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The research delved into the occurrence and dynamics of dissolved metals, specifically manganese (Mn) and copper (Cu), within the Jiulong River Estuary, South China, a medium-sized subtropical estuary. Our findings unveiled a nuanced seasonal and spatial variability of dissolved metals throughout the entire estuarine system. Notably, dissolved Mn concentrations peaked (~ 3.5 μM) in the upper estuary, diminishing sharply along the salinity gradient, with a modest rise in the middle estuary and outer Xiamen Bay. In the upper estuary, heightened concentrations of dissolved Mn occurred in spring due to augmented terrestrial particle inputs, followed by suboxically reductive releases; conversely, concentrations were low in summer, attributed to dilution from increased freshwater discharges and particle scavenging. In contrast, dissolved Cu exhibited differently, with elevated concentrations (29.2–37.5 nM) in the upper and middle estuaries, driven by reductive dissolution of Mn particles and chloride-induced ion exchanges, respectively. Concurrently, heightened inputs of nutrients and metals correlated with elevated phytoplankton productivity (indicated by chlorophyll a) in the upper and outer estuary regions. Our analysis underscored the sensitivity of dissolved metals to environmental parameters, including temperature, pH, and dissolved oxygen. The integration of compiled historical data underscored the dynamic nature of dissolved metals, particularly Cu, in response to geochemical processes.The elevated ion levels indicated intensified ion releases from particles and sediments, attributable to increased anthropogenic perturbation and climatic changes (e. g. ocean warming). [ABSTRACT FROM AUTHOR]

Dissolved (<0.2 μm) trace metals (dTMs) including iron (Fe), manganese (Mn), and cobalt (Co) are micronutrients that (co-) limit phytoplankton growth in many ocean regions. Here, we present the spatial and seasonal distributions of dFe, dMn, and dCo on the Northeast Atlantic continental margin (Celtic Sea), along a transect across the shelf and two off-shelf transects along a canyon and a spur. Waters on the continental shelf showed much higher dTM concentrations (dFe 0.07–6.50 nmol L−1, average 1.41 ± 0.96 nmol L−1, n = 138; dMn 0.868–14.8 nmol L−1, 2.75 ± 2.37 nmol L−1, n = 148; dCo 54.8–217 pmol L−1, 109 ± 32 pmol L−1, n = 144) than on the slope (dFe 0.03–1.90 nmol L−1, 0.65 ± 0.43 nmol L−1, n = 454; dMn 0.223–1.14 nmol L−1, 0.58 ± 0.20 nmol L−1, n = 458; dCo 27.3–122 pmol L−1, 71.7 ± 11.7 pmol L−1, n = 441), attributed to strong dTM contributions from a low-salinity endmember, i.e., riverine discharge. Benthic sedimentary input via reductive dissolution (especially for dFe and dMn), delineated by short-lived radium (Ra) isotopic activities (223Ra xs and 224Ra xs), was only prominent at a station (Site A) characterized by fine sediments. On the continental slope, dMn levels at depth were mainly determined by the formation of insoluble Mn oxides and the intrusion of Mediterranean Outflow Waters. In contrast, dFe and dCo concentrations at depth were balanced by the regeneration from remineralization of sinking organic particles and scavenging removal. In addition, bottom and intermediate nepheloid layers along the slope illustrated both elevated dTM concentrations and Ra isotopic activities. The presence of nepheloid layers is especially significant along the canyon transect relative to the spur transect, demonstrating the importance of slope topography on the off-shelf transport of dTMs into the Northeast Atlantic Ocean. As a seasonal stratified shelf sea, dTMs and nutrients showed synchronized seasonal variations on the shelf, indicating the influence of biological processes in addition to source effects. Surface dFe and dCo were depleted in summer due to enhanced biological uptake, while sub-surface dFe and dCo were elevated in summer and autumn ascribed to the remineralization of sinking organic particles. In contrast, surface dMn levels were predominantly controlled by the seasonal variations in photoreduction, while sub-surface dMn concentrations were relatively constant throughout the year. The combined effects of fluvial and benthic sources, topographical controls, and biological processes shape the seasonal variations of dTM distributions. Such seasonal variations in dTMs and biological activities can affect the biological carbon pump on the Northeast Atlantic continental margin, and may further influence the carbon cycle in the Atlantic Ocean via the dynamic dTM exchange between continental margins and the open ocean. [ABSTRACT FROM AUTHOR]

Trace metals act as a limiting nutrient and prerequisite for primary productivity in marine environments. The distribution of metals in dissolved phase along the salinity gradients of Swarna, Sharavati and Kali estuaries in southwestern India, during post and pre-monsoon seasons, were studied. We have investigated the behaviour of trace metals in the estuarine environment and their extent of impact on human health and ecosystem. The study revealed, non-conservative behaviour of dissolved Mn, Fe, Ni, Cd and Co in the estuaries. Whereas Cu behaved non-conservatively in post-monsoon and conservatively in pre-monsoon seasons. Risk assessment studies revealed that higher chronic daily intake (CDI) in humans, through dermal pathway, in Swarna and Sharavati estuaries during post-monsoon, whereas it was during pre-monsoon season in the Kali estuary. Hazard Index values for the studied metals in adults and children are below risk thresholds, though children are more prone to health risk through the dermal pathway. [ABSTRACT FROM AUTHOR]

