Use of the IEUBK Model for Determination of Exposure Routes in View of Site Remediation

The Integrated Exposure Uptake Biokinetic (IEUBK) model is frequently used to estimate blood lead concentrations of children exposed to lead. Simulations with the IEUBK model were run to estimate the blood lead concentration in children living in the vicinity of a non-ferrous plant, situated in Hoboken, Belgium. Concentrations in soil ranged from 59–2425 mg Pb/kg dm, average concentrations in house dust ranged from 234–73394 mg Pb/kg dm. Measured blood lead concentrations in children aged 2–7 years were between 3 and 35 μ g/dl. Exposure sources were indoor dust in the house and the school, outdoor dust and soil in the home surrounding and at the school's playground, and suspended dust in the air. Soil ingestion values and lead exposure from food were changed to Flemish values. The model was able to predict the measured blood lead concentrations adequately except for the lowest exposure group. Predictions showed a systematic overestimation. Analysis of the data revealed that the neighbourhood's school is an important source of exposure to lead; indoor house dust dominates exposure for children going to school outside the area, because of the high concentrations of lead in indoor dust (3 to 5 times higher than in outdoor soil).     

Chemically enhanced phytoextraction of risk elements from a contaminated agricultural soil using Zea mays and Triticum aestivum: performance and metal mobilization over a three year period

Enhanced phytoextraction using EDTA for the remediation of an agricultural soil contaminated with less mobile risk elements Cd and Pb originating from smelting activities in Príbram (Czech Republic) was assessed on the laboratory and the field scale. EDTA was applied to the first years crop Zea mays. Metal mobilization and metal uptake by the plants in the soil were monitored for two additional years when Triticum aestivum was planted. The application ofEDTA effectively increased water-soluble Cd and Pb concentrations in the soil. These concentrations decreased over time. Anyhow, increased concentrations could be still observed in the third experimental year indicating a low possibility of groundwater pollution after the addition of EDTA during and also after the enhanced phytoextraction process under prevailing climatic conditions. EDTA-applications caused phytotoxicity and thereby decreased biomass production and increased Cd and Pb uptake by the plants. Phytoextraction efficiency and phytoextraction potential were too low for Cd and Pb phytoextraction in the field in a reasonable time frame (as less than one-tenth of a percent of total Cd and Pb could be removed). This strongly indicates that EDTA-enhanced phytoextraction as implemented in this study is not a suitable remediation technique for risk metal contaminated soils.     

两个育性相关基因在几类小麦雄性不育材料中的表达研究

以1B/1R类K型不育系K3314A及其保持系3314B,非1B/1R类K型不育系732A及其保持系732B,YS温敏雄性不育小麦A3017为材料,提取不同温度处理下各时期小穗的总RNA进行反转录,对AY914051和AY660990两个目标基因进行半定量PCR和电泳分析,测定其在小麦中的表达变化趋势,以分析其与这几种不育系的育性相关关系,探讨这几种不育小麦败育的关键发育时期。结果表明,除AY914051基因在2种保持系3314B和732B中表达量变化不大之外,其它均有明显差异;2个目标基因与这几种雄性不育系的败育有关,但与育性相关程度不同,不育系两个目的基因的表达受温度变化影响程度明显大于保持系。由实验结果推测,1B/1R类K型不育系、非1B/1R类K型不育系和YS温敏雄性不育系的败育关键时期为单核期或单核期至二核期之间;温度差异可能会导致YS温敏雄性不育系的育性相关基因表达时期错位,错位后的表达差异积累可能最终导致其败育。     

粗毛栓菌和蜡状芽孢杆菌及其共固定菌对pb2+的吸附

将粗毛栓菌菌丝球与蜡状芽孢杆菌共固定为共固定菌.以粗毛栓菌菌丝球、蜡状芽孢杆菌和共固定菌为研究对象,测定不同吸附时间、初始pH、吸附剂浓度和pb2+浓度对3种生物吸附剂吸附pb2+的影响,并将3种生物吸附剂吸附pb2+前后的红外吸收光谱进行分析比较.结果表明:在吸附剂浓度为2g.L-1、pH为5.0、pb2+浓度为50 mg·L-1条件下对pb2+吸附lh效果良好,其吸附率分别为71.7％、91.0％和96.9％.生物吸附剂红外光谱主要由蛋白质、碳水化合物和含硫、磷酸基团的吸收带组成,表明对pb2+吸附起主要作用的官能团是羟基、羧基、磷酸基和含硫基团.     

