污染土壤的淋洗法修复研究进展

污染土壤淋洗技术是修复污染土壤的一种新方法 ,是对污染土壤生物修复的一种补充 ,使污染土壤修复的系统化成为可能。淋洗法主要使用淋洗剂清洗土壤 ,使土壤中污染物随淋洗剂流出 ,然后对淋洗剂及土壤进行后续处理 ,从而达到修复污染土壤的目的。因为淋洗剂的种类和淋洗方式的不同 ,土壤淋洗法可分为许多种类。土壤淋洗法主要受土壤条件、污染物类型、淋洗剂的种类和运行方式等因素影响。综合考虑多方面因素 ,就有潜力设计出经济高效的土壤淋洗系统。土壤淋洗法有很多优点 ,尽管也存在一些问题 ,但其技术上的优势也是其他方法难以取代的 ,所以有良好的应用前景。     

Sorption of non-ionic surfactants to soil: the role of soil mineral composition

In this study, the importance of individual soil mineral constituents on non-ionic surfactant sorption is evaluated by employing scanning electron microscopy (SEM) equipped with energy-dispersive X-ray analysis (EDAX) to observe microchemical surface composition of model soil colloids and relate surface microchemical composition to the sorption behavior of a non-ionic surfactant, Polyethylene Glyco Mono-p-nonylphenyl Ether (A9PE10), on selected model soil colloids. This information is critical to understanding the fate and transport of this class of contaminants in subsurface. Results obtained from this study indicate that a correlation between the atomic ratio of Si:(Al + Fe) on soil mineral surface and A9PE10 sorption capacity exist, where those soil with larger value of Si:(Al + Fe) ratio exhibit higher sorption capacity. This allows us to predict that the non-ionic surfactant sorption capacity for soil decrease with progressively increasing states of soil maturity.     

Evaluation of soil flushing potential for clean-up of desert soil contaminated by industrial wastewater

The flushing potential of a desert loess soil contaminated by the flame retardant Tetrabromobisphenol A (TBBPA), chloride (Cl(-)) and bromide (Br(-)) was studied in undisturbed laboratory column experiments (20 cm diameter, 45 cm long) and a small field plot (2 x 2 m). While the soluble inorganic ions (Cl(-) and Br(-)) were efficiently flushed from the soil profile after less than three pore volumes (PV) of water, about 50% of the initial amount of TBBPA in the soil was also flushed, despite its hydrophobic nature. TBBPA leaching was made possible due to a significant increase in the pH of the soil solution from 7.5 to 9, which increased TBBPA aqueous solubility. The remaining TBBPA mass in the soil was not mobilized from its initial location in the topsoil due to the decrease in pH at this horizon. In situ soil flushing demonstrated that this method is a feasible treatment for reducing soil contamination at this site.     

Effect of soil properties on degradation and sorption of methyl bromide in soil

Methyl bromide (CH₃Br) is currently the most widely used soil fumigant, and its emission into the atmosphere after application reportedly contributes to ozone depletion in the stratosphere. Irreversible degradation and partially reversible sorption reactions affect the quantity of this furnigant reaching the soil surface and escaping into the atmosphere. Incubation studies in closed headspace vials under controlled conditions showed that degradation of CH₃Br was highly dependent on soil organic matter content, and to a lesser extent, on the moisture level in the soil. Methylation of CH₃Br on organic matter was suggested to be the major reaction that CH₃Br undergoes in the soil environment. Other soil constituents such as clay did not contribute to the degradation under moist or air-dried conditions, though enhanced degradation was observed on oven-dried montmorillonite and kaolinite clays. Within soil profiles, degradation of CH₃Br decreased with soil depth mainly due to the reduction of soil organic matter content with depth. In both Greenfield and Wasco sandy loams, the degradation rate of CH₃Br in soil layers from 0 to 270 cm could be estimated from soil organic matter content. Sorption of CH₃Br on moist soils was generally limited, and varied with soil depth. The degree of sorption could be predicted from soil moisture alone or soil moisture and organic matter content.     

