Fluorine In Soils Research Articles

Balancing Environmental Safety and Economic Feasibility: A Review of Soil Fluorine Management Strategies in South Korea

Balancing Environmental Safety and Economic Feasibility: A Review of Soil Fluorine Management Strategies in South Korea

Efficient and simultaneous immobilization of fluoride and lead in water and tea garden soil by bayberry tannin foam loaded zirconium

Nowadays, human activities intensified the combined pollution of fluoride and lead in acidic tea garden soil. The key to eliminating this combined pollution is to immobilize pollutants simultaneously, thus preventing their migration from tea garden soil to tea trees. In this paper, the natural product bayberry tannin was employed as raw material to fabricate functional materials (TF-Zr) for simultaneous adsorption of fluorine (F) and lead (Pb) in water and soil by the reactivity of tannin with Pb2+ and the affinity of Zr with F. SEM-Mapping, EDS, FT-IR, XPS were utilized to probe the immobilization mechanisms. The results showed that TF-Zr could simultaneously and efficiently adsorb F– and Pb2+ from water with the adsorption capacity of 5.02 mg/g (Pb) and 4.55 mg/g (F). The adsorption processes were both in accordance with the proposed secondary kinetic adsorption model. Besides, the presence of F– promoted the adsorption of Pb2+ by TF-Zr. The materials were applied into tea garden soil to explore its effect on the variation of F and Pb forms in the soil. It was found that the proportion of water-soluble fluorine, exchangeable fluorine and exchangeable lead in the tea garden soil decreased significantly, while the proportion of residual fluorine and lead increased evidently, illustrating TF-Zr possessed eximious fixation effect on the highly reactive fluorine and lead in the soil and facilitated their conversion to the more stable residue state. Therefore, TF-Zr can be used for the efficient and simultaneous immobilization of fluorine and lead in water and tea garden soil.

Effect of Origin on Chemical Extractability of Fluorine in Soil and Its Consequence on Human Health Risk

Effect of Origin on Chemical Extractability of Fluorine in Soil and Its Consequence on Human Health Risk

Effects of swine manure and straw biochars on fluorine adsorption-desorption in soils.

With increasing global awareness of soil health, attention must be paid to fluorine exposure in soils, which poses a threat to human health. Therefore, this study aimed to study the fluorine adsorption characteristics of swine manure and straw biochars and their impact on fluorine adsorption-desorption in soil with batch experiments. The biochar samples originated from high-temperature anaerobic cracking of swine manure (350°C, 500°C, and 650°C) and straw (500°C). Results indicated that the adsorption of soil fluorine reached adsorption equilibrium at around 4 h after the mixing of swine manure and straw biochar. Fluorine adsorption kinetics using these biochars conformed to the quasi-two-stage kinetic model. The fluorine adsorption kinetics for biochar-treated soils conformed to the double-constant equation and the Elovich equation, and the soil treated with straw biochar showed the fastest fluorine adsorption rate. The adsorption isotherms of fluorine for biochars and biochar-treated soils could be fitted by the isothermal adsorption model of Langmuir and Freundlich. The maximal equilibrium quantity of fluorine was 73.66 mg/g for swine manure biochar. The soil, adding with 2% of swine manure biochar achieved with showed at 650°C had the smallest adsorption. This study also shows that the adsorption of fluorine by biochar gradually decreased with the increase of pH. Comparing with other factors, the mixture pH with biochars added had a significant effect on fluorine adsorption. The decreased fluorine adsorption capacities for soils treated with swine manure and straw biochars were closely related to the increased pH in soils after adding biochars. Considering the fluorine threat in soil, this study provides a theoretical basis for the application of biochars on soil fluorine adsorption.

Total Content and Mobile Forms of Halogens (Fluorine, Bromine, and Iodine) in Soils of Tuva

Total Content and Mobile Forms of Halogens (Fluorine, Bromine, and Iodine) in Soils of Tuva

Potential Ecological Risk Assessment and Source Analysis of Heavy Metals in Soil-crop System in Xiong'an New District

