Distribution characteristics and microbial synergistic degradation potential of polyethylene and polypropylene in freshwater estuarine sediments.

The microbial degradation of polyethylene (PE) and polypropylene (PP) resins in rivers and lakes has emerged as a crucial issue in the management of microplastics. This study revealed that as the flow rate decreased longitudinally, ammonia nitrogen (NH4+-N), heavy fraction of organic carbon (HFOC), and small-size microplastics (< 1 mm) gradually accumulated in the deep and downstream estuarine sediments. Based on their surface morphology and carbonyl index, these sediments were identified as the potential hot zone for PE/PP degradation. Within the identified hot zone, concentrations of PE/PP-degrading genes, enzymes, and bacteria were significantly elevated compared to other zones, exhibiting strong intercorrelations. Analysis of niche differences revealed that the accumulation of NH4+-N and HFOC in the hot zone facilitated the synergistic coexistence of key bacteria responsible for PE/PP degradation within biofilms. The findings of this study offer a novel insight and comprehensive understanding of the distribution characteristics and synergistic degradation potential of PE/PP in natural freshwater environments.

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.

Distinct differences of vertical phytoplankton community structure in mainstream and a tributary bay of the Three Gorges Reservoir, China.

The vertical distribution of phytoplankton plays a crucial role in shaping the dynamics and structure of aquatic communities. In highly dynamic reservoir systems, water level fluctuations significantly affect the physiochemical conditions and the phytoplankton community. However, the specific effects on the vertical characteristics of phytoplankton between the mainstream and the tributary bay of the reservoir remain unstudied. This study investigated the vertical aspects of phytoplankton density, biomass, α and ß diversity through monthly sampling over two years in the mainstream (Chang Jiang, CJ) and a tributary bay (Xiang Xi, XX) of the Three Gorges Reservoir in China. Phytoplankton density and biomass were significantly higher in XX, indicating an increased risk of algal blooms in the tributary. The phytoplankton community in CJ showed more stable species-environment relationships, a lower Shannon index and a higher evenness index, suggesting a relatively simple structure and a more uniform distribution of phytoplankton among different water layers. Conversely, XX showed greater differences between water layers (higher ß diversity), with significant negative correlations with water level and positive correlations with DO difference, dissolved silica (DSi) difference, and stratification. Peak phytoplankton density and biomass, as well as high ß diversity in XX, occurred during periods of decreased water levels with strong stratification in spring and summer. A structural equation model complemented by path analysis revealed that a decrease in water level could increase ß diversity either directly through internal processes with extended residence time or indirectly by modifying stratification and the vertical distribution of DSi in XX. Therefore, a proposed water quality management strategy for XX was to increase the water level or reduce ß diversity by implementing artificial mixing during stratification periods. Overall, this study lies in its comprehensive investigation of the vertical characteristics of the phytoplankton community in both the mainstream and the tributary bay of the Three Gorges Reservoir, elucidating the significant impact of water level fluctuations and providing insights for targeted water quality management strategies in the tributary bay to mitigate potential ecological impacts.

Depth distribution of plant-parasitic nematodes on bentgrass golf greens in Missouri and Indiana.

Control of plant-parasitic nematodes (PPNs) on golf putting greens with nematicides is dependent on the seasonal occurrence and depth distribution of target PPN populations. This study aimed to determine if plant-parasitic nematode populations on golf course putting greens in Missouri and Indiana peaked at a targetable depth at a specific time in the year, focusing primarily on lance (Hoplolaimus spp.) and root-knot (Meloidogyne spp.) nematodes. To elucidate species diversity in the region, rDNA from a subset of lance and root-knot nematodes was sequenced and analyzed, with additional micromorphology of a lance nematode assessed in scanning electron micrographs (SEM). Soil samples were taken to a depth of 25 cm and stratified into 5 cm increments during April, June, August and October at seven sites across Missouri, three in the Kansas City metro of Kansas in 2021 and in ten sites across Indiana in 2022. Samples were stratified in five-centimeter increments and aggregated for a total of 100 cm3 of soil at each depth for each sampling. Samples were processed using a semi-automatic elutriator followed by the sucrose-flotation method, and populations were counted using a hemocytometer and recorded. For molecular characterization, rDNA was extracted and analyzed from 31 individual lance nematodes from one site in Missouri and eight sites in Indiana, and 13 root-knot nematodes from nine sites across Indiana. A significant interaction occurred between sampling month and depth for lance and ring nematodes Missouri/KS, with both PPN populations peaking at the 0-5 cm depth during October, which is well after most targeted nematicide applications are applied. Ring nematodes in Indiana did not follow this trend and were most abundant in August at a depth of 0-5 cm. No significant interaction between depth and month occurred for lance or root-knot nematodes in Indiana, or root-knot nematodes in Missouri/KS. Hoplolaimus stephanus and H. magnistylus were the lance species identified on golf greens, and Meloidogyne naasi, M. graminicola and M. marylandi were the root-knot species identified. Scanning-electron micrographs confirmed morphological characteristics unique to H. stephanus.

