Sequential extraction analysis of lead in Michigan roadside soils: Mobilization in the vadose zone by deicing salts?

Sequential extraction analysis was used to characterize the geochemical partitioning of Pb in roadside soils of the Detroit, MI area. Four soil profiles (10, 30, 60, and 100 m from road) were sampled at 15‐cm intervals to a depth of 75 cm at each of five locations along an urban‐rural transect. The observed concentrations increase with increasing traffic volume and proximity to the highway, indicating that vehicle emissions are the principal source of Pb. Concentrations in roadside soils of urban sites (>100,000 vehicles per 24 h) are 10 to 15 times greater than the background level of 12 to 22 mg/kg found at rural sites. Sequential extraction data show that the Pb is mainly in carbonate and oxide forms in the most heavily contaminated soils; organically bound forms tend to predominate elsewhere. Both surface and subsurface horizons of soils are polluted at urban sites where translocation in the vadose zone is suggested by elevated levels of Pb to depths of 75 cm. Mobilization is attributed primarily to partial dissolution of organic matter by excess NaCl derived from highway deicing salts and complex‐ation of Pb with organic chelates. Mobilization appears to be occurring in soils up to 60 m from the highway at urban sites.     

Stabilization Pb,Zn, and Cd-Contaminated Soil By Means of Natural Zeolite

This article aims to investigate the stabilization of Pb, Zn, and Cd contained in contaminated soil from a former mining site in Montevecchio, Sardinia, using clinoptilolite-rich tuff from Pentalofos, Evros. The study included (1) batch experiments and their environmental characterization and (2) column experiments. The first tests involved 1-month pot experiments with varying soil-zeolite mixtures, and their evaluation was carried out by standard USEPA leaching tests (TCLP, EPT test, SPLP). Moderate solubility reductions were recorded according to the TCLP (Pb: 38%, Zn: 33%, and Cd: 32%) due to the introduction of competing Na ions in the solution, while the EPT test showed more significant variations (Pb: 55%, Zn: 74%, and Cd: 46%). A major decrease is achieved in both cases by 10% w/w zeolite addition. The study was complemented by column experiments involving soil-zeolite mixtures eluted by CH3COOH solutions (0.003N and 0.05N). The solubility of Pb was reduced by 50 to 60% compared with the control column, thus indicating the considerable selectivity of clinoptilolite for Pb. In addition, Na and Ca measurements in the leachates confirmed that the immobilization of Pb was mainly attributed to ion exchange reactions.     

The effect of calcium concentration on the toxicity of copper, lead and zinc to yolk-sac fry of brown trout, Salmo trutta L., in soft, acid water

Yolk-sac fry of brown trout were exposed to three levels of single trace metals (Cu, 20,40,80 nmol 1^-1; Pb, 12·5,25,50 nmol 1^-1; Zn, 75,150,300 nmol 1^-1) typical of concentrations reported for acid soft waters, in flowing, artificial, soft water media maintained at pH 4·5 and [Ca] of 20 or 200 μmol 1^-1for 30 days.
Mortalities were high in fry subjected to all levels of the three trace metals at [Ca] 20 μmol 1^-1, with 80% of the total deaths occurring between days 11 and 15 of the experiment. 25% mortality occurred at low [Ca] and pH 4·5 in the absence of trace metals, with only one death recorded at [Ca] 200 μmol1^-1'(Cu, 80 nmol 1^-1). At high [Ca] all three levels of Cu and Pb impaired net Na and K uptake; Cu was the only metal to reduce the uptake of Ca. The Zn treatments had no significant effect on mineral uptake. Calcification of centra was reduced by all three Cu treatments at [Ca] 200 μmol 1^-1. The lowest Zn concentration (75 nmol 1^-1) was the only other treatment to impair skeletal development. In the absence of trace metals, low [Ca] significantly reduced Ca, Na and K uptake, skeletal calcification and dry mass at pH 4·5.
The deleterious effects of low Cu, Pb and Zn concentrations at low pH and low [Ca], and the ameliorative effect of higher ambient [Ca], are discussed in relation to fishery status in soft, acid waters.     

Metal Phytoremediation by the Halophyte Limoniastrum monopetalum (L.) Boiss: Two Contrasting Ecotypes

The phytoremediation potential of the halophyte Limoniastrum monopetalum for the removal of Cd and Pb from polluted sites is assessed in this work. Two pot experiments were conducted; the first with wild L. monopetalum grown on soil polluted with Cd and Pb irrigated at different salinities, and the second with commonly cultivated ornamental L. monopetalum grown on soil polluted with Cd irrigated also at different salinities. The data revealed that wild L. monopetalum is a Cd and Pb tolerant plant able to accumulate at least 100 ppm of cadmium in its shoots without showing any significant decrease in terms of biomass production, chlorophyll content or water content suggesting that it could be an accumulator of Cd. Pb above-ground accumulation was kept at low levels with the majority of Pb localized in the roots. On the other hand, contrasting results were obtained for ornamental L. monopetalum which although it was found to be also Cd tolerant, Cd accumulation in its tissues was kept at significantly lower levels especially compared to that of the wild ecotype. In addition for ornamental L. monopetalum salinity did not have a positive effect on Cd accumulation and translocation as observed in the wild type and in other halophytes. Analysis of the salt excretion crystals on the leaf surface confirmed that wild and cultivated ornamental L. monopetalum excrete cadmium and lead through their salt glands as a possible metal detoxification mechanism, although the amount excreted by the ornamental L. monopetalum is significantly less.     

