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The editorial in "Frontiers in Marine Science" discusses the development and novel applications of geochemical proxies in marine and terrestrial carbonate records. The research explores various proxies, such as Mg/Ca and Li/Ca cycles in coralline algae and δ18Oshell in bivalves, to understand past climate conditions. Laboratory and field studies are conducted to develop new proxies, and existing proxies are applied to samples from the distant past, providing insights into historical climate variations. The editorial aims to inspire innovative research in the field of paleoclimatology and geochemistry. [Extracted from the article]

The Mediterranean Basin is involved in a recurring phenomenon wherein air masses laden with dust from North Africa impact the southern regions of the European continent. Saharan dust has been associated with increased mortality and respiratory symptoms. Palermo is a large coastal city, and in addition to the impact of desert dust particles, it has a mixture of anthropogenic sources of pollutants. In this study, we collected Saharan dust samples during August 2022 and October 2023, following a high-intensity Saharan dust event, and measured concentrations of 33 major and trace elements as well as Rare Earth Elements (REE). The mineralogical characterization of the deposition dust collected during Saharan events revealed calcite, dolomite, quartz, and clay minerals. The presence of palygorskite is indicative of Saharan events. Seven elements (Ca, Mg, Al, Ti, Fe, K, and Na) account for 98% of the total analyzed inorganic burden. Elemental ratios are valuable tools in atmospheric sciences for estimating sources of air masses. The results highlight that the city of Palermo is mainly affected by dust from the north-western Sahara. [ABSTRACT FROM AUTHOR]

To investigate the relationship between the correlation ratios of selenium (Se) and other elements and mild cognitive impairment (MCI) among older adults. A total of 1000 individuals participated in our research analysis. The concentrations of elements in whole blood were determined using inductively coupled plasma mass spectrometry to reflect their exposure levels. Participants' cognitive function was assessed using the Mini-Mental State Examination. Logistic regression analysis was used to evaluate the relationship between elemental ratios and MCI. Se concentration was positively correlated with red blood cell count (r = 0.219, p < 0.001), haemoglobin level (r = 0.355, p < 0.001), haematocrit (r = 0.215, p < 0.001), mean corpuscular haemoglobin (r = 0.294, p < 0.001) and mean corpuscular haemoglobin concentration (r = 0.428, p < 0.001) and negatively correlated with red cell volume distribution width-standard deviation (r = –0.232, p < 0.001) and platelet distribution width (r = –0.382, p < 0.001). Compared with the normal group, the ratios of Se/vanadium (V), Se/lead (Pb) and Se/cadmium (Cd) in the whole blood of the MCI group were significantly lower (all p < 0.001), while the ratios of manganese (Mn)/Se and iron (Fe)/Se were higher (all p < 0.001). The increase in the ratios of Se/V, Se/Pb and Se/Cd is related to a decreased risk of MCI among older adults; contrarily, an increase in the ratios of Mn/Se and Fe/Se may be a risk factor for MCI. [ABSTRACT FROM AUTHOR]

The brown macroalga Fucus vesiculosus is a foundation species in temperate rocky shores, subjected to seasonally fluctuating environmental conditions. To obtain a more complete picture of the seasonality of F. vesiculosus ecophysiology in the northern Baltic Sea, in situ photochemistry, elemental ratios and chlorophyll a and c content of the alga were investigated in field campaigns conducted in different months throughout the year during 2017. Carbon, nitrogen, carbon to nitrogen ratio and chlorophyll a and c content of the alga varied substantially throughout the year, with highest carbon content observed in summer, and highest nitrogen content in winter. C:N ratio in F. vesiculosus apical tissue ranged from 8.6 in February to 48.3 in July. Chlorophyll a and c content followed inversely the seasonal patterns of ambient irradiance. High chlorophyll a and c content in winter was associated with higher maximum photosynthetic efficiency of energy conversion (Fv/Fm), but not with efficiency of photosynthetic energy conversion under light limitation (α). Electron transport rate correlated strongly with seawater temperature, and the highest electron transport rates were observed in summer and correlated with highest internal carbon content of the alga. Redundancy analysis conducted on measured environmental variables against physiological responses identified day of year, temperature and macronutrients in seawater as the most important variables driving the observed seasonal patterns in F. vesiculosus ecophysiology. The results suggest elevated temperatures may increase Fucus growth and photosynthesis rates in the study area. Highlights Two distinct physiological states of Fucus vesiculosus were identified. The most important variables driving responses were season, temperature and macronutrients. Fucus ecophysiology shows substantial seasonality in the northern Baltic Sea. [ABSTRACT FROM AUTHOR]

Elucidating the tectonic setting of unknown rock samples has long attracted the interest of not only igneous petrologists but also a wide range of geoscientists. Recently, attempts have been made to use machine learning to discriminate the tectonic setting of igneous rocks. However, few studies have designed methods that are applicable to altered rocks. This study proposes a novel approach that utilizes the ratio of elements less susceptible to weathering, alteration, and metamorphism as feature values for analyzing altered basalts. The method was evaluated using six well-established machine learning algorithms: K-Nearest Neighbor (KNN), Support Vector Machine (SVM), Random Forest (RF), Light Gradient Boosting Machine (LightGBM), eXtreme Gradient Boosting (XGBoost), and Multi-Layer Perceptron (MLP). The results show that KNN achieved the highest classification score of 83.9% in the balanced accuracy of classifying the eight tectonic settings, closely followed by SVM with a score of 83.7%. In addition, oceanic and arc/continental basalts could also be discriminated against with an accuracy of more than ∼90% for KNN. This study suggested that the machine learning method can discriminate tectonic settings more accurately and reliably than previously used discrimination diagrams by designing appropriate feature values.

Previously unidentified small (up to 1.3 mm in length), gently curved hollow spines composed of calcium phosphate and derived from the upper Famennian (Devonian) of the Holy Cross Mountains in central Poland are described. They are similar to the type species of Phakelodus, but show some distinct morphological differences, therefore, have been included into Phakeloides polonicus gen. et sp. nov. The studied specimens of that species show relatively massive mineral structure characterized by significant porosity with well-preserved major structural features. The outer layer of the spines is, in contrary, fragmentarily preserved, and exposes distinct mosaic-like ornamentation of the surface of the middle layer, which consists of obliquely arranged, shallow furrows. Geochemical analyses of the Devonian Phakeloides polonicus gen. et sp. nov. spines have revealed the presence of a weaker mineralized structure, compared to conodont apatite, composed of a diagenetic phosphate phase. It is characterized by moderate cathodoluminescence intensity, elevated concentrations of iron and sulphur as well as decreased concentrations of strontium, calcium, and phosphorus. The "Orsten" type, early diagenetic phosphatization of the outer layer of the spines is not observed in studied specimens of Phakeloides polonicus gen. et sp. nov., contrary to the previously investigated Furongian (Cambrian) material. This points to the low rate of diagenetic phosphatization, which was likely enabled by very slow sedimentation and long residence time of the spines close to sediment-water interface at varying redox conditions and significant flux of phosphate ions. [ABSTRACT FROM AUTHOR]

Macroalgae are important primary producers in coastal waters; they have high carbon sink potential and are often subjected to hyposaline stress in their natural habitats. The effect of hyposaline stress on dissolved organic carbon (DOC) release from macroalgae remains to be studied in depth. In this study, five common intertidal macroalgae in coastal waters of Fujian Province, China—Pyropia haitaneisis, Gracilaria lemaneiformis, Sargassum thunbergii, Enteromorpha prolifera, and Ulva lactuca—were used as research materials to investigate the effects of 6-h hyposaline treatments (5 PSU, 0 PSU) on the growth, DOC release rate, photosynthesis, respiration, and contents of carbon (C), nitrogen (N), and phosphorus (P). Our results showed that, although there were significant interspecific differences in the tolerance of the five species of macroalgae to low salinity, the DOC release rate of macroalgae increased overall with decreasing salinity, while the photosynthetic rate showed the opposite trend. Hyposaline treatments reduced the net photosynthetic rate of macroalgae, as the net photosynthetic rate of all five species decreased by more than 50% and 75% under the 5 PSU and 0 PSU treatments, respectively. The tissue C contents of P. haitaneisis, G. lemaneiformis, and E. prolifera increased significantly with decreasing salinity, by 6.90%, 40.15%, and 43.80% at 0 PSU, respectively. However, the tissue C contents of S. thunbergii and U. lactuca were not influenced or were slightly decreased by low salinity. These results suggest that short-term hyposaline treatment has a dual effect on organic carbon accumulation of macroalgae by inhibiting photosynthetic carbon fixation and increasing DOC release, and this in turn may have a large impact on the carbon cycle in macroalgae enrichment areas.