In order to evaluate the distribution characteristics of fluorine geochemistry in the surface soil and human health risk in Xiong'an New District, GIS spatial analysis and correlation analysis were used to analyze the depleted and enriched features and influencing factors of soil fluoride and to carry out the soil fluoride health risk assessment. The uncertainty of the health risk assessment results was studied based on the Monte Carlo stochastic simulation. The results showed that the average content of fluorine was 641 mg·kg-1, which was 1.34 times the background value of the national A-layer soil. The excess fluorine and high-grade samples accounted for more than 85%, and the overall soil fluorine content was relatively high. The average content of fluoride of the irrigation water samples was 0.85 mg·L-1, the spatial distribution characteristics of which were affected by the hydrochemical type and flow direction of shallow groundwater. The vertical spatial variation of soil fluoride, mainly affected by the vertical distribution of soil physicochemical properties such as soil organic carbon and texture, was not obvious. The depletion and enrichment of topsoil fluorine was mainly controlled by the geological background, and its spatial distribution was affected by external inputs, such as human factors (agricultural irrigation water, fertilization, and atmospheric dry and wet deposition). The soil fluoride content was significantly correlated with the iconic indicators of the geomorphological environment, including the content of Al2O3, Fe2O3, MgO, K2O, soil organic carbon (Corg.), cation exchange capacity (CEC), clay, and silt (P<0.01). The results of human health risk assessment showed that oral intake was the main exposure risk route of soil fluoride. The non-carcinogenic health risk index HQ of adults was less than 1, and the harm could be ignored. The probability of non-carcinogenic health risk exceeding the threshold for adults and children was 34.3% and 27.6%, respectively, and daily soil intake was the most sensitive parameter.

Geochemical evidence of fluoride behavior in loess and its influence on seepage characteristics: An experimental study

High background levels of fluorine in groundwater and soil in arid and semi-arid loess regions pose a severe threat to socio-economic development and human health, necessitating the evaluation of fluorine migration in loess. In this study, static leaching and dynamic seepage tests as well as scanning electron microscopy, mercury intrusion porosimetry, and X-ray fluorescence analyses were conducted using loess as the porous medium. Additionally, simulations using PHREEQC software were performed. The results indicated that the studied loess had a high background level of fluorine. Geochemical processes closely related to fluorine include dissolution of gypsum and dolomite, precipitation/dissolution of calcite and fluorite, and ion exchange between CaX and NaX. Under seepage of water with high fluorine levels, soil particles flocculated and formed aggregates; furthermore, the contact area between soil particles reduced, resulting in point-to-point contact between particles. Consequently, pores changed from small (intra- and inter-particle pores) to large (intra- and inter-granular pores) scale pores. Permeability initially decreased rapidly, then remained relatively stable, and subsequently rapidly increased with the passage of time. This was attributed to the dissolution of calcium minerals in loess, yielding Ca2+, which induced the precipitation of fluorite and promoted the dissolution of carbonates. Cation exchange and dissolution of other components were also important factors influencing permeability. The findings of this study can elucidate the coupling between loess microstructure, seepage behavior, and geochemical actions under the influence of high‑fluorine water, and are of great significance for in-situ regional research in loess areas.

Fluorine and Iodine in Soils of the Kulunda Plain

The content and distribution of fluorine (F) and iodine (I) have been studied using the example of a four soils located on the terrace of Kuchukskoye Lake in the Altai kray. Soil sections are located on various elements of the micro relief within the boundaries of the lake terrace. The textural-carbonate stratified chernozem (Calcic Chernozem (Loamic, Areninovic, Bathyraptic)) occupies the top of the micro relief. The Solonchak quasi-gleyed (Calcic Solonchak (Loamic, Sulphatic, Humic) is located in a micro-depression. The absolute difference in elevation between these soils is 1 m. Solonetz dark quasi-gleyed salted (Protosalic Solonetz (Loamic, Humic) and texture-carbonate quasi-gleyed salted (Calcic Gleyic Chernozem (Loamic, Endosalic) are confined to the slope between the Calcic Chernozem and Solonchak. The total content of halogens and their mobile forms were determined: water-soluble for F and salt-soluble for I. The content of total F in soils averaged 277.40 mg/kg (lim 59.83–541.10 mg/kg), water-soluble – 3.47 mg/kg (lim 0.04–16.45 mg/kg). Statistical calculations proved that the content of total F strongly correlates with the content of clay, carbonates and water-soluble sodium-cation, and the value of the correlation coefficient depends on the type of soil and its position on the micro relief. Water-soluble F has a high positive correlation with similar parameters in the Chernozem and in the Solonetz. The results showed that the content of total I in the studied soils is higher than in zonal soils of this territory, averages 13.61 mg/kg of soil (5.27–15.21 mg/kg) and moderately depends on the content of clay and carbonates. The influence of the soil type and its position on the micro relief was not revealed on the content of total I. The average content of salt-soluble I is 0.71 mg/kg (0.01–1.86 mg/kg). For all studied soils except Solonchak the relationship of the content of salt-soluble I with the content of clay, carbonates and water-soluble sodium cation has been established. No significant correlation between the above-mentioned parameters has been established for the Solonchak. The revealed heterogeneity of the spatial distribution of F and I in in the studied soils should be taken into account when conducting regional assessments of the status of these halogens.

