Lead in Egyptian soils: Origin, reactivity and bioavailability measured by stable isotope dilution.

The current availability of Pb in Egyptian soils and associated plants were studied in 15 locations (n=159) that had been historically subjected to industrial and automobile Pb emissions. Isotopic dilution with enriched 204Pb was used to estimate the soil Pb labile pool (PbE); results showed that %PbE values were mostly <25% which is likely due to the alkaline nature of the soils. Nonetheless, lability of Pb was significantly higher in urban and industrial locations indicating greater reactivity of anthropogenic Pb in comparison to geogenic-Pb. A plot of 206Pb/207Pb vs 208Pb/207Pb showed that all soils were aligned close to a virtual binary line between two apparent end member signatures (petrol and geogenic-Pb) suggesting that they are the major sources of Pb in the Egyptian environment. Soils with greater Pb concentrations (urban and industrial locations) displayed a significantly greater ratio of labile petrol-Pb to labile geogenic-Pb in comparison to less-contaminated soils. However, this difference was marginal (±5%) suggesting that historically emitted petrol-Pb has substantially mixed with geogenic-Pb into a common pool as a result of prolonged contact with soil. The proportion of petrol-Pb in fruits and leaf vegetables was significantly (P<0.005) greater than that of the associated soils suggesting preferential uptake of the more labile petrol-Pb as opposed to the relatively immobile geogenic-Pb. However, it is also possible that the major source of Pb intake by Egyptian consumers is extraneous Pb dust enriched with petrol Pb rather than systematic Pb via roots uptake.

Evaluating the mobility of polymer-stabilised zero-valent iron nanoparticles and their potential to co-transport contaminants in intact soil cores.

The use of zero-valent iron nanoparticles (nZVI) has been advocated for the remediation of both soils and groundwater. A key parameter affecting nZVI remediation efficacy is the mobility of the particles as this influences the reaction zone where remediation can occur. However, by engineering nZVI particles with increased stability and mobility we may also inadvertently facilitate nZVI-mediated contaminant transport away from the zone of treatment. Previous nZVI mobility studies have often been limited to model systems as the presence of background Fe makes detection and tracking of nZVI in real systems difficult. We overcame this problem by synthesising Fe-59 radiolabelled nZVI. This enabled us to detect and quantify the leaching of nZVI-derived Fe-59 in intact soil cores, including a soil contaminated by Chromated-Copper-Arsenate. Mobility of a commercially available nZVI was also tested. The results showed limited mobility of both nanomaterials; <1% of the injected mass was eluted from the columns and most of the radiolabelled nZVI remained in the surface soil layers (the primary treatment zone in this contaminated soil). Nevertheless, the observed breakthrough of contaminants and nZVI occurred simultaneously, indicating that although the quantity transported was low in this case, nZVI does have the potential to co-transport contaminants. These results show that direct injection of nZVI into the surface layers of contaminated soils may be a viable remediation option for soils such as this one, in which the mobility of nZVI below the injection/remediation zone was very limited. This Fe-59 experimental approach can be further extended to test nZVI transport in a wider range of contaminated soil types and textures and using different application methods and rates. The resulting database could then be used to develop and validate modelling of nZVI-facilitated contaminant transport on an individual soil basis suitable for site specific risk assessment prior to nZVI remediation.

Zinc solubility and fractionation in cultivated calcareous soils irrigated with wastewater.

The solubility, lability and fractionation of zinc in a range of calcareous soils from Peshawar, Pakistan were studied (18 topsoils and 18 subsoils). The lability (E-value) of Zn was assessed as the fraction isotopically exchangeable with (70)Zn(2+); comparative extractions included 0.005 M DTPA, 0.43 M HNO3 and a Tessier-style sequential extraction procedure (SEP). Because of the extremely low concentration of labile Zn the E-value was determined in soils suspended in 0.0001 M Na2-EDTA which provided reliable analytical conditions in which approximately 20% of the labile Zn was dissolved. On average, only 2.4% of soil Zn was isotopically exchangeable. This corresponded closely to Zn solubilised by extraction with 0.005 DTPA and by the carbonate extraction step (F1+F2) of the Tessier-style SEP. Crucially, although the majority of the soil CaCO3 was dissolved in F2 of the SEP, the DTPA dissolved only a very small proportion of the soil CaCO3. This suggests a superficial carbonate-bound form of labile Zn, accessible to extraction with DTPA and to isotopic exchange. Zinc solubility from soil suspended in 0.01 M Ca(NO3)2 (PCO2 controlled at 0.03) was measured over three days. Following solution speciation using WHAM(VII) two simple solubility models were parameterised: a pH dependent 'adsorption' model based on the labile (isotopically exchangeable) Zn distribution coefficient (Kd) and an apparent solubility product (Ks) for ZnCO3. The distribution coefficient showed no pH-dependence and the solubility model provided the best fit to the free ion activity (Zn(2+)) data, although the apparent value of log10 Ks (5.1) was 2.8 log units lower than that of the mineral smithsonite (ZnCO3).

Soil-plant interactions and the uptake of Pb at abandoned mining sites in the Rookhope catchment of the N. Pennines, UK--a Pb isotope study.

