The unique distribution pattern of PFAS in landfill organics.

PFAS from degrading landfill waste partition into organic matter, leachate, and landfill gas. Driven by the limited understanding of PFAS distribution in landfill organics, we analyzed PFAS across various depths and seven spatially distinct locations within a municipal landfill. The measured PFAS concentrations in organics ranged from 6.71 to 73.06 µg kg-1, a sum of twenty-nine PFAS from six classes. Perfluorocarboxylic acids (PFCAs) and fluorotelomer carboxylic acids (FTCAs) were the dominant classes, constituting 25-82 % and 8-40 % of total PFAS at different depths. PFBA was the most dominant PFCA with a concentration range of 0.90-37.91 µg kg-1, while 5:3 FTCA was the most prevalent FTCA with a concentration of 0.26-17.99 µg kg-1. A clear vertical distribution of PFAS was observed, with significantly greater PFAS concentrations at the middle depths (20-35 ft), compared to the shallow (10-20 ft) and high depths (35-50 ft). A strong positive correlation (r > 0.50) was noted between total PFAS, total carbon, and dissolved organic matter in landfill organics. Multivariate statistical analysis inferred common sources and transformations of PFAS within the landfill. This study underscores the importance of a system-level analysis of PFAS fate in landfills, considering waste variability, chemical properties, release mechanisms, and PFAS transformations.

Metagenomic Insights into Ecophysiology of Zetaproteobacteria and Gammaproteobacteria in Shallow Zones within Deep-sea Massive Sulfide Deposits.

Deep-sea massive sulfide deposits serve as energy sources for chemosynthetic ecosystems in dark, cold environments even after hydrothermal activity ceases. However, the vertical distribution of microbial communities within sulfide deposits along their depth from the seafloor as well as their ecological roles remain unclear. We herein conducted a culture-independent metagenomic ana-lysis of a core sample of massive sulfide deposits collected in a hydrothermally inactive field of the Southern Mariana Trough, Western Pacific, by drilling (sample depth: 0.52| |m below the seafloor). Based on the gene context of the metagenome-assembled genomes (MAGs) obtained, we showed the metabolic potential of as-yet-uncultivated microorganisms, particularly those unique to the shallow zone rich in iron hydroxides. Some members of Gammaproteobacteria have potential for the oxidation of reduced sulfur species (such as sulfide and thiosulfate) to sulfate coupled to nitrate reduction to ammonia and carbon fixation via the Calvin-Benson-Bassham (CBB) cycle, as the primary producers. The Zetaproteobacteria member has potential for iron oxidation coupled with microaerobic respiration. A comparative ana-lysis with previously reported metagenomes from deeper zones (~2| |m below the seafloor) of massive sulfide deposits revealed a difference in the relative abundance of each putative primary producer between the shallow and deep zones. Our results expand knowledge on the ecological potential of uncultivated microorganisms in deep-sea massive sulfide deposits and provide insights into the vertical distribution patterns of chemosynthetic ecosystems.

Microbial carbon metabolism patterns of microplastic biofilm in the vertical profile of urban rivers.

Microplastics (MPs) can provide a unique niche for microbiota in waters, thus regulating the nutrients and carbon cycling. Following the vertical transport of MPs in waters, the compositions of attached biofilm may be dramatically changed. However, few studies have focused on the related ecological function response, including the carbon metabolism. In this study, we investigated the microbial carbon metabolism patterns of attached biofilm on different MPs in the vertical profile of urban rivers. The results showed that the carbon metabolism capacity of biofilm on the degradable polylactic acid (PLA) MPs was higher than that in the non-degradable polyethylene terephthalate (PET) MPs. In the vertical profile, the carbon metabolism rates of biofilm on two MPs both decreased with water depth, being 0.74 and 0.91 folds in bottom waters of that in surface waters. Specifically, the utilization of polymers, carbohydrate, and amine of PLA biofilm was significantly inhibited in the bottom waters, which were not altered on the PET. Compared with surface waters, the microbial metabolism function index of PLA biofilm was inhibited in deep waters, but elevated in the PET biofilm. In addition, the water quality parameters (e.g., nutrients) in the vertical profile largely shaped carbon metabolism patterns. These findings highlight the distinct carbon metabolism patterns in aquatic environments in the vertical profile, providing new insights into the effects of MPs on global carbon cycle.

