Evaluation of residual soil contamination from commercial oil well drilling activities and its impact on the naturally occurring background radiation environment

Radiation exposure received by individuals living and working on a farmland contaminated with radium was evaluated by measuring the technologically enhanced radiation background using portable survey instruments and a high‐pressure ionization chamber. Analysis of selected organic compounds, metals, and radioactive material in samples of soil and water obtained from the farm demonstrate a potential risk to inhabitants that needs to be evaluated, especially for future generations living and working on this land who may not be aware of the potential hazard. The distribution of radium and several other hazardous waste materials was found to be significantly elevated in areas where sludge ponds and waste pits were formerly located. Transport of these contaminants in soil was detected by in situ measurement of radium, which may be a useful analog for determining the translocation of metals and other contaminants associated with oil well‐drilling activities. Conventional risk assessment models, using default input parameters, assume that exposure to radium in the soil is via the food chain and radon, and that inhalation of resuspended particles is less important. These models also assume that the chemical and physical characteristics of the radium contamination remain constant in time. However, under certain environmental conditions, the radium compounds will become more soluble with time, increasing their significance as a source of radiation exposure, especially as the radium will persist in soil for many thousands of years. Assessment of present and future risk to populations living and working on these contaminated lands must account for the potential change in radium solubility with time and the increased risk from both inhalation and ingestion of radium

This research describes environmental conditions found at one former well site in the Martha oil field in eastern Kentucky and identifies several important concerns related to the current and future risk associated with use of land contaminated with naturally occurring radioactive material.     

铜陵狮子山铜尾矿场植被调查与土壤酶活性研究

对安徽铜陵狮子山铜尾矿废弃地进行植被调查,发现当地现今自然定居植物共42种,隶属于13科36属,主要包括禾本科10种,豆科6种,菊科6种,十字花科5种。全部植物中,1～2年生草本植物21种,多年生草本植物20种,形成6种相对稳定的演替群落和单种斑块。尾矿场土壤的5种土壤酶（蔗糖酶、过氧化氢酶、脲酶、磷酸酶、多。酚氧化酶）活性的高低与植被丰富度和群落分布有一定的对应关系。结合本实验室前期工作,证实某些植物如白茅、狗牙根、白车轴草等已在尾矿场上成功定居且综合优势比较高,可作为铜尾矿治理中优先选用的物种。     

Speciation and Vertical Distribution of Lead and Lead Shot in Soil at a Recreational Firing Range

In this study, the speciation, vertical distribution and soil particle size fractions of lead in soil samples at a recreational firing range was determined. This study was performed to gain a better understanding of how lead shot breaks down at ranges. Both the chemical form of lead and the types of soil particles with which lead is associated are important for understanding not only the mobility and persistence, but also the human and ecological impact of lead at these ranges. Lead as shot gun pellets was found to be the dominant form of lead in soil samples. The highest levels were measured in surface samples located in the “fall zone” of the range. Results indicate shot to be relatively absent below surficial samples. Lead concentrations in soil decreased markedly across a 0–6″ depth profile. Lead carbonates were the dominant non-shot form of lead present at all depths. Water-soluble lead species made up a minor fraction of the non-shot lead present in the samples. Based on soil particle sizes measured, highest concentrations of lead were measured in soil particles passing a 0.075 mm sieve.     

自然演替过程中铜尾矿土壤酶活性的变化

铜陵矿区堆放了大量不同时期的铜尾矿,形成大量铜尾矿废弃地,其中的大部分铜尾矿废弃地处于自然生态恢复状态。并形成典型的原生演替系列。为探讨废弃地自然生态恢复中不同演替阶段植物群落变化与土壤酶活性变化的关系,对铜陵3处不同时期弃置的尾矿废弃地进行了调查。随着自然生态系统演替的进行,尾矿中土壤酶活性逐步提高,维管植物群落下尾矿中土壤酶活性〉隐花植物结皮下尾矿中土壤酶活性〉裸地处土壤酶活性;位于植物群落下的尾矿废弃地中脲酶、碱性磷酸酶、过氧化氢酶的活性从表层至下层逐渐降低。不同植物群落对尾矿中土壤酶活性影响有很大差异,位于木贼群落下的尾矿中几种土壤酶的活性高于位于白茅群落和中华结缕草群落下的尾矿中酶的活性。相关分析表明,土壤酶活性与有机质、总N表现出显著的正相关。     

Investigation of the extent of contamination of heavy metals in agricultural soil using statistical analyses and contamination indices

