Seawater Source Research Articles

Regional patterns in the geochemistry of oil-field water, southern San Joaquin Valley, California, USA

Chemical and isotopic data for water co-extracted with hydrocarbons in oil and gas fields are commonly used to examine the source of the formation water and possible impacts on groundwater in areas of oil and gas development. Understanding the geochemical variability of oil-field water could help to evaluate its origin and delineate possible contamination of shallow aquifers in cases where oil-field water is released to the environment. Here we report geochemical and multiple isotope (H, C, O, Sr, Ra) data from 22 oil wells, three sources of produced water that are disposed of in injection wells, and two surface disposal ponds in four oil fields in the southern San Joaquin Valley, California (Fruitvale, Lost Hills, North and South Belridge). Correlations between Cl and δ18O, as well as other ions, and gradual increases in salinity with depth, indicate dilution of one or more saline end-members by meteoric water. The saline end-members, represented by deep samples (610 m–2621 m) in three oil-bearing zones, are characterized by NaCl composition, near-seawater Cl concentrations (median 20,000 mg/L), enriched δ18OH2O (median 3.4‰), high ammonium (up to 460 mg-N/L), and relatively high radium activity (226Ra+228Ra = 12.3 Bq/L). The deepest sample has low Na/Cl (0.74), high Ca/Mg (5.0), and low 87Sr/86Sr (0.7063), whereas the shallower samples have higher Na/Cl (0.86–1.2), Ca/Mg near 1, and higher 87Sr/86Sr (∼0.7083). The data are consistent with an original seawater source being modified by various depth and lithology dependent diagenetic processes. Dilution by meteoric water occurs naturally on the east side of the valley, and in association with water-injection activities on the west side. Meteoric-water flushing, particularly on the east side, results in lower solute concentrations (minimum total dissolved solids 2730 mg/L) and total radium (minimum 0.27 Bq/L) in oil-field water, and promotes biodegradation of dissolved organic carbon and hydrocarbon gases like propane. Acetate concentrations and δ13C of dissolved inorganic carbon indicate biogenic methane production occurs in some shallow oil zones. Natural and human processes produce substantial variability in the geochemistry of oil-field water that should be considered when evaluating mixing between oil-field waters and groundwater. The variability could result in uncertainty as to detecting the potential source and impact of oil-field water on groundwater.

Biodegradation of dispersed oil in natural seawaters from Western Greenland and a Norwegian fjord

With increasing oil exploration, production and transportation in the Arctic, predictions of the fate of spilled oil become important, including oil compound biodegradation. The use of chemical dispersants may result in increased biodegradation due to the generation of dispersions consisting of small oil droplets, but only few studies have focused on biodegradation of chemically dispersed oil in Arctic seawater. In this study we compared oil biotransformation in Arctic and temperate seawaters collected from Western Greenland (Disko Bay, surface and from 80 m depth) and a Norwegian fjord (Trondheimsfjord, surface). A naphthenic oil, premixed with a dispersant, was dispersed in the seawaters from the different sources, and the dispersions incubated in low concentrations in a carousel system at 4–5 °C for up to 64 days. Targeted oil compounds (n-alkanes, BTEX, naphthalenes and PAHs) were biotransformed in both Arctic and temperate seawaters, although the degradation was faster in the temperate seawater. In the Arctic seawater, transformation was faster in the surface than in the subsurface seawater. Calculations of biotransformation rates and half-lives of oil compound groups representing 70–80% of fresh oils also showed significantly faster depletion in the temperate than the Arctic seawater. Microbial analyses revealed differences between the bacterial communities in the seawater sources during oil biodegradation. The results emphasized, that oil compounds are biodegraded in Arctic seawater, but degradation potential and rates may vary between seawaters from different sources.

