Systematic change of foraminiferal Mg/Ca ratios across a strong salinity gradient

The Mg/Ca ratio of foraminiferal calcite is an important proxy for estimating past ocean temperatures. Used in conjunction with δ¹⁸O of foraminiferal calcite it allows deconvolution of temperature and ice-volume signals to infer past ocean temperatures and salinities (assuming the relationship between seawater δ¹⁸O and salinity is known). Such work assumes that temperature is the only, or at least the dominant, environmental controller of foraminiferal Mg/Ca. The semi-enclosed Mediterranean Sea, where salinity varies from 36 to 40 psu over a seasonal temperature range of between only 5 °C to 8 °C, provides a relevant setting to test this assumption outside the laboratory. In this study, planktonic foraminifera (O. universa, G. siphonifera, G. bulloides and G. ruber (white) and (pink)) were picked from 11 box core tops spanning the Mediterranean salinity gradient and analysed for their trace-element concentrations. Mg/Ca ratios are higher, for the associated calcification temperatures, than in other regions where calibrations have been conducted and correlate poorly with calcification temperature. Mg/Ca ratios are particularly high for samples from the Eastern Mediterranean where salinity is unusually high. Correlations of Mg/Ca with the calcification salinity are statistically significant with Mg/Ca changing by 15–59% per psu, suggesting that salinity may act as a control on Mg/Ca ratios in addition to the dominant temperature control. We show that contamination by non-carbonate material and diagenetic high-Mg carbonate overgrowths cannot account for the observed trend of increasing Mg/Ca with salinity. A relationship between Mg/Ca and salinity is also suggested by re-analysis of calibrations from open-ocean settings. These new Mediterranean results are from a region with unusually high salinity but suggest that the effects of salinity on the Mg/Ca palaeothermometer should be considered even in open-ocean settings, particularly where large salinity changes occurred in the past.     

Minor element and Ca isotope composition of calcareous dinoflagellate cysts of cultured Thoracosphaera heimii

We investigated the influences of temperature, salinity and pH on the calcium isotope as well as trace and minor element (uranium, strontium, magnesium) to Ca ratios on calcium carbonate cysts of the calcareous dinoflagellate species Thoracosphaera heimii grown in laboratory cultures. The natural habitat of this species is the photic zone (preferentially at the chlorophyll maximum depth) of temperate to tropical oceans, and it is abundant in deep-sea sediments over the entire Cenozoic. In our experiments, temperatures ranged from 12 to 30 °C, salinity from 36.5 to 38.8 and pH from 7.9 to 8.4. The δ^44/40Ca of T. heimii cysts resembles that of other marine calcifiers, including coccolithophores, foraminifers and corals. However, its temperature sensitivity is considerably smaller and statistically insignificant, and T. heimii might serve as a recorder of changes in seawater δ^44/40Ca over geologic time. The Sr/Ca ratios of T. heimii cysts show a pronounced temperature sensitivity (0.016 mmol/mol °C^? 1) and have the potential to serve as a palaeo-sea surface temperature proxy. No clear temperature- and pH-dependences were observed for Mg/Ca. U/Ca seems to be influenced by temperature and pH, but the correlations change sign at 23 °C and pH 8.2, respectively.     

Constraints of authigenic carbonates on trace elements (Sr, Mg) of lacustrine ostracod shells in paleoenvironment reconstruction and its mechanism

Molar ratios of Mg/Ca and Sr/Ca were measured in two species of ostracod shells preserved in the upper core (15-55 m) of the Heqing Basin in Yunnan Province, southwest China. By correlating the molar ratios between Mg/Ca and Sr/Ca and comparing them with Sr concentrations of the sediments, we suggested that: (1) the molar Mg/Ca and Sr/Ca ratio variations in respective ostracod primo re- flected the changes in its ambient water composition and ecology; (2) the molar Sr/Ca ratios responded better to the salinity change linearly than Mg/Ca without aragonite precipitation in the system, and otherwise there was no linear relation between them; and (3) the molar Sr/Ca ratios were mainly con- trolled by salinity and authigenic carbonate precipitation, whereas the molar Mg/Ca ratios were related to both salinity and temperature. In fact, the rate of ostracod growth owing to temperature controls the fluctuation of Mg/Ca in shells. Here, more attentions should be paid to the constraint of authigenic mineral precipitation processes on the trace elements in ostracod shells and to the correlation between these trace elements in biogenic carbonates and compositions of the sediments in systems and in fu- ture in vitro experiments.     