Stability of pentobarbital in soil

Intravenous injection of barbiturates, particularly pentobarbital (5-ethyl-5-pentan-2-yl-1,3-diazinane-2,4,5-trione), is a widely used method to euthanize large animals such as horses. However, one concern with this method is the fate of pentobarbital after the disposal of the carcass. As tissues decompose, pentobarbital may leach into the soil and from there migrate to groundwater. A method using methanol extraction, solid phase concentration, and liquid chromatography (LC/MS) has been developed to measure pentobarbital in soils. Recovery of pentobarbital from soil averaged approximately 85% from different soil types including topsoil, potting soil, sand, stall sweepings, and loam. The method was capable of detecting pentobarbital levels of 0.1 ppm. A calibration curve was constructed with a linear range of 1 ppm to 100 ppm. The limit of quantification was 0.5 ppm. The rate of degradation of pentobarbital in sand, topsoil, and potting soil was measured over a 17-week period. At the end of week 17, approximately 17% of the pentobarbital remained in the sand, 19% remained in the topsoil, and 10% remained in the potting soil. While there was a significant decrease in the pentobarbital recovered from the soil, there were still detectable amounts of pentobarbital present in the soil after 17 weeks. To determine the importance of bacterial degradation, the three soil types were autoclaved before addition of pentobarbital. After autoclaving, no degradation of pentobarbital was observed in sand and one topsoil sample, while there was no difference in the degradation of pentobarbital in autoclaved potting soil versus potting soil that had not undergone autoclaving.     

Decontamination of electronic waste-polluted soil by ultrasound-assisted soil washing

Laboratorial scale experiments were performed to evaluate the efficacy of a washing process using the combination of methyl-β-cyclodextrin (MCD) and tea saponin (TS) for simultaneous desorption of hydrophobic organic contaminants (HOCs) and heavy metals from an electronic waste (e-waste) site. Ultrasonically aided mixing of the field contaminated soil with a combination of MCD and TS solutions simultaneously mobilizes most of polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and the analyte metal (Pb, Cu, and Ni) burdens. It is found that 15 g/L MCD and 10 g/L TS is an efficient reagent combination reconciling extraction performance and reagent costs. Under these conditions, the removal efficiencies of HOCs and heavy metals are 93.5 and 91.2 %, respectively, after 2 cycles of 60-min ultrasound-assisted washing cycles. By contrast, 86.3 % of HOCs and 88.4 % of metals are removed from the soil in the absence of ultrasound after 3 cycles of 120-min washing. The ultrasound-assisted soil washing could generate high removal efficiency and decrease the operating time significantly. Finally, the feasibility of regenerating and reusing the spent washing solution in extracting pollutants from the soil is also demonstrated. By application of this integrated technology, it is possible to recycle the washing solution for a purpose to reduce the consumption of surfactant solutions. Collectively, it has provided an effective and economic treatment of e-waste-polluted soil.

     

Physicochemical soil parameters affecting sequestration and mycobacterial biodegradation of polycyclic aromatic hydrocarbons in soil

