Biogenic Activity Research Articles

Atmospheric CO2 column concentration over Iran: Emissions, GOSAT satellite observations, and WRF-GHG model simulations

Regarding global warming and climate change, carbon dioxide (CO2) is one of the most important greenhouse gases. Simulating CO2 gas at hourly/weekly time intervals and desired vertical resolution is challenging due to the coarse horizontal resolution of global models. In this study, both column-averaged CO2 mixing ratio (XCO2) and vertical cross sections of CO2 mixing ratio were simulated by the Weather Research and Forecast Green House gas (WRF-GHG) model at spatial resolutions of 30 and 10 km for the Middle East region as the first domain, and Iran as the second domain. Simulations consider the primary CO2 sources (anthropogenic, biogenic, fire, and oceanic) and the Copernicus Atmosphere Monitoring Service (CAMS) dataset. XCO2 retrieved from GOSAT satellite observations was employed to evaluate the simulation results of the column-averaged CO2 concentrations in February and August 2010. The evaluations showed that the spatiotemporal variability of meteorological variables was well simulated by WRF-GHG with correlation coefficients r of 0.86–0.92, 0.67–0.75, and 0.76–0.82 for temperature, wind, and relative humidity, respectively, during February and August 2010. The evaluations also indicated that the WRF-GHG simulations outperformed the global model TM3, with mean bias error values of − 0.79 and 0.45 PPMV for WRF-GHG in February and August, respectively. The percentage contribution of net CO2 emissions from human activities in Iran was calculated as (38.33 % and 23.70 %) of the total emissions, respectively, with values of 4.4 and 0.85 kg/km2 in each month. The net emissions contributions of biogenic, fire, and oceanic sources were evaluated in February and August, with biogenic emissions contributing (31.901 % and 27.66 %), biogenic absorption contributing (24.07 % and 46.63 %), fire emissions contributing (5.7 % and 2.064 %), and oceanic emissions contributing (3.23 × 10−6 % and 2.23 × 10−6 %). Large-scale circulations and biogenic activity are responsible for the major features of the spatial and seasonal distribution of CO2 in the area. In February, column mixing ratios are higher in more northern latitudes; in August, they are higher to the south. Furthermore, the simulated vertical cross sections show high CO2 mixing ratios in the mid-lower troposphere and northerly/northeasterly advection in February; the vertical profile is inverted in August with high concentrations in the lower stratosphere associated with southwesterly advection. However, the interaction between the synoptic and sub-synoptic features with the topography determines the precise dispersion and distribution of CO2. Despite the negligible emissions in central and eastern Iran, these factors play an important role in the observed concentrations in February and August. In August, the areas between the 120-day low-level monsoon flow of Sistan in eastern Iran, and the westerlies over western/southwestern Iran and the Zagros Mountain range, interact with the heat-low in the Iranian plains and with the Arabian subtropical high. In February, the dominant winds in western Asia were west winds, with the main source of pollution coming from the northeastern regions flowing towards central and eastern Iran. The equatorward displacement of the polar jet stream and the passage of low-pressure systems from the west in winter cause a temporary reduction in CO2 concentrations.

Transforming air pollution management in India with AI and machine learning technologies

A comprehensive approach is essential in India's ongoing battle against air pollution, combining technological advancements, regulatory reinforcement, and widespread societal engagement. Bridging technological gaps involves deploying sophisticated pollution control technologies and addressing the rural–urban disparity through innovative solutions. The review found that integrating Artificial Intelligence and Machine Learning (AI&ML) in air quality forecasting demonstrates promising results with a remarkable model efficiency. In this study, initially, we compute the PM2.5 concentration over India using a surface mass concentration of 5 key aerosols such as black carbon (BC), dust (DU), organic carbon (OC), sea salt (SS) and sulphates (SU), respectively. The study identifies several regions highly vulnerable to PM2.5 pollution due to specific sources. The Indo-Gangetic Plains are notably impacted by high concentrations of BC, OC, and SU resulting from anthropogenic activities. Western India experiences higher DU concentrations due to its proximity to the Sahara Desert. Additionally, certain areas in northeast India show significant contributions of OC from biogenic activities. Moreover, an AI&ML model based on convolutional autoencoder architecture underwent rigorous training, testing, and validation to forecast PM2.5 concentrations across India. The results reveal its exceptional precision in PM2.5 prediction, as demonstrated by model evaluation metrics, including a Structural Similarity Index exceeding 0.60, Peak Signal-to-Noise Ratio ranging from 28–30 dB and Mean Square Error below 10 μg/m3. However, regulatory challenges persist, necessitating robust frameworks and consistent enforcement mechanisms, as evidenced by the complexities in predicting PM2.5 concentrations. Implementing tailored regional pollution control strategies, integrating AI&ML technologies, strengthening regulatory frameworks, promoting sustainable practices, and encouraging international collaboration are essential policy measures to mitigate air pollution in India.

