productivity regime and phytoplankton size structure in the arabian sea abstract the productivity regime and size structure of phytoplankton are described for three different epipelagic systems in the arabian sea during the inter monsoon period in spring 1987 1 the coast of oman 2 the central arabian sea and 3 the shelf off pakistan these results are related to the functioning of the specific ecosystem off the coast of oman the transition from a surface maximum of autotrophic biomass and production to a more oligotrophic system with a chlorophyll subsurface maximum was observed concomitantly the size spectrum changed towards a higher significance of picoplankton in the central arabian sea a typical oligotrophic system with a pronounced subsurface maximum of autotrophic biomass and primary production was encountered here the epipelagic system could be divided into two distinct sub systems the surface layer regenerated production the predominance of picophytoplankton and minor losses due to sedimentation thus a closed system and the subsurface maximum layer at the nutricline characterized by higher sedimentation losses and more diatoms both sub systems showed about the same productivity the turnover in the surface layer having been much greater than in the subsurface maximum the system on the shelf off pakistan is seen as a decay stage of the open ocean system when water from offshore is transported onto the shelf during the onset of monsoon winds

size fractionated primary production and nitrogen assimilation in the northwestern indian ocean abstract rates of phytoplankton production and nitrogen assimilation were measured at various stations along a transect in the northwestern indian ocean from near the equator northwards into the upwelling system off the arabian peninsula during september october 1986 the measurements were made using in situ incubation techniques with the simultaneous use of 14c and 15n isotopes samples were fractionated after the incubations into three size classes 0 2 0 8 m 0 8 5 0 m and 5 0 m for the 14c incubations and 5 m for the 15n incubations the assimilation of nitrate and ammonium was measured these measurements were supported by a detailed description of the horizontal and vertical distributions of chlorophyll temperature and underwater light field by the deployment of a towed undulating oceanographic recorder rates of primary production ranged from approximately 0 5 g c m 2 day 1 at the equator reducing to 2 5 in the upwelling region off the coast of oman total nitrogen assimilation followed a similar pattern very significant variations in the size distribution of the activity of the plankton were observed over 75 of the carbon and nitrogen assimilation was in the

efficient method for coupling field data and numerical modeling for the estimation of transverse mixing coefficients in meandering rivers abstracta numerical model has been developed employing an orthogonal stream tube gridding system for the investigation of mixing patterns in meandering rivers the proposed model couples field data and modeling it uses a measured velocity field to solve the advection diffusion equation this equation provides a practical simulation with greater accuracy and lower computational cost for estimation of mixing in meandering channels with a long full mixing length the model has been used to estimate the transverse mixing coefficient in surveyed subreaches of the north saskatchewan river in canada good agreement was observed between the numerical and measured tracer concentrations using reasonable values for the transverse mixing coefficient the average dimensionless transverse mixing coefficient from the calibrated numerical model for the surveyed reach was 0 39 which was consistent with values estimated using empirical formulas for transverse mixing coefficients in natural meandering rivers the estimat

millennial scale oscillation of denitrification intensity in the arabian sea during the late quaternary and its potential influence on atmospheric n2o and global climate the intensity of denitrification in the arabian sea during the last 65 kyr is reconstructed using high resolution 15 n records of three sediment cores in conjunction with other geochemical tracers for water column oxygenation and productivity the results reveal a close link to the greenland ice core record with low or absent water column denitrification during the last glacial maximum the stadials and at the time of the heinrich events including the younger dryas in contrast denitrification was high during the holocene and the interstadials the intensification of denitrification is related to stronger sw monsoonal upwelling which enhances organic matter flux and degradation resulting in a strengthening of the midwater oxygen deficiency such a combination of enhanced upwelling and denitrification has also been implied for the eastern tropical north pacific etnp where these events occur during the holocene and to some extent during the interstadials too today the arabian sea and the etnp together contribute substantially to the global marine water column denitrification and a significant fraction of the ocean atmosphere n 2 o flux originates from these areas changes in n 2 o emissions from these areas could thus have effected the recently described stadial interstadial variations in the atmospheric concentration of this greenhouse gas as deduced from ice cores moreover denitrification is the major sink for oceanic nitrate and provides a primary control for the oceanic nutrient inventory which in turn influences global primary productivity and co 2 sequestration by the biological pump short term switches between a nondenitrification mode and a denitrification mode in these marine regions therefore have an impact on global climate

