Overview of Patented Technologies for Remediation of Soil Pollution

Soil, an important material basis for human activities, is an indispensable natural rasource that is difficult to regenerate. It is also an important part of human ecological environment. Currently, soil pollution has affected China＇s agricultural production and threatened human health and ecological safety, so it has been paid more attention to by the people and has become a hot spot in environmental field. Through continuous research, a variety of soil remediation patents and technologies also emerge. Here, by retrieving the main words through the website （www. soopat. corn） and Chinese patent net, types of soil pollution and remediation technologies under the authorization status of the patents were analyzed, and the major species of soil pollutants and soil remediation technologies were reviewed.

Countermeasures for Remediation of Soil Pollution in Metal Mines

Firstly,the causes and existence state of soil pollution in metal mines were discussed.Secondly,the remediation technology of heavy metal contaminated soil was introduced.Thirdly,the remediation strategies for soil pollution in metal mines were analyzed.Finally,the problems and development direction of soil pollution remediation and control in metal mines were discussed.

Investigation and Analysis of Soil Pollution of Heavy Metals(Hg,As) in Duanzhou District,Zhaoqing City

The soil heavy metals(Hg and As)in Duanzhou District of Zhaoqing City were determined by AFS200 T atomic fluorescence spectropho-tometer,and the soil environment in Duanzhou District was evaluated by several evaluation methods of soil heavy metal pollution,such as single factor index method,pollution load index method and Nemerow comprehensive pollution index method.Finally,according to the data and conclu-sions,the soil pollution situation in Duanzhou District of Zhaoqing was analyzed.The results will let more people pay attention to the changes of the environment and realize the harm of the environment,and the government can formulate a new plan conducive to the coordinated development of the environment and economy.

Control Approaches to Soil Pollution from Heavy Metals

With the continuous development of human society and economy and the continuous progress of industrial technology,more and more pollutants are discharged into the natural environment,and soil environment is also affected at the same time. Among pollutants leading to soil pollution,heavy metals have resulted in most serious soil pollution. Here,many control and restoration approaches to soil pollution from heavy metals are proposed,and characteristics and applicable conditions of various methods are compared,so as to provide theoretical references for the control and restoration of soil pollution from heavy metals in future.

The main strategies for soil pollution apportionment:A review of the numerical methods

Nowadays,a large number of compounds with different physical and chemical properties have been determined in soil.Environmental behaviors and source identification of pollutants in soil are the foundation of soil pollution control.Identification and quantitative analysis of potential pollution sources are the prerequisites for its prevention and control.Many efforts have made to develop methods for identifying the sources of soil pollutants.These efforts have involved the measurement of source and receptor parameters and the analysis of their relationships via numerical statistics methods.We have comprehensively reviewed the progress made in the development of source apportionment methodologies to date and present our synthesis.The numerical methods,such as spatial geostatistics analysis,receptor models,and machine learning methods are addressed in depth.In most cases,however,the effectiveness of any single approach for source apportionment remains limited.Combining multiple methods to address soil quality problems can reduce uncertainty about the sources of soil pollution.This review also constructively highlights the key strategies of combining mathematical models with the assessment of chemical profiles to provide more accurate source attribution.This review intends to provide a comprehensive summary of source apportionment methodologies to help promote further development.

Low-Density Microplastics in Recreational Parks of Al Ain, United Arab Emirates: Abundance, Composition, and Potential Effects on Soil Health

Microplastics (MPs) have been an emerging concern due to their harmful effects on the ecosystem and are ubiquitous in various habitats, from marine to terrestrial environments. However, studies on the presence of MPs in recreational areas are limited. One of the previous works has reported that urban recreational parks are considered “sinks” for plastic debris, including MPs. In this study, low-density MPs (LD-MPs) in soil samples collected from recreational parks of Al Ain, United Arab Emirates (UAE) were isolated by density flotation method. Results showed that these parks have varying levels of LD-MPs caused by various anthropogenic activities, such as sludge use and application of reclaimed water from wastewater treatment facilities in those areas. These plastic particles were isolated in 87% of the soil samples, with an average concentration of 1550 ± 340 MPs/kg. Predominantly, these comprised large LD-MPs (300 - 5000 μm), with red and blue being the most common colors. Fourier transform infrared (FTIR) spectroscopy identified possible synthetic polymers, including polyethylene and polypropylene. Additionally, a negative correlation was observed between LD-MP concentration and soil pH and moisture content, indicating potential adverse effects on soil health. These findings highlight the need for monitoring and managing microplastic pollution in urban recreational areas to mitigate its ecological impacts.