Six soils, obtained from grasslands and wooded areas in Northeastern Illinois, were physicochemically characterized. Measured parameters included total organic carbon (TOC) content, contents of humic acid, fulvic acid and humin, pore volume and pore size distribution, and chemical makeup of soil organic matter (determined using solid-state ¹³C-NMR). Moistened, gamma-sterilized soils were spiked with 200 ppm of either phenanthrene or pyrene (including ¹⁴C label); following 0, 40, or 120 days of aging, the contaminant-spiked soils were then inoculated with Mycobacterium austroafricanum strain GTI-23, and evolution of ¹⁴CO₂ was assessed over a 28-day period. Results for both phenanthrene and pyrene indicated that increased contact time led to increased sequestration and reduced biodegradation, and that TOC content was the most important parameter governing these processes. One soil, although only tested with phenanthrene, showed significantly lower-than-expected sequestration (higher-than-expected mineralization) after 40 days of aging, despite a very high TOC value (>24%). Because the level of sequestration in this soil was proportional to the others after 120 days of aging, this implies some difference in the temporal progression of sequestration in this soil, although not in its final result. The primary distinguishing feature of this soil was its considerably elevated fulvic acid content. Further experiments showed that addition of exogenous fulvic acid to a soil with very low endogenous humic acids/fulvic acids content greatly enhanced pyrene mineralization by M. austroafricanum. Extractabilities of 13 three- to six-ring coal tar PAHs in n-butanol from the six soils after 120 days of sequestration were strongly TOC-dependent; however, there was no discernible correlation between n-butanol extractability and mycobacterial PAH mineralization.     

Relative effect of soil moisture on emissions and distribution of 1,3-dichloro-propene and chloropicrin in soil columns

Emissions of soil fumigants are regulated to protect air quality in California. Irrigation prior to fumigation can reduce fumigant emissions at relatively low costs; however, the optimum range of soil water content that reduces emissions without reducing efficacy is not clearly defined. The objective of this study was to determine the effects of soil water content [at 30, 45, 60, 75, 90 and 100% field capacity (FC)] on the emission and distribution of fumigants 1,3-dichloropropene (1,3-D) and chloropicrin (CP) in columns packed with a sandy loam soil. After injecting equal amounts of cis-1,3-D, trans-1,3-D, and CP, fumigant emissions and distribution in soil were monitored for 14 days. Emissions of all three compounds showed similar response to soil water content except that CP emissions were lower than both isomers of 1,3-D. The emission peak flux was highest and occurred earliest in the driest soil while it was reduced and delayed as soil water content increased. After the peak, emission flux decreased rapidly in the driest soil but more slowly in higher water content treatments. Initially, higher soil water content resulted in substantially lower cumulative emissions among the treatments, but as time progressed, the differences in cumulative emissions decreased or even disappeared. These trends were likely due to the effect of the closed-bottom short soil columns which allowed fumigants to only move upward and contribute to emission. Higher fumigant concentrations in the soil–gas phase were observed in high soil water content treatments, due to less emission loss and more fumigant retained in the soil.     

Long-term effects of soil heterogeneity on cadmium behaviour in soil

A deterministic model for long-term behaviour of contaminants in the rootzone is developed that includes sorption, leaching, and plant uptake. The model is applied to cadmium accumulation in a sandy soil and uptake of cadmium by barley. Sensitivity analysis showed that the sensitivity of the leaching rate to changes in soil chemical and soil physical parameters decreases as a function of time, and becomes zero when steady state is reached. In contrast, accumulation of cadmium in soil and the plant uptake rate of barley are increasingly sensitive to soil chemical and soil physical parameters as time preceeds. To analyse cadmium behaviour in a field that is heterogeneous with respect to soil physical properties, the interstitial flow velocity was assumed to be a random, lognormally distributed variate. Using Monte Carlo simulation, the average plant uptake rate appeared to be much higher in the stochastic analysis than in the deterministic approach. Steady state is reached after a very long period of time. For a lognormally distributed proton activity, causing heterogeneity with respect to the sorption capacity of the soil, the model predicted similar deviations from the deterministic approach. It is concluded that reference values for groundwater and crop quality are exceeded earlier in a heterogeneous field than in a homogenous soil profile. Moreover, when average values suggest an acceptable situation, variability of the leaching rate and the plant uptake rate can still cause exceedance of reference values in part of the field. Therefore, it is reasoned that environmental quality standards should take soil heterogeneity into account.     