Nitrogen uptake and assimilation preferences of the main green tide alga Ulva prolifera in the Yellow Sea, China

The successive outbreak of large-scale Ulva prolifera green tides in the Yellow Sea, China, from 2007 to 2017, is a serious regional environmental issue that attracts worldwide attention. The competitive advantage in nitrogen uptake and utilization is an important factor, making U. prolifera the dominant green-tide-forming seaweed. However, the detailed preference characteristics of U. prolifera for nitrogen uptake and assimilation in common inorganic and organic nitrogen sources is poorly understood and is studied using stable nitrogen isotope (15N) analysis. Our results reveal that various nitrogen sources can be simultaneously and directly taken up by U. prolifera. The uptake rates are in the sequence of NO3− (nitrate) > NH4+ (ammonium) > CO(NH2)2 (urea) > C2H5NO2 (glycine) and C3H7NO2 (alanine). In other words, U. prolifera mostly prefers inorganic nitrogen, such as nitrate and ammonium, although it can also utilize different organic nitrogen sources simultaneously. Moreover, the assimilation of NH4+ is inhibited and its uptake cannot be fitted by the Michaelis–Menten equation when the alga is exposed to multiple nitrogen sources. We propose that at the early and middle stages of green tides the rich inorganic nitrogen sources (especially NO3−) in seawater are very important to support the fast growth of U. prolifera, while at the later stage of green tides, when inorganic nitrogen sources have been exhausted, organic nitrogen sources may contribute importantly to maintaining the growth of U. prolifera, thus lengthening the duration of green tides.

The Design and Optimization of the Heat Exchanger of the Sea Water Source Heat Pump Air Conditioning System Based on the Baffle Spacing

In this paper, we proposed the spacing of the single-bow baffle plate to adapt to the current sea water source heat pump air conditioning system. The paper used AutoCAD platform to create a geometric model of a single bow baffle tube heat exchanger, and used the fluid analysis software Fluent to solve the heat exchanger model. The different baffle layouts were compared in the whole sea water source heat pump air conditioning system. Through the distribution of the pressure, velocity and temperature of the shell side, the optimal heat exchanger of baffle plate heat exchanger was obtained. The results show that the spacing of the baffle plate has the optimal value, and when the distance outside the baffle is equal to or slightly larger than the distance within the baffle, the comprehensive performance of the heat exchanger is better.

Microbial communities in seawater from an Arctic and a temperate Norwegian fjord and their potentials for biodegradation of chemically dispersed oil at low seawater temperatures

Biodegradation of chemically dispersed oil at low temperature (0–2 °C) was compared in natural seawater from Arctic (Svalbard) and a temperate (Norway) fjords. The oil was premixed with a dispersant (Corexit 9500) and small-droplet oil dispersions prepared. Faster biotransformation of n-alkanes in the Arctic than in the temperate seawater were associated with the initially higher abundance of the alkane-degrading genus Oleispira in the Arctic than the temperate seawater. Comparable transformation of aromatic hydrocarbons was further associated with the late emergences Cycloclasticus in both seawater sources. The results showed that chemically dispersed oil may be rapidly biodegraded by microbial communities in Arctic seawater. Compared to oil biodegradation studies at higher seawater temperatures, longer lag-periods were experienced here, and may be attributed to both microbial and oil properties at these low seawater temperatures.

Assessment of polycyclic aromatic hydrocarbons of organic richness in seawater from some coastal area around Alexandria city, Egypt

ABSTRACTThe compositions of polycyclic aromatic hydrocarbons used as chemical markers for the identifying of different sources in the surface seawater of Alexandria coastal area. The quantitative analysis of polycyclic aromatic hydrocarbons (PAHs) showed a concentration ranged from 8970.939-1254756.00 ng/L, which exceed the maximum admissible concentrations of PAHs (200 ng/L) for the water standard of European Union. The calculated diagnostic ratios suggested that the sources of PAHs at the majority of the studied area are derived primarily from pyrogenic sources from incomplete fuel combustion of the boats and vehicle engines with lesser amounts of PAHs contributed from petrogenic sources. Some stations displayed mixed sources in comparison to many other studied marine systems, the PAHs concentrations detected at Alexandria area were considered be higher to pose health risks to aquatic bodies.