Effects of heavy metal pollution of highway origin on soil nematode guilds in North Shenyang, China

Soil samples were collected with distance at 5, 20, 40, 80, 160, and 320 m from the Shen-Ha （Shenyang-Harbin） Highway, Northeast China, to investigate the effect of heavy metals of highway origin on soil nematode guilds. The contents of soil Pb, Cu, Zn, and the nematode community structure were analyzed. The results showed that the contents of total and available Pb, Ca, Zn varied significantly with the different distances from the highway. Pb was the main pollutant in the soils in the vicinity of Shen-Ha Highway. The zone from 20 to 40 m away from the highway was the most polluted area. The highest abundance of soil nematodes was found at 5 m while the lowest at 20 m away from the highway. Thirty six genera of nematodes belonging to 23 families were identified. Nematode guilds having different responses to soil heavy metals were classified into four types. Soil nematode guilds may act as a prominent indicator to heavy metal pollution of highway origin.

Effects of Wastewater Discharge on Heavy Metals Pollution in Fadama Soils in Kano City, Nigeria

Objective To present the results of a research project on 6 heavy metals （Cd, Cu, Zn, Pb, Hg, and Cr） at 30 Fadama fields scattered around Kano. Methods Following a reconnaissance conducted, 30 representative Fadama lands being irrigated with wastewater were selected from zones of the city under residential, industrial, commercial, and mixed but largely residential landuses. Five additional Fadama lands not being irrigated with wastewater were selected to serve as control. Using grid sampling procedure, soil samples were selected from 0-15 cm and 20-30 cm depths and analyzed for the above listed heavy metals using atomic absorption spectrophotometry. T-test was used to compare the mean values of the metals for the Fadama lands under different landuse zones with those of the control. Results Analyses of the soil data collected showed that the metals were concentrated in higher amounts in the lower （20-30 cm） than the upper （0-15 cm） depths, which was an indication of downward movement of the metals in profile of the soils. In the two soil depths, Zn was generally the most abundant, followed by Cr, then Pb, Cu, and Cd while Hg was the least. The Fadama soils in areas of mixed landuses with industrial as the dominant ones maintained the highest concentrations of the various metals. Conclusions These results indicate clearly that the Fadama soils are significantly polluted by industrial and household wastewater and that there is a particular threat from Cr and Pb pollution. There is also evidence that the metals are accumulating at lower layers of the soil profile, suggesting that not only plants and soil, but even water bodies could be under the threat of heavy metal pollution in the area.

Relationships between soil pollution by heavy metals and melanin-dependent coloration of a fossorial amphisbaenian reptile

Melanin is the basis of coloration in many animals,and although it is often used in communication,thermoregulation,or camouflage,melanin has many other physiological functions.For example,in polluted habitats,melanin can have a detoxifying function.Melanic coloration would help to sequester in the skin the heavy metal contaminants from inside the body,which will be expelled to the exterior when the skin is sloughed.Moreover,animals should have evolved more melanic colorations in more polluted habitats(“industrial melanism”hypothesis).We examined whether the fossorial amphisbaenian reptile,Trogonophis wiegmanni,is able to eliminate heavy metals,derived from soil pollution by seagull depositions,through sloughing its skin.Our results suggest a covariation between levels of soil pollution by heavy metals and the concentration of heavy metals in the sloughed skins of amphisbaenians.This suggests that amphisbaenians may expel heavy metals from their bodies when they slough the skins.We also tested whether amphisbaenians inhabiting soils with higher levels of heavy metal pollution had darker(melanin-dependent)body colorations.However,contrary to predictions from the“industrial melanization”hypothesis,we found a negative relationship between soil pollution and proportions of melanic coloration.This contradictory result could,however,be explained because heavy metals have endocrine disruption effects that increase physiological stress,and higher stress levels could result in decreased melanogenesis.We suggest that although amphisbaenians might have some detoxifying mechanism linked to melanin in the skin,this process might be negatively affected by stress and result ineffective under conditions of high soil pollution.