Rivers and estuaries are important conduits and reactors for organic matter (OM). Despite the substantial export of terrestrial OM by rivers, only a small proportion of this material reaches the open ocean. One potentially important mechanism contributing to the removal of terrestrial dissolved OM (DOM) is flocculation; a process that transforms DOM into larger size fractions that can settle into sediment pools. Here we investigate the role of flocculation in adjacent boreal coastal systems over three consecutive seasons. Flocculation experiments, which include the artificial salting of freshwater DOM to mid (12 psu) and high salinity (25 psu), and a 1:1 mixture of freshwater DOM with their respective saline endmember, highlight a potentially important source of particulate carbon (PC) in boreal estuaries. Along with a 3.5% ± 1.0% removal of dissolved organic carbon (DOC) and 44% ± 16% dissolved iron (DFe), the potential for flocculation of these constituents significantly increased with increasing salinity from 12 to 25 psu. The particulate matter (PM) produced by salt‐induced flocculation was comparable to in situ PC concentrations (in situ PC = 27.5 μmol L−1 and flocculated PC = 15.0 μmol L−1) and stable carbon isotopic signatures (in situ PM = −28.8‰ and flocculated PM = −28.3‰). DFe:DOC and Sr were the only parameters that could significantly explain the degree of carbon and iron flocculation. This demonstrates the importance of DOC, DFe, and optical properties, and the predictive value of DFe:DOC for understanding DOM susceptibility to flocculation and its relevance and contribution to regional and global carbon budgets. Plain Language Summary: The salt in seawater is an important factor shaping the transport, transformation, and fate of organic matter (OM) from rivers to the ocean. Salts can cause compounds to stick together and form larger particles in a process called flocculation. These larger particles can sink to the bottom where they can be effectively stored in sediments; however, understanding the factors behind how much and where flocculation may occur is still unresolved. Bridging these knowledge gaps will contribute to improved landscape and regional carbon budgets. We investigated the impact of flocculation in two boreal coastal systems using a series of laboratory experiments across multiple seasons. Our findings highlight the important contribution of flocculation in removing OM from the water column. Flocculation can occur across the entire range of estuarine salinities while the degree to which it contributes to particulate OM at a given salinity is dependent upon dissolved OM quantity, source, and composition. We further show flocculation to be a selective process, whereby the concentration of iron and organic carbon, as well as their ratio, can be a useful tool to predict the degree of flocculation at regional scales. Key Points: Flocculation affects dissolved and particulate organic matter and iron distribution and characteristics; thus is a requisite for carbon flux estimatesDissolved organic carbon, dissolved iron, and their molar ratio are useful predictors of the spatial and temporal variations in flocculationSalt‐induced flocculation can occur in salinities up to 25 psu [ABSTRACT FROM AUTHOR]

• Geochemical concentrations and distribution of major and trace elemental oxides were governed by lithologic factors. • Silicon, Fe, Al, Ca, and K showed the higher affinity to parent material. • The profiles elemental ratios revealed both an oxic and anoxic depositional environment. • Volatility of elements depends on the modes of occurrence, the intensity of the fire and the duration. Geochemical composition and distribution of major elements study is vital in terms of investigating the major soil forming compounds and to know the fate of trace elements in soils. Particle size distribution (PSD), pH, organic carbon (OC), and major and trace elements of hydromorphic soils formed on recent alluvium in Obafemi-Owode Local Government Area of Ogun state, Nigeria were analysed using standard procedures. Three profiles pits were dug based on the mapping units identified, and samples were collected for laboratory analysis. Data were subjected descriptive statistics and Pearson' correlation coefficients using IBM SPSS version 27. The PSD was dominated by sand content, followed by clay and silt, and soil pH in KCl was strongly acid (3.17–4.30) and pH in H 2 O was moderately acid (4.74–5.80), while OC contents were low to moderate (1.22–6.69 g/kg). The major elemental results showed higher concentration of SiO 2 (>50 %) connotes presence quartz, feldspar, and clay minerals. Manganese, Cu, Ba, Zr, and Zn have higher concentrations among the trace elements. Major elements ratios (SiO 2 /Al 2 O 3, K 2 O/Al 2 O 3) showed moderate weathering stage, while trace elements ratios (Ni/Co and Cu/Zn) revealed deposition under humid conditions and anoxic environment. The statistical analysis revealed that most elements have skewness closed to zero except MgO and K 2 O. Correlation coefficients between the elements are positive and significant (p < 0.05 and p < 0.01) indicating that their presence can be accounted for by similar lithology, though some have negative relationship which could be as a result of anthropogenic activities. The study found that elements were potential tracers for the presence of human activities and environmental changes. [ABSTRACT FROM AUTHOR]

To investigate the chemical compositions, sources, and aging processes of submicron particles (PM1), a comprehensive field campaign was conducted in Guangzhou urban area of China during the autumn (October–November) of 2018. The average mass concentration of PM1 was 35.6 ± 20.8 µg m−3, which was mainly contributed by organic aerosols (OA, 42%), then followed by sulfate (25%) and inorganic nitrate (11%). The inorganic nitrate was found to be the main driving component (up to ∼50%) to account for the fast increase of PM1 during the polluted periods of Guangzhou autumn. The promotion effects of sulfate, aerosol liquid water content, and particles acidity on nitrate formation were systematically discussed. Source apportionment results showed 72% of OA in Guangzhou autumn was contributed by secondary OA (SOA), and 28% of primary OA (POA), including vehicle emission related hydrocarbon‐like OA (HOA, 16%), nitrogen‐containing OA (NOA, 3%) and cooking OA (COA, 8%). To explore the aging processes of OA, the dynamic variations of OA and its oxidation level as a function of ambient photochemical age are shown. Using an in situ field‐deployed oxidation flow reactor, the heterogeneous reaction rate coefficients of ambient POA with OH radicals (kOH) were estimated to be 4.0–5.4 × 10−13 cm3 molecules−1 s−1, which is equivalent to a lifetime of POA >2 weeks. The long heterogeneous lifetime of POA supports gas phase oxidation was the major pathway for ambient OA aging. The OH uptake coefficient (γOH) was estimated to be 0.76–0.84, underlining that OH radicals can be taken up efficiently on ambient aerosols. Key Points: The promotion effects among aerosol liquid water contents, aerosol acidity, sulfate and nitrate formation in the haze periods were foundFreshly formed secondary organic aerosols (SV‐OOA) contributed substantially to OA/ΔCO enhancement during aging processesLong heterogeneous lifetime of ambient OA (>2 weeks) was found based on an in situ field‐deployed oxidation flow reactor [ABSTRACT FROM AUTHOR]

This study introduces and discusses inorganic geochemical data from Patos Lagoon, the world's largest choked coastal lagoon located in southern Brazil. Here, we characterise the sedimentary geochemical environment using different elemental ratios to assess the influence of both anthropogenic activities and the natural hydrological regime on the contemporary geochemical record. Three sediment cores collected in the freshwater domain of Patos Lagoon were analysed. Elements Al, Ca, Cr, Fe, K, Sr, Ti and V were determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Strong correlations between Sr and Ca, together with the lack of correlation with detrital elements suggested that carbonate precipitation is particularly important in this system. Lithogenic elements Al, K, Fe and Ti reflected the influence of the Guaíba River on the sedimentary sequences of Patos Lagoon. The K/Al ratio was used to investigate changes in weathering patterns and Ti/Al to evaluate grain size changes. Ti/Ca provided an excellent proxy for inferring historical changes in wetter and drier conditions, and also appears to be sensitive to the influence of ENSO events. Finally, the V/Cr ratio reflected the prevailing reducing conditions of the bottom sediments. Overall, our findings show that processes of sediment weathering, transport and deposition are mostly related to natural process, and given the large size of the system, the dilution processes could play an important role in attenuating geochemical changes related to human impacts. [ABSTRACT FROM AUTHOR]

