Dust Deposition Research Articles

Transient high-temperature dust diffusion and deposition in a tee duct with vortex by large eddy simulations

This study employed computational fluid dynamics-discrete phase model (CFD-DPM) to investigate the transport characteristics of transient high-temperature dust in a vertical tee duct. Utilizing the large eddy simulation (LES) model, the research elucidated the flow characteristics, temperature field distribution, and particle deposition patterns within the tee duct. Specifically, it was observed that the vortex generated by the tee duct dissipated when x/D exceeds 20. Furthermore, high-temperature fluid exhibited an upward migration within the pipe by buoyancy, concurrently intensifying flow velocity fluctuations. Particle diffusion was initially driven by particle inertia and later became dominated by the combined effects of vortex and buoyancy. The deposition of particles displayed a trend of a sharp increase and decrease, then a gradual increase and decrease along the duct. The particle deposition can be divided into three stages, each governed by varying influencing factors on particle movement: (a) particle inertia within the range 0 < x/D < 5; (b) vortex carry spanning 5 < x/D < 20; and (c) turbulent pulsations beyond 20 < x/D. The total deposition mass was decreased by 50% by the vortex. This article provides a comprehensive description of the diffusion and deposition of transient high-temperature dust in a tee duct.

Investigation of Dust Deposition in Vegetation Period as an Ecological Service on Urban Trees in Budapest—A Case Study

In this article, we investigated the dust deposit on leaves in the vegetation period of urban trees using a simple washing method. The data presented in this paper are preliminary results. Air pollution and the area and population of cities are increasing. The EU directives require the reduction and maintenance of air pollution. Trees have many ecological services, including the dust removal capacity. We investigated four urban tree species (Acer platanoides L., Fraxinus excelsior L., Tilia tomentosa Moench., and Prunus cerasifera L. ‘Woodii’) in many locations in Budapest. After collection, the leaves were washed with distillated water, which was eliminated in a drying chamber, and then the dust was measured back into the beakers. Microscopical photos were taken of each leaf’s surface. We found differences among species and seasons, which confirmed previous studies. Examining the data by location, we found no difference in dust deposition, unlike previous results. The dust deposition for Tilia tomentosa Moench. is between 48 and 295 mg/m2; for Fraxinus excelsior L., between 47 and 205 mg/m2; and for Acer platanoides L., between 110 and 500 mg/m2. No relevant data were found for Prunus cerasifera ‘Woodii’ (between 426 and 492 mg/m2) due to its exposed location. New data were obtained in Budapest for the dust deposition of the ‘Woodii’ variety. We partially confirmed or provided new results by examining the dust deposition capacities of urban trees. The leaf surface structure of the examined trees is supposedly a typical cause of dust deposit differences.

A module based modeling framework for estimating lunar dust deposition due to human activities

Lunar dust is considered to be one of the top challenges for enabling humans to have extended stays on the moon. Human activities such as module landings and launches, walking, rover operation and construction activities will inevitably produce a significant amount of dust. Therefore, it is important to estimate the potential range and intensity of dust deposition caused by these activities to minimize dust accumulation over time and for maintenance planning and execution. A modular model that correlates the dust deposition distribution with initial mean dust particle velocity, its mean ejected angle and the total amount of ejected mass is developed for an elementary mechanical movement. This modular model is further employed to form a modeling framework to estimate dust deposition of a trajectory based activity of similar repeated movements such as the landing process of a lander, walking and rover operation. The model forms a unified modeling framework for different trajectory-based activities and is shown to predict consistent and physically meaningful ranges and intensities of dust deposition provided reliable data to calibrate the model parameters.