strontium isotope quantification of siderite brine and acid mine drainage contributions to abandoned gas well discharges in the appalachian plateau unplugged abandoned oil and gas wells in the appalachian region can serve as conduits for the movement of waters impacted by fossil fuel extraction strontium isotope and geochemical analysis indicate that artesian discharges of water with high total dissolved solids tds from a series of gas wells in western pennsylvania result from the infiltration of acidic low fe fe 10 mg l coal mine drainage amd into shallow siderite iron carbonate cemented sandstone aquifers the acidity from the amd promotes dissolution of the carbonate and metal and sulfate contaminated waters rise to the surface through compromised abandoned gas well casings strontium isotope mixing models suggest that neither upward migration of oil and gas brines from devonian reservoirs associated with the wells nor dissolution of abundant nodular siderite present in the mine spoil through which recharge water percolates contribute significantly to the artesian gas well discharges natural sr isotope composition can be a sensitive tool in the characterization of complex groundwater interactions and can be used to distinguish between inputs from deep and shallow contamination sources as well as between groundwater and mineralogically similar but stratigraphically distinct rock units this is of particular relevance to regions such as the appalachian basin where a legacy of coal oil and gas exploration is coupled with ongoing and future natural gas drilling into deep reservoirs

seasonality in the hydrography and biogeochemistry across the pakistan margin of the ne arabian sea abstract a series of cruises were conducted across the pakistan continental shelf edge and upper slope in the ne arabian sea between march and october 2003 coinciding with spring inter monsoon and late to post sw monsoon conditions water column hydrographic profiling together with nutrient chemistry show the upper boundary of the oxygen minimum zone omz rose during the sw monsoon by approximately 80 m leading to an inundation of a substantial area of the continental shelf with low oxygen water while the lower boundary showed only slight movement the core of the omz identified by the presence of a secondary nitrite maximum and high nitrate deficits rose by approximately 200 m nitrite concentrations within the secondary nitrite maximum approximately doubled over the period of study but this was not matched with an increase in the nitrate deficit dissolved oxygen concentrations in the core of the omz showed little or no substantial change during the course of the study hydrographic profiling showed greatest change in water masses around the 200 600 m depth range probably resulting from the northward movement of the west india undercurrent

nitrous oxide in the deep waters of the world s oceans we present a compilation and analysis of n2o data from the deep water zone of the oceans below 2000 m the n2o values show an increasing trend from low concentrations in the north atlantic ocean to high concentrations in the north pacific ocean indicating an accumulation of n2o in deep waters with time we conclude that the observed n2o accumulation is mainly caused by nitrification in the global deep water circulation system i e the conveyor belt hydrothermal and sedimentary n2o fluxes are negligible we estimate the annual n2o deep water production to be 0 3 0 1 tg despite the fact that the deep sea below 2000 m represents about 95 of the total ocean volume it contributes only about 3 16 to the global open ocean n2o production a rough estimate of the oceanic n2o budget suggests that the loss to the atmosphere is not balanced by the deep sea nitrification and pelagic denitrification therefore an additional source of 3 8 tg n2o yr 1 attributed to nitrification in the upper water column 0 2000 m might exist with a simple model we estimated the effect of changes in the north atlantic deep water nadw formation for deep water n2o the upper water n2o budget is not significantly influenced by variations in the n2o deep water formation however the predicted decrease in the nadw formation rate in the near future might lead to an additional source of atmospheric n2o in the range of about 0 02 0 4 tg yr 1 this anthropogenically induced source is small and it will be difficult to detect its signal against the natural variations in the annual growth rates of tropospheric n2o

transverse mixing in an unregulated northern river transverse mixing in an unregulated northern river in canada was studied in different discharge conditions with and without ice cover the distribution of cumulative discharge was constructed on the basis of river cross sectional shapes and a modified streamtube method was proposed to describe transverse mixing the modified method only uses raw field data to calibrate the modeled concentration profiles and thus can produce a reliable mixing coefficient even with relatively low quality field data the effects of river discharge and ice cover on the transverse mixing coefficient were examined in a fixed study reach it was found that the transverse mixing coefficient increased approximately linearly with river discharge from 84 to 960 m3 s the dimensionless transverse mixing coefficient scaled with river shear velocity and river depth appeared unaffected within 14 by the river discharge in both open water and ice covered conditions and its value was 21 smaller in the ice covered condition than

