rates of trace metal and nutrient diagenesis in an intertidal creek bank abstract carbon mineralization in marine sediments is a key process involved in the cycling of carbon nutrients and trace metals however as marine sediments are usually diffusion dominated the pace of element and nutrient cycling is slow because consumption of oxidants and or nutrients in the pore waters via microbial activity often outpaces resupply adding an advective flow component to such a system should change the biogeochemical dynamics considerably numerical simulations show that shallow coastal aquifers affected by tidal forces can establish ground water velocities of up to 7 cm h 1 driving a circulation of sea water through the sediments with subsequent discharge although known to enhance solute exchange the impact of advection on early diagenesis has not received much attention to address this issue we mapped the interstitial water chemistry down to 2 5 m sediment depth along a transect on an intertidal creek bank that is subject to a periodic advective flow additionally a recently developed hydrogeological simulation of the creek bank was applied to calculate ages of the sampled pore waters sample ages obtained were used to quantify flow path integrated production or depletion rates for trace metals nutrients and sulphate we find young sea water percolating relatively fast through sediments close to the creek showing strong signs of alteration whereas pore waters from diffusion dominated regions are less altered the increase in inorganic nutrients and some trace elements along the flow path requires high rates of turnover sulphate molybdenum and uranium are almost completely depleted after 200 days while dissolved inorganic carbon dic ammonia and manganese increase averaged production rates for dic appear to be three times higher when advection dominated the subsurface flow regime our results demonstrate that sites dominated by advection generally show signs of faster rates of diagenetic reactions

sulfur iron and carbon cycling following hydrological restoration of acidic freshwater wetlands abstract freshwater re flooding is a relatively novel approach to remediate drained acid sulfate soil ass wetlands this study documents the geochemical consequences of restoring freshwater re flooding for contemporary reduced inorganic sulfur ris and iron species in two coastal floodplain ass wetlands re flooding has established predominantly reducing suboxic conditions and encouraged organic carbon accumulation in surface sediments 20 30 the ph of former sulfuric horizons has increased by 2 3 units partly in response to alkalinity generation from anaerobic metabolism of organic carbon coupled with fe iii and so 4 2 reduction despite considerable sulfidisation reactive fe fe r sum of 1 m hcl and citrate dithionite extracts and non sulfidic fe ii remain abundant in both wetlands high concentrations of fe 2 up to 5 mm in wetland porewaters represent a considerable pool of labile net acidity and is partly a result of insufficient s ii to sequester excess fe 2 accumulation of iron sulfides appears to be constrained more by so 4 2 and carbon availability rather than fe r reformation and accumulation of ris species is greatest in organic rich surface horizons 40 500 mol g 1 where time integrated ris accumulation rates approximate 10 100 nmol g 1 d 1 while pyrite is the dominant ris species to have formed since re flooding there is anomalous accumulation of s 0 up to 80 mol g 1 accounting for 50 of the ris pool in some samples greigite fe 3 s 4 has formed in near surface sediments and while avs s is a minor component of the ris pool overall at some locations maximum concentrations exceed 300 mol g 1 contemporary near surface pyrite is characterised by abundant small 200 300 nm crystals in contrast to relic sedimentary pyrite of estuarine origin that is dominated by larger crystals with diverse habit although fe and so 4 2 reduction are partly responsible for wetland scale recovery from acute acidification the resultant accumulation of diverse ris species in surficial sediments indicates an oxidative component to the s cycle and represents a hysteresis in s cycling that contrasts markedly with the drained conditions existing before remediation analysis of seasonal climate fluctuations suggests that near surface sediments containing contemporary ris are vulnerable to oxidation and possible temporary re acidification during future drought episodes this study underscores the long term legacy of ass wetland drainage and highlights the need for both considered hydrological management of re flooded wetlands and further study to quantify possible re acidification risks associated with seasonal drought

did early man reach java during the late pliocene abstract homo erectus pithecanthropus reached java from the asian continent and became one of the oldest islanders in the world this article deals with the palaeomagnetic and 40 ar 39 ar dating of the lower lahar a layer located at the base of the fossil bearing series of the sangiran dome combined 40 ar 39 ar and palaeomagnetic data show that the deposition of the lower lahar marking the emergence of the first dryland at sangiran took place at the end and just after the olduvai subchron therefore c 1 7 million years can be considered as a maximal theoretical age for the arrival of the first hominids at sangiran

