Soil contamination with radionuclides and potential remediation

Soils contaminated with radionuclides, particularly 137Cs and 90Sr, pose a long-term radiation hazard to human health through exposure via the foodchain and other pathways. Remediation of radionuclide-contaminated soils has become increasingly important. Removal of the contaminated surface soil (often up to 40 cm) or immobilization of radionuclides in soils by applying mineral and chemical amendments are physically difficult and not likely cost-effective in practicality. Reducing plant uptake of radionuclides, especially 137CS and 90Sr by competitive cations contained in chemical fertilizers has the general advantage in large scale, low-level contamination incidents on arable land, and has been widely practiced in central and Western Europe after the Chernobyl accident. Phytoextraction of radionuclides by specific plant species from contaminated sites has rapidly stimulated interest among industrialists as well as academics, and is considered to be a promising bio-remediation method. This paper examines the existing remediation approaches and discusses phytoextraction of radionuclides from contaminated soils in detail.     

Measurement of fluorescence decay of crude oil: a potential technique to identify oil slicks

The single photon counting technique has been used to measure the decay time for several Kuwaiti crude and refined oils. Fluorescent characteristics of two different bunker oils from widely separate geographic areas have been studied. Laser induced fluorescent data for the crude oil samples are compared with the decay time results to evaluate the potential of these techniques for the identification of oil sticks in the marine environment. Response of the oil film thickness to various excitation wavelengths from a CW Ar ion laser and a pulsed xenon lamp has been investigated.     

Plants' use of different nitrogen forms in response to crude oil contamination

In this study, we investigated Phragmites australis’ use of different forms of nitrogen (N) and associated soil N transformations in response to petroleum contamination. ¹⁵N tracer studies indicated that the total amount of inorganic and organic N assimilated by P. australis was low in petroleum-contaminated soil, while the rates of inorganic and organic N uptake on a per-unit-biomass basis were higher in petroleum-contaminated soil than those in un-contaminated soil. The percentage of organic N in total plant-assimilated N increased with petroleum concentration. In addition, high gross N immobilization and nitrification rates relative to gross N mineralization rate might reduce inorganic-N availability to the plants. Therefore, the enhanced rate of N uptake and increased importance of organic N in plant N assimilation might be of great significance to plants growing in petroleum-contaminated soils. Our results suggest that plants might regulate N capture under petroleum contamination.     

Effect of crude oil contamination on the chlorophyll content and morpho-anatomy of Cyperus brevifolius (Rottb.) Hassk

Chlorophyll plays a pivotal role in the plant physiology and its productivity. Cultivation of plants in crude oil contaminated soil has a great impact on the synthesis of chlorophyll pigment. Morpho-anatomy of the experimental plant also shows structural deformation in higher concentrations. Keeping this in mind, a laboratory investigation has been carried out to study the effect of crude oil on chlorophyll content and morpho-anatomy of Cyperus brevifolius plant. Fifteen-day-old seedling of the plant was planted in different concentrations of the crude oil mixed soil (i.e., 10,000, 20,000, 30,000, 40,000, and 50,000 ppm). A control setup was also maintained without adding crude oil. Results were recorded after 6 months of plantation. Investigation revealed that there is a great impact of crude oil contamination on chlorophyll content of the leaves of the experimental plant. It also showed that chlorophyll a, chlorophyll b, and total chlorophyll content of leaves grown in different concentrations of crude oil were found to be lower than those of the control plant. Further, results also demonstrated that chlorophyll content was lowest in the treatment that received maximum dose of crude oil. It also showed that chlorophyll content was decreased with increased concentration of crude oil. Results also demonstrated that there was a reduction in plant shoot and root biomass with the increase of crude oil concentration. Results also revealed that the shoot biomass is higher than root biomass. Morphology and anatomy of the experimental plant also show structural deformation in higher concentrations. Accumulation of crude oil on the cuticle of the transverse section of the leaves and shoot forms a thick dark layer. Estimation of the level of pollution in an environment due to oil spill is possible by the in-depth study of the harmful effects of oil on the morphology and anatomy and chlorophyll content of the plants grown in that particular environment.     

