Seawater Concentrations Research Articles

Solar-driven hydrogen evolution in alkaline seawater over earth-abundant g-C3N4/CuFeO2 heterojunction photocatalyst using microplastic as a feedstock

Production of sustainable H2 fuel by photoreforming plastic waste is an emerging novel approach to tackling environmental pollution and energy shortage. We developed a n-p heterojunction g-C3N4/CuFeO2 photocatalyst made of only earth-abundant elements using a simple and scalable process. The heterostructure effectively suppresses the charge recombination, which is evident from a significant reduction in the emission of photoluminescence in g-C3N4/CuFeO2 compared to that of g-C3N4. g-C3N4/CuFeO2 exhibits promising performance in photoreforming various kinds of polyester plastics. Notably, g-C3N4/CuFeO2 outperforms g-C3N4 and CuFeO2, showing more than 60-fold and 100-fold enhanced activity for H2 evolution by photoreforming hydrolyzed polyester microfiber, respectively. On the other hand, the nuclear magnetic resonance study suggests formate is the main oxidizing organic product. Interestingly, g-C3N4/CuFeO2 can also perform photoreforming using non-pretreated plastics in alkaline solutions. g-C3N4/CuFeO2 maintains 84 % of activity toward H2 evolution by replacing pretreated poly(butylene succinate) solution with non-pretreated poly(butylene succinate) as the feedstock. Given the freshwater resource shortage, seawater, the most abundant on Earth, also served as the water resource under investigation. g-C3N4/CuFeO2 photocatalyst preserves its almost intact photocatalytic activity by replacing pure water with 25 % content seawater, although a decrease in activity is observed in higher seawater content. Activities for H2 evolution of 241 ± 6.2 μmol h−1 gcat−1 and 150 ± 8.2 μmol h−1gcat−1 were achieved by photoreforming hydrolyzed polyester microfiber over g-C3N4/CuFeO2 in 25 % and 100 % seawater content, respectively. This study demonstrates that non-toxic and noble-metal-free g-C3N4/CuFeO2 serves as an efficient and well environmentally adaptive photocatalyst for plastic reforming.

Low cobalt inventories in the Amundsen and Ross seas driven by high demand for labile cobalt uptake among native phytoplankton communities

Abstract. Cobalt (Co) is a scarce but essential micronutrient for marine plankton in the Southern Ocean and coastal Antarctic seas, where dissolved cobalt (dCo) concentrations can be extremely low. This study presents total dCo and labile dCo distributions measured via shipboard voltammetry in the Amundsen Sea, the Ross Sea and Terra Nova Bay during the CICLOPS (Cobalamin and Iron Co-Limitation of Phytoplankton Species) expedition. A significantly smaller dCo inventory was observed during the 2017/2018 CICLOPS expedition compared to two 2005/2006 expeditions to the Ross Sea conducted over a decade earlier. The dCo inventory loss (∼ 10–20 pM) was present in both the surface and deep ocean and was attributed to the loss of labile dCo, resulting in the near-complete complexation of dCo by strong ligands in the photic zone. A changing dCo inventory in Antarctic coastal seas could be driven by the alleviation of iron (Fe) limitation in coastal areas, where the flux of Fe-rich sediments from melting ice shelves and deep sediment resuspension may have shifted the region towards vitamin B12 and/or zinc (Zn) limitation, both of which are likely to increase the demand for Co among marine plankton. High demand for Zn by phytoplankton can result in increased Co and cadmium (Cd) uptake because these metals often share the same metal uptake transporters. This study compared the magnitudes and ratios of Zn, Cd and Co uptake (ρ) across upper-ocean profiles and the observed order-of-magnitude uptake trends (ρZn > ρCd > ρCo) that paralleled the trace metal concentrations in seawater. High rates of Co and Zn uptake were observed throughout the region, and the speciation of available Co and Zn appeared to influence trends in dissolved metal : phosphate stoichiometry and uptake rates over depth. Multi-year loss of the dCo inventory throughout the water column may be explained by an increase in Co uptake into particulate organic matter and subsequently an increased flux of Co into sediments via sinking and burial. This perturbation of the Southern Ocean Co biogeochemical cycle could signal changes in the nutrient limitation regimes, phytoplankton bloom composition and carbon sequestration sink of the Southern Ocean.

