Soil Pollution Control Research Articles

Evaluation of Some Potentially Toxic Elements and Associated Ecological and Health Risks in Topsoil Samples Adjacent to an Industrial Zone in Turkey.

Potentially toxic element (PTE) pollution as a result of industrial activities remains a global problem that poses serious threats to human and ecological health. PTEs (Al, Fe, Ti, Mn, V, Zn, Cu, Cr, Ni, Pb, Co, and As) are metals or metalloids with biological toxicity. This study analyzed the concentrations of these PTEs and the physicochemical properties of topsoil samples collected from areas near industrial districts in the Samsun province of Turkey to evaluate ecological and health risks, estimating various indexes. The average concentrations of Al, Fe, Ti, Mn, V, Zn, Cu, Cr, Ni, Pb, Co, and As analyzed in 23 topsoil samples by energy-dispersive X-ray fluorescence spectrometry were found as 93,822, 82,410, 6623, 1642, 406, 278, 207, 149, 78, 68, 32, and 10 mg/kg dry weight, respectively. Zn, Cu, Cr, Ni, Pb, and Co levels exceed the maximum contaminant levels in the Turkish Regulation on the Control of Soil Pollution. The average pH values, organic matter, total organic carbon, and nitrogen measured in soil samples were 7.14, 6.11, 0.96, and 0.04%, respectively. The ecological and health evaluation reveals that the studied area is polluted with V, Cu, Zn, As, Ni, and Pb, which may pose a risk to people living in settlements near the industrial district.

Application and Research Progress of Biochar in Environment Pollution Control

Biochar is a carbon-rich material with a wide range of raw materials, low cost, and environmental friendliness. It has a range of advantages such as high porosity and rich surface functional groups. Recently, the application of biochar to control environmental pollution and to improve soil quality have become increasingly widespread. To systematically summarize the application status, efficiency, shortage and development prospects of biochar in environmental pollution control, this article concludes the viewpoints from resent research of biochar materials in marine oil, soil pollution control and industrial wastewater, and made the prospect of biochar materials application in the environmental pollution control and remediation.

Content, Sources, and Ecological Risk Assessment of Heavy Metals in Soil of Typical Karst County

Soil heavy metals in karst areas have obvious high background value characteristics. Conducting county-level soil heavy metal ecological risk assessment and identifying heavy metal sources in karst areas are of great significance for soil pollution control and land resource management. Taking Pingguo City, a typical karst county in Guangxi Province, as the study object, 3 151 surface and deep soil samples were collected using the grid method and combined to form 785 analytical samples. The contents of eight heavy metal elements, including As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, were determined. The content characteristics and sources of heavy metals were analyzed using statistical analysis, interpolation analysis, factor analysis, and the absolute principal component-multiple linear regression model （APCS-MLR）. Using the content of heavy metal elements in deep soil （150-200 cm） as background values, the ecological risk assessment of heavy metals in surface soil （0-20 cm） in the study area was conducted using the geo-accumulation index （Igeo） and potential ecological risk index （RI） methods. The results showed that the average content of heavy metal elements in the deep soil of the study area was significantly higher than the background value of the C layer soil in Guangxi Province, and the average content of heavy metal elements in the surface soil was significantly higher than the background value of the A layer soil in Guangxi Province. The spatial distribution of soil heavy metal element content generally showed the characteristics of high in karst areas and low in non-karst areas. The main sources of As, Cr, Ni, Pb, and Zn were soil parent materials, with contribution rates of 74.36%, 84.59%, 93.69%, 79.67%, and 78.17%, respectively. The main sources of Cd were soil parent material sources and unknown sources, with contribution rates of 37.33% and 31.05%, respectively. The main sources of Cu were soil parent materials and unknown sources, with contribution rates of 59.07% and 40.23%, respectively. The main sources of Hg were tectonic activity and mineralization, as well as unknown sources, with contribution rates of 52.49% and 30.65%, respectively. The geo-accumulation index （Igeo） showed that the surface soil was mainly polluted by Cd, with mild or above pollution accounting for 47.78%. The potential ecological risk index （RI） showed that the proportion of surface soil heavy metal comprehensive potential ecological hazards with mild, moderate, strong, and very strong levels was 80.78%, 14.97%, 2.51%, and 1.64%, respectively.