Advances in understanding ozone impact on forest trees: Messages from novel phytotron and free-air fumigation studies

Recent evidence from novel phytotron and free-air ozone (O₃) fumigation experiments in Europe and America on forest tree species is highlighted in relation to previous chamber studies. Differences in O₃ sensitivity between pioneer and climax species are examined and viewed for trees growing at the harsh alpine timberline ecotone. As O₃ apparently counteracts positive effects of elevated CO₂ and mitigates productivity increases, response is governed by genotype, competitors, and ontogeny rather than species per se. Complexity in O₃ responsiveness increased under the influence of pathogens and herbivores. The new evidence does not conflict in principle with previous findings that, however, pointed to a low ecological significance. This new knowledge on trees' O₃ responsiveness beyond the juvenile stage in plantations and forests nevertheless implies limited predictability due to complexity in biotic and abiotic interactions. Unravelling underlying mechanisms is mandatory for assessing O₃ risks as an important component of climate change scenarios.     

The impact of crude oil prices on Chinese stock markets and selected sectors: evidence from the VAR-DCC-GARCH model

Environmental Science and Pollution Research - The interaction between oil and stock market returns is one of the most important relationships that have a significant influence on the economy of...     

油田含油污泥超声脱油的研究

在油田含油污泥的热洗处理中引入超声辐照处理技术,研究考察了超声脱油技术中超声强度,超声辐照时间,含油污泥预热温度,清洗液用量和清洗液回用4个试验操作条件对污泥脱油的影响,认为在优化条件（超声发生器输出电压175 V,辐照时间15 min,预热温度55 ℃,清洗液和含油污泥以质量比8∶1）下,超声脱油技术可以把污泥的干基油含量由0.35 g/g降低到0.14 g/g,同时也证明清洗液可以反复使用。根据简单的经济核算,处理1 t含油污泥可以产出66元的效益。研究表明,使用超声处理可以有效地提高含油污泥的污油脱除效率,明显降低污泥清洗的操作温度。     

Understanding biochemical defense and phytoremediation potential of Leucas aspera in crude oil polluted soil

Environmental Science and Pollution Research - The phytoremediation potential and enzymatic defense of a medicinal herb Leucas aspera was studied in the crude oil contaminated soil. The...     

Adsorption of crude oil on arctic terrain

Arctic terrain was divided into three layers, moss, detritus and clay, and each layer was contacted with Norman Wells crude oil. Chromatographic analysis of the crude oil extracts of the terrain layers showed that the adsorption capacity of the terrain increased with increasing organic content. The higher molecular weight n-alkanes were adsorbed to a greater extent than lower n-alkanes on the moss and detritus layers. Of the aromatics, p-xylene was adsorbed to a greater extent than benzene on all three layers of the terrain. Retention of crude oil components on Arctic terrain in the event of an oil spill would be in accord with these findings.     

Assessment of crude oil biodegradation in arctic seashore sediments: effects of temperature,salinity, and crude oil concentration

The expected increase in offshore oil exploration and production in the Arctic may lead to crude oil spills along arctic shorelines. To evaluate the potential effectiveness of bioremediation to treat such spills, oil spill bioremediation in arctic sediments was simulated in laboratory microcosms containing beach sediments from Barrow (Alaska), spiked with North Slope Crude, and incubated at varying temperatures and salinities. Biodegradation was measured via respiration rates (CO₂ production); volatilization was quantified by gas chromatography/mass spectrophotometry (GC/MS) analysis of hydrocarbons sorbed to activated carbon, and hydrocarbons remaining in the sediment were quantified by GC/flame ionization detector (FID). Higher temperature leads to increased biodegradation by naturally occurring microorganisms, while the release of volatile organic compounds was similar at both temperatures. Increased salinity had a small positive impact on crude oil removal. At higher crude oil dosages, volatilization increased, however CO₂ production did not. While only a small percentage of crude oil was completely biodegraded, a larger percentage was volatilized within 6–9 weeks.     

