Search Results (169)

The new LOAC2 optical aerosol counter is designed to detect liquid and solid particulates across 19 to 30 size classes within the 0.15–90 µm size range, and to provide their main typology. The instrument can be used at ground level and on all kinds of balloons, including weather balloons, up to an altitude of about 35 km. The measurements are based on principles established for the previous version of LOAC, now incorporating improved electronics and detection geometry. Counting is performed at small scattering angles in the diffraction domain, making it insensitive to the refractive indices and the porosity of the particles, thus allowing a direct relationship between scattered intensity and aerosol size. Typology identification is now performed at three additional scattering angles, where the scattered flux is highly sensitive to the refractive index of the different aerosol families present in the atmosphere. The calibration was conducted using calibrated spherical and irregular grains, as well as different types of solid particles. Several intercomparison sessions with other counters and with reference mass-concentration air quality monitoring stations were carried out indoors, in an atmospheric simulation chamber, and in outdoor ambient air. The agreement between LOAC2 and the other instruments is good, confirming the ability of LOAC2 to be used for scientific studies and for monitoring atmospheric aerosols. Full article

Organic matter production, recycling, and burial processes temporally fluctuate across the Clarion-Clipperton Zone (CCZ) in the Eastern Tropical Pacific. Between 2019 and 2022, we conducted pelagic and benthic surveys in Nauru Ocean Research Inc. contract area D (NORI-D) in the southeast CCZ to establish environmental baseline conditions. Here, we synthetise the natural ranges of variability in physicochemical and biogeochemical processes in NORI-D across multiple surveys and years. We present interannual water column physicochemical characteristics from five metocean and pelagic campaigns, annual satellite-derived net primary productivity and export production, time-integrated sediment trap annual particulate organic carbon flux, and seafloor biogeochemical and sediment physical characteristics from three benthic campaigns. Temperature and salinity seasonally varied at the sea surface. Strong thermohaline and oxygen stratification developed over 0–100 m. Mean net primary productivity, export production, and seafloor particulate organic carbon flux amounted to 634.1, 15.7, and 2.1 mg C m⁻² d⁻¹, respectively. These rates fluctuated nearly four-fold seasonally and interannually. An oxygen minimum zone (100–700 m) dampened organic carbon flux attenuation (b = −0.538) to the abyss. Abyssal seafloor organic matter dynamics showed more homogenous conditions in 2020–2021 (TOC = 0.57 ± 0.05%) than in 2022 (TOC = 0.42 ± 0.19%). Bioturbation rate and mixed-layer depth decreased from 2020 to 2022, while oxygen consumption increased at 0–1 cm bsf. Lipid consumption and compositional alteration in 2022 surpassed 2020–2021. Our findings provide critical baseline data to inform environmental impact assessments and monitoring programmes for deep-sea mining of polymetallic nodules in NORI-D. Full article

Microzooplankton grazing is a key regulator of phytoplankton standing stock and the export of particulate organic carbon (POC) in the ocean, yet its spatial coupling with phytoplankton growth across shelf-basin gradients remains underexplored in marginal seas. Using 43 dilution experiments in the South China Sea (SCS), this study systematically examined the spatial variability and environmental drivers of phytoplankton growth rate (μ) and grazing mortality rate (m) as well as the resulting grazing impact (m/μ) across shelf, slope, and basin habitats. Results show a significant seaward decline in m (shelf: 0.73 ± 0.53 d⁻¹; basin: 0.27 ± 0.19 d⁻¹; p < 0.01), while μ decreased non significantly (shelf: 0.88 ± 0.53 d⁻¹; basin: 0.70 ± 0.18 d⁻¹; p = 0.49). Consequently, growth and grazing were strongly coupled on the shelf (r = 0.82, p < 0.01) but completely decoupled in the basin (r = 0.21, p = 0.46), coinciding with a shift toward picophytoplankton dominance and reduced grazing pressure. We also found that export efficiency was positively correlated with both m/μ and m, highlighting the important role of microzooplankton grazing in carbon export, but that the overall carbon export flux itself was also shaped by nutrient-driven changes in POC recycling. These findings underscore the role of bottom-up nutrient forcing and top-down grazing impact in controlling carbon export in the SCS. Full article