geochronology of early human settlements in java what is at stake abstract despite the fact java island is a volcanic area it has been challenging to build a chronological framework of its early human settlements from the oldest lower pleistocene homo erectus up to the dispersals that followed the last glacial maximum lgm various dating methods are implemented on volcanic effluents sedimentary deposits speleothems and also on fossils including direct analyses on human remains thanks to radiometric and palaeodosimetric grounded techniques as well as to magnetostratigraphy however a number of results must be considered with caution in order to identify specific bias originating from reworking of volcanic effluents or post depositional geochemical evolution such bias might well explain apparent contradictions between absolute dating results and other chronologically significant proxies e g biostratigraphy converging age estimates resulting from the implementation of several dating methods though being sometimes less precise seem to have a higher reliability

assessing redox zones and seawater intrusion in a coastal aquifer in south korea using hydrogeological chemical and isotopic approaches a shallow 25 m coastal alluvial groundwater system underneath a paddy field in the yangyang area of south korea was investigated to examine the occurrence of redox processes the aquifer is affected by seawater intrusion and is characterized by a highly reducing environment facilitated by high organic matter in the sediments hydrochemical data with 34s and 18o of sulfate were examined for depth specific groundwater from two multilevel samplers that were installed at seaward yy2 and landward yy1 locations shallow groundwater showed distinct patterns of redox zoning evidence of significant bacterial sulfate reduction bsr was observed throughout the nearly entire depths of the two boreholes while at the depths of active seawater intrusion in yy2 conditions suitable for methanogenesis were never reached thus at yy2 the deep zone of intense bsr was overlain by a zone in which methanogenesis occurred in a low sulfate environment in contrast concurrent bsr and methanogenesis in yy1 occurred at depths with high sedimentary organic matter and low dissolved sulfate due to intensive bsr considerable bsr in the groundwater representing trapped seawater in a clay layer had resulted in a very strong increase of 34ssulfate up to 99 9 the inferred sulfur isotopic enrichment factor e for bsr in the lower part of yy2 was 12 3 while e at yy1 was much higher 45 9 in addition the observed trends of 18osulfate at yy1 indicated significant oxygen isotope exchange of sulfate oxygen with ambient water likely because of lower cell specific rates of bsr and higher sulfur isotope fractionation as indicated by the 34s in contrast there was little evidence of oxygen isotope exchange between water and so42 at yy2 this study indicates that in coastal aquifers with sulfate reducing activity 34s and 18o of sulfate can reveal zones of active seawater intrusion and of trapped seawater this study provides an example of the application of sulfur and oxygen isotope data with hydrochemical and hydrogeologic data to interpret complex redox zonation in an organic rich coastal environment

redox geochemistry in organic rich sediments of a constructed wetland treating colliery spoil leachate abstract the results are reported of a geochemical study of sediment cores and surface waters taken over an annual cycle from the compost based constructed wetland at quaking houses ne england the wetland was built to treat acidic and metalliferous waters emanating from colliery spoil the influent waters contain up to 10 mm so 4 2 total fe around 100 m and a mean ph of 6 2 the organic rich sediments sustain a coupled redox cycle of fe and s which occurs throughout the year but which is more intense in the summer months throughout the sediments reduction of fe iii and so 4 2 apparently occur within the same macroscopic volume of sediment along with oxidation of sulfide and fe iii in the top 2 cm of the sediment pore water fe concentrations reach a maximum of 1 mm in the presence of high concentrations of fe oxides and the occurrence of so 4 reduction partial re oxidation of sulfide is indicated by the presence of significant elemental s total fe in the surface 10 cm has a mean value of 7 9 of sediment dry weight of which sulfide fe represents 7 12 and reactive amorphous fe 20 45 around 90 of the solid phase sedimentary fe occurs as oxides or oxyhydroxides it is suggested that the downwards diffusion of dissolved fe from the near surface maximum is sustained by the precipitation of fe oxides as a result of radial o 2 loss from roots in the dense rhizosphere pore water ph is between 7 2 and 7 8 and alkalinity increases downwards coupled to microbial so 4 and fe reduction transport processes occurring at and across the sediment water interface are sufficiently rapid in the 20 h residence time of the waters to a remove 70 90 of influent fe and 15 25 of influent so 4 into surface sediments and b increase both the ph and alkalinity of effluent waters coupling of the fe and s cycles is fundamental to effective remediation in terms of both alkalinity generation and the retention of metals