Formation conditions of Jixian System cherts in the Qishan area, Ordos Basin: Implications for marine redox conditions and paleoecology

Abundant chert bands and nodules are discovered throughout the Mesoproterozoic Jixian System in the Ordos Basin. These cherts faithfully record the Jixian period oceanic conditions and paleoecology. However, the diagenetic mechanism of the cherts remains unclear and controversial. To understand the origin of these cherts, we performed a multitracer study by combining field reconnaissance, petrological analyses, Si isotope analysis, and major and trace element analysis of chert samples from the Qishan section. The results show that Jixian cherts had a high Al/(Al + Fe + Mn) value (~0.48), showed a flat distribution of rare earth elements in seawater, and most of the Fe/Ti values are <20. A weak negative Ce anomaly (~0.97) indicates the contribution of REY to weakly oxygenated seawater. The high isotopic composition of silicon (δ30Si = 0.74 ‰-1.35 ‰) and the average Siex value of 37.52 indicate that there is a source of biological silica, and the relationship between Eu/Eu* and Y/Ho and δ30Si shows that the hydrothermal and volcanic influences were less and correlated with seawater. The chert bands were closely related to biological activities. The chert nodules were influenced by hydrothermal activity. Secondary cherts were related to diagenesis, but the nature of siliceous fluids remains unchanged, still characterized by biogenic activity origins. The sea oxygen concentration in the Jixian period had increased, with periodic variations in the intensity of biological activities affecting the pH of the water body, or biological photosynthesis binding SiO2 colloid in water, affecting chert sediments, leading to frequent interlayering between dolomite and chert bands. Episodic hydrothermal fluids and late-stage diagenetic processes jointly influenced the formation of cherts. This study bears significant significance in enhancing our understanding of the sedimentary environment and the origin of cherts during the Jixian period in the Ordos Basin.

Typhoon- and pollution-driven enhancement of reactive bromine in the mid-latitude marine boundary layer.

Tropospheric reactive bromine is important for atmospheric chemistry, regional air pollution, and global climate. Previous studies have reported measurements of atmospheric reactive bromine species in different environments, and proposed their main sources, e.g. sea-salt aerosol (SSA), oceanic biogenic activity, polar snow/ice, and volcanoes. Typhoons and other strong cyclonic activities (e.g. hurricanes) induce abrupt changes in different earth system processes, causing widespread destructive effects. However, the role of typhoons in regulating reactive bromine abundance and sources remains unexplored. Here, we report field observations of bromine oxide (BrO), a critical indicator of reactive bromine, on the Huaniao Island (HNI) in the East China Sea in July 2018. We observed high levels of BrO below 500m with a daytime average of 9.7±4.2 pptv and a peak value of ∼26 pptv under the influence of a typhoon. Our field measurements, supported by model simulations, suggest that the typhoon-induced drastic increase in wind speed amplifies the emission of SSA, significantly enhancing the activation of reactive bromine from SSA debromination. We also detected enhanced BrO mixing ratios under high NOx conditions (ppbv level) suggesting a potential pollution-induced mechanism of bromine release from SSA. Such elevated levels of atmospheric bromine noticeably increase ozone destruction by as much as ∼40% across the East China Sea. Considering the high frequency of cyclonic activity in the northern hemisphere, reactive bromine chemistry is expected to play a more important role than previously thought in affecting coastal air quality and atmospheric oxidation capacity. We suggest that models need to consider the hitherto overlooked typhoon- and pollution-mediated increase in reactive bromine levels when assessing the synergic effects of cyclonic activities on the earth system.