Hands-on Hypoxia: Engaging High School Educators in the science behind Marine Microbial Dynamics in Hypoxic Coastal Areas Through Field and Classroom Experiences

The University of Southern California’s (USC) Joint Educational Project’s STEM Education Programs hosted a three-day summer workshop focused on marine microbiology and coastal deoxygenation for high school educators. To increase ocean literacy in high school students from Title I schools, topical marine science research was translated into four lesson plans appropriate for classrooms that teach biology and environmental science. The lesson plans focus on how marine microbes affect and are affected by the dissolved oxygen content of seawater but covered diverse oceanography topics including microbial ecology, nutrient cycling, physical ocean dynamics, and climate change. This education framework was designed to promote and facilitate hands on discovery-based learning and making observations about the natural world. The workshop and lesson plan development were executed in partnership with faculty and graduate students researching marine microbes and oceanography from USC’s Marine and Environmental Biology department to provide scientific expertise on the subject matter. At the workshop, educators were guided through each lesson plan and given classroom sets of materials to complete each of the experiments in their own classrooms. Educators also had the opportunity to experience the academic research process at both USC and the Wrigley Institute of Environmental Studies on Catalina Island, California. Teachers valued this interactive experience to learn from professional scientists and STEM educators. They left the workshop equipped with the knowledge and confidence to teach these marine microbiology and biogeochemistry concepts in their classrooms.

Effect of ocean warming on pigment and photosynthetic carbon fixation of plankton assemblage in Pingtan Island of Southeast China

Temperature plays an important role in affecting the physiological traits of marine plankton. In this study, we conducted an outdoor incubation experiment to investigate the effects of elevated temperature on Chl a, photosynthetic carbon fixation and the composition of plankton communities in the surface seawater around Pingtan Island, the northwest Taiwan Strait in Autumn 2022. After 3–4 days of incubation, elevated temperature (1–4 °C higher than ambient temperature) led to a decrease in Chl a concentration across all three stations, did not result in significant increases in the particulate organic carbon (POC) and nitrogen (PON) concentrations in seawater with high nitrate concentrations, whereas increased POC and PON concentrations in nitrate-limited seawater. These findings suggest that the effect of temperature on the POC and PON contents of plankton is affected by the availability of nitrate. Diatoms were the dominant phytoplankton group in all three stations. Our results indicate that ocean warming has a potential to increase the POC contents of marine plankton per volume of seawater, which may increase the ability of phytoplankton to absorb atmospheric CO2 and to alleviate global warming.

Sensitive analysis of selenium speciation in natural seawater by isotope-dilution and large volume injection using PTV-GC-ICP-MS

Although oceans play a key role in the global selenium (Se) cycle, there is currently very little quantitative information available on the distribution of Se concentrations and Se speciation in marine environments. In general, determining Se concentration and speciation in seawater is highly challenging due to very low Se levels ((sub)ng⋅L−1), whereas matrix elements interfering Se pre-concentration and detection are up to the g⋅L−1 levels. In this study, we established a sensitive method for the determination of the various Se chemical fractions present in natural seawater, i.e. selenite (SeIV), selenate (SeVI), organic Se-II + Se0 and total Se, using species-specific isotope dilution gas chromatography coupled to inductively coupled plasma mass spectrometry (ID-GC-ICP-MS). We compared different derivatization reagents and optimized specific pre-treatment protocols, including a microwave assisted oxidation protocol for the determination of total Se and organic Se-II + Se0 using H2O2. To increase sensitivity, we developed an online pre-concentration method based on large volume injection (LVI) using a programmed temperature vaporization (PTV) inlet. Eventually, the developed method achieved low absolute and methodological detection limits, i.e., respectively, 0.1–0.3 pg and 0.9–3.1 ng.L-1 for the different fractions. The accuracy of our method was of 2% for a certified reference material (CRM) diluted in artificial seawater while the precision was better than 4% for a freshwater CRM in artificial seawater matrix as well as two common seawater CRMs certified for trace elements excluding Se. As a proof-of-concept, we quantified the various Se fractions in a large number of natural water samples from the Baltic and North Seas, encompassing a wide range of salinity (7–35 psu), which shows that its detection limits are sufficient to determine total Se, SeIV, SeVI and organic Se-II + Se0 concentrations in brackish and marine systems.