stable sulfur isotope dynamics in an acid sulfate soil landscape following seawater inundation abstract in 2002 a tidally driven seawater exchange remediation strategy was successfully implemented on a severely acidified tropical coastal landscape dominated by acid sulfate soils ass in northern australia this study examined changes in the stable sulfur isotope signatures in a range of sulfide and sulfate so4 fractions at three sites with different levels of exposure to the tidally driven seawater exchange remediation 34s in the acid soluble so4 fraction e g jarosite was less depleted in 34s than the corresponding sulfide indicating a degree of fractionation during sulfide oxidation and jarosite precipitation the 34s of jarositic so4 was similar at all three sites indicating the appreciable stability of jarositic so4 even after extended exposure to seawater 34s of the water soluble exchangeable and schwertmannitic so4 reflect conditions post remediation and indicate the relative contributions from two potential so4 sources a lighter so4 derived from the oxidation of pyrite and a heavier so4 derived from the seawater the 34s of the contemporary surficial sulfide accumulations also reflect a so4 contribution from seawater used for remediation and were isotopically different from the relict sulfides found at depth at all sites 34s of water soluble sulfate allowed the progress of the remediation to be traced down the soil profile this study demonstrates the utility of stable sulfur isotope signatures in various sulfide and so4 fractions to trace the sulfur geochemical pathways occurring in soils in this case as a result of the introduction of tidally driven sea water

insular dwarfism in canids on java indonesia and its implication for the environment of homo erectus during the early and earliest middle pleistocene abstract several canid fossils which were originally discovered and described in the early 20th century are known from early and earliest middle pleistocene of java indonesia here we revise the taxonomy and relative age of the javanese canid fossils in light of recent developments in the taxonomy and phylogeny of canidae and new insights in the evolution of island mammals results show that cuon was absent during the early and earliest middle pleistocene while the large sized xenocyon previously megacyon was present in the early pleistocene and replaced by the small sized xenocyon previously mececyon during the earliest middle pleistocene the latter is probably an anagenetic dwarf derived from the larger form of the preceding period the change in body size of xenocyon on java over time is likely the effect of increased competition within the carnivore guild within the restricted boundaries of the island simultaneously with a pronounced body size shift a dietary shift from large sized prey to much smaller prey must have taken place in order to meet energetic constraints the degree of endemism of terrestrial mammals of the earliest middle pleistocene horizon of the site trinil which has also yielded homo erectus fossils indicates that during this period java was marginally isolated which allowed for a corridor dispersal to the island with subsequent vicariance the nature and degree of isolation may have been similar to that of late pleistocene sicily but of a longer duration given the higher degree of dwarfism of the stegodon antilope and canid the following continentalisation enabled the invasion by mainland terrestrial mammals as is seen in younger layers at trinil and eventually by homo sapiens and cuon in the late pleistocene holocene

the rain forest in java through the quaternary and its relationships with humans adaptation exploitation and impact on the forest abstract relations between humans and the rain forest in java island began during the lower pleistocene but clear evidence for anthropic impact and clearance of the forest does not occur until late in the holocene after the rise of the ancient kingdoms on java at the end of 1st millennium a d the history of landscape change in java over the last 2 5 million years appears highly complex and linked to the repetitive expansion and fragmentation of the rain forest over this time these processes are now much better understood thanks to the range of palaeoenvironmental studies undertaken at various altitudes and in locations that show the dynamics of rain forest in response to variations in climatic and regional environmental change the extent of rain forest throughout the holocene appears to have been quite sensitive to small perturbations making it somewhat difficult to discriminate especially for relatively ancient holocene forest recessions between a climatic cause and one of anthropic origin clear evidence of intensive human impact on rain forest is observed late c 1500 years ago a pattern that is repeated in other parts of island southeast asia this paper will focus on the history of the landscape changes in java during the quaternary with special reference to the dynamics of rain forest structure and composition largely drawn from available pollen analyses subsequently the paleoenvironmental palaeoanthropological and archaeological records are considered to investigate the adaptive relationships between human groups and the forest through time