High precision glacial–interglacial benthic foraminiferal Sr/Ca records from the eastern equatorial Atlantic Ocean and Caribbean Sea

Glacial–interglacial variation in the marine Sr/Ca ratio has important implications for coral Sr thermometry [J.W. Beck et al., Science 257 (1992) 644–647]. A possible variation of 1–3% was proposed based on ocean models [H.M. Stoll and D.P. Schrag, Geochim. Cosmochim. Acta 62 (1998) 1107–1118]. Subsequently, studies have used fossil foraminifera to test this prediction [P.A. Martin et al., Geochem. Geophys. Geosyst. 1 (1999); H.M. Stoll et al., Geochim. Cosmochim. Acta 63 (1999) 3535–3547; H. Elderfield et al., Geochem. Geophys. Geosyst. 1 (2000)]. But whether some component of foraminiferal Sr/Ca variation can be uniquely ascribed to seawater Sr variation is still not clear. To address this question, we developed cleaning and analysis techniques and measured Sr/Ca ratios on individual shells of the modern benthic foraminifer Cibicidoides wuellerstorfi. We showed that different size shells have different Sr/Ca ratios; however, samples with shell sizes of 355–500 μm appear to have normally distributed Sr/Ca ratios (1σ=1.8%). For multi-shell measurements (with estimated errors of 0.12–0.39%), the ratio varied by as much as 7.2±0.5% during the last glaciation for two Caribbean records at the same site and by 3.7±0.5% over the past 40,000 yr for one record from the Sierra Leone Rise in the eastern equatorial Atlantic. The two Caribbean records are very similar indicating that the behavior of shell Sr uptake was identical locally and that the shell Sr/Ca ratio faithfully reflects the local environment. The Atlantic record differs from the Caribbean records by as much as several percent. Thus, the foraminiferal Sr/Ca changes cannot be solely due to changes in seawater Sr/Ca unless the glacial deep ocean had spatial variation in Sr/Ca well in excess of the modern ocean. Certain similarities between the three records do exist. Notably, the rate of change of Sr/Ca is similar between 9 and 0 ka (−0.25%/kyr) and between 25 and 16 ka (+0.16%/kyr). This suggests that during these intervals, benthic foraminiferal Sr/Ca was affected by similar large-scale variables. One of these variables may be the average marine Sr/Ca ratio; however, comparison with model predictions [H.M. Stoll and D.P. Schrag, Geochim. Cosmochim. Acta 62 (1998) 1107–1118] suggests other factors must also be considered. The discrepancies between the two sites may be related to the different water mass histories for the Caribbean and eastern Atlantic. Our results suggest that variation of the seawater Sr budget only partially contributed to C. wuellerstorfi Sr/Ca records, while other significant factors still need to be quantified. At present we cannot confidently determine past seawater Sr/Ca variation from our foraminiferal records.     

Strontium stable isotopes fractionate in the soil environments?