Ecotoxicological assessment of doxycycline in soil

Doxycycline has been used in continually increasing quantities for mass treatment of food animals because of its greater bioavailability relative to older tetracyclines. The study presented in this paper was undertaken to investigate the degradation rate of the tetracycline derivative in manure-amended soil. In the present experiment, following composting, the doxycycline-contaminated manure was applied to agricultural land, and a field study was performed to investigate the degradation rate of doxycycline in soil. By the end of the 20-week sampling period, about 20 %, 33 % and 18 % of the initial doxycycline concentrations could be measured in soil samples taken at three different soil depths. The calculated half-life of doxycycline in the soil was 66.5, 76.3 and 59.4 days at depths of 0 cm, 25 cm and 50 cm, respectively. The potential effect of doxycycline on soil microbial activity was demonstrated by the nitrogen transformation test performed in compliance with the Organisation for Economic Co-operation and Development (OECD) Guideline No. 216. On day 28, the following nitrate concentrations of the control soil sample were found in the soil samples treated with different amounts of doxycycline: 76.9 %, 53.0 %, 65.6 %, 59.7 % and 77.1 %.     

A framework of connections between soil and people can help improve sustainability of the food system and soil functions

Globally soil quality and food security continue to decrease indicating that agriculture and the food system need to adapt. Improving connection to the soil by knowledge exchange can help achieve this. We propose a framework of three types of connections that allow the targeting of appropriate messages to different groups of people. Direct connection by, for example, handling soil develops soil awareness for management that can be fostered by farmers joining groups on soil-focused farming such as organic farming or no-till. Indirect connections between soil, food and ecosystem services can inform food choices and environmental awareness in the public and can be promoted by, for example, gardening, education and art. Temporal connection revealed from past usage of soil helps to bring awareness to policy workers of the need for the long-term preservation of soil quality for environmental conservation. The understanding of indirect and temporal connections can be helped by comparing them with the operations of the networks of soil organisms and porosity that sustain soil fertility and soil functions.     

Ecotoxicological assessment of doxycycline in soil

Doxycycline has been used in continually increasing quantities for mass treatment of food animals because of its greater bioavailability relative to older tetracyclines. The study presented in this paper was undertaken to investigate the degradation rate of the tetracycline derivative in manure-amended soil. In the present experiment, following composting, the doxycycline-contaminated manure was applied to agricultural land, and a field study was performed to investigate the degradation rate of doxycycline in soil. By the end of the 20-week sampling period, about 20 %, 33 % and 18 % of the initial doxycycline concentrations could be measured in soil samples taken at three different soil depths. The calculated half-life of doxycycline in the soil was 66.5, 76.3 and 59.4 days at depths of 0 cm, 25 cm and 50 cm, respectively. The potential effect of doxycycline on soil microbial activity was demonstrated by the nitrogen transformation test performed in compliance with the Organisation for Economic Co-operation and Development (OECD) Guideline No. 216. On day 28, the following nitrate concentrations of the control soil sample were found in the soil samples treated with different amounts of doxycycline: 76.9 %, 53.0 %, 65.6 %, 59.7 % and 77.1 %.     

Leaching and degradation of ethametsulfuron-methyl in soil

Leaching and degradation of the herbicide ethametsulfuron-methyl[methyl 2-[(4-ethoxy-6-methylamino-1,3,5-triazine-2-yl)carbamoylsulfamoyl]benzoate] in three soils were investigated under laboratory conditions. Ethametsulfuron-methyl was mobile on soils when tested using non-aged and aged soil columns; this mobility agreed reasonably well with Freundlich soil isotherm constants. It was found that ethametsulfuron-methyl was more mobile in alkaline sandy Vertisol soil and neutral loamy Alfisol soil than in acidic clayey Red soil. Degradation of ethametsulfuron-methyl in soils was pH-dependent; calculated half-life (t(1/2)) values ranged from 13 to 67 days. Ethametsulfuron-methyl was more persistent in neutral or weakly basic than in acidic soil. Five soil metabolites were isolated and identified by LC/MS/MS analysis. The degradation pathways included the cleavage of the sulfonylurea bridge, N- and O-dealkylation, and triazine ring opening.     

