Concentration Distribution Characteristics Research Articles

Cadmium exposure in marine crabs from Jiaxing City, China: Insights into health risk assessment

Abstract In this study, a survey was conducted on cadmium levels in seawater crabs during 2015–2023 in Jiaxing, China, to evaluate their concentration levels, distribution characteristics, and health risks. The concentrations of cadmium were analyzed using atomic absorption spectroscopy and inductively coupled plasma mass spectrometry. The pollution level and health risks were assessed using the single-factor pollution index and margin of safety (MOS) method. The results showed that cadmium in seawater crabs ranged from 0.091 to 21.136 mg/kg, with a median value of 1.360 mg/kg and an exceedance rate of 15.8%. Over 88% of cadmium was primarily accumulated in crab roe and hepatopancreas. Bread crabs had the highest cadmium content (1.894 mg/kg), followed by swimming crabs (1.422 mg/kg), flower crabs (1.226 mg/kg), and mud crabs (1.070 mg/kg). The single-factor pollution index indicated that the median cadmium level in seawater crabs represented mild pollution (P i = 0.453). MOS risk assessment revealed that cadmium exposure from general consumption posed a low health risk (P50, MOS = 3.47). However, there was a potential risk associated with high consumption of highly polluted swimming crabs (P95, MOS = 0.94) and bread crabs (P95, MOS = 0.45). The above-standard cadmium content in market-sold seawater crabs highlights the need for improved food market monitoring. While daily consumption poses relatively low dietary risks for the general population, careful considerations on daily intake levels are needed.

The analysis of ozone pollution in urban agglomerations of the Sichuan basin based on the scale decomposition-synthesis method.

The analysis of ozone pollution in urban agglomerations of the Sichuan basin based on the scale decomposition-synthesis method.

Reinforcement of Carbazole-Based Self-Assembled Monolayers in Inverted Perovskite Solar Cells.

Self-assembled monolayers (SAMs) with excellent hole conduction capabilities significantly improve the performance of inverted perovskite solar cells (PSCs). However, the amphiphilic nature of SAMs causes the spontaneous formation of spherical micelles in solution, limiting their surface coverage and uniformity on indium tin oxide (ITO) substrates. Furthermore, the distribution of the SAMs directly affects the morphology of perovskite films and the charges transfer properties at the buried interface. This study employs a cosolvent strategy combining n-butanol and dimethyl sulfoxide to improve the uniform spreading of SAMs on ITO. The synergistic interaction between the solvent molecules smooths the surface of [2-(3,6-dimethoxy-9H-carbazol-9-yl) ethyl] phosphonic acid (MeO-2PACz) and enhances its surface coverage. The cosolvent based MeO-2PACz has the characteristics of concentrated surface potential distribution and high work function, exhibiting uniform and enhanced P-type behavior. Additionally, the cosolvent-treated SAMs provide uniform nucleation sites for the crystallization of perovskite, effectively eliminating void defects at the buried interface and improving the crystallinity of perovskite films. Consequently, the optimized device achieves a power conversion efficiency (PCE) of 25.51% and a fill factor of 84.38%. Furthermore, the ordered SAMs improve the stability of PSCs, with encapsulated device retaining 92.63% of its initial PCE after operating for 1500 h under simulated AM 1.5G standard irradiation in air at 65 °C.

Experimental Study on Concentration and Size Distribution Characteristics of Particulate Matter in Cold and Hot Rolling

Workers’ health is jeopardized in steel rolling workshops due to the production of particulate matter. These particles’ physicochemical properties have a direct impact on their effects on human health, emphasizing the importance of understanding these properties for exposure control. This study investigated particulate matter emissions in hot and cold steel rolling workshops, focusing on mass concentrations, particle size distributions, and elemental compositions. The findings revealed that particles predominantly range from 0.3 to 1.0 μm in size, with irregular block-like and fibrous morphologies. Elemental analysis showed distinct compositions: the main components in the hot rolling workshop were oxygen, calcium, silicon, carbon, and iron while those in the cold rolling workshop were oxygen, silicon, aluminum, carbon, and iron. The particulate matter concentrations were higher in the hot rolling workshop than in the cold rolling workshop. The Rosin–Rammler particle size distribution function was applied to characterize particle size distribution at emission sources. This paper highlights the dynamic variations and spatial distribution patterns of particulate matter during rolling processes, providing key data for understanding particulate matter behavior in industrial environments and informing targeted pollution control strategies.