Monitoring of 137Cs, 239+240Pu, and 90Sr in the marine environment of South Korea and their impact on marine biota: 10 years after the Fukushima accident

This study conducted an analysis of the behavior of radionuclides and assessment their radioactive risk based on seawater and seabed sediment samples gathered from the East, South, and Yellow Seas of South Korea over the period from 2011 to 2020. The distribution for each radionuclides in seawater obtained from the East, South, and Yellow Seas were similar. However, the concentrations of 137Cs and 239+240Pu in sediments from the East Sea were observed to be higher compared to those from the South and Yellow Seas. This variation can be attributed to differences in the ocean inflow, water column properties, and seabed characteristics among the seas around South Korea. There were no statistically significant differences between the radioactive concentrations of seawater and seabed samples collected before and after the Fukushima accident, and no areas with unusually high radiation levels were detected. Using the distribution coefficient (Kds) and the concentration ratio (CR) calculated from the 2011-to-2020 data, we evaluated the radiological impact on fish. The ERICA tool was utilized to assess these data, and indicated a negligible radiological risk from radioactivity in the seawater, seabed sediments, and marine biota in the South Korean Ocean.

Taxonomic Identification of the Arctic Strain Nocardioides Arcticus Sp. Nov. and Global Transcriptomic Analysis in Response to Hydrogen Peroxide Stress.

Microorganisms living in polar regions rely on specialized mechanisms to adapt to extreme environments. The study of their stress adaptation mechanisms is a hot topic in international microbiology research. In this study, a bacterial strain (Arc9.136) isolated from Arctic marine sediments was selected to implement polyphasic taxonomic identification based on factors such as genetic characteristics, physiological and biochemical properties, and chemical composition. The results showed that strain Arc9.136 is classified to the genus Nocardioides, for which the name Nocardioides arcticus sp. nov. is proposed. The ozone hole over the Arctic leads to increased ultraviolet (UV-B) radiation, and low temperatures lead to increased dissolved content in seawater. These extreme environmental conditions result in oxidative stress, inducing a strong response in microorganisms. Based on the functional classification of significantly differentially expressed genes under 1 mM H2O2 stress, we suspect that Arc9.136 may respond to oxidative stress through the following strategies: (1) efficient utilization of various carbon sources to improve carbohydrate transport and metabolism; (2) altering ion transport and metabolism by decreasing the uptake of divalent iron (to avoid the Fenton reaction) and increasing the utilization of trivalent iron (to maintain intracellular iron homeostasis); (3) increasing the level of cell replication, DNA repair, and defense functions, repairing DNA damage caused by H2O2; (4) and changing the composition of lipids in the cell membrane and reducing the sensitivity of lipid peroxidation. This study provides insights into the stress resistance mechanisms of microorganisms in extreme environments and highlights the potential for developing low-temperature active microbial resources.

PH-Dependent Dual-Mode Detection toward Uranium by a Zinc-Tetraphenylethylene Fluorescent Metal-Organic Framework.

An interpenetrated tetraphenylethylene-based fluorescent metal-organic framework (ECUT-180) with exceptional sensitivity, excellent selectivity, and fast response (less than 30 s) toward uranium was successfully prepared. Especially, in the prescence of uranyl, ECUT-180 displays significant fluorescence turn-on under pH 2-3, while fluorescence turn-off under pH 4-8. The corresponding detection limits were determined to be 2.92 ppb at pH 2 and 0.86 ppb at pH 8, both of which are lower than the average uranium content (3.3 ppb) in seawater. Mechanism investigation reveals that the fluorescence enhancement on the strong acid condition can be assigned to uranium adsorption, while the quenching is caused by the resonance energy transfer.