rb sr record of fluid rock interaction in eclogites the marun keu complex polar urals russia abstract rb sr internal mineral isochrons in the eclogite facies marun keu metamorphic complex polar urals russia date periods of fluid rock interaction and record the metamorphic reaction history the marun keu complex consists of late proterozoic to early ordovician mostly igneous rocks that experienced a subduction related non pervasive eclogite facies metamorphism followed by a local decompression related amphibolite facies overprint during the uralian orogeny field observations show that metamorphic reactions as well as ductile deformation are controlled by local availability of a free fluid phase isotopic data reveals that availability of fluids similarly exerts control on isotope distribution from a relic gabbro which has never been infiltrated by free fluids a premetamorphic rb sr age of 467 39 ma was obtained rb sr isochron ages for 14 samples of eclogite and amphibolite facies assemblages sampled from within or close to metamorphic fluid veins range from 352 5 ma to 360 3 ma a sm nd isochron for a metagranite yields an age of 354 4 ma taken together the ages for both prograde and retrograde metamorphic assemblages overlap within analytical uncertainty and yield an average value of 355 5 1 4 ma indicating that the metamorphic evolution and incipient exhumation of the marun keu complex proceeded rapidly the results demonstrate that assemblages preserve their rb sr isotopic signatures as long as they remain devoid of free fluids and that only fluid rock interaction may cause sr isotope redistribution in addition the data suggest local fluid rock equilibrium low fluid rock ratios with overall fluid deficiency and limited fluid mobility at depth however some fluids must have been mobile on the km scale since they can be traced into the suprasubduction zone mantle wedge metasomatic veins in the rai iz ophiolite yield a rb sr mineral isochron age of 373 1 5 4 ma they are interpreted as evidence for suprasubduction zone metasomatism in an oceanic setting prior to subduction of the east european margin and associated formation of eclogites in the marun keu complex we propose that rb sr mineral isochron ages provide hygrochronological rather than thermochronological constraints they define the cooling history only in combination with zircon and apatite fission track data the straightforward interpretation of rb sr mineral ages as cooling ages is obsolete

enrichment and heterogeneity of trace elements at the redox interface of fe rich intertidal sediments abstract redox interfacial sediments can undergo radical geochemical changes with oscillating tides in this study we examine trace element enrichment and availability at both landscape and pedon scales in the surface sediments of a remediating acidic tidal wetland fe rich sediments at the surface water interface 0 10 mm in depth were collected across an elevation gradient spanning the supratidal to subtidal range these sediments were analysed for solid phase fe fractions and trace elements as pb cr cu mn ni zn v b co mo ba and u via dilute hcl extractions and total digests their concentrations were compared with those of underlying 0 05 0 65 m in depth former sulfuric horizon sediments of a coastal acid sulfate soil cass reactive fe was enriched at the redox interface by up to 16 times 197 g fe kg that of the former sulfuric horizon the proportion of total trace elements associated with reactive phases was high in interfacial sediments representing over 90 of b and u and 50 of pb cu zn v and ba extractable by dilute hcl the interfacial sediments were particularly enriched in reactive cr cu ni zn b mo and u with reactive b mo and u concentrations between 5 and 10 times greater than in the former sulfuric horizon surface enrichment of trace elements is strongly co associated with fe iii mineralisation likely via sorption and co precipitation processes enrichment is highly spatially heterogeneous and is strongly influenced by elevation and tidal zonation at a landscape scale and by sediment micro topography and preferential advective transport via surface connected macropores at the pedon scale the results from this study provide new insights to the processes influencing trace element enrichment in fe rich redox interfacial sediments across a remediating acidic tidal wetland