The sensitivity of Southern Ocean atmospheric dimethyl sulfide (DMS) to modeled oceanic DMS concentrations and emissions

Abstract. The biogeochemical formation of dimethyl sulfide (DMS) from the Southern Ocean is complex, dynamic, and driven by physical, chemical, and biological processes. Such processes, produced by marine biogenic activity, are the dominant source of sulfate aerosol over the Southern Ocean. Using an atmosphere-only configuration of the United Kingdom Earth System Model (UKESM1-AMIP), we performed eight 10-year simulations for the recent past (2009–2018) during austral summer. We tested the sensitivity of atmospheric DMS to four oceanic DMS datasets and three DMS transfer velocity parameterizations. One oceanic DMS dataset was developed here from satellite chlorophyll a. We find that the choice of oceanic DMS dataset has a larger influence on atmospheric DMS than the choice of DMS transfer velocity. Simulations with linear transfer velocity parameterizations show a more accurate representation of atmospheric DMS concentration than those using quadratic relationships. This work highlights that the oceanic DMS and DMS transfer velocity parameterizations currently used in climate models are poorly constrained for the Southern Ocean region. Simulations using oceanic DMS derived from satellite chlorophyll a data, and when combined with a recently developed linear transfer velocity parameterization for DMS, show better spatial variability than the UKESM1 configuration. We also demonstrate that capturing large-scale spatial variability can be more important than large-scale interannual variability. We recommend that models use a DMS transfer velocity parameterization that was developed specifically for DMS and improvements to oceanic DMS spatial variability. Such improvements may provide a more accurate process-based representation of oceanic and atmospheric DMS, and therefore sulfate aerosol, in the Southern Ocean region.

Algunos aspectos limnológicos abióticos de las cuencas de los ríos Limay y Neuquén con especial referencia al embalse Ramos Mexía

The Negro river tributaries are the Limay and Neuquen rivers, which constitute the Andean eastern drainage system betweem 36" and 41" S. Huge reservoirs have been constructed, as a part of a hydroelectric power program and also for flood control purposes.&#x0D; Morphometric and lithological differences accounts for thermal and chemical distinctive fractures between these reservoirs.&#x0D; The Ramos Mexía impoundment and Pellegrini off-channel reservoir are wind mixed all over the year, while in the deeper Los Barreales and Mari Menuco stratification develops during the summer.&#x0D; The annual heat budget of the Ramos Mexía has been raughly estimated in 36131, 30760 and 31047 cal cm-2 for the years 1978, 1979-1980 and 1980-1981 respectively. These estimates are higher than those for others lakes situated on the Andes mountains in a region of more oceanic climate.&#x0D; The waters of the system are well oxygenated, neutral and soft. The Limay basin waters are the more diluted, with an average conductivity of 30 μScm-1 near the glacial lake Nahuel Huapi, and 67 μScm-1 in the Ramos Mexía artificial lake. Conductivity seasonal changes are related with discharge flow rate patterns and with level changes in the reservoirs. The Neuquen basin waters present conductivities ranging from 75 μScm-1 near the Andes, to 250 μScm-1 in Mari Menuco reservoir, while the Pellegrini attains to 3600 μScm-1.&#x0D; Both rivers (and R. Mexía artificial lake) have calcium-bicarbonate type waters, beeoming richer in sulphate and sodium as they move seaward through a semiarid region. In Los Barreales and M. Menuco reservoirs bicarbonate and sulphate may change their relative positions during the annual hydrologic cycle. The Pellegrini dosed basin belong to the sulphate-chloride sodium type.&#x0D; Reactive silica concentration is rather high throughout the year, without showing depletion to any important extent due to biogenic activity, except in the Pellegrini artificial lake.

Coastal eutrophication driven by long-distance transport of large river nutrient loads, the case of Xiangshan Bay, China

With accelerating anthropogenic activities, the overloading of land-derived nutrients and the resultant eutrophication are threatening coastal aquatic habitats worldwide. In semi-enclosed coastal bays, eutrophication is always considered a local problem that can be mitigated by nutrient reduction at a regional scale. However, as the main nutrient drains major global river discharges can have far-reaching effects over hundreds of kilometers alongshore, which are usually not precisely recognized in local coastal zone management. Here, we first quantified the contributions from both local and remote nutrient sources in Xiangshan Bay (XSB), a eutrophic semi-enclosed bay in China 200 km south of the mouth of the Changjiang River (CJR, the world's third largest river), employing a salinity-based conservative mixing model. We found that the nutrients in Xiangshan Bay were mainly supplied by intruded coastal water fed by CJR discharge, contributing 63 % of dissolved inorganic nitrogen (DIN), 65 % of dissolved silicon (DSi), and 49 % of dissolved inorganic phosphorus (DIP) during the summer of 2017, and 75 % of DIN, 75 % of DSi and 60 % of DIP during the winter of 2019. Additionally, long-term interannual trends in the nutrient concentrations of XSB were generally synchronous with those of the downstream portion of the CJR, indicating that CJR discharge seems to be a strong driver of the eutrophication observed in XSB. In contrast, the impact of local nutrient inputs, such as riverine sewage drainage, aquaculture, biogenic activities, and elemental recycling, was much lower and was regionally limited to the inner bay. Interestingly, the DIP contributions of the local and remote sources were similar, indicating the greater relevance of the internal process. Overall, to mitigate eutrophication in large river-adjacent coastal bays, the inter-regional united practices for nutrient source regulation and ecosystem restoration should be permanently applied along the entire river basin-estuary-coastal continuum.