Geochemistry of fluids from Earth’s deepest ridge-crest hot-springs: Piccard hydrothermal field, Mid-Cayman Rise

Hosted in basaltic substrate on the ultra-slow spreading Mid-Cayman Rise, the Piccard hydrothermal field is the deepest currently known seafloor hot-spring (4957–4987 m). Due to its great depth, the Piccard site is an excellent natural system for investigating the influence of extreme pressure on the formation of submarine vent fluids. To investigate the role of rock composition and deep circulation conditions on fluid chemistry, the abundance and isotopic composition of organic, inorganic, and dissolved volatile species in high temperature vent fluids at Piccard were examined in samples collected in 2012 and 2013.Fluids from the Beebe Vents and Beebe Woods black smokers vent at a maximum temperature of 398 °C at the seafloor, however several lines of evidence derived from inorganic chemistry (Cl, SiO2, Ca, Br, Fe, Cu, Mn) support fluid formation at much higher temperatures in the subsurface. These high temperatures, potentially in excess of 500 °C, are attainable due to the great depth of the system. Our data indicate that a single deep-rooted source fluid feeds high temperature vents across the entire Piccard field. High temperature Piccard fluid H2 abundances (19.9 mM) are even higher than those observed in many ultramafic-influenced systems, such as the Rainbow (16 mM) and the Von Damm hydrothermal fields (18.2 mM). In the case of Piccard, however, these extremely high H2 abundances can be generated from fluid-basalt reaction occurring at very high temperatures.Magmatic and thermogenic sources of carbon in the high temperature black smoker vents are described. Dissolved ΣCO2 is likely of magmatic origin, CH4 may originate from a combination of thermogenic sources and leaching of abiotic CH4 from mineral-hosted fluid inclusions, and CO abundances are at equilibrium with the water–gas shift reaction. Longer-chained n-alkanes (C2H6, C3H8, n-C4H10, i-C4H10) may derive from thermal alteration of dissolved and particulate organic carbon sourced from the original seawater source, entrainment of microbial ecosystems peripheral to high temperature venting, and/or abiotic mantle sources. Dissolved ΣHCOOH in the Beebe Woods fluid is consistent with thermodynamic equilibrium for abiotic production via ΣCO2 reduction with H2 at 354 °C measured temperature. A lack of ΣHCOOH in the relatively higher temperature 398 °C Beebe Vent fluids demonstrates the temperature sensitivity of this equilibrium.Abundant basaltic seafloor outcrops and the axial location of the vent field, along with multiple lines of geochemical evidence, support extremely high temperature fluid-rock reaction with mafic substrate as the dominant control on Piccard fluid chemistry. These results expand the known diversity of vent fluid composition, with implications for supporting microbiological life in both the modern and ancient ocean.

Assessing the distribution, origins, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in the habitat of Medaka fish at Keramat Kebo River and Estuary, Tangerang, Banten

Indonesia has a variety of coastal systems such as coral reef, mangrove, seagrass, mudflat, and dune, each of which has high biodiversity of species. The primary concern in Indonesia is that rapid economic growth would endanger some essential natural ecosystems and resources, and cause deterioration of environmental condition. As a part of bioindicator development to recognize pollutants with small fish of the genus Oryzias, this study was conducted to assess baseline status of PAHs distribution and sources in seawater, sediments and Oryzias fish. The ecological risk of PAHs in sediments was also evaluated. Concentrations of fifteen USEPA PAH based on GCMS analysis in seawater, sediments, and Oryzias fish vary from 0.00 to 30,600 ng/l, 6.7 to 138.6 ng/g dry weight (dw) and 25.2 to 30.5 ng/g dw, respectively. Based on the diagnostic ratio of PAH compounds, the potential sources of PAHs originated mainly from pyrogenic sources. The status of sediment from this Oryzias fish habitat was considered to be low polluted with PAHs.