This study shows that the stable isotopic composition of strontium (the ⁸⁸Sr/⁸⁶Sr ratio expressed as δ^88/86Sr value relative to the NBS987 standard) varies significantly in sedimentary terrestrial environments. The abundances of ⁸⁶Sr, ⁸⁸Sr isotopes were analyzed by MC-ICP-MS “Nu Plasma”. All studied rocks and waters show δ^88/86Sr values that are distinctly different from the measured NBS987 standard (yielding 0.01 ± 0.05‰, all errors are reported as 2σ). Modern corals from the northern Gulf of Aqaba, Red Sea yielded significantly different value than seawater (δ^88/86Sr = 0.22 ± 0.07‰, compared to 0.35 ± 0.06‰, respectively), in an excellent correlation with the δ^88/86Sr analyses reported by Fietzke and Eisenhauer [Fietzke, J., Eisenhauer, A., 2006. Determination of temperature-dependent stable strontium isotopes (⁸⁸Sr/⁸⁶Sr) fractionation via bracketing standard MC-ICP-MS. Geochm. Geophys. Geosyst. 7 (no. 8)] on other coral samples. All carbonate samples that originated in the marine environment: corals (porites and acropora from the northern Gulf of Aqaba); Cretaceous limestone and runoff from the Judea Mountains as well as lacustrine evaporitic aragonite (Dead Sea); and Red Sea and Atlantic seawater yield an average δ^88/86Sr value of 0.26 ± 0.1‰. On the other hand, secondary materials (products of chemical weathering) from the terrestrial environment of the Judea Mountain such as terra rossa soil and speleothem calcite (that derives its Sr from the above-lying soil) yielded significantly lower δ^88/86Sr value of − 0.17 ± 0.06‰. This indicates that strontium isotopes fractionate in the soil environment calling for a possible development of strontium isotopes as a tracer for processes of chemical weathering and pedogenesis.     

Tracing effects of decalcification on solute sources in a shallow groundwater aquifer, NW Germany

δ⁸⁷Sr values and Ca/Sr ratios were employed to quantify solute inputs from atmospheric and lithogenic sources to a catchment in NW Germany. The aquifer consists primarily of unconsolidated Pleistocene eolian and fluviatile deposits predominated by >90% quartz sand. Accessory minerals include feldspar, glauconite, and mica, as well as disperse calcium carbonate in deeper levels. Decalcification of near-surface sediment induces groundwater pH values up to 4.4 that lead to enhanced silicate weathering. Consequently, low mineralized Ca–Na–Cl- and Ca–Cl-groundwater types are common in shallow depths, while in deeper located calcareous sediment Ca–HCO₃-type groundwater prevails. δ⁸⁷Sr values and Ca/Sr ratios of the dissolved pool range from 7.3 to −2.6 and 88 to 493, respectively. Positive δ⁸⁷Sr values and low Ca/Sr ratios indicate enhanced feldspar dissolution in shallow depths of less than 20 m below soil surface (BSS), while equilibrium with calcite governs negative δ⁸⁷Sr values and elevated Ca/Sr ratios in deep groundwater (>30 m BSS). Both positive and negative δ⁸⁷Sr values are evolved in intermediate depths (20–30 m BSS). For groundwater that is undersaturated with respect to calcite, atmospheric supplies range from 4% to 20%, while feldspar-weathering accounts for 8–26% and calcium carbonate for 62–90% of dissolved Sr²⁺. In contrast, more than 95% of Sr²⁺ is derived by calcium carbonate and less than 5% by feldspar dissolution in Ca–HCO₃-type groundwater. The surprisingly high content of carbonate-derived Sr²⁺ in groundwater of the decalcified portion of the aquifer may account for considerable contributions from Ca-containing fertilizers. Complementary tritium analyses show that equilibrium with calcite is restricted to old groundwater sources.     