The environmental footprint of Holocene societies: a multi-temporal study of trails in the Judean Desert, Israel

The global distribution of footpaths and their inferred antiquity implies that they are widespread spatial and temporal anthropogenic landscape units. Arid environments are of special interest for investigating historically used footpaths, as older routes may preserve better due to minimal modern impact and slower pedogenic processes. Here we examine footpaths in the Judean Desert of the southern Levant, a human hotspot throughout the Holocene. We studied one modern and two archaeological footpaths (one attributed to the Early Bronze Age and one to the Roman period) using micromorphology, bulk samples laboratory analysis, and remote sensing. Field observations and color analysis indicate that footpaths in the studied arid limestone environment can result in brighter surface color than their non-path surroundings. Similar color changes are reflected using both laboratory analysis and high-resolution remote sensing, where the difference is also significant. Microscopically, the footpaths studied tend to be less porous and with fewer biogenic activities when compared to their non-path controls. However, the two ancient footpaths studied do exhibit minimal indicators of biogenic activities that are not detectable in the modern footpath sample. Our study shows that high-resolution remote sensing coupled with micromorphology, while using appropriate local modern analogies, can help to locate and assess both the environmental effect and the antiquity of footpaths.

MLR index-based principal component analysis to investigate and monitor probable sources of groundwater pollution and quality in coastal areas: a case study in East India.

Identifying groundwater contamination sources and supervising groundwater quality conditions are urgently needed to protect the groundwater resources of coastal areas like Contai of India, as communities here are heavily relying on groundwater which deteriorates progressively. So current research aims to address in detail about origins and influencing factors of groundwater contamination, status, and monitoring water quality by employing extremely useful leading technologies like principal component and factor analyses (PCA/FA), groundwater quality index (GWQI), and multiple linear regression (MLR) that helps to simplify complicated works instead of the conventional methods. Eight groundwater quality parameters were evaluated here, such as pH, TH (total hardness), Tur (turbidity), EC (electrical conductivity), TDS (total dissolved solids), Mn (manganese), Fe (iron), and Cl (chloride) for 38 sites. Three principal components with ~ 81% of the total variance were extracted from the PCA/FA analysis. The origin of maximum loadings of each factor is identified as a result of saline water, disintegration and leaching process, organic or else biogenic activities, and lithogenic or otherwise non-lithogenic links through percolating water. GWQI results show that ~ 87% of the samples fall into the good category and ~ 13% of the samples fall into the poor to very poor category. A model consisting of Tur, Fe, EC, Mn, TH, and Cl as independent parameters is more feasible and is proposed to predict GWQI obtained from MLR analysis. This MLR model also suggests that turbidity with the highest beta coefficient (0.820) is a key contributor relative to the entire groundwater class in this affected area. The findings relating to this research may support the designer and officials in monitoring and protecting coastal groundwater resources like selected areas.

Variation and trend of nitrate radical reactivity towards volatile organic compounds in Beijing, China

Abstract. Nitrate radical (NO3) is an important nocturnal atmospheric oxidant in the troposphere that significantly affects the lifetime of pollutants emitted by anthropogenic and biogenic activities, especially volatile organic compounds (VOCs). Here, we used 1 year of VOC observation data obtained in urban Beijing in 2019 to look into the level, composition, and seasonal variation in NO3 reactivity (kNO3). We show that hourly kNO3 towards measured VOC varied widely from &lt; 10−4 to 0.083 s−1 with a campaign-average value (± standard deviation) of 0.0032 ± 0.0042 s−1. There was large seasonal difference in NO3 reactivity towards VOC with averaged values (± standard deviation) of 0.0024±0.0026 s−1 (spring), 0.0067±0.0066 s−1 (summer), 0.0042±0.0037 s−1 (autumn), and 0.0027±0.0028 s−1 (winter). Alkenes such as isoprene and styrene accounted for the majority. Isoprene was the dominant species in spring, summer, and autumn, accounting for 40.0 %, 77.2 %, and 43.2 %, respectively. Styrene only played a leading role in winter, with a percentage of 39.8 %. A sensitivity study shows monoterpenes, the species we did not measure, may account for a large fraction of kNO3. Based on the correlation between the calculated kNO3 and VOC concentrations in 2019, we established localized parameterization schemes for predicting the reactivity by only using a part of VOC species. The historically published VOC data were collected using the parameterization method to reconstruct the long-term kNO3 in Beijing. The lower kNO3 during 2014–2021 compared with that during 2005–2013 may be attributed to anthropogenic VOC emission reduction. Finally, we revealed that NO3 dominated the nocturnal VOC oxidation, with 83 % of the annual average in Beijing in 2019, which varied seasonally and was strongly regulated by the level of kNO3, nitrogen oxide, and ozone. Our results improve the understanding of nocturnal atmospheric oxidation in urban regions and contribute to our knowledge of nocturnal VOC oxidation and secondary organic pollution.