sulfur storage and alkalinity generation in new england lake sediments we measured rates of burial and forms of reduced s in lake sediments to evaluate the importance of so z reduction to the alkalinity budget of several new england lakes the contribution of dissimilatory sod2 reduction to alkalinity generation in these lakes was estimated conservatively to range from 1 to 75 meq m 2 yr l the contribution of both assimilatory and dissimilatory sod2reduction ranged from 10 to 159 meq m 2 yr l for lakes with water residence times on the order of years sod2 reduction can be important in controlling lake water alkalinity we found substantial quantities of inorganic reduced s in sediments of nearly all of the lakes that we studied the majority was present as pyrite in most lakes concentrations of inorganic reduced s were higher in sediments deposited in the last 85 yr when compared to older sediments in contrast the ratio of c to organic s showed no consistent trend with depth in most lakes it appears that in these lakes most of the sulfide produced from s0 2 reduction is stored primarily as inorganic forms rather than as c bonded s in lakes with highly organic sediments and low fe concentrations we found that a considerable portion of the sedimentary fe was present as ferrous sulfides if these lakes were typical alkalinity generation bv reduced s storage in lakes with organic rich sediments in the northeastern u s ilready may be limited by fe availability

sedimentary iron geochemistry in acidic waterways associated with coastal lowland acid sulfate soils abstract we examined the solubility mineralogy and geochemical transformations of sedimentary fe in waterways associated with coastal lowland acid sulfate soils class the waterways contained acidic ph 3 26 3 54 fe iii rich 27 138 m surface water with low molar cl so 4 ratios 0 086 5 73 the surficial benthic sediments had high concentrations of oxalate extractable fe iii due to schwertmannite precipitation kinetically favoured by 28 30 of aqueous surface water fe being present as the fe iii so 4 species subsurface sediments contained abundant pore water hco 3 6 20 mm and were reducing eh ii concentrations were high 2 mm and were constrained by precipitation dissolution of siderite the near neutral reducing conditions also promoted so 4 reduction and the formation of acid volatile sulfide avs the results show for the first time for class associated waterways that sedimentary avs consisted mainly of disordered mackinawite in the presence of abundant pore water fe ii precipitation dissolution of disordered mackinawite maintained very low i e ii concentrations such low concentrations of s ii caused slow rates for conversion of disordered mackinawite to pyrite thereby resulting in relatively low concentrations of pyrite 1 as fe compared to disordered mackinawite up to 590 mol g 1 as fe this study shows that interactions between schwertmannite goethite siderite disordered mackinawite and pyrite control the geochemical behaviour of sedimentary fe in class associated waterways

metal pollution of estuarine sediments caused by leaching of acid sulphate soils abstract this study tracks changes in metal distribution in estuarine sediments as a result of leakage from acid sulphate as soil landscapes in the boreal zone finland the main objective was to identify the impact of these nasty soils on sediment geochemistry in a biologically sensitive and shallow brackish water estuary in order to do this four sediment cores were sampled in a profile extending seawards from the mouth of the vora river which is one of the most heavily as soil impacted rivers in finland and europe two of the cores were rather deep 2 5 m and 4 0 m and the others were shallow 0 4 m and 0 8 m the results showed that an appreciable amount of aluminium al cobalt co cadmium cd copper cu manganese mn nickel ni and zinc zn were elevated in the surface and sub surface of the sampled bottom sediments compared to the deeper sediment background levels these metals are all known to be abundantly leached from the as soils at the site approximately 4 km away from the river mouth the concentrations of cd co mn ni and zn were elevated 5 100 times as compared to the background levels and showed an intriguing cyclic pattern most likely reflecting seasonal leaching dynamics in the as soil landscapes in contrast metals that are not abundantly leached from as soils i e chromium cr iron fe and vanadium v had consistently low concentrations throughout all sediment cores the elevated metal concentrations in the top layers of the sediments in the estuary are alarming the continuous land uplift of the region combined with the episodic rapid declines in ph may result in short and long term extensive release of metals this in turn may have significant effects on the trace metal contents in the gulf of bothnia and the entire baltic sea