Corrosion of Brass Fishing Vessel Propeller in Artificial Seawater

The propeller was an important component in the fishing vessels marine propulsion system. Brass was widely used as a fishing vessel propeller. Brass was chosen because it has good mechanical properties and good corrosion resistance. The content of seawater in Indonesia has levels of 3% – 3.5% NaCl. In addition to the level of Ion Cl-, environmental factors can affect corrosion rate of material or metal. The environmental factors that affect the corrosion rate are the level of salinity, pH, DO, temperature and TDS. The objective of the present work was to explain the corrosion rate of brass in artificial seawater in Indonesia with exposure time. The material used for research is fishing vessel propeller commercial in Indonesia market. Measurement of the corrosion rate of brass used the principle of weight loss according to ASTM G31-72 (2004). During the corrosion test, the artificial seawater solution was tested for its pH and salinity quality over time of immersion. The result of immersion brass in the artificial seawater shows that the corrosion rate decreases in 1-to-10-days exposure time due to the increase in salinity levels above 30‰. While the results of exposure time immersion above 15 days tends to increase the corrosion rate due to a decrease in pH level. pH level of seawater depends on the environmental conditions and tends not to change significantly.
 Keyword: Artificial Seawater, Brass, Corrosion Rat, pH, Salinity.

Phosphorous concentration in iron-rich rocks of the Chilpi Group, Bastar Craton, India: implications on late Palaeoproterozoic seawater palaeo-productivity

AbstractThe concentration of the bio-limiting nutrient element, phosphorus (P), in seawater is important for primary marine productivity and the evolution of life on geological time scales. The molar percentage of P/Fe in banded iron formations (BIF) and iron oxide-rich chemical sediments is a good proxy for the first-order approximation of seawater P concentration. Bio-available concentration of phosphorus in Precambrian, especially during the late Palaeoproterozoic Era (2.0–1.8 Ga), is poorly constrained. We evaluated the P/Fe ratios of iron-rich rocks from the late Palaeoproterozoic Chilpi Group, Bastar Craton, Central India. The bulk rock molar percentage of P/Fe ratios of the Chilpi rocks vary between 0.11 and 1.17 (average 0.51 ± 0.3), and the average of EPMA spot analysis P/Fe molar ratio is 0.32 ± 0.4; both have values similar to Archaean BIFs of the world. The observed low molar ratio is not an artefact of contamination from terrestrial sources, diagenetic alterations or high-temperature hydrothermal inputs; it indicates the deposition from phosphorus-lean seawater. The modelled P/Fe molar ratio in the Chilpi Group suggests that the concentration of phosphorus in the shallow marine environment was less than 0.12 μM. The low level of phosphorus concentration in seawater during the late Palaeoproterozoic Era is interpreted to be a consequence of the low primary production during a period of low atmospheric oxygen content, which might have impeded the evolution of eukaryotes.

A Quantitative interpretation of salt water mixture in the shallow aquifer through the geoelectrical resistivity data

The main problem of groundwater in coastal areas is the intrusion of saltwater into freshwater aquifers. This study aims to predict the amount of saltwater content in aquifers polluted by intro-sea saltwater. In this study, an attempt is made to provide a direct correlation approach for resistivity measurements with the physical characteristics of groundwater. A 2D resistivity survey with the Wenner configuration have been carried out in the coastal area. The geoelectrical resistivity survey is about 3 km from the shoreline. The chemical measurement was done on freshwater, seawater and fresh-seawater mixture, which the mixture was consisted of 25%, 50% and 75% of seawater content. The results showed that the resistivity below 5 ohm.m indicated the presence of seawater with a concentration of more than 50% mixed with fresh water. In general, it can be seen that the decrease in resistivity appears to decrease exponentially with increasing seawater content in the aquifer.

User Acceptance for Multitask IoT Monitoring and Controlling System for Salt Ponds

The process of making salt is still done manually by filling water into reservoirs and plots which require salt farmers to visit their farms periodically. This is mainly because the speed of the salt crystalization process is always inconsistent due to salt concentration in seawater and the weather. This study aims to build a new prototype of a water level monitoring system in reservoirs and plots in salt ponds then measure the water's salinity value, which will be reported to the farmers. The method used in this research is prototyping, which includes system requirement analysis, rapid design, prototype building, system evaluation, and system improvement. The system was tested using the black box method, namely testing all system functionality and determining user satisfaction with questionnaires. The functionality test results, including monitoring the water level and the pump control, show that the prototype functions correctly. The designed system can send information in the form of water level values in reservoirs, water levels in plots, and salinity values with linear sensor accuracy with measurement results with conventional measuring instruments with standard error values of 0.485, 0.44, and 0.72, respectively. Applying this system will ease farmers’ monitoring of water levels and controlling irrigation in reservoirs and plots.

