits hot spring deposits that form at shallow depths the franciscan complex and great valley sequence contain clastic sedimentary rocks with higher concentrations of mercury than volcanic rocks of the clear lake volcanic field mean mercury isotopic compositions 202hg for all three rock units are similar although the range of values in franciscan complex rocks is greater than in either great valley or clear lake rocks hot spring and silica carbonate mercury deposits have similar average mercury isotopic compositions that are indistinguishable from averages for the three rock units although 202hg values for the mercury deposits have a greater variance than the country rocks precipitates from spring and geothermal waters in the area have similarly large variance and a mean 202hg value that is significantly lower than the ore deposits and rocks these observations indicate that there is little or no isotopic fractionation