Well location layout of surface drilling for gas extraction in an abandoned gob

The gob is formed by large-scale voids left after the completion of underground coal mining. A large amount of desorbed gas still remains in the gob. Surface drilling is used to extract gas from abandoned coal mines. The location of surface drilling in abandoned gobs is the key to ensure efficient gas extraction. In this paper, an abandoned gob is divided into the start mining area, the middle area, and the end mining area based on the result of physical similarity simulation experiment. The distribution characteristics of methane concentration in the abandoned gob under the surface drilling extraction are calculated by using the numerical simulation software Ansys. The gas extraction effect in the start mining area, the middle area, and the end mining area is compared. Results show that the methane control range by extraction pipe presents different characteristics along the X-, Y-, and Z-axes of the abandoned gob. When Z = 55 m, the methane control range by extraction pipe reaches the maximum. When Y = 40 m and 60 m, the methane control range by extraction pipe reaches the maximum. In the start and end mining areas, the methane control range by extraction pipe reaches the maximum when X = 70 m and 30 m, respectively. In the middle area, the methane control range by extraction pipe reaches the maximum when X = 100 m and 150 m. The gas extraction effect is the best in the end mining area, followed by the start mining area and finally the middle area. The preferred location of surface drilling is the end mining area of the abandoned gob. The research results provide theoretical basis for gas extraction in abandoned coal mines.

Study on concentration distribution and detonation characteristics of typical multiphase fuel in orthogonal flow field

Study on concentration distribution and detonation characteristics of typical multiphase fuel in orthogonal flow field

Distribution characteristics and analysis of fungal aerosol concentration and particle size in air-conditioned wards in Wuhan, China.

Fungal contamination in the air of hospital wards can affect the health of medical staff, patients, and caregivers. Through systematic analysis of the concentration, types, and particle size distribution characteristics of fungi in the air of wards in Wuhan, China, in 2023, it was found that there was no significant correlation between the concentration of fungi in the air of wards and the disease type and personnel density. The main influencing factors were temperature, humidity, and seasonal changes. The distribution characteristics of fungal particle size in the wards of various departments in winter and summer showed a roughly normal distribution, with the percentage of particle size gradually increasing from stage I to stage III. The proportion from stage III to stage V was generally the highest, while the proportion from stage V to stage VI gradually decreased. There was no significant difference in the median diameter of airborne fungal conidia between different departments in winter and summer, and the median diameter of fungal conidia was less than 3.19 μm. The dominant fungal genus in the wards during winter and summer were basically the same, and there was no significant difference compared to wards in other inpatient buildings. The current study indicates that more attentions should be paid to the increasing of filtration efficiency of fungal conidia particle sized from 1.1~4.7 μm, and appropriate antifungal and sterilization drugs, equipments and methods should be selected in the maintenance of daily hygiene, including the operation and management of the air conditioning systems in the inpatient wards.

Investigation of droplet splashing behavior during oblique jet impact onto a wall

For the issue of jet impingement on the wall in industrial cooling processes, an experimental setup based on high-speed photography for oblique jet impingement onto the wall was constructed. The experimental focus was on the study of liquid droplet splashing behavior after oblique jet impingement on the wall, discussing the liquid droplet splashing behavior under three jet impingement modes: Rayleigh regime, first wind-induced regime, and secondary wind-induced regime. By employing methods such as trajectory imaging and particle image velocity for liquid droplet parameter image measurement, obtaining the particle size, velocity, and distribution of splashed droplets after oblique jet impact on walls under different working conditions. The impact of jet impingement velocity and angle on droplet splashing parameters was analyzed. The results showed that when the impingement point is before the breakup length, with increasing flow velocity, the surface wave of the liquid column, and the spreading liquid film became more pronounced, but the loss of liquid-phase components due to splashing was relatively small. When the impingement point is after the breakup length, the secondary breakup resulting in a “crown”-shaped liquid film after droplet impingement leads to a significant loss of liquid-phase components through splashing. As the inlet velocity of the jet increases, there is a decreasing trend in droplet size and an increasing trend in droplet velocity. With an increase in jet angle, there is a decreasing trend in droplet size and velocity. Based on the concentration, size, and velocity distribution characteristics of splashing droplets, the area after oblique jet impingement on the wall can be divided into the impingement zone, low-concentration low-velocity zone, high-concentration high-velocity zone, and lateral splashing zone. This has significant implications for understanding the splashing mechanism after oblique jet impingement on the wall and optimizing operating conditions.