Plants inhabiting polygons for megapolis waste as promising species for phytoremediation

Screening of ruderal plant species inhabiting polygons for solid waste (SW) burying contaminated with heavy metals (HM). Among these plants, wood small-reedgrass (Calamagrostis epigeios L. Roth) was found; this plant is a perennial grass characterized by the highest level of HM, especially Ni, accumulation. The content of Ni was 703 mg/kg dry wt in wood small-reedgrass leaves and 346 mg/kg dry wt in its rhizomes. On the SW polygon closed 15 years ago, wood small-reedgrass produced a monoculture of high productivity (15 centner/ha), and this provided for extraction of HM moved from SW layers and maintenance of their concentrations in covering soil at the level not dangerous for plants (by 5–10 times below the threshold level). Under constant conditions, the tolerance of wood small-reedgrass seed germination to HM was established. Adult plants turned out to be tolerant to periodic mowing; they were capable of HM accumulation in above-ground organs; they also accumulated the osmorprotectant proline. It was concluded that wood small-reedgrass could be used for SW polygon recultivation and within the lawn grass mixtures for near-road lawns in cities.     

Assessing Lead Risks at Non-Residential Hazardous Waste Sites

In 1996, the U.S. Environmental Protection Agency (USEPA) developed the Adult Lead Methodology (ALM) to provide an interim approach to assessing risks from non-residential exposures to lead. Because such exposures often involve occupational activities of adults, the ALM was directed at assessing soil-related lead risks to adults. Consistent with other approaches used in Superfund risk assessment, the ALM was designed to predict quasi-steady state blood lead concentrations (PbB) that might result from soil exposure. These predictions are converted to a risk estimate, expressed as the probability of exceeding a PbB level of concern. To examine the assumptions and variables in the ALM that have become available since 1996, a comparison was made of the attributes of seven alternative research models for which adequate documentation is available to understand and implement each approach. Several of these models have been used in regulatory decision-making; however, the USEPA has officially embraced none for general use. This analysis suggests that the ALM can continue to serve as a reasonable tool for assessing risks associated with non-residential exposures to soil. Under certain circumstances other models may be more applicable (i.e., for assessing acute or intensive exposures); however, the ALM is recommended for the majority of risk assessment applications.     

Carbon and Nitrogen Mineralization of Lead Treated Soils in the Eastern Mediterranean Region,Turkey

The aim of this study was to determine the first effect of lead on microbial activity in soil. The study was carried out in the soil samples from four different radish (Raphanus sativus L. var. radicula, Brassicaceae) fields along the highway in a district (Kadirli, Osmaniye) of the Eastern Mediterranean Region, Turkey. After the calculation of Pb contents, the Pb amounts of the soil samples were brought up to 50 and 100 mg Pb kg^?1 by treatment with Pb(NO ₃ ) ₂ , and the samples for the carbon and the nitrogen mineralization were incubated under controlled conditions (28°C, constant moist). The carbon mineralization was determined by a CO ₂ respiration method for 30 days. The nitrogen mineralization was observed in vitro for 6 weeks. The untreated group was statistically different from the 50 and 100 mg Pb kg^?1 treatments in the aspect of the C(CO ₂ ) outlet during mineralization (P ≤ 0.05), but difference between the 50 and 100 mg Pb kg^?1 treatments was not significant. NH ₄ -N and NO ₃ -N contents of each soil were shown differences between across treatments. Based on these results, it is possible to conclude that the addition of 50 and 100 mg Pb kg^?1 provided a toxic effect threshold for the microbial activity into 30 days.     