Peatlands occupy 20% of the land area of Ireland and store over half of soil carbon stocks. Over 80% of these peatlands have been disturbed by human activity such as drainage for peat extraction, afforestation and agriculture. In this study, peat samples were collected from 12 horticultural peat extraction sites in the Irish midlands. The carbon (C), nitrogen (N), hydrogen and sulphur content were determined, and from these, the carbon oxidation state (Cox) and oxidative ratio (OR) were calculated. The carbon oxidation ratio reflects organic matter synthesis and degradation, and is thus an important parameter in understanding terrestrial carbon cycling, whilst OR represents the molar ratio of oxygen (O2) and carbon dioxide (CO2) fluxes associated with net ecosystem exchange. Elemental concentrations and ratios were typical for Irish horticultural peat (e.g. carbon concentrations 54%–57%), though showed site to site variability. Cox and OR values varied between −0.22 and −0.11, and 1.04 and 1.07, respectively, and were comparable to United Kingdom peat soils. All values for OR were lower than 1.1, the value commonly used in global CO2 partitioning studies. Further research should investigate OR values in peatland which has not been studied to date. Across all sites, measures of increased decomposition (i.e. C/N ratios) significantly correlated with increasing OR reflecting more reduced organic matter. This study provides data in temperate peat soils that increases the coverage of Cox and OR values and will inform global CO2 partitioning studies. [ABSTRACT FROM AUTHOR]

Microscope, cathodoluminescence, chemical and oxygen isotope studies have been conducted to determine the original mineralogy and diagenetic alteration of phosphatic grasping spines of Cambrian chaetognaths. The obtained data, along with a comparison to the composition of conodont apatite, show the presence of a few generations of diagenetic phosphate phases. A thin, outer layer of the spines is composed of very early diagenetic phosphate, which incrusted the original cuticle layer contributing to the preservation of an original shape and structural details of the fossils. This process can be linked to the 'Orsten'‐type phosphatization mainly known from Lower Palaeozoic strata. Successive phosphate generations are observed within the middle and inner layers as well as internal cavities of the spines. Plastic deformations and diagenetic features of the spines show that they were originally composed of slightly flexible chitinous organic matter similar to that of modern chaetognaths. This conclusion is substantiated by rare findings of purely organic remnants of Cambrian chaetognath grasping spines. [ABSTRACT FROM AUTHOR]

Loess-based proxies have been widely used to infer glacial-interglacial to millennial-scale changes of the East Asian monsoon. However, the characteristic of millennial-scale variability is still unclear during glacial-interglacial cycles in loess-palaeosol sequence. Here, we present high-resolution (5-cm) elemental results of a 96.7-m thick Mangshan loess-palaeosol sequence on the southeastern Chinese Loess Plateau to emphasize millennial monsoon changes. We explore time series of loess proxies (magnetic susceptibility, CaCO 3 content, Ca/K, Fe/K, and Rb/Sr ratios) and speleothem δ18O records and decompose these proxies into intrinsic components using the ensemble empirical mode decomposition method. Synthesized signals of low- and high-frequency components can track the monsoon variability at glacial-interglcial and millennial timescales, respectively. The proportions of millennial components of the loess proxies vary from 9.4%~13.4%, less than that in Chinese speleothem δ18O record (~24.4%). Among five loess proxies, Fe/K ratio is the most sensitive indicator of millennial-scale summer monsoon oscillations, exhibiting abrupt changes similar to that of the Chinese speleothem δ18O record. The amplitude of abrupt monsoon changes recorded in Mangshan is larger during interglacials than glacials, which is in line with Gulang records, implying the lower sensitivity of loess proxies to weak weathering during glacilals and an interglacial amplification of abrupt summer monsoon changes. [ABSTRACT FROM AUTHOR]

Diverse wastes are produced during coal combustion and part of it is recycled worldwide in construction, agriculture, and other industries. As the waste becomes part of the environment, both intentionally and unintentionally, it is important to understand its long-term impact on surrounding soils. In this study, we characterized the situation where such waste, composed of mixed slag, fly ash, gangue, and coke material, was deposited 10–15 years ago as a layer within the urban soil. Two types of soil profiles were identified characterized by a different emplacement of the waste, which either occurred as a 10-cm thick layer or thin seams. Combined chemical and mineralogical analyses of the buried waste showed that slag fragments were affected by the dissolution of primary phases and precipitation of secondary carbonates, Fe-(hydr)oxides, and silica. The impact of the waste was detected in the underlying soils using ratios of trace elements enriched in the waste versus the uppermost soils (e.g., Ni/Pb, V/Zn, Ba/Pb) showing that it might be possible to recognize areas affected by similar deposited waste products. Combined leaching and mineralogical observations showed that V was released, but most probably as particles of unreactive V-rich sulfides, and Ba was preferentially leached from Ba-rich slag glass. Moreover, a combination of mineralogical observations, trace element ratios, and Pb isotopes showed that the thick layer of the waste may have acted not only as a source of potentially toxic elements but also as a trap (insulator) that stopped contamination coming from other sources (e.g., atmosphere). [Display omitted] • Mixed coal combustion waste has been buried in urban soil for 10–15 years. • The impact of waste can be detected in underlying soils using elemental ratios. • The waste may act not only as a source of metallic elements but also as a trap. • Selective Ba removal is potentially of environmental concern. [ABSTRACT FROM AUTHOR]

Highly time-resolved measurements of non-refractory submicron particulate matter (NR-PM 1) were performed using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) over a big urban city (Ahmedabad, 23.0°N, 72.6°E, 49 m amsl) of western India during the post-monsoon season. All the components of NR-PM 1 [i.e., organic aerosol (OA) SO 4 2 − , NO 3 − , NH 4 + and Cl − ] showed a strong diurnal variation with the overall dominance of OA (58%) in NR-PM 1 , and the OA composition was found to be a mixture of fresh and aged species. O/C varied from 0.04 to 0.91 whereas, H/C varied from 1.34 to 2.26. A strong diurnal variation in O/C caused a large variability in OM/OC ratio (ranging from 1.2 to 2.3) during the study period, which suggests that a constant conversion factor for OM estimation (from OC) can be a source of large uncertainty in their load assessment over the study region. Furthermore, the observed slope (−0.78 ± 0.01) of Van Krevelen (VK) diagram suggests that plausible major functional groups of ambient oxidized OA could be the mixture of alcohols and carboxylic groups. Further, a drastic change in NR-PM 1 concentrations and composition was observed during Diwali, a festival when huge amount of firecrackers are burnt across India. Three distinct sources of OA [i.e., primary OA (POA), semi-volatile oxygenated OA (SV-OOA), and low volatility OOA (LV-OOA)] were identified via positive matrix factorization (PMF) analysis. The OA mass was dominated by POA (42%), followed by LV-OOA (33%) and SV-OOA (25%). Diurnal variations in PMF factors suggest that OOA (SV-OOA + LV-OOA) were high during early morning and afternoon hours; whereas, POA was most abundant during traffic rush hours. Observations also revealed that the high OA loading events were dominated by POA during the study period. This study provides new insights on the atmospheric aging of OA, for the first time, over western India, which would be helpful in understanding the formation mechanism of secondary OA over this region. • First study on organic aerosol (OA) characteristics from the western India. • Composition of NR-PM 1 was dominated (58%) by OA. • OA was dominated by POA followed by LV-OOA and SV-OOA. • The slope of VK-diagram was −0.78 ± 0.01 during the study period. [ABSTRACT FROM AUTHOR]

