Multiple kinetic Langmuir modeling to predict the environmental behaviour of As(v) in soils

A soil with a relatively high Fe content (2.82% [w/w]) was loaded for up to one year with As(v) by equilibrating it with a solution containing 1000 mg l(-1) As(v) at a soil mass-to-solution ratio of 0.1 kg l(-1). The incorporation of As(v) into the soil and its distribution over the soil phases were monitored by sampling at strategic time intervals using an operationally defined five-step sequential extraction procedure (Wenzel et al., Anal. Chim. Acta, 2001, 436, 309) and subsequent As measurement. A multiple kinetic Langmuir model was developed to retrieve the dynamic parameters (adsorption and desorption rate constants, capacities and Langmuir equilibrium constants) for each of the soil phases by numerical fitting of the experimental adsorption data to the model. Under the equilibration conditions used the adsorption rate constants for all five operationally defined soil phases were very similar but the desorption rate constants decreased by a factor of ca. 150 from soil phase 1 (non-specifically sorbed As) to 5 (residual phases). This implies that As(v) incorporation "deeper" into the soil leads to stronger binding which is associated with the Langmuir equilibrium constants (adsorption rate constants/desorption rate constants). Equilibration of the soil with As(v) was complete in ca. 10 days with As(v) predominantly bound to soil phase 2 (specifically sorbed As) and soil phase 3 (amorphous and poorly crystalline hydrous oxides). X-Ray absorption spectroscopy techniques revealed that these binding characteristics may be related to adsorption of As(v) on Si- and/or Al-containing structures and natural hydrous iron oxide (HFO) surface sites, respectively. Since the model is independent of the initial As(v) concentration in the solution and the soil mass-to-solution ratio, the behaviour of the thus characterized soil-As(v) system can be predicted for a range of conditions. Simulations showed that in an accidental As(v) spill the soil studied would actively scavenge As(v) by instantaneous adsorption onto all soil phases followed by redistribution of As(v) from weaker binding sites to stronger ones over time.     

Fractionation of traffic-emitted Ce, La and Zr in road dusts

The introduction of catalytic converters has led to a new environmental problem since catalysts emit platinum group elements (PGEs) which are among the least distributed elements in nature. Along with PGEs the vehicle exhaust catalysts contain also a number of stabilizers, commonly oxides of rare earth elements and alkaline earth elements such as Ce, La and Zr. Since vehicular emission of these elements has received little attention so far this work attempts to offer insight into their distribution and fate in the environment by measuring their speciation in road dust samples collected along several highways in Germany and a city centre (Saarbrücken). Speciation of the elements (fractionation into associated mineralogical phases) was carried out via a conventional sequential extraction protocol and the complexing abilities of humic substances in the organic matter were investigated by selective extraction methods in combination with size segregation. For evaluation purposes soil samples spiked with catalytic converter material were analyzed, showing a much lower fraction of Ce, La and Zr mobilized in comparison to the road dust samples. It was found that the elements were effectively bound to humic substances in road dust with a preference for complexation with low molecular weight compounds (<1600 Da).     

The seasonal distribution of heavy metals in Mussel sample from Yalova in the Marmara Sea, 2008�C2009

Concentration of the some heavy metals (Co, Cu, Fe, Ni, Pb and Zn) Mediterranean mussel Mytilus galloprovincialis from Yalova (Marmara Sea) were investigated seasonally. The mean concentrations of Co, Cu, Fe, Ni, Pb and Zn in the soft tissues were 4.08 ± 0.67, 5.54 ± 0.59, 156.72 ± 20.18, 3.71 ± 1.14, 2.92 ± 0.51 and 106.23 ± 5.66 mg kg(?-1) dry weights, respectively. There were no significant differences between the metal concentrations among the seasons (P > 0.05). The mean Pb and Zn concentrations were higher than the acceptable limit proposed by International Turkish standards.     

Is maternal alpha-fetoprotein screening still of value in a low-risk area for neural tube defects?