青藏高原湖泊Mg~(2+)、Ca~(2+)和Mg/Ca盐度指示意义的初步分析

总结了青藏高原地区400多个湖泊湖水的Mg2+、Ca2+和Mg/Ca等水化指标与湖水盐度的相关关系,以及这种关系随着湖水变化(不同采样时间和采样点以及自然蒸发)而产生的变化规律.结果表明:青藏高原湖泊湖水的Mg2+浓度与盐度具有较为稳定的正相关关系,而Ca2+和Mg/Ca与盐度的相关性较弱.在对于某一特定水化学类型的湖泊,一般碳酸盐型湖泊的Mg2+、Ca2+以及Mg/Ca等指标与盐度均没有明显的相关性;硫酸盐型湖泊中Mg2+浓度和盐度呈现较高的正相关关系,而Ca2+以及Mg/Ca与盐度的相关性仍很弱;而在氯化物型湖泊中,Mg2+浓度与盐度呈更高的正相关性,Ca2+浓度也与盐度呈一定的正相关性,Mg/Ca这一指标与盐度的相关性依然很弱.而对某一特定湖泊,在不同演化阶段或不同的采样地点,Mg2+浓度与盐度仍然保持明显的正相关关系,而Ca2+以及Mg/Ca与盐度的相关性仍然不稳定或很弱.在青藏高原作古环境重建应用的时候,湖水Mg2+浓度是古盐度一个较好的转换指标,而Ca2+以及Mg/Ca的古盐度指示意义相对较弱.     

Vent fluid chemistry in Bahía Concepción coastal submarine hydrothermal system, Baja California Sur, Mexico

Shallow submarine hydrothermal activity has been observed in the Bahía Concepción bay, located at the Gulf coast of the Baja California Peninsula, along faults probably related to the extensional tectonics of the Gulf of California region. Diffuse and focused venting of hydrothermal water and gas occurs in the intertidal and shallow subtidal areas down to 15 m along a NW–SE-trending onshore–offshore fault. Temperatures in the fluid discharge area vary from 50 °C at the sea bottom up to 87 °C at a depth of 10 cm in the sediments.Chemical analyses revealed that thermal water is enriched in Ca, As, Hg, Mn, Ba, HCO₃, Li, Sr, B, I, Cs, Fe and Si, and it has lower concentrations of Cl, Na, SO₄ and Br than seawater. The chemical characteristics of the water samples indicate the occurrence of mixing between seawater and a thermal end-member. Stable isotopic oxygen and hydrogen composition of thermal samples plot close to the Local Meteoric Water Line on a mixing trend between a thermal end-member and seawater. The composition of the thermal end-member was calculated from the chemistry of the submarine samples data by assuming a negligible amount of Mg for the thermal end-member. The results of the mixing model based on the chemical and isotopic composition indicate a maximum of 40% of the thermal end-member in the submarine vent fluid.Chemical geothermometers (Na/Li, Na–K–Ca and Si) were applied to the thermal end-member concentration and indicate a reservoir temperature of approximately 200 °C. The application of K–Mg and Na/Li geothermometers for vent fluids points to a shallow equilibrium temperature of about 120 °C.Results were integrated in a hydrogeological conceptual model that describes formation of thermal fluids by infiltration and subsequent heating of meteoric water. Vent fluid is generated by further mixing with seawater.     

Modern and Pleistocene boron isotope composition of the benthic foraminifer Cibicidoides wuellerstorfi

Here we present the first species-specific study of boron isotopes in the epibenthic foraminifer species Cibicidoides wuellerstorfi. Coretop samples from a water depth profile from 1000 to 4500 m on the northern flank of the Walvis Ridge are 4.4‰ lower than the values expected, based on calculations of the δ¹¹B_borate of ambient seawater. Similar values for this foraminifer species are presented from ODP site 668B at the Sierra Leone Rise, in the equatorial Atlantic. The consistency between data of the same species suggests the offsets are primary, rather than diagenetic. Glacial C. wuellerstorfi from ODP 668B and Walvis Ridge have boron isotope compositions only slightly different to interglacial samples, that is no larger than + 0.10 pH units, or + 23 µmol kg^− 1 in [CO₃²⁻] above the reconstructed glacial lysocline, and − 0.07 pH units, or − 14 µmol kg^− 1 in [CO₃²⁻] below. We use these results to suggest that glacial deep water pH in the Atlantic was similar to interglacial pH. The new data resolve the inconsistency between the previously reported high bottom water pH and the lack of significant carbonate preservation of the glacial deep ocean.     