Water column physico‐chemical studies were conducted over the southern Central Indian Ridge between 24°44'S and 25°52'S to identify and chemically characterize seafloor hydrothermal activity. High turbidity values were observed between 2300 and 2700 m with two distinct layers, between water depths of 2320–2500 m and 2510–2650 m, at two closely spaced CTD stations at 24°48.62'S (CTD‐17‐P5) and 24°48.68'S (CTD‐17‐P8). Elevated concentrations of dissolved Mn (DMn: 19–112 nM), dissolved Fe (DFe: 33–88 nM), methane (CH4: 32–246 nM), elevated δ3He values (28%–88%), and stable carbon isotope ratios of CH4 confirm the hydrothermal origin. In plume layer‐1, the maximum concentrations were observed at 2375m at P8 and in plume layer‐2, the maximum concentrations were observed at 2570 m at P5. The stable isotope ratios of methane (δ13C‐CH4) show that heavier isotopes are enriched (−13.2‰ to −14.7‰) in the plume waters and are similar to vent fluids on the global mid‐oceanic ridges. Further, morphological and mineralogical studies of plume particles, collected from the plume layer‐2 maxima, clearly show the presence of barite, pyrite, chalcopyrite, and indicate possible venting of high‐temperature fluids in the vicinity of P5. Enrichment in methane relative to the other tracers and the general geochemical characteristics of these two plume layers, CH4/Mn (1.8–2.2); CH4/Δ3He (85–97 × 106), Mn/Δ3He (44–46 × 106), Fe/Δ3He (52–54 × 106), indicate that these plumes are formed from fluids released at the seafloor that circulated through ultramafic/gabbroic rocks. The high concentrations of dissolved gases and metals combined with the presence of sulfide particles in the water column provide evidence for a new ultramafic/gabbroic‐hosted hydrothermal vent field, at 24°49'S on the southern Central Indian Ridge. Plain Language Summary: Evidence for the seafloor hydrothermal activity was first discovered in 1970. Since then, numerous vent fields were discovered in Atlantic, Indian and Pacific Oceans. Among these three oceans, Indian Ocean is relatively less explored and most of the hydrothermal fields were discovered along the Central Indian Ridge. A multi‐disciplinary team, expertise in geophysics, geology, physical, chemical and biological oceanographers, has to work together to discover these fields. Extensive water column studies have been carried out on the southern Central Indian Ridge to identify plumes. High concentrations of manganese, iron, methane, and helium values between 2300 and 2700 m confirm the presence of hydrothermal plumes. The nature of the particles collected from these plumes shows that most of them are sulfides, sulfate and oxides of iron. The geochemical ratios in these plumes (combination of gas/metal and metal/gas) show that the fluid composition is controlled by ultramafic rocks. The chemical composition of both fluid and plume is mainly controlled by the rock type (basalt and/or ultramafic) of the sub‐seafloor. The high concentrations of gases and metals in the water column provide evidence for a new hydrothermal vent field, at 24°49'S on the southern Central Indian Ridge. Key Points: Chemical signatures in the deep waters of the southern Central Indian Ridge, at 24°49'S, provide evidence for hydrothermal plumesEnrichment of volatiles (helium and methane) over metals (manganese and iron) in plumes indicate the influence of ultramafic rocksPresence of sulfide and sulfate particles (pyrite, chalcopyrite and barite) in plumes may indicate the high‐temperature venting in the vicinity [ABSTRACT FROM AUTHOR]