Influence of soil moisture on the sequestration of organic compounds in soil

A study was conducted as a part of continuing investigation of the effect of soil moisture on the sequestration of organic compounds aged in the soil. Here, experiments focused on the effects of moisture changes within the soil before, during, and after contaminant addition. The extractability of aged (68 d) phenanthrene was greater from soil that had been subjected to wetting and drying cycles prior to solute addition as compared to soil initially maintained at constant moisture. The recovery of phenanthrene added to moist soil was increased relative to extractability from soil that was air-dried at the time of the contaminant addition. Repeated wetting and drying of soil after the addition of atrazine or phenanthrene resulted in decreased extractability of the compounds as compared to samples maintained at constant moisture. A method for rapidly sequestering contaminants is proposed and may be useful in limiting the time required for laboratory studies involving “aged” contaminants. These data build upon the findings of earlier work from our laboratory and indicate that changes in the moisture conditions of soil can affect the availability of sequestered contaminants possibly through alterations in the structure of the natural solid.     

Evaluation of antibiotic mobility in soil associated with swine-slurry soil amendment under cropping conditions

Interest in identifying pools of antibacterial-resistance genes has grown over the last decade, with veterinary antibiotics (VAs) receiving particular attention. In this paper, a mesoscale study aimed at evaluating the vertical transport of common VAs—namely, fluoroquinolones, tetracyclines, sulfonamides, and lincosamides in agricultural soil subjected to drip irrigation—was performed under greenhouse conditions. Accordingly, leachates of cropped and uncropped soil, amended with swine-slurry leading to 19–38 μg kg^?1 (dry mass) antibiotics in the soil, were analyzed over the course of the productive cycle of a lettuce (42 days) with three sampling campaigns (N?=?24). High lincomycin (LCM) concentrations (30–39 μg L^?1) were detected in the leachates collected from the swine-slurry-amended soil. The highest LCM mass recovered in the leachates (30.1?±?1.63 %) was obtained from cropped experimental units. In addition, the LCM leaching constant and its leaching potential as obtained from the first-order model were higher in the leachates from the cropped experimental units. Lower concentrations of sulfadimethoxine were also detected in leachates and in soil. Enrofloxacin and oxytetracycline occurred only in soil, which is consistent with high soil interaction.     

建筑弃土与污泥堆肥混合配制营养土对园林植物的影响

使用建筑弃土与污泥堆肥配制营养土并应用于园林绿化。以凤仙花为研究对象,通过盆栽实验观察和对比分析了凤仙花从播种到开花整个生命过程的生长指标,并对其结果进行模糊评价。结果表明,凤仙花播种期和生长期各生长指标随着营养土中堆肥含量的增加而增加,并在堆肥施用量30%时达到最佳;营养土中的重金属对凤仙花的生长速度有抑制效应,主要集中在播种期和生长期初期,随着凤仙花的生长成熟,重金属的胁迫效应持续减少,并在成熟期显著降低,重金属对凤仙花地表部分的抑制更为明显;建筑弃土与污泥堆肥配制的营养土对园林植物营养效果良好,成熟期的凤仙花生物量大幅度增加,最大增幅550%;通过模糊评价并综合考虑配置方案,最佳堆肥施用量为30%。     

Chloride concentration affects soil microbial community

We studied the effect of increased inorganic chloride concentration on forest soil microflora in a laboratory experiment. Microbial DNA extracted from experimental soil samples was amplified with PCR using primer pairs specifically amplifying bacterial, eukaryotic and fungal DNA fragments. The resulting amplified DNA was further used for terminal restriction fragment length polymorphism (TRFLP) analysis. Our work revealed that chloride concentration affects the indigenous microbial community in experimental soil. This was documented on an unidentified microorganism whose DNA was detectable in soil high in chloride but was not found in soil with low chloride concentration. The presence of the organism responsive to increased chloride concentration was associated with the highest observed value of chlorination of humic acid, suggesting possible role of this organism in soil chlorine turnover. High chloride concentration in the soil tended to decrease the rate of degradation of trichloroacetic acid. The problems connected with measurement of chlorination rates in soil are discussed.     