To examine the level of contamination of Eshghabad region, Neyshabur, the concentration of heavy metals in soil was measured. For this purpose, 37 samples were taken from surface soil and the total concentration of heavy elements was measured by inductively coupled plasma (ICP). The mean concentration of Pb, Ni, Cu, Zn, and Fe was obtained to be 195, 87.3, 22.8, 274.8, and 2.5%, respectively. Using five valid indicators, the intensity of metal contamination in soil was calculated and compared. Furthermore, using statistical analyses, the relationships between the elements, their origins, and the spatial distribution of metals across various stations were investigated. The results indicated that the mean value of all of the studied metals (except for iron and copper) is greater than the mean concentration of metals in the Earth's crust. The indicators showed very high contamination for lead, while low to medium contamination for other elements of interest in the farming soils of the region. Statistical analyses indicated that there is a relatively similar contamination intensity across all of the studied stations. Considering the quality standards, the soils of this region are threatened by contamination of lead.     

贵州省某土法炼锌点土壤重金属污染现状

对贵州省赫章县新官寨土法炼锌点的土壤重金属含量及空间分布进行了研究,以了解土法炼锌活动停止以后土壤重金属的污染状况.结果表明,当地农业土壤重金属的平均含量分别为Pb 337、Zn 648、Cd 9.0、Hg 0.44、Cu 121和As 17 mg·kg-1,分别是贵州省农业土壤背景值的7.5、7.9、26.4、2.2、4.7和0.8倍.单项污染指数显示,土壤Cd的污染最重,依次为Zn、Pb、As、Hg和Cu.综合污染指数揭示,该土法炼锌点4 km范围内的表层农业土壤严重污染.土壤中的污染物主要累积于表层30 am内,30 cm以下浓度较低.土壤Zn和Cd具有较高的活性和迁移性,峰值已向下迁移15～20 cm.     

Phytoremediation of soil contaminated with cadmium, copper and polychlorinated biphenyls

A pot experiment and afield trial were conducted to study the remediation of an aged field soil contaminated with cadmium, copper and polychlorinated biphenyls (PCBs) (7.67 +/- 0.51 mg kg(-1) Cd, 369 +/- 1 mg kg(-1) Cu in pot experiment; 8.46 +/- 0.31 mg kg(-1) Cd, 468 +/- 7 mg kg(-1) Cu, 323 +/- 12 microg kg(-1) PCBs for field experiment) under different cropping patterns. In the pot experiment Sedum plumbizincicola showed pronounced Cd phytoextraction. After two periods (14 months) of cropping the Cd removal rates in these two treatments were 52.2 +/- 12.0 and 56.1 +/- 9.1%, respectively. Total soil PCBs in unplanted control pots decreased from 323 +/- 11 to 49.3 +/- 6.6 microg kg(-1), but with no significant difference between treatments. The field microcosm experiment intercropping of three plant species reduced the yield of S. plumbizincicola, with a consequent decrease in soil Cd removal. S. plumbizincicola intercropped with E. splendens had the highest shoot Cd uptake (18.5 +/- 1.8 mg pot(-1)) after 6 months planting followed by intercropping with M. sativa (15.9 +/- 1.9 mg pot(-1)). Liming with S. plumbizincicola intercropped with M. sativa significantly promoted soil PCB degradation by 25.2%. Thus, adjustment of soil pH to 5.56 combined with intercropping with S. plumbizincicola and M. sativagave high removal rates of Cd, Cu, and PCBs.     