Abstract We studied a 13-meter sediment core collected from La Mancha coastal lagoon, Veracruz, Mexico, to determine paleoenvironmental variations linked to the mid- to late Holocene sea-level rise. We examined modern and fossil benthic foraminiferal assemblages, isotopic values in tests of Ammonia tepida (δ18O-foram and δ13C-foram), δ13C in organic matter (δ13C-org), and sediment elemental ratios (Fe/Ca, Ca/Ti, and K/Rb) to reconstruct salinity variations, coastal processes, and the morphologic evolution of a partially closed coastal lagoon. We identified four main periods of environmental change: (1) From ~7800 to 6500 cal. yr. BP, the core site was an open lagoon with higher oceanic influence than today, through the presence of a southern mouth, as evidenced by the euryhaline assemblage Ammonia-Quinqueloculina-Bolivina-Nonionella. Low δ18O-foram and high δ13C values on foraminifera shells indicate greater inputs of seawater, and δ13C-org values reflect a lagoon environment. Elemental ratios of lower Fe/Ca, moderate Ca/Ti, and higher K/Rb suggest increased coastal weathering and reduced detrital deposits than today. (2) From ~6500 to 4600 cal. yr. BP., the lagoon experienced the progressive closure of the southern mouth, to the point that sedimentation restricted seawater entrance, as evidenced by variable δ13C-org values, a lowering trend in δ18O-foram and δ13C-foram values, low Fe/Ca, higher Ca/Ti but moderate K/Rb values. At this time, benthic foraminifera were dominated by the opportunistic Ammonia-Elphidium polyhaline assemblage. (3) From ~4600 to 1400 cal. yr. BP, the northern mouth was the only source of seawater to the lagoon, establishing the optimal environment for calcareous foraminifera of the polyhaline assemblage Ammonia-Elphidium. Lowest δ13C-org values indicate greater organic input by terrestrial plants. (4) At 1400 cal. yr. BP, modern conditions of a partially closed lagoon were established, while increased terrigenous inputs and freshwater runoff favored the growth of agglutinated foraminifera species. At millennial time scales, in addition to the sea level rise effects, the lagoon evolution fits in the paleoclimatic context that links insolation, the latitudinal change of ITCZ, ocean currents, longshore drift and moisture transport, as driving factors of morphological change in the western coast of the Gulf of Mexico. Highlights • Lagoon evolution over mid to late Holocene shows four environmental and sea-level episodes. • Benthic foraminifera assemblages vary in agreement to shifts in salinity and ocean proximity. • In the mid-Holocene, the open lagoon was euhaline with two mouths that enhanced ocean intrusion. • In the late-Holocene, the partially closed lagoon was polyhaline to oligohaline with an ephemeral inlet. • Sea-level rise, shifts in insolation, ITCZ and ocean currents are millennial-scale controls on coastal evolution. [ABSTRACT FROM AUTHOR]

Stoichiometric ratios of resources and consumers have been used to predict nutrient limitation across diverse terrestrial and aquatic ecosystems. In forested headwater streams, coarse and fine benthic organic matter (CBOM, FBOM) are primary basal resources for the food web, and the distribution and quality of these organic matter resources may therefore influence patterns of secondary production and nutrient cycling within stream networks or among biomes. We measured carbon (C), nitrogen (N), and phosphorus (P) content of CBOM and FBOM and calculated their stoichiometric ratios (C/N, C/P, N/P) from first- to fourth-order streams from tropical montane, temperate deciduous, and boreal forests, and tallgrass prairie, to compare the magnitude and variability of these resource types among biomes. We then used the ratios to predict nutritional limitations for consumers of each resource type. Across biomes, CBOM had consistently higher %C and %N, and higher and more variable C/N and C/P than FBOM, suggesting that microbial processing results in more tightly constrained elemental composition in FBOM than in CBOM. Biome-specific differences were observed in %P and N/P between the two resource pools; CBOM was lower in %P but higher in N/P than FBOM in the tropical montane and temperate deciduous forest biomes, while CBOM was higher in %P but similar in N/P than FBOM in the grassland and boreal forest biomes. Stable 13C isotopes suggest that FBOM likely derives from CBOM in tropical and temperate deciduous forest, but that additional non-detrital components may contribute to FBOM in boreal forests and grasslands. Comparisons of stoichiometric ratios of CBOM and FBOM to estimated needs of aquatic detritivores suggest that shredders feeding on CBOM are more likely to experience nutrient (N and/or P) than C limitation, whereas collector-gatherers consuming FBOM are more likely to experience C than N and/or P limitation. Our results suggest that differences in basal resource elemental content and stoichiometric ratios have the potential to affect consumer production and ecosystem rates of C, N, and P cycling in relatively consistent ways across diverse biomes. [ABSTRACT FROM AUTHOR]

Hydrological changes in East Asia during the last millennium have been addressed by numerous earlier studies, but spatial characteristics and dynamics in precipitation variations during the Little Ice Age (LIA) remain unclear, perhaps especially due to the sparse coverage of high-resolution hydrological records from tropical and sub-tropical regions in East Asia. In this study, a sediment core was obtained from Shuangchi Lake in northern Hainan Island, tropical China, of which geochemical proxies including the ratios of Rb/Sr, Rb/K, Zr/Rb and Si/Ti were analyzed using an X-ray fluorescence (XRF) core scanner. Meanwhile, the grain size distribution of sediments was also determined. The results show that the Rb/Sr and Rb/K ratios decreased significantly during the LIA, whilst the Zr/Rb and Si/Ti ratios increased along with higher median grain size. The changes of these proxies likely suggest that precipitation was enhanced during the LIA in this region, and this was consistent with other hydrological records from tropical southern China. The synthesis of hydrological records from East Asia and the tropical Pacific suggest that the co-existence of a contracted Intertropical Convergence Zone (ITCZ) and strengthened Pacific Walker circulation (PWC) could contribute synchronously to the increased precipitation in the tropical region of southern China during the LIA. [ABSTRACT FROM AUTHOR]

The Kuroshio, flowing through the eastern end of the East China Sea, transports terrestrial material to the Northwestern Pacific Ocean. Along the Kuroshio path, we collected size‐fractionated suspended particles in the upper 200 m to investigate the composition and sources of particulate trace metals. Demonstrated by Al‐ and P‐normalized elemental ratios, we found that anthropogenic aerosol deposition was the major source of most particulate trace metals in the Kuroshio region although the impact of bottom resuspension and riverine input may be significant at some specific regions. As seen in our previous studies in the South China Sea and the Western Philippine Sea, this study concluded that anthropogenic aerosol deposition is the dominant particulate trace metal source in the surface water of the Northwestern Pacific Ocean and its marginal seas. Compared to particulate trace metal composition obtained in other open oceans, we found that the distribution patterns of particulate trace metal composition in the surface waters are closely associated with aerosol deposition fluxes. In regions with low deposition, the particulate trace metal concentrations were extremely low and metal to P ratios were all comparable to their intracellular quota previously proposed. In regions with high deposition, metal to P ratios were highly elevated in comparison to their intracellular quota and metal to Al ratios were deviated from lithogenic ratios to various extents. The globally consistent distribution patterns validate trace metal stoichiometry concept in plankton intracellularly and the primary role of aerosol deposition on deciding particulate trace metal composition in oceanic surface water globally. Plain Language Summary: The Kuroshio adjacent to the East China Sea is an ideal region to investigate the material exchange and transport from the marginal sea to the Northwestern Pacific Ocean. Particulate trace metals may serve as useful proxies or tracers for the sources of particulate materials in the Kuroshio and material exchange with the marginal seas and islands. In addition to aerosol transport, both anthropogenic and lithogenic materials carried by riverine or sediment transport may be additional sources of particulate trace metals in the studied region. In this study, we found that anthropogenic aerosol deposition is the dominant particulate trace metal source in the surface water. Compared to the data obtained in other open oceans, we further revealed that the distribution patterns of particulate trace metal composition in the surface waters are closely associated with aerosol deposition globally. The globally consistent distribution patterns also validate that plankton possess relatively constrained trace metal composition intracellularly. Key Points: Anthropogenic aerosol deposition is the dominant source of most particulate trace metals collected in the surface water of the KuroshioThe distribution patterns of particulate metal composition in the global surface water are associated with aerosol deposition fluxesThe distribution patterns of particulate metal composition validate intracellular trace metal stoichiometry concept in plankton [ABSTRACT FROM AUTHOR]