Study on Soil Pollution Control and Land Ecological Restoration Technology

This paper discusses the present situation and development trend of soil pollution control and land ecological restoration technology. Soil pollution mainly comes from industrial emissions, excessive use of pesticides and fertilizers and improper treatment of municipal garbage, which poses a threat to agriculture, human health and ecological balance. Treatment technologies include engineering remediation (such as soil replacement and water washing), physical-chemical remediation (such as solidification-stabilization, leaching, etc.), and biological remediation (using microorganisms, plants and animals). Land ecological restoration emphasizes integrity and sustainability, and adopts various methods such as plant and microbial restoration. In addition, prevention and control strategies and policy suggestions are put forward, including strengthening waste treatment standards, rational use of pesticides and fertilizers, and promoting waste classification. It is also suggested to establish a sound legal system for soil pollution prevention and control and raise public awareness of environmental protection.

Assessment of Human Health Risk Caused by Heavy Metals in Kiln Dust from Coal-Fired Clay Brick Factories in Türkiye

AbstractHeavy metal (HM) pollution from natural processes and different anthropogenic activities pose significant human and environmental health risks because of their stability, non-degradable properties, and high toxicity. HM released into the air in the form of dust can enter the human body via ingestion, inhalation, and dermal contact. Keeping in mind the significance of estimating the risk from HM in different environments, the carcinogenic and non-carcinogenic health risks to workers caused by HM in kiln dust (KD) samples collected from coal-fired clay brick factories in the Western Black Sea Region of Türkiye were assessed for the first time in this study. The concentrations of major and minor oxides and HMs in the collected KD samples were analyzed using energy-dispersive X-ray fluorescence spectrometry. The average concentrations of Fe, Mn, Cr, Ni, V, Zn, Cu, As, Co and Pb analyzed in thirty-three KD samples were determined as 65444, 768, 251, 249, 248, 122, 60, 52, 42 and 16 mg/kg dw, respectively. The average levels of Ni, As, Cr, Co and Cu exceed the maximum contaminant levels recommended in the Turkish Regulation on Control of Soil Pollution. Carcinogenic and non-carcinogenic human health risk assessments for workers via three exposure pathways were carried out, estimating the hazard index (HI) and total carcinogenic risk (TCR) index, respectively. The HI values (< 1) revealed no possible non-carcinogenic health risk due to exposure to all HMs in the studied KD samples. The average TCR value revealed that the potential cancer risks for Ni, As, Cr, and Pb were slightly above the safe limit and required monitoring and further investigation for these HMs.

Improved mapping of heavy metals in agricultural soils using machine learning augmented with spatial regionalization indices

The accurate spatial mapping of heavy metal levels in agricultural soils is crucial for environmental management and food security. However, the inherent limitations of traditional interpolation methods and emerging machine-learning techniques restrict their spatial prediction accuracy. This study aimed to refine the spatial prediction of heavy metal distributions in Guangxi, China, by integrating machine learning models and spatial regionalization indices (SRIs). The results demonstrated that random forest (RF) models incorporating SRIs outperformed artificial neural network and support vector regression models, achieving R2 values exceeding 0.96 for eight heavy metals on the test data. Hierarchical clustering for feature selection further improved the model performance. The optimized RF models accurately predicted the heavy metal distributions in agricultural soils across the province, revealing higher levels in the central-western regions and lower levels in the north and south. Notably, the models identified that 25.78 % of agricultural soils constitute hotspots with multiple co-occurring heavy metals, and over 6.41 million people are exposed to excessive soil heavy metal levels. Our findings provide valuable insights for the development of targeted strategies for soil pollution control and agricultural soil management to safeguard food security and public health.