Cadmium contamination in orchard soils and fruit trees and its potential health risk in Guangzhou, China

This study examines cadmium (Cd) contamination in orchard soils and fruit trees in Guangzhou, China, and assesses its potential health risk. Soils and tissues samples of three species of fruit trees were collected from three orchards. The average soil Cd concentration was 1.27, 1.84 and 0.68 mg/kg in orchards I, II, and III, respectively. The carambola (Averrhoa carambola) accumulated exceptionally high concentrations of Cd (7.57, 10.84, 9.01 and 2.15 mg/kg dw in root, twig, leaf and fruit, respectively), being 6.0-24 times and 4.0-10 times the corresponding tissue Cd in the longan (Dimocarpus longan) and wampee (Clausena lansium), respectively. Furthermore, all Cd concentrations (0.04-0.25 mg Cd/kg fw) of the fruits exceeded the tolerance limit of cadmium in foods of PR China (0.03 mg/kg fw). Our results indicate that the carambola tree has high Cd accumulation capacity and might be a Cd accumulator; and its fruit, among the three species of fruits studied, also poses the highest potential health risk to local residents.     

利用生物柴油去除滨海构筑物上原油的模拟研究简

溢油向岸滩漂移会造成海岸带人工构筑物的严重污染。采用混凝土片模拟滨海构筑物,研究投加生物柴油及营养对石油污染物的去除效果。结果表明,施加生物柴油可以促进滨海构筑物上的石油进入水中,生物柴油施加量越大,构筑物上残余的石油量越小;同时施加生物柴油和营养能够促进海水中降解石油微生物的增殖和石油的降解;营养和微生物条件一致的情况下,投加2 mL和5 mL生物柴油的系统中石油的总去除率分别为37.5%和32.7%,表明生物柴油的投加量有一个适宜值。研究结果可为生物柴油-营养联合修复石油污染海岸带提供数据支持。     

利用生物柴油去除滨海构筑物上原油的模拟研究

溢油向岸滩漂移会造成海岸带人工构筑物的严重污染。采用混凝土片模拟滨海构筑物,研究投加生物柴油及营养对石油污染物的去除效果。结果表明,施加生物柴油可以促进滨海构筑物上的石油进入水中,生物柴油施加量越大,构筑物上残余的石油量越小;同时施加生物柴油和营养能够促进海水中降解石油微生物的增殖和石油的降解;营养和微生物条件一致的情况下,投加2 mL和5 mL生物柴油的系统中石油的总去除率分别为37.5%和32.7%,表明生物柴油的投加量有一个适宜值。研究结果可为生物柴油-营养联合修复石油污染海岸带提供数据支持。     

Effects of oil contamination on plant growth and development: a review

Environmental Science and Pollution Research - Oil spills generate several environmental impacts and have become more common with the increase in petroleum extraction, refining, transportation, and...     

Assessing the hydrocarbon degrading potential of indigenous bacteria isolated from crude oil tank bottom sludge and hydrocarbon-contaminated soil of Azzawiya oil refinery,Libya

The disposal of hazardous crude oil tank bottom sludge (COTBS) represents a significant waste management burden for South Mediterranean countries. Currently, the application of biological systems (bioremediation) for the treatment of COTBS is not widely practiced in these countries. Therefore, this study aims to develop the potential for bioremediation in this region through assessment of the abilities of indigenous hydrocarbonoclastic microorganisms from Libyan Hamada COTBS for the biotreatment of Libyan COTBS-contaminated environments. Bacteria were isolated from COTBS, COTBS-contaminated soil, treated COTBS-contaminated soil, and uncontaminated soil using Bushnell Hass medium amended with Hamada crude oil (1 %) as the main carbon source. Overall, 49 bacterial phenotypes were detected, and their individual abilities to degrade Hamada crude and selected COBTS fractions (naphthalene, phenanthrene, eicosane, octadecane and hexane) were evaluated using MT2 Biolog plates. Analyses using average well colour development showed that ~90 % of bacterial isolates were capable of utilizing representative aromatic fractions compared to 51 % utilization of representative aliphatics. Interestingly, more hydrocarbonoclastic isolates were obtained from treated contaminated soils (42.9 %) than from COTBS (26.5 %) or COTBS-contaminated (30.6 %) and control (0 %) soils. Hierarchical cluster analysis (HCA) separated the isolates into two clusters with microorganisms in cluster 2 being 1.7- to 5-fold better at hydrocarbon degradation than those in cluster 1. Cluster 2 isolates belonged to the putative hydrocarbon-degrading genera; Pseudomonas, Bacillus, Arthrobacter and Brevundimonas with 57 % of these isolates being obtained from treated COTBS-contaminated soil. Overall, this study demonstrates that the potential for PAH degradation exists for the bioremediation of Hamada COTBS-contaminated environments in Libya. This represents the first report on the isolation of hydrocarbonoclastic bacteria from Libyan COTBS and COTBS-contaminated soil.     