Source Attribution of Atmospheric Dust Deposition to Utah Lake

Atmospheric deposition (AD) is a significant source of nutrient loading to waterbodies around the world. However, the sources and loading rates are poorly understood for major waterbodies and even less understood for local waterbodies. Utah Lake is a eutrophic lake located in central Utah, USA, and has high-nutrient levels. Recent research has identified AD as a significant source of nutrient loading to the lake, though contributions from dust particles make up 10% of total AD. To better understand the dust AD sources, we sampled suspected source locations and collected deposition samples around the lake. We analyzed these samples using Inductively Coupled Plasma (ICP) for 25 metals to characterize their elemental fingerprints. We then compared the lake samples to the source samples to determine likely source locations. We computed spectral angle, coefficient of determination, multi-dimensional scaling, and radar plots to characterize the similarity of the samples. We found that samples from local dust sources were more similar to dust in lake AD samples than samples from distant sources. This suggests that the major source of the dust portion of AD onto Utah Lake is the local empty fields south and west of the lake, and not the farther playa and desert sources as previously suggested. Preliminary data suggest that dust AD is associated with dry, windy conditions and is episodic in nature. We show that AD from dust particles is likely a small portion of the overall AD nutrient loading on Utah Lake, with the dry and precipitation sources contributing most of the load. This case identifies AD sources to Utah Lake and provides an example of data and methods that can be used to assess similarity or perform attribution for dust, soil, and other environmental data. While we use ICP metals, any number of features can be used with these methods if normalized.

Environmental pollution biomonitoring around a cement factory based on the Air Pollution Tolerance Index of some tree species.

The present study examined the ability of Quercus castaneifolia C.A.M., Parrotia persica C.A.M., and Carpinus betulus L. for environmental pollution biomonitoring based on the Air Pollution Tolerance Index (APTI). Four leaf traits, total leaf chlorophyll content, leaf extract pH, ascorbic acid content, and relative water content of leaf, were used to compute the APTI values. The study was conducted at five sites in the Hyrcanian forests at different distances from a cement factory close to the Neka city, northern Iran. Based on the results, a 22.5, 30.1, and 25.8% decrease was thus recorded in total chlorophyll content for Q. castaneifolia, P. persica, and C. betulus, respectively, compared to the reference site. However, ascorbic acid content shows an increment of 179.8, 116.8, and 97.3% for P. persica, C. betulus, and Q. castaneifolia, respectively, in the polluted sites as compared to the reference site. The relative water content of P. persica was significantly higher than of Q. castaneifolia and C. betulus in all studied sites. APTI was significantly different among the species, and P. persica was highly tolerant to air pollution, with the highest values of APTI ranging from 11.8 to 16.9. The APTI values of Q. castaneifolia ranged from 9.5 to 11.3 and showed an intermediate tolerance to air pollution. Also, the most sensitive species to air pollution was C. betulus, with a range of 6.6-7.9 in APTI values. Based on APTI values, it can be suggested that P. persica can be used as a biomonitor, while C. betulus can be used as a bioindicator for atmospheric dust deposition and heavy metal pollution.

Evidence for the Presence of Thin and Heterogenous Dust Deposits on Ryugu's Boulders From Hayabusa2 MARA and Sample Data

AbstractMiddle infrared spectral results obtained in‐situ by the Hayabusa2 MARA instrument are generally in‐line with previous results and a new comparison with sample C0137 returned from asteroid (162173) Ryugu, being similar to an aqueously altered CI1 chondrite. The mid‐IR spectrum of the boulder on Ryugu measured by MARA is shallower around 9 μm compared to the laboratory spectrum of C0137. Here we show that discontinuous, fine dust deposits can partially explain the differences in the spectral data and remain in agreement with the temperature observations of the boulder by MARA if an opaque dust layer covers less than 3% of the field of view. Such a presence of dust covering a low porosity boulder was discounted by previous analysis of the mid‐infrared MARA data which did not consider a highly porous boulder as we do here.