Combined effect of diuron and simazine on photosystem II photochemistry in a sandy soil and soil amended with solid olive-mill waste

Diuron (3-(3,4-dichlorophenyl)- = 1,1-dimethylurea) and simazine (6-chloro-N(2), N(4)-diethyl-1,3,5-triazine-2,4-diamine) are soil-applied herbicides used in olive crops. The objective of this study is to investigate the effect of these herbicides on Photosystem II photochemistry of Olea europaea L., and whether the amendment of soil with an organic waste (OW) from olive oil production industry modifies this effect. For this purpose, herbicide soil adsorption studies, with unamended and OW-amended soil, and chlorophyll fluorescence measurements in adult olive leaves, after one, two and three weeks of soil herbicide treatment and/or OW amendment, were performed. Soil application of these herbicides reduced the efficiency of Photosystem II photochemistry of olive trees due to chronic photoinhibition, and this effect is counterbalanced by the addition of OW to the soil. OW reduces herbicide uptake by the plant due to an increase in herbicide adsorption.     

Seasonal variation of HCH isomers in open soil and plant-rhizospheric soil system of a contaminated environment

Background, aim, and scope  

Lindane, technically 1, 2, 3, 4, 5, 6-hexachlorocyclohexane (γ- HCH), is the most commonly detected organochlorine pesticide from diverse environmental compartments. Currently, India is the largest consumer and producer of lindane in the world. The production of lindane results in the generation of large quantities of waste HCH isomers (mainly α-, β- and δ-). All these isomers are toxic and have a long-range environmental transport potential. The aim of this study was to monitor the seasonal variation of HCH isomers in an open soil–plant–rhizospheric soil system of a contaminated industrial area. For this, selected plant species and their rhizospheric soil (soil samples collected at a depth range of 0–45 cm near to the root system) and open soil samples (soil samples collected (0–30 cm depth) from 1–1.5 m away from the plant root system) were collected for 2 years (two summer seasons and two winter seasons).     

Layer of organic pine forest soil on top of chlorophenol-contaminated mineral soil enhances contaminant degradation

Chlorophenols, like many other synthetic compounds, are persistent problem in industrial areas. These compounds are easily degraded in certain natural environments where the top soil is organic. Some studies suggest that mineral soil contaminated with organic compounds is rapidly remediated if it is mixed with organic soil. We hypothesized that organic soil with a high degradation capacity even on top of the contaminated mineral soil enhances degradation of recalcitrant chlorophenols in the mineral soil below. We first compared chlorophenol degradation in different soils by spiking pristine and pentachlorophenol-contaminated soils with 2,4,6-trichlorophenol in 10-L buckets. In other experiments, we covered contaminated mineral soil with organic pine forest soil. We also monitored in situ degradation on an old sawmill site where mineral soil was either left intact or covered with organic pine forest soil. 2,4,6-Trichlorophenol was rapidly degraded in organic pine forest soil, but the degradation was slower in other soils. If a thin layer of the pine forest humus was added on top of mineral sawmill soil, the original chlorophenol concentrations (high, ca. 70 μg g^?1, or moderate, ca. 20 μg g^?1) in sawmill soil decreased by >40 % in 24 days. No degradation was noticed if the mineral soil was kept bare or if the covering humus soil layer was sterilized beforehand. Our results suggest that covering mineral soil with an organic soil layer is an efficient way to remediate recalcitrant chlorophenol contamination in mineral soils. The results of the field experiment are promising.