Upwelling of subsurface waters injects macronutrients (fixed N, P, and Si) and micronutrient trace metals (TMs) into surface waters supporting elevated primary production in Eastern Boundary Upwelling Regions. The eastern South Atlantic features a highly productive shelf sea transitioning to a low productivity N‐Fe (co)limited open ocean. Whilst a gradient in most TM concentrations is expected in any off‐shelf transect, the factors controlling the magnitude of cross‐shelf TM fluxes are poorly constrained. Here, we present dissolved TM concentrations of Fe, Co, Mn, Cd, Ni, and Cu within the Benguela Upwelling System from the coastal section of the GEOTRACES GA08 cruise. Elevated dissolved Fe, Co, Mn, Cd, Ni, Cu and macronutrient concentrations were observed near shelf sediments. Benthic sources supplied 2.22 ± 0.99 μmol Fe m−2 day−1, 0.05 ± 0.03 μmol Co m−2 day−1, 0.28 ± 0.11 μmol Mn m−2 day−1 and were found to be the dominant source to shallow shelf waters compared to atmospheric depositions. Similarly, off‐shelf transfer was a more important source of TMs to the eastern South Atlantic Ocean compared to atmospheric deposition. Assessment of surface (shelf, upper 200 m) and subsurface (shelf edge, 200–500 m) fluxes of Fe and Co indicated TM fluxes from subsurface were 2–5 times larger than those from surface into the eastern South Atlantic Ocean. Under future conditions of increasing ocean deoxygenation, these fluxes may increase further, potentially contributing to a shift toward more extensive regional limitation of primary production by fixed N availability. Key Points: Shelf sediments release redox‐sensitive trace metals (TMs) to overlying oxygen‐depleted waters in the Benguela Upwelling SystemSediment‐derived TMs are upwelled and laterally transported constituting a major source to shelf waters and to the eastern South AtlanticSubsurface fluxes of dissolved Fe and Co from the shelf edge play an important role in supplying Fe and Co to the eastern South Atlantic [ABSTRACT FROM AUTHOR]

Abstract Water column physico‐chemical studies were conducted over the southern Central Indian Ridge between 24°44’S and 25°52’S to identify and chemically characterize seafloor hydrothermal activity. High turbidity values were observed between 2300 and 2700 m with two distinct layers, between water depths of 2320–2500 m and 2510–2650 m, at two closely spaced CTD stations at 24°48.62’S (CTD‐17‐P5) and 24°48.68’S (CTD‐17‐P8). Elevated concentrations of dissolved Mn (DMn: 19–112 nM), dissolved Fe (DFe: 33–88 nM), methane (CH4: 32–246 nM), elevated δ3He values (28%–88%), and stable carbon isotope ratios of CH4 confirm the hydrothermal origin. In plume layer‐1, the maximum concentrations were observed at 2375m at P8 and in plume layer‐2, the maximum concentrations were observed at 2570 m at P5. The stable isotope ratios of methane (δ13C‐CH4) show that heavier isotopes are enriched (−13.2‰ to −14.7‰) in the plume waters and are similar to vent fluids on the global mid‐oceanic ridges. Further, morphological and mineralogical studies of plume particles, collected from the plume layer‐2 maxima, clearly show the presence of barite, pyrite, chalcopyrite, and indicate possible venting of high‐temperature fluids in the vicinity of P5. Enrichment in methane relative to the other tracers and the general geochemical characteristics of these two plume layers, CH4/Mn (1.8–2.2); CH4/Δ3He (85–97 × 106), Mn/Δ3He (44–46 × 106), Fe/Δ3He (52–54 × 106), indicate that these plumes are formed from fluids released at the seafloor that circulated through ultramafic/gabbroic rocks. The high concentrations of dissolved gases and metals combined with the presence of sulfide particles in the water column provide evidence for a new ultramafic/gabbroic‐hosted hydrothermal vent field, at 24°49’S on the southern Central Indian Ridge.

The biogeochemical cycle of trace metals plays an important role in the coastal zone. The distribution, interaction, and biogeochemical behavior of dissolved trace metals in surface and bottom seawater are still unclear. This study analyzed the distribution and performed an ecological health risk assessment of dissolved trace metals (Zn, Cd, Co, Pb and Cr) in surface and bottom seawater in the summer (August) of 2019 and 2020 in the seawater of the Yantai offshore area, China. Zinc (Zn), cadmium (Cd), cobalt (Co), lead (Pb) and chromium (Cr) ranged from 23.76–117.47 μg/L (42.67 μg/L ± 15.15), 0.21–0.51 μg/L (0.30 μg/L ± 0.05), 0.90–2.94 μg/L (1.09 μg/L ± 0.31), 0.13–1.06 μg/L (0.39 μg/L ± 0.17), and 2.00–9.9 μg/L (5.38 μg/L ± 2.99) in the summer of the two years. The average metal (Zn and Co) concentrations were slightly higher than the other Chinese coastal areas, while the major contamination pressures were from Zn and Pb. The largest contaminants were in the following order: Zn > Pb > Cd > Cr > Co. Correlation analysis, principal component analysis and hierarchical cluster were used to determine the potential origins and cause the spatial distribution of the multiple dissolved trace metals. The major sources of the trace metal contamination in study area were identified as external inputs from natural human and atmospheric settling and the natural release of the trace metals in sediments under external disturbances. Riverine inputs, the Lubei coastal current and aquaculture significantly influenced the multi-parameter horizontal distributions of the dissolved trace metals and dissolved organic carbon. Although the growth of phytoplankton was strong in summer, the uptake of Zn, Cd, Co and Pb was negligible compared with the exogenous input. The concentrations of Zn, Cd, Co and Pb were higher in the surface than those in the bottom. Monsoons, tides and wind waves also influence the migration, transformation and distribution of dissolved trace metals and dissolved organic carbon. This study provides important information on the biogeochemical cycle process (migration and conversion) and distribution of dissolved trace metals at different depths in coastal and marine pasture areas.