Highly transparent, durable, and omniphobic liquid-like coatings for efficient dynamic de-wetting and self-cleaning applications

Solar cells, which are contributing significantly to achieving carbon neutrality but suffer from the dust deposition problem that limits their power conversion efficiency. Despite the many desirable properties of self-cleaning coatings to improve the efficiency of solar cells, one formidable challenge in designing coatings for their practical applications lies in integrating transparency, durability, and self-cleaning properties. Herein, we report a multifunctional, durable, and omniphobic liquid-like FEVE-g-PDMS coating, which was readily prepared by embedding highly flexible polydimethylsiloxane (PDMS) chains as dynamic de-wetting agent into the fluorinated ethylene-(hydroxyl-alkyl) vinyl ether (FEVE) matrix. The resultant coating exhibited low roughness and high transparency (89.72 % at 550 nm, the air was used as reference), which could be applied to the protective solar cover glass by facile spraying technique. The PDMS chains with high mobility were enriched on the coating surface and could dynamically rotate/bend/stretch to reduce the energy barriers for the moving liquids, endowing coating with unprecedented dynamic de-wetting property. Importantly, the coating demonstrated self-cleaning property, which could readily slide the liquid and dust contaminants off, resulting in a high efficiency recovery ratio for solar cells (95.37 %). Besides, the coating showed strong adhesion, and durability to ultraviolet rays, humidity and thermal atmospheres, and chemical media. Therefore, the synthetic omniphobic liquid-like coating holds great promise for the development of innovative self-cleaning materials with versatility and durability that are not realizable with conventional solid interface engineering.

Impact of dust deposition on the growth of marine autotrophic and heterotrophic microorganisms: Evidence from the South China Sea

Aeolian dust can provide nutrients for the ocean and affect the growth of phytoplankton. However, the impacts of dust deposition on autotrophic and heterotrophic microorganisms have rarely been studied. In this study, we conducted two microcosm experiments in the low-nutrient and low-chlorophyll environment of the South China Sea and found that dust did not stimulate the abundance of autotrophic and heterotrophic microorganisms. Our results show that dust contains most of the unreacted iron-bearing minerals, and thus provides limited bioavailable iron and nitrogen for bacterioplankton and phytoplankton growth. These results elucidate the overlooked impacts of the properties of the iron-bearing minerals in aeolian dust on microbial communities, which may play an important role in marine ecosystems and climate change.

Constraining Changes in Surface Dust Thickness on Mars Using Diurnal Surface Temperature Observations From EMIRS

AbstractDiurnal surface temperature data collected from the Emirates Mars Infrared Spectrometer have been used to characterize dust redistribution on Mars following a regional dust storm in January 2022. A comparative temporal analysis is conducted pre‐ and post‐dust storm to estimate net changes in surface dust thickness at Syrtis Major, Isidis Planitia, Tyrrhena Terra, Hesperian Planum, and Elysium Planitia. By leveraging data from a numerical thermal model, we relate differences in observed surface temperature to changes in the thickness of the surface dust layer. We describe the methodology for estimating net changes in surface dust thickness, including a description of the thermophysical model employed, provide a sensitivity analysis with respect to local time and surface properties, and discuss the implications of our findings. Surface temperature differences suggest both dust deposition and removal, with some regions experiencing a net removal as high as 340 μm, while other regions experienced net deposition reaching up to 120 μm. Visible‐wavelength imagery from the Emirates Exploration Imager, which is more sensitive to changes in surface dust distribution, is incorporated in our analysis to provide additional context. When the area of each region of interest is accounted for, we find that the dust storm had the potential to remove and/or deposit more than 1.51 × 109 and 1.20 × 109 kg, respectively, suggesting that dust reservoirs are capable of transporting vast quantities of dust over short timescales.

The Importance of Dynamic Iron Deposition in Projecting Climate Change Impacts on Pacific Ocean Biogeochemistry

AbstractDeposition of mineral dust plays an important role in upper‐ocean biogeochemical processes, particularly by delivering iron to iron‐limited regions. Here we examine the impact of dynamically changing iron deposition on tropical Pacific Ocean biogeochemistry in fully coupled earth system model projections under several emissions scenarios. Projected end‐of‐21st‐century increases in central tropical Pacific dust and iron deposition strengthen with increasing emissions/radiative forcing, and are aligned with projected soil moisture decreases in adjacent land areas and precipitation increases over the equatorial Pacific. Increased delivery of soluble iron results in a reduction in, and eastward contraction of, equatorial Pacific phytoplankton iron limitation and shifts primary production and particulate organic carbon flux projections relative to a high emissions projection (SSP5‐8.5) wherein soluble iron deposition is prescribed as a static climatology. These results highlight modeling advances in representing coupled land‐air‐sea interactions to project basin‐scale patterns of ocean biogeochemical change.