quantifying alkalinity generating processes in a tidally remediating acidic wetland abstract lime assisted tidal exchange late is a new remediation technique that is demonstrably effective at decreasing acidity in coastal acid sulfate soils cass however the relative magnitude of the major in situ alkalinity generating processes and external alkalinity inputs that dominate neutralization of acidity during late have not been quantified here we combine investigations of porewater and solid phase geochemistry from a remediating cass wetland to derive first order estimates of alkalinity generating processes and inputs after 6 years of late quantified inputs include marine derived hco 3 from tidal exchange hydrated lime additions and in situ alkalinity from anaerobic metabolism of organic carbon coupled with reduction of iron and sulfate a progressive increase in tidal inundation led to the development of significant relationships 0 01 between topography and both non sulfidic solid phase fe ii and solid phase reduced inorganic sulfur species these topographic relationships were conjoined with a digital elevation model enabling up scaling of alkalinity estimates to a sub catchment level estimates indicate the relative order of importance of alkalinity generating processes and inputs is fe reduction 50 64 tidal exchange 25 42 sulfate reduction 7 13 hydrated lime addition 4 2 reduction was limited by an inability to distinguish between non sulfidic solid phase fe ii generated by microbial dissimilatory reduction of fe iii or chemical reduction of fe iii by h 2 s nevertheless the combined alkalinity contribution of these two electron accepting processes accounts for between 58 and 74 of the total the majority 99 of net alkalinity generation was due to either tides or microbial metabolism this indicates that the late remediation technique is both a cost effective means of decreasing soil acidity and is readily transferable to similar cass landscapes provided there is adequate supply of suitable electron donors and sufficient regenerative capacity in the adjacent estuarine marine tidal hco 3 pool

a 135 000 year record of vegetational and climatic change from the bandung area west java indonesia sedimentological and palynological analyses of sediment cores from the intramontane bandung basin west java indonesia provide a first palaeoclimatic record for the indonesian region covering continuously the last 135 000 years our data on palaeosol development indicate anomalously dry conditions for the final part of the penultimate glacial period around 135 000 yr b p and very warm and humid interglacial conditions from 126 000 to 81 000 yr b p during the transition to the last glacial period around 81 000 yr b p freshwater swamp forest of the bandung plain was replaced by an open swamp vegetation dominated by grasses and sedges indicating a change to considerably drier conditions possibly related to reduced moisture uptake by the nw monsoon as a consequence of lower sea levels at the onset of glacial conditions a strong reduction in asplenium ferns from 81 000 to 74 000 yr b p suggests that drier conditions may also have occurred in the mountains of the bandung area while increased numbers indicate that from 74 000 to 47 000 yr b p it was slightly wetter again inferred depression of montane vegetation zones and reduced fern percentages suggests distinctly cooler and possibly drier climatic conditions prevailed in the bandung area from 47 000 to approximately 20 000 yr b p for the last glacial maximum 4 7 c lower temperatures are recorded

iron geochemical zonation in a tidally inundated acid sulfate soil wetland abstract tidal inundation is a new technique for remediating coastal acid sulfate soils cass here we examine the effects of this technique on the geochemical zonation and cycling of fe across a tidally inundated cass toposequence by investigating toposequence hydrology in situ porewater geochemistry solid phase fe fractions and fe mineralogy interactions between topography and tides exerted a fundamental hydrological control on the geochemical zonation redistribution and subsequent mineralogical transformations of fe within the landscape reductive dissolution of fe iii minerals including jarosite kfe3 so4 2 oh 6 resulted in elevated concentrations of porewater fe2 30 mmol l 1 in former sulfuric horizons in the upper intertidal zone tidal forcing generated oscillating hydraulic gradients driving upward advection of this fe2 enriched porewater along the intertidal slope subsequent oxidation of fe2 led to substantial accumulation of reactive fe iii fractions up to 8000 mol g 1 in redox interfacial tidal zone sediments these fe iii precipitates were poorly crystalline and displayed a distinct mineralisation sequence related to tidal zonation schwertmannite fe8o8 oh 6so4 was the dominant fe mineral phase in the upper intertidal zone at mainly low ph 3 4 this was followed by increasing lepidocrocite feooh and goethite feooh at circumneutral ph within lower intertidal and subtidal zones relationships were evident between fe fractions and topography there was increasing precipitation of fe sulfide minerals and non sulfidic solid phase fe ii in the lower intertidal and subtidal zones precipitation of fe sulfide minerals was spatially co incident with decreases in porewater fe2 a conceptual model is presented to explain the observed landscape scale patterns of fe mineralisation and hydro geochemical zonation this study provides valuable insights into the hydro geochemical processes caused by saline tidal inundation of low lying cass landscapes regardless of whether inundation is an intentional strategy or due to sea level rise