Lead dynamics in the forest floor and mineral soil in south-central Ontario

Recent studies have suggested that the residence time of Pb in the forest floor may not be as long as previously thought, and there is concern that the large pulse of atmospheric Pb deposited in the 1960s and early 1970s may move rapidly through mineral soils and eventually contaminate groundwater. In order to assess Pb mobility at a woodland (JMOEC) in south-central Ontario, a stable Pb isotope tracer ²⁰⁷Pb (8 mg m^–2) was added to the forest floor in white pine (Pinus strobus) and sugar maple (Acer saccharum) stands, respectively, and monitored over a 2-year period. Excess ²⁰⁷Pb was rapidly lost from the forest floor. Applying first-order rate coefficients (k) of 0.57 (maple) and 0.32 (pine) obtained from the tracer study, and estimates of Pb deposition in the region, current predicted Pb concentrations in the forest floor are 1.5–3.1 and 2.1–5.8 mg kg^–1 in the maple and pine plots, respectively. These values compare favorably with measured concentrations (corrected for mineral soil contamination) of 3.1–4.3 mg kg^–1 in the maple stand and 2.6–3.6 mg kg^–1 in the pine stand. The response time (1/^k) of Pb in the forest floor at the sugar maple and white pine plots was estimated to be 1.8 and 3.1 years, respectively. The rapid loss of Pb from the forest floor at the JMOEC is much greater than previously reported, and is probably due to the rapid rate of litter turnover that is characteristic of forests with mull-type forest floors. In a survey of 23 forested sites that border the Precambrian Shield in south-central Ontario, Pb concentrations in the forest floor increased exponentially with decreasing soil pH. Lead concentrations in the forest floor at the most acidic survey sites, which exhibited mor-type forest floors, were approximately 10 times higher (80 mg kg^–1) than at the JMOEC, and pollution Pb burdens were up to 25 times greater. Despite the rapid loss of Pb from the forest floor at the JMOEC, the highest pollution Pb concentrations were found in the upper (0–1 cm) mineral soil horizon. Lead concentrations in the upper 30 cm of mineral soil were strongly correlated with organic matter content, indicating that pollution Pb does not move as a pulse down the soil profile, but instead is linked with organic matter distribution, indicating groundwater contamination is unlikely.     

Partial identification and copper tolerance of soil bacteria from copper-impregnated bog and from a salt marsh

Abstract

Bacteria from two areas in Wales have been extracted and partially identified. The areas are a copper impregnated bog in the Coed-Y-Brenin Forest with low pH and high carbon and copper content, and the Morfa Harlech salt marshes which have neutral pH and lower copper and carbon. Bacillus spp. was the predominant bacterium in both soils, but there was increased diversity of bacteria in the salt marsh soils. Bacteria from the Cu-rich, Coed-Y-Brenin soils showed higher growth densities in nutrient agar plates containing 10, 30 and 100 μg cm^?3 Cu than bacteria from the salt marsh soils, indicating that bacteria from the Coed-Y-Brenin soils could tolerate higher copper concentrations. Pseudomonas spp. from both study areas grew better in media with added Cu at low levels. The possibility is discussed that the bacteria play a part in the bioavailability of Cu particularly in the copper-rich Coed-Y-Brenin area.     

Lead, copper, zinc, and magnesium content in hair of children and young people with some neurological diseases

The lead, copper, zinc, and magnesium levels of scalp hair taken from 153 children aged 1–15 yr and young people (16–18 yr) with selected neurological disorders (hyperexcibility, loss of consciousness, and epileptiform convulsions of an unknown origin, etc.), were measured using the atomic absorption spectrometry method and then compared with a control group of healthy children (n=108). The research indicated significantly reduced mean levels of magnesium in the hair of children suffering from selected neurological diseases (in children aged 11–15 yr of age, above 30%; up to 5 yr of age, nearly 30%; the differences were statistically significant at p<0.05) and slightly decreased mean levels of copper (differences statistically significant at p<0.05, particularly in the 11 to 15-yr category). Differences in zinc levels in hair were inconsiderable (not statistically significant in any age groups). The lead level in the hair of the above-mentioned group of children was exceeded in relation to the control group (a statistically significant difference at p<0.05 for the total group). A more than twofold decrease in the mean value of the Mg/Pb ratio (and a nearly 30% decrease in the value of the Mg/Zn ratio) in the hair of children suffering from neurological diseases suggests that the high toxicity of lead accompanying, among other things, magnesium deficiencies might be a cause of the observed disorders in children.     

Control of microbial contamination for large-scale photoautotrophic micropropagation

Summary Photoautotrophic (sugar-free) micropropagation has been examined for many different plant species. One of the advantages of photoautotrophic micropropagation is the low risk of contamination, which facilitates the use of large culture vessels, and thus contributes to the reduction in production cost. In this article, pathogenic and nonpathogenic contaminations are discussed, and guidelines for development of large-scale, pathogen-free, photautotrophic micropropagation systems are introduced. A preliminary experiment was conducted for producing pathogen-free plantlets by large-scale photoautotrophic micropropagation. Addition of AgNO₃ in the medium was shown to suppress growth of nonpathogenic contaminants without reducing fresh and dry weight, and number of leaves of the tomato plantlets.     