Mineral Composition Effects on Dust Deposition at Realistic Engine Conditions

Abstract In this article, the role of mineral composition was assessed for Air Force Research Laboratory Test Dust (AFRL), for deposition in a realistic gas turbine engine environment. Experiments were performed on an effusion cooling test article with a coolant flow temperature of 894 K and surface temperature of 1144 K. Aerosolized dust with a 0–10 µm particle size distribution was delivered to the test article. The mineral recipe of AFRL was altered such that the presence of each of the five components ranged from 0% to 100%, and capture efficiency, hole capture efficiency, blockage per gram, and normalized deposit height were reported. Results are compared to a previous study of the intermineral synergies in an impingement cooling jet at the same temperature conditions. Despite differences in experimental facility flow geometry, overall agreement was found between the trends in the deposition behavior of the dust blends. The strong deposition effects that were observed were shown to be related to adhesion forces of particles, mechanical properties, and chemical properties of the dust minerals. Supplemental testing was performed in a high-temperature (1425–1650 K) impinging jet (200–260 m/s) to evaluate mineral effects at hot gas path conditions. Capture efficiency and morphology of dust deposits are reported. The capture efficiency in this regime was shown to correlate well with temperature, with chemical effects being secondary. An attempt was made to predict capture efficiency using chemical assessments such as a ratio of bases to acids, Ca:Si ratio, and optical basicity with only modest success.

Publisher’s note

This study is an experimental investigation of the effect of natural dust deposition on the performance of three (PV) systems installed on the rooftop of the faculty of science and technology in the city of Mohammedia of Morocco in a Mediterranean climate. To determine the local soiling losses in solar PV systems electrical performance analysis using the IEC60891 procedure and the optical, morphological, and thermal properties of the dust deposited on PV systems is assessed. The results show that power production and maximum current of PV modules decrease by 7.4–12.35% and 11.6–18%, respectively, after allowing dust to accumulate naturally without any scheduled cleaning. In addition, the optical transmittance of the glass samples is reduced by 75–5%, from transmittance/absorbance data obtained with a UV-Visible spectrophotometer. The elemental and chemical analysis results by XRF, XRD, and FT-IR indicate that silica and calcite are the predominant components of the dust sample. Differential scanning calorimetry is used to assess the thermal properties (DSC) in a temperature range of 6–85 °C and the Laser-Flash method (LFA) for measuring thermal conductivity and diffusivity in the temperature range of 25 °C to 70 °C. It has been established that, for a given mass, dust particles can accumulate energy in thermal form when the temperature rises.

Significance of site-specific factors to peat accumulation indicated by differences in Holocene histories of dust delivery and peat deposition at two neighboring locations in the Altai Mountains, northwestern China

Peatlands can archive exceptional paleoenvironmental histories of dust delivery because of their uninterrupted and elevated accumulation rates, yet long-term records of dust deposition and its effect on peat accumulation are rare in the arid and semiarid Asian regions that can be major dust sources. We present here high-resolution Holocene peat accumulation and paleodust records from the Tielishahan (TLSH) and Halashazi (HLSZ) peatlands in the Altai Mountains of northwestern China. We find that although the two peatlands share common histories of external climate forcing and dust delivery, they have significantly different long-term rates of peat accumulations. Peat deposition initiated ~2 kyr earlier in the HLSZ peatland than in the TLSH peatland, exhibiting higher peat accumulation rates and greater mineral dust fluxes during the early Holocene, but it has constantly smaller values from the mid-Holocene to the present. The TLSH peatland has a higher peat accumulation rate and mineral dust flux during the early Holocene, lower values during the mid-Holocene, and increasing values during the latest Holocene. The elemental proxies in the two peat cores indicate that atmospheric deposition is the major factor in controlling delivery of mineral elements in HLSZ peatland, whereas elemental delivery in the TLSH peat record is affected by both the regional atmospheric dust flux and the water table under this sequence.We also find that peat accumulation is closely related to mineral dust deposition, as most Asian locations generally share similar patterns in long-term peat accumulation and dust deposition. We postulate that increased aridity in the dust sources of arid central Asia and stronger westerly winds induced by negative NAO variations are key drivers on greater dust deliveries. We further postulate that local factors, such as site-specific differences in permafrost thawing, the areas of the peatlands, and their hydrology are the main reasons for the asynchronous Holocene histories of these two neighboring peatlands. These local factors should be considered when interpreting long-term paleoclimate records from rates of peat accumulation and paleodust delivery.