Rapid Detection of Oil Pollution in Soil by Using Laser-Induced Breakdown Spectroscopy

Detection of oil pollution in soil has been carried out using laser-induced breakdown spectroscopy（LIBS）. A pulsed neodymium-doped yttrium aluminum garnet（Nd：YAG） laser（1,064 nm, 8 ns, 200 mJ） was focused onto pelletized soil samples. Emission spectra were obtained from oil-contaminated soil and clean soil. The contaminated soil had almost the same spectrum profile as the clean soil and contained the same major and minor elements. However, a C–H molecular band was clearly detected in the oil-contaminated soil, while no C–H band was detected in the clean soil. Linear calibration curve of the C–H molecular band was successfully made by using a soil sample containing various concentrations of oil. The limit of detection of the C–H band in the soil sample was 0.001 mL/g. Furthermore, the emission spectrum of the contaminated soil clearly displayed titanium（Ti） lines, which were not detected in the clean soil. The existence of the C–H band and Ti lines in oil-contaminated soil can be used to clearly distinguish contaminated soil from clean soil. For comparison, the emission spectra of contaminated and clean soil were also obtained using scanning electron microscope-energy dispersive X-ray（SEM/EDX） spectroscopy,showing that the spectra obtained using LIBS are much better than using SEM/EDX, as indicated by the signal to noise ratio（S/N ratio）.

Biodegradation of benzo[a]pyrene in soil by Mucor sp.SF06 and Bacillus sp.SB02 co-immobilized on vermiculite

Two indigenous microorganisms, Bacillus sp. SB02 and Mucor sp. SF06, capable of degrading polycyclic aromatic hydrocarbons （PAHs） were co-immobilized on vermiculite by physical adsorption and used to degrade benzo[a] pyrene （BaP）. The characteristics of BaP degradation by both free and co-immobilized microorganism were then investigated and compared. The removal rate using the immobilized bacterial-fungal mixed consortium was higher than that of the freely mobile mixed consortium. 95.3% of BaP was degraded using the co-immobilized system within 42 d, which was remarkably higher than the removal rate of that by the free strains. The optimal amount of inoculated co-immobilized system for BaP degradation was 2%. The immobilized bacterial-fungal mixed consortium also showed better water stability than the free strains. Kinetics of BaP biodegradation by co-immobilized SF06 and SB02 were also studied. The results demonstrated that BaP degradation could be well described by a zero-order reaction rate equation when the initial BaP concentration was in the range of 10--200 mg/kg. The scanning electronic microscope （SEM） analysis showed that the co-immobilized microstructure was suitable for the growth of SF06 and SB02. The mass transmission process of co-immobilized system in soil is discussed. The results demonstrate the potential for employing the bacterial-fungal mixed consortium, co-immobilized on vermiculite, for in situ bioremediation of BaP.

Status quo of soil petroleum contamination and evolution of bioremediation

Along with the rapid development of oil industries internationally,petroleum prospecting and exploitation activities are growing intensively.Especially in China,with the fastest economic growth in the world and shortage of petroleum resources,we are leading the practices of petroleum deep exploitation.Obviously,the risk of damage to the natural environment from these activities is high.Oil contamination in soils and groundwater is becoming a big issue along with pesticide pollution,which makes organic pollution prevention and control （OPPC） much more complex.In this paper,based on recent research on oil-contaminated soil at home and abroad,we make comments on the remediation technologies for polluted soil,emphasizing bioremediation techniques and degradation mechanisms in order to push forward research into bound organic pollution prevention and control （OPPC）,especially in China.

Evaluation of ecological risk and primary empirical research on heavy metals in polluted soil over Xiaoqinling gold mining region,Shaanxi,China

Soil,crop and residents'hair over Xiaoqinling gold mining region,China,which was selected as a case study,were sampled and analyzed for Hg,Cd,Pb,Cu,Cr,As and Zn concentrations.The concentrations of heavy metals in soil or crop and hair samples were used to assess their potential ecological risks,or to find the responses to these metals as evidences to prove the potential risk was coming down to observed harm,respectively.The results showed that,these metals in soil were ranked by severity of ecological risk as Hg>Cd>Pb>Cu>Cr>As>Zn,based on their single-element indexes.In the view of the potential ecological risk indexes,of all soil samples,about half had significantly high or high potential ecological risk,which covered more than 74%of the studied region.Most of the risks were 97.41%from Hg,Pb and Cd,especially,84.37%from Hg.Both the single-element and potential ecological risk indexes indicated that,the ecological risk grades had a special spatial characteristic,and increased from northwest to southeast generally.This was agreed with the spatial distribution of the strength in gold mining activities over the studied region.The concentrations of Hg and Pb were higher than their relative backgrounds in the corps,and were even 9.48 and 25.09 times higher than their relative backgrounds in residents'hair,respectively.All these showed that the heavy metals in the soil had a high potential ecological risk,especially,had been affecting these crops'growing and yield,and even the residents'health through food strains.Obviously,these metals'potential ecological harm had been coming down to observed harm to the ecology.