Results of clumped isotope, oxygen isotope and elemental (Mg/Ca, Sr/Ca) analyses of exceptionally well-preserved belemnite rostra and ammonite shells from the uppermost Callovian–Upper Kimmeridgian (Lamberti–Mutabilis zones) of the Russian Platform are presented. Despite a significant decrease in belemnite δ 18 O values across the Upper Oxfordian–Lower Kimmeridgian, the clumped isotope data show a constant seawater temperature (ca. 16 °C) in the studied interval. The decrease in belemnite δ 18 O values and lower δ 18 O values measured from ammonite shells are interpreted as a result of the salinity decline of the Middle Russian Sea of ca. 12‰, and salinity stratification of the water column, respectively. The postulated secular palaeoenvironmental changes are linked to the inflow of subtropical, saline waters from the Tethys Ocean during a sea-level highstand at the Middle–Late Jurassic transition, and progressive isolation and freshening of the Middle Russian Sea during the Late Oxfordian–Kimmeridgian. The obtained clumped isotope data demonstrate relative stability of the Late Jurassic climate and a paramount effect of local palaeoceanographic conditions on carbonate δ 18 O record of shallow epeiric seas belonging to the Subboreal Province. Variations in Mg/Ca and Sr/Ca ratios of cylindroteuthid belemnite rostra, which are regarded by some authors as temperature proxies, are, in turn, interpreted to be primarily dependent on global changes in seawater chemistry. The paleoenvironmental variations deduced from clumped and oxygen isotope records of the Russian Platform correspond well with changes in local cephalopod and microfossil faunas, which show increasing provincialism during the Late Oxfordian and the Early Kimmeridgian. Based on the review of literature data it is suggested that the observed salinity decrease and restriction of Subboreal basins during the Late Jurassic played a major role in the formation of periodic bottom water anoxia and sedimentation of organic rich facies. [ABSTRACT FROM AUTHOR]

The Po Valley is one of the most important hot spots in Europe for air pollution. Morphological features and anthropogenic pressures lead to frequent breaching of air quality standards and to high-pollution episodes in an ~46 × 103-km2-wide alluvial lowland. Therefore, it is increasingly important to study the air quality in a wide geographical scale to better implement possible and successful mitigation measures. The Veneto region lies in the eastern part of the Po Valley and the elemental composition of PM has been mainly studied in the Venice area, whereas scarce data are available for the remaining territory of the region. In this study, the elemental composition of PM2.5 was investigated over 1 year (2012–2013) at six major cities of the Veneto region. Samples were analyzed for 16 elements (Ca, Al, Fe, S, K, Mg, Ti, Mn, Zn, Ba, As, Ni, Pb, Sb, V, and Cu), and results were processed to investigate spatial and seasonal variations, the influence of meteorological factors, and the most probable sources by using a procedure based on (i) elemental ratios (Cu/Sb, Cu/Zn, Cu/Pb, Mn/V, V/Ni, and Zn/Pb), (ii) cluster analysis on wind data, and (iii) conditional probability function (CPF). The percentage of elements in PM2.5 ranged between 11 and 20%, and Ca and S were the most abundant elements in the region. Typical seasonal variations and similar trends were exhibited by each element, especially in the lowland. Some elements such as Zn, K, Mn, Pb, and Sb were found at high concentrations during the cold period. However, no similar dispersion processes were observed throughout the region, and their concentrations were mostly depending on individual local sources. In the alpine and foothill parts of the region, lower concentrations were recorded with respect to the Po Valley cities, which resulted enriched of most of the elements considered in this study. The cluster analysis on wind data and the CPF of the ratio-related sources demonstrated that a widespread pollution condition exists in the region, apart from the coastal area. However, specific directions (e.g., a link with high-traffic roads, industrial areas, and airports) resulted the most probable explanation for each ratio-related source. In addition, the Veneto region hosts one of the most important Mediterranean ports for the cruise sector (Venice harbor), and its impact was previously demonstrated in the historical city center. In this study, the impact of Venice shipping emissions was estimated to be 3.5% of PM2.5 in some particular days. [ABSTRACT FROM AUTHOR]

The aim of this study was to reveal the relative content of C, N, Ca, Si, P, Mg, K, S and Fe in seston particles in Norwegian coastal water (NCW), and how it relates to biological and hydrographic processes during seasonal cycles from October 2009–March 2012. The following over all stoichiometric relationship for the time series was obtained: C 66 N 11 Si 3.4 Ca 2.3 P 1 Mg 0.73 S 0.37 K 0.35 Fe 0.30 , which is novel for marine waters. A record-breaking (187-year record) negative North Atlantic Oscillation (NAO) index caused extreme physical forcing on the Norwegian Coastal Current Water (NCCW) during the winter 2009–2010, and the inflow and upwelling of saline Atlantic water (AW) in the fjord was thus extraordinary during late spring-early summer in 2010. The element concentrations in fjord seston particles responded strongly to this convection, revealed by maximum values of all elements, except Fe, exceeding average values with 10.8 × for Ca, 9.3 for K, 5.3 for S, 5.1 for Mg, 4.6 for Si, 4.0 for P, 3.8 for C, and 3.3 for N and Fe. This indicates that the signature of the Atlantic inflow was roughly two times stronger for Ca and K than for the others, probably connected with peaks in coccolithophorids and diatoms. There is, however, 1.5 × more of Si than Ca contained in the seston, which could be due to a stronger dominance of diatoms than coccolithophorids, confirming their environmental fitness. In total our data do not indicate any severe nutrient limitation with respect to N, P and Fe, but accumulation of iron by Fe-sequestering bacteria might at times reduce the availability of the dissolved Fe-fraction. There is a high correlation between most of the measured elements, except for Ca, which together with Fe only weakly correlated with the other elements. It is to be expected that environmental alterations in NCW related to climate change will influence the seston elemental composition, but the full effect of this will be strongly dependent on the future dominance of the high pressure versus low pressure systems (i.e. NAO index), since they are key regulators for the direction of wind driven vertical convection (i.e. upwelling or downwelling). Changes in stratification, temperature, light, pH (ocean acidification), CaCO 3 concentrations (carbon pump) and availability of nutrients in the euphotic zone (biogeochemical cycling) are essential for the future dominance of coccolithophorids versus diatoms. [ABSTRACT FROM AUTHOR]

New carbon and oxygen isotope records and discussion of the main variations in seawater temperature through the Sinemurian–Aalenian of the Pieniny Klippen Basin (northern Tethys Ocean) are presented herein. Comparison of the recorded changes in stable-isotope compositions of bulk carbonate and belemnite rostra from an open-marine environment with previously documented, predominantly restricted epicontinental data enables determination of major climatic events that were most likely of worldwide extent. A slight positive δ 13 C shift is recorded in the lowermost Upper Pliensbachian. A significant positive excursion in carbonate carbon isotope values is documented in the Lower Toarcian Serpentinum Zone. Furthermore, the δ 13 C values display a falling trend in the Lower–Upper Toarcian and relatively constant values in the Aalenian. Temperatures inferred from the δ 18 O values of well-preserved belemnite rostra suggest rather cool seawater conditions (10–13 °C) in the Pieniny Klippen Basin during the Late Sinemurian, warming by 4 °C in the Early Pliensbachian and then cooling by 8 °C in the Late Pliensbachian. The seawater temperature rose once more in the Early Toarcian and began to fall again during the Middle Toarcian. In the Middle–?Late Aalenian, seawater temperatures oscillated between 10 and 13 °C. [ABSTRACT FROM AUTHOR]

Using benthic foraminiferal-based proxies in sediments from the Celtic margin, we provide a well-dated record across the last deglaciation of the Channel River dynamics and its potential impact on the hydrology of intermediate water masses along the European margin. Our results describe three main periods: 1) During the Last Glacial Maximum, and before ∼21 ka BP, the predominance of meso-oligotrophic species suggests well oxygenated water masses. After ∼21 ka BP, increasing proportions of eutrophic species related to enhanced riverine supply occurs concomitantly with early warming in Greenland air-temperatures; 2) A thick laminated deposit, occurring during a 1500-years long period of seasonal melting of the European Ice Sheet (EIS), is associated with early Heinrich Stadial 1 period (∼18.2–16.7 ka BP). The benthic proxies describe low salinity episodes, cold temperatures, severe dysoxia and eutrophic conditions on the sea floor, perhaps evidence for cascading of turbid meltwaters; 3) During late HS1 (∼16.7–14.7 ka BP), conditions on the Celtic margin's seafloor changed drastically and faunas indicate oligotrophic conditions as a result of the ceasing of EIS meltwater discharges. While surface waters were cold due to Laurentide Ice Sheet (LIS) icebergs releases, increasing benthic Mg/Ca ratios reveal a progressive warming of intermediate water masses whereas oxygen proxies indicate overall well oxygenated conditions. In addition to the well known effect of EIS meltwaters on surface waters in the Celtic margin, our benthic record documents a pronounced impact on intermediate water depths during HS1, which coincided with major AMOC disruptions. [ABSTRACT FROM AUTHOR]