Fluorine and Iodine in Soils of the Kulunda Plain

Fluorine and Iodine in Soils of the Kulunda Plain

Geo-Environmental Factors’ Influence on the Prevalence and Distribution of Dental Fluorosis: Evidence from Dali County, Northwest China

Residents living in areas with high fluorine environmental background will ingest excessive fluorine from the atmosphere, drinking water, food and other ways. Long-term effects of fluorine on the human body could cause people suffering from dental fluorosis and influence the sustainable development of the severe fluorosis areas. Previous studies have independently discussed the high fluoride environment in Dali County from the aspects of natural environment, drinking water quality and endemic fluorosis. This study carried out a detail investigation on dental fluorosis population in seven selected villages of Dali County, Shaanxi province, northwest China. The highest dental fluorosis index of 1.9 was found in Lianjia village located near the Anren depression, while the lowest dental fluorosis index of 0.0 was found in Jiaxi village near the Yellow River alluvium. Groundwater fluorine contents the range was 0.01 mg/L to 11.80 mg/L, with the highest value (2.6 mg/L) being observed in the 2nd terrace of Weihe River. The lowest groundwater fluorine content (0.8 mg/L) was observed in the Yellow River alluvium. Soil fluorine contents ranged from 1.18 mg/kg to 13.70 mg/kg, with its highest value (13.70 mg/kg) observed in Xinfeng village near the Anren depression. The lowest value of fluorine (1.18 mg/kg) was found in soil from the 1st terrace of Weihe River. As for the fluorine contents of corn, they ranged from 4.04 mg/kg to 7.72 mg/kg. The highest value (7.72 mg/kg) appeared in the 3rd terrace of Weihe River and the lowest value (4.04 mg/kg) in the 2nd terrace of Weihe River. The soil leaching was the dominant fluorine source of groundwater environment. Areas with severe dental fluorosis are located at the edge of the depression and the conjunction between steep slope and gentle slope. A poor correlation was found between the dental fluorosis index from the seven investigated villages and the corn fluorine content contrarily to the groundwater fluorine content, which positively correlated to the dental fluorosis index. Based on the obtained results, two recommendations were done to prevent and control dental fluorosis and accelerate the sustainable development in Dali County: to strengthen the use of low fluorine groundwater for drinking water supply, and to widely install the public water purifiers in the rural communities for purifying high-fluorine water to reduce the incidence of dental fluorosis in the population.

Synergistic degradation of fluorene in soil by dielectric barrier discharge plasma combined with P25/NH2-MIL-125(Ti)

Plasma techniques to degrade pollutants are generally more efficient than conventional methods, but exist some problems such as high energy consumption, incomplete degradation of pollutants, and secondary pollution caused by highly toxic intermediates. In this study, the dielectric barrier discharge plasma (DBDP) combined with the Ti-based metal organic frameworks (MOFs) catalysts (P25/NH2-MIL-125(Ti)) was used to degrade fluorene in the soil. The synergistic treatment technique used in soil remediation can realize a green and promising treatment efficiency with relatively low energy consumption. Compared with DBDP system alone, the synergetic treatment system of DBDP and P25/NH2-MIL-125(Ti) considerably increased the degradation efficiency of fluorene in the soil to above 90% at 10 min, even with a relatively low discharge voltage (5 kV). The synergistic treatment system achieved 88.8% of fluorene mineralization at 60 min. Optical emission spectroscopy and electron paramagnetic resonance spectroscopy both showed that •OH and •O2− played an important role in the synergetic treatment system. Nine main intermediates were identified using gas chromatography-mass spectrometry and Fourier transform infrared analysis. The main degradation of fluorine in soil was caused by the electronic transition of the catalytic material excited by DBDP, and finally mineralized into CO2 and H2O. The fluorene and its toxic intermediates were effectively removed. This study provides an insight for achieving high efficiency and environmentally friendly application perspective in soil remediation.