Identification of particle distribution pattern in vertical profile via unmanned aerial vehicles observation.

Below the boundary layer, the air pollutants have been confirmed to present the decreasing trend with the height in most situaitons. However, the disperiosn rate of air pollutants in the vertical profile is rarely investigated in detail, especially through in-situ measurement. With this consideration, we employed an unmanned aerial vehicle equipped with portable monitoring equipments to scrutinize the vertical distribution of PM2.5. Based on the original data, we found that PM2.5 concentration decreases gradually with altitude below the boundary layer and demonstrated an obvious linear correlation. Therefore, the vertical distribution of PM2.5 was quantified by representing the distribution of PM2.5 with the slope of PM2.5 vertical distribution. We used backward trajectories to reveal the causes of outliers (PM2.5 increasing with altitude), and found that PM2.5 in the high altitude came from the southwest. Besides, the relationship between the vertical distribution of PM2.5 and various meteorological factors was investigated using stepwise regression analysis. The results show that the four meteorological factors most strongly correlated with the slope values are: (a) the difference in relative humidity between the ground and the air; (b) the difference in temperature between the ground and the air; (c) the height of the boundary layer; and (d) the wind speed. The slope values increase with increasing the difference in relative humidity between ground and air and the difference in temperature between the ground and the air, and decrease with increasing boundary layer height and wind speed. According to the Random Forest calculations, the ground-to-air relative humidity difference is the most important at 0.718; the wind speed is the least important at 0.053; and the ground-to-air temperature difference and boundary layer height are 0.140 and 0.088, respectively.

Influence of the Age of Free-Living Amoeba Cysts on Their Vertical Distribution in a Water Column.

Free-living amoebae (FLA) are widely distributed protozoa in both natural and artificial environments such as drinking water. In addition to the ability of all FLA to transport various pathogenic microorganisms, certain species, such as Acanthamoeba spp. or Balamuthia mandrillaris, have intrinsic pathogenic abilities and cause severe cerebral infections. Previous work has shown an enrichment of FLA cysts in biofilm developed in upper levels of Drinking Water Storage Towers (DWSTs), suggesting that differences in densities of FLA cysts may play a role in their unequal distribution in the water column. To evaluate this hypothesis, a model of a water column was created for this study and used to analyze the vertical distribution of cysts of the FLA Acanthamoeba castellanii, Vermamoeba vermiformis, and Balamuthia mandrillaris from 0 to 23 weeks. Interestingly, our data showed that the cysts of both A. castellanii and V. vermiformis were enriched in upper water levels during their aging. However, B. mandrillaris cysts were equally distributed in the water column during the entire study. These results show that, in addition to the role of water level variation in the DWST, some FLA cysts can become less dense during their aging, which contributes to their enrichment in upper water and therefore biofilm levels.

Insect root feeders incur negative density-dependent damage across plant species in an alpine meadow.

