An assessment of mercury loading in core sediments of Sunderban mangrove wetland, India (a preliminary report).

This is a preliminary report on total mercury (T(Hg)) in core sediments (<63 microm particle size) of Sunderban mangrove wetland, northeastern part of the Bay of Bengal, India. Cold vapor atomic absorption spectrometry (CVAAS) was used for T(Hg) determination. The concentration varies from 9.8 to 535.1 ppb (ngg(-1)). Results revealed variations over premonsoon and postmonsoon month at different core depth, as well as in studied three sampling stations, located at the site of three rivers: Hugli River (S(1)), Matla River (S(2)) and Bidyadhari River (S(3)). Elevated concentration of T(Hg) in subsurface layer (4-8 cm) of the core at S(2) is attributed to remobilization of mercury from deeper sediment (32-36 cm). Positive correlation is present between total Hg and clay content. Based on index of geoaccumulation (I(geo)) and Effects-Range Low (ER-L) value (150 ppb) it is considered that the sediments are till now unpolluted. As a consequence, there is less chance of ecotoxicological risk to organisms living in studied sediments. Two statistical methods were applied to determine T(Hg) anomalies. Box plot method showed one extreme and three outliers in S(1) at postmonsoon season. Two extremes were found at S(2) at 4-8 and at 32-36 cm in premonsoon period. In S(3) there was no anomaly by box plot method. MAD method was more sensitive than box plot method and T(Hg) anomaly was detected at 12-16 cm in S(3) during postmonsoon season. The data reported are useful baselines for T(Hg) in Sunderban mangrove wetland, India and would be of help in future sediment quality studies.

Multidisciplinary work on barium contamination of the karstic upper Kupa River drainage basin (Croatia and Slovenia); calling for watershed management.

The present work was designed as an extension of a previous study of a barium anomaly observed in stream sediments of the Kupa River. In its upper part the Kupa River drains a region underlain by a trans-boundary aquifer. The river is a significant water resource in a region of tourism, sport, and fishing in both Croatia and Slovenia. The contamination source is situated in Homer (Lokve), Croatia, where barite was mined until 10 years ago. The barium processing waste material (<3-mm fraction) was carelessly deposited in gardens, forests, and into a sinkhole, which has an underground link with the Kupica River, a tributary of the Kupa River. Barium waste and stream sediments were analyzed using comparative techniques: X-ray diffraction (XRD), X-ray fluorescence (XRF), Mössbauer spectroscopy, and grain size analysis. XRD of the waste material identified the major minerals quartz, barite, and dolomite and the Fe-containing minor minerals muscovite and goethite. Barite was identified as a minor or trace mineral in the Kupica River sediments. XRF analysis of the waste material has shown Ba and Fe to be the predominant elements, Ca and K to be minor elements, and Mn, Zn, Sr, Pb, Co, Cu, As, Zr, Rb, Y, and Mo to be trace elements. Mössbauer spectroscopy performed at room temperature (RT) was used to study iron minerals, particularly to obtain information on the valence status of Fe ions. Grain size analysis of the waste material (<63-microm fraction) has shown that it contains 23.5% clay-size material in comparison with 7-8% clay-size material in stream sediments. It is our aim to combine geochemical and medical methods to investigate the possible impact of waste disposal on human health in Lokve. At this stage of the work, concentrations of Ba and other toxic elements in the water compartment of the Kupica River (a source of drinking water) have not been monitored by Croatian Waters (name of the Croatian water authorities). The necessity of such measurements in future studies has been highlighted. A preliminary study of diseases diagnosed in Lokve shows that about 18% of the total inhabitants have serious medical problems. Diseases of the circulatory system, endocrine, nutritional, and metabolic diseases, neoplasms, and respiratory diseases predominate. This paper calls for further multidisciplinary research on the health effects of barium and trace elements, as well as for bioremediation of contaminated gardens and for watershed management of vulnerable karstic aquifers.

Paramagnetic molecular centers in gamma-irradiated aluminum hydroxide complexed with glycine or serine.

Paramagnetic molecular centers produced by gamma irradiation at 77 K and at 293 K in Alx(OH)y, when precipitated with glycine or serine, were studied by ESR spectroscopy. Stable paramagnetic centers characteristic for the amino acid were observed only in the complexes with DL-alpha-serine, and only in air. In the absence of air, at 293 K, none of the paramagnetic centers gave ESR spectra characteristic of the amino acids examined. Irradiation at 77 K produced the glycine radical, .CH2COOH, only in the complex prepared at pH 6.8 and not in the complex prepared at pH 9.5. The radical decayed when the sample was warmed. In the serine complexes, at 77 K the radicals characteristic of the amino acid were not observed. Differences in the behavior between glycine and serine in the complexes prepared under similar conditions are probably due to the serine OH group available for hydrogen bonding in the matrix.