Spatial distribution of microplastics in the Gulf of Cadiz as a function of their density: A Lagrangian modelling approach.

Microplastics (MPs) are distributed throughout the world oceans and represent one of the greatest environmental concerns of marine pollution. In the Gulf of Cadiz (GoC), MPs are found throughout the water column, on the seafloor, and accumulated within commercial marine species, primarily due to discharges from the main estuaries. The aim of this study was to analyse the transport pathways, spatial distribution, and accumulation regions of MPs in the GoC based on their density and source. For this, a Lagrangian transport model was coupled to a high-resolution hydrodynamic model and four particle sources were considered: Cape San Vicente, Guadiana Estuary, Guadalquivir Estuary, and Bay of Cadiz/Guadalete River. To account for the diversity of plastics detected in the GoC, particles with ten different densities were used, from low-density to high-density polymers. This study indicates that a significant proportion of low-density MPs accumulate near their sources and within the top few centimetres of the water column due to local surface currents. The Guadalquivir and Guadiana estuaries are the primary contributors to the high accumulation of low-density MPs on the GoC eastern shelf, consistent with previous field studies identifying these estuaries as the main sources of MPs into the region, including polyethylene and polypropylene. In contrast, the Bay of Cadiz/Guadalete River seems to be the primary source of low-density MPs in offshore waters within the uppermost meter of the water column, influenced by local mesoscale features. The Guadalquivir Estuary seems to be the main source of high-density MPs into the continental shelves, such as polystyrene, polyamide, and polyvinyl chloride, followed by the Bay of Cadiz/Guadalete River, and to a lesser extent, the Guadiana estuary. These MPs accumulate near their sources at depths of 3.5 to 50 m due to their high sinking rates, but can also be transported offshore by deep currents, either northwards along the Portuguese offshore waters or westwards off the GoC offshore region.

In-situ aircraft observations of aerosol and cloud microphysical characteristics of mixed-phase clouds over the North China Plain.

Aerosol-cloud interactions play a vital role in climate change. This study leverages observations from the King-350 aircraft over the North China Plain on November 29, 2019, to examine aerosol and cloud microphysical characteristics of mixed-phase clouds. Through detailed vertical and spectral distributions, we investigate aerosol, cloud droplet, and ice crystal distributions in seeded clouds (SC) and natural precipitating clouds (NPC) within the same cloud system. From the vertical profile, SC and NPC have similar vertical distributions of aerosol and cloud droplets, with over 95 % of aerosols concentrated below 1600 m near the ground. Cloud droplets are more evenly distributed within the two clouds, cloud droplet number concentrations (Nc) in SC were three orders of magnitude higher than in NPC. Ice water content (IWC) and ice crystal number concentration (Ni) show distinct layer preferences-accumulating predominantly in SC's top layer and NPC's middle layer. From spectral distribution, a smaller proportion of cloud droplets (40-50 µm in diameter, the same hereafter) in SC compared to NPC. Rimed ice crystals and globular graupel (1325-1550 µm in diameter) were in SC, while plate and irregular ice crystals (300-450 µm) were in NPC with an order of magnitude higher than in SC. These microphysical differences highlight the complexity of cloud seeding efficacy, which varies based on cloud conditions and microphysical properties. In the first seeding, Ni increased by 1-2 orders of magnitude (125-300 µm) in the high Nc (Nc > 1.11 × 105 L-1) region. Seeding in low Nc (Nc < 1.11 × 105 L-1) regions was hard to be effective, especially in low Nc and low liquid water content (LWC) (LWC < 0.122 g/m3) regions. In the second seeding, ice crystals (125-250 µm) produced by the first seeding enhance the seeding efficiency. The responded regions were more sensitive to subsequent seeding, resulting in stronger reactions or longer duration.