ASSESSMENT OF THE EFFECT OF AEROSOL DISINFECTION OF NANOSILVER AND HYDROPEROXIDE AG+ AT CAN THO UNIVERSITY OF MEDICINE AND PHARMACY

Background: One of the crucial methods for lowering hospital infections is air disinfection. Because the airborne contagion environment is difficult to control, the development of effective air disinfectants is critical to maintaining a safe air environment and preventing respiratory infections. At the Hospital of Can Tho University of Medicine and Pharmacy, nanosilver and hydroperoxide Ag+ are two different kinds of airborne infection control, so an analytical cross-sectional study was conducted with objectives: to compare the disinfection efficacy of two solutions, nanosilver and 5% Hydroperoxide - 0.005% Ag+, and to assess the efficacy of the silver nano solution and 5% Hydroperoxide - 0.005% Ag+ solution in disinfecting hospital air. Materials and methods: This study was conducted on 156 air microbiological samples in 13 wards at the Can Tho University of Medicine and Pharmacy Hospital using Koch's dust deposition method based on the principle of allowing dust to settle on the surface of nutrient agar boxes for a certain period. Data analysis using SPSS 26.0 software. Results: After disinfecting the rooms with nanosilver, the air quality was good in 69.23% of cases and pretty in 30.07%. With 5% Hydroperoxide - 0.005% Ag+, the number of rooms with good air quality was 15.39%, with pretty air was 69.23, and with poor air was 15.39%. Nanosilver can eradicate the fungus from Sabouraud Agar medium, and the density after disinfection was lower than before; the difference was not statistically significant (p&gt;0.05). Moreover, on Macconkey Agar and Blood Agar medium, bacterial density after disinfecting by nanosilver was decreased; the difference was statistically significant (p &lt; 0.05). Nanosilver reduced the bacterial density in 4 types of rooms better than 5% Hydroperoxide - 0.005% Ag+ solution. However, the difference was not statistically significant (p &gt; 0.05). Conclusions: Nanosilver can be used to disinfect the hospital air as an alternative to 5% Hydroperoxide - 0.005% Ag+. Nanosilver disinfects well on gram-negative and gram-positive bacteria. Additional methods for improving the antifungal impact of nanosilver are required.

Transformation of lakebed into a major soluble-salt-bearing dust source for Asia since the mid-pleistocene

Loess in the Chinese Loess Plateau (CLP) preserves abundant information about the dust cycle over Asia. However, the variations of loess source and composition over time remain controversial. Soluble salt is an important dust component and is linked to the landforms and environments associated with dust mobilization, transport and deposition. Based on an investigation of the soluble salts of two loess sequences from the central and western CLP, we show that the soluble salts of Chinese loess mainly stepwise increased at ∼1 and ∼ 0.5 Ma. Several lines of evidence indicated that the increased supply of soluble salts mainly originated from dust input, suggesting the enhanced salinity of Asian dust. The enhanced soluble-salt-bearing dust was driven by lakebed evolution in the potential source areas, as confirmed by abundant geomorphological and sedimentological evidence. The Mid-Pleistocene Transition (associated with Tibetan Plateau uplift) induced aridity of the potential source areas (PSA) and Mid-Brunhes Transition triggered intensifying East Asian summer monsoon are responsible for the stepwise lakebed evolution in the PSA at ∼1 and ∼ 0.5 Ma, respectively, which in turn acted as an important soluble-salt-bearing dust reservoir. These findings provide new evidence for understanding the evolution of regional dust emissions and their possible environmental effects in the past and future.