Quantitative expression of LNAPL pollutant concentrations in capillary zone by coupling multiple environmental factors based on random forest algorithm

Quantitative expression of LNAPL pollutant concentrations in capillary zone by coupling multiple environmental factors based on random forest algorithm

Spatiotemporal Distribution Characteristics of Ground-level-ozone and Its Relationship with Meteorological Conditions in a Representative City in the Bohai Rim from 2017 to 2022

In recent years, ground-level-ozone（O3） pollution in urban areas in the Bohai Rim has attracted wide attention. Based on the analysis of the spatiotemporal distribution characteristics of O3 concentration in Dongying, a representative city in the Bohai Rim from 2017 to 2022, the effects of meteorological factors and sea-land breeze circulation on O3 concentration were evaluated. The results showed that： ① From 2017 to 2022, the annual assessment value of O3 concentration in Dongying showed a fluctuating upward trend, and the pollution days with O3 as the primary pollutant increased. O3 pollution mainly occurred in spring, summer, and autumn, with the most severe O3 pollution episodes typically occurring in May and June, and the duration of O3 pollution season tended to be longer. The monthly variation in the daily maximum 8-h average ozone （MDA8 O3） presented a bimodal distribution, with significant increases in the 5th and 25th percentiles, and the spatial distribution was "high in the north and south, low in the middle." In addition, the nocturnal O3 concentration in recent years in Dongying also showed a significant increase trend. ② Meteorological factors greatly influenced O3 concentration in Dongying. When the temperature was greater than 30℃, the relative humidity was less than 50%, and the wind direction was south-southwest or east-northeast, a high O3 value was more likely to occur. Meteorological factors contributed 30% of the MDA8 O3 variation in Dongying during the study period. In the case of moderate and severe O3 pollution, the contribution of meteorological factors to the change in MDA8 O3 could be as high as 40%. ③ To some extent, sea-land breeze contributed to the occurrence of MDA8 O3 exceeding the secondary standard limit value of the National Ambient Air Quality Standard. In the afternoon, the hourly concentration of O3 during the sea-land breeze days was approximately 20 μg·m-3 higher than that during the non-sea-land breeze days. On the days of moderate and severe O3 pollution, the O3 concentration during the sea-land breeze days from 10：00 to 16：00 was higher than that during non-sea-land breeze days, and the O3 concentration was also at a high level from 20：00 to 23：00 on sea-land breeze days. In the O3 pollution season, the sea-land breeze could significantly affect the O3 level in coastal cities, which could bring significant challenges for O3 pollution prevention and control in this region. In the future, cities in the Bohai Rim need to further strengthen regional joint prevention and control of O3 pollution and increase emission reduction efforts of nitrogen oxides and volatile organic compounds. This strategy could effectively lower pollutant concentrations within the land breeze air mass, consequently reducing the impact of the sea breeze air mass on air quality in cities in the Bohai Rim.