Coral skeletons are built by Ca-carbonate (calcite or aragonite) crystals that exhibit distinct morphological patterns and specific spatial arrangements that constitute skeletal microstructures. Additionally, the long-standing recognition that distinct coral species growing in similar conditions are able to record environmental changes with species-specific responses provides convincing evidence that, beyond the thermodynamic rules for chemical precipitation, a biological influence is at work during the crystallization process. Through several series of comparative structural and geochemical (elemental and isotopic) data, this paper aims to firmly establish the specific properties of the distinct major taxonomic units that are commonly gathered as deep-water "corals" in current literature. Moreover, taking advantage of recent micrometric and infra-micrometric observations, attention is drawn to the remarkable similarity of the calcareous material observed at the nanoscale. These observations suggest a common biomineralization model in which mineralogical criteria are not the leading factors for the interpretation of the geochemical measurements. [ABSTRACT FROM AUTHOR]

1. High biodiversity and biomass of soil communities are crucial for litter decomposition in terrestrial ecosystems such as tropical forests. However, the leaf litter that these communities consume is of particularly poor quality as indicated by elemental stoichiometry. The impact of resource quantity, quality and other habitat parameters on species richness and biomass of consumer communities is often studied in isolation, although much can be learned from simultaneously studying both community characteristics. 2. Using a dataset of 780 macro-invertebrate consumer species across 32 sites in tropical lowland rain forest and agricultural systems on Sumatra, Indonesia, we investigated the effects of basal resource stoichiometry (C:X ratios of N, P, K, Ca, Mg, Na, S in local leaf litter), litter mass (basal resource quantity and habitat space), plant species richness (surrogate for litter habitat heterogeneity) and soil pH (acidity) on consumer species richness and biomass across different consumer groups (i.e. 3 feeding guilds and 10 selected taxonomic groups). 3. In order to distinguish the most important predictors of consumer species richness and biomass, we applied a standardised model averaging approach investigating the effects of basal resource stoichiometry, litter mass, plant species richness and soil pH on both consumer community characteristics. This standardised approach enabled us to identify differences and similarities in the magnitude and importance of such effects on consumer species richness and biomass. 4. Across consumer groups, we found litter mass to be the most important predictor of both species richness and biomass. Resource stoichiometry had a more pronounced impact on consumer species richness than on their biomass. As expected, taxonomic groups differed in which resource and habitat parameters (basal resource stoichiometry, litter mass, plant species richness and pH) were most important for modulating their community characteristics. 5. The importance of litter mass for both species richness and biomass indicates that these tropical consumers strongly depend on habitat space and resource availability. Our study supports previous theoretical work indicating that consumer species richness is jointly influenced by resource availability and the balanced supply of multiple chemical elements in their resources. [ABSTRACT FROM AUTHOR]

Fluxes of acidity and contaminants from acid mine drainage (AMD) sources to the receiving surface water bodies were studied in a mining-impacted watershed (Meca River, SW Spain) using a novel methodology based on the joint application of EMMA and MIX codes. The application of EMMA and elemental ratios allowed delimiting the end-members responsible for water quality variations at a catchment scale. The further application of MIX quantified the significant impact of AMD on the river quality; less than 10% of AMD relative contribution is enough to maintain acidic conditions during most of the year. The mixing model also provided information about the element mobility, distinguishing those elements with a quasi-conservative behavior (e.g., Cu, Zn, Al, Co or Ni) from those affected by mineral precipitation/dissolution (e.g., K, Si, Na, Sr, Ca, Fe, Pb, or As). Floods are the main driver of dissolved and, mainly particulate, contaminants in the catchment. Thus, the first rainfall events in November only accounted for 19% of the annual Meca flow but yielded between 26 and 43% of the net acidity and dissolved metal loads (mainly, Fe, As and Pb). Concerning particulate transport, around 332 tons of particulate Fe, 49 tons of Al, 0.79 tons of As and 0.37 tons of Pb were recorded during these first floods. The particulate As concentration can be up to 34 times higher than the dissolved one during floods and between 2 and 4 times higher for Fe, Pb and Cr. This integrated modeling approach could be a promising and useful tool to face future restoration plans in derelict mines worldwide. This approach would allow prioritizing remedial measures, achieving an environmental and cost-effective restoration of degraded areas. [ABSTRACT FROM AUTHOR]

El Niño–Southern Oscillation (ENSO) has a strong influence on the climate of the Changjiang River basin, China, most notably upon extreme events such as flooding and drought. However, long-term historical records, which reveal the impacts of ENSO variability on climatic and environmental changes in this region, are scarce. A sediment core (G9) was collected from the estuarine delta of the Changjiang River. And its elemental ratios, mineral compositions, and grain size distribution were analyzed to investigate the links between sediment parameters in this region and the history of ENSO variability during the last century. Observed variations in K 2 O/Na 2 O, Al 2 O 3 /SiO 2 , and Rb/Sr ratios are synchronous with changes in mineral compositions and grain size throughout the sediment core. Lower K 2 O/Na 2 O, Al 2 O 3 /SiO 2 , and Rb/Sr ratios generally correspond to lower ratios of clay minerals to rock-forming minerals and larger grain sizes, which in turn correspond to periods of flooding in the Changjiang River basin. Such trends probably reflect increased physical erosion and the transport of greater amounts of coarse-grained suspended matter to the estuary. These geochemical proxies are also positively correlated with sea surface temperature anomalies in the Niño-3.4 region (120°W–170°W, 5°S–5°N) (using a low-pass filter with a cut-off of 13 years). We therefore conclude that (1) ENSO-related flood events in the Changjiang River basin have a strong influence on physical erosion processes in the upper catchment area and thereby influence the grain size distribution, elemental ratios, and mineral compositions of the estuarine sediments; and (2) the geochemical records presented here can serve as a proxy for ENSO-driven regional weathering variations on decadal to centennial time scales, because they could potentially be recorded in longer sediment cores recovered from the Changjiang River estuary. [ABSTRACT FROM AUTHOR]

The Ocean Cockle Fishery is a small fishery in southern New South Wales targeting three bivalve species:Eucrassatella kingicola;Glycymerisgrayana; andCallista(Notocallista)kingii. The fishery currently consists of a single licensed fisher harvesting a defined patch of seabed but has been identified as potentially able to support expansion. All target species have unknown population dynamics and life histories, and the degree to which expansion can be supported is therefore also unknown. We used internal growth marks in cross sections of shell to determine ages from the commercial catch. The assumption that the alternating bands represent seasonal variations in growth rate was validated by laser ablation induction-coupled plasma mass spectrometry (LA-ICPMS), a small tag-recapture program and preliminary marginal increment analysis. Mean length-at-age was modelled using the von Bertalanffy growth equation.Callista kingii(L∞ = 43.8,K = 0.43) grew substantially faster to a smaller maximum size thanE. kingicola(L∞ = 70.0,K = 0.18) andG. grayana(L∞ = 54.3,K = 0.20). These growth characteristics may explain anecdotal observations thatC. kingiihas increased in relative abundance in recent catches and is relatively rare in unfished areas whileE. kingicolain particular has declined in mean size and abundance. [ABSTRACT FROM PUBLISHER]