During wet deposition, particulate matter and gaseous species in the atmosphere are ultimately transported to the Earth’s surface via precipitation and subsequently incorporated into terrestrial ecosystems. Therefore, investigating the fluxes, chemical compositions, and source apportionment of regional wet deposition is of great scientific importance. An analysis of the concentrations, deposition fluxes, spatiotemporal variations, and source apportionment of water-soluble ions in wet deposition can further enhance our understanding of the water-soluble ion characteristics, atmospheric pollution profiles, and potential ecosystem impacts of wet deposition in the Yangtze River Delta and Pearl River Delta regions. Coastal cities in China are most developed regions, and also areas suffering from severe air pollution. This study investigates the chemical characteristics, sources and wet deposition fluxes of water-soluble inorganic ions in precipitation in two typical coastal urban agglomerations of China: Ningbo in the Yangtze River Delta and Guangzhou in the Pearl River Delta. Precipitation samples were collected and analyzed to determine the concentrations of major ions. The results revealed distinct ionic compositions between the two regions. In Ningbo, NO₃⁻ and SO₄²⁻ were the predominant ions accounting for 16.98% to 23.22% of the total, reflecting the influence of anthropogenic emissions from fossil fuel combustion and mobile sources with the NO₃⁻/SO₄²⁻ ratio of 0.90 and 0.70. In Guangzhou, precipitation was characterized by high contributions of SO₄²⁻, NO₃⁻, NH₄⁺, and Ca²⁺, accounting for 17.22% to 23.29% of the total, indicating a mixed influence of industrial emissions, agricultural activities, and construction dust with the NO₃⁻/SO₄²⁻ ratio of 0.92 and 0.87. A clear inverse relationship between rainfall amount and ion concentration was observed at all sites (p < 0.05), demonstrating a significant dilution effect. Seasonality played a crucial role in deposition fluxes. In Ningbo, fluxes peaked during summer from 4667 to 5156 mg·m⁻², while in Guangzhou, distinct dry and rainy season patterns influenced the scavenging efficiency of different ion species. Urban sites exhibited enhanced scavenging of crustal and anthropogenic ions (e.g., Ca²⁺, NH₄⁺) during the rainy season, whereas the coastal site showed elevated fluxes of marine-derived ions (Na⁺, Cl⁻, Mg²⁺, SO₄²⁻) during the same period. The observed trends in ion fluxes suggest a gradual improvement in regional air quality over the study period. These findings elucidate the complex interactions between anthropogenic activities, natural sources, and meteorological factors in shaping the wet deposition chemistry in coastal urban environments, providing essential data for developing regional deposition models and assessing the ecological impacts of atmospheric pollution. Full article

This study investigates long-term wildfire emissions and smoke-plume geospatial characteristics in Greece by analyzing a multi-pollutant dataset spanning January 2003 to August 2025. Details of emissions of carbon monoxide (CO), carbon dioxide (CO₂), methane (CH₄), particulate matter (PM_2.5), organic carbon (OC), and black carbon (BC) were derived from the Global Fire Assimilation System (GFAS), which converts MODIS fire radiative power into trace gas and aerosol fluxes at 0.1° resolution, and also accounts for the land type. Burned-area statistics from the European Forest Fire Information System (EFFIS) were used for cross-validation. Data were processed into daily, monthly, annual, and cumulative time series, with spatial mapping at the municipality scale and information regarding long-term trends. The analysis shows that while there are several sizeable wildfire events in the country every year, the bulk of the total of Greek wildfire emissions for the last 23 years is attributable to a few extreme fire seasons (2007, 2021, and 2023) that produced abrupt emission surges and accounted for a disproportionate share of national totals. Analysis of spatial data identifies the areas of Evia, East Attica, Messinia, and Evros as persistent emission hotspots. Although wildfire CO₂ emissions are generally a minor fraction of Greece’s anthropogenic totals (<5%), they reached 15–17% during peak fire years. Plume-injection height analysis reveals that most smoke remains below ~1 km but can reach 3–6 km during extreme events, facilitating long-range transport. Overall, the dataset demonstrates a shift toward more intense and concentrated wildfire events in recent years, highlighting both their growing climatic relevance and their acute impacts on regional air quality. Full article