Microplastic volumes in Tokyo Bay.

Microplastic (MP) pollution is a rising environmental concern. This study investigated MP concentrations in Tokyo Bay using neuston net for surface sampling and deep-sea plankton pump for underwater sampling across six stations at multiple depths. Results revealed substantial variation in MP concentrations. Surface large microplastics (LMP, > 350 µm) ranged from 0.21 × 10-3 to 3.34 × 10-3 pieces L-1, averaging 1.26 × 10-3 pieces L-1, while surface small microplastics (SMP, 60 µm to 350 µm) were highest at head of the bay (11.5 ± 3.05 pieces L-1). SMP concentrations varied with depth and position, peaking at center of the bay (5.79 ± 1.63 pieces L-1 at 2 m). Additionally, the total amount of surface LMP was estimated at 10.3 m3 and SMP at 15.0 m3 in the Tokyo Bay. This study provides a comprehensive picture of the spatial and vertical distribution of MP in Tokyo Bay.

Changes of vertical distribution of Microcystis colonies driven by short-term rainfall: Disappearance and reformation of surface bloom.

Global climate warming and human activities have increased the magnitude and frequency of Microcystis surface blooms, posing significant threats to freshwater ecosystems and human health over recent decades. Heavy rainfall events have been reported to cause the disappearance of these blooms. Although some studies have employed turbulence models to analyze the movement characteristics of Microcystis colonies, the impact of rainfall is complex, comprehensive investigations on their vertical migration induced by short-term rainfall are still necessary. Utilizing monitoring data from eutrophic ponds and controlled simulation experiments, this study examines the short-term impacts of rainfall on the vertical distribution of Microcystis in the water column. Our findings indicate that rainfall contributes to the disappearance of Microcystis blooms by reducing the quantity of small to medium-sized colonies (0-100 µm) at the surface, subsequently decreasing the overall Microcystis biomass. As rainfall intensity increases, larger colonies migrate deeper into the water column. At a rainfall threshold of 666 mm, the difference in the median volume diameter (DV50) of Microcystis colonies between the surface and bottom reaches a minimal value of 3.09%. Post-rainfall, these colonies rapidly ascend, aggregate into larger formations, and re-establish surface blooms. The greater the rainfall, the smaller the resultant Microcystis biomass, albeit with larger aggregated colony sizes. When rainfall exceeds 222 mm, the recovery rate of surface Microcystis biomass remains below 100%, decreasing to 19.48% at 666 mm of rainfall, while the median volume diameter (DV50) of the colonies increases to 139.07% of its pre-rainfall level. Furthermore, compared to pre-rainfall conditions, the photosynthetic activity of the surface Microcystis colonies was enhanced and the secretion of EPS was increased under heavy rainfall conditions. Our results identify a critical response time of 30 min for Microcystis colonies to rainfall, after which the response ceases to intensify. These insights are crucial for predicting post-rain Microcystis bloom dynamics and aiding management authorities in timely interventions.

Historical sedimentary and evolutionary characteristics of POPs and EDCs in typical regions of the three Gorges reservoir, China.

The historical sedimentary and evolutionary characteristics of persistent organic pollutants and endocrine disruptors in typical regions of the Three Gorges Reservoir are scarcely studied. Herein, the 96-year data on contaminated sediment history were reconstructed using Caesium 137 isotope dating. Polychlorinated biphenyl concentrations in the involved sediment cores ranged from non-detected (ND) to 11.39 ng/g. The concentrations of polycyclic aromatic hydrocarbons ranged from ND to 2075.20 ng/g and peaked in the 1970s owing to natural, agricultural and human activities. Further, phthalate esters (PAEs) and heavy metals (HMs) were detected at concentrations ranging from ND to 589.2 ng/g and 12.10-93.67 µg/g, respectively, with highest values recorded in the 1980s owing to rapid industrialisation and insufficient management during China's early reform and development stages. PAE and HM concentrations have increased in recent years, suggesting the need to focus on industrial and agricultural activities that have caused this impact. Although current pollutant concentrations in sediments do not pose a risk to the aquatic ecosystem, they should be continuously monitored.