Deep utilization of salinity gradient energy between concentrated seawater and river water by multi-stage reverse electrodialysis

While concentrated seawater discharged by desalination plants requires considerable efforts to alleviate undesired environmental risk, the conversion of salinity gradient energy to electric energy is considered an ideal way. In this work, the experiment and simulation of multi-stage reverse electrodialysis (MS-RED) were carried out, and the influence of flow rate and compartment thickness of high concentration compartment (HCC) and low concentration compartment (LCC) on the MS-RED performance were investigated independently for the huge concentration difference between HCC and LCC. The optimized flow rates of LCC and HCC were 0.96 cm·s−1 and 0.71 cm·s−1, and the compartment thicknesses of LCC and HCC were 1.05 mm and 0.85 mm, respectively. Furthermore, the performance of series multi-stage reverse electrodialysis (SMS-RED) and independent multi-stage reverse electrodialysis (IMS-RED) was compared, and SMS-RED showed better performance than IMS-RED. With the optimized conditions of SMS-RED, the power generation and energy efficiency were reached 684.07 W and 16.22 % after 20 stages, respectively, while the concentration of concentrated seawater was reduce from 66.70 to 37.63 g·L−1. The results can provide a theoretical basis for the industrial development of MS-RED to achieve the deep utilization of concentrated seawater and reduce the environmental risks of its direct discharge.

In situ temperature-compensated ultraviolet spectrophotometry to estimate nitrate and chloride concentrations in estuarine seawater with different salinity and composition

Various methods have been proposed for in situ measurement of nitrate concentrations from the ultraviolet (UV) absorbance spectrum of seawater with stable salinity and constituents. However, salinity and temperature affect the UV absorption spectrum of seawater. In sea areas with large variability in salinity and water temperature, accurate nitrate ion concentration measurements remain challenging. We performed in situ measurements of nitrate, chloride, and bromide in estuarine seawater with different salinity compositions and applied water temperature compensation. First, the impact of water temperature on the UV absorbance of chloride, bromide, and nitrate was experimentally investigated and represented in a mathematical model. Next, chloride, bromide, and nitrate concentrations were estimated by suppressing the impact of residual components from the UV absorbance spectra of seawater using principal component regression (PCR). Hence, the chloride, bromide, and nitrate concentrations were determined by measuring the UV absorbance spectrum of seawater alone, without measuring water temperature and electrical conductivity. The proposed method was more accurate (±1.39 μM below 100 μM and ±0.90 μM below 20 μM) than the conventional method (±2.35 μM below 100 μM and ±1.88 μM below 20 μM) and PCR without water temperature compensation (±3.67 μM). In a field study, an in situ UV spectrophotometer with water temperature compensation was used to measure depth profiles of nitrate concentrations in estuarine seawater. We successfully measured the depth profiles of low chloride and high nitrate concentrations in the surface layer as well as high chloride and low nitrate concentrations in the lower layer. The proposed method enables in situ measurements of nitrate concentrations in waters with either stable or highly variable salinity and composition. Unlike conventional chemical analysis, our method can describe detailed spatiotemporal variations in nitrate concentrations.

Seafloor hydrothermal systems control long-term changes in seawater [Li+]: Evidence from fluid inclusions.

Secular variations in the major ion chemistry and isotopic composition of seawater on multimillion-year time scales are well documented, but the causes of these changes are debated. Fluid inclusions in marine halite indicate that the Li concentration in seawater [Li+]SW declined sevenfold over the past 150 million years (Ma) from ~184 μmol/kg H2O at 150 Ma ago to 27 μmol/kg H2O today. Modeling of the lithium geochemical cycle shows that the decrease in [Li+]SW was controlled chiefly by long-term decreases in ocean crust production rates and mid-ocean ridge and ridge flank hydrothermal fluxes without requiring changes in continental weathering fluxes. The decrease in [Li+]SW parallels the 150 Ma increase in seawater Mg2+/Ca2+ and 87Sr/86Sr, and the change from calcite to aragonite seas, KCl to MgSO4 evaporites, and greenhouse to icehouse climates, all of which point to the importance of plate tectonic activity in regulating the composition of Earth's hydrosphere and atmosphere.