Health risk of fluorine in soil from a phosphorus industrial area based on the in-vitro oral, inhalation, and dermal bioaccessibility

Health risk of F in soil is of special concern due to the continuously elevated concentration of F in soil. However, there is still a dearth of risk assessments of F in soil based on in-vitro bioaccessibility posed by multiple exposure routes. Herein, the oral, inhalation, and dermal bioaccessibility of F in soil was firstly obtained by adapting and combining in-vitro methods, which then was introduced to remedy an information gap of a comprehensive risk of F in soil posed by a multi-exposure pathway. Combined in-vitro tests indicate the oral, inhalation, and dermal bioaccessibility of F was 13.15 ± 2.63%, 16.55 ± 2.63%, and 1.27 ± 0.73%, respectively. Plasma yielded a detoxic potential for the absorbed F after digesting in small intestine, while effects of enzymes, sweat, and food on the oral bioaccessibility of F were insignificant. Different with metals, the major dissolving phase of F was the interstitial fluid in the deep lung instead of in the alveolar macrophages intracellular environment. A potentially major release of F in the exocrine sweat was noted than in the apocrine sweat. Risk assessments based on the daily exposure incorporated with the in-vitro bioaccessibility suggested that compared with inhalation and dermal contact, oral ingestion was the main exposure route of F in soil to human. Present findings provide insights into the bioaccessibility and health risk of F in soil by multiple exposure routes, which are crucial for the risk control of F contamination in soil.

Distribution, co-existing metals, and potential health risk of fluorine in farmland soil in different anthropogenic activity dominated districts in a county-level city in Sichuan province, Southwest China, in 2015.

Continuous fluorine (F) accumulation in soil by anthropogenic activities leads to variously global environmental and health issues. Herein, 300 farmland soil samples were collected from different anthropogenic activity dominated districts for studying the distribution and related health risk of F in soils. Co-existing metal concentrations in soil samples were also analysed to evaluate the relationship between the distribution of F and metals in soil. The median value of the total F concentration of 488 mg kg-1 in the present samples was higher than the median background F concentration in topsoil in Sichuan province of China (261 mg kg-1). Concentration of water-soluble F (1.33-26.2 mg kg-1) was two or three orders of magnitude less than that of total F in soil. Levels of total and water-soluble F in soils collected from the district with longer contamination history were higher than that from other districts with shorter contamination period, indicating a historical contribution of anthropogenic activities to F accumulation in soil. Notable positive correlation between the total F and vanadium (V) concentration in soil can be partly linked to the usually negative charged form or a common source of F and V in soil (e.g. coal combustion). Compared with inhalation and dermal contact, present human exposure of F in soil was mainly caused by oral ingestion, and the health risks posed by F in soil for both children and adults were acceptable. However, considering the higher potential risk for children than adults, the accumulation of F in soil induced by anthropogenic activities should not be neglect.

Effect of urea feeding on transforming and migrating soil fluorine in a tea garden of hilly region.

The hilly region of western Sichuan is famous for producing Mengding-mountain tea in China. However, it is very easy to enrich fluorine (F) in tea, which recently raised people's concern on fluorosis. In this study, we simulated the local special climate conditions, especially the natural precipitation through column leaching experiment to investigate the effect of fertilization on F desorption from soil. The results suggested different fertilizers could greatly affect desorption of F from soil, but only urea (CO(NH2)2) could significantly and continuously promote the dissolution of F from soil. Furthermore, to reveal the effect of CO(NH2)2 on migration of F from soil to tea, field plots experiment in a tea garden was carried out. The results showed that CO(NH2)2 promoted soil acidification continuously, resulting in the increase of dissolved F and Al content in soil, which were migrated to tea in the form of F-Al complex. Therefore, the key to reducing the F content in tea is to alleviate soil acidification and reduce F-Al complex content in soil. Most importantly, with CO(NH2)2 addition, the contents of F in tea increased significantly from first bud to fifth bud in comparison with those of without CO(NH2)2, especially in 2016, indicating the accelerating and prolonging enrichment of F in tea by adding CO(NH2)2. This study would have important guidance for controlling F mitigation from soil to tea by managing fertilizers application and anthropogenic activities.