Preserving Artistic Legacy: A Frame-Guided Approach for Color Recovery in Aged Tangka Paintings

Over time, the colors in old Tangka paintings can fade due to various factors, including exposure to light, air pollution, humidity, and dust deposition. Interestingly, the frame acts as a physical barrier between the artwork and its surroundings, offering some protection against the harmful factors that contribute to color fading. In this paper, we propose a novel approach to recover the faded colors of Tangka paintings by leveraging the visual cues provided by the frame-covered area. Our method involves the development of an interactive annotation pipeline and the utilization of histogram matching for color restoration. We applied this approach to faded, aged Tangka paintings in Palace Museum’s collection and achieved visually plausible color recovery, even for intricate patterns that are challenging to restore manually.

Research on Dust Migration and Dust Deposition Rules of Breathing Zone in Fully Mechanized Mining Face.

The dust in the breathing zone of the fully mechanized mining face poses a serious threat to the lives and health of the workers, and clarifying the distribution and settlement pattern of the dust in the breathing zone is an important foundation for reducing dust concentrations in the breathing zone and improving the workers' working environment. The dust concentration distribution at the mining face and the settlement results of different dust particle sizes along the breathing zone were analyzed in detail using a combination of computational fluid dynamics simulation and downhole measurements by establishing a highly simulated 3D solid model of the 2302 fully mechanized mining face at the Xinqiao coal mine. The study's findings reveal that dust from advanced support and coal-cutting processes converge within 20-60 m of the coal mining region, generating a high-concentration pollution zone at the height of the sidewalk breathing zone. The particle size of dust in the breathing zone is primarily concentrated between 1 and 40 μm, and the fully mechanized mining face is split into a rapid settling area, a medium settling area, and a slow settling area based on particle size settling speed. Eddy currents in the return airway lead to an increase in dust particles of 20-40 μm in the breathing zone area. The results of the study can provide a theoretical basis for dust management at the fully mechanized mining face for the breathing zone area.

Potential toxic heavy metals in village topsoil of antimony mining area: Pollution and distribution, environmental safety----A case study of Qilijiang village in xikuangshan mining area, central Hunan Province, China

Potential toxic heavy metal elements in the topsoil of villages in antimony mining areas pose a serious threat to residents' health, and scientific analysis of potential toxic heavy metal element contamination in the topsoil of villages in antimony mining areas and environmental safety is especially important for residents' health and the high quality of sustainable development in the mining areas. In this study, we chose Qilijiang Village in the Lengshuijiang Tin Mine in Hunan Province and used field sampling and indoor experiments to investigate the toxic heavy metal pollution and environmental safety of the topsoil using key technologies such as geomatics mathematical analysis, analysis of variance (ANOVA), GIS, and environmental risk assessment modeling.The average contents of potential Pb, Cr, As, Cd, and Sb in the topsoil of the residential area exceeded the standard values by 1.12, 1.00, 15.82, 13.37, and 38.87 times, respectively; the degree of contamination risk was As > Sb > Cr > Pb > Cd in the order of As > Sb > Cr > Pb > Cd; and the high-loading elements were As and Sb with a high degree of homology. The results of spatial and principal component analysis revealed that the potential Pb, Cr, As, Cd, and Sb in the surface soil of the residential area were influenced by discrete sources such as mining, processing, and other industrial and mining activities, as well as dust deposition and residents' domestic drainage water (As and Sb); the natural geological backdrop and the metal products industry (Cr); lead-acid batteries, industrial activities, and gasoline additives (Pb); residents of the residential area, green space, and resident gardens; fertilizer application; and pesticide use (Cd). According to the results of the environmental safety analysis, Sb, As, and Cd are in the heavy pollution category, while Cr and Pb are in the low pollution category, and the ecological danger of metals is Cd (401.22) > Sb (388.70) > As (158.16) > Pb (5.58) > Cr (2.00).Cd and Sb have reached a very high degree of ecological risk; As is at a higher risk level; and Pb and Cr are at a lower or no risk level. Except for As and Sb (HI value > 1), the non-carcinogenic risk of village topsoil was insignificant, and Pb, Sb, and As in topsoil exhibited carcinogenic risk, with As exceeding the permissible level, and the carcinogenic risk of As in Qilijiang village was more serious than that of Sb. The study's findings are critical for implementing preventive steps to protect the ecosystem and assure long-term growth in the area.