This study investigated sub-basin variability in dissolved (dBa)–excess particulate (Ba_xs) barium relationships and Ba flux patterns across the western and central Mediterranean Sea during late spring 2017 (PEACETIME cruise). The dBa concentrations increased from ~35 nmol L⁻¹ near the surface to ~70 nmol L⁻¹ at 2500 m, consistent with the relatively weak vertical dBa gradient typical of the Mediterranean. Depth profiles of dBa showed distributions consistent with Ba_xs dynamics associated with organic matter remineralization at mesopelagic depths (100–1000 m). Ba_xs exhibited basin-dependent maxima, with lower (<300 pM) depth-weighted average concentrations confined to the upper mesopelagic in the Tyrrhenian and Ionian basins and higher (up to 650 pM) and deeper concentrations (to ~1000 m) in the Algero–Provençal basin, suggesting contrasted remineralization horizon structures. A simplified steady-state 1-D approach yielded first-order mesopelagic dBa removal fluxes of ~0.3 ± 0.1 µmol m⁻² d⁻¹ in the Algero–Provençal basin to 1.7 ± 1.0 µmol m⁻² d⁻¹ in the Ionian basin, consistent with previous estimates obtained from a coupled dBa and parametric optimum multiparameter approach. Together, these paired dissolved and particulate Ba observations refined the Mediterranean Ba cycle framework and provided additional geochemical constraints for interpreting mesopelagic carbon remineralization processes. Full article

In rural areas affected by Chernobyl, accelerated erosion has become a major source of particulate ¹³⁷Cs in sediment load. The long-term dynamics of the activity concentration in eroded soil material transported from individual slope catchments can be better understood by exploring the ¹³⁷Cs depth distribution in sediments deposited near cultivated fields. This study focuses on three cultivated slope catchments located in the Chernobyl-affected area of Central Russia. A depth incremental campaign was conducted within zones of sediment accumulation in 2022–2025. The behavior of radiocaesium associated with particles after the Chernobyl accident was controlled by the prompt implementation of remediation measures. Shortly after the accident, the values decreased by more than two times. The radionuclide flux then began to depend on soil erosion processes. Gradually, the thickness of the upper soil that had been eroded became large enough to allow soil material from deeper layers to be involved during ordinary plowing and led to a subsequent decrease in the ¹³⁷Cs activity concentration. Given the decreasing snowmelt runoff and lack of increase in high-intensity rainfall in the 21st century, the activity concentration of ¹³⁷Cs in slope runoff has remained quite stable. This phenomenon requires consideration of whether a physically based model for the transport of particulate radionuclides should be developed. Full article

This study develops and validates the Saharan Dust Flux and Transport Index (SDFTI) using a 22-year dataset (2003–2024) of dust-related and dynamical variables across the Mediterranean. The index integrates six components (surface-particulate matter, satellite-derived desert-dust optical depth, free-tropospheric dust mass, transport score, North-Atlantic Oscillation and Oceanic Niño Indices) combined through a physically calibrated weighting scheme. To assess the stability of the formulation, three alternative variants are constructed (dust-enhanced, dynamics-enhanced, and equal-weight) and evaluated across four Mediterranean sub-regions using seasonal means, inter-annual anomalies, component correlations, and extreme-event detection. The results show that the SDFTI is highly robust over the full 2003–2024 period. Across all regions, the calibrated variants reproduce nearly identical seasonal cycles (e.g., spring–summer peaks of +0.53 to +0.58 in Western Mediterranean), identify the same dusty and non-dusty years (2008–2012 minima, 2021–2022 maxima), and capture the same major dust outbreaks (e.g., March 2022, June 2021). SDFTI consistently provides the most balanced representation of dust-mass loading and transport dynamics, while the equal-weight variant diverges as expected due to its lack of physical calibration. Overall, the SDFTI offers a stable and regionally coherent measure of Saharan dust transport. The methodological framework (variable selection, normalisation, weighting, and sensitivity testing) is general and can be adapted to other dust-affected regions worldwide. Full article

Carbon fluxes from the atmosphere to the ocean and from the ocean surface to the deep ocean are a key pathway in the long-term sequestration of anthropogenic CO₂. Particulate Organic Carbon (POC), which comprises living plankton, detritus and other microscopic organisms, is a very dynamic carbon pool in surface waters, so an ability to assess POC reliably from satellites and autonomous profilers is fundamental to the quantification of the reservoirs and fluxes of carbon within the ocean, and to assess their response to climate change. In situ records from sample filtration during dedicated hydrographic surveys are limited both in terms of spatial coverage and time, so reliable algorithms are required that make use of readily available autonomously collected data that provide much better spatial and temporal coverage. In this paper, algorithms that use ocean colour data from satellites to estimate POC are re-assessed, and then the satellite-derived products are compared with near-surface in situ observations from biogeochemical (BGC) Argo profilers. The satellites and in situ BGC-Argo records match each other to within 30%, but a regional bias persists that may be related to the BGC-Argo fluorometers overestimating the chlorophyll concentration in the Southern Ocean. A simple coarse-resolution regional correction to the observed chlorophyll-a concentration and backscatter coefficient, plus the removal of clear outliers, improves the agreement to approximately 15%. The association of POC with the surface chlorophyll value is so strong that an algorithm based on chlorophyll-a alone provides an almost equally good estimate of POC compared with more complex algorithms that incorporate additional bio-optical variables such as the backscattering coefficient. Full article