Potential to produce brown mussel integrated to a net-cage fish farm in a Mediterranean bay

In this study, we investigated the potential exploitation of the brown mussel Perna perna (Linnaeus, 1758) in an aquaculture farm (Monastir Bay, Mediterranean Sea, Tunisia). The quality of seawater as well as performance indicators such as Condition Index, length, weight, growth and frequency distribution of the mussel were determined over an annual cycle; from July 2017 to August 2018. Interestingly, P. perna has an extended sexual cycle during the year with two main spawning periods, the first in spring and the second in autumn, when suspended matter and Chlorophyll a were at their maximum concentrations in seawater. Spat mussels and young mussels showed significant growth rates from 1 July 2017 to 31 October 2017. Adult mussels exhibited negative allometric growth and a modal size of 41 to 50 mm. Results showed that several potentially toxic microalgae species developed at low densities in this marine zone. By using Solid Phase Adsorption Toxins Tracker (SPATT); lipophilic toxins including Okadaic acid and yessotoxins were detected at low levels in seawater and may be involved in the positive LSTs (lipophilic shellfish toxins) mouse bioassays in P. perna during the autumn. No other toxins such as paralytic shellfish toxins or amnesic shellfish toxins nor pathogenic bacteria or viruses were detected in P. perna. Altogether, our results suggest that finfish farms in Monastir Bay could be suitable sites for farming P. perna.

High dimethylsulfoniopropionate concentrations in the surface seawater over the marginal seas of China and the Northwest Pacific Ocean during May–July of 2021 following La Niña

The total dimethylsulfoniopropionate (DMSPt) concentrations over the surface seawater of China's marginal seas and the northwest Pacific Ocean (NWPO) in May–July 2021 (during the recessional period of La Niña) were analysed. The results showed that the DMSPt concentrations in the marginal seas of China varied from 4.73 to 775.96 nmol L−1, with an average value of 111.42 ± 129.30 nmol L−1 (average ± standard deviation). It was 2–12 times higher than those previously measured in the same seas and in the NWPO in this study. Significant positive correlations between DMSPt, chlorophyll-a and surface seawater temperature (SST) were observed in the SYS, the ECS and the NWPO. Moreover, their abnormally high SST was related to La Niña. These results suggested that high phytoplankton abundance was caused by abnormally high SST following La Niña, which further promoted DMSPt concentration increases. However, the increase of DMSPt was also related to other factors such as nutrients.

Seepage Analysis and the Reservoir Water Pollution Potential under Vertical Dam Structure Planning

A prospective resolution to the intricate predicaments of flooding, sanitation, and the availability of unprocessed water for the populace of Jakarta residents is the implementation of the coastal reservoir paradigm. This paradigm entails harnessing the latent capacity of the Cisadane River flow and its subsequent storage within a retention pond, and then subjecting it to reprocessing to serve as a viable source of raw water. The selection of a vertical seawall design was based on the objective of creating an effective barrier between the reservoir and the sea, while also considering several environmental factors. This design was selected with the aim of minimizing the need for extensive soil excavation and rock placement. However, it is important to note that the risks of construction failure associated with seepage under hydraulic structure and dam stability pose significant challenges. Besides preventing saltwater intrusion and maintaining the integrity of the reservoir as a freshwater source, dam must be designed to mitigate potential seepage failure and intrusion issues. To address these concerns, this study employed numerical simulation using the SEEP/W and CTRAN/W software. The simulation was carried out to analyze seepage discharge under a vertical dam and predict potential seawater intrusion into the reservoir. The dam was examined over a ten-year period, with varying embankment widths of 10m, 20m, and 30m. The analysis considered changes in water level (ΔH) and the addition of a cut-off wall at depths of 5m, 10m, and 15m. The obtained results showed that seepage discharge rates amounted to 3,14x10-4 m3 s-1, 2,67x10-4 m3 s-1, and 2,50x10-4 m3 s-1 for embankment widths of 10m, 20m, and 30m, respectively, under a 1m level difference condition. Following this, the safety factor for piping on vertical embankment was determined as 1.10, 1.34, and 1.39 for widths of 10m, 20m, and 30m, respectively. This factor was found to increase to 4.03 when the embankment distance was widened, and a 15m deep cut-off wall was installed. It is important to note that the seawater intrusion model predicted a seawater concentration of 65,12 g m-3 at the bottom for an embankment width of 10m, while no intrusion was observed at widths of 20m and 30m with ΔH=1m. This study aims to assess potential risks of piping due to seepage and seawater contamination at the Cisadane Estuary.