Measurement report: Atmospheric CH4 at regional stations of the Korea Meteorological Administration–Global Atmosphere Watch Programme: measurement, characteristics, and long-term changes of its drivers

Abstract. To quantify CH4 emissions at policy-relevant spatial scales, the Korea Meteorological Administration (KMA) started monitoring its atmospheric levels in 1999 at Anmyeondo (AMY) and expanded monitoring to Jeju Gosan Suwolbong (JGS) and Ulleungdo (ULD) in 2012. The monitoring system consists of a cavity ring-down spectrometer (CRDS) and a new cryogenic drying method, with a measurement uncertainty (68 % c.i. (confidence interval)) of ± 0.7–0.8 ppb. To determine the regional characteristics of CH4 at each KMA station, we assessed the CH4 level relative to local background (CH4xs), analyzed local surface winds and CH4 with bivariate polar plots, and investigated CH4 diurnal cycles. We also compared the CH4 levels measured at KMA stations with those measured at the Mt. Waliguan (WLG) station in China and Ryori (RYO) station in Japan. CH4xs followed the order AMY (55.3 ± 37.7 ppb) &gt; JGS (24.1 ± 10.2 ppb) &gt; ULD (7.4 ± 3.9 ppb). Although CH4 was observed in well-mixed air at AMY, it was higher than at other KMA stations, indicating that it was affected not only by local sources but also by distant air masses. Annual mean CH4 was highest at AMY among all East Asian stations, while its seasonal amplitude was smaller than at JGS, which was strongly affected in the summer by local biogenic activities. From the long-term records at AMY, we confirmed that growth rate increased by 3.3 ppb yr−1 during 2006/2010 and by 8.3 ppb yr−1 from 2016 to 2020, which is similar to the global trend. Studies indicated that the recent global accelerated CH4-growth rate was related to biogenic sources. However, δ13CH4 indicates that the CH4 trend in East Asia is derived from both biogenic and fossil fuel sources from 2006 to 2020. We confirmed that long-term high-quality data can help understand changes in CH4 emissions in East Asia.

Seasonal trends and potential sources of aliphatic amines in the aerosols and gas phase at a forested site on the northern foot of Mt. Fuji, Japan

The present study measured the concentrations of aliphatic amines (methylamine (MA), ethylamine (EA), dimethylamine (DMA), diethylamine (DEA), trimethylamine (TMA), and triethylamine (TEA)) in both the aerosols and gas phase at a forested site in Japan, and discussed their seasonal trends and potential sources. These measured amines were more preferentially partitioned into the aerosols than into the gas phase, and mainly distributed into the fine-mode range in the aerosols, although the DMA and TMA were also abundant in the gas phase and the TMA in the aerosols was mainly distributed into the coarse-mode range. The most abundant amine both in the aerosol and gas phase was the DMA, followed by the MA. The MA, EA, DMA, and DEA in the gas phase and aerosols showed higher concentrations in the summer, although the coarse-mode EA concentration did not show the seasonality. The gaseous TMA also showed higher concentrations in the summer, but the coarse-mode TMA increased in the autumn and no seasonality was found in the fine-mode TMA concentrations. The TEA in the gas phase showed higher concentrations in the autumn, but that in the aerosols did not show the seasonality. The decomposition of organic materials in the soil and subsequent volatilization would be an important source of the gaseous MA, DMA, DEA, and TMA. Various biogenic activities can be also expected to be potential sources of the gaseous MA and DMA. The fine-mode MA, EA, DMA, DEA, TMA, and the coarse-mode DMA would be derived from their gaseous form through direct dissolution. Some portions of the fine-mode MA, DMA, and the coarse-mode DMA can be expected to be derived from the primary sources such as biogenic particles like plant debris. The transport of the anthropogenic aerosols can be also expected to contribute to the fine-mode MA. Only the TEA in the gas phase was suggested to be derived from the different sources in the forest from the other five gaseous amines and not contribute to the formation of the fine-mode TEA. It can be considered that the coarse-mode MA, EA, DEA, TMA, TEA, and the fine-mode TEA were affected by the sources independent from the local emission of the gaseous amines, such as the primary sources or the transport from distant sources, although some portions of the coarse-mode MA, EA and DEA might be derived from the dissolution of their gaseous form. Biogenic and pedospheric processes in the forest would be important sources for the amines, especially the gaseous and fine-mode amines, in a forest atmosphere.