The coupling of physical transport and phase-transfer processes represents a fundamental mechanism governing metal cycling in estuarine systems under tidal oscillations. Taking Quanzhou Bay as a model system, we conducted continuous observations and sample collection at the river channel (Q1), the turbidity maximum zone (Q2), and the outer bay channel (Q3). The metals (Al, Ti, Ba, Cu, Mn, and Zn) were measured by ICP-MS to systematically investigate the distribution, transport, and inter-media transfer across multiple water layers under varying estuarine processes. Our findings demonstrate that particulate metal concentrations in Quanzhou Bay exhibit strong synchrony with suspended sediment concentrations (SSC) over tidal cycles, displaying a distinct sediment-following pattern controlled by alternating end members. Particulate metal fluxes during flood and ebb-tides generally followed the hierarchy Q1 > Q2 >> Q3. Notably, stations Q1 and Q2 were dominated by flood-tide fluxes with net transport directed landward, whereas Q3 was characterized by ebb tide dominance with net flux directed seaward—revealing a spatial division of labor between “inner bay retention/reallocation” and “outer bay channel export”. In contrast, dissolved metals exhibited marked element-specific responses to tidal forcing: Al and Ti increased during flood tides at stations Q1 and Q2, while Ba and Cu showed opposite trends, and Mn and Zn displayed more conservative behavior. Concurrently, solid/liquid partition coefficient (logKd) values for Al, Ti and Ba, Cu exhibited inverse patterns over tidal cycles, suggesting divergent adsorption–desorption regulation under identical hydrodynamic conditions that drives differential phase-transfer dynamics. These disparities likely reflect intrinsic chemical properties and source variations among the elements. This study elucidates, at the tidal timescale, the coupled processes of “alternating end-member control—estuarine filter modulation—concurrent channelized export and inner bay retention” in Quanzhou Bay, providing critical process-level insights for metal flux quantification and bay pollution remediation initiatives in an ecological restoration project. Full article

Aerosol dry deposition is an important sink for particulate matter and a source of uncertainty in air quality modeling. Using the Weather Research and Forecasting model coupled with CUACE (WRF-CUACE), we quantified how three aerosol dry deposition schemes and satellite-based leaf area index (LAI) information affected PM_2.5 dry removal and near-surface PM_2.5 over central and eastern China in January 2022. The schemes were abbreviated as Z01, E20, and PZ10, respectively. A fourth simulation (PZ10_MLAI) used PZ10 but replaced the baseline LAI dataset with a Moderate Resolution Imaging Spectroradiometer (MODIS) constrained LAI field. Hourly PM_2.5 was evaluated with the China National Environmental Monitoring Center network. The schemes produced pronounced, size-dependent differences in deposition velocities, with a pronounced spread in the 0 to 2.5 µm average and more than one order of magnitude spread in the accumulation mode diagnostic, leading to distinct regional mean PM_2.5 dry deposition fluxes. The mean PM_2.5 flux increased by 5.9% in E20 relative to Z01 and decreased by 54.4% in PZ10. The MODIS LAI adjustment changed the PZ10 mean flux by 0.42%. The flux contrasts yielded coherent PM_2.5 responses, with E20 reducing near-surface concentrations by about 10 to 30% and PZ10 increasing them by about 20 to 60%, reaching about 80 to 100% in parts of southern China. Domain mean correlations ranged from 0.61 to 0.65 and PZ10-based simulations exhibited near-zero mean bias. Although MODIS LAI effects were modest for this winter month, local PM_2.5 differences commonly remained within about 4% and approached 6 to 10%, indicating that satellite LAI constraints can be important for multi-year and decadal applications. Full article