Analysis of Heavy Metal Sources for Vegetable Soils from Shandong Province, China

Heavy metal pollution in agricultural soils has serious negative influence on human health. Concentrations of Cd, Hg, As, Pb, Cr, Cu, Zn, and Ni in top soils （0-20 cm） of greenhouses and farmlands from four main vegetable production areas Shouguang, Laiyang, Jinxiang, and Zhangqiu in Shandong Province, one of the most rapidly developing regions in China, were measured in this study. Shouguang is mainly occupied by greenhouse vegetables and the other three areas are mainly open field culture. Total of 149 soil samples were collected. The average concentrations of the eight heavy metals of the tested 149 soil samples were all below the threshold values according to ＂Farmland environmental quality evaluation standards for edible agricultural products （HJ332-2006）＂ of China. However, most of the studied heavy metals were present at higher concentrations than those of the natural background levels in local agricultural soils. Among the total 149 soil samples, 22 samples were contaminated by Cd, Ni, Cu, or Hg. Comparisons showed that the main pollution element in greenhouse vegetable soils was Cd, while that of open field vegetable soils was Cu. The results of principal components analysis （PCA） suggested that concentrations of Cr, As, and Ni were mainly controlled by parent rocks; Hg and Pb were affected by anthropogenic activities such as vehicle and industrial fumes and waste water irrigation. Meanwhile, concentrations of Cd, Cu, and Zn were affected mainly by the use of agrochemicals. Most of the heavy metals were positively correlated with each other in concentration. Appropriate measures should be taken to effectively control heavy metal levels in vegetable soils and thus protect human health.

Risk assessment of heavy metal contaminated soil in the vicinity of a lead/zinc mine

Heavy metal contamination of soils through anthropogenic activities is a widespread and serious problem confronting scientists and regulators throughout the world. In this study we investigated the distribution, chemical species and availability of lead, zinc, cadmium and copper in nine surface（0 to 20 cm） soils from near an abandoned lead/zinc mine tailings located in Shaoxing, Zhejiang, China. Total heavy metal contents ranged from 5271 to 16369 mg/kg for Pb, 387 to 1221 mg/kg for Zn, 3.0 to 9.3 mg/kg for Cd and 65 to 206 mg/kg for Cu. In general, all heavy metals exceeded China National Standards for Soil Environmental Quality of Heavy Metals by a factor of 3-65 times. Comparison of the heavy metal concentrations（Pb, Zn, Cd and Cu） with clay content revealed a strongly significant relationship while significant relationship（ P 〈 0.001 ） was also obtained between Cd ＋ Zn and Pb ＋ Cu. Solid phase speciation of the soils using Tessier procedure showed that the heavy metals were distributed in the order： residual 〉〉 organically complexed-Fe-Mn oxides occluded 〉 carbonate bound 〉 exchangeable 〉 water soluble. In the organic matter fraction, the ratio of Pb（29.1% ） to its total concentration in the soils was higher than those of Zn（4.70% ）, Cd（3.16% ） and Cu（9.50% ）. The percentages of the water soluble and the exchangeable fractions of Pb（1.80% ） and Cd（2.74% ） were markedly greater than those of Zn（0.10% ） and Cu（0.15% ）, suggesting that Pb and Cd are relatively more mobile and hence more toxic in the contaminated soils. Strongly significant relationships between H20-Pb, H20-Zn and H20-Cu, strong positive correlations between H20-Pb, H20-Zn, H20-Cu and organic matter in soil were found. The content of H20-Pb, H20-Zn, H20-Cu was negatively correlated with pH values. The similar negative relationships between pH values and exchangeable heavy metals were also recorded. It is suggested that increasing soil pH or liming the soil could decrease bioavailability of heavy metals in the soil.