Feasibility of a Chemical Washing Method for Treating Soil Enriched with Fluorine Derived from Mica

High levels of fluorine in soil may pose health risks and require remediation. In this study, the feasibility of using a practical chemical washing method for the removal of fluorine from an enriched soil was evaluated. The chemical washing procedures were optimized through experimental analyses of various washing solutions and washing conditions (i.e., washing solution concentration, solid–liquid ratio, agitation speed, and reaction time). Additionally, the effects of techniques for improving the washing efficiency, such as ultrasonic washing, aeration, and multi-stage washing, were evaluated. Herein, among all applied methodologies, the maximum washing efficiency achieved for the total fluorine present in soil was only 6.2%, which indicated that chemical washing was inefficient in remediating this particular soil. Further sequential extraction analysis showed that the fluorine in this soil was present in a chemically stable form (residual fraction), possibly because of the presence of mica minerals. It was demonstrated that chemical washing may not be effective for remediating soils containing such chemically stable forms of fluorine. In these cases, other physical-based remediation technologies or risk management approaches may be more suitable.

Spatial variability and pollution risk assessment of soil fluorine in the core area of the Middle Route of the South-to-North Water Transfer Project

Spatial variability and pollution risk assessment of soil fluorine in the core area of the Middle Route of the South-to-North Water Transfer Project

Agroecological assessment of fluorine in soils and agricultural plants of steppe landscapes of Odessa region

The materials of long-term research of the features of the content and distribution of fluorine in southern chernozems are highlighted. The purpose of this work is to investigate the effects of irrigation and chemical meliorants on the fluorine accumulation in soils and crops. To achieve this goal, the following tasks were set: to determine the content of fluorine in soils and plants in conditions of irrigation and application of phosphorus fertilizers (phosphogypsum); to carry out ecological assessment of southern chernozems in terms of accumulation and migration of fluorine in soil, plant resistance to fluorine accumulationand translocation. The research was conducted within the irrigation areas of Odessa region. Bulk and movable forms of fluorine were determined by the potentiometric method in the southern chernozems of different reclamation state (non-irrigated, irrigated and irrigated reclaimed). The content of movable fluorine in agricultural plants was determined by the author’s method. It was established that the contest of bulk fluorine is the highest in the non-irrigated chernozems, but does not exceed the MPC. In irrigation, the number of bulk forms of fluorine decreases due to their dissolution and migration from the top layer to the depth of the soil profile. The content of soluble forms of fluorine increases significantly in all components of agrolandscape under the influence of irrigation and especially the introduction of phosphogypsum. It was determined that the combined application of phosphorous fertilizers and manure leads toa decrease of the fluorine content in soils, lysimetric waters and agricultural plants. The degree of mobility of fluorine compounds in the studied chernozems during irrigation and especially the introduction of phosphogypsum increases. The level of fluorine content in lysimetric waters and the coefficient of water migration correlate with its content in soils. A positive correlation was found between the fluorine content in the roots of maize, oats, wheat ear and soil while its absence between the content of fluorine in the stems and leaves. The introduction of mineral and organic fertilizers together enhances the ability of plants to absorb fluorine from chernozem soils. The active contamination rate for all tested plants is higher than one, which can cause their inhibition. When resuming irrigation of chernozem soils, there will be a need for increased doses of mineral, including phosphorus fertilizers. Despite the low solubility of fluorine compounds, conducted research has shown that irrigation and application of phosphogypsum significantly increases the soluble forms of fluorine, which can adversely affect the pollution of agrolandscapes and public health.

Evaluation of the bioaccumulation of mercury (Hg) and fluorine (F) in garden produce in south Benin