Heat and mass transfer analysis of non‐miscible couple stress and micropolar fluids flow through a porous saturated channel

AbstractThis study examines the flow rate, Bejan number transportation, concentration distribution and thermal characteristics of an immiscible couple stress‐ micropolar fluids within a porous channel. The authors focus on the effects of heat radiation and an angled magnetic field on the thermal dispersion, concentration distribution and entropy formation of two different types of incompressible immiscible micropolar and couple stress fluids inside a porous channel. Here, the static walls of the channel are isothermal, and the pressure gradient in the flow domain's entrance zone is constant. In this flow problem, we tried to simulate thermal radiation in the energy equation by applying Rosseland's diffusion approximation. To solve the problem, the authors have used no‐slip conditions at the channel's immovable walls, a continuity of temperature profile, shear stresses, thermal flux, linear velocity, and micro‐rotational velocity over the fluid‐fluid interface. The equations that govern the flow of immiscible fluids are solved using a well‐defined methodology and both the temperature and flow field are then evaluated using a closed‐form solution. The mathematical results of the thermal distribution and flow velocity are used to derive the Bejan number distribution and the entropy generation number. Graphical discussions are used to illustrate the impact of different emerging factors on the model's flow and thermal properties, which describe the major impact of the proposed model. These variables involve the micropolarity parameter, Reynolds number, inclination angle parameter, radiation parameter, and Hartmann number. The outcomes of the present models are corroborated by previously established results available in the literature.

Spatial and temporal distribution characteristics of dust concentration based on satellite in mining area.

The spatial and temporal distribution patterns of dust concentration in the Pingshuo mining area and urban area were analyzed utilizing satellite data. The results indicate that the correlation coefficients of the average PM2.5 and PM10 concentration retrieved by satellite in Shuozhou City are 0.88 and 0.63, respectively, and the satellite inversion data demonstrate high reliability. The spatial distribution of dust concentration in the Pingshuo Mine area is elevated during winter and spring, with significant dust accumulation in winter. The pollution phenomenon in the Pingshuo mining area was pronounced from January to March, and the air quality deteriorated significantly. The correlation analysis of dust concentration between the city and the mining area reveals a marked spatial discontinuity at the boundary between the city and the mining area, indicating that the mining area is not the primary cause of the increase of dust concentration in the urban area, and changes in dust concentration within the mining area exert no significant impact on the urban area. The research results possess significant implications for dust control in both the mining and urban areas.

Study on the Typical Environmental Factors in the Middle Part of Zhoushan Fishery Based on HY-1C/D and Other Multi-Source Data

This study utilizes satellite data, including HY-1C/D, along with reanalysis data, to unveil the typical environmental characteristics of the sea surface in the middle of Zhoushan fishery. The article addresses three main issues. The first one is the development of an ocean primary productivity (OPP) inversion algorithm model. The second one is the study of chlorophyll-α (Chl-α) concentration and OPP distribution characteristics in Zhoushan fishery using China’s domestically produced ocean satellite HY-1C/D CZI data. The last one is the revelation of the characteristics of typical environmental factors on the sea surface at Zhoushan fishery by combining HY-1C/D with multi-source data. The results show the following: (1) The middle part of Zhoushan fishery exhibits significant seasonal and regional variations in Chl-α concentration and OPP. Chl-α concentration ranges mainly between 0.2 and 2.9 µg/L, with higher concentrations in spring and summer and lower Chl-α concentrations in autumn and winter. Spatially, Chl-α concentration gradually decreases from west to east. The OPP in the study area ranges from 100 mg·m−2d−1 to 1000 mg·m−2d−1, with high OPP values distributed on the western side, ranging from 400 mg·m−2d−1 to 1000 mg·m−2d−1, and gradually decreasing seaward. The highest OPP occurs in summer and the lowest in winter. (2) The correlation analysis between Chl-α concentration and OPP revealed a strong positive relationship. Consequently, this study developed an empirical model for estimating OPP based on Chl-α concentration and validated its feasibility. The model applies to areas with Chl-α concentrations ranging from 0.2 to 4 µg/L. (3) The convergence of freshwater injection, multiple ocean currents, and seasonal upwelling in the study area brings about a rich supply of nutrients. Additionally, the region is characterized by suitable conditions, including optimal Chl-α concentrations, OPP, SST, salinity, currents, and geological water depths. The synergistic effect of these factors together contributed to the formation of Zhoushan fishery.