Estimation of maternal serum alpha-fetoprotein (AFP) was used as a screening method for the detection of neural tube defects (NTDs) in 6344 women over three years. Of 88 (1.4 per cent) who had one or more serum AFP levels equal to, or greater than, 2.5 multiples of the median (MoM) for the relevant gestational age, 43 (0.68 per cent) underwent amniocentesis. There were eight NTDs. Four of these were screened by serum AFP, and all cases of spina bifida had serum AFP levels greater than 3.0 MoM, including one small open defect which was not seen on ultrasound. The other four cases of NTD, which were not screened, were identified by ultrasound. Of 64 singleton pregnancies 32 (50 per cent) had serum AFP levels between 2.5 and 3.0 MoM, and low birthweight (⪕2500 g) occurred in 29 per cent. Because of improvements in ultrasound techniques and the apparent falling incidence of NTD, the role of serum AFP as the primary screening procedure should be regularly reviewed. Effective screening is dependent on mothers booking early.     

Prenatal diagnosis of pericentric inversion of chromosome no. 17 in a twin pregnancy

Although prenatal genetic diagnosis can usually provide prospective parents with information as to whether their fetus is affected with certain genetic conditions, the presence of twins and the uncertainty about the phenotype of some chromosome variations pose a major dilemma and make genetic counselling very difficult. Here, a case report of an unusual chromosome aberration (pericentric inversion of chromosome no. 17) in a twin pregnancy which was originally suspected to be monoamniotic but later proved to have two sacs was presented.     

Monitoring perchlorate exposure and thyroid hormone status among raccoons inhabiting a perchlorate-contaminated site

Perchlorate is a water soluble anion that is readily accumulated in vegetation. It inhibits uptake of iodide into thyroid gland tissue, thereby reducing production of thyroid hormones. Potential raccoon food items including berries, fish, and vegetation collected at a contaminated site contained quantifiable concentrations of perchlorate as determined by ion chromatography. Therefore, we monitored resident raccoons for exposure to perchlorate by examining plasma perchlorate and thyroid hormone concentrations. Resulting analytical data failed to demonstrate perchlorate exposure among raccoons that likely consumed food items collected along perchlorate-contaminated water bodies. There were no correlations between triiodothyronine or thyroxine and thyroid stimulating hormone concentrations, but triiodothyronine concentrations in raccoon plasma were significantly higher in 2000 than in 2001 (p = 0.0081). These data suggest that natural attenuation and remedial efforts initiated in January of 2001 may have reduced perchlorate exposure among raccoons inhabiting this site from 2000 to 2001. Temporal, spatial, and analytical factors limited our ability to quantify exposure among raccoons, however, our data do not indicate that raccoons currently inhabiting this site are at risk for significant exposure to perchlorate and subsequent effects.     

Monitoring of Butter and Ghee (Clarified Butter Fat) for Pesticidal Contamination from Cotton Belt of Haryana, India

Butter (45) and ghee (55) samples were collected from rural and urban areas of cotton growing belt of Haryana and analysed for detecting the residues of organochlorine, synthetic pyrethroid and organophosphate insecticides. The estimation was carried out by using multi residue analytical technique employing GC-ECD and GC-NPD systems equipped with capillary columns. Butter samples were comparatively more contaminated (97%) than ghee (94%), showing more contamination with organochlorine insecticides from urban samples. About 11% samples of butter showed endosulfan residues above MRL value and 2% samples had residues of synthetic pyrethroids and organophosphates each above their respective MRL values. In ghee, residues of HCH & DDT both and of endosulfan exceeded the MRL values in 5 and 20% samples, respectively. Among organophosphates, only chlorpyriphos was detected with 9% samples showing its residue above MRL value. Irrespective of contamination levels, residues above the MRL values were more in ghee. More extensive study covering other agricultural regions/zones of Haryana has been suggested to know the overall scenario of contamination of milk products.