The effect of crude oil and oil spill chemicals on nitrogen fixation in the cyanobacteria Nostoc sp

The effects of crude oil and three oil spill dispersants (Corexit 9600, 9550 and 7664) on nitrogenase activity in the cyanobacteria Nostoc sp. were examined. The addition of oil to Nostoc sp. cultures resulted in a catastrophic decline in nitrogenase activity with activity ceasing 7 h after treatment. The addition of a dispersant with the oil did not ameliorate this effect. Cultures exposed to high concentrations of dispersants showed lower rates on nitrogenase activity than untreated cultures. However, it is unlikely that dispersant concentrations of this magnitude would occur in the field. At the lowest concentration tested, which approximates the manufacturer's recommended application rate, the effects of the dispersant appear to be negligible.     

影响原油生物降解因素的实验研究

以原油为唯一碳源,从长期被石油污染土壤中筛选出6株原油降解菌SY1~SY6,通过单因素实验研究初始pH、温度、充氧量(摇床转数)、盐浓度、氮源和磷源等环境因素和营养条件对各菌株生物降解原油的影响。实验结果表明:6株原油降解菌在初始pH7~9,温度30℃,摇床转速180 r/min时生长良好,且能有效地降解石油类污染物,其平均降解率为50%以上。6菌株在盐浓度在1%时生长良好,SY3菌和SY4菌能在盐浓度10%以上生长,具有一定的耐盐能力。同时,6菌株以氯化铵(NH4Cl)为氮源,磷酸氢二钾(K2HPO4)和磷酸二氢钾(KH2PO4)的混合物(2∶1)为磷源时生长良好,因此可作为各菌生长的最适氮源和磷源。研究结果可以为含油废水的处理提供微生物基础。     

原油对纳米SiO2/聚偏氟乙烯离子膜的污染及清洗技术研究

聚偏氟乙烯(PVDF)膜的疏水性限制了其在水处理领域的应用.采用纳米SiO2/PVDF离子膜电渗析对含原油高矿化度污水进行膜污染试验.结果表明,纳米SiO2/PVDF离子膜抗油珠污染的能力较强于PVDF膜.乳化油珠在电场的作用下向阴离子膜表面迁移,并在阴离子膜表面浓集、聚并,形成油膜,堵塞离子通道,少量原油以憎水膜的形式覆盖于活性基团上.扫描电镜和能谱分析表明,膜面有机污染物主要是石油类污染物,无机污染物主要是CaCO3等无机物污垢.原油污染的纳米Si02/PVDF离子膜的较佳清洗方法为碱-表面活性剂法.     

秸秆固定化石油降解菌降解原油的初步研究

用秸秆做载体固定嗜碱芽孢杆菌(Bacillus alcalophilus SG)降解原油,其原油去除率为73.88%,高于单纯投加菌液或者菌液与秸秆的混合物的原油去除率.秸秆的最佳投加量(干重)为25.0 g/L,最佳固定化时间为30 h.用预处理过的秸秆固定SG,降低了固定化SG的原油去除率.在固定化培养基中添加无机盐离子,促进了固定化SG对原油的降解.不同初始pH的原油培养基在固定化SG降解原油的过程中逐渐呈中性或偏碱性.固定化SG在pH 6.0～10.0时对原油均有不错的降粘能力.