Health Risk Assessment of Heavy Metals in Soils of a City in Guangdong Province Based on Source Oriented and Monte Carlo Models

Taking a city in Guangdong Province as the research area, the concentration and spatial distribution characteristics of heavy metals in the surface soil were studied to clarify the situation of soil heavy metal pollution and priority control factors, providing basic data for the prevention and control of soil heavy metal pollution in the city. The content characteristics of heavy metals in 221 soil samples in the city were analyzed, and the potential health risk assessment and source analysis were carried out through the Monte Carlo model, the potential health risk assessment (HRA) model, and the PMF receptor model. It was found that heavy metals ω(As), ω(Hg), ω(Cd), ω(Pb), ω(Cr), ω(Cu), ω(Ni), and ω(Zn) in the soil of the city were 18.16, 0.43, 1.46, 68.57, 98.34, 64.19, 26.53, and 257.32 mg·kg-1, respectively, with a moderate to high degree of variation. Except for Ni concentration, the soil concentrations of other heavy metal elements exceeded the background values of soil in Guangdong Province to a certain extent, and the concentrations of Cd and Zn exceeded the national secondary standards, resulting in severe heavy metal pollution; the main sources of heavy metals were industrial sources, and natural parent materials, lead battery manufacturing, transportation, artificial cultivation, and pesticide and fertilizer inputs also had an undeniable impact on the accumulation of heavy metals in the soil. Heavy metals in the soil had a certain degree of tolerable carcinogenic health risk for both children and adults, whereas non-carcinogenic risks could be ignored. The potential health risk of children was greater than that of adults, and the main exposure route was through oral intake. The input sources of pesticides and fertilizers and As should be the main controlling factors for the health risks of heavy metals in the city's soil, followed by mixed sources and Cr. There were differences in the spatial distribution characteristics and relative pollution levels of heavy metals, and it is necessary to deepen zoning monitoring and control, strengthen soil pollution prevention and control, and reduce human input of heavy metals in soil.

Adaptive state-of-health temperature sensitivity characteristics for durability improvement of PEM fuel cells

Adaptive state-of-health temperature sensitivity characteristics for durability improvement of PEM fuel cells

丘陵山地果园单轨式防霜机的仿真与试验

In order to solve the problems of artificial operation, high labor intensity and low efficiency of frost prevention in hilly orchards, this study takes hilly orchards as the research object. Based on the agronomic requirements of frost prevention in hilly orchards, a smoke anti-frost machine based on the transport track of hilly orchards is designed. With the help of Fluent software, the spatial and temporal distribution characteristics of smoke mass concentration and temperature in the process of smoke diffusion are simulated and analyzed based on the discrete phase model. The results show that the smoke continues to erupt at a speed of 6 m / s, and the plume volume gradually increases. After 9 s, the smoke reaches a stable diffusion state. Based on the established smoke diffusion simulation model, the orthogonal test analysis of the working parameters at the smoke outlet of the frost-proof machine was carried out with the temperature increase near the canopy of the fruit tree as the index. The results showed that the best combination of working parameters at the smoke outlet of the frost-proof machine was the smoke outlet speed of 10 m / s, the smoke outlet angle of 60 °, and the smoke outlet diameter of 140 mm. The field test results show that the frost-proof machine can continuously operate for 0.5 h at a running speed of 0.6 m / s, and the temperature in the height range of 1.5 m to 4 m in the working area can be increased by about 1.7 ° C. This study is of great significance to reduce the frost disaster loss of hilly orchards and improve the economic benefits of hilly orchards.

Experimental and numerical study on mixture concentration distribution and ignition characteristics of biodiesel/n-butanol dual-fuel spray impingement in inert and combustion environments

Experimental and numerical study on mixture concentration distribution and ignition characteristics of biodiesel/n-butanol dual-fuel spray impingement in inert and combustion environments

The concentration estimation for ensemble of NV– color centers with spin coherent manipulation

The concentration and distribution of negatively charged nitrogen-vacancy color centers (NV−) directly affect the sensitivity and resolution of quantum sensing. In this paper, a simple method is proposed to estimate the concentration of the ensemble of NV− centers with spin coherent manipulation. The stray fluorescence is eliminated by separating the fluorescence near the NV− zero-phonon line. By introducing a single NV− fluorescence quantitative model, the number of NV− centers in the diamond under test can be obtained. The average concentration of the ensemble of NV− centers in the sample can be obtained by combining the detection volume. Compared with the results measured by electron spin resonance, the concentration of NV− centers measured by our method can be verified, and the maximum error between the two methods is less than 4.3%. The results show that the method provides an effective reference for accurately characterizing the concentration distribution characteristics of the NV− ensemble.