Seasonal variations in pCO2 and its controlling factors in surface seawater of the northern East China Sea

Surface partial pressure of CO₂ (pCO₂), temperature, salinity, nutrients, and chlorophyll a were measured in the East China Sea (ECS; 31°30′–34°00′N to 124°00′–127°30′E) in August 2003 (summer), May 2004 (spring), October 2004 (early fall), and November 2005 (fall). The warm and saline Tsushima Warm Current was observed in the eastern part of the survey area during four cruises, and relatively low salinity waters due to outflow from the Changjiang (Yangtze River) were observed over the western part of the survey area. Surface pCO₂ ranged from 236 to 445 μatm in spring and summer, and from 326 to 517 μatm in fall. Large pCO₂ (values >400 μatm) occurred in the western part of the study area in spring and fall, and in the eastern part in summer. A positive linear correlation existed between surface pCO₂ and temperature in the eastern part of the study area, where the Tsushima Warm Current dominates; this correlation suggests that temperature is the major factor controlling surface pCO₂ distribution in that area. In the western part of the study area, however, the main controlling factor is different and seasonally complex. There is large transport in this region of Changjiang Diluted Water in summer, causing low salinity and low pCO₂ values. The relationship between surface pCO₂ and water stability suggests that the amount of mixing and/or upwelling of CO₂-rich water might be the important process controlling surface pCO₂ levels during spring and fall in this shallow region. Sea–air CO₂ flux, based on the application of a Wanninkhof [1992. Relationship between wind speed and gas exchange over the ocean. Journal of Geophysical Research 97, 7373–7382] formula for gas transfer velocity and a set of monthly averaged satellite wind data, were −5.04±1.59, −2.52±1.81, 1.71±2.87, and 0.39±0.18 mmol m⁻² d⁻¹ in spring, summer, early fall, and fall, respectively, in the northern ECS. The ocean in this study area is therefore a carbon sink in spring and summer, but a weak source or in equilibrium with the atmosphere in fall. If the winter flux value is assumed to have been the mean of autumnal and vernal values, then the northern ECS absorbs about 0.013 Pg C annually. That result suggests that the northern ECS is a net sink for atmospheric CO₂, a result consistent with previous studies.     

Geochemistry of coral from Papua New Guinea as a proxy for ENSO ocean–atmosphere interactions in the Pacific Warm Pool

A Porites sp. coral growing offshore from the Sepik and Ramu Rivers in equatorial northern Papua New Guinea has yielded an accurate 20-year history (1977–1996) of sea surface temperature (SST), river discharge, and wind-induced mixing of the upper water column. Depressions in average SSTs of about 0.5–1.0 °C (indicated by coral Sr/Ca) and markedly diminished freshwater runoff to the coastal ocean (indicated by coral δ¹⁸O, δ¹³C and UV fluorescence) are evident during the El Niño – Southern Oscillation (ENSO) events of 1982–1983, 1987 and 1991-1993. The perturbations recorded by the coral are in good agreement with changes in instrumental SST and river discharge/precipitation records, which are known to be diagnostic of the response of the Pacific Warm Pool ocean–atmosphere system to El Niño. Consideration of coastal ocean dynamics indicates that the establishment of northwest monsoon winds promotes mixing of near-surface waters to greater depths in the first quarter of most years, making the coral record sensitive to changes in the Asian–Australian monsoon cycle. Sudden cooling of SSTs by 1°C following westerly wind episodes, as indicated by the coral Sr/Ca, is consistent with greater mixing in the upper water column at these times. Furthermore, the coral UV fluorescence and oxygen isotope data indicate minimal contribution of river runoff to surface ocean waters at the beginning of most years, during the time of maximum discharge. This abrupt shift in flood-plume behaviour appears to reflect the duration and magnitude of northwest monsoon winds, which tend to disperse flood plume waters to a greater extent in the water column when wind-mixing is enhanced. Our results suggest that a multi-proxy geochemical approach to the production of long coral records should provide comprehensive reconstructions of tropical paleoclimate processes operating on interannual timescales.     