This paper examines Pb concentrations and sources in soil, grass and heather from the Rookhope catchment in the North Pennines, UK, an area of historical Pb and Zn mining and smelting. Currently, the area has extensive livestock and sports shooting industries. Risk assessment, using the source-pathway-receptor paradigm, requires the quantification of source terms and an understanding of the many factors determining the concentration of Pb in plants. A paired soil and vegetation (grass and heather) geochemical survey was undertaken. Results showed no direct correlation between soil (total or EDTA extractable Pb) and vegetation Pb concentration. However, regression modelling based on the Free-Ion Activity Model (FIAM) suggested that the underlying mechanism determining grass Pb concentration across the catchment was largely through root uptake. Spatial patterns of (206/207)Pb isotopes suggested greater aerosol deposition of Pb on high moorland and prevailing wind facing slopes. This was evident in the isotopic ratios of the heather plants. Pb isotope analysis showed that new growth heather tips typically had (206/207)Pb values of ~1.14, whilst grass shoots typically had values ~1.16 and bulk soil and peat ~1.18. However, the (206/207)Pb ratio in the top few cm of peat was ~1.16 suggesting that grass was accessing Pb from a historical/recent pool of Pb in soil/peat profiles and consisting of both Pennine ore Pb and long-range Pb deposition. Isotope Dilution assays on the peat showed a lability of between 40 and 60%. A simple source apportionment model applied to samples where the isotope ratios was not within the range of the local Pennine Pb, suggested that grass samples contained up to 31% of non-Pennine Pb. This suggests that the historical/recent reservoir of non-Pennine Pb accessed by roots continues to be a persistent contaminant source despite the principal petrol Pb source being phased out over a decade ago.

Fistula advancement operation in the treatment of selected cases of persistently recurrent urethrocutaneous fistula following distal penile hypospadias repair.

BACKGROUND: Hypospadias fistula may be a persistently recurrent problem in some cases. The present paper describes a urethral mobilization procedure as a new way to solve this problem. METHODS: The procedure was performed on seven children suffering from recurrent hypospadias fistula that had failed more than once to be repaired by the classic ways of closure. Selection of suitable cases should be done intra-operatively, when urethral mobilization has successfully allowed the fistula opening to easily reach the glans top. The described procedure is an extensive urethral mobilization that advances the fistula opening to the neomeatus at the glans top through a glanular tunnel. RESULTS: The operation resulted in a straight penis with the neomeatus at the glans top in all seven children, without complications, over a period of 6-18 months follow up. CONCLUSIONS: The fistula advancement operation, as it is called by the author, can, in selected cases, solve the problem of persistently recurrent hypospadias fistula with a high success rate. Thus, the author recommends that this technique is added to urologists' armamentarium.

Double purpose penile skin flap one-stage urethroplasty for repair of distal penile hypospadias cripples.

A new one-stage urethroplasty operation is presented. The author called it "double purpose penile skin flap technique". It is recommended for the substitution of distal urethral defect when its length is equal to or less than half the circumference of the penile shaft in cases following multiple failed hypospadias repairs.

Implantation of beads into the penile skin and its complications.

Embedding of beads into the penile skin was observed among 60 foreign workers in the employ of certain Saudi Arabian companies. The procedure had been performed by an unqualified person. They had undergone this procedure in order to increase sexual stimulation of the mate. Infection secondary to implantation procedure had occurred in only 2 cases, necessitating surgical treatment. The first patient was suffering from a penile abscess (one week) after embedding of an ivory bead. The second one was troubled by a painful erection (3 months) after embedding of three glass beads. The other 58 persons had had their implanted beads for varying periods of time, ranging from 3 months to 8 years, without complaint. They refused to have the beads removed. This abnormal procedure is considered to be a manifestation of a suppressed psycho-sexual neurosis.

Spontaneous localized lipogranuloma of the spermatic cord.

Four cases of localized lipogranuloma of the spermatic cord without evident predisposing factor, are presented. The mass was associated with a small vaginal hydrocele. Wide excision of the intact mass proved successful in all cases. There was no recurrence or regrowth up to one-year follow up. At histology a lipogranuloma was diagnosed but its cause could not be assessed. A spontaneous specific tissue reaction of the cord tunics to an unknown injury, is hypothesized.

Simple procedure to repair distal penile hypospadias without chordee in adult males.

Penile, glanular and preputial flaps repair was done in 7 adult male patients with distal penile hypospadias without chordee. They suffered from psychological problems because of the abnormal shape of their penis. The procedure consisted in a simplified perimeatal-based flap technique with special attention given to the incision and suturing of the flaps. The operation resulted into a normally looking penis through the creation of a wide neourethra starting with a meatus at the apex of the glans and covered by a pliable elastic hair-less skin. This procedure is rapid, simple and needs a short hospitalization period without urinary diversion. It proved satisfactory for adults with distal penile hypospadias without chordee, resulting in a long penis, flat glans with pliable skin and well developed dorsal hooded foreskin. The procedure should be performed when the meatus is at a distance not suitable for meatoplasty and glanuloplasty or other techniques. It is recommended to correct the shape of the penis of any hypospadiac during childhood to prevent psychosexual neuroses in adulthood.