A fugacity model for soil vapor extraction

A relatively simple fugacity‐based model is developed for predicting the effectiveness of soil vapor extraction (SVE), an in situ soil remediation technique used for removing volatile organic chemicals from unsaturated soils. The model accounts for the natural processes of volatilization, degradation, and leaching, as well as gas‐phase advection due to SVE. Model predictions are compared with published data for a field‐scale SVE operation. An exponentially declining sweep efficiency for SVE is introduced to improve the fit between simulated and measured soil extraction gas concentrations. The model permits the magnitudes of the various processes affecting the fate and transport of 1,1,1‐trichloroethane (TCA) and perchloroethylene (PCE) in soils to be evaluated. Without SVE, the dominant removal process is biodegradation, but the rate of degradation is low, requiring more than 9 years for soil gas concentrations from a spill of about 13 kg of TCA to be reduced to a concentration of 0. 001 μg/l. The removal time may be reduced to only about 2 years if SVE is used. Moreover, substantially less chemical leaches into the underlying groundwater, greatly reducing the potential extent of ground water contamination.     

The effects of contamination of soil with copper,lead and arsenic on the growth and composition of plants

Summary Accumulations of copper, lead and arsenic in soils affected by orchard sprays or mining were investigated in relation to their effects on growth and composition of plants. Seasonal variations in concentrations of the elements in pasture plants sampled from contaminated soils in the field are reported. The effects of soil temperature and applications of the nutrients P, S and N on the composition of plants grown in contaminated soils were investigated in glasshouse experiments.The copper concentrations of pasture species sampled from sites which were formerly orchards were usually high (20 to 60 mg kg^–1) during most of the growing season and may present some risk of toxicity to grazing ruminant animals. Lead (0.8 to 21 mg kg^–1) and arsenic (<0.2 to 5.8 mg kg^–1) concentrations were within, or close to the normal range of concentration in plants. In the glasshouse experiments, soil temperature was found to be an important factor in the uptake of copper, lead and arsenic. There were significant differences in uptake between genotypes. Applications of fertilizers at rates equivalent to those used for commercial vegetable production generally resulted in small decreases in the concentrations of copper, lead and arsenic concentrations in silver beet.     

重金属污染土壤植物修复的研究进展和应用前景

土壤污染是当今面临的一个严峻的问题。其中重金属污染尤为严重。因此重金属污染土壤的修复日益受到各国政府和学者的重视。植物修复技术作为一种绿色安全的技术以其潜在的高效、经济及生态协调性成为当前国际学术界研究的热点领域。就植物修复技术的概念、方法原理、植物修复技术的研究历史和现状以及优点、应用前景作了系统阐述,并介绍了国内外开展的一些应用性实例。指出了植物修复技术当前还存在的问题。对今后发展的方向。作出了几点展望。     

Treatment with Ca(OH)2 for inactivation of Salmonella Typhimurium and Enterococcus faecalis in soil contaminated with infected horse manure

Aim: To investigate the inactivation of Salmonella enterica serovar Typhimurium and the faecal indicator Enterococcus faecalis in horse manure:soil mixtures by application of hydrated lime (Ca(OH)₂). Methods and Results: In laboratory incubations, the inhibitory effect of different concentrations of Ca(OH)₂, as well as different application techniques, was tested. Other variables were horse manure:soil ratio, incubation temperature (6 and 14°C) and soil type (sand/clay). Bacterial enumeration by the plate count method in samples taken at increasing intervals revealed that Ca(OH)₂ effectively reduced Salmonella Typhimurium numbers. However, to achieve a sufficient reduction, the Ca(OH)₂ had to be applied at a sufficient rate, and the amount required varied because of manure:soil ratio and incubation temperature. The results showed that a pH above 11 was needed and that a high pH had to be maintained for up to 7 days. An appropriate application technique for the Ca(OH)₂ was also important, so that a high pH was obtained throughout the whole material to be treated. In addition, a high manure:soil ratio in combination with a higher incubation temperature was found to rapidly neutralize the pH and to increase the risk of Salmonella re‐growth. Conclusions: Application of Ca(OH)₂ can be an efficient method for treating a Salmonella‐contaminated horse paddock. A high pH is a key factor in Salmonella inactivation, and thus, monitoring the pH during the treatment period is necessary. To avoid re‐growth excess manure should be removed for separate treatment elsewhere. Significance and Impact of the Study: Persistence of Salmonella in horse paddocks poses a risk of disease transmission to healthy animals and people who come into contact with these animals. An efficient method to de‐contaminate a Salmonella‐contaminated soil would be a valuable tool for animal welfare and for public health.