Desalination remains in Saudi Arabia the supreme viable alternative to boost the future water supply requirements. The present research is focused on the environmental issue observations and modeling based on dissolved trace metals, hydrographic parameters, and nutrients at the discharging plume and nearby locations of Rabig desalination plant (RDP) and Yanbu desalination plant (YDP) located at the north of Jeddah city (~ 150 and 400 km, respectively). A multi-effect distillation (MED) technology is used in RDP whereas, in YDP, a combination of multistage flashing (MSF), reverse osmosis (RO), and MED technologies is in use for the production of potable waters. The concentration of dissolved Cu, Ni, and Zn was assessed by using cathodic stripping voltammetry. The observed pattern was reflecting an average value of dissolved Cu, Ni, and Zn at RDP that was 8.24, 5.28, and 12.69 nM, respectively. The correspondent changes at YDP were 17.53, 18.06, and 71.19 nM of Cu, Ni, and Zn, respectively. The statistical validation shows a significant positive correlation between metals and temperature with salinity and a significant negative correlation of dissolved oxygen and pH. The background concentration of nearby YDP is comparatively higher and which is ascribed by the negative effects of nearby industries. Detailed investigation of circulation pattern and brine discharge analysis near the Yanbu desalination plant also carried out with the help of 3d hydrodynamical numerical model Delft3d. [ABSTRACT FROM AUTHOR]

The dissolved (D) trace metals zinc (Zn), cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), titanium (Ti), lanthanum (La), yttrium (Y), and lead (Pb) were analyzed via ICPMS in samples from the Ross Sea obtained during a cruise between 20 December 2013 and 5 January 2014. The concentrations of DZn, DCd, DCo, DCu, DFe, DMn, DNi, and DTi were significantly lower in the Antarctic surface Water (AASW) compared to the other deeper water masses, indicating biological uptake and possibly scavenging. In the AASW, DLa and DY were higher than in Winter Water (WW). This can be explained by a spring source from ice melt followed by loss during summer and autumn, probably due to passive adsorption. Dissolved Pb was low (16 pM) and no distinction between water masses was possible. Akin to the macro-nutrients nitrate and silicate, the modified Circumpolar Deep Water (mCDW) shows elevated DCd compared to the shelf water masses. Sea ice melt and ice sheet melt released DZn, DFe, DMn, DNi, DY, DLa, and probably DPb into the Ross Sea. However, only DFe, DMn, DY and DLa are transported into the Antarctic Circumpolar Current with the outflowing High Salinity Shelf Water (HSSW). The bottom nepheloid layer (BNL) released DFe, as well as DMn and DCu, into the HSSW whereas lateral transport from land formed a source of DMn and DFe. One station in the Ross Sea Polynya was resampled after two weeks, during which time the thickness of the BNL increased, with accompanying increases in DFe and DMn near the seafloor. In the surface layer nutrients (including micro-nutrients) were depleted further. The uptake slopes/stoichiometric ratios of DZn, DCd and DCo versus phosphate indicated that the distribution of these metals is related to uptake as well as the composition of the phytoplankton community. Estimated stoichiometric ratios of Zn and Cd relative to P were higher at a station dominated by Phaeocystis antarctica than at diatom-dominated stations, implying a higher utilization of these metals by P. antarctica.

The pronounced seasonal variation over the Bay of Bengal affects trace metals concentration and distribution. Trace metals distribution in the Bay of Bengal has been best characterized during spring and fall intermonsoon, while limited studies were conducted during the southwest monsoon. This study reports the full-depth profiles of trace metals, including dissolved iron, manganese, lead, cadmium, copper, and zinc (Fe, Mn, Pb, Cd, Cu, and Zn) in the Bay of Bengal (BoB) during southwest monsoon, from July to August 2013. At coastal and ocean scales, transect observations covering the entire water depth provided a comprehensive picture of the circulation and biogeochemical cycles of these elements in seawater during the southwest monsoon. Water samples were obtained from one station in the northeastern Indian Ocean (NR-1) and from three shallow coastal stations with maximum depths <60 m (BA-1, BA-3, and BA-5), as well as from three offshore stations with maximum depths exceeding 2000 m (MY-7, MY-9, and MY-11). In the surface layer (5 m depth), the trace metal concentrations at the shallow near-coastal station BA-5 were higher than those at the ocean station NR-1. Surface trace metal concentrations in offshore regions encompassing stations MY-11, MY-9, and MY-7 were relatively higher than those reported for other seasons in a similar salinity region, indicating seasonal variation associated with freshwater intrusion and coastal-derived input. Below the mixed layer depth, the trace metal/phosphate (P) ratio was higher than that previously reported in the eastern Indian Ocean, suggesting an input from continental margins and mildly reducing sediments, particularly for Fe, Mn, and Cu. Moreover, at intermediate depths (190–800 m), where the North Indian Central Water (NICW) is the main water mass, the Cd/P ratio (0.55 ± 0.11 nmol/μmol) deviated from the global trend (∼0.3 nmol/μmol) owing to oxygen-deficient conditions. Intriguingly, at some stations, specifically MY-9 and MY-7, the intermediate dFe concentrations were relatively higher than those at station NR-1 at the same depth. Continental margin sediment, water mass movement, and ventilation may control the transport of Fe from locations with high Fe concentrations, including near the continental shelf (station MY-11 in this study) and the Andaman Sea. • Monsoon dynamics drive seasonal trace metal variations. • Continental margins act as significant dFe sources. • NICW exhibits elevated dFe levels from various sources. • Continuous sediment inputs influence dCu distribution. • Oxygen-deficient conditions affect dCd-phosphate relationship. [ABSTRACT FROM AUTHOR]