Large-area seepage and heat transfer model of beach well infiltration intake system for seawater source heat pump

The seawater source heat pump (SWHP) has attracted significant attention as a renewable energy utilization system. The beach well infiltration intake system (BWIS) effectively improves the stability, reliability, and energy-efficiency of SWHP systems in cold climate areas. A seepage and heat transfer model is established for scientific BWIS applications. MATLAB is used to analyze solutions for the seepage model, as well as to obtain a numerical solution for the heat transfer model. The analytical solution for the seepage model is a fast-solving method compared with the numerical solution. The method explicitly analyzes the qualitative and quantitative relationships among influencing factors of the system. In the heat transfer model, the advection term dominates the heat transfer, while the conduction term can be ignored. A BWIS for SWHP systems is tested and the simulation results agree with the measured data. The simulation model is used to analyze BWIS performance. All system influencing factors are identified and classed according the model. The results demonstrate the usefulness of the simulation model, thereby validating the method as a potential engineering tool for BWIS design.

Can a hybrid RO-Freeze process lead to sustainable water supplies?

In this paper we investigate the potential for using suspension crystallisation for the production of clean drinking water from a seawater source. The experimental results show that the produced water from the suspension crystallisation plant not only meets water quality standards but is comparable in ionic composition to premier bottled water from around the globe. The experimental results obtained from a pilot scale suspension crystallisation unit showed that the achievable water recovery was around 41% and the salt rejection ratio reached over 99%, which is comparable with most desalination technologies. Moreover, a hybrid RO-Freeze plant has been proposed that is capable of significantly increasing the potable product water that could be achieved by RO alone (~400% increase), while simultaneously concentrating the RO brine (used as feed water) producing a super brine of ~13wt%. While there is a cost to this additional process in terms of capital and energy that must be quantified, the obvious increase in water harvest and reduction in residual brine quantity lead to a very attractive desalination process. If the energy demands are acceptable, then this technology could lead to a more sustainable water future.

Heat pump technology: An Alaska case study

Heat pumps are a proven technology around the world and are being increasingly used in Alaska. Technological advances have improved their performance at low temperatures, making them more suitable for arctic environments. This analysis identified data related to 17 heat pumps installed in Alaska, which included air source, ground source, and sea water source systems. The data show that the average installed cost/kW of the heat pumps studied was $5,579. The minimum cost was just over $700/kW for a small air source minisplit system and over $12 000 for a complex vertical loop ground source heat pump. Air source heat pumps in Alaska have operated successfully down to −15 °C. Technological advances are ongoing that should enable further heat pump operation in colder climates.

Pengaruh Komposisi Air Laut dan Pasir Laut Sebagai Sumber Energi Listrik

Electrical energy is energy derived from electric charge that causes static electric field or the movement of electrons in a conductor (conductor of electricity) or ions (positive or negative) in a liquid or gas. The electrical energy needed by society to lighting, heating, cooling, or to move back in mechanical equipment to produce other forms of energy. Utilization of a mixture of sand and sea water is one of the methods of renewable energy. In other hand, utilization of sea water is known that it can generate electricity. This study is a preliminary study to combine sea water and sea sand as raw materials. The purpose of this study was to analyze the optimal composition of sea water and sea sand in generating electrical energy. Source of sea water and sea sand comes from Kenjeran Beach Surabaya Indonesia. Research methods such as mixing sea water and sea sand with a weight percent ratio sea sand in the mixture of 0%, 25%, 50%, 75%, and 100%. The electrical energy generated is determined by observing the current flow and power are seen on the multi meter. Based on the results of current and voltage measurements obtained respectively 2,4 V; 2,3 V; 2,3 V; 1,8 V; and 0,9 V. So the results of the analysis of the composition of sea water and sea sand can potentially be used as a source of electrical energy, although sea sand as agent of resistant.

