[Spatial distribution pattern of local tumor progression analysis after microwave ablation of hepatocellular carcinoma based on three-dimensional magnetic resonance imaging]

Objective: To investigate the spatial distribution pattern of local tumor progression (LTP) for hepatocellular carcinoma (HCC) ≤5 cm after microwave ablation. Methods: A retrospective analysis was performed on 169 HCCs with matched MRI before and after ablation from December 2009 to December 2019. A tumor MRI was reconstructed using three-dimensional visualization technology. LTP was classified as contact or non-contact, early or late stage, according to whether LTP was in contact with the edge of the ablation zone and the occurrence time (24 months). The tumor-surrounded area was divided into eight quadrants by using the eight-quadrant map method. An analysis was conducted on the spatial correlation between the quadrant where the ablative margin (AM) safety boundary was located and the quadrant where different types of LTP occurred. The t-test, or rank-sum test, was used for the measurement data. 2-test for count data was used to compare the difference between the two groups. Results: The AM quadrant had a distribution of 54.4% LTP, 64.2% early LTP stage, and 69.1% contact LTP, suggesting this quadrant was much more concentrated than the other quadrants (P < 0.001). Additionally, the AM quadrant had only 15.2% of non-contact type LTP and 17.1% of late LTP, which was not significantly different from the average distribution probability of 12.5% (100/8%) among the eight quadrants (P = 0.667, 0.743). 46.6% of early contact type LTP was located at the ablation needle tip, 25.2% at the body, and 28.1% at the caudal, while the location distribution probabilities of non-early contact LTP were 34.8%, 31.8%, and 33.3%, respectively. Conclusion: LTP mostly occurs in areas where the ablation safety boundary is the shortest. However, non-contact LTP and late LTP stages exhibit the feature of uniform distribution. Thus, this type of LPT may result from an inadequate non-ablation safety boundary.

Spatial distribution characteristics, risk assessment and management strategies of tailings ponds in China

The tailings ponds (TPS) stemming from mineral resource exploitation are becoming a global challenge due to their high hazards and pollution to the surrounding area. However, previous studies on China's tailings ponds have either focused on a single or few areas, or the number of tailings ponds varies greatly. A systematic assessment of the number, distribution characteristics, potential risks and management strategies of the tailings pond in China is lacking. This study obtained the latest list of tailings ponds in China up to the end of 2022 based on official information and assessed their spatial distribution characteristics, environmental risk and management strategies simultaneously. The results demonstrated that the distribution of TPS in China is relatively clustered and multiple factors affected the spatial distribution of TPS in China, which were concentrated in areas with low economic and population density, convenient transportation, and a developed water system. The risk assessment suggested that 1803 TPS had large or significant environmental risks, which were mainly distributed in Yunnan, Hunan, Shaanxi and Jiangxi provinces. To solve the problem of tailings ponds from the source, the key point of tailings pond management in China should be adjusted from the prevention of pollution or dam break accidents to the full resource utilization of tailings. In summary, this study will provide a scientific basis for the risk control of TPS and an innovative idea for the management of other solid waste.

Spatial distribution and migration of lead and zinc and the influence of parent materials in typical paddy soils of Hunan Province, China

This study aimed to investigate the distribution and migration characteristics of lead (Pb) and zinc (Zn) in paddy soils in Hunan Province, China. A total of 343 soil samples from 63 profiles were collected from typical regions. The concentration, spatial distribution, and migration behaviors of Pb and Zn in the paddy soils were examined. The results showed that (1) the concentration ranges of Pb and Zn in the surface layer were 17.62-114.07 mg/kg and 44.98-146.84 mg/kg, respectively. (2) The content was higher in the middle and lower reaches of the Xiangjiang River basin horizontally and exhibited shallow enrichment characteristics vertically. (3) Pb migration was weaker than Zn migration, and the parent material had the most significant influence on Pb and Zn content in the bottom soil layer. The research results will clarify the characteristics of Pb and Zn contents in paddy soils in Hunan Province, further understand the horizontal distribution and vertical migration and transformation characteristics of Pb and Zn contents in paddy soils, and provide basic data for scientific rice cultivation and safe food production.