Refined views of ancient ocean chemistry: Tracking trace element incorporation in pyrite framboids using atom probe tomography

The trace element chemistry of pyrite can be used to determine the origin, timing, and conditions of formation of ore deposits; as a vectoring tool for mineral exploration; and to determine the evolution of the Earth’s oceanic and atmospheric chemistry. However, little is known about whether trace elements are held with the pyrite structure or within nano-inclusions of other phases. This distinction is important for two primary reasons. First, trace element incorporation into the pyrite structure can affect the partitioning of other trace elements. Second, if trace elements are held within nano-inclusions, the partition coefficient of the mineral phases that make up the nano-inclusion, rather than pyrite, are the critical consideration in related interpretations. Previous studies addressing this topic have used laser ablation inductively coupled plasma mass spectrometry; however, the resulting data do not provide sufficient spatial resolution to delineate trace element distributions unless the inclusions are large. Further, they use these flat element profiles in time resolved laser ablation output graphs to argue that pyrite trace element content provides a direct relationship between trace element content of seawater and pyrite trace element content. To improve resolution, we have used atom probe tomography to characterize trace element distributions in pyrite framboids from the Cariaco Basin and Demerara Rise in three-dimensions at sub-nanometer resolution. Manganese was found to be concentrated in the pyrite nanocrystal part of the original framboid structure. In contrast, Ni was mostly found along the grain boundary, though it still appeared to be contained within the pyrite structure. Copper was concentrated in later pyrite overgrowths, and As varied in its location. These observations suggest that some important trace elements are incorporated into pyrite during early diagenesis, even in euxinic settings dominated by water-column pyrite formation. Statistical analysis was used to determine whether trace elements were incorporated in the lattice or within nanoscale inclusions (referred to here are nano-inclusions). We found that As, Ni, Cu, and Mn were commonly held within the pyrite structure, but As, Ni, and Cu can also be held as nano-inclusions or within grain interfaces. Incorporation of As is known to enhance the incorporation of other trace elements and in this case appears to correlated to elevated Ni and Cu concentrations in the Cariaco Basin samples. Understanding these relationships strongly impacts our ability to utilize pyrite trace metal concentrations to analyze and quantify early ocean chemistry and its evolution through time.

Organophosphate Esters in Air and Seawater of the South China Sea: Spatial Distribution, Transport, and Air-Sea Exchange.

Organophosphate esters (OPEs) have become one group of chemicals with emerging concern in the marine environment. In this work, we investigated OPEs in the air and seawater of the South China Sea in summer 2019. The concentrations of ∑10OPEs in the atmosphere ranged from 66 to 550 pg/m3, with TCIPP, TNBP, TPhP, and TEP predominating in the air. The total dissolved OPE concentrations (∑10OPEs without TEP) measured in high-volume water samples ranged from 300 to 3600 pg/L, with a mean concentration of 1180 ± 910 pg/L. TEP was measured with liquid-liquid extraction (LLE), and it showed the highest concentration (average 2000 ± 1450 pg/L) among the selected OPEs. Total suspended matter associated OPEs accounted for less than 4.7% of the sum of OPE concentrations in seawater. Fugacity fractions and air-sea exchange fluxes showed that TCEP, TCIPP, TIBP, TEHP, TPhP, and EHDPP were favored to volatilize, TEP dominated the deposition, while TPrP and TNBP varied between volatilization and deposition. Atmospheric particle deposition fluxes ranged from 5 to 71 ng/m2/day with an average of 17 ± 15 ng/m2/day. The input of ∑OPEs to the entire South China Sea via atmospheric particle deposition was estimated to be 22 ± 19 tons/year, while the net air-sea exchange fluxes of OPEs were volatilization from seawater to air with an average of 44 ± 33 tons/year. This work suggests that air-sea exchange and atmospheric particle deposition are significant processes interfering with the transport of OPEs in the marine environment.