Multiple factors such as temperature, human activity, climate and hydrochemistry conditions affect water quality of drinking water sources. This research mainly focused on monitoring the dissolved trace metal concentrations from water samples in several important drinking water sources including the Huangpu River, Qingcaosha Reservoir and several reservoirs for West Tai Lake from spring to summer in 2013. The changes of trace metal concentrations and removal efficiencies in four typical water treatment plants (WTPs) in China corresponding to these water sources were also investigated. Results indicated that Qingcaosha Reservoir, Hengshan Reservoir and Youche Reservoir were less influenced by anthropogenic activities, therefore the change of dissolved metal concentrations was not significant except for local geochemical elements such as Sr and Ba. The other two water sources that flow through large industrial areas were greatly affected with elevated trace metal concentrations such as Fe, Mn, Zn, Ni, P, which can be attributed to anthropogenic and socio-economic impacts. High Fe and Mn concentrations were observed at low pH while high electric conductivity gained relevance with high geochemical metal concentrations. The occurrence of high dissolved Ni, Cu, Co and Zn was associated with high ammonia concentration and low pH, which might result from the formation of metal ammine complexes. In addition to the raw water information, dissolved metal concentrations after the treatment by individual WTP processes indicated that biological activated carbon and sand filtration achieved significant removal of Mn and Fe, while coagulation/flocculation efficiently reduced the concentrations of As, Pb and Zn. However, oxidation processes might form highly toxic Cr(VI) and increase the dissolved Cr concentrations which posed a potential threat to human safety. These preliminary results showed the necessity of control technology for dissolved trace metals in micro-polluted water sources for providing safe water. [ABSTRACT FROM AUTHOR]

Certification of trace metals in seawater certified reference materials (CRMs) NASS-7 and CASS-6 is described. At the National Research Council Canada (NRC), column separation was performed to remove the seawater matrix prior to the determination of Cd, Cr, Cu, Fe, Pb, Mn, Mo, Ni, U, V, and Zn, whereas As was directly measured in 10-fold diluted seawater samples, and B was directly measured in 200-fold diluted seawater samples. High-resolution inductively coupled plasma mass spectrometry (HR-ICPMS) was used for elemental analyses, with double isotope dilution for the accurate determination of B, Cd, Cr, Cu, Fe, Pb, Mo, Ni, U, and Zn in seawater NASS-7 and CASS-6, and standard addition calibration for As, Co, Mn, and V. In addition, all analytes were measured using standard addition calibration with triple quadrupole (QQQ)-ICPMS to provide a second set of data at NRC. Expert laboratories worldwide were invited to contribute data to the certification of trace metals in NASS-7 and CASS-6. Various analytical methods were employed by participants including column separation, co-precipitation, and simple dilution coupled to ICPMS detection or flow injection analysis coupled to chemiluminescence detection, with use of double isotope dilution calibration, matrix matching external calibration, and standard addition calibration. Results presented in this study show that majority of laboratories have demonstrated their measurement capabilities for the accurate determination of trace metals in seawater. As a result of this comparison, certified/reference values and associated uncertainties were assigned for 14 elements in seawater CRMs NASS-7 and CASS-6, suitable for the validation of methods used for seawater analysis. [ABSTRACT FROM AUTHOR]