Heavy Metal Distribution in Soils near the Almalyk Mining and Smelting Industrial Area,Uzbekistan

The present study demonstrates distribution and chemical forms of heavy metals in soils of the AImalyk mining and smelting industrial area along five transects. The study area is located in Almalyk, Uzbekistan, where the intensification of industrial enterprises negatively impacts the environment. The distribution of 17 heavy metals （Cu, Zn, Pb, Sc, V, Cr, Co, Ni, Ga, Rb, Sr, Y, Zr, Nb, Ba, Th, and U） were studied in 21 sampling locations （21×3=63 soil samples） along five radial transects with a total length of 60 km downwind deposition gradient. Soil samples were collected from the upper layer （0-10 cm） at 4-6 km intervals. As a result of X-ray fluorescence spectrometry analyses by using X -ray fluorescence spectroscopy （XRF, Philips Analytical Ink, USA ）, a significant decrease in heavy metal （Cu, Zn, Pb） deposition was found going from the source in a downwind direction. Soil samples taken from the first location （near the pollution sources） showed higher concentrations of Cu, Zn and Pb, and lower concentrations with increasing distance from the source. Obtained data showed different impact of pollution sources to heavy metal deposition and distribution in soils. The Almalyk mining and smelting complex is the major source of Pb, Zn and Cu enrichment in soils. Distribution of other trace elements does not exceed background content and suggests lithogenic background. This allowed us to divide these elements into two groups： （1） technogenic （Cu, Zn and Pb）; and （2） lithogenic （Sc, V, Cr, Co, Ni, Ga, Rb, Sr, Y, Zr, Nb, Ba, Th and U） origins.

Study of polluted soil remediation based on freezing and thawing cycles

It is generally known that soil pollution poses a terrible hazard to the environment, but the present techniques of contaminated soil remediation cannot control this growing threat. This paper compares the pollutant extraction efficiency of traditional pumping and treating, which is a typical washing technology for the remediation of contaminated soils, with methods that utilize freeze-thaw cycles. In the soil freezing process, water shifts from unfrozen soils to the freezing front, and the permeability of soil will be enhanced under certain temperature gradients and water conditions. Therefore, this paper discusses the purification of contaminated soil through freeze-thaw action. We conducted a cleansing experiment on clay and silica sand infused with NaCl（simulation of heavy metals） and found that the efficiency of purification was enhanced remarkably in the latter by the freeze-thaw action. To assess the effective extraction of DNAPLs in soil, we conducted an experiment on suction by freezing, predicated on the different freezing points of moisture and pollutants. We found that the permeability coefficient was significantly increased by the freezing-thawing action, enabling the DNAPL contaminants to be extracted selectively and effectively.

Illustrating the multi-stakeholder perceptions of environmental pollution based on big data:Lessons from China

The relationship between stakeholders and the environment influences sustainable development and human wellbeing.To illustrate the multi-stakeholder perceptions of environmental pollution in China,we interpreted a feedback loop in the perception-behavior-environment nexus from the perspective of the coupled human-environment system,measured the differences of environmental perceptions among five stakeholders(the public,government,media,companies,and scientists)and regions(including 31 provinces,autonomous regions,and municipalities in China,with exceptions of Taiwan of China,Hong Kong of China,and Macao of China due to a lack of data)using big data,and made a comparison between the perceptions and the actual pollution situation.The results showed that the five stakeholders exhibited similar perceptions of environmental pollution at the national scale,with air pollution being of most concern,followed by water pollution and soil pollution.There were significant spatial differences in environmental perceptions.All stakeholders in the developed regions in eastern China paid relatively high attention to environmental issues,while those in the northwestern regions paid much less attention.There existed a mutual influence and interaction among the different stakeholders.More attention should be paid to air pollution in Xinjiang Uygur Autonomous Region and Ningxia Hui Autonomous Region,water pollution in Hainan Province,Inner Mongolia Autonomous Region,Heilongjiang Province,and Jilin Province,and soil pollution in Hainan Province,Fujian Province,and Jilin Province.This paper provides a research paradigm on multi-stakeholder environmental perceptions based on big data,and the results provide a background reference for regional environmental governance.

Experimental Study on Enhanced Electrokinetic Remediation of Heavy Metal-contaminated Soil

In order to improve the efficiency of traditional electrokinetic remediation method of heavy metal-contaminated soil, cadmium-contaminated soil was remediated by two enhanced electrokinetic techniques, namely, the approaching anode method and intermittent current method. The remediation effect was verified under the conditions that the electric field strength was 2 V/cm, 0.1 mol/L citric acid was used as the electrolyte, and the remediation reaction time was 96 h. The results showed that for the approaching anode method, when the average electromigration distance was 5.48, the removal rate was 88.12%, which was 10.47% higher than the unenhanced technique, and the energy consumption per unit volume was 7.36 kWh/m^3;and as to the intermittent current method, the removal rate was 80.81%, and the energy consumption per unit volume was 8.12 kWh/m^3, which was relatively reduced by 33.07%. After the remediation, the proportions of the weak acid extractive form and reducible form of calcium decreased, and the proportions of the oxidizable form and residual form of cadmium did not change significantly.