Effects of road dust on vegetation composition and surface chemistry of three ombrotrophic peatlands in eastern Canada

Dust deposition can fertilize nutrient-limited peatlands and affect their plant assemblages and ecosystem functions, but the effects of local road dust on peatlands have seldom been studied. Here, we investigate the responses of vegetation composition and surface chemistry (vegetation, surface peat, and groundwater chemistry) at three ombrotrophic peatlands: Rivière-au-Tonnerre (RT), Chemin de l'Anse-de-la-Grande-Pointe (GP), and Kegaska (KEG) in eastern Québec, Canada, to varying levels of road dust deposition with differential chemical composition. At each site, a transect aligned with the dominant wind direction, starting at and perpendicular to the roadside, was sampled at increasing intervals up to 250 m away from the gravel (unpaved) road. We find that the ash content of surface peat is highest closest to the roads at all three sites and decreases exponentially with increasing distance up to 200 m away from the roads. At KEG, with the highest amount of, and the most phosphorus (P) rich, road dust deposition, the ash content is highest among the three sites, decreasing most rapidly with distance away from the road. The stoichiometric mass ratios of carbon (C), nitrogen (N) and P, i.e., C:N, C:P, and N:P, in foliar tissues and surface peat increase significantly with distance away from the road at KEG, and mosses are found to be more responsive in terms of foliar chemistry than shrubs to the road dust deposition. A higher concentration of total dissolved phosphorus at KEG is found closer to the road. At GP, having a moderate amount of road dust deposition, significant increases in C:N, C:P, and N:P ratios with distance are found only in surface peat but not in foliar tissues. Due to the presence of carbonate minerals in the road dust of GP, the calcium (Ca) concentration and pH value of groundwater closer to the road are higher, leading to an obvious loss of vegetation coverage, especially mosses, and a consequent increase in NO3− leaching. In contrast, at RT, having the lowest amount of road dust deposition, only a few clear variation patterns in surface chemistry are found along the sampling transect. Overall, our results suggest that dust from gravel roads can be an important localized source of nutrients for adjacent peatlands and influence their vegetation composition and surface chemistry, depending on the amount of road dust and its chemical composition, especially its contents in Ca and P.

The Long-Term Deep Loessal Sediments of Northeast China: Loess or Loessal Paleosols?

Previous research assumed deep buried loess as the initial composition of the overlying paleosol and failed to address the long-term continuous pedogenic weathering history in the deep loess-paleosol sequence, which was attributed to little understanding on the difference between loess and paleosol in the long-term deep loess-paleosol sequence. To distinguish between the loess and paleosol, in the long-term deep loess-paleosol sequence in northeast China, the morphology, dust deposition fluxes, geochemical characteristics, magnetic susceptibility, and grain size distributions were investigated. Results showed that the loess layers buried at depth could be differentiated from the paleosol by their poor pedogenic development. The presence of coarser grains in the loess as well as lesser amounts of clay and Fe–Mn coatings compared to paleosol indicated weaker weathering of the loess. Also, optical iron clay films deposited on the surface of the skeleton particles were less visible in the loesses than in the paleosols. From the loess evolution perspective, the pedogenic formation process of the newly formed loess soils should be considered as important as that of the reddish paleosol layer based on criteria of formation time, depth within profile, and morphological characteristics. The formation of the reddish or yellowish paleosol layer was constrained by pedogenic environments associated with climatic change and by the relative rates of deposition and pedogenesis. The terms “loessal paleosol” and “loessal paleosol sequence” are suggested to aid in systematically and consistently addressing the long-term pedogenic weathering evolution recorded in the complex formation of deep loess and paleosol sequences in pedology research. The long-term deep loessal sediments of Northeast China are loessal paleosols, which cannot be simply used as a reference for the overlying paleosol and be deducted from pedogenesis consideration.