Spatiotemporal interpretable mapping framework for soil heavy metals

Mapping the spatiotemporal distribution of soil heavy metals is a prerequisite for soil pollution prevention and control. However, current mapping methods make it difficult to balance robustness and interpretability. In this study, we proposed a spatiotemporal interpretable mapping framework for soil heavy metals and conducted a case study of soil cadmium (Cd) in cropland of the Poyang Lake region in China. The results showed that the average soil Cd concentration increased significantly (p < 0.01) from 0.13 mg/kg in 1983 to 0.19 mg/kg in 2010. Soil Cd in 1983 was mainly controlled by human activities and topography, whereas it was jointly driven by human activities, topography, and climate in 2010. In addition, the framework revealed the spatial distribution of soil Cd and their uncertainties at a 12.5-m resolution in 1983 (R2 = 0.94) and 2010 (R2 = 0.97). The top three covariates in 1983 were nighttime-light, PM10, and land surface temperature (day), whereas those in 2010 were mean annual minimum temperature, gross domestic product, and industrial enterprises, with Shapley additive explanation (SHAP) values of 0.44, 0.42, and 0.27, and 0.31, 0.11, and 0.09 mg/kg, respectively. By integrating machine learning, variable and model selection, and the SHAP module, the proposed framework achieves a balance between the robustness and interpretability in mapping the spatiotemporal distribution of soil Cd, going beyond the limitations of the classical statistical “smoothing effect” and the artificial intelligence “black box.” Our study emphasizes the importance of considering time, space, models, variables, and mechanisms in digital soil mapping, which will enable more accurate and scientific predictions of soil contaminants across time and space.

Revolutionizing Agriculture with Nanotechnology: Advances, Applications, and Sustainability Considerations

The integration of nanotechnology into agriculture has garnered significant interest due to its potential to revolutionize agricultural practices. This paper explores the application of nanotechnology in crop protection, nutrient delivery, soil management, and environmental sustainability. Nanopesticides and nanofertilizers represent notable advancements, offering enhanced efficacy, reduced environmental impact, and improved targeted delivery of active ingredients. Nanomaterials such as nanoparticles and nanocapsules encapsulate nutrients and agrochemicals, ensuring gradual release and optimized plant uptake. Nanosensors, based on materials like carbon nanotubes and quantum dots, enable real-time monitoring of soil health, crop growth, and environmental conditions, facilitating precision agriculture. Nanomaterials also play a role in soil remediation and pollution control by degrading pollutants and enhancing soil fertility. Additionally, nanobiotechnology offers eco-friendly solutions for pest and disease management through nanoscale delivery systems for biocontrol agents and plant vaccines. Despite the transformative potential of nanotechnology in agriculture, considerations of safety, regulatory oversight, and ethical implications are essential. Interdisciplinary collaboration and stakeholder engagement will be crucial to harness the full benefits of nanotechnology for sustainable agriculture.

Effects of Four Amendments on Cadmium Bioavailability and Enzyme Activity in Purple Soil

In this study, the effects of four types of amendments on effective Cd and Cd content in different parts of prickly ash soil and soil enzyme activity were studied, which provided scientific basis for acidification improvement of purple soil and heavy metal pollution control. A field experiment was conducted. Six treatments were set up:no fertilizer (CK), only chemical fertilizer (F), lime + chemical fertilizer (SF), organic fertilizer + chemical fertilizer (OM), biochar + chemical fertilizer (BF), and vinasse biomass ash + chemical fertilizer (JZ). Soil pH; available Cd (DTPA-Cd); Cd content in branches, leaves, shells, and seeds of Zanthoxylum; as well as the activities of catalase (S-CAT), acid phosphatase (S-ACP), and urease (S-UE) in different treatments were studied, and their relationships were clarified. The results showed following:① The two treatments of vinasse biomass ash + chemical fertilizer and lime + chemical fertilizer significantly increased soil pH (P &lt; 0.05) to 3.39 and 2.25 units higher than that in the control, respectively. Compared with that in the control treatment, the content of available Cd in soil under vinasse biomass ash + chemical fertilizer and lime + chemical fertilizer treatment decreased by 28.91 % and 20.90 %, respectively. ② The contents of Cd in leaves, shells, and seeds of Zanthoxylum were decreased by 31.33 %, 30.24 %, and 34.01 %, respectively. The Cd enrichment ability of different parts of Zanthoxylum was different, with the specific performances being leaves &gt; branches &gt; seeds &gt; shells. Compared with that of the control, the enrichment coefficient of each part of Zanthoxylum treated with vinasse biomass ash + chemical fertilizer decreased significantly(P &lt; 0.05)by 27.54 %-40.0 %. ③ The changes in catalase and urease activities in soil treated with amendments were similar. Compared with those in the control group, the above two enzyme activities were significantly increased by 191.26 % and 199.50 %, respectively, whereas the acid phosphatase activities were decreased by 16.45 %. Correlation analysis showed that soil available Cd content was significantly negatively correlated with soil pH value(P &lt; 0.01), S-CAT and S-UE enzyme activities were significantly positively correlated with soil pH(P &lt; 0.01), and the soil available Cd content was significantly negatively correlated (P &lt; 0.01); the S-ACP enzyme showed the complete opposite trends. The application of lime and vinasse biomass ash to acidic purple soil had the most significant effect on neutralizing soil acidity. It was an effective measure to improve acidic purple soil and prevent heavy metal pollution by reducing the effective Cd content in soil and improving the soil environment while inhibiting the absorption and transfer of Cd in various parts of Zanthoxylum.