ABSTRACT S.B. Sujitha; M.P. Jonathan; D.C. Escobedo-Urias; Fernando Aguirre-Bahena; S.K. Sarkar; Lorena Elizabeth Campos Villegas, and E. González Gomez., 2018. Fate of dissolved trace metals in the waters of Bahia Magdalena lagoon, Baja California Sur, Mexico. In: Shim, J.-S.; Chun, I., and Lim, H.S. (eds.), Proceedings from the International Coastal Symposium (ICS) 2018 (Busan, Republic of Korea). Journal of Coastal Research, Special Issue No. 85, pp. 431–435. Coconut Creek (Florida), ISSN 0749-0208. Concentrations of dissolved trace metals (Fe, Mn, Cr, Cu, Ni, Co, Zn, Cd, As) were determined in forty-one surface and forty bottom water samples procured from Bahia Magdalena lagoon, Baja California Sur, Mexico using an Atomic Absorption Spectrophotometry. In-situ measurements of temperature, salinity, dissolved oxygen and pH were also carried out in each station and high salinities classified the lagoon as Eurihaline. The region witness raised temperatures (avg. 28.92°C) due to their location in an arid setting with less precipitation (< 14mm) and high evaporation rates. The pH values ranged from 7.52 – 8.56 indicating an alkaline environment. Cadmium and Zinc presented nutrient like distributions whereas Fe, Mn, Co, Cu, Cr, Ni showed scavenged type of profiles. The high values of Ni (surface: 0.246 mg/L; bottom: 0.138 mg/L), As (surface: 0.224 mg/L; bottom: 0.228 mg/L), Co (surface: 0.125 mg/L; bottom: 0.122 mg/L) and Cd (surface: 0.018 mg/L; bottom: 0.016 mg/L) are due to the local influences such as the ophiolitic outcrops, upwelling process, hydrothermal fluids and submarine phosphatic deposits. Less concentrations of Fe in the surface 0.011 mg/L and bottom waters (0.007 mg/L) are attributed to the formation of insoluble Fe oxides and hydroxides in oxygenated waters. Moreover, the fate of metals is also determined by the plankton distributions present in the lagoon which release strong chelators that influence the bioavailability of trace metals. However, the levels of Ni and As were observed to be hundred fold higher than the recommended values (Ni: 0.002 mg/L, As: 0.0002 mg/L) set by the Mexican government posing severe threat to the biota. This study gives distinct evidence of the distribution of dissolved trace metals against which long term contamination status may be evaluated. [ABSTRACT FROM AUTHOR]

Using land use types in multiple spatial scales (entire basin, buffer zones, and slopes) as well as statistical and spatial analysis, relationships between land use types and concentrations of dissolved trace metals were determined in the Le'an River Basin, China. The result showed that farmland and urban land were determined as the source of the pollutants, while forestland and grassland were identified as the sink of the pollutants. The temporal differences of relationships between land use types and concentrations of dissolved trace metals mainly due to the discrepancy of rainfall characteristics. Land use type close to river was a better indicator for the effectiveness of concentrations of trace metals, especially at scale of 0-200 m. Forestland and grassland on lower slopes greatly affected the water quality, and the former had no significant or weak influences on higher slopes. Urban land had the greater positive correlations with concentrations of dissolved trace metals on higher slopes, which are mainly due to frequent mining activity. Further analysis suggested that the buffer zones with low slope needed to be seriously taken into consideration for effective land use management in similar basin. [ABSTRACT FROM AUTHOR]

Water samples were collected on the Athabasca River (AR), upstream and downstream from bitumen mines and upgrading facilities, to identify changes in water quality due to industrial activities in this region of northern Alberta, Canada. Starting upstream of Fort McMurray and proceeding downstream ca. 100 km, waters were collected in duplicate at 13 locations on the main stem of the river, as well as 5 tributary streams, using ultraclean sampling protocols developed for polar snow and ice. To estimate potential bioaccessibility, trace elements of concern (Ag, Cd, Pb, Sb, Tl) were determined in the dissolved fraction (< 0.45 μm) along with metals known for their enrichments in bitumen (V, Ni, Mo, Re) and those found mainly in ionic (Li, Sr) or colloidal forms (Al, Co, Cr, Fe, Ga, Mn, Th, Y). Analyses were performed in the metal-free, ultraclean SWAMP lab using quadrupole and sector-field ICP-MS. Concentrations of Ag, Cd, Pb, Sb and Tl were extremely low, not significantly more abundant downstream of industry and probably reflect “background” values. In contrast, V, Ni, Mo and Re concentrations were all significantly (p < 0.05) greater downstream of industry. However, chloride also increased downstream, due to natural inputs of saline groundwaters and it is unclear whether the increases in V, Ni, Mo and Re are due to natural or anthropogenic inputs to the river. Although it had been claimed that the industrial development of the Athabasca Bituminous Sands (ABS) is a significant source of Ag, Cd, Pb, Sb and Tl to the river, our study failed to find any evidence to support this. Here we provide a first, robust (accurate and precise) description of baseline values for these trace elements in the AR, and suggest that V, Ni, Mo and Re are more valuable tracers for environmental monitoring and source assessment. [ABSTRACT FROM AUTHOR]