Objectives: The richness of the soils in metallic trace elements (MTEs) and Fluorine, which are potentially toxic elements, makes it necessary to pay attention to the risks of transfer of these elements to the food chain. The aim of this study is to evaluate the content of mercury and fluorine in soils, irrigation water and market garden products in South Benin. Methodology and Results: A total of 21 composite soil samples (0-20cm), 21 samples of irrigation water per growing area and 87 plant samples were collected. After sampling under aseptic conditions, they were sent for analysis in laboratories. The Excel spreadsheet calculated the contents and the GraphPad Prism 8.0 calculated the averages and tests of two ways. Before determining the bioaccumulation, the contents were compared to the minimum concentration referenced by international standards. All matrices were contaminated with mercury and fluorine. The minimum reference concentration (0.55mg/Kg) was higher than the average levels of the study soils in Mercury (0.11±0.1. 10-2 to 0.164±0.345 .10-3 mg/Kg) and in Fluorine (8.123±1.772 to 23.5±1.126mg/Kg). Mercury and Fluorine levels in site irrigation water were below the standards. The levels of mercury (0.46 .10-3 ±0.13 .10-4 to 0.001±0.38. 10-4 mg/L) and fluorine (0.15±0.07 to 2.17±0.41mg/L) in the irrigation water of the sites are lower than the standards, except for the Houéyiho borehole. In leaves such as amaranth, there was a very significant difference (0.001 &lt; p &lt; 0.01) at Sèmekpodji and Grand-popo. Amaranth is a leaf that is in direct contact with the chemicals used in the environment and could absorb mercury. Fluorine levels exceed the maximum recommended concentration (0.05 mg/Kg) so the vegetables are polluted with fluorine. Conclusion and application of results: In Houéyiho, a medium bioaccumulation in amaranths and carrots was observed while in chili peppers bioaccumulation was low. On the other hand, in Sèmè-kpodji and Grandpopo, a low bioaccumulation of mercury in all the vegetables was observed. Fluorine bioaccumulation is medium in amaranth and carrot at Houéyiho and Sèmè-kpodji and low in chilli peppers at both sites. While bioaccumulation is low in vegetables produced at the Grand-popo site. Key words: bioaccumulation, soil contamination, vegetable contamination, mercury, fluorine, MRC, Benin

Fluorine and white clover: Assessing fluorine's impact on Rhizobium leguminosarum.

The soil fluorine (F) concentration in New Zealand agricultural soils has increased with time as a direct result of the widespread application of phosphate fertilizer to land. Elevated soil F concentrations may potentially harm soil microorganisms, which are important for nutrient cycling and soil formation. Rhizobium leguminosarum is a N2 -fixing soil bacterium that is a fundamental component in New Zealand legume-based pastoral farming. Any impact of F on Rhizobium leguminosarum would have an adverse effect on New Zealand pasture production. In this study, F toxicity to Rhizobium leguminosarum was examined as a first step to develop F guideline values for New Zealand agricultural soils. Bottle-based experiments were conducted to examine the effect of the F- ion on Rhizobium-white clover (Trifolium repens L.) symbiosis by observing nodule morphology and growth. Results indicate that the F- concentration that causes 10% inhibition of Rhizobium respiration (IC10 ) for F- toxicity to Rhizobium leguminosarum was >100mg F- L-1 . Significant morphological changes occurred when Rhizobium was exposed to F concentrations of 500 and 1000mg L-1 . Both light and transmission electron micrographs confirmed that the Rhizobium leguminosarum-white clover interaction was not influenced by F- concentrations >100mg L-1 . The toxic F- concentration for Rhizobium leguminosarum determined in this study is orders of magnitude higher than the F- concentration in New Zealand agriculture soils under "normal conditions." There appears to be no indication of imminent risk of soil F to Rhizobium leguminosarum.

Geochemical characteristics and environmental quality assessment of fluorine in soil and water environment of Jinbei

Fluorine is a necessary trace element in humans, lack or excess can adversely affect human health. The geochemical characteristics and environmental quality of fluorine in soil and water environment of Jizhou district in northern Tianjin were studied. The results show: fluorine content in surface soil 201×10-6 ∼8545×10-6, average 757 ×10-6. The average content is the background value of surface soil in Tianjin 1.25 times twice, all over the country 1.58 times twice. In soil vertical profiles, the content of fluorine in clay soil is higher than that in sandy soil. The average groundwater fluorine content in plain area 1.50 mg/L, average mountain area 0.47 mg/L. Plain area is obviously larger than mountainous area. Over the whole district 90% the fluorine content of surface soil showed excess and high level. Proportion of groundwater samples in plain area with fluoride class IV and class V water 61.54%. Fluorine excess ratio in maize samples 26.67%. Maximum excess multiple greater than 2 times twice. Overall, the fluorine content in the surface soil and the groundwater in the plain area of North Tianjin is significantly higher, For high-fluorine areas, the fluorine content of some bulk agricultural products has exceeded the standard. We should pay attention to it.