Density and extractive potential of “uçá”-crab, Ucides cordatus (Linnaeus, 1763), in mangroves of the “Todos os Santos” Bay, Bahia, Brazil

Ucides cordatus is one of the main fishery resources of the “Todos os Santos” Bay (BTS), State of Bahia, Brazil. Population parameters (structure, density, and fishery potential) of this crab species were analyzed in the dry and rainy seasons in nine mangrove areas of BTS. Five sample quadrats (5 × 5 m) were used to record the number and diameter of active open burrows (with biogenic activity) and closed burrows of U. cordatus, tree variables (composition, density, and diameter), and flood level. Crab density (ind.m−2) was indirectly estimated by counting galleries. The diameter of open galleries was converted into carapace width (CW) using a regression model to later characterize the U. cordatus population structure. There were more galleries in the dry season than in the rainy season. Crab density ranged from 0.32 to 2.63 ind.m−2 (1.32 ± 0.90 ind.m−2), and the mean density was higher during the dry period (t = 0.02; p < 0.05). Crab density differed among sampling areas regardless of seasonal period. Crab size (CW) in BTS was 52.4 ± 16.7 mm, with specimens significantly larger during the dry period (t = 0.01; p < 0.05), and there was a significant difference (F = 4.57; p = 000.1) among mangrove areas. Non-commercial size animals (CW < 60.0 mm) were more abundant (65.2%) than those with commercial size (34.8%) in BTS. Crab density and flood level showed significant negative correlation (p = −0.51; p < 0.05), while there was a positive correlation between CW and flooding level (p = 0.40; p < 0.05). U. cordatus population parameters differed significantly among BTS sampling sites due to their heterogeneity. This study is the first assessment of “uçá”-crab populations in BTS mangroves and reveals a need for a sustainable management in the area. Furthermore, this study could be a model for monitoring other large brachyuran species inhabiting estuarine systems, which are economically and biologically relevant.

U-Pb DATING OF APATITE FROM SILVERMINES DEPOSIT, IRELAND: A MODEL FOR HYDROTHERMAL ORE GENESIS

AbstractUranium-Pb dating of unusual coarse-grained apatite crystals from hydrothermal dolostone breccia in the barite-rich Magcobar zone at the Silvermines deposit, Ireland, indicates an age of 331 ± 5.6 Ma for hydrothermal alteration. This age is in agreement with an Re-Os age on pyrite-sphalerite but differs from previous estimates that were based on palemomagnetism and sphalerite Rb-Sr geochronology at Silvermines. The new U-Pb age indicates the deposit largely formed epigenetically rather than as a synsedimentary deposit. The trace element composition of the apatite provides additional constraints on the geochemical evolution of the Silvermines hydrothermal system indicating that it was initiated with the expulsion of oxidizing fluids responsible for early hematite-silica precipitation. This was followed by the formation of hydrothermal dolostone breccias containing barite and the apatite dated here. The infiltration of metal-bearing hydrothermal fluids, likely derived from the basement, overlapped and followed the development of hydrothermal dolostone breccias, interacting with Carboniferous seawater during dolomitization and barite precipitation. Near-sea-floor biogenic activity, possibly enhanced due to escape of hydrothermal fluids, resulted in the reduction of seawater sulfate and formation of the sulfide-bearing fluids that facilitated the development of the Silvermines Zn-Pb deposit.

A comprehensive evaluation of the spatiotemporal variation of CO2 and its driving forces over China

With the improved accuracy and high spatiotemporal resolution, satellite remote sensing has provided an alternative way for monitoring the variations of CO2 in remote areas where field observations are inadequately sampled but the emissions of CO2 are increasing rapidly. Based on CO2 estimates from satellite remote sensing and the atmospheric tracer transport model, this study assessed the spatiotemporal patterns of atmospheric CO2 and its driving forces across China. Results show a consistent increase in CO2 at all levels of the troposphere, with the growth rate exceeding 2.1 ppm/year. Among them, the near surface witnessed obvious spatial heterogeneity with the highest concentrations of CO2 occurring in East China and the lowest in Northwest China. This strong spatial differentiation disappeared with increase in altitude and is replaced by a distinct south–north gradient difference at the upper troposphere. With regard to vertical variations, the concentration and growth rates of CO2 at the lower troposphere are generally higher than those at the upper troposphere. The driving mechanism analysis indicates that the variation of CO2 at the near surface is primarily caused by anthropogenic and biogenic activities, while air motion dominates the distribution of CO2 at the upper troposphere. The findings of the present study could provide a valuable reference for understanding regional carbon cycles and formulating carbon emission reduction strategies on a national scale.