Correlation between δ~(18)O,Sr/Ca and Mg/Ca of coral Acropora and seawater temperature from coral culture experiments

To be used as proxies of seawater surface temperature(SST), the δ 18Oc values and Sr/Ca and Mg/Ca ratios of scleractinian coral skeletons must be verified by coral culture experiments in the laboratory. This paper describes a coral culture experiment that was conducted at several seawater temperatures T(21–28°C) using a tandem aquarium system and the new method for depositing coral skeletons grown under controlled conditions. The δ 18Oc values and the Sr/Ca and Mg/Ca ratios of the cultured coral were measured. We concluded that the δ 18Oc values and Sr/Ca and Mg/Ca ratios of the cultured coral are clearly correlated with T. The linear regression curve is δ18Oc(‰)=δ0.1427δT(°C)δ0.1495(n=18, r=0.955, p0.0001), and the slope of δ0.1427‰/°C is at the low end of the range of published values(δ0.13–δ0.29‰/°C). The Sr/Ca ratio decreases with increasing T, whereas the Mg/Ca ratio increases with increasing T, indicating a negative correlation between Sr/Ca and Mg/Ca. Their linear regression curves are Sr/Ca(mmol/mol)=δ0.04156δT+10.59(n=15, r=0.789, p0.005) and Mg/Ca(mmol/mol)= 0.04974δT+2.339(n=17, r=0.457, p0.05), respectively, which demonstrate that when Mg/Ca and Sr/Ca are increased by one unit, T increases by 5.19°C and decreases by 15.62°C, respectively. These variations are significantly lower than published values.     

Al–Mg and Pb–Pb systematics of Allende CAIs: Canonical solar initial Al/Al ratio reinstated

The precise knowledge of the initial ²⁶Al/²⁷Al ratio [(²⁶Al/²⁷Al)₀] is crucial if we are to use the very first solid objects formed in our Solar System, calcium–aluminum-rich inclusions (CAIs) as the “time zero” age-anchor and guide future work with other short-lived radio-chronometers in the early Solar System, as well as determining the inventory of heat budgets from radioactivities for early planetary differentiation. New high-precision multi-collector inductively-coupled plasma mass spectrometry (MC-ICP-MS) measurements of ²⁷Al/²⁴Mg ratios and Mg-isotopic compositions of nine whole-rock CAIs (six mineralogically characterized fragments and three micro-drilled inclusions) from the CV carbonaceous chondrite, Allende yield a well-defined ²⁶Al–²⁶Mg fossil isochron with an (²⁶Al/²⁷Al)₀ of (5.23 ± 0.13) × 10^− 5. Internal mineral isochrons obtained for three of these CAIs (A44A, AJEF, and A43) are consistent with the whole-rock CAI isochron. The mineral isochron of AJEF with (²⁶Al/²⁷Al)₀ = (4.96 ± 0.25) × 10^− 5, anchored to our precisely determined absolute ²⁰⁷Pb–²⁰⁶Pb age of 4567.60 ± 0.36 Ma for the same mineral separates, reinstate the “canonical” (²⁶Al/²⁷Al)₀ of 5 × 10^− 5 for the early Solar System. The uncertainty in (²⁶Al/²⁷Al)₀ corresponds to a maximum time span of ± 20 Ka (thousand years), suggesting that the Allende CAI formation events were culminated within this time span. Although all Allende CAIs studied experienced multistage formation history, including melting and evaporation in the solar nebula and post-crystallization alteration likely on the asteroidal parent body, the ²⁶Al–²⁶Mg and U–Pb-isotopic systematics of the mineral separates and bulk CAIs behaved largely as closed-system since their formation. Our data do not support the “supra-canonical” ²⁶Al/²⁷Al ratio of individual minerals or their mixtures in CV CAIs, suggesting that the supra-canonical ²⁶Al/²⁷Al ratio in the CV CAIs may have resulted from post-crystallization inter-mineral redistribution of Mg isotopes within an individual inclusion. This redistribution must be volumetrically minor in order to satisfy the mass balance of the precisely defined bulk CAI and bulk mineral data obtained by MC-ICP-MS.The radiogenic ²⁰⁸Pb/²⁰⁶Pb ratio obtained as a by-product from the Pb–Pb age dating is used to estimate time-integrated ²³²Th/²³⁸U ratio (κ value) of CAIs. Limited κ variations among the minerals within a single CAI, contrasted by much larger variations among the bulk CAIs, suggest Th/U fractionation occurred prior to crystallization of igneous CAIs. If interpreted as primordial heterogeneity, the κ value can be used to calculate the mean age of the interstellar dust from which the CAIs condensed.     