the global impact of the minoan eruption of santorini greece the minoan eruption of santorini was a large magnitude natural event however in terms of scale it ranks smaller in erupted volume and eruptive intensity than the historical eruption of tambora in 1815 ad and smaller in sulphur emission and by inference climatic effects than both the tambora and mt pinatubo 1991 eruptions eruption statistics for the past 2000 years indicate that minoan size eruptions typically occur at a rate of several per thousand years eruptions resulting in a minoan scale injection of sulphur to the stratosphere occur far more frequently at a rate of one or two per century inferences of massive sociological religious and political impacts from such eruptions owe more to mythology than reality

residential mobility and social identity in the periphery strontium isotope analysis of archaeological tooth enamel from southeastern arabia a b s t r a c t strontium isotope analysis represents an effective means of assessing mobility and reconstructing geographic residence patterns in archaeological populations this biogeochemical technique was utilized to test the hypothesis that burgeoning interregional exchange networks and the occurrence of exotic grave goods in local tombs would correspond with a highly mobile population and a considerable immigrant presence during the umm an nar 2700e2000 bc period in the uae this region has been considered peripheral relative to larger civilizations in mesopotamia and the indus valley but played an important role as a major supplier of copper for the persian gulf individuals n 100 from six monumental umm an nar tombs mowaihat tell abraq umm an nar island i ii v unar 1 were selected to evaluate the geographic origins of tomb members mean 87 sr 86 sr ratios from local individuals interred at mowaihat 0 708863 0 000014 1s n 12 tell abraq 0 708873 0 000020 1s n 27 umm an nar island 0 708902 0 000079 1s n 33 and unar 1 0 708805 0 000065 1s n 25 all display little isotopic variability indicative of a population that was not highly mobile however coupled with archaeological evidence three immigrants from tell abraq n 2 and mowaihat n 1 identi ed by deviant strontium values suggest that this region was actively engaged in interregional interaction despite claims that these tombs acted as visible markers of territoriality legitimized by local ancestors buried within them the presence of non locals suggests that as commerce became increasingly important de nitions of kinship and social identity may have become more exible to better meet the needs of the local community and those with whom they interacted

water masses in the humboldt current system properties distribution and the nitrate deficit as a chemical water mass tracer for equatorial subsurface water off chile abstract three sections are used to analyze the physical and chemical characteristics of the water masses in the eastern south pacific and their distributions oceanographic data were taken from the scorpio may june 1967 piquero may june 1969 and krill june 1974 cruises vertical sections of temperature salinity dissolved oxygen nitrate nitrite phosphate and silicate were used to analyze the water column structure five water masses were identified in the zone through t s diagrams subantarctic water subtropical water equatorial subsurface water antarctic intermediate water and pacific deep water their proportions in the sea water mixture are calculated using the mixing triangle method vertical sections were used to describe the geographical distributions of the water mass cores in the upper 1500 m several characteristic oceanographic features in the study area were analyzed the shallow salinity minimum displacement towards the equator the equatorial subsurface salinity maximum associated with a dissolved oxygen minimum zone and a high nutrient content displacement towards the south and the equatorward intermediate antarctic salinity minimum associated with a dissolved oxygen maximum the nitrate deficit generated in the denitrification area off peru and northern chile is proposed as a conservative chemical tracer for the equatorial subsurface waters off the coast of chile south of 25 s