Distribution characteristics and potential ecological risk assessment of heavy metals in soils around Shannan landfill site, Tibet

At present, sanitary landfill is mainly used for domestic waste treatment in Shannan City, Tibet. However, there are few studies on heavy metals in the soil around the landfill in Shannan city. Therefore, the surrounding soil of Luqionggang landfill in Shannan City, Tibet Autonomous Region, is taken as the research object. In the study, the geo-accumulation index method, Nemerow comprehensive pollution index method and potential ecological risk index method are mainly used to evaluate the pollution and risk of heavy metals in the soil around the landfill site. The main results are as follows: The average pH value of the soil around the landfill site is 9.37, belonging to the strong alkaline range. The average values of heavy metals Hg and Ni in soil exceeded the background content, and the average contents of other heavy metals Cu, Pb, Zn, Cr, As and Cd did not exceed the background content. The average content of these eight heavy metals did not exceed the screening value of the national soil environmental quality standard. In the horizontal direction, the average content of heavy metal elements Cu, Cr, Cd, Hg and Ni is relatively high in the west. The average content of heavy metals As, Zn and Pb in the north, east and south is slightly higher than that in the west. And the farther away from the landfill, the less the soil is affected by heavy metals. The evaluation results of geo-accumulation index show that heavy metal Hg is the most affected. The average value of the comprehensive pollution index is 2.969, which is between 2 and 3, belonging to the moderate pollution level. And the west side of the landfill (downstream area) is greatly affected. The evaluation results of potential ecological hazard pollution index show that the potential risk index of single pollutants of heavy metals Cu, Pb, Zn, Cr, Ni, As and Cd belongs to low ecological hazard level, and the potential risk index of single pollutants of heavy metal Hg belongs to relatively heavy ecological hazard level. On the whole, the total potential risk coefficient belongs to medium pollution hazard degree. According to the correlation analysis, there is no significant correlation between heavy metal elements As and Hg and the other six heavy metal elements. In addition, the pollution source of heavy metal As may be mainly soil forming factors and the pollution source of Hg may be mainly human factors.

Analysis of spatial distribution characteristics and main influencing factors of heavy metals in road dust of Tianjin based on land use regression models

Land use regression (LUR) models are mainly used for the simulation and prediction of conventional atmospheric pollutants. Whether the LUR models can be expanded to study more toxic and hazardous pollutants (such as heavy metals) remains to be verified. Combined with the factors of road, land use type, population, pollution enterprise, meteorology, and terrain, the LUR models were used to simulate the spatial distribution characteristics of heavy metals in road dust and determine the main influencing factors. Samples of road surface dust were collected from 144 evenly distributed points in Tianjin, China, with 108 modelling points and 36 verification points. The R² values of the LUR models of Cd, Cr, Cu, Ni, and Pb contents were 0.301, 0.412, 0.399, 0.496, and 0.377, and their error rates were 2.72%, 4.96%, 4.64%, 8.91%, and 4.94%, respectively. The error rates of the kriging interpolation models were 3.33%, 6.50%, 5.14%, 18.30%, and 22.87%, which were all greater than those of the LUR models. The estimation effect of the LUR models was more refined than that of the kriging interpolation models. The contents of most heavy metals (except Ni) in road dust of the central area in Tianjin were generally higher than those of the surrounding areas. The heavy metal contents in road dust of Tianjin were mainly affected by road variables and meteorological variables. The LUR models were suitable for small-scale spatial prediction of heavy metals in urban road dust within urban areas.

PCDD/Fs and heavy metals in the vicinity of landfill used for MSWI fly ash disposal: Pollutant distribution and environmental impact assessment

This study focused on the syngenetic control of polychlorinated-ρ-dibenzodioxins and dibenzofurans (PCDD/Fs) and heavy metals by field stabilization/solidification (S/S) treatment for municipal solid waste incineration fly ash (MSWIFA) and multi-step leachate treatment. Modified European Community Bureau of Reference (BCR) speciation analysis and risk assessment code (RAC) revealed the medium environment risk of Cd and Mn, indicating the necessity of S/S treatment for MSWIFA. S/S treatment significantly declined the mass/toxic concentrations of PCDD/Fs (i.e., from 7.21 to 4.25 μg/kg; from 0.32 to 0.20 μg I-TEQ/kg) and heavy metals in MSWIFA due to chemical fixation and dilution effect. The S/S mechanism of sodium dimethyldithiocarbamate (SDD) and cement was decreasing heavy metals in the mild acid-soluble fraction to reduce their mobility and bioavailability. Oxidation treatment of leachate reduced the PCDD/F concentration from 49.10 to 28.71 pg/L (i.e., from 1.60 to 0.98 pg I-TEQ/L) by suspension absorption or NaClO oxidation decomposition, whereas a so-called "memory effect" phenomena in the subsequent procedures (adsorption, press filtration, flocculating settling, slurry separation, and carbon filtration) increased it back to 38.60 pg/L (1.66 pg I-TEQ/L). Moreover, the multi-step leachate treatment also effectively reduced the concentrations of heavy metals to 1-4 orders of magnitude lower than the national emission standards. Furthermore, the PCDD/Fs and heavy metals in other multiple media (soil, landfill leachate, groundwater, and river water) and their spatial distribution characteristics site were also investigated. No evidence showed any influence of the landfill on the surrounding liquid media. The slightly higher concentration of PCDD/Fs in the soil samples was ascribed to other waste management processes (transportation and unloading) or other local source (hazardous incineration plant). Therefore, proper management of landfills and leachate has a negligible effect on the surrounding environment.