Correlations between microbial indicators, pathogens, and environmental factors in a subtropical Estuary

The objective of this study was to evaluate whether indicator microbes and physical–chemical parameters were correlated with pathogens within a tidally influenced Estuary. Measurements included the analysis of physical–chemical parameters (pH, salinity, temperature, and turbidity), measurements of bacterial indicators (enterococci, fecal coliform, Escherichia coli, and total coliform), viral indicators (somatic and MS2 coliphage), viral pathogens (enterovirus by culture), and protozoan pathogens (Cryptosporidium and Giardia). All pathogen results were negative with the exception of one sample which tested positive for culturable reovirus (8.5 MPN/100 L). Notable physical–chemical parameters for this sample included low salinity (<1 ppt) and high water temperature (31 °C). Indicator bacteria and indicator virus levels for this sample were within average values typically measured within the study site and were low in comparison with levels observed in other freshwater environments. Overall results suggest that high levels of bacterial and viral indicators were associated with low salinity sites.     

Anomalous drip in the Punkva caves (Moravian Karst): relevant implications for paleoclimatic proxies

The anomalous drip in the Punkva caves (Moravian Karst) shows specific hydrogeochemical properties such as low SI_calcite ~ 0.14 ± 0.11 (standard deviation), low mineralization (4.53 ± 0.42) × 10^?3 mol l^?1, and enhanced values of δ¹³C (?7.85 to ?8.35‰ VPDB), Mg/Ca × 1000 ratio (45.7 ± 3.3), and Sr/Ca × 1000 ratio (0.65 ± 0.06). By these properties, the anomalous drip significantly differs from other regular drips in the same cave and other caves in the region. The study suggests that the anomalous drip properties are a consequence of prior calcite precipitation or/and water mixing along the water flow path. As the former processes are spatially controlled, the knowledge of dripwater flow path seems to be necessary for correct paleoclimatic/paleoenvironmental reconstructions. Copyright © 2015 John Wiley & Sons, Ltd.     

Oceanography of coastal and riverine waters around Timika, West Central Irian Jaya, Arafura Sea

Oceanographic studies have been carried out in coastal and riverine waters of the area around Timika, West Papua in November 1999, March–April, July and November 2000. The temperature of the seawater along the coast is around 28 °C in winter (November 99), rising to 30.0 °C (November 00). In the open sea, 30 miles off the coast at 40 m water depth, the temperature is >30 °C with no stratification. Water temperature near the coast is consistently lower than in the open sea. This is thought to be due the cooling effect of the land, being densely covered by mangrove forest. In the upper parts of the Kamora, West Tipuka, East Tipuka, Ajkwa, Minajerwi, Mawati and Otakwa Rivers, at salinity zero psu, water temperature varies between 24.6 and 26.2 °C, which is as cold as the temperature in the upwelling Banda Sea to the NW. Some of these rivers are fed by glacial melt water from the high mountains to the east. At mid estuary, warm seawater is found under the cooler river water.Salinity near this coast varied between 24 and 30, and offshore salinity was 31–33 with no stratification. Inshore surface waters were turbid (11–14 ntu), and near bottom waters were generally much more turbid from river sediment supply and tidal resuspension. The Ajkwa River estuary has the highest turbidity (750 ntu) at zero salinity. Offshore waters were very clear (5.0–6.0 ntu), and there was no increase in turbidity near the bottom.     