sulfur biogeochemical cycling and novel fe s mineralization pathways in a tidally re flooded wetland abstract sulfur biogeochemical cycling and associated fe s mineralization processes exert a major influence over acidity dynamics electron flow and contaminant mobility in wetlands benthic sediments and groundwater systems while s biogeochemical cycling has been studied intensively in many environmental settings relatively little direct information exists on s cycling in formerly drained wetlands that have been remediated via tidal re flooding this study focuses on a tidal wetland that was drained in the 1970s causing severe soil and water acidification and subsequently remediated by controlled re flooding in 2002 we examine so 4 2 reduction rates and fe s mineralization at the tidal fringe 7 years after the commencement of re flooding the initial drainage of the wetland examined here caused in situ pyrite fes2 oxidation resulting in the drained soil layers being highly acidic and rich in so 4 2 bearing fe iii minerals including jarosite kfe3 so4 2 oh 6 tidal re flooding has neutralized much of the previous acidity with the pore water ph now mostly spanning ph 5 7 the fastest rates of in situ so 4 2 reduction up to 300 nmol cm 3 day 1 occur within the inter tidal zone in the near surface soil layers to 60 cm below ground surface the so 4 2 reduction rates correlate with pore water dissolved organic c concentrations thereby suggesting that electron donor supply was the predominant rate determining factor elemental s was a major short term product of so 4 2 reduction comprising up to 69 of reduced inorganic s in the near surface soil layers this enrichment in elemental s can be partly attributed to interactions between biogenic h2s and jarosite a process that also contributed to enrichment in pore water fe2 up to 55 mm and so 4 2 up to 50 mm the iron sulfide thiospinel greigite fe3s4 was abundant in near surface soil layers within the inter to sub tidal zone where tidal water level fluctuations created oscillatory redox conditions there was evidence for relatively rapid pyrite re formation within the re flooded soil layers however the results indicate that pyrite re formation has occurred mainly in the lower formerly drained soil layers whereas the accumulation of elemental s and greigite has been confined towards the soil surface the discovery that pyrite formation was spatially decoupled from that of elemental s and greigite challenges the concept that greigite is an essential precursor required for sedimentary pyrite formation in fact the results suggest that greigite and pyrite may represent distinct end points of divergent fe s mineralization pathways overall this study highlights novel aspects of fe s mineralization within tidal wetlands that have been drained and re flooded in contrast to normal undisturbed tidal wetlands as such the long term biogeochemical trajectory of drained and acidified wetlands that are remediated by tidal re flooding cannot be predicted from the well studied behaviour of normal tidal wetlands

vegetation and climate change in west java indonesia during the last 135 000 years abstract sedimentological and palynological analyses of two sediment cores from the intramontane bandung basin java indonesia provide the first palaeoclimatic record for the indonesian region covering the last 135 000 years our data indicate anomalously dry conditions for the penultimate glacial and very warm and humid conditions during the last interglacial during the last glacial period fresh water swamp forests of the bandung plain were replaced by open swamp vegetation dominated by grasses and sedges indicating a change to considerably drier climatic conditions possibly as a consequence of lower sea levels at the onset of glacial conditions for the last glacial maximum temperatures 4 7 c lower than at present are recorded