Forest canopies effectively remove airborne particles, reducing the frequency of atmospheric haze and improving air quality as well as playing a crucial role in maintaining human health. In this study, we examined the retention of particulate matter by Picea crassifolia Kom. (P. crassifolia) needles using an aerosol regenerator in two typical catchments, while the concentrations of dissolved trace elements (Na, Zn, Pb, and Cd) were determined only in the Tianlaochi catchment. The results showed that the retention of airborne particles was lower in the Tianlaochi catchment (e.g., total suspended particles (TSP): 0.0049 μg cm⁻² in summer) than in the Sancha catchment (e.g., TSP: 0.0145 μg cm⁻²) in summer and autumn, while the opposite trend was found in winter and spring, with Tianlaochi catchment reaching higher TSP levels (0.0230 μg cm⁻² in spring) compared to Sancha catchment (0.0205 μg cm⁻²). The big tree exhibited the highest particulate retention, with a maximum flux of 84.870 μg cm⁻², indicating it was the most effective at particle trapping. The highest Na, Zn, Cd, and Pb values absorbed by the needle samples were 1.794 mg L⁻¹, 11.345 μg L⁻¹, 0.081 μg L⁻¹, and 4.316 μg L⁻¹, respectively. P. crassifolia needles absorbed more Na, Zn, and Cd in July and August than in June. The absorption capacity of the needles decreased in the order Na > Zn > Pb > Cd. P. crassifolia forest can effectively reduce airborne particulate matter. Our study provides a theoretical foundation to examine the role of forest ecosystems in the retention of atmospheric particulate matter in the Qilian Mountains region. Full article

Using MODIS-Aqua satellite observations, this study analyzes the spatiotemporal distribution characteristics of particulate organic carbon (POC) in China’s marginal seas from 2003 to 2024. The statistical relationships between various marine environmental variables, including sea surface temperature (SST), nutrients, and primary production (PP), and POC concentrations are explored using partial least squares path modeling (PLS-PM). Finally, a box model approach is conducted to assess the POC budget in the study area. The results indicate that the POC concentration in the marginal seas of China generally exhibits a characteristic of being high in spring and low in summer. The highest concentration of POC is observed in the Bohai Sea, followed by the Yellow Sea, and the lowest in the East China Sea, with coastal waters exhibiting higher POC concentrations compared to the central areas. The spatial distribution and seasonal changes in POC are jointly influenced by PP, water mass exchange, resuspended sediments, and terrestrial inputs. Large-scale climate modes show statistical associations with POC concentration in the open waters of China’s marginal seas. PP and respiratory consumption are identified as the predominant input and output fluxes, respectively, in China’s marginal seas. This study enriches the understanding of carbon cycling processes and carbon sink mechanisms in marginal seas. Full article

During the 71st cruise of the R/V Akademik Oparin in the summer of 2024, we assessed the distributions of dissolved and particulate forms of ²¹⁰Pb and ²¹⁰Po in the Sea of Japan, the Sea of Okhotsk, and the northwestern Pacific Ocean. Quantitative estimates of vertical fluxes were derived based on measured concentrations of suspended particulate matter (SPM) and particulate organic carbon (POC). This study provides the first in situ measurements of these radionuclides and the first estimates of derived fluxes for the Sea of Okhotsk. The study confirmed the existence of two contrasting biogeochemical regimes: a sedimentation regime in the productive waters of the Sea of Okhotsk and a recycling regime in the oligotrophic waters of the open ocean, separated by the dynamic transition zone of the Kuril Islands. The calculated POC fluxes confirmed the high efficiency of the biological pump in the coastal seas. The identified anomalies in the distribution of radionuclides indicate a significant role of lateral transport and the sorption of organic carbon onto mineral particles in shaping vertical fluxes matter. Full article

Wildfires are a major source of greenhouse gases (GHGs), particulate matter (PM), and atmospheric pollutants, exerting widespread impacts on air quality, human health, and global climate. To address knowledge gaps, this study conducts a literature review of GHG emissions from wildfires across diverse ecosystems and fire regimes. The analysis quantifies emission magnitudes and compositions, evaluates their influence on regional and global climate processes, and synthesizes trends and methodological advances. Results show that the burned area is the main determinant of total emissions, with CO₂ as a robust predictor for estimated CO and CH₄, reflecting coupled emission behavior under varying combustion conditions. The Modified Combustion Efficiency (MCE) demonstrates a stronger predictive capacity for the CO/CO₂ ratio than for CH₄/CO₂, suggesting that CO/CO₂ can be predicted from MCE. Complete combustion dominates most fire events, while incomplete combustion increases the release of CO, CH₄, N₂O, and PM, contributing to tropospheric ozone formation and enhanced radiative forcing. Exposure to PM_2.5 and ozone remains a major health concern in fire-affected regions. This review provides a quantitative synthesis linking combustion efficiency and GHG co-variability, offering insights to refine emission modeling and guide climate mitigation strategies. Full article