The distribution of trace metal micronutrients, which are crucial in many biotic enzymatic reactions, in the eastern Indian Ocean is not well understood. Here, we measured the concentrations of dissolved iron (dFe), manganese (dMn), lead (dPb), cadmium (dCd), copper (dCu), and zinc (dZn) at full depth in the water column of the eastern Indian Ocean (from the Bay of Bengal to the south of the equator). Throughout, dFe was replete in the surface mixed layer (SML). Moreover, the supply of dFe from below the SML and atmospheric deposition met the phytoplankton demand. In the thermocline, the subsurface maxima of dFe coincided with the dissolved oxygen (DO) minima. In addition, the distribution of Fe* in the Bay of Bengal indicated an additional input of dFe into the water column, apart from the biogenic organic particle regeneration. Unlike dFe, other trace metals were not enriched in the oxygen minimum zone, indicating that high Fe* value was caused by the release of dFe from the estuary or continental shelf under oxic conditions. In deep water, dFe, dMn, and dPb levels were low, whereas dCd, dCu, and dZn concentrations increased with depth. However, dFe and dMn levels were elevated in coastal bottom waters, where Fe* values were also high, indicating the supply of these metals from external sources. Exploring the relationship between trace metals and phosphate at the thermocline illustrated how oxygen-deficient conditions in the Bay of Bengal affect trace metal (dCd in particular) and phosphate ratios, compared with the global trend. • Supply of dFe into the surface waters of eastern Indian Ocean met the phytoplankton demand. • Continental shelf and bottom sediment enriched dFe and dMn concentration in thermocline and near bottom waters. • Relationship between dCd and phosphate alter from the global trend. • DPb in Bay of Bengal showed the highest concentration among the previous reports. [ABSTRACT FROM AUTHOR]

Trace metals play an important role in some biogeochemical processes in the marine system. The physical and hydrological conditions in estuaries and coastal seawater are complicated and significantly affected by human activities. Therefore, the biogeochemical behavior and influencing mechanism of trace metals in nearshore water have become a research hotspot. Jiulong River estuary and Xiamen Bay are located in the coastal areas of Fujian Province, which are significantly influenced by Longyan, Xiamen, and Zhangzhou City. In July 2021, November 2021, and January 2022, the trace metals chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), and cadmium (Cd) and environmental factors (water temperature, salinity, pH, dissolved oxygen (DO), suspended particulate matter (SPM), etc.) in Jiulong River estuary and Xiamen Bay were investigated. The results showed that the order of trace metal concentration average values measured in Jiulong River estuary and Xiamen Bay was Mn>Ni>Cu>Cr>Co>Cd. In July 2021, the average values of ρ (Cr), ρ (Mn), ρ (Co), ρ (Ni), ρ (Cu), and ρ (Cd) were 0.159, 47.96, 0.068, 1.56, 1.07, and 0.016 μg·L -1 , respectively. In November 2021, the average values were 0.216, 8.48, 0.030, 1.70, 1.92, and 0.019 μg·L -1 , respectively. The average concentrations in January 2022 were 0.281, 32.39, 0.062, 2.21, 1.54, and 0.034 μg·L -1 , respectively. The concentration of dissolved metals in the estuary was higher than that in the bay area. Principal component analysis showed that the main factors affecting the concentrations of dissolved trace metals were river runoff and anthropogenic activities.

Abstract: This study for the first time examined dissolved metals (Cu, Cd, and Mn) together with dissolved oxygen and carbonate system in the whole Pearl River Estuary system, from the upper rivers to the groundwater discharges until the estuarine zone, and explored their potential impacts in the adjacent northern South China Sea (SCS) during May–August 2009. This river-groundwater-estuary system was generally characterized by low dissolved metal levels as a whole, whilst subject to severe perturbations locally. In particular, higher dissolved Cu and Cd occurred in the North River (as high as 60nmol/L of Cu and 0.99nmol/L of Cd), as a result of an anthropogenic source from mining activities there. Dissolved Cu levels were elevated in the upper estuary near the city of Guangzhou (Cu: ∼40nmol/L), which could be attributable to sewage and industrial effluent discharges there. Elevated dissolved metal levels (Cu: ∼20–40nmol/L; Cd: ∼0.2–0.8nmol/L) also occurred in the groundwaters and parts of the middle and lower estuaries, which could be attributable to a series of geochemical reactions, e.g., chloride-induced desorption from the suspended sediments, oxidation of metal sulfides, and the partial dissolution of minerals. The high river discharge during our sampling period (May–August 2009) significantly diluted anthropogenic signals in the estuarine mixing zone. Of particular note was the high river discharge (which may reach 18.5 times as high as in the dry season) that transported anthropogenic signals (as indicated by dissolved Cu and Cd) into the adjacent shelf waters of the northern SCS, and might have led to the usually high phytoplankton productivity there (chlorophyll-a value >10μg/L). [Copyright &y& Elsevier]