Vertical distribution of microplastics in sediment columns along the coastline of China.

At present, there has been relatively less coverage of microplastics (MPs) pollution in sediment columns, especially across a large geographical span. This study collected sediment columns across 11 provinces along the coastline of China for MPs pollution investigation. The study found higher MPs diversity (Simpson diversity index) in sediment columns than in surface sediments, mostly comprising fiber MPs with dominant transparent and blue colors. Lower MPs pollution was noted in mangrove reserves, while estuarine and coastal areas showed higher pollution levels. Spearman correlation analysis shows that vertical of MPs abundance significantly decreased with depth at 6 of 11 sites. Large-sized MPs with diverse colors in deeper sediments (>40 cm) suggests that burial processes may render MPs more resistant to degradation. Our research highlights varied MPs distribution in coastal sediment, aiding future marine MPs pollution prediction and assessment.

The ice phenology as a predictor of Planktothrix rubescens bloom in vegetation season in temperate lakes.

Introduction: Global warming affects air and water temperatures, which impacts the phenology of lakes and aquatic ecosystems. These changes are most noticeable during winter, when the potentially toxic Planktothrix rubescens forms its inoculum for annual blooms. Mostly, research has been conducted on alpine lakes, where blooms have persisted for decades, while a few have focused on temperate lakes. Our study aimed to determine the factors influencing the dynamics of the development of P. rubescens in temperate lakes where blooms occasionally occur, with a particular emphasis on the role of ice phenology. Methods: We investigated the vertical distribution of P. rubescens in an annual cycle in three temperate lakes. Samples were collected monthly in the winter and biweekly during the vegetative seasons. Overall, 434 samples were collected and analyzed according to biological and chemical parameters. Physical parameters were measured in situ. Results: The vegetation seasons in temperate lakes showed a similar development pattern in the P. rubescens population as that in alpine lakes. Our results also show the influence of physical and chemical factors on the vertical distribution of this cyanobacterium. These results revealed the significant impact of P. rubescens filaments on phytoplankton biodiversity and biomass. Our data show the role of ice phenology in the establishment of the winter inoculum of P. rubescens and its further mass development until its disappearance in autumn. Conclusion: A climate-zone-independent pattern of P. rubescens blooms was observed during the vegetation periods. The population of P. rubescens was more influenced by physical factors than by the availability of dissolved nutrients in the water. Despite the same etiology, global warming has been shown to cause different responses in aquatic ecosystems, which affect the different nature of P. rubescens appearances. We associated blooms in temperate lakes, in contrast to alpine lakes, mainly with the presence of ice cover during severe winters, when the species establishes its inoculum. Hence, blooms in temperate lakes occur at different time intervals. Therefore, the dynamics of periodic blooms of P. rubescens in temperate lakes provide novel knowledge to the case study and a counterpoint to permanent blooms found in deep alpine lakes.

Riverbed depth-specific microplastics distribution and potential use as process marker.

Riverbed sediments have been identified as temporary and long-term accumulation sites for microplastic particles (MPs), but the relocation and retention mechanisms in riverbeds still need to be better understood. In this study, we investigated the depth-specific occurrence and distribution (abundance, type, and size) of MPs in river sediments down to a depth of 100 cm, which had not been previously investigated in riverbeds. In four sediment freeze cores taken for the Main River (Germany), MPs (≥ 100 µm) were detected using two complementary analytical approaches (spectroscopy and thermoanalytical) over the entire depth with an average of 21.7 ± 21.4 MP/kg or 31.5 ± 28.0 mg/kg. Three vertical trends for MP abundance could be derived, fairly constant in top layers (0-|30 cm), a decrease in middle layers (30-60 cm), and a strong increase in deep layers (60-100 cm). The dominant polymer types were polyethylene (PE), polypropylene (PP), and polystyrene (PS). Polyethylene terephthalate (PET) and PP were also found in deep layers, albeit with the youngest age of earliest possible occurrence (EPO age of 1973 and 1954). The fraction of smaller-sized MPs (100-500 µm) increased with depth in shallow layers, but the largest MPs (> 1 mm) were detected in deep layers. Based on these findings, we elucidate the relationship between the depth-specific MP distribution and the prevailing processes of MP retention and sediment dynamics in the riverbed. We propose some implications and offer an initial conceptual approach, suggesting the use of microplastics as a potential environmental process tracer for driving riverbed sediment dynamics.