Glacial–interglacial changes in Subantarctic sea surface temperature and δO-water using foraminiferal Mg

Laboratory culturing experiments with living Globigerina bulloides indicate that Mg/Ca is primarily a function of seawater temperature and suggest that Mg/Ca of fossil specimens is an effective paleotemperature proxy. Using culturing results and a core-top Neogloboquadrina pachyderma calibration, we have estimated glacial–interglacial changes in sea surface temperature (SST) using planktonic Mg/Ca records from core RC11-120 in the Subantarctic Indian Ocean (43°S, 80°E) and core E11-2 in the Subantarctic Pacific Ocean (56°S, 115°W). Our results suggest that glacial SST was about 4°C cooler in the Subantarctic Indian Ocean and 2.5°C cooler in the Subantarctic Pacific. Comparison of SST and planktonic δ¹⁸O records indicates that changes in SST lead changes in δ¹⁸O by on average 1–3 kyr. The glacial–interglacial temperature change indicated by the Subantarctic Mg/Ca records suggests that temperature accounts for 40–60% of the foraminiferal δ¹⁸O change. We have used the Mg/Ca-based SST estimates and δ¹⁸O determinations to generate site-specific seawater δ¹⁸O records, which suggest that seawater δ¹⁸O was on average 1‰ more positive during glacial episodes compared with interglacial episodes.     

The partitioning of Triclosan between aqueous and particulate bound phases in the Hudson River Estuary

The distribution of Triclosan within the Hudson River Estuary can be explained by a balance among the overall effluent inputs from municipal sewage treatment facilities, dilution of Triclosan concentrations in the water column with freshwater and seawater inputs, removal of Triclosan from the water column by adsorption to particles, and loss to photodegradation. This study shows that an average water column concentration of 3 ± 2 ng/l (in the lower Hudson River Estuary) is consistent with an estimate for dilution of average wastewater concentrations with seawater and calculated rates of adsorption of Triclosan to particles. An average Triclosan sediment concentration of 26 ± 11 ng/g would be in equilibrium with the overlying water column if Triclosan has a particle-to-water partitioning coefficient of k_d  10⁴, consistent with laboratory estimates.     

中国东部若干封闭含油气盆地泥质岩地球化学的研究

中国东部沿北东、北北东向断裂发育了一系列早第三纪含油气断陷盆地。受干旱气候的影响,这些盆地常为封闭或半封闭的咸水湖泊环境。本文通过对其中若干盆地泥质岩的化学分析,确认泥质岩主要由粘土矿物组成,并含少量碳酸盐。将盆地的沉积环境,尤其是盐度与一些地球化学参数关系作了探讨后认为,低盐度时 Sr/Ba、Ca、Mg 总量、Ca/Mg、V/Ni 和 Mn/Fe 能反映湖泊在时空上的盐度变化。高盐度时,Sr/Ba、CaCO_3、B 与盐度正相关已不复成立,并对其原因作了讨论。     

Multi-factors on biodegradation kinetics of polycyclic aromatic hydrocarbons (PAHs) by Sphingomonas sp. a bacterial strain isolated from mangrove sediment

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated sediment is an attractive remediation technique and its success depends on biodegradation kinetics, and the optimal condition for the PAH-degrading isolates; however, information on this aspect is still scarce. The effects of multi-factors on biodegradation of phenanthrene, a 3-ring model PAH, in contaminated sediment slurry by Sphingomonas sp. a bacterial strain isolated from surface mangrove sediment, were investigated using the orthogonal experimental design (form L₁₆(4⁵)). The most significant factors were salinity and inoculum size, while the effects of phenanthrene concentrations, nutrient addition and temperatures were insignificant. The optimal biodegradation condition in contaminated mangrove sediment slurry was 30 °C, 15 ppt salinity, a carbon/nitrogen ratio of 100:1 (the background ratio in sediment) and an inoculum size of 10⁶ most probable number g⁻¹ sediment. The phenanthrene biodegradation could be best described by the first order rate model, C = C₀e^−kt, where k (the rate constant) is equaled to 0.1185, under the optimal condition. The kinetic model was verified and its validity in predicting biodegradation by Sphingomonas sp. at various phenanthrene concentrations was proved by experimental data.