Experimental study of seawater seepage and heat transfer in a laboratory vertical beach well

Vertical beach well intake (VBWI) is considered as an ideal approach to provide seawater for seawater source heat pump (SWHP) in coastal areas due to its attractive advantages of seawater with high quality, lower temperature in summer and higher temperature in winter compared to raw surface seawater. A laboratory VBWI system was built and experimental strategy was proposed in this paper. First, pumping tests were conducted to obtain hydraulic parameters of the aquifer and estimate the state of water flow within aquifer region. As results of these tests, permeability coefficient of the aquifer was calculated to be 0.0209 m/s, and the water seepage in aquifer could be recognized as laminar flow. Then the influence of water-level variations on temperature in VBWI system was explored. Results showed that water temperature variation of the pumping well influenced by wave-induced water level fluctuations can be negligible in this laboratory VBWI. These testing results were adopted to provide information of hydraulic parameter and simplify the governing equation of seepage and heat transfer of VBWI model. And then numerical models describing seepage and heat transfer process of VBWI system for a SWHP were established. Finally, verification tests for the validity of the numerical model were conducted. Compared experimental results with numerical simulation of pumping temperature under cooling and heating mode respectively, simulation results showed great agreement with experimental data. The results revealed the numerical model can be well validated by laboratory experiments on VBWI system.

Multifactor analysis on beach well infiltration intake system for seawater source heat pump

The seawater source heat pump (SWHP) is a renewable energy utilization system. The beach well infiltration intake system (BWIS) effectively improves the stability, reliability, and energy efficiency of SWHP systems in cold climate areas. BWIS research requires a multidisciplinary approach that involves both hydrogeology and heat transfer theory. There are many factors influencing the energy consumption and life-cycle costs of the systems, with each factor having many possible values. This paper aims to determine the degree of influence of ten representative factors of BWIS: specific heat capacity of rock-soil, rock-soil density, thermal conductivity of rock-soil, void fraction of rock-soil, rock-soil permeability, beach well radius, site length, site width, row number of beach wells, and column number of beach wells. In this paper, a BWIS seepage and heat transfer model is established. Based on the model, an orthogonal design optimization method is presented and analyses are conducted for heat pump unit energy consumption, seawater pump energy consumption, and economic cost for various conditions using MATLAB code. The results indicate that a greater number of beach wells is not always better and the number and placement of beach wells should be scientifically and objectively optimized by the orthogonal design method. The optimization method can scientifically guide engineering design for BWIS and offset the design deficiency that results from the current practice of only using a hydrogeological report of randomly selected test wells.

Effect of seawater intake methods on the performance of seawater source heat pump systems in cold climate areas

The Seawater Source Heat Pump (SWHP) system is an energy-saving and environmentally-friendly technology for the cooling and heating of buildings. The SWHP system is based on obtaining “free” heat from the sea by using heat pumps. In this study, field test and analysis were conducted to compare the performances of beach well infiltration intake system and direct intake system for SWHP systems at the Liaodong Peninsula, China. The average unit COP was 2.99 for the direct intake system and 4.66 for the beach well infiltration intake system, with the average seawater temperature being 5.83°C and 12.85°C, respectively. The test results indicate that the beach well infiltration intake method effectively improves the stability, reliability and energy efficiency of the SWHP systems in cold climate areas, and the intake seawater temperature is a critical factor influencing the performance of SWHP system. A simulation study was conducted for further illustration that how the intake seawater temperature of the beach well infiltration intake system was increased. The simulation result shows that the intake seawater temperature of beach well infiltration intake system is higher than the direct intake system, and the main reason is that the underground seawater with higher temperature is extracted. The intake seawater temperature is very sensitive to the seepage velocity in a range, and the flow quantity of pump seawater should not be too large under limited engineering conditions. The simulation results are foundations for further successful SWHP system engineering.