nitrogen biogeochemical cycling in the northwestern indian ocean abstract the vertical distribution and fine scale structure of nitrate no 3 nitrite no 2 nitrous oxide n 2 o phosphate po 4 oxygen o 2 and chlorophyll chl were determined in the north western indian ocean nwio along a meridional section 67 e from the equator to the gulf of oman using an autoanalyser for micromolar levels of nutrients and chemiluminescence and gas chromatographic methods for nanomolar levels of no 3 and no 2 and n 2 o respectively three biogeochimically contrasting regimes were investigated 1 the highly oligotrophic nutrient depleted subtropical gyre 2 the nonsoonal upwelling of nutrient rich intermediate waters of the southeastern arabian coast and 3 the denitrifying o 2 depleted zone odz ca 150 1200 m depth in the arabian sea concentrations of no 3 and no 2 were severely depleted in surface oligotrophic waters from the equator average 43 and 3 6 nm respectively to the subtropical gyre 12 15 n average 13 3 and 2 0 nm respectively with similar levels in the more stratified gulf of oman upwelling waters off southern arabia had three orders of magnitude higher no 3 levels and throughout the nwio the calculated no 3 fuelled primary production appeared to be regulated by no 3 concentration existing redfield o 2 no 3 regeneration ratios 9 1 previously derived for the deep indian ocean were confirmed 9 35 within the oxic upper layers of the nwio the no potential temperature relationship broecker 1974 earth and planetary science letters 23 100 107 needed for the derivation of expected no 3 and no 3 deficits within the denitrifying odz were refined using an isopycnal binary mixing model along the 26 6 density layer to take into account the inflowing contribution of no 3 depleted persian gulf water vertically integrated no 3 deficits increased northwards from 0 8 mol no 3 n m 2 at sta 2 04 n up to 6 49 mol no 3 n m 2 at sta 9 at the mouth of the gulf of oman then decreased to 4 10 moles no 3 n m 2 toward sta 11 near the straits of hormuz when averaged for the denitrification area of the arabian sea this corresponds to a deficit of 118 tg no 3 n adopting a recent freon 11 based estimate of water residence time of 10 years olson et al 1993 deep sea research ii 40 673 685 for the o 2 depleted layer we calculate an annual net denitrification flux of 11 9 tg n to the atmosphere or approximately 10 of the global water column denitrification rates supersaturated n 2 o concentrations were found in both surface oxic and upwelling waters up to 246 and peaked at the base of the odz up to 1264 in the northern arabian sea both nitrification in oxic waters and denitrification in hypoxic layers can be invoked as sources of n 2 o the inventory of excess n 2 o amounted to 2 55 1 3 tg n 2 o n corresponding to annual production of 0 26 0 13 tg from denitrification this is comparable to earlier law and owens 1990 nature 346 826 828 estimates of the ventilation flux of n 2 o 0 22 0 39 tg yr 1 from the upwelling region of the arabian sea the decadal response times for circulation deoxygenation denitrification and ventilation of the odz derived n 2 o and co 2 greenhouse gases and their monsoonal coupling implies the arabian sea is a sensitive oceanic recorder of global climate change

coal fly ash interaction with environmental fluids geochemical and strontium isotope results from combined column and batch leaching experiments abstract the major element and sr isotope systematics and geochemistry of coal fly ash and its interactions with environmental waters were investigated using laboratory flow through column leaching experiments sodium carbonate acetic acid nitric acid and sequential batch leaching experiments water acetic acid hydrochloric acid column leaching of class f fly ash samples shows rapid release of most major elements early in the leaching procedure suggesting an association of these elements with soluble and surface bound phases delayed release of certain elements e g al fe si signals gradual dissolution of more resistant silicate or glass phases as leaching continues strontium isotope results from both column and batch leaching experiments show a marked increase in 87 sr 86 sr ratio with continued leaching yielding a total range of values from 0 7107 to 0 7138 for comparison the isotopic composition of fluid output from a fly ash impoundment in west virginia falls in a narrow range around 0 7124 the experimental data suggest the presence of a more resistant highly radiogenic silicate phase that survives the combustion process and is leached after the more soluble minerals are removed strontium isotopic homogenization of minerals in coal does not always occur during the combustion process despite the high temperatures encountered in the boiler early released sr tends to be isotopically uniform thus the sr isotopic composition of fly ash could be distinguishable from other sources and is a useful tool for quantifying the possible contribution of fly ash leaching to the total dissolved load in natural surface and ground waters

strontium isotopic characterization of soils and coal ashes abstract the 87 sr 86 sr isotopic ratios and rb and sr concentrations were measured for a number of soils and samples of coal derived fly and bottom ashes fly and bottom ashes from a given coal rank are similar in their concentrations of rb and sr and their 87 sr 86 sr ratios values of 87 sr 86 sr isotopic ratios of ashes decrease in the order bituminous subbituminous lignitic reflecting the decreasing rank of parent coals the 87 sr 86 sr isotopic ratios of soils vary widely differing significantly only from the ratios observed for lignitic ashes the results indicate that the 87 sr 86 sr values may be used as a tracer for detecting dispersion of lignitic ashes on soils in these coal ashes the 87 sr 86 sr ratios of the biogeologically available fraction of sr are linearly correlated with the logarithm of the sr concentrations the logarithm of the rb sr ratios and the rb concentrations