The study on medium size river Sutla in Croatia indicated considerable water contamination at specific sites during the baseflow period, probably associated to low flow-rate (0.73-68.8 m s), and consequently low dilution capacity of this river. Various aspects of contamination were observed: increased conductivity to 1,000 μS cm, decreased dissolved oxygen level to 50%, 4-5°C increased water temperature, increased concentrations of several dissolved trace elements (e.g., maximal values of Li: 45.4 μg l; Rb: 10.4 μg l; Mo: 20.1 μg l; Cd: 0.31 μg l; Sn: 30.2 μg l; Sb: 11.8 μg l; Pb: 1.18 μg l; Ti: 1.03 μg l; Mn: 261.1 μg l; and Fe: 80.5 μg l) and macro elements (e.g., maximal values of Na: 107.5 mg l; and K: 17.3 mg l), as well as moderate or even critical fecal ( E. coli: 4,888 MPN/100 ml; total coliforms: 45,307 MPN/100 ml; enterococci: 1,303 MPN/100 ml) and organic pollution (heterotrophic bacteria: 94,000 cfu/ml). Although metal concentrations still have not exceeded the limits considered as hazardous for aquatic life or eventually for human health, the observed prominent increases of both metal concentrations and bacterial counts in the river water should be considered as a warning and incentive to protect the small and medium size rivers from the future deterioration, as recommended by EU Water Framework Directive. [ABSTRACT FROM AUTHOR]

The study is based on physicochemical parameters (pH, DO, and salinity) and dissolved trace elements (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, and Cd) of Uppanar River water (RW) and surface and bottom coastal waters (CW) off Cuddalore, southeast coast of India in 56 samples collected during 2001. High concentration of Fe and Mn in RW and CW indicates enrichment above the normal level. Physicochemical parameters do not exhibit significant relationship with trace metals. Enrichment of Pb is due to external input and excess level of Cu, Pb, Zn in RW and Cr, Cu, Ni, Pb in CW is identified. Fe-Mn oxides are the chief scavengers of trace elements in both the aquatic environments and it is supported by geochemical, statistical and comparative studies. The results signify that industrial growth has affected the aquatic environments and regular monitoring will help to adopt stringent pollution control measures for better management of the aquatic region. [ABSTRACT FROM AUTHOR]

Concentrations of dissolved metals (Cd, Cu, Ni, Mn and Zn) were determined for summer and winter, under low-flow conditions in Port Jackson, a microtidal, well-mixed estuary in south-east Australia. Mean concentrations of Cd (0.04 ± 0.02 μg/l), Ni (0.86 ± 0.40 μg/l), Mn (20.0 ± 25 μg/l) and Zn (6.47 ± 2.0 μg/l) were below water quality guidelines. Concentrations of Cu (1.68 ± 0.37 μg/l), however, slightly exceeded recommended values. Dissolved Ni and Mn behaved mostly conservatively, whereas Cd, Cu and Zn showed mid-estuarine maxima. Peaks in Cd, Cu and Zn concentrations were located in the upper estuary, independent of the salinity and suspended particulate matter loading, and were consistent with anthropogenic inputs of metals in the estuary. Concentrations of dissolved Cu were highest in summer, whereas concentrations of Cd, Ni and Mn were significantly lower in summer than winter (P&les;0.05). The increase in temperature and biological activity during summer explained the seasonal variation. The sequence of log Kd values (20–30 salinity) was Mn>Zn>Cu>Ni. These results give unique information concerning the contemporaneous distribution of dissolved trace metals in the Port Jackson estuary and they provide a data set against which the long-term contamination may be assessed. [Copyright &y& Elsevier]

This study investigates the origins and transport mechanism of dissolved trace metals (d-Mn, d-Fe, d-Cu, and d-Co) and macronutrients in Ariake Sea, a shallow and semi-enclosed inlet bay during early summer. Concentrations of macronutrients and dissolved trace metals (d-Mn, d-Fe, d-Cu, and d-Co) were the highest in the surface waters of the innermost station in Ariake Sea and decreased gradually from the nearshore regions to the East China Sea. During estuarine mixing, d-Fe, d-Mn, and d-Cu showed non-conservative patterns, while d-Co exhibited a conservative pattern. This variability reflects the combined effects of water circulation and geochemically driven cycles in shaping the distribution of the metals. D-Mn and d-Fe were removed during estuarine mixing. Meanwhile, d-Cu pattern indicated input via intra-estuarine processes. The internal flux of d-Cu (1.6 × 1013 nmol/month) calculated from our data was slightly higher than its river fluxes (1.1 × 1013 nmol/month). We proposed sedimentary fluxes (2.1 × 1011–1.8 × 1013 nmol/month) supplied more d-Cu than other possible sources such as photodissolution of SPM, groundwater discharge, and atmospheric deposition. The conservative pattern of d-Co reflected a balance between input and removal during estuarine mixing. • Fluvial input is a primary source of dissolved trace metals (manganese, iron, copper and cobalt) in Ariake Sea. • The binding with organic ligand hinders loss of cobalt via scavenging processes. • Internal input within the embayment system enriches dissolved copper in the water column. [ABSTRACT FROM AUTHOR]