Although herbivores are well known to incur positive density-dependent damage and mortality, thereby likely shaping plant community assembly, the response of belowground root feeders to changes in plant density has seldom been addressed. Locally rare plant species (with lower plant biomass per area) are often smaller with shallower roots than common species (with higher plant biomass per area) in competition-intensive grasslands. Likewise, root feeders are often distributed in the upper soil layers. We hypothesized, therefore, that root feeders would incur negative density (biomass)-dependent damage across plant species. To test this hypothesis, we investigated the diversity and abundance of plant and root feeder species in an alpine meadow and determined the diet of the root feeders using metabarcoding. Across all species, root feeder load decreased with increasing aboveground plant biomass, root biomass, and total plant biomass per area, indicating a negative density dependence of damage across plant species. Aboveground plant biomass per area increased with increasing individual plant biomass and root depth per area across species, suggesting that rare plant species were smaller in size and had shallower root systems compared to common plant species. Both root biomass per area and root feeder biomass per area decreased with soil depth, but the root feeder biomass decreased disproportionately faster compared to root biomass with increasing root depth. Root feeder load decreased with increasing root depth but was not correlated with the feeding preference of root feeder species. Moreover, the prediction derived from a random process incorporating vertical distributions of root biomass and root feeder biomass significantly accounted for interspecific variation in root feeder load. In conclusion, the data indicate that root feeders incur negative density-dependent damage across plant species. On this basis, we suggest that manipulative experiments should be conducted to determine the effect of the negative density-dependent damage on plant community structure and that different types of plant-animal interactions should be concurrently examined to fully understand the effect of plant density on overall herbivore damage across plant species.

Long-term nitrogen addition modifies fine root growth and vertical distribution by affecting soil nutrient availability in a Mongolian pine plantation.

Fine roots are the primary organ of tree species in water and nutrient acquisition, and are the major contributor of forest soil organic carbon (C). However, it remains largely unknown how fine root growth dynamics and vertical distribution respond to long-term nitrogen (N) enrichment, which prevents us from accurately evaluating forest C sequestration potential under N deposition. Here, we investigated the effects of nine-year N addition (0 and 10 g N m-2 year-1) on fine root nutrients, biomass, production, turnover rate and vertical distribution in three soil layers (0-10, 10-20 and 20-40 cm) of a Mongolian pine (Pinus sylvestris var. mongolica) plantation in the Keerqin Sandy Lands, Northeast China. We found that soil inorganic N was increased and Olsen-P was decreased by N addition. N addition increased fine root N, C:P and N:P ratios, but reduced fine root P and C:N ratio across all soil layers. N addition reduced fine root biomass in 0-10 cm soil layer but increased it in 20-40 cm soil layer. N addition accelerated fine root turnover rate in 0-10 cm soil layer, and increased fine root necromass across all soil layers. Moreover, N addition significantly enhanced biomass of ectomycorrhizal extraradical hyphae in the 0-10 cm soil layer. Redundancy analysis showed that variations of fine root traits were well explained by soil NO3--N in 0-10 and 10-20 cm soil layers, and by soil NH4+-N and Olsen-P in 20-40 cm soil layer. Collectively, our results highlight the shift from N limitation to P limitation of Mongolian pine plantations under long-term N addition, and suggest that changes in fine root growth and vertical distribution induced by N addition could accelerate belowground C allocation in Mongolian pine plantations.

Effect of long-term in-row branch covering on soil microorganisms in pear orchards.

Branches covering (BC) is a way to reuse the pruned branches and save the cost of ground cloth. This study investigated the effects of BC and ground-cloth covering on the soil microcosm environment by measuring the chemical properties and microbial communities at different soil depths for 6 years. The results revealed that BC significantly improved soil chemical properties, increased the abundance of bacterial microbial communities and the diversity and homogeneity of bacteria and fungi, while decreased the abundance of fungal microbial communities. There was a threshold value for the regulation of microbial communities by BC, which decreased the high-abundance communities (Proteobacteria, Ascomycota, etc.) and increased the low-abundance communities (Acidobacteriota, Basidiomycota, etc.). Fungi were more sensitive to BC than bacteria. The stability and homogeneity of microorganisms were stronger in the 15-25 cm soil layer. The bacterial phyla were dominated by Proteobacteria, with the top 10 phyla accounting for more than 80% of the relative abundance; the genera were dominated by MND1, with the top 10 genera accounting for about 10%. The fungal phyla were dominated by Ascomycota, with the top 10 phyla accounting for 50-90%; the genera were dominated by unidentified Pyronemataceae sp., with the top 10 genera accounting for 30-60%. The phyla that differed significantly between treatments were mainly Proteobacteria, Ascomycota, Acidobacteriota, and Basidiomycota. In addition, metabolism was the predominant function in bacteria, while Saprotroph was the predominant function in fungi. Bacteroidota correlated strongly with soil chemical properties and bacterial functions, while Chytridiomycota correlated strongly with soil chemical properties and Pathogen-Saprotroph-Symbiotroph. In conclusion, BC can improve soil nutrient content and optimize microbial community structure and function. Through initially assessing the effects of BC on soil nutrients and microorganisms in pear orchard rows, this study provides a reference for excavating key microorganisms and updating the soil row management model.