Archaeological shell and fish middens are rich sources of paleoenvironmental proxy data. Patelloid limpet shells are common constituents in archaeological middens found along European, African, and South American coastlines. Paleotemperature reconstructions using oxygen isotope ratios of limpet shells depend on the ability to constrain the oxygen isotope ratio of seawater; therefore, alternative proxies are necessary for coastal localities where this is not possible. The study evaluates whether Mg/Ca, Sr/Ca, Li/Ca, Li/Mg, and Sr/Li ratios are reliable proxies of sea surface temperature (SST) in the calcite layer of shells of the patelloid limpets, Patella vulgata and Nacella deaurata . We compare Mg/Ca, Sr/Ca, Li/Ca, Li/Mg, and Sr/Li ratios to the seasonal variations in contemporaneous δ 18 O shell values, which primarily record seasonal changes in SST. Elemental ratios (Mg/Ca, Sr/Ca, Li/Ca, Li/Mg, and Sr/Li) show no significant correlations with reconstructed SST in P. vulgata and N. deaurata shells, nor do they show sinusoidal cycles expected from a SST proxy. In addition, shell δ 13 C values show no significant ontogenetic trends, suggesting that these limpets exhibit little change in metabolic carbon incorporation into the shell with increasing ontogenetic age. Although shell growth rate exhibits a logarithmic decrease with age based on calculated linear extension rates, growth rate does not correlate with elemental profiles in these limpets. Overall, elemental ratios are not reliable recorders of paleotemperature in patelloid limpets. [ABSTRACT FROM AUTHOR]

Ninety-six particulate matter (PM10) chemical source profiles for geological sources in typical cities of southwest China were acquired from Source Profile Shared Service in China. Twenty-six elements (Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Sr, Cd, Sn, Sb, Ba, Be, Tl and Pb), nine ions (F-, Cl-, SO42-, NO3-, Na+, NH4+, K+, Mg2+ and Ca2+), and carbon-containing species (organic carbon and elemental carbon) were determined to construct these profiles. Individual source profiles were averaged and compared to quantify similarities and differences in chemical abundances using the profile-compositing method. Overall, the major components of PM10 in geological sources were crustal minerals and undefined fraction. Different chemical species could be used as tracers for various types of geological dust in the region that resulted from different anthropogenic influence. For example, elemental carbon, V and Zn could be used as tracers for urban paved road dust; Al, Si, K+ and NH4+ for agricultural soil; Al and Si for natural soil; and SO42- for urban resuspended dust. The enrichment factor analysis showed that Cu, Se, Sr and Ba were highly enriched by human activities in geological dust samples from south-west China. Elemental ratios were taken to highlight the features of geological dust from south-west China by comparing with northern urban fugitive dust, loess and desert samples. Low Si/Al and Fe/Al ratios can be used as markers to trace geological sources from southwestern China. High Pb/Al and Zn/Al ratios observed in urban areas demonstrated that urban geological dust was influenced seriously by non-crustal sources. [ABSTRACT FROM AUTHOR]

Considering recent increases in anthropogenic N loading, it is essential to identify the controls on N removal and retention in aquatic ecosystems because the fate of N has consequences for water quality in streams and downstream ecosystems. Biological uptake of nitrate (NO3−) is a major pathway by which N is removed from these ecosystems. Here we used data from the second Lotic Intersite Nitrogen eXperiment (LINX II) in a multivariate analysis to identify the primary drivers of variation in NO3− uptake velocity among biomes. Across 69 study watersheds in North America, dissolved organic carbon:NO3− ratios and photosynthetically active radiation were identified as the two most important predictor variables in explaining NO3− uptake velocity. However, within a specific biome the predictor variables of NO3− uptake velocity varied and included various physical, chemical, and biological attributes. Our analysis demonstrates the broad control of elemental stoichiometry on NO3− uptake velocity as well as the importance of biome-specific predictors. Understanding this spatial variation has important implications for biome-specific watershed management and the downstream export of NO3−, as well as for development of spatially explicit global models that describe N dynamics in streams and rivers. [ABSTRACT FROM AUTHOR]

Otolith chemical signatures were used to estimate the number of likely nursery sources that contributed recruits to a suite of red snapper (Lutjanus campechanus) year-classes sampled in 2012 in US Atlantic Ocean waters from southern Florida (28°N) to North Carolina (34°N). Otoliths from subadult and adult fish (n=139; ages 2-5 years) were cored and their chemical constituents analysed for δ13C, δ18O, as well as the elemental ratios of Ba : Ca, Mg: Ca, Mn: Ca and Sr : Ca. Results from multiple linear regression analyses indicated that there was significant latitudinal variation for δ13C, Ba : Ca, Mg: Ca and Mn: Ca. Therefore, these variables were used to parameterise Markov Chain Monte Carlo (MCMC) models computed to estimate the most likely number of nursery sources to each age class. Results from MCMC models indicated that between two and seven nursery sources were equally plausible among the four age classes examined, but the likely number of nursery sources declined for fish aged 4 and 5 years because of apparent mixing between more northern and more southern signatures. Overall, there is evidence to reject the null hypothesis that a single nursery source contributed recruits among the age classes examined, but increased sample size from a broader geographic range may be required to refine estimates of the likely number of nursery sources. [ABSTRACT FROM AUTHOR]

In recent years portable X-ray fluorescence (pXRF) spectrometers have been recognised as an in-field tool for soil analyses as they offer rapid, real-time, simultaneous multi-element analysis of soil samples with no or minimal sample preparation. Portable XRF has been used quite extensively to estimate the degree of soil contamination with heavy metals and to measure the concentration of elements in soils that are important for the soil's fertility, but more recently it has also been used to calibrate for a range of soil chemical and physical properties to perform digital soil morphometrics. However, this still relatively new technology also offers an opportunity for soil scientists to investigate processes of pedogenesis in the field, which in turn will complement the in-field descriptions of soils profoundly. Here, we employed a handheld pXRF spectrometer to investigate the pedogenesis pathways and likely parent materials of three different soil types, utilizing elemental concentration data and geochemical indices. Our study site, a property called ‘Nowley’, is situated on the Liverpool Plains in the Spring Ridge district on the North West Slopes of New South Wales, Australia, in one of the most versatile dryland cropping regions of the continent. The variation in soil types and parent materials across the property offers an unique opportunity to study the impact of parent materials and topography on soil formation. A total of three soil pits were excavated to a depth of 1.0 m to expose the lower B horizons. Soil pit faces were then scanned at 0.1 m depth increments starting from the top of the soil profile to the lowest B horizon exposed. Our results show that elemental data acquired in field condition, which are affected by sample heterogeneities and soil moisture content, are comparable to elemental data acquired in air-dried, ground condition, as geochemical index values show similar trends down the soil profile. We found that the use of pXRF is a very effective in-field tool to assess pedogenic pathways and parent material origin, because of the instant computation of weathering indices and elemental ratios. We conclude that pXRF can be applied successfully and readily to study the soil's weathering history and identify processes of soil formation in the field. [ABSTRACT FROM AUTHOR]

ABSTRACT Millennial-scale monsoon variability has been investigated intensively using loess-based proxies; however, the amplitude and rhythms of millennial-scale signals have seldom been disentangled from the background glacial-interglacial changes. Here we present the results of high-resolution scanning X-ray fluorescence analysis of a 75-m-thick loess sequence from the north-western Chinese Loess Plateau to address glacial-interglacial to millennial monsoon variability over the last two climatic cycles. Variations of the Si/K, Fe/K and Ca/K ratios are separated spectrally into low- and high-frequency components corresponding to glacial-interglacial and millennial-scale monsoon variability, respectively. The results indicate that the three elemental ratios exhibit similar glacial-interglacial variability but with varying spectral densities at the 100-, 41- and 23-kyr periodicities. Millennial-scale variability is quite similar between the three elemental ratios, and comparable to those inferred from records of Chinese speleothem δ18O, Greenland palaeotemperature and North Atlantic cooling events. Comparison of various proxies indicates the broad similar magnitudes of abrupt climate changes, at least during the last two glacial-interglacial cycles, whereas the timing and amplitude of abrupt climatic events are not well correlated. We suggest that refinement of loess chronology and intensive data-model integration in the future are critical to decipher the characteristics and dynamics of rapid monsoon changes. [ABSTRACT FROM AUTHOR]

Chemical elements in lake water are incorporated into fish tissues through bioconcentration and biomagnification. Lake water and fish tissue samples from 23 lakes, located within 4 major South African catchments, were analysed to investigate the link between element concentrations in lake water and otolith, fin spine, muscle, liver and gill tissues. The comparison is complicated by the seasonal variation in water chemistry as well as the large natural variation between individual fish within a lake. Comparisons between fish from different lakes can also only be done within the same species, which may not occur within all the lakes within the project area. This may be further complicated by erratic anthropogenic contamination. It is therefore more successful to use inter-element ratios for comparison than absolute element concentrations. Using the Sr/Ca elemental ratio, a species-specific correlation was identified between lake water, otolith, fin spine and gill tissue samples. The best discrimination between fish species was achieved using a Na/Ca versus Mg/Ca elemental ratio diagram of gill tissues. The best discrimination between fish from different lakes was achieved using a Ba/Mg versus Sr/Mg elemental ratio diagram for fin spine tissue. [ABSTRACT FROM AUTHOR]