tracing the interaction of acid mine drainage with coal utilization byproducts in a grouted mine strontium isotope study of the inactive omega coal mine west virginia usa abstract in order to ameliorate acidic discharge the inactive omega coal mine west virginia was partially filled by injection of a grout consisting of 98 coal utilization byproducts cub including fluidized bed combustion ash and fly ash and 2 portland cement in this study discharge chemistry and sr isotope ratios were determined to identify and quantify the extent of interaction between mine waters and the cub cement grout eight sampling sites were monitored around the downdip perimeter of the mine the major and trace element chemistry of the discharges was generally not sufficient to distinguish between discharges that interacted with grout and those that did not elements that showed the most separation include k and as which were elevated in some waters that interacted with cub cement grout in contrast the sr isotope ratios clearly distinguished discharges from grouted and non grouted areas discharges that bypassed the grouted portions had 87 sr 86 sr ratios ranging from 0 71510 to 0 71594 while two discharges that interacted with grout had ratios in the range of 0 71401 0 71456 the treatment inlet which includes both grouted and ungrouted discharges yielded intermediate isotopic ratios leaching experiments on cub cement grout coal and surrounding rocks are consistent with the isotopic trends observed in the discharges based on these results waters that interacted with grout received 30 40 of their sr from the cub cement grout material these results suggest that the grout material is chemically eroding at a rate of approximately 0 04 per year this novel application of the sr isotope system illustrates its ability to sensitively track and quantify fluid interaction with coal and cub based grout

strontium isotopes as tracers of airborne fly ash from coal fired power plants fly ash generated by coal fired power plants is in part collected by filters in the emission stacks while a small portion is vented into the atmosphere since many of the coalfired power plants in the western united states are located in the desnrt the ability to monitor fly ash emissions requires a chemical tracer that utilizes desert soil and plant interactions with the fly ash deposited in the desert environment this investigation presents the results of a controlled greenhouse experiment in which a native desert plant the brittlebush encelia farinosa was grown on admixtures of desert soils and fly ash the fly ash is strongly enriched in sr and the brittlebush is a sr accumulator the data demonstrate that 1 the brittlebush isotopically equilibrates with desert soils whose fly ash components are as low as 0 25 by weight 2 the fly ash sr is apparently more available to the plant than sr derived from the soils and 3 the difference between the87sr 86sr ratio of the fly ash 0 70807 and soils 0 71097 to 0 71117 warrants further investigations in the natural environment to determine the practicality of this method as a natural tracer of fly ash in the environment

radiogenic isotopes systematics and applications to earth surface processes and chemical stratigraphy radiogenic isotopes have wide application to chemical stratigraphy geochronology provenance studies and studies of temporal changes in earth surface processes this paper briefly reviews the principles of radiogenic isotope geochemistry and the distribution of a number of elements of interest in the environment and then uses this information to explore the range of applications to chemical stratigraphy and other fundamental subjects of sedimentary geology many of these applications center on the reconstruction of secular variations in paleoseawater isotope signals these seawater isotope curves can be used for stratigraphic correlation and to assess changes through earth history in processes such as tectonic uplift climate change biogeochemical cycling ocean circulation crustal growth and surface water evolution understanding the modern biogeochemical cycle of the element isotope system of interest is essential for gaining the maximum information regarding the operation of ancient cycles the main sources of uncertainty for reconstructing seawater isotope curves involve diagenetic alteration sample impurities and errors in age assignments rigorous sample selection criteria and pretreatment methods are keys to reconstructing the most accurate seawater isotope curves applications are discussed for the rb sr sm nd la ce lu hf re os u th pb k ar and cosmogenic isotope systems d 2003 elsevier b v all rights reserved

an intermediate nepheloid layer associated with high microbial metabolic rates and denitrification in the northwest indian ocean extensive optical physical chemical and biochemical measurements made simultaneously in the northwest indian ocean reveal the occurrence of an intermediate nepheloid layer inl invariably associated with the secondary nitrite maximum maxima in particulate protein and the activity of the respiratory electron transport system ets are also found within the inl since the inl persists long distances from the continental margin with an offshore intensification it may not be related to the transport of material resuspended along the continental margin an apparent correlation of the inl with the previously reported subsurface maximum in bacterial abundance suggests that a local increase in the abundance of bacteria may be responsible for the increased turbidity positive correlations of the beam attenuation anomaly with nitrite and nitrate deficit suggest that most of these bacteria may be denitrifiers the organic carbon demand within the denitrifying layer computed from the observed ets activity appears to be severalfold higher than the sinking carbon fluxes to the denitrifying layer requiring additional modes of supply of the biodegradable organic matter it is proposed that a bacterial maximum could be maintained with efficient utilization of the dissolved organic matter within the denitrifying waters