Unveiling 3-D evolution and mechanisms of ozone pollution in Changzhou, China: Insights from lidar observations and modelling.

Ground ozone (O3) pollution has emerged as a prominent environmental concern in eastern cities of China, particularly during the summer and autumn seasons. However, a comprehensive investigation into the three-dimensional (3-D) evolution characteristics of O3 within complicated urban environments, especially in lake-land environment, is notably scarce. To enhance our understanding of the mechanisms underlying elevated O3 concentrations within a 3-D scale, this study employed an ozone lidar to delineate vertical ozone profiles in Changzhou, a typical city in China with complicated anthropogenic and biogenic emissions and complex land cover. The process analysis tool integrated into the Weather Research and Forecasting with Chemistry (WRF-Chem) model was further utilized to analyze the formation processes of O3. The results unveil a persistent O3 pollution episode lasting over 15 days in Changzhou during the study period, with multiple peaks exceeding 200 µg m⁻³. Notably, O3 predominantly accumulated within the boundary layer, confined below 1.2 km. Both ground and vertical contributions to this pollution were mainly due to local chemical reactions, with a maximum near-surface contribution reaching 19 ppb h-1 and a vertical contribution of 10 ppb h-1 at the height of 900 ± 200 m. Furthermore, episodes of the enhanced O3 concentrations on August 9 and August 26, 2021, were influenced by external advection process. Our study also found that local circulation plays an important role in the accumulation of surface O3 during certain periods. There was a temperature difference between the surface of Lake Tai and the adjacent land, resulting in the formation of lake-land breezes that facilitate the transport of O3 from the lake surface to the terrestrial environment during pollution events. Our study emphasizes the necessity of reducing local pollutant emissions and implementing joint emission controls as the primary strategies for mitigating O3 pollution in Changzhou and the surrounding region.

Polybrominated diphenyl ethers and their alternatives in soil cores from a typical flame-retardant production park: Vertical distribution and potential influencing factors.

With the prohibition on the production and use of polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE) and organophosphate flame retardants (OPFRs) have emerged as their alternatives. However, the vertical transport and associated influencing factors of these chemicals into soil are not clearly understood. To clarify the vertical distribution of the pollutants and related influencing factors, surface soil and soil core samples were collected at a depth in the range of 0.10-5.00 m in a typical 20-year-old flame-retardant production park and surrounding area. PBDEs and DBDPE show a clear point source distribution around the production park with their central concentrations up to 2.88 × 104 and 8.46 × 104 ng/g, respectively. OPFRs are mainly found in residential areas. The production conversion of PBDEs to DBDPE has obvious environmental characteristics. The vertical distribution revealed that most of the pollutants have penetrated into the soil 5.00 m or even deeper. The median concentrations of deca-BDE and DBDPE reached 50.9 and 9.85 × 103 ng/g, respectively, even at a depth of 5.00 m. Soil organic matter plays a crucial role in determining the vertical distribution, while soil clay particles have a greater impact on the high molecular weight and/or highly brominated compounds.

A convolutional neural networks method for tropospheric ozone vertical distribution retrieval from Multi-AXis Differential Optical Absorption Spectroscopy measurements.