Corals have long been used as proxies for changes in the seawater environment. However, the existence of trace element and isotopic inconsistencies between different coral species and within different architectural elements of the same species grown simultaneously suggests that factors besides seawater temperature and its chemical composition contribute to coral geochemical records. Secondary Ion Mass Spectrometry (SIMS) analysis was conducted on the reef building coral Orbicella annularis from the Veracruz Reef System, in the Southern Gulf of Mexico in order to investigate variability in oxygen isotopes (δ 18 O) and elemental calcium ratios between the different architectural structures of this coral. The microstructures of Orbicella include thecae walls, septa, costae, exothecal dissepiments (ExDs), and endothecal dissepiments (EnDs). SIMS data showed that EnDs are isotopically heavier by 0.7‰ than other simultaneously grown structures. The elemental heterogeneity between architectural structures was observed by LA-ICP-MS: EnDs were found to become depleted in Mg/Ca, B/Ca and enriched in Ba/Ca, U/Ca relative to thecae. Elemental and isotopic spot profiles (with a 6.5 mm long sampling path) in the coral growth direction yielded weekly time resolution and demonstrated that factors other than temperature — including aragonite growth rate and modification of calcifying fluid chemistry — also affect elemental and isotopic ratios in corallite aragonite. [ABSTRACT FROM AUTHOR]

Despite the progress made in explaining trophic interactions through the stoichiometric interplay between consumers and resources, it remains unclear how the number of species in a trophic group influences the effects of elemental imbalances in food webs. Therefore, we conducted a laboratory experiment to test the hypothesis that multispecies producer assemblages alter the nutrient dynamics in a pelagic community. Four algal species were reared in mono- and polycultures under a 2 x 2 factorial combination of light and nutrient supply, thereby contrasting the stoichiometry of trophic interactions involving single vs. multiple producer species. After 9 d, these cultures were fed to the calanoid copepod Acartia tonsa, and we monitored biomass, resource use, and C:N:P stoichiometry in both phyto- and zooplankton. According to our expectations, light and N supply resulted in gradients of phytoplankton biomass and nutrient composition (C:N:P). Significant net diversity effects for algal biomass and C:N:P ratios reflected the greater responsiveness of the phytoplankton polyculture to altered resource supply compared to monocultures. These alterations of elemental ratios were common, and were partly triggered by changes in species frequency in the mixtures and partly by diversity-related changes in resource use. Copepod individual biomass increased under high light (HL) and N-reduced (+N) conditions, when food was high in C:N but low in C:P and N:P, whereas copepod growth was obviously P limited, and copepod stoichiometry was not affected by phytoplankton elemental composition. Correspondingly, copepod individual biomass reflected significant net diversity effects: compared to expectations derived from monocultures, copepod individuals feeding on algal polycultures remained smaller than predicted under HL and N-sufficient (+N) conditions but grew larger than predicted under HL, +N and low light +N conditions. In conclusion, multiple producer species altered the stoichiometry of trophic interactions between phyto- and zooplankton, with divergent effects under high and low resource supply. [ABSTRACT FROM AUTHOR]

The Jiang harbor-centered radial sand ranges (RSRs) off the Jiangsu coast are the largest in the Yellow Sea. However, the provenance of the RSRs remains controversial. In this study, we compare major and trace element geochemistry together with grain size and main mineral composition in carbonate-free sediments from RSRs and potential sources. Onshore and offshore RSR sediments have different grain size characteristics: onshore RSR sediments have mean grain-sizes of < 50 μm whereas offshore RSR sediments are between 50 and 160 μm in mean grain size. Despite these differences in grain size onshore and offshore RSRs have similar mineral compositions. Relative to upper continental crust (UCC), onshore RSR sediments are enriched in SiO 2 , TiO 2 , Li and partly in Cs, Zn and some high field strength elements (Y, Zr, Nb, Pb and Th) while depleted in other elements. Offshore RSR sediments are complicated in geochemical compositions. Some of them have very high contents of high field strength elements, and others are similar to onshore RSR sediments. Onshore and offshore RSR sediments have different controlling factors of geochemical compositions: onshore RSR sediments are influenced by clay-size minerals whereas offshore sediments are controlled by heavy minerals. The identification of Zr/Nb and Ti/Zr vs. K/Rb shows that onshore and offshore RSRs seem to have similar sources. Their differences in grain size are a result of hydrodynamic sorting. The identification of elemental ratios reveals that sources of RSR sediments are variable in space and time and the inputs of the Chinese Rivers, especially the old Yellow River and the Yangtze River are still dominant but the effect of the Korean field cannot be neglected. Our findings also demonstrate the potential of elemental ratios such as Zr/Nb and K/Rb as tracer pairs for provenance of sediments in the Yellow Sea. [ABSTRACT FROM AUTHOR]

Marine sediments record paleoenvironmental changes over time through variations in major and trace element concentrations. The main objective of this paper is to review such changes in the Mediterranean Sea basins over the last 20 ka, using the inorganic chemistry and mineralogy of marine sediment records. Elemental ratio proxies that are mostly used are discussed, and the uncertainties involved in using them for paleoclimate and paleoceanographic reconstructions are evaluated. The focus on the Mediterranean region is based on the sensitivity of this region to global climate changes due to its semi-enclosed nature. The elemental ratios that have been particularly useful for reconstructing terrigenous inputs into the Mediterranean have been Ti/Al and Zr/Al ratios as proxies for eolian dust input, and Mg/Al, K/Al and Rb/Al ratios as proxies for fluvial input. Redox sensitive elements (e.g., U, Mo, V, Co, Ni, Cr) have provided reliable reconstructions of oxygen conditions at the time of deposition. Some of these elements are also particularly susceptible to post-depositional remobilization and record diagenetic processes instead of the original environmental signatures. Regarding productivity fluctuations, most of the paleoproductivity reconstructions are based on the abundance of barite and Ba excess algorithms. The biogeochemistry of Ba is, however, not fully understood and mechanisms for barite precipitation in the water column are not yet known. Two case studies are presented: the eastern Mediterranean sapropel S1 (deposited between 10.8 and 6.1 cal ka BP) and the westernmost Mediterranean paleoclimate record over the last 20 ka. [ABSTRACT FROM AUTHOR]

Understanding the natural variability of the Earth’s climate system and accurately identifying potential anthropogenic influences requires long term, geographically distributed records of key climate indicators, such as temperature and precipitation that extend prior to the last 400 years of the Holocene. Reef corals provide an excellent source of high resolution climate records, and importantly represent the tropical marine environment where palaeoclimate data are urgently required. Recent decades have seen significant improvement in our understanding of coral biomineralisation, the associated uptake of geochemical proxies and methods of identifying and understanding the effects of both early and late, post depositional diagenetic alteration. These processes all have significant implications for interpreting geochemical proxies relevant to palaeoclimatic reconstructions. This paper reviews the current ‘state of the art’ in terms of coral based palaeoclimate reconstructions and highlights a key remaining problem. The majority of coral based palaeoclimate research has been derived from massive colonies of Porites . However, massive Porites are not globally abundant and may not provide material of a particular age of interest in those regions where they are present. Therefore, there is great potential for alternate coral genera to act as complimentary climate archives. While it remains critical to consider five key factors – vital effects, differential growth morphologies, geochemical heterogeneity in the skeletal ultrastructure, transfer equation selection and diagenetic screening of skeletal material – in order to allow the highest level of accuracy in coral palaeoclimate reconstructions, it is also important to develop alternate taxa for palaeoclimate studies in regions where Porites colonies are absent or rare. Currently as many as nine genera other than Porites have proven at least limited utility in palaeothermometry, most of which are found in the Atlantic/Caribbean region where massive Porites do not exist. Even branching taxa such as Acropora have significant potential to preserve environmental archives. Increasing this capability will greatly expand the number of potential geochemical archives available for longer term temporal records of palaeoclimate. [ABSTRACT FROM AUTHOR]