Lead and Cadmium Contamination in Roadside Soils in Irbid City,Jordan: A Case Study

This study evaluates the amount and distribution of Pb and Cd in roadside soils adjacent to two main roads in Irbid, Jordan, from October 2001 to July 2002. A total of 260 samples were collected from Irbid-Howara Street and Yarmouk University Street. Lead and Cd content were measured using Graphite Furnace Atomic Absorption Spectrometry. The environmental significance of this study is discussed in terms of the influence of traffic density on Pb and Cd concentrations in roadside soils, and enrichment factors were calculated to evaluate the degree of pollution. The accuracy of the results obtained has been examined and two standard reference materials, CRM 142 R (soil) and SRM 2709 (soil), were analyzed to confirm the accuracy of the results. The precision of the measurements was assessed in terms of relative standard deviation (RSD) using five replicate analyses of samples collected from the roadside sites. RSD values for Pb and Cd were found to be less than 6%. The overall Pb concentration in roadside soil samples was 325 and 431 μg g^?1 for Pb and 1.142 and 1.135 μg g^?1 for Cd in Yarmouk University Street and Irbid-Houwa Street, respectively. Results indicated that levels of Pb and Cd were decreasing as the distance from the road increases. Enrichment factor results were 655 and 826 for Pb, and 252 and 237 for Cd in Yarmouk University Street and Irbid-Houwa Street, respectively.     

Oxidative stress induced by lead, cadmium and arsenic mixtures: 30-day, 90-day, and 180-day drinking water studies in rats: An overview

Humans are frequently exposed to combinations of lead (Pb), cadmium (Cd) and Arsenic (As) but there is a paucity of actual data on the molecular effects of these agents at low dose levels. The present factorial design studies were undertaken in rats to examine the effects of these agents at LOEL dose levels on a number of molecular parameters of oxidative stress in hematopoietic and renal organ systems following oral exposure in drinking water at 30, 90 and 180 day time points. Results of these studies demonstrated dynamic, time-dependent alterations in both molecular targets and inducible oxidative stress protective systems in target cell populations. In general, cellular protective systems, which protected against oxidative damage at the 90 day time point, appeared to be finite such that molecular manifestations of oxidative stress became statistically significant at the 180 day time point for several of the combination exposure groups. These data demonstrate the importance of duration of exposure in assessing the toxic potential of Pb, Cd and As mixtures at low dose levels.     

Distribution and Toxic Effects of Cadmium and Lead on Maize Roots

Two-day-old seedlings of maize (Zea mays L.) were incubated on Cd and Pb nitrate solutions at the concentrations that inhibited root growth approximately by 50% after two-day-long incubation (LC₅₀; 10^–4 and 10^–3 M, respectively) or completely terminated growth of the primary root after one-day-long incubation (LC; 5 × 10^–4 and 10^–2 M, respectively). Cd and Pb contents were measured using an anodic inversion voltammetric technique in a flow injection system and a histochemical method. At LC₅₀, Cd and Pb were discerned, by histochemical techniques, in all root apical tissues, whereas in the root hair zone, the heavy metals were primarily accumulated in the apoplast of the rhizodermis and cortex and to a lesser extent, in the vascular tissues and parenchyma cells surrounding the metaxylem vessels. Insignificant accumulation of Cd and Pb in the pericycle probably explains why root branching was tolerant to these agents. At LC, Cd and Pb were found in the apoplast of all root tissues, in accordance with the practically complete inhibition of root growth and branching. Irrespectively of Cd and Pb concentrations in the external solution, the metal contents in the root apex exceeded those in the basal region. Procion dyes were used to assess cell death inflicted by Cd and Pb. At LC, the root cap and meristematic cells perished, together with the rhizodermal cells and the outer cortical cells of the root apex, whereas only the rhizodermal cells in the root apical region died at LC₅₀. The evidence that Cd and Pb cross the endodermal barrier at LC presumes that, at lower metal concentrations, the Casparian strip and plasmalemma of the endodermis regulate the transport of these metals into the central cylinder. The authors conclude that the identical barriers control Cd and Pb transport in root tissues.