Pollution Characteristics，Sources，and Secondary Generation of Organic Acids in PM2.5 in Zhengzhou

Organic acids in atmospheric particulate matter are widely involved in various physical and chemical reactions in the atmosphere and contribute greatly to the formation of secondary organic aerosols and haze pollutions. Therefore， the concentration distribution characteristics， sources， and secondary formation of organic acids in particulate matter are of great significance for further investigation of organic aerosols and their secondary transformation. Fine particulate matter （PM2.5） samples were collected in Zhengzhou， and three types of organic acids， including dicarboxylic acids， fatty acids， and resin acids， were analyzed to explore their species distribution， seasonal variations， source contribution， and secondary generation. Malonic acid （di-C3） and succinate acid （di-C4） were the most abundant in the identified dicarboxylic acids， which showed obvious seasonal variations in the order of summer > autumn > winter > spring. Fatty acids had the highest concentration in winter and the lowest concentration in spring， showing obvious bimodal advantages， with the most abundant compounds being palmitic acid and stearic acid （C18）. Principal component analysis and multiple linear regression （MLR） were used to analyze the source of organic acids in PM2.5 in Zhengzhou； the results showed that 35% of the organic acids came from combustion and traffic sources， 24% from cooking sources， 23% from secondary formation， and 17% from natural sources. The ratios of the selected marker species （i.e.， di-C3 / di-C4， F/M， and C18：1 / C18） were used as tracers for the secondary formation of the organic aerosol and its aging process. The results showed that the photochemical reaction was intense in summer， and the proportion of organic aerosol aging or secondary production was high， whereas the photochemical reaction was weak in winter， and the aging degree of organic aerosol was low. Correlation analysis and MLR were used in combination to quantify the relative contribution of gas-phase oxidation and liquid-phase oxidation to dicarboxylic acid formation， and the results showed that gas-phase oxidation played a dominant role in the sampling period （accounting for 58%）， especially in summer （61%）.

The Spatio-Temporal Distribution Characteristics of Carbon Dioxide Derived from the Trajectory Mapping of Ground Observation Network Data in Shanxi Province, One of China’s Largest Emission Regions

In this study, the trajectory mapping domain-filling technology, which can provide more reliable statistical estimates of long-lived gas concentrations in a broader geographical area based on limited station data, is used to map the CO2 concentration data of six ground observation stations to the entire Shanxi Province. The technology combines a dynamical model of the atmosphere with trace gas observations, combining forward and backward trajectories to greatly expand the information on long-lived CO2 gas concentrations over a trajectory path. The mapped results show good agreement with the observation results, which reveals the generalizability of the trajectory mapping domain-filling technology. The results show that the spatio-temporal distribution characteristics of CO2 concentration in the entire Shanxi region is significant: during the five years, the provincial average CO2 concentration exhibits an overall increasing trend. The CO2 concentration increases from the north to the south across the province. Influenced by the economic growth rate and COVID-19, there are differences in the annual variation characteristics of the CO2 concentration across the entire province, with the highest year-on-year growth in 2019 and a year-on-year decrease in 2020. The increasing rate of the CO2 concentration in the northern low-value areas is faster than that in the southern high-value areas. Overall, there is a decreasing trend in the CO2 concentration growth from the north to the south in the entire province. There are seasonal differences in the CO2 concentration distribution across the entire province. The CO2 concentration and amplitude are higher in autumn and winter than they are in spring and summer. This study can provide scientific support and methodological reference for the spatio-temporal distribution characteristics analysis of GHGs at the provincial–regional scale, as well as at the national and global scales.