Major Ion Chemistry in a Freshwater Coastal Lagoon from Southern Brazil (Mangueira Lagoon): Influence of Groundwater Inputs   总被引：1，自引：0，他引：1  

Isaac R. Santos  Maria I. Machado  Luis F. Niencheski  William Burnett  Idel B. Milani  Carlos F. F. Andrade  Richard N. Peterson  Jeffrey Chanton  Paulo Baisch 《Aquatic Geochemistry》2008,14(2):133-146

This paper characterizes major ion distributions and investigates whether groundwater exerts a major control on the chemical functioning of Mangueira Lagoon, a large (90 km long), shallow (∼4–5 m deep), and fresh coastal lagoon in southern Brazil. Water volumes equivalent to ∼80% of the total annual input are used in the summer for irrigating nearby rice plantations, the most important regional economic activity. While Na⁺ and Cl⁻ are the major ions in local groundwater, Na⁺ and HCO₃⁻ are the most enriched ions in lagoon water. The ion concentrations measured in Mangueira Lagoon were homogeneous, except for a few samples affected by rainwater and groundwater inputs. A shore-normal transect starting at the pump house of a rice irrigation canal indicated strong groundwater input at this canal. In spite of the small volume contribution (∼2% of precipitation), groundwater discharge accounts for 50–70% of major ion inputs into the lagoon, with ∼70% of the groundwater inputs being anthropogenically derived (e.g., from the rice irrigation canals). This may have serious implications for the management of the coastal water resources from Mangueira Lagoon and other similar areas as groundwater associated with agricultural systems may be contaminated by fertilizers and pesticides. The results imply that groundwater should not be neglected in dissolved species’ budgets even when its volume contribution is small.  相似文献   

Recent pollen spectra and zonal vegetation in the western USSR     

G. M. Peterson 《Quaternary Science Reviews》1983,2(4)

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Interannual fluctuations in the density of sand lance,Ammodytes americanus,larvae in Long Island Sound, 1951–1983     

Doreen M. Monteleone  William T. Peterson  George C. Williams 《Estuaries and Coasts》1987,10(3):246-254

Enumeration data from over 2,300 ichthyoplankton samples collected during 17 yr, spanning a 32-yr interval (1951–1983), were compiled to determine interannual variations in density of sand lance larvae. Years of relatively high densities were noted during the winters of 1965–1966 and 1978–1979 and low densities in 1971–1974. A regular increase in numbers during the late 1970’s and the peak in 1978–1979 coincided with increases in population size found throughout the coastal northwest Atlantic Ocean. Densities in Long Island Sound began to decline in 1980 and this continued through 1983. In contrast, densities throughout coastal Atlantic areas during the 1980’s remained at least as high as they were 1976–1978. Interannual fluctuations in density of sand lance larvae could be partially explained by water temperatures in December. Warm Decembers were associated with low larval densities.  相似文献   

Racemization of amino acids in marine sediments determined by gas chromatography     

Keith A. Kvenvolden  Etta Peterson  Jon Wehmiller  P.E. Hare 《Geochimica et cosmochimica acta》1973,37(10):2215-2225

Ratios of d- to l-amino acids in acid hydrolysates from foraminifera of two deep-sea cores from the Caribbean Sea and Atlantic Ocean increase with depth and consequently with age over a span from 40,000 to 2,000,000 yr. The changing ratios do not seem to follow first-order reversible rate laws. Valine, leucine and glutamic acid apparently racemize (isoleucine epimerizes) at slower rates than do phenylalanine, alanine, aspartic acid and proline. The general relative order for rates of racemization of total (free and bound) amino acids may depend on the electron-withdrawing capacity of the R substituents of the amino acids and on the rates with which the amino acids are naturally hydrolyzed. In contrast to the total amino acids, the free amino acids in these samples are more extensively racemized, probably as a result of various catalytic and hydrolytic reactions.Previous related work based on ion-exchange chromatography has considered only ratios of alloisoleucine to isoleucine. With the gas chromatographic method used here, d/l ratios of all common asymmetric amino acids can be estimated. Measurement of the extent of racemization of amino acids in marine sediments seems to provide the basis for a geochronological tool covering the last few million years.  相似文献   

Zircon trace element chemistry at sub-micrometer resolution for Tarawera volcano,New Zealand,and implications for rhyolite magma evolution     

Sonja Storm  Axel K. Schmitt  Phil Shane  Jan M. Lindsay 《Contributions to Mineralogy and Petrology》2014,167(4):1-19