The vertical distribution of tropospheric ozone (O3) is crucial for understanding atmospheric physicochemical processes. A Convolutional Neural Networks (CNN) method for the retrieval of tropospheric O3 vertical distribution from ground-based Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements to tackle the issue of stratospheric O3 absorption interference faced by MAX-DOAS in obtaining tropospheric O3 profiles. Firstly, a hybrid model, named PCA-F_Regression-SVR, is developed to screen features sensitive to O3 inversion based on the MAX-DOAS spectra and EAC4 reanalysis O3 profiles, which incorporates Principal Component Analysis (PCA), F_Regression function, and Support Vector Regression (SVR) algorithm. Thus, these screened features for ancillary inversion include the profiles of temperature, specific humidity, fraction of cloud coverage, eastward and northward wind, the profiles of SO2, NO2, and HCHO, as well as season and time features to serve as sensitive factors. Secondly, the preprocessed MAX-DOAS spectra dataset and the sensitive factor dataset are utilized as input, while the O3 profiles of the EAC4 reanalysis dataset incorporating the surface O3 concentrations are employed as output for constructing the CNN model. The Mean Absolute Percentage Error (MAPE) decreases from 26 % to approximately 19 %. Finally, the CNN model is applied for inversion and comparison of tropospheric O3 profiles using independent input data. The CNN model effectively reproduces the O3 profiles of the EAC4 dataset, showing a Gaussian-like spatial distribution with peaks primarily around 950 hPa (550 m). Since the reanalysis data used for model training has been smoothed, the CNN model is insensitive to extreme values. This behavior can be attributed to the MAPE loss function, which evaluates Absolute Percentage Errors (APEs) of O3 concentration at all altitudes, resulting in varying retrieval accuracy across different altitudes while maintaining overall MAPE control. Temporally, the CNN model tends to overestimate surface O3 in summer by around 20 µg/m3, primarily due to the influence of the temperature feature in the sensitivity factor dataset. In conclusion, leveraging MAX-DOAS spectra enables the retrieval of tropospheric O3 vertical distribution through the established CNN model.

Spatial distribution of small microplastics in the Norwegian Coastal Current.

High concentrations of microplastic (MP) particles have been reported in the Arctic Ocean. However, studies on the high-resolution lateral and vertical transport of MPs from the European waters to the Arctic are still scarce. Here, we provide information about the concentrations and compositions of MPs in surface, subsurface, and deeper waters (< 1 m, ∼ 4 m, and 17-1679 m) collected at 18 stations on six transects along the Norwegian Coastal Current (NCC) using an improved Neuston Catamaran, the COntinuos MicroPlastic Automatic Sampling System (COMPASS), and in situ pumps, respectively. FTIR microscopy and spectroscopy were applied to measure MP concentration, polymer composition, and size distribution. Results indicate that the concentrations of small microplastics (SMPs, <300 µm) varied considerably (0-1240 MP m-3) within the water column, with significantly higher concentrations in the surface (189 MP m-3) and subsurface (38 MP m-3) waters compared to deeper waters (16 MP m-3). Furthermore, the average concentration of SMPs in surface water samples was four orders of magnitude higher than the abundance of large microplastics (LMPs, >300 µm), and overall, SMPs <50 µm account for >80 % of all detected MPs. However, no statistically significant geographical patterns were observed in SMP concentrations in surface/subsurface seawaters between the six sampling transects, suggesting a relatively homogeneous horizontal distribution of SMPs in the upper ocean within the NCC/Norwegian Atlantic Current (NwAC) interface. The Lagrangian particle dispersal simulation model further enabled us to assess the large-scale transport of MPs from the Northern European waters to the Arctic.

Bacterial Diversity and Vertical Distribution Patterns in Sandy Sediments: A Study on the Bacterial Community Structure Based on Environmental Factors in Tributaries of the Yangtze River.