Precipitation and characterization of an aluminosilicate from AlCl3-Na2SiO3-HCl in serum, of interest for Alzheimer disease.

A precipitation experiment was performed with human serum to model aluminosilicate formation in brains of patients with Alzheimer disease. Aluminum and (or) silicate ions were added to serum in a 1:2 molar ratio at pH 7.4. Precipitates formed immediately and were left for 24 h at 37 degrees C before filtration. Silicate and aluminosilicate formed precipitates with human serum proteins albumin, transferrin, and IgG. In untreated samples, the IgG/albumin ratio increased slightly compared with the ratio in dried serum. Diethylbarbiturate-washed precipitates had a significantly lower protein content than did untreated ones. The IgG/albumin ratio increased considerably in the sample containing aluminosilicate. We conclude that IgG is the sodium dodecyl sulfate-soluble human protein most firmly bound to the aluminosilicate matrix. From 27Al magic-angle-spinning nuclear magnetic resonance (MAS NMR), a pronounced peak was found at 52.79 ppm and a minor peak at 0.53 ppm, suggesting that 4-coordinated aluminum predominates and that 6-coordinated aluminum is present in a smaller proportion. The 29Si MAS NMR spectrum shows a poorly ordered structure. The aluminosilicate formed also contains the cations Na+ > K+ > Ca2+ > Mg2+ and anions Cl- > PO4(3-). Rather than looking for aluminum toxicity to explain the effects of Alzheimer disease, one should consider that by precipitating such a composite phase, the balance of cations, anions, and proteins in human serum is changing.

Paramagnetic molecular centers in gamma-irradiated precipitates in the system AlCl3-DL-alpha-valine-NaOH.

Formation and stability of paramagnetic molecular centers were studied in AlCl3-NaOH-DL-alpha-valine by ESR spectroscopy. In Al3(OH)9(valine)1 x 3H2O gamma-irradiated at room temperature the valine radical [formula: see text] was detected. The radical was formed by abstraction of a hydrogen atom from the valine molecule coupled to the aluminum hydroxide matrix. Stability of the radical depended critically on structural properties of the aluminum hydroxide matrix. In aluminum hydroxide with the ratio (Al)/(Valine) = 20, either no paramagnetic species were detected (irradiation in air) or a singlet at g = 2.008 of 1.8 mT linewidth was detected (irradiation in vacuum) at room temperature. Primary paramagnetic species (gamma irradiation at 77 K) in Al3(OH)9(Val)1 x 3H2O are chloride paramagnetic centers and the primary neutral valine radical [formula: see text] It was formed by abstraction of the NH2 group from the valine molecule. With warming, this radical was not transformed to the radical (I).

Aspartic acid as a trap for gamma-radiation energy in the amorphous Al5(OH)15(Asp)3.3H2O.

Paramagnetic molecular centers produced by gamma irradiation at 77 K and at room temperature in the novel compound Al5(OH)15(Asp)3.3H2O were studied by ESR spectroscopy. The g value of 2.0034 and the lack of such lines in pure aluminum hydroxide suggested that all the paramagnetic centers observed are related to the aspartic acid molecule. However, none of the paramagnetic centers gave an ESR spectrum characteristic for gamma-irradiated pure aspartic acid powder. The influence of the oxygen on the formation of the paramagnetic centers was noticed. The extreme stability of the paramagnetic molecular centers formed in Al5(OH)15(Asp)3.3H2O suggests that aspartic acid complexed in aluminum hydroxide is a good trap for gamma-radiation energy.

Oxalate molecule as the trap for gamma-irradiation energy in the amorphous aluminosilicate Al2(OH)6H4SiO4.

Paramagnetic species which were the products of gamma irradiation at 77 K and at room temperature were studied by ESR spectroscopy in the amorphous aluminosilicate, Al2(OH)6H4SiO4, prepared in the presence and in the absence of oxalate ion. The aluminosilicate precipitated from the solution containing the oxalate ion in 10(-4) mol dm-3 concentration contained the oxalate only in trace amounts. When gamma-irradiated at 77 K and at room temperature, this compound gave the stable paramagnetic species represented by the single ESR line centered at g = 2.000. We ascribe this spectrum to the CO2- radical formed from the oxalate ion. The same aluminosilicate prepared in the absence of the oxalate either produced no stable paramagnetic product after gamma irradiation at room temperature or resulted in composite ESR spectra, indicating the presence of several paramagnetic species if irradiated at 77 K. Complex ESR spectra were transformed by heating to the stable paramagnetic centers which differed from the one obtained from oxalate ion. We conclude that in Al2(OH)6H4SiO4 oxalate acts as a trap for the gamma-radiation energy.