Zoned crystals can be important recorders of magmatic processes in space and time. However, in most situations, the temporal dimension is difficult to quantify. Here, we have employed secondary ion mass spectrometry depth profiling to excavate parallel pits into non-polished crystal faces of zircon to obtain ~5 μm resolution U–Th disequilibrium ages (one pit) that can be correlated with trace element zoning at sub-μm resolution derived from a second pit. Data from 17 crystals representing each of the four rhyolite eruptions of Tarawera volcano, an intra-caldera edifice within the Okataina Volcanic Centre, reveal diverse zircon growth conditions over time. Most crystals display rimward depletions in Zr/Hf and Ti, broadly consistent with cooling and crystallization. However, a significant fraction of crystals lacks these patterns and displays rimward trace element variations consistent with isothermal or prograde crystallization. Oscillatory zonation patterns in Y, Th, and U are superimposed on the Zr/Hf and Ti trends. Despite the limited number of crystals analyzed in this way, the striking lack of ubiquitous trace element zoning patterns in crystals from the same hand sample implies that fractional crystallization upon cooling was punctuated by magma recharge and crystal mixing affecting different parts of the magma reservoir. By combining data from all crystals, a systematic change to more heterogeneous trace element abundances is revealed by zircon crystal domains <45 ka following the Rotoiti caldera-forming eruption. This contrasts with the more uniform conditions of zircon crystallization lasting >100 ka prior to caldera formation and is best explained by the post-caldera system consisting of small, isolated melt pockets that evolved independently. An important conclusion is that the zircon ‘cargo’ in volcanic rocks reflects thermally and compositionally divergent processes that act near simultaneously in a magma storage region and not exclusively the conditions in the eruptible magma.  相似文献   

Seasonal Cycle of Phytoplankton Community Composition in the Coastal Upwelling System Off Central Oregon in 2009   总被引：1，自引：0，他引：1  

Xiuning Du  William T. Peterson 《Estuaries and Coasts》2014,37(2):299-311

Coastal upwelling in the northern California Current varies seasonally, with downwelling in winter and upwelling in summer, resulting in pronounced variability in hydrography, nutrients, phytoplankton biomass, and species composition. Winter was characterized by moderate concentrations of nitrate and silicate (averages of 10 and 18 μM, respectively) and low concentrations of chlorophyll a (Chl a). During the upwelling season, concentrations of the same nutrients ranged from near 0 μM to approximately 27 and 43 μM and Chl a 0.5?<?x?<?15 μg L^?1. During autumn, upwelling weakened and nutrient concentrations were reduced, but large phytoplankton blooms continued to occur. Variations in hydrography, nutrients, and phytoplankton also occurred within the upwelling season due to alternation of the winds between northerly (active upwelling) and southerly (relaxation of upwelling), on a 5- to 10-day time scale. Eleven blooms were observed, most of which occurred near the end of active upwelling events and during relaxation of upwelling. Nonmetric multidimensional scaling ordination of species composition of the microplankton revealed four distinct communities: a winter community, early upwelling and late upwelling season communities, and an autumn community. Diatoms (Asterionellopsis glacialis, Eucampia zodiacus, and several Chaetoceros, Thalassiosira, and Pseudo-nitzschia species) dominated early in the upwelling season, averaging 80 % of the phytoplankton biomass, and dinoflagellates dominated near the end of the upwelling season, averaging 68 % of the phytoplankton biomass. Dinoflagellates formed two monospecific blooms—Prorocentrum gracile in late summer and Akashiwo sanguinea in autumn. Changes in community composition were correlated with bottom temperature and salinity (representing seasonal variability) and sea surface salinity (representing within-season event-scale variability in upwelling).  相似文献   

Variability of Stable Isotope Fingerprints of the Serpulid Ficopomatus enigmaticus Within a Permanently Stratified Estuary: Implications for (Palaeo)environmental Interpretations     

Sonja Lojen  Marijana Cukrov  Neven Cukrov 《Estuaries and Coasts》2014,37(2):436-448

This paper examines how the mixing of freshwater and seawater, and related mixing of freshwater and marine particulate organic matter (POM) in the permanently stratified estuary of the River Krka, Croatia, are reflected in the stable isotope fingerprints of soft tissues and tubes of the serpulid Ficopomatus enigmaticus. The carbon stable isotope composition (δ¹³C values) of the river-borne POM is retained over long distances, causing a depletion in ¹³C of POM in brackish waters. A trophic depletion in ¹³C was recorded in serpulid soft tissues. The serpulid carbonate tubes were depleted in ¹³C even at locations with salinity close to that of the sea and were subject to large isotope fractionation between dissolved inorganic C (DIC) and carbonate caused by vital effects, making carbonate depleted in ¹³C by several per mil compared with DIC. These effects, though large in the freshwater zone, fade towards the sea. The carbonate δ¹⁸O values of tubes reflect the δ¹⁸O values of the water. The temperature-related differences in δ¹⁸O values of tubes from different sites are masked by source-related differences in the δ¹⁸O values of water arising from mixing of freshwater and seawater in the estuary. Therefore, in serpulide tubes, the terrestrial component can easily be overestimated because of vital effects during biomineralisation and trophic depletion in ¹³C in freshwater and brackish environments.  相似文献   