Vertical variation in leaf functional traits of Parashorea chinensis with different canopy layers.

Introduction: Canopy species need to shift their ecological adaptation to improve light and water resources utilization, and the study of intraspecific variations in plant leaf functional traits based at individual scale is of great significance for evaluating plant adaptability to climate change. Methods: In this study, we evaluate how leaf functional traits of giant trees relate to spatial niche specialization along a vertical gradient. We sampled the tropical flagship species of Parashorea chinensis around 60 meters tall and divided their crowns into three vertical layers. Fourteen key leaf functional traits including leaf morphology, photosynthetic, hydraulic and chemical physiology were measured at each canopy layer to investigate the intraspecific variation of leaf traits and the interrelationships between different functional traits. Additionally, due to the potential impact of different measurement methods (in-situ and ex-situ branch) on photosynthetic physiological parameters, we also compared the effects of these two gas exchange measurements. Results and discussion: In-situ measurements revealed that most leaf functional traits of individual-to-individual P. chinensis varied significantly at different canopy heights. Leaf hydraulic traits such as midday leaf water potential (MWP) and leaf osmotic potential (OP) were insignificantly correlated with leaf photosynthetic physiological traits such as maximal net assimilation rate per mass (A mass). In addition, great discrepancies were found between in-situ and ex-situ measurements of photosynthetic parameters. The ex-situ measurements caused a decrease by 53.63%, 27.86%, and 38.05% in A mass, and a decrease of 50.00%, 19.21%, and 27.90% in light saturation point compared to the in-situ measurements. These findings provided insights into our understanding of the response mechanisms of P. chinensis to micro-habitat in Xishuangbanna tropical seasonal rainforests and the fine scale adaption of different resultant of decoupled traits, which have implications for understanding ecological adaption strategies of P. chinensis under environmental changes.

Environmental impact assessment of the coal yard and ambient pollution.

This study investigates the vertical distribution of pollutants emitted from coal yards using unmanned aerial vehicles (UAVs). Vertical concentration measurements of black carbon (BC) and particulate matter (PM) in a range of 1 m to 100 m above ground level (AGL) in the central coal yard showed clear spatial patterns and gradients of these pollutants. In addition, measurements were taken at specific heights (1 m, 30 m AGL, and 60 m AGL) at seven locations approximately 3 km from the yard. Thirteen measurements were carried out during the non-heating period under similar weather conditions. The measured BC concentrations decreased significantly with increasing altitude, with ground-level concentrations reaching 1.88 ± 0.61 µg/m3 and decreasing by over 46% at 80 m AGL. Similarly, PM10 concentrations at 60 m AGL decreased by 21.7%, with values of 25.99 ± 9.24 µg/m3 measured near the ground level and 16.52 ± 8.31 µg/m3 at 60 m AGL. The maximum coal particle pollution from the coal depot ranges from 500 to 1,000 m. The study showed a significant decrease in BC concentrations with height above the coal yard surface. Concentrations of PM10 and PM10-TSP showed a complex distribution influenced by local emissions and long-range particle transport. Meteorological factors, especially wind speed and direction, significantly influenced the pollutant dispersion. In addition, higher pollutant concentrations were measured during dry periods than after rainfall. The findings of this study contribute to a better understanding of the dispersion patterns and potential impacts of coal dust, enabling the implementation of targeted mitigation strategies and improved pollution control measures.

Spatial distribution and vertical characteristics of microplastics in the urban river: The case of Qinhuai River in Nanjing, China.