contemporary pedogenesis of severely degraded tropical acid sulfate soils after introduction of regular tidal inundation abstract marine tidal inundation was partially restored to a severely degraded tropical acid sulfate soil landscape after having been excluded for over 30 years the effects on soil acidity and iron sulfide mineral reformation were investigated by comparing the geochemistry of soils before and after five years of regular tidal inundation the soil ph increased by 2 3 units and titratable actual acidity taa decreased by 40 50 mol h g 1 within former sulfuric horizons relict acidity remained at depth 1 m in the underlying sulfidic horizons 34 s data indicate that tidal inundation caused exchange of marine solutes within former sulfuric horizons but not within underlying sulfidic material there was considerable reformation of pyrite within former sulfuric horizons after tidal inundation with reduced inorganic sulfur increasing by 60 mol g 1 acid volatile sulfide also accumulated but mainly near the soil surface up to 16 mol g 1 reduction of fe iii minerals strongly influences the geochemistry of the tidally inundated soils after tidal inundation the soil ph and eh closely followed the iron redox couple and there was non sulfidic solid phase fe ii up to 600 mol g 1 there was also substantial diagenetic enrichment of poorly crystalline fe oxides near the soil surface following tidal inundation with reactive fe spanning 400 1800 mol g 1 while the decreases in soil acidity documented here are likely due to a combination of marine alkalinity inputs and reduction of both fe and so 4 2 the relative importance of each process remains to be determined this study demonstrates that marine tidal inundation can be an effective landscape scale strategy for ameliorating severe acidity associated with drained acid sulfate soils

seawater inundation of coastal floodplain sediments short term changes in surface water and sediment geochemistry abstract coastal floodplains are highly vulnerable to seawater inundation as a result of storm surge and sea level rise due to their low elevation and proximity to the coastline intact soil cores from a levee acid sulfate soil scald and four backswamp sites on a coastal floodplain in eastern australia were inundated with artificial seawater treatments 0 50 and 100 for 14 days to examine the short term consequences for surface water and floodplain sediment geochemistry all sites displayed an initial decrease in surface water ph following inundation with 50 and 100 seawater in addition higher concentrations of trace metals al fe mn ni and zn were observed in most sites inundated with 50 or 100 seawater this was generally attributed to competitive exchange and desorption of trace metals from sediments due to the higher ionic strength of the seawater solutions and upward diffusive flux of metals from the sediments to surface waters at one backswamp site reductive processes had established by day 7 which also resulted in elevated fe 2 concentrations in the overlying surface waters transmission electron microscopy tem identified the presence of poorly crystalline ferrihydrite and schwertmannite and goethite and jarosite these meta stable fe iii minerals can act as a source of metals for desorption and can also be readily reduced and act as a source of fe 2 to surface waters importantly inundation with either 50 or 100 seawater resulted in a similar magnitude of acidity and trace metal mobilisation the data suggest that an inundation event of 0 2 m depth with either 50 or 100 seawater could cause a pulse mobilisation of up to 64 8 and 9 1 kg ha 1 of fe and al respectively quantities of similar magnitude to previous estimates of annual drainage fluxes from similar backswamps this study suggests that the short term inundation of coastal floodplain sediments by either brackish water or seawater will result in rapid declines in surface water quality as a result of increased liberation of acidity and trace metals

the palaeoenvironmental context of the palaeolithic of java a brief review abstract the earliest palaeolithic implements found in java island are older than 1 ma postdating the oldest homo erectus fossils the archaeological record subsequently documents acheulean like tools in early middle pleistocene deposits a diversity of flake tools assemblages found in late middle early upper pleistocene sites and the conspicuous development of cave occupations during the end of the pleistocene and the early holocene the environment mostly forested during the lower pleistocene underwent important changes during the setup of mid pleistocene climatic conditions then at the beginning of the upper pleistocene and at the boundary between mis 2 and 1 its reconstructions must also consider more local factors e g the repetitive effects of the tectonic and volcanic activities which had severe consequences on local climate on the palaeogeography and the vegetal formations or even isolation of faunistic and floristic groups examples presented here broach the context of ancient human settlements and adaptation from a multidisciplinary viewpoint that includes the study of the vegetal cover and the availability of lithic raw material the associated vertebrate faunas considered both as an environmental proxy and as a subsistence resource reflect the contrasts between periods of contact with the mainland increased biodiversity and periods of isolation favouring endemism and also the impact of local environmental constraints