Analysis of spatial structure and influencing factors of the distribution of national industrial heritage sites in China based on mathematical calculations

An in-depth analysis of the spatial distribution characteristics and overall pattern of industrial heritage sites in China provides not only a comprehensive understanding of the current status of industrial heritage but also a reference for its protection and ongoing utilization. A total of 170 industrial heritage sites that were included in the List of National Industrial Heritage of China were selected as the research objects. Their spatial structure characteristics were quantitatively analyzed based on a kernel density analysis of ArcGIS and imbalance and Gini coefficient index of function calculations. The results show that the distribution of industrial heritage sites in China presents a strong aggregation trend and a distribution pattern of four cores, six centers, and multiple scattered points. The distribution of industrial heritage sites in 34 administrative regions is extremely imbalanced. A total of 170 industrial heritage sites are distributed across 27 administrative regions; 52.35% are concentrated in the East and Southwest divisions. According to the index definitions, this research analyzed their influencing factors from perspectives of the natural and social environments. The results show that the industrial heritage sites in China are mainly distributed in traditional agricultural and commercial areas with rich natural or water transport resources. The current study of major historical events in modern China and the growth curve of industrial heritage concludes that China's industry has experienced five stages of development: Ancient, Beginning, Accelerated Development, Climax, and Slowdown. The geographical divisions and distribution of categories show colonial and socialist characteristics.

Distribution characteristics and risk assessment of TBBPA in seawater and zooplankton in northern sea areas, China

Tetrabromobisphenol-A (TBBPA) is a typical persistent organic pollutant (POP) that is harmful to the environment and organisms. It easily accumulates in organisms and is transmitted along the food chain or food web for long distances and long periods of time. The experiment was designed to assess the TBBPA pollution levels in marine environments via environmental sample testing and risk assessment. TBBPA levels in seawater and zooplankton samples at each station (n = 38) were detected, whereafter the bioaccumulation factor (BAF) and risk quotient (RQ) were calculated to evaluate the potential bioaccumulation and ecological risk of TBBPA to zooplankton, respectively. The results showed that TBBPA was widely detected in surface seawater and zooplankton samples in the Yellow Sea and Bohai Sea, with levels ranging from ND (non-detected) to 0.46 μg/L and ND to 9.83 μg/kg (wet weight), respectively. In both the Yellow Sea and Bohai Sea, the distance from the shore was one of the main factors affecting the TBBPA concentration in seawater, regardless of visibility. The BAF was significantly correlated with the TBBPA content in zooplankton samples (P < 0.01), which ranged from 372.32 to 29,941.55, indicating that TBBPA exhibits an obvious bioaccumulation risk to marine zooplankton. The ecological risk assessment indicated that TBBPA levels in seawater pose a high ecotoxicity risk to zooplankton (RQ > 1). This finding suggests that both the significant bioaccumulation of TBBPA in marine ecosystems and its potential ecological risks cannot be ignored.

Public psychological distance and spatial distribution characteristics during the COVID-19 pandemic: a Chinese context

The COVID-19 pandemic is a public health emergency, which continues to have a significant impact on the functioning of society and the public’s daily life. From the perspective of psychological distance (PD), this study used descriptive, differential, and spatial autocorrelation analysis methods to explore the cognitive distance, emotional distance, expected distance and behavioral distance of the Chinese public in relation to the COVID-19 pandemic. An analysis of 4042 valid sample data found that: (1) The event emotional distance and subject emotional distance were both furthest from the event and subject psychological distance dimensions, and anger about the event was the strongest. (2) The government was the most appealing subject in the process of pandemic prevention and control, but at the same time, the public’s sense of closeness to the government was also lower than that of the other three subjects, e.g., medical institutions. (3) Different pandemic regions showed significant differences in PD. Mean scores of PD in each risk region were as follows: High-risk regions > medium-risk regions > low-risk regions. (4) From a global perspective, no spatial autocorrelation was found in PD. However, from a local perspective, high-value regions (provinces with distant PD) are mainly concentrated in the southern regions (Guizhou, Guangxi, Hainan, Jiangxi), and low-value regions (provinces with close PD) are mainly concentrated in North China (Shanxi, Hebei, Beijing). Combined with the relevant conclusions, this paper put forward policy recommendations.