Application of Biochar-Based Catalysts for Soil and Water Pollution Control

Application of Biochar-Based Catalysts for Soil and Water Pollution Control

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.

Morphological distribution and risk assessment of soil heavy metals in the Belly of the Three Gorges Reservoir area in Chongqing-A Case Study of Fengdu

The study of the morphological distribution and pollution risk of heavy metals in the hinterland of the Three Gorges Reservoir area in Chongqing can be used to provide data support for soil pollution prevention and control, ecological environment safety risk control and agricultural healthy development in the region. In this paper, Fengdu County, the hinterland of the Three Gorges Reservoir Area in Chongqing, was taken as the study area. The total amount and morphology of 8 heavy metal elements in the surface soil of agricultural land were analyzed and determined. The geocumulative index method was used to evaluate the pollution degree. The risk assessment coding method is used to evaluate the potential risk level. The results showed that the average contents of heavy metal elements As, Hg, Cu and Cr in the soil in the study area were relatively low. The average contents of Cd, Zn, Pb and Ni were higher than those in the Three Gorges Reservoir area. The mean value of Cd content was 1.71 times that of the background value. Cd in the soil heavy metal form is dominated by ion exchange state. The proportion of carbonate-bound state and iron-manganese bound state is relatively high. The proportion of bioavailable state was 46.36%, and the biological activity was strong. The other elements are mainly in the stable residue state. The results of the geoaccumulation index method showed that Cd was mainly mild pollution level. The other elements are mainly clean and pollution-free levels. The evaluation results of the risk assessment coding method showed that the risk of Cd contamination was the highest, and the risk of contamination of other elements was relatively low. On the whole, there is a certain degree of potential pollution risk in the soil Cd in the study area. Attention needs to be paid to the prevention and control of Cd.

The factors affecting microplastic pollution in farmland soil for different agricultural uses: A case study of China

Microplastics (MPs) accumulation in agricultural soil seriously affects soil quality and grain production, and endangers ecological environment and human safety. The factors contributing to the MPs accumulation in various agricultural land-use soils remain unclear. In this study, a meta-analysis was conducted to analyze the influence of meteorological factors. Furthermore, the accumulation process of MPs pollution in different agricultural land-use soils in China was explored. The conclusions are as follows: (1) The MPs abundance varied from 23 to 41,741 n/kg in Chinese agricultural soil. Especially, the moderate and severe pollution (≥4,000 n/kg) were found in the Yunnan-Kweichow Plateau. (2) The order of MPs abundance in soil was as follows: vegetable > orchard > food crops. Compared to non-mulching, MPs abundance in mulching food crops, vegetable, and orchard soil was approximately 1.4-fold, 11.4-fold, and 1.1-fold, respectively. (3) In orchard and food-crop soils, MPs abundance was negatively associated with rain and wind speed, but positively correlated with altitude and temperature. Whereas MPs abundance in vegetable soil was significantly positively affected with temperature, altitude, sunshine hours, wind speed, and rainfall. (4) The MPs pollution accumulation in soil was mainly dominated by mulching agricultural measures under different agricultural land-use. Meteorological factors have an indirect impact by affecting MPs fragmentation and migration. The results provide theoretical support for soil pollution control, agricultural production safety, and watershed management.

Provincial-scale Soil As Migration and Transformation and Rice Safe Planting Zoning: A Case Study of Guizhou Province