Geological, geochronological and geochemical constraints on the Tianhu iron deposit, Chinese Tianshan Orogen, NW China: A modified Algoma-type BIF deposit

The Tianhu large Fe deposit (104Mt @ 42%) contains bedded- and lenticular-shaped orebodies hosted by the metamorphosed Neoproterozoic Tianhu Group in the Chinese Tianshan Orogen, NW China. In this study, an integrated geological, age and geochemical investigation was conducted to decipher whether the deposit belongs to the long debated BIF- or skarn-type. A newly-measured cross-section shows that the orebodies are stratiform, in intrusive contact with migmatite, and are divided into the upper, middle and lower units by faults. The well-preserved primary banded ores are hosted in the lower unit, while sulfide veins crosscut the banded formation in the middle and upper units, indicating pre-existing Fe-rich sediments modified by later sulfide-bearing magmatic-metamorphic fluids. Petrographic observation has identified a biotite-sphene-epidote-K-feldspar-plagioclase-ilmenite metamorphic mineral assemblage, whilst phase equilibrium simulation indicates that the ore-hosting Tianhu Group (with volcanic protoliths) were amphibolite-facies metamorphosed at 7.8–8.8kbar and 605–635°C. The Tianhu migmatite is newly zircon U–Pb dated to be Middle Ordovician (469.6±2.3Ma and 469.3±1.7Ma). Geochemical features of the Tianhu Fe ores, including low Al2O3, TiO2 and HFSEs and the poor correlations among them, coupled with the presence of positive Y and Eu anomalies, point to a mixed ore-forming material source of high-temperature hydrothermal vent fluids and seawater. The negative Eu anomalies and REY patterns, atypical to BIFs, may have been derived from the sedimentary and hydrothermal apatite. The pyrite δ34S (−9.23 to +11.07‰), 206Pb/204Pb (19.513–21.156), 207Pb/204Pb (15.691–15.764) and 208Pb/204Pb (38.655–39.136) indicate that the pyrite may have been of a mixed primary sedimentary and later hydrothermal origin. Based on the new geological, age and geochemical data, we conclude that the Tianhu Fe deposit is a Neoproterozoic Algoma-type BIF deposit modified by Ordovician magmatic-metamorphic events.

Oceans as bioenergy pools for methane production using activated methanogens in waste sewage sludge

The dissolved CO2 that causes ocean acidification has great potential for bioenergy production. In this study, we demonstrate that activated methanogens in waste sewage sludge (WSS) are useful for converting bicarbonate in seawater into methane. These activated methanogens were adapted in different seawater sources for methane production through repeated batch experiments that resulted in an increase of 300–400 fold in the methane yield. During these repeated batch experiments, the microbial communities in WSS adapted to the high salinity of seawater to generate more methane. Microbial community analysis showed the dominance of Achromobacter xylosoxidans, Serrati sp. and methanogens including Methanobacterium sp., Methanosarcina sp., and Methanosaeta concillii. Using a 13C-labeled isotope, we demonstrate that 81% of the methane is derived from microbial conversion of NaH13CO2 in artificial seawater. Therefore, this study shows that oceans, with the largest surface area on Earth, have a potential as a substrate for methane energy production via an acclimated consortium approach.

Stable isotopes in surface waters of the Atlantic Ocean: Indicators of ocean‐atmosphere water fluxes and oceanic mixing processes

AbstractThe surface ocean hydrological cycle is explored based on ∼300 new δ18O and δD measurements from surface waters of the Atlantic Ocean and the Mediterranean Sea over the period 2010–2016. Our approach combines these surface observations with salinity (S) and stable isotope measurements of atmospheric water vapor. The distinct regional S‐δ distributions are used to identify different surface water masses and their horizontal advection. Moreover, based on assumptions on the δ‐S characteristics of seawater sources and the isotope composition of the evaporative (δe) and meteoric water (δMW) fluxes, the δ‐S distribution is used to indicate the relative importance of evaporation (E) and meteoric water inputs (MW). Here δe is estimated from the Craig and Gordon's equation using 120 days of measurements of the ambient air above the Atlantic Ocean collected during three cruises. To provide quantitative estimates of the E:MW ratio, we use the box model from Craig and Gordon (1965). This identifies the subtropical gyre as a region where E:MW ∼2 and the tropical ocean as a region were MW:E ∼2. Finally, we show that the δ18O‐δD distribution is better represented by a linear fit than the δ‐S relationship, even in basins governed by different hydrological processes. We interpret the δ18O‐δD distribution considering the kinetic fractionation processes associated with evaporation. In the tropical region where MW exceeds E, the δ18O‐δD distribution identifies the MW inputs from their kinetic signature, whereas in regions where E exceeds MW, the δ18O‐δD distribution traces the humidity at the sea surface.

