Case study: heavy metals and fluoride contents in the materials of Syrian phosphate industry and in the vicinity of phosphogypsum piles.

This study focuses on the determination of heavy metals and fluoride concentrations in the Syrian phosphate industry and in the vicinity of the phosphogypsum (PG) piles. Four sampling campaigns were carried out, in which 86 soil, 139 plant, 30 air particulate, 16 water, 12 PG, 6 phosphate ore (raw and treated) and 3 fertilizer samples were collected. Differential pulse anode stripping voltammetry was used for Pb and Cd determination, atomic absorption spectrometry was used for Zn, Cr and Cu determination, and instrumental neutron activation analysis was used for Se, Ni, As and Hg determination. Fluoride concentration was determined via fluoride ion selective electrode. The data revealed that most of the heavy metals were retained in the fertilizer. Fluoride content in PG was 0.47%. The presence of PG piles showed no impact on the run-off and ground and lake waters in the area. However, fluoride concentration was double the permissible airborne threshold in the sites to the east of the PG piles because of the prevailing wind in the region. Similarly, enhanced concentrations of fluoride were recorded for the eastern soil samples. The content of heavy metals in plants was element- and plant-specific and influenced by the element concentration in soil, the soil texture and the pH. The maximal mean of fluoride was found in the plants species of the eastern sites (699 mg kg(-1)), which mainly related to PG erosion and airborne deposition. Thus, the main impact of the PG piles was to increase the concentration of fluoride in the surrounding area. A national action should be taken to regulate PG piles.

Sorption of 226Ra from waste effluents using Syrian bentonite.

In view of environmental concern, sorption of radium on natural bentonite mineral (Aleppo, Syria) was investigated using a batch-type method. Data were expressed in terms of distribution coefficients. An attempt to increase the selectivity of bentonite for radium was made by preparing M-derivatives. Loss of mineral crystallinity in acidic media and the formation of a new phase, such as BaCO3, in Ba-derivative were evidenced by XRD characterizations. Of the cationic forms, Na-bentonite showed the highest affinity. Mechanisms of radium uptake were studied using M-derivatives and simulated radium solutions. The obtained results indicated that surface sorption/surface ion exchange were the predominant processes. The distinct sorption behaviour observed with the Ba-form was, possibly, a reflection of radium coprecipitation with barium carbonate. The competing order of macro components, likely present in waste streams, was investigated by studying different concentrations of the corresponding salt media. Sodium was found to be the weakest inhibitor. The performance of natural bentonite and the most selective forms, i.e. Ba- and Na-derivatives, to sorb radium from actual oil co-produced waters, collected form Der Ezzor Petroleum Company (DEZPC), was studied. This showed the influential effect ofpH compared with other parameters.

Hormonal and cellular regulation of Sertoli cell anti-Müllerian hormone production in the postnatal mouse.

Anti-Müllerian hormone (AMH) is secreted by immature testicular Sertoli cells. Clinical studies have demonstrated a negative correlation between serum AMH and testosterone in puberty but not in the neonatal period. We investigated AMH regulation using mouse models mimicking physiopathological situations observed in humans. In normal mice, intratesticular, not serum, testosterone repressed AMH synthesis, explaining why AMH is downregulated in early puberty when serum testosterone is still low. In neonatal mice, AMH was not inhibited by intratesticular testosterone, due to the lack of expression of the androgen receptor in Sertoli cells. We had shown previously that androgen-insensitive patients exhibit elevated AMH in coincidence with gonadotropin activation. In immature normal and in androgen-insensitive Tfm mice, follicle stimulating hormone (FSH) administration resulted in elevation of AMH levels, indicating that AMH secretion is stimulated by FSH in the absence of the negative effect of androgens. The role of meiosis on AMH expression was investigated in Tfm and in pubertal XXSxrb mice, in which germ cells degenerate before meiosis. We show that meiotic entry acts in synergy with androgens to inhibit AMH. We conclude that AMH represents a useful marker of androgen and FSH action within the testis, as well as of the onset of meiosis.

Testicular dysgenesis does not affect expression of anti-müllerian hormone by Sertoli cells in premeiotic seminiferous tubules.

Anti-Müllerian hormone (AMH) immunoreactivity was studied on paraffin sections obtained from archival testicular biopsies of 29 children with intersex disorders and of 22 controls. Strong AMH immunoreactivity was observed in Sertoli cell cytoplasm from 8 fetal weeks until puberty. During pubertal maturation, in both normal and intersex patients, AMH expression was present in premeiotic seminiferous tubules, but was no longer detected in neighboring tubules with meiotic development. AMH immunostaining was abolished in the testis of one patient with persistent Müllerian ducts due to a mutation of the AMH gene, but was conserved in the testes of two patients with mutations of the AMH receptor gene. Testicular dysgenesis usually results in sexual ambiguity, with low testosterone and AMH serum levels and persistence of Müllerian derivatives. AMH immunoreactivity was conserved in premeiotic seminiferous tubules of dysgenetic testes, and also in sex-cord cells of a gonadoblastoma. In patients with asymmetric gonadal differentiation, the streak gonad was AMH-negative. In conclusion, secretion of AMH is a constitutive feature of the immature Sertoli cell and its expression is altered only by mutations of the AMH gene, but not by gonadal dysgenesis. The degree of regression of Müllerian ducts and serum AMH levels reflect the number, not the functional value, of Sertoli cells present in the immature testis.