Microplastics (MPs) are emerging as global environmental pollutants, significantly influencing the safety of city rivers. This study investigated six sampling sites in the Qinhuai River of Nanjing, which explored the distribution and characteristics of MPs and the microbial structure in 2023. The studied river contained various levels of MPs with average concentrations of 667.68 items/L, whose abundance firstly decreased midstream and then increased downstream. The MPs abundance upstream was higher in surface water column, microplastics midstream and downstream accumulated more in deep water column. Black and blue are prevalent in the color distribution, while the polymers of PC, PP and PS changed with increasing depth, with a proportion of 74 % âˆ¼ 97 % in the dominant shapes of granules. Furthermore, the water with higher MPs may stimulate the growth of MPs-related bacteria in sediments, including the genus of Pseudoxanthomonas and Dechloromonas. Our research will provide constructive support for enhancing urban river management strategies.

Vertical distribution of microplastic along the main gate of Indonesian Throughflow pathways.

Even though Pacific - Indian Ocean exchange [Indonesian Throughflow (ITF)] has been measured for the last three decades, the measurements of microplastic in the region is very limited. This study was the initial investigation of the vertical distribution of microplastic in the deep-sea areas across the ITF Pathway. Niskin water samples were utilized to obtain the samples from a water column in a range of 5 to 2450 m. A total of 924 microplastic particles with an average abundance of 1.062 ± 0.646. n/L were found in the water column. Our findings indicate that water temperature and water density are the most significant factors correlated to the microplastic concentration. This study will be the first report discussing the distribution of microplastics in the deep-sea water column that could be highly significant in determining the fate and transport of microplastic within Indonesian waters that exits into the Indian Ocean.

Vertical distribution characteristics and transport paths of antibiotic resistance genes in constructed wetland system.

Although the migration and diffusion of antibiotic resistance genes (ARGs) in soil-plant systems have attracted much attention, the migration and diffusion characteristics between constructed wetlands and soil-plant systems differ greatly. Therefore, it is necessary to conduct research on vertical transmission and diffusion of ARGs in constructed wetlands. The vertical distribution and transmission of ARGs in constructed wetlands were explored via metagenomic analysis. The results showed that the proportion of multidrug ARGs was the largest, ranging from 24.2% to 47.5%. The shared characteristics of ARGs were similar to those of bacteria, and there were fewer unique ARGs and microbial species in mesophyll tissue. Sourcetracker analysis revealed that ARGs transfer between plants and atmosphere was bidirectional, but the diffusion of ARGs to atmosphere through plants was relatively weak. ARGs were mainly transmitted to atmosphere/surrounding environment through substrate and influent, and the contributions of substrate to ARGs in atmosphere/surrounding environment were 59.2% and 78.6%, respectively. ARGs involved in foliar attachment mainly originated from peripheral inputs. ARGs showed nonspecific selection for the host at phylum, class and order levels. These findings suggest that more attention should be given to the potential risks of ARGs in constructed wetlands, to formulate effective control and management strategies.

Vertical distribution characteristics of soil organic carbon and vegetation types under different elevation gradients in Cangshan, Dali.

Background: The Cangshan National Nature Reserve of Dali City was adopted as the research object to clarify the vertical distribution characteristics of soil organic carbon (SOC) and vegetation types at different elevations in western Yunnan. Methods: The contents of SOC, light fraction organic carbon (LFOC), heavy fraction organic carbon (HFOC), and water-soluble organic carbon (WSOC) in the 0-30 cm soil layer at different elevations (2,400, 2,600, 2,800, 3,000, 3,200, 3,400, and 3,600 m) were determined, and the above-ground vegetation types at different elevations were investigated. Results: Results showed that the SOC content was the highest in 0-20 cm surface soil and gradually decreased with the deepening of the soil layer. It increased then decreased with the increase in elevation, and it peaked at 3,000 m. The LFOC content was between 1.28 and 7.3515 g kg-1. It exhibited a decreasing trend and little change in profile distribution. The HFOC content ranged between 12.9727 and 23.3708 g kg-1; it increased then decreased with the increase in profile depth. The WSOC content was between 235.5783 and 392.3925 mg kg-1, and the response sensitivity to elevation change was weak. With the increase in elevation, WSOC/SOC and LFOC/SOC showed a similar trend, whereas HFOC presented an opposite trend. This observation indicates that the active organic carbon content at 3,600 m was lower than that at 2,400 m, and the middle elevation was conducive to the storage of active organic carbon. Meanwhile, the physical and chemical properties of soil affected the distribution of organic carbon to a certain extent. The vegetation type survey showed that the above-ground dominant species within 2,400-2,800 m were Pinus yunnanensis and Pinus armandii. Many evergreen and mixed coniferous broadleaf forests were distributed from 3,000 m to 3,200 m. Species of Abies delavayi were mainly distributed from 3,400 m to 3,600 m. This research serves as a reference for the study of forest soil carbon stability in high-elevation areas and plays an important role in formulating reasonable land use management policies, protecting forest soil, reducing organic carbon loss, and investigating the carbon sequestration stability of forest ecosystems.