Chemical and Sr isotopic characteristics of rainwater on the Alxa Desert Plateau, North China: Implication for air quality and ion sources

The major ions and Sr isotopes in rainwater have been studied during 2013–2015 on the Alxa Desert Plateau in order to identify the source of rainwater chemistry and to assess air quality in the desert area of northern China. The pH and EC values of rainwater vary from 6.7 to 8.1 and from 35 to 1237μScm−1, respectively, at the two meteorological stations (AYQ and YBL) in the Alxa Desert Plateau. Ca2+, SO42−, Na+ and Cl− are the dominant ions in rainwater, possessing >85% of total ions. The mean daily wet deposition fluxes of soluble ions are 8709μeq/m2/d at YBL and 5459μeq/m2/d at AYQ, approaching the values at Xi'an, Beijing, Guangzhou, and Chengdu. Statistical analysis shows that SO42− and NO3− in rainwater were mainly from anthropogenic sources while Ca2+ and K+ originated from terrestrial sources. Cl− was mainly from seawater sources, and Na+ was partly from mineral weathering. Major ions are well correlated with each other in rainwater, revealing that substances of various origins were synchronously carried into the atmosphere by wind. By using Sr isotope techniques, three main end-members controlling base cations of rainwater are identified: silicates, carbonates and seawater. Based on the analyses of acid-soluble fractions of desert soils, local soil dust could be the most important source of base cations in rainwater whereas the effect of the anthropogenic sources could be neglected.

Purple haze: Combined geochemical and Pb-Sr isotope constraints on colourants in Celtic glass

The composition of 2977 Late Prehistoric glass objects was investigated to derive information on the nature of the colourants used. 2673 Late Iron Age Celtic (La Tène) bracelet fragments from the Netherlands and Austria and 51 Early Iron Age beads from the Netherlands were analysed. Hand-held XRF analyses demonstrated that all glass objects were of the soda-silica-lime type, which has a presumed origin in the Eastern Mediterranean. Copper was used as colourant, in the form of copper filings, in most of the Early Iron Age glass beads to give recycled glass a blue-green colour.The vast majority (98%) of the translucent Iron Age glass, was coloured using cobalt (blue), manganese (purple; colourless), antimony (colourless) and iron (green). Manganese, however, was added to all glass, contributing additional amounts of elements like copper, cobalt and iron. Opaque decorations were produced using antimony, or a combination of tin and lead.REE analyses on a selection of representative objects indicate that the manganese ores in translucent glass are of hydrogenetic-diagenetic (Early Iron Age) or hydrothermally influenced diagenetic (Late Iron Age) types. Strontium isotope ratios show mixing between a calcite-related seawater source (0.709) and manganese ores with isotope ratios of ∼0.70766. Lead isotope ratios are dominated by colourant-derived Pb. The isotope ratios of the manganese used to produce translucent glass and lead used for opaque glass decorations fall in the same range. The most likely general provenance of both lies on Lavrion or the Western Cycladic Islands, although an origin in the central Taurus or the Sinai mountains cannot be excluded. The conclusion is that manganese ore used for colourants contributes significantly to the REE concentration in the glass, including Nd, as well as to Sr and Pb. This needs to be taken into account when using concentrations or isotope ratios of these elements for provenancing other raw materials like sand and calcium carbonate. This appears to be the case for all antique soda-lime-silica glass.