To explore the distribution characteristics of paddy soil and rice AS content, as well as the health risks of rice consumption, and to evaluate the safe planting ability of rice, 209 paddy soil samples and 1 567 groups of paddy soil-rice samples were collected, their As content and basic soil physical and chemical properties were determined, and the single-factor pollution index method was used to evaluate the pollution degree of the samples. The results showed that:① the soil of paddy fields in Guizhou Province was mainly neutral, and its fertilizer retention capacity and organic matter content were above the medium level, and the soil was relatively fertile. The range of ω(As) in paddy soil was 0.042-91.75 mg·kg-1, the geometric mean was 10.03 mg·kg-1, and the cumulative effect of paddy soil As was lower than that of natural soil As (P<0.05) by independent sample T. Compared with the screening value (0.2 mg·kg-1) of the Soil Pollution Risk Management and Control Standard for Agricultural Land (GB 15618-2018), the excess rate of soil samples was 15.37%. ② The ω (As) range of rice grain samples was 0.001-0.937 mg·kg-1, the geometric average value was 0.108 mg·kg-1, 10.21% of the rice grain samples exceeded the limit value of "Limit of Contaminants in Food (trial)" (GB 2762-2022), and the locations where the exceedances are mainly found are in the central and northern parts of Qiannan Prefecture, as well as around industrial and mining activity zones in the southern counties and districts of Zunyi. ③ As ingested through rice posed non-carcinogenic risk and carcinogenic risk for adults and children, and the impact on children was greater than that of adults. There is no strict control area for safe rice planting in Guizhou Province, and rice can be safely planted.

Early warning of heavy metals contamination in agricultural soils: Spatio-temporal distribution and future trends in the Hexi Corridor

Conducting risk and early warning assessments of heavy metals (HMs) pollution in agricultural soils holds significant importance for pollution prevention and sustainable agricultural development. Early warning studies on heavy metal contamination of agricultural soils in oases in arid zones are rare in previous studies, therefore, this study carried out spatial and temporal simulation and early warning studies on the environmental capacity of agricultural soils in the Hexi Corridor based on field monitoring data and remote sensing technology and other methods. The results revealed that agricultural soils have been affected by human activities, leaving HMs at a moderate pollution level. The mean environmental capacity indices for Cr, Ni, Cu, Zn, As and Pb showed that they all belonged to the medium-capacity state, and 7.01 % of the sampling points being overloaded and in the low capacity for As. Cr, Ni, Zn and As were found in the moderate and high capacity zones located in the study area's western part, and the spatial distribution was basically the same. HMs in the middle parts area were dominated by low to medium capacity status, which may be related to agricultural activities such as application of fertilizers and pesticides and sewage irrigation. Based on the soil dynamic capacity model, it was found that in the next 20 years, HMs showed a decrease of 70–80 %, and the soil environment dynamic capacity was smaller than both the static and existing capacity, and it showed a decreasing trend with the change of time, which indicated that the soil's capacity for pollutants in the study area would be reduced if no pollution control measures were taken. Risk warning results showed that the overall spatial distribution pattern of the probability of pollution in the study area during the next 10 and 20 years was lower in the west and the northern part of Wuwei City, and higher in the middle part. This study suggests constructing a management system of “pollution evaluation - source treatment - risk early warning” for heavy metal contaminated sites, formulating corresponding policies and early warning measures, strengthening the research and development of monitoring, remediation, and treatment technologies, and realizing the prevention and control of agricultural soil pollution and sustainable development in the study area.

Balancing the Scales: The Complex Dynamics of Soil Carbon Sequestration

At present, soil pollution is a global problem, and how to control soil pollution has become a hot topic. As an important part of soil pollution control, it is necessary to discuss the importance, advantages and disadvantages of soil carbon sequestration. In the whole process of the carbon cycle, most gases need to enter the soil to complete gas exchange. Therefore, this essay provides a comprehensive analysis of soil carbon sequestration, covering its processes, environmental and economic benefits, limitations, and technological advancements. It begins by explaining soil carbon sequestration’s role in mitigating climate change and enhancing soil health. Then it delves into the factors influencing carbon sequestration, including environmental conditions and soil characteristics. What is more, it acknowledges the process’s limitations, such as the soil’s finite carbon storage capacity and the need for widespread adoption of sustainable practices. Finally, it discusses innovative techniques in soil management and technology’s role in monitoring and maximizing soil carbon sequestration. The essay concludes by emphasizing a balanced and integrated approach for effectively using soil carbon sequestration in combating climate change.

Soil Pollution Status, Sources and Control Methods in China

Soil is the solid foundation for our survival and development. With the progress of society, our country pays more and more attention to soil pollution. Soil pollution can cause the quality and yield of agricultural products to decline, pollute groundwater and surface water resources, affect air quality, lead to soil pollution in regional areas, and cause the destruction of ecological environment and the sharp decline of biodiversity. These problems will affect China's future sustainable development and social stability, so a detailed analysis of the sources of soil pollution is conducive to analyzing the nature of pollutants and pollution methods, which plays an important role in the prevention and control of soil pollution. And to introduce to the public some new technologies of soil pollution control, new ideas and the future direction of soil remediation.