The influence of bioturbation on reservoir quality: Insights from the Columbus Basin, offshore Trinidad

Nine facies are recognised in two mid-Pliocene cores from the Columbus Basin, offshore east coast Trinidad. Facies successions are consistent with deposition within a deltaic-shoreface continuum. Lower shoreface deposits are heavily bioturbated by Scolicia, Asterosoma, Thalassinoides, Teichichnus, Palaeophycus and other elements of the Cruziana Ichnofacies whereas middle shoreface sandstone beds contain sand-filled burrows of the Skolithos Ichnofacies. Deltaic deposits record coarsening-upward successions with evidence of freshwater influx such as synaeresis cracks, fluid muds, and dispersed organic detritus. Prodelta and distal delta front deposits comprise heterolithic beds and contain sporadically distributed and diminutive structures belonging to the Phycosiphon Ichnofacies. Hummocky cross-stratification is prominent in storm-dominated proximal delta front sandstone deposits that are sparsely bioturbated by Ophiomorpha, Skolithos and other elements of the Rosselia Ichnofacies. Cryptic bioturbation is common at the top of these beds. Thin section examination, core plug analysis, and numerical modelling of the facies were undertaken to better understand fluid flow in bioturbated strata of the Columbus Basin. Whereas lithology and texture remain the primary control on reservoir quality, examples of biogenically enhanced permeability are present in the P3 and P7 cores. The highest permeability values are associated with highly bioturbated middle shoreface deposits that comprise clean, sand-filled burrows. Favourable permeability measurements are also attributed to cryptically bioturbated delta front sandstone beds. The latter display higher permeabilities when compared to unbioturbated and sparsely sandstone beds. Biogenic activity contributed to reduced permeabilities in lower shoreface and distal delta front deposits owing to extensive sediment packing and sediment mixing behaviours. Relationships between permeability and bioturbation intensity indicate that effective permeability in bioturbated intervals of the P3 and P7 cores are best characterised by the arithmetic mean of permeabilities and that simple statistical calculations can aid in the analysis of highly bioturbated facies (BI = 5–6).

Hygroscopicity and CCN Activity of Water‐Soluble Extracts From the Arctic Aerosols in Winter to Early Summer

AbstractThe hygroscopicity and cloud condensation nuclei (CCN) activity of water‐soluble extracts from Arctic lower tropospheric aerosols during winter to summer were investigated under sub‐ and super‐saturated conditions, with chemical composition and air mass origin. The κ values from the hygroscopic growth factor at 80%–90% relative humidity (κHTDMA) during winter, spring, and summer were 0.34 ± 0.06, 0.41 ± 0.05, and 0.25 ± 0.02, respectively, whereas those derived from CCN activation diameter at 0.29%–0.59% supersaturation (κCCNC) were 0.42 ± 0.03, 0.43 ± 0.05, and 0.34 ± 0.11, respectively. The hygroscopicity and CCN activity showed clear seasonal variations following changes in composition that are linked to natural, anthropogenic, and biogenic sources. During winter and spring, κ was high when highly hygroscopic components such as sea salts, sulfate, and highly‐oxidized/aged particles were dominant due to long‐range atmospheric transport and photochemical reactions. In contrast, κ was significantly lower in summer when water‐insoluble (22%) and water‐soluble organic matter (OM) (17%) were dominated with high biogenic activity associated with ice‐edge zones. The κCCNC and κHTDMA values agreed well within 8% and the surface tension agreed with that of pure water within 10%. The κ for OM (κOM) estimated from chemical composition during spring and summer was on average 0.04 ± 0.06 (up to ∼0.17). This result suggests that highly hygroscopic components such as sea salt and sulfate mainly controlled particle hygroscopicity and CCN activity in winter, but water‐soluble OM could also contribute in spring and summer.