Natural Radon and Radium Isotopes for Assessing Groundwater Discharge into Little Lagoon,AL: Implications for Harmful Algal Blooms     

Ni Su  William C. Burnett  Hugh L. MacIntyre  Justin D. Liefer  Richard N. Peterson  Richard Viso 《Estuaries and Coasts》2014,37(4):893-910

Naturally occurring isotopes of radon (²²²Rn) and radium isotopes (^{223,224,226,228}Ra) were used as tracers to assess submarine groundwater discharge (SGD) into Little Lagoon, AL (USA), a site of recurring harmful algal blooms (HABs). The radium isotopic data suggests that there are two groundwater sources of these tracers to the lagoon, a shallow (A1) and deeper (A2) aquifer. We estimated the fraction of each source via a three-end-member mixing model consisting of Gulf of Mexico seawater, shallow and deep groundwater. The estimated lagoonwide SGD rates based on a radium mass balance and the mixing model were 1.22?±?0.53 and 1.59?±?0.20 m³ s^-1 for the shallow and deep groundwater discharges, respectively. To investigate temporal variations in SGD, we performed several radon surveys from 2010 through 2012, a period of generally declining groundwater levels due to a drought in the southeastern USA. The total SGD rates based on a radon mass balance approach were found to vary from 0.60 to 2.87 m³ s^-1. We observed well-defined relationships between nutrients and chlorophyll-a in lagoon waters during a period when there was an intense diatom bloom in April 2010 and when no bloom existed in March 2011. A good correlation was also found between radium (groundwater-derived) and nutrients during the April 2010 period, while there was no clear relationship between the same parameters in March 2011. Based on multivariate analysis of chemical and environmental factors, we suggest that nutrient-rich inputs during high SGD may be a significant driver of algal blooms, but during low SGD periods, multiple drivers are responsible for the occurrence of algal blooms.  相似文献   

Stable isotopic and elemental characteristics of recent tufa from a karstic Krka River (south‐east Slovenia): useful environmental proxies?          下载免费PDF全文

Saša Zavadlav  Boštjan Rožič  Matej Dolenec  Sonja Lojen 《Sedimentology》2017,64(3):808-831

Tufa samples from 16 consecutive barrages along a 13 km section of the groundwater‐fed Krka River (Slovenia) were analysed for their petrographical, mineralogical, elemental and stable carbon (δ¹³C) and oxygen (δ¹⁸O) isotope composition, to establish their relation to current climatic and hydrological conditions. Waters constantly oversaturated with calcite and the steep morphology of the Krka riverbed stimulate rapid CO₂ degassing and subsequent tufa precipitation. The carbon isotope fractionation (Δ¹³C) between dissolved inorganic carbon and tufa in the Krka River evolves towards isotopic equilibrium being controlled by continuous CO₂ degassing and tufa precipitation rate downstream. The Δ¹³C increased from 1·9 to 2·5‰ (VPDB); however, since tufa precipitation rates remain similar downstream, the major controlling factor of carbon isotope exchange is most probably related to the continuous ¹²CO₂ degassing downstream leaving the carbon pool enriched in ¹³C. In the case of oxygen, the isotope fractionation (Δ¹⁸O) was found to be from 1·0 to 2·3‰ (VSMOW) smaller than reported in the literature. The observed discrepancies are due to different precipitation rates of calcite deposits because Krka tufas on cascades grow relatively faster compared to slowly precipitated calcite deposits in cave or stream pools. Due to non‐equilibrium oxygen isotope exchange between Krka tufa and water, the δ¹⁸O proxy showed from 1·2 to 8·2°C higher calculated water temperatures compared to measured water temperatures, demonstrating that δ¹⁸O proxy‐based temperature equations are not reliable for water temperature calculations of fast‐growing tufa on cascades. Because Mg is bound to the terrigenous dolomite fraction in the Krka tufa samples, the Mg/Ca was also found to be an unreliable temperature proxy yielding over up to 20°C higher calculated water temperatures.  相似文献