Volatile Organic Compounds (VOCs) in Soil: Transport Mechanisms, Monitoring, and Removal by Biochar-Modified Capping Layer

Volatile organic compounds (VOCs), as a primary pollutant in industrial-contaminated sites or polluted soils, cause severe damage to the soil. Therefore, a comprehensive understanding of the transport of VOCs in soil is imperative to develop effective detection means and removal methods. Among them, biochar possesses potential advantages in the adsorption of VOCs, serving as an effective method for removing VOCs from soil. This review provides an overview of the VOCs within soil, their transport mechanisms, monitoring technology, and removal approach. Firstly, the historical development of the VOC migration mechanism within the capping layer is described in detail. Secondly, the in situ monitoring techniques for VOCs are systematically summarized. Subsequently, one of the effective removal technologies, a capping layer for polluted sites, is simply introduced. Following this, the potential application of a biochar-modified capping layer for the removal of VOCs is comprehensively discussed. Finally, the major challenges in the field and present prospects are outlined. The objective of this study is to furnish researchers with a foundational understanding of VOCs, their relevant information, and their removal approach, inspiring environmental protection and soil pollution control.

Research and Application Progress of Biochar in Amelioration of Saline-Alkali Soil

Saline-alkali land， as one of the farmland problems that seriously threatens grain yield in the 21st century， is widely distributed and has great potential for development. Biochar is a relatively efficient novel soil amendment， which can play an important role in alleviating the soil acid-base barrier， soil pollution control， carbon sequestration， and fertilizer slow release and has a great prospect in promoting sustainable agricultural development. In recent years， the research and application of biochar to improve saline-alkali soil have attracted much attention. However， due to the complexity and heterogeneity of the structural components of biochar， the improvement effect of biochar on saline-alkali soil is highly uncertain， and there is also a lack of systematic summary and in-depth discussion of the key mechanisms， which limits the further popularization and application of biochar technology in the improvement of saline-alkali soil. This study comprehensively analyzed the effects of biochar on physicochemical properties， nutrient availability， and biological characteristics of saline-alkali soil； summarized the improvement effects of biochar and modified biochar on saline-alkali soil and their effects on quality and efficiency； and elucidated the possible mechanism of biochar in the improvement of saline-alkali soil. The future research prospect of biochar was discussed in order to provide reference for further research and development of green， efficient， and accurate improvement technology of biochar in saline-alkali soil and its popularization and application.

Pollution Characteristics and Risk Assessment of Polycyclic Aromatic Hydrocarbons in Soils of Guangzhou

In order to comprehensively study the pollution characteristics of polycyclic aromatic hydrocarbons （PAHs） in soils of Guangzhou， 222 topsoil samples were collected and analyzed. The ecological risk of soil PAHs pollution was evaluated using the effect interval low/median method （ERL/ERM） and the （BaP） toxicity equivalent method， and the health risk of soil PAHs pollution was evaluated using the lifelong cancer risk increment model. The source of PAHs was analyzed using the characteristic compound ratio method and PMF model. The results indicated that： the content of surface soil （∑16PAHs） in Guangzhou was 38-11 115 μg·kg-1， with an average of 526 μg·kg-1， and 16 types of polycyclic aromatic hydrocarbon monomers showed strong variation. There was a certain degree of ecological risk of PAHs in Guangzhou， and there was already a significant ecological risk of PAHs pollution in individual sampling points， which were generally in a state of mild pollution. Based on the results of the health risk assessment， the contribution rates of total cancer risk in both adults and children were presented as follows： skin contact &gt; ingestion of soil &gt; respiratory intake. The health risk of children was greater than that of adults， and the overall health risk was within an acceptable range. Source analysis showed that the main sources of soil PAHs in Guangzhou were coal （37.1%）； diesel （32%）； coking （17.3%）； and mixed sources of traffic emissions， biomass combustion， and petrochemical product volatilization （13.6%）. The overall source of soil PAHs belonged to mixed sources. The research results have enriched our understanding of the pollution status of PAHs in the surface soil of Guangzhou and are helpful in promoting soil pollution prevention and control actions.