High temperature susceptibility measurements: A potential tool for the identification of oil-water transition zone in petroleum reservoirs

Determining the position and thickness of the oil-water transition zone (OWTZ) in hydrocarbon reservoirs is important to reserve estimation and production planning. This paper describes a magnetic method of identifying this zone. High temperature susceptibility (HT-χ) measurements on core samples from Paleogene reservoirs of the UK Central North Sea revealed distinct signatures around the oil water interface. Rapid increases in susceptibilities at temperatures &amp;lt;250°C were observed for samples around the oil water interface unlike the main oil leg where alteration involving increase in susceptibility occurred at significantly slower rates and higher temperatures. The HT-χ data together with Mössbauer measurements revealed that the variation in alteration characteristics is due to the increasing concentration of hexagonal pyrrhotite and/or lepidocrocite around the oil water interface. Hexagonal pyrrhotite was identified in reservoirs existing at temperatures of &amp;lt;80°C, while lepidocrocite dominated the signature around the contact of deeper reservoirs. These observations suggest that the precipitation of hexagonal pyrrhotite is related to OWTZ centred biogenic activities i.e., biodegradation. The dominance of lepidocrocite in deeper diagenetic settings has been related to hydrolysis of hydrocarbon at the oil water interface, together with cessation of biogenic activities.

MICROFACIES OF LATE PLEISTOCENE TRAVERTINE DEPOSITS IN JORDAN

The Late Pleistocene travertine outcrops from Deir Alla, Suwayma, and Az Zara were investigated, and their microfacies were identified. The microfacies of the Deir Alla travertines include micrite and spar groundmass, shrubs, crystalline crusts, a stromatolite-like structure, peloids, and cements. Shrub travertine includes spar calcite-coated stems with probably microbial micritic clumps. The crystalline crust travertine displays an alternation of micrite and sparite laminae. The micritic laminae are dark-coloured. Bundles of radial spar crystals are associated locally with micritic groundmass. The crystalline crust developed where biogenic activity is limited. Peloidal microfacies are less than 0.25 mm in diameter, cryptocrystalline, pale-dark green in colour, elliptical to spherical in shape, and usually associated with microorganisms. The microfacies of the Suwayma and Az Zara travertines include crystalline calcite rhombs and other composite scalenohedral crystals. They occur as small anhedral-subhedral crystals, monocrystalline to some polycrystalline, corroded, subrounded, and mainly coated with iron oxide and/or clay minerals. Peloids, ooids, and oncoids are common. They are dark-green coloured, cryptocrystalline to microcrystalline carbonates of spherical and ellipsoidal shape with less than 1 mm in diameter. Rich flora travertines include reed and paper-thin rafts with leaf impressions encrusted on moss cushions. The flora observed in the upper part of the Suwayma section was identified as charophyte oospores (gyrogonites). A few grains of quartz are present as small subhedral-euhedral crystals, monocrystalline, corroded, rounded, and mainly coated with iron oxide. The iron is irregularly distributed among the laminae and voids and is occasionally replaced by carbonates. The described macrophyte encrustation structures probably represent algae, cyanobacteria, or bryophytes. All samples of micrite and spar calcite appear as groundmass.

Sources of PM2.5-Associated PAHs and n-alkanes in Changzhou China

Polycyclic aromatic hydrocarbons (PAHs) and n-alkanes are important specific organic constituents in fine particulate matter (PM2.5). Seventy-five PM2.5 samples were collected in Spring Changzhou, to investigate the concentrations and sources of n-alkanes (C9–C40) and PAHs. The average concentrations of total PAHs (∑PAHs) and n-alkanes (∑n-alkanes) were 4.37 ± 4.95 ng/m3 and 252.37 ± 184.02 ng/m3, ranging from 0.43 to 22.22 ng/m3 and 57.37 to 972.17 ng/m3, respectively. The average concentrations of ∑n-alkanes and ∑PAHs were higher in severely polluted days (PM2.5 ≥ 150 μg/m3) in comparison to other days. Up to 85% of PAHs were four- and five-ring compounds, and the middle-chain-length n-alkanes (C25–C35) were the most abundant species (80.9%). The molecular distribution of n-alkanes was characterized by odd-number carbon predominance (carbon preference index, CPI &gt; 1), with a maximum centered at C27, C29, and C31 revealing a significant role of biogenic sources. Principal component analysis suggested that the biogenic sources that contributed the most to n-alkanes and PAHs were from coal combustion (46.3%), followed by biomass burning (16.0%), and vehicular exhaust (10.3%). The variation in the concentration of n-alkanes and PAHs from different air mass transports was not agreement with the change in PM2.5 mass, indicating that regional transport had important impacts on the characterization of PM2.5. The results of our study can provide useful information for evaluating the influence of anthropogenic and biogenic activities on organic matters (n-alkanes and PAHs).