Bacterial diversity and its distribution characteristics in sediments are critical to understanding and revealing biogeochemical cycles in sediments. However, little is known about the relationship between biogeochemistry processes and vertical spatial distribution of bacterial communities in sandy sediments. In this study, we used fluorescence quantitative PCR, high-throughput sequencing technology and statistical analysis to explore the vertical distribution pattern of bacterial community diversity and its influencing factors in sandy sediments of the Yangtze River Basin. The aim is to enrich the understanding of the ecological characteristics and functions of bacteria in river ecosystems. The results showed that both sediment bacterial abundance and diversity showed a gradual decrease from surface to bottom in the vertical distribution. The main environmental factors that influenced the bacterial distribution pattern were pore water dissolved oxygen (DO), total nitrogen (TN) concentration and sediment nitrogen (N) content. The dominant bacterial species, Massilia and Flavobacterium, are suitable for growth and reproduction in high oxygen and nutrient-richer environments, while Limnobacter prefers low oxygen or anaerobic conditions. The vertical distribution pattern of bacteria and its influencing factors in river sandy sediment found in this study differ from the results in mud sediment, which may be related to the larger granular gap between sandy sediment and the lower content of organic matter. The findings of this study further our understanding of the distribution patterns and ecological preferences of microbial communities in river sediments, providing insights into how these communities may adapt to varying environmental conditions.

Comprehensive profiles of sulfur cycling microbial communities along a mangrove sediment depth.

The sulfur (S) cycle is an important biogeochemical cycle with profound implications for both cellular- and ecosystem-level processes by diverse microorganisms. Mangrove sediments are a hotspot of biogeochemical cycling, especially for the S cycle with high concentrations of S compounds. Previous studies have mainly focused on some specific inorganic S cycling processes without paying specific attention to the overall S-cycling communities and processes as well as organic S metabolism. In this study, we comprehensively analyzed the distribution, ecological network and assembly mechanisms of S cycling microbial communities and their changes with sediment depths using metagenome sequencing data. The results showed that the abundance of gene families involved in sulfur oxidation, assimilatory sulfate reduction, and dimethylsulfoniopropionate (DMSP) cleavage and demethylation decreased with sediment depths, while those involved in S reduction and dimethyl sulfide (DMS) transformation showed an opposite trend. Specifically, glpE, responsible for converting S2O32- to SO32-, showed the highest abundance in the surface sediment and decreased with sediment depths; in contrast, high abundances of dmsA, responsible for converting dimethyl sulfoxide (DMSO) to DMS, were identified and increased with sediment depths. We identified Pseudomonas and Streptomyces as the main S-cycling microorganisms, while Thermococcus could play an import role in microbial network connections in the S-cycling microbial community. Our statistical analysis showed that both taxonomical and functional compositions were generally shaped by stochastic processes, while the functional composition of organic S metabolism showed a transition from stochastic to deterministic processes. This study provides a novel perspective of diversity distribution of S-cycling functions and taxa as well as their potential assembly mechanisms, which has important implications for maintaining mangrove ecosystem functions.

Differentiating anthropogenic effects from natural metal(loid) levels in residential soil near a zinc smelter in South Korea.

Metal(loid)s pose a significant hazard due to inherent toxicity. Individuals are particularly exposed to metal(loid)s in soil through direct or indirect contact. Identifying metal(loid) sources in soil is required for exposure mitigation to anthropogenic metal(loid)s, while metal(loid)s are natural constitutes of soil. Metal(loid) concentrations and Pb isotopes were determined in residential soil profiles impacted by a Zn smelter to distinguish the anthropogenic effect from natural levels. One hundred sixty-nine core soil samples were collected from depths down to 5.5 m below ground level at 19 sites and were divided into Zn-Cd-As- and As-contaminated groups based on the worrisome level (WL) of soil contamination. The Zn-Cd-As-contaminated group (n = 62) was observed at depths < 1 m, showed high Zn levels (mean of 1168 mg/kg) and Cd and As frequently exceeding WLs, and had low 206Pb/207Pb ratios close to the Zn smelter. In contrast, the As-contaminated group (n = 96) was observed at depths > 1 m, did not have other metals exceeding WLs, and showed a wide range of 206Pb/207Pb ratios far away from the Zn smelter. The results indicated that the pollution sources of Zn-Cd-As- and As-contaminated soils were fugitive dust emissions from smelter stacks and geology, respectively. The metal(loid)s in host rock set geochemical baselines in soil profiles, while smelting activities affected the upper layers over 50 years. This study demonstrated the effectiveness of utilizing the vertical distribution of metal(loid) concentrations and Pb isotopes in soil profiles for distinguishing between anthropogenic and geogenic origins, in combination with baseline assessment.