Using persuasive messages to encourage hunters to support regulation of lead shot

Lead shot from hunting adds the toxic metal to environments worldwide. The United States banned lead shot for hunting waterfowl in 1991 and 26 states have lead shot restrictions beyond those mandated for waterfowl hunting. The Minnesota Department of Natural Resources (MDNR) was interested in studying hunter attitudes about expanded restrictions on the use of lead shot for hunting small game to understand what communication strategies might increase public support for potential restrictions on lead shot. We mailed messages about lead shot, including 1,200 control messages and 400 of each of 9 treatment messages, and surveys to 4,800 resident small game hunters. We compared attitudes and intentions related to a possible ban among control and treatment groups. Compared to the control message, all treatment messages elicited more positive attitudes and intentions to support a ban. A basic factual message, messages with references to Ducks Unlimited, and a first-person narrative message generated the strongest support for a ban. Results also demonstrated a substantial relationship between the use of lead shot and response to persuasive messages supporting a ban. © 2012 The Wildlife Society.     

Engineering a CD4 mimetic inhibiting the binding of the human immunodeficiency virus-1 (HIV-1) envelope glycoprotein gp120 to human lymphocyte CD4 by the transfer of a CD4 functional site to a small natural scaffold

The solvent-exposed CDR2-like region of human CD4 was transferred to the structural scaffold of scorpion charybdotoxin, as a means to reproduce that site in a native-like conformation. The chimeric mini-protein (33 amino acids long), obtained by solid-phase synthesis, is able to specifically prevent the interaction of HIV-1 gp120 with CD4. This CD4 mimetic may represent a valuable tool in the study of the HIV–cell interactions and as a lead in the development of antiviral drugs.     

Quality control and statistical modeling for environmental epigenetics: A study on in utero lead exposure and DNA methylation at birth

DNA methylation data assayed using pyrosequencing techniques are increasingly being used in human cohort studies to investigate associations between epigenetic modifications at candidate genes and exposures to environmental toxicants and to examine environmentally-induced epigenetic alterations as a mechanism underlying observed toxicant-health outcome associations. For instance, in utero lead (Pb) exposure is a neurodevelopmental toxicant of global concern that has also been linked to altered growth in human epidemiological cohorts; a potential mechanism of this association is through alteration of DNA methylation (e.g., at growth-related genes). However, because the associations between toxicants and DNA methylation might be weak, using appropriate quality control and statistical methods is important to increase reliability and power of such studies. Using a simulation study, we compared potential approaches to estimate toxicant-DNA methylation associations that varied by how methylation data were analyzed (repeated measures vs. averaging all CpG sites) and by method to adjust for batch effects (batch controls vs. random effects). We demonstrate that correcting for batch effects using plate controls yields unbiased associations, and that explicitly modeling the CpG site-specific variances and correlations among CpG sites increases statistical power. Using the recommended approaches, we examined the association between DNA methylation (in LINE-1 and growth related genes IGF2, H19 and HSD11B2) and 3 biomarkers of Pb exposure (Pb concentrations in umbilical cord blood, maternal tibia, and maternal patella), among mother-infant pairs of the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) cohort (n = 247). Those with 10 μg/g higher patella Pb had, on average, 0.61% higher IGF2 methylation (P = 0.05). Sex-specific trends between Pb and DNA methylation (P < 0.1) were observed among girls including a 0.23% increase in HSD11B2 methylation with 10 μg/g higher patella Pb.     

Integration of the Predictions of Two Models with Dose Measurements in a Case Study of Children Exposed to the Emissions from a Lead Smelter

The predictions of two source-to-dose models are evaluated with observed data collected in a village polluted by an operating secondary lead smelter. Both models were built up from several sub-models linked together and run using Monte-Carlo simulation. The first model system provides the distribution of the media-specific lead concentrations (air, soil, fruit, vegetables, and blood) in the whole area investigated. The second model provides an estimate of the concentration of exposure of specific individuals living in the study area. The predictions of the first model system were improved by performing a sensitivity analysis and using field data to correct the default value provided for the leaf wet density. However, in this case study, the model system tends to overestimate the exposure due to exposed vegetables. The second model was tested for nine children with contrasting exposure conditions. It managed to capture the blood levels for eight of them. In the last case, the exposure of the child by pathways not considered in the model may explain the failure of the model. The interest of this integrated model is to provide outputs with lower variance than the first model system, but further tests are necessary to conclude about its accuracy.