pb and sr isotopic evidence for sources of atmospheric heavy metals and their deposition budgets in northeastern north america concentrations of al ba cd cu mg mn pb rb sr and zn as well as pb and sr isotopic compositions were determined in samples of snowpack obtained during the 1998 winter season from northeastern north america median enrichment factors relative to upper crustal abundances for cd cu mn pb and zn for all samples range from ca 50 to 36 000 and are indicative of an anthropogenic origin the pb isotope ratios correlate with geographic location because snowpack from eastern ontario and the northeastern usa are characterized by the most radiogenic 206pb 207pb ratios ca 1 18 1 19 and these decrease systematically in an easterly direction towards the atlantic coast ca 1 16 the pb isotope data for the 1998 samples of snowpack indicate that atmospheric pollution in this region of north america is dominated solely by a mixture of anthropogenic emissions from us 206pb 207pb ca 1 20 and canadian 206pb 207pb ca 1 15 sources this result contrasts with that obtained for 1997 snowpack from similar geographic regions because the pb isotope data for the latter suggest the involvement of an additional anthropogenic component possibly that of eurasian pollution transported over the high arctic this difference in the distribution pattern of atmospheric pollution over northeastern north america between the 1997 and 1998 winter seasons may be related to the el nino phenomenon sr isotope data for all the 1998 snowpack samples define a large range in 87sr 86sr values but most are between 0 709 to 0 710 similar to the value of present day seawater ca 0 7092 however the majority of snowpack samples from eastern ontario are characterized by lower 87sr 86sr ratios 0 709 and these correlate negatively with their enrichment factors of pb such trends suggest the presence of a relatively unradiogenic source of anthropogenic sr possibly related to emissions from coal fired power plants located in the western and midwestern regions of the usa annual depositional budgets estimated from 1998 snowpack indicate that those for pb cd and cu are highest in eastern ontario and significantly lower in the remaining regions the former reflect a meteorological corridor in northeastern north america which coincides with heavily industrialized and densely populated areas depositional budgets of zn are extremely high in all areas investigated and their exact source s remains enigmatic these may reflect either an increase in atmospheric industrial emissions since the 1980s a lower residence time in the atmosphere or particular chemical speciation that affects the deposition of zn from the lower troposphere depositional budgets for mn are also high and may be related to the combustion of mn bearing fossil fuels by automotive vehicles

strontium isotopes as tracers of coal combustion residue in the environment we evaluated the application of sr isotopes as tracers of coal combustion residues in the environment strontium isotopes unlike light stable isotopes do not fractionate and can be used to monitor interactions between coal combustion residue and hydrogeologic systems the primary objective of this investigation was to determine if sr isotopes could detect the presence of flyash and other effluents produced by coal combustion in the environs surrounding a coal fired power plant in the southwestern united states analyses of coal flyash and bottom ash indicated a 87sr 86sr range of 0 70883 to 0 70972 for these residues this range in87sr 86sr exceeds the error of an individual analysis 0 00002 and represented our criteria to establish evidence for impact i e any sample whose 87sr 86sr ratio lies within this range received sr from fossil fuel ff residue natural background materials groundwater soil rocks have87sr 86sr ratios which exceed 0 710 and are therefore markedly distinct from the ff residue our analytical techniques were developed to selectively leach the flyash derived sr from soils this makes the detection of trace quantities 0 1 of ff residue possible soil sr leachate analyses suggest that ff residues have impacted on site soils to depths of 51 5 15 5 m the 87sr 86sr ratios of soil leachates below a ff waste evaporation pond lie within the range of the ff residue this supports our selection of the sr isotopic range defined by the ff residue as our criteria for impact off site soil analyses show that surface 0 1 cm soils collected from as far as 12 5 km in all geographic directions have interacted with flyash detailed analyses of deeper soils 1 5 cm 5 10 cm indicate that flyash impact varies with depth plants such as the brittlebush growing on such soils uptake sr from both the flyash and soil their 87sr 86sr ratios represent mixtures of the two components our data suggest that groundwater has not been severely impacted by ff residue in most cases waste evaporation pond waters are more commonly impaired temporal variations in the 87sr 86sr ratios of groundwater and waste evaporation pond water were observed the data may be used to assess the quality of these waters over time