[Characteristics of Vertical Distribution and Environmental Factors of Antibiotics in Quaternary Sedimentary Column in Urban Areas].

Antibiotics easily remain in sediments after migrating from the surface to the subsurface due to water-rock interactions, posing a risk of secondary release to groundwater. To investigate the vertical distribution characteristics and environmental impact factors of antibiotics, five 30 m quaternary sediment columns were drilled and stratified near the hospital, and five major classes of antibiotics and sulfonamide metabolites were tested and analyzed. The results showed that:① the antibiotic content in the sediments ranged from 3.05 to 107.03 µg·kg-1, and all of the target antibiotics were detected except lomefloxacin, of which ofloxacin and oxytetracycline were the most important antibiotics in the study area. ② The antibiotics did not show a strict downward trend in the vertical direction but varied with the lithological stratification. ③ Antibiotics were primarily deposited in the clay layer and varied with the fluctuation of the groundwater level. ④ The results of redundancy analysis between antibiotics and environmental factors suggested that pH and TOC controlled the fate and transformation of antibiotics through influencing the adsorption of antibiotics by sediments. The risk of antibiotic contamination from hospital wastewater seepage into the subsurface environment should be taken seriously.

Fine-Root Distribution and Soil Physicochemical Property Variations in Four Contrasting Urban Land-Use Types in South Korea.

Urbanization and associated forest conversions have given rise to a continuum of native (forest fragments) and modified (artificial grasslands and perennial ecosystems) land-use types. However, little is known about how these shifts affect soil and fine-root compartments that are critical to a functioning carbon and nutrient circulation system. In this study, soil physicochemical properties, fine-root mass, and vertical distribution patterns were investigated in four representative urban land-use types: grassland (ZJ), perennial agroecosystem (MP), broadleaf deciduous forest patch (QA), and coniferous evergreen forest patch (PD). We quantified the fine-root mass in the upper 30 cm vertical profile (0-30 cm) and at every 5 cm depth across three diameter classes (<2 mm, 2-5 mm, and <5 mm). Soil physicochemical properties, except for phosphorus, nitrogen, ammonium nitrogen, and sodium cations, varied significantly across land-use types. The total root biomass (<5 mm) decreased in the order of QA (700.3 g m-2) > PD (487.2 g m-2) > ZJ (440.1 g m-2) > MP (98.3 g m-2). The fine-root mass of ZJ and MP was correlated with soil nutrients, which was attributed to intensive management operations, while the fine-root mass of QA and PD had a significant relationship with soil organic matter due to the high inputs from forest litter. Very fine roots (<2 mm) presented a distinct decremental pattern with depth for all land-use types, except for MP. Very fine roots populated the topmost 5 cm layer in ZJ, QA, and PD at 52.1%, 49.4%, and 39.4%, respectively. Maintaining a woody fine-root system benefits urban landscapes by promoting soil stabilization, improving ground infiltration rates, and increasing carbon sequestration capacity. Our findings underscore the importance of profiling fine-root mass when assessing urban expansion effects on terrestrial ecosystems.

Trends and drivers of aerosol vertical distribution over China from 2013 to 2020: Insights from integrated observations and modeling.