Impact of soil physicochemical factors and heavy metals on co-occurrence pattern of bacterial in rural simple garbage dumping site.

Rural waste accumulation leads to heavy metal soil pollution, impacting microbial communities. However, knowledge gaps exist regarding the distribution and occurrence patterns of bacterial communities in multi-metal contaminated soil profiles. In this study, high-throughput 16 S rRNA gene sequencing technology was used to explore the response of soil bacterial communities to various heavy metal pollution in rural simple waste dumps in karst areas of Southwest China. The study selected three habitats in the center, edge, and uncontaminated areas of the waste dump to evaluate the main factors driving the change in bacterial community composition. Pollution indices reveal severe contamination across all elements, except for moderately polluted lead (Pb); contamination severity ranks as follows: Mn > Cd > Zn > Cr > Sb > V > Cu > As > Pb. Proteobacteria, Actinobacteria, Chloroflexi, and Acidobacteriota predominate, collectively constituting over 60% of the relative abundance. Analysis of Chao and Shannon indices demonstrated that the waste dump center boasted the greatest bacterial richness and diversity. Correlation data indicated a predominant synergistic interaction among the landfill's bacterial community, with a higher number of positive associations (76.4%) compared to negative ones (26.3%). Network complexity was minimal at the dump's edge. RDA analysis showed that Pb(explained:46%) and Mn(explained:21%) were the key factors causing the difference in bacterial community composition in the edge area of the waste dump, and AK(explained:42.1%) and Cd(explained:35.2%) were the key factors in the center of the waste dump. This study provides important information for understanding the distribution patterns, co-occurrence networks, and environmental response mechanisms of bacterial communities in landfill soils under heavy metal stress, which helps guide the formulation of rural waste treatment and soil remediation strategies.

Spatial distribution of volatile organic compounds in contaminated soil and distinct microbial effect driven by aerobic and anaerobic conditions.

The vertical distribution of 35 volatile organic compounds (VOCs) was investigated in soil columns from two obsolete industrial sites in Eastern China. The total concentrations of ΣVOCs in surface soils (0-20 cm) were 134-1664 ng g-1. Contamination of VOCs in surface soil exhibited remarkable variability, closely related to previous production activities at the sampling sites. Additionally, the concentrations of ΣVOCs varied with increasing soil depth from 0 to 10 m. Soils at depth of 2 m showed ΣVOCs concentrations of 127-47,389 ng g-1. Among the studied VOCs, xylene was the predominant contaminant in subsoils (2 m), with concentrations ranging from n.d. to 45,400 ng g-1. Chlorinated alkanes and olefins demonstrated a greater downward migration ability compared to monoaromatic hydrocarbons, likely due to their lower hydrophobicity. As a result, this vertical distribution of VOCs led to a high ecological risk in both the surface and deep soil. Notably, the risk quotient (RQ) of xylene in subsoil (2 m, RQ up to 319) was much higher than that in surface soil. Furthermore, distinct effects of VOCs on soil microbes were observed under aerobic and anaerobic conditions. Specifically, after the 30-d incubation of xylene-contaminated soil, Ilumatobacter was enriched under aerobic condition, whereas Anaerolineaceae was enriched under anaerobic condition. Moreover, xylene contamination significantly affected methylotrophy and methanol oxidation functions for aerobic soil (t-test, p < 0.05). However, aromatic compound degradation and ammonification were significantly enhanced by xylene in anaerobic soil (t-test, p < 0.05). These findings suggest that specific VOC compound has distinct microbial ecological effects under different oxygen content conditions in soil. Therefore, when conducting soil risk assessments of VOCs, it is crucial to consider their ecological effects at different soil depths.