case study intermediate field mixing for a bank discharge in a natural river the intermediate field mixing characteristics of the gold bar wastewater treatment plant effluent into the north saskatchewan river at edmonton were evaluated this region may be considered to be the early part of the transverse mixing region where local channel characteristics are important an extensive field study was conducted to delineate the bathymetry of the study area and evaluate the mixing characteristics by means of a steady state dye test the topographic and limited velocity results of the field study were used to create and validate a depth averaged hydrodynamic model of the study reach in order to extract streamtube information the results from the hydrodynamic model were used to interpret the mixing characteristics of the study reach as well as extract channel characteristics from the analysis it is evident that the distribution of effective transverse mixing coefficient is highly dependent on local river conditions the use of the hydrodynamic model to extract channel characteristics provided a reasonable estimate of mixing characteristics without requiring detailed field velocity data the trade off is more detailed bathymetry data is required to have a realistic model plume averaged channel characteristics rather than cross sectional averaged were shown to produce more realistic transverse mixing coefficients assumed gaussian profile distributions were successfully applied suggesting that for a bank discharge if the maximum bank concentration and mass flux are known this technique could be applied

chemical oceanography of the persian gulf abstract measurements of basic hydrographic properties nutrient elements alkalinity and total carbon dioxide were made in the persian gulf in february and march 1977 on r v atlantis ii cruise 93 the results show clearly the penetration into the gulf of surface indian ocean water initially of 36 5 salinity which is carried northwards along the iranian coast gradually increasing in salinity to more than 40 the inflowing surface water is high in phosphate 1 0 0 5 moles kg 1 due to upwelling induced by the north east monsoon however nitrate levels are at or below the detection limit and nitrogenous nutrients appear to be limiting the seawater carbonate system is greatly perturbed by the precipitation of large quantities of calcium carbonate the alkalinity salinity relationship shows that the greatest carbonate loss occurs in the shallow waters of the trucial coast where up to 125 moles kg 1 of caco3 have been lost from the water dense saline low specific alkalinity water formed in the shallows appears to migrate down slope to augment the outflowing waters in the deeper part of the gulf the outflow of the tigris euphrates and karun rivers to the north provides an intense but low capacity signal of low salinity high specific alkalinity waters large amounts of co2 are also fixed by photosynthetic processes the classical mediterranean type of circulation is plainly revealed the residence time of water within the persian gulf is approximately 2 5 yr

geochemical estimates of denitrification in the arabian sea and the bay of bengal during woce high quality world ocean circulation experiment woce data are used in conjunction with an isopycnal mixing model to calculate nitrate deficits due to denitrification in the oxygen minima of both the arabian sea and the bay of bengal basin scale integral denitrification rates are estimated by combining the nitrate deficits with water mass ages computed for the same regions based on the chlorofluorocarbon cfc 11 distributions nitrate deficits exceeding 12 mol kg 1 are observed for the arabian sea during the 1995 southwest monsoon the estimated basin scale nitrate deficit integrated over the oxygen minimum layer is 63 20 tg n and the annual loss rate is 21 7 tg n y 1 the basin scale nitrate deficit is about half other recent inventory estimates with most of the discrepancy in the bottom half of the oxygen minimum below the secondary nitrite maximum no signature of active water column denitrification was observed in the bay of bengal during the 1995 northeast monsoon

climatically linked oscillations in arabian sea denitrification over the past 1 m y implications for the marine n cycle water column and core top 15n data show that arabian sea denitrification produces large nitrogen isotopic enrichments that are regionally recorded with fidelity in the sediments these results facilitate interpretation of a 1 m y 15n record for ocean drilling program site 722b on the owen ridge in terms of climatically linked oscillations in denitrification at the major orbital periods as at present denitrification was greatest during interglacial periods and apparently was not active during most glacial intervals cross spectral analysis of 15n with foraminiferal 18o global climate sea level index and lithogenic grain size monsoon strength index suggests forcings by changes in hydrography and productivity acting through the extent and intensity of the oxygen minimum zone the data suggest that denitrification may be an internal forcing mechanism for climate change during major glacial interglacial transitions through influence on marine n inventory and atmospheric co2 however compensation or amplification may occur from other sinks sediment denitrification or sources nitrogen fixation