Understanding aerosol vertical distribution is of great importance to climate change and atmospheric chemistry, but there is a dearth of systematical analysis for aerosol vertical distribution amid rapid emission decline after 2013 in China. Here, the GEOS-Chem model and multiple-sourced observations were applied to quantify the changes of aerosol vertical distributions in response to clean air actions. In 2013-2020, the MODIS aerosol optical depth (AOD) presented extensive decreasing trends by -7.9 %/yr to -4.2 %/yr in summer and -6.1 %/yr to -5.8 %/yr in winter in polluted regions. Vertically, the aerosol extinction coefficient (AEC) from CALIPSO decreased by -8.0 %/yr to -5.5 %/yr below ~1 km, but the trends weakened significantly with increasing altitude. Compared with available measurements, the model can reasonably reproduce 2013-2020 trends and seasonality in AOD and vertical AEC. Model simulations confirm that emission reduction was the dominant driver of the 2013-2020 decline in AOD, while the effect of meteorology varied seasonally, with contributions ranging from -2 % to 13 % in summer and -67 % to -2 % in winter. Vertical distributions of emission-driven AEC trends strongly depended on emission reductions, local planetary boundary layer height, and relative humidity. For aerosol components, sulfate accounted for ~50 % of the AOD decline during summer, followed by ammonium and organic aerosol, while in winter the contribution of organic aerosol doubled (24 %-35 %), and nitrate exhibited a weak increasing trend. Chemical production and meteorological conditions (e.g., relative humidity) primarily drove the nitrate contribution, but emission reduction and hygroscopicity were decisive for other components. This work provides an integrated observational and modeling effort to better understand rapid changes in aerosol vertical distribution over China.

Dynamic evolution of antibiotic resistance genes in plastisphere in the vertical profile of urban rivers.

Microplastics (MPs) can vertically transport in the aquatic environment due to their aging and biofouling, forming distinct plastisphere in different water layers. However, even though MPs have been regarded as hotspots for antibiotic resistance genes (ARGs), little is known about the propagation and transfer of ARGs in plastisphere in waters, especially in the vertical profile. Therefore, this study investigated the dynamic responses and evolution of ARGs in different plastisphere distributed vertically in an urbanized river. The biofilm biomass in the polylactic acid (PLA) plastisphere was relatively higher than that in the polyethylene terephthalate (PET), showing depth-decay variations. The ARGs abundance in plastisphere were much higher than that in the surrounding waters, especially for the PLA. In the vertical profiles, the ARGs abundance in the PET plastisphere increased with water depths, while the highest abundance of ARGs in the PLA mostly appeared at intermediate waters. In the temporal dynamic, the ARGs abundance in plastisphere increased and then decreased, which may be dominated by the MP types at the initial periods. After long-term exposure, the influences of water depths seemed to be strengthened, especially in the PET plastisphere. Compared with surface waters, the microbiota attached in plastisphere in deep waters showed high species richness, strong diversity, and complex interactions, which was basically consistent with the changes of nutrient contents in different water layers. These vertical variations in microbiota and nutrients (e.g., nitrogen) may be responsible for the propagation of ARGs in plastisphere in deep waters. The host bacteria for ARGs in plastisphere was also developed as water depth increased, leading to an enrichment of ARGs in deep waters. In addition, the abundance of ARGs in plastisphere in bottom waters was positively correlated with the mobile genetic elements (MGEs) of intI1 and tnpA05, indicative of a frequent horizontal gene transfer of ARGs. Overall, water depth played a critical role in the propagation of ARGs in plastisphere, which should not be ignored in a long time series. This study provides new insights into the dynamic evolution of ARGs propagation in plastisphere under increasing global MPs pollution, especially in the vertical profile.

Enhancement of atmospheric oxidation capacity induced co-pollution of the O3 and PM2.5 in Lanzhou, northwest China.

In recent years, the co-pollution of surface ozone (O3) and fine particulate matter (PM2.5) has emerged as a critical concern within specific regions of China's atmospheric environment. This study employed a comprehensive approach by integrating statistical analysis with the interpretable ensemble machine learning model. Delving deeply into the intricate mechanisms behind O3 and PM2.5 co-pollution in Lanzhou city from 2019 to 2022, the research synthesized and analyzed an array of data sources, including ground observations, a multi-parameter lidar system, and meteorological data. Our findings, derived from ground observations to vertical distribution, unequivocally confirm that the enhancement of atmospheric oxidation capacity serves as a critical driver in the genesis of secondary particles, playing a substantial role in the augmented levels of O3 and PM2.5 experienced during the warm season. Moreover, the impact of local weather patterns is indispensable as it precipitates a relatively stable mid-level atmosphere, culminating in elevated surface concentrations of both PM2.5 and O3. Overall, this study emphatically underscores the importance of adopting a comprehensive approach to address these environmental challenges.