The spatial distribution characteristics of coseismic landslides triggered by the Ms7.0 Lushan earthquake and Ms7.0 Jiuzhaigou earthquake in southwest China

In recent years, a series of earthquakes have occurred in Sichuan province, southwest China. On April 20, 2013, 1013 landslides were triggered in the Lushan earthquake within the research area of 1215.87 km². On August 8, 2017, 821 landslides were induced in the Jiuzhaigou earthquake within the study area of 541.61 km². The slope, aspect, elevation, distance to the river, distance to fault, stratum lithology, curvature, and PGA as evaluation factors were chosen to research the distribution characteristics of coseismic landslides. The relationship between influence factors and distribution of coseismic landslides were analyzed using landslide area density (LAD), defined as the ratio between the coseismic landslides area and the total area under the specific classification of eight factors, and landslide number density (LND), interpreted as the number of landslides per square kilometer affected by an earthquake. Both the LAD and LND curves show the common correlations between distribution characteristics of coseismic landslides and the classification of eight factors. The high density of coseismic landslides was found at locations where the valley evolves from U-shaped to V-shaped, along slopes with an inclination between 20 and 50°. Due to the effect of river cutting erosion and human engineering activities, massive coseismic landslides appeared within the scope of 200 m from the river system. Eight hundred sixty small shallow coseismic landslides were found less than 3 km from the seismogenic fault in both earthquakes. Both concave and convex terrain has the same effect of promoting coseismic landslides. The strata of the Carboniferous and Cretaceous are more prone to coseismic landslides occurrence. In the event of another earthquake of similar magnitude in southwest China in the future, the research results can quickly predict the distribution of coseismic landslides and provide a scientific basis for emergency rescue.

The bioavailability and potential ecological risk of copper and zinc in river sediment are affected by seasonal variation and spatial distribution

River sediment is the ultimate sink for heavy metal pollution. Copper (Cu) and zinc (Zn) are consistently found at environmentally significant levels in sediments worldwide. We hypothesized that the bioavailability and potential ecological risk of Cu and Zn in river sediments may be affected by seasonal variations and spatial distribution. In this study, we tested our hypothesis using highly industrialized river sediments (Laojie River) as an example. The concentration of heavy metals, pollution indexes, and risk indexes were evaluated and multivariate statistical analyses were performed. We found that seasonal variations affect heavy metal contamination, pollution indexes, and potential ecological risk in sediments and this effect was more severe in the dry season. In addition, higher levels of metal contamination, pollution indexes, and potential ecological risk were observed midstream and downstream of the Laojie River. We found that Cu and Zn were the primary contaminants in Laojie River sediments and may originate from common anthropogenic sources. Analysis of the chemical fractions further revealed that Cu and Zn exhibited high mobility and potential bioavailability risk. In addition, a high percentage and amount of Cu and Zn were found in exchangeable fractions, suggesting they pose a great risk to aquatic organisms. Our results indicate that seasonal variations and spatial distribution affect the bioavailability and potential ecological risk of Cu and Zn in river sediments. These findings suggest that seasonal variations and spatial distribution are important parameters to consider for environmental monitoring and environmental management in aquatic environments.

Contamination features and ecological risks of heavy metals in the farmland along shoreline of Caohai plateau wetland, China

Spatial distribution characteristics of heavy metal (Cd, Pb, Cr, Cu, Zn, and Hg) contents and their ecological risks in the farmland along the shoreline of the Caohai wetland were investigated. Incubation experiments were also conducted to characterize the emission of heavy metals across soil-water interface if the farmland was reclaimed to wetland. The results showed that spatial distribution characteristics of these heavy metal contents were significantly different. Concentrations of Cd, Zn, and Hg were higher than the corresponding geochemical background levels. Ecological risk assessment suggested that the farmland along the shoreline of Caohai wetland were characterized by non-pollution or slight pollution of Pb, Cr, and Cu, moderate pollution of Cd, slight to moderate pollution of Hg, and slight pollution of Zn. Emission rates of Cd, Zn, and Hg across soil/sediment-water interface first increased, then decreased and finally reached equilibrium after the farmland soil was submersed. The contribution-rates of Cd, Zn, and Hg transferring from sediment to overlying water were calculated to be 12.7%, 14.8%, and 10.4%, respectively. We conclude that environmental issues caused by heavy metals, especially by Cd, Zn, and Hg, in the farmland along the shoreline of the Caohai wetland should be paid great attention.