A safer disposal of hazardous phosphate coating sludge by formation of an amorphous calcium phosphate matrix.

Phosphate coating hazardous wastes originated from the automotive industry were efficiently encapsulated by an acid-base reaction between phosphates present in the sludge and calcium aluminate cement, yielding very inert and stable monolithic blocks of amorphous calcium phosphate (ACP). Two different compositions of industrial sludge were characterized and loaded in ratios ranging from 10 to 50 wt.%. Setting times and compressive strengths were recorded to establish the feasibility of this method to achieve a good handling and a safe landfilling of these samples. Short solidification periods were found and leaching tests showed an excellent retention for toxic metals (Zn, Ni, Cu, Cr and Mn) and for organic matter. Retentions over 99.9% for Zn and Mn were observed even for loadings as high as 50 wt.% of the wastes. The formation of ACP phase of low porosity and high stability accounted for the effective immobilization of the hazardous components of the wastes.

Treatment of toxic metal aqueous solutions: encapsulation in a phosphate-calcium aluminate matrix.

Polyphosphate-modified calcium aluminate cement matrices were prepared by using aqueous solutions polluted with toxic metals as mixing water to obtain waste-containing solid blocks with improved management and disposal. Synthetically contaminated waters containing either Pb or Cu or Zn were incorporated into phosphoaluminate cement mortars and the effects of the metal's presence on setting time and mechanical performance were assessed. Sorption and leaching tests were also executed and both retention and release patterns were investigated. For all three metals, high uptake capacities as well as percentages of retention larger than 99.9% were measured. Both Pb and Cu were seen to be largely compatible with this cementitious matrix, rendering the obtained blocks suitable for landfilling or for building purposes. However, Zn spoilt the compressive strength values because of its reaction with hydrogen phosphate anions, hindering the development of the binding matrix.

Solidification/stabilization of toxic metals in calcium aluminate cement matrices.

The ability of calcium aluminate cement (CAC) to encapsulate toxic metals (Pb, Zn and Cu) was assessed under two curing conditions. Changes in the consistency and in the setting time were found upon the addition of the nitrates of the target metals. Both Pb and Cu caused a delay in CAC hydration, while Zn accelerated the stiffening of the mortar. Compressive strengths of the metal-doped mortars, when initially cured at 60 °C/100% RH, were comparable with that of the free-metal mortar. Three different pore size distribution patterns were identified and related to the compounds identified by XRD and SEM. Sorbent capacities of CAC for the toxic metals were excellent: a total uptake was achieved for up to 3 wt.% loading of the three metals. In this way, CAC mortars were perfectly able to encapsulate the toxic metals, allowing the use of CAC for waste management as proved by the leaching tests.

Encapsulation, solid-phases identification and leaching of toxic metals in cement systems modified by natural biodegradable polymers.

Cement mortars loaded with Cr, Pb and Zn were modified by polymeric admixtures [chitosans with low (LMWCH), medium (MMWCH) and high (HMWCH) molecular weight and hydroxypropylchitosan (HPCH)]. The influence of the simultaneous presence of the heavy metal and the polymeric additive on the fresh properties (consistency, water retention and setting time) and on the compressive strength of the mortars was assessed. Leaching patterns as well as properties of the cement mortars were related to the heavy metals-bearing solid phases. Chitosan admixtures lessened the effect of the addition of Cr and Pb on the setting time. In all instances, chitosans improved the compressive strength of the Zn-bearing mortars yielding values as high as 15 N mm(-2). A newly reported Zn phase, dietrichite (ZnAl(2)(SO(4))(4)·22H(2)O) was identified under the presence of LMWCH: it was responsible for an improvement by 24% in Zn retention. Lead-bearing silicates, such as plumalsite (Pb(4)Al(2)(SiO(3))(7)), were also identified by XRD confirming that Pb was mainly retained as a part of the silicate network after Ca ion exchange. Also, the presence of polymer induced the appearance and stabilization of some Pb(IV) species. Finally, diverse chromate species were identified and related to the larger leaching values of Cr(VI).

Interaction of carboxymethylchitosan and heavy metals in cement media.

The performance of an etherified chitosan, carboxymethylchitosan (CMCH), when added to cement mortars doped with heavy metals, was assessed. In the presence of heavy metals (Cr, Pb, Zn) strong modifications of the fresh-state properties were evaluated. The addition of the polymer was seen to be useful in minimising some of these modifications, as those related to the setting time. A competitive mechanism for adsorption between the oxoanionic form of the metals and the carboxylate groups of the chitosan derivative was established. Studies on the metal chelating ability of the polymer and leaching from the hardened specimens showed scarce complexation under alkaline conditions, pointing to physical entrapment based on metal adsorption. However, significant chelation of metals was proved at near-neutral pH, suggesting the potential usefulness of the polymer as an agent for removing heavy metals from polluted waters and subsequently immobilizing them in cement mortars. Leaching tests carried out on polymer-metal complex-bearing samples showed a reduction in the amount of released Pb and Zn.

Selenium intake reduces serum C3, an early marker of metabolic syndrome manifestations, in healthy young adults.

OBJECTIVES: To evaluate the associations between serum complement factor 3 (C3) and several anthropometrical, biochemical and lifestyle features in healthy young adults, emphasizing on the putative effect of selenium intake on C3 concentrations. METHODS: This study enrolled 100 healthy young adults aged 18-34 years. Anthropometric and blood pressure measurements and lifestyle features were analyzed. Fasting blood samples were collected for the measurement of glucose, total cholesterol, HDL-cholesterol, LDL-cholesterol, triacylglycerols and C3 concentrations. Nail samples were collected for the analysis of selenium concentrations. RESULTS: Values of BMI (P=0.034), sum of skinfold thicknesses (STs) (P=0.021), body fat mass (BFM) (P=0.023), percentage of overweight subjects (P=0.007), serum triacylglycerols (P=0.012) and nail selenium (P=0.001) were significantly different between subjects above and below the median of serum C3 concentrations. The following correlations with serum C3 were identified tricipital ST (P=0.033), sum of STs (P=0.012), BMI (P=0.008), BFM (P=0.018), waist-to-height ratio (P=0.016), serum glucose (P=0.045), serum triacylglycerols (P=0.001) and nail selenium (P=0.006). Circulating C3 showed a positive association with several adiposity markers such as BMI (P=0.001), waist circumference (P=0.006), waist-to-height ratio (P=0.002), BFM (P=0.025), as well as serum glucose (P=0.027) and triacylglycerols (P<0.001), whereas nail selenium was a statistically significant negative predictor of C3 concentrations (P=0.018). CONCLUSIONS: C3 seems to be related with selenium status and several anthropometrical and biochemical measurements linked to metabolic syndrome in apparently healthy young adults. These findings suggest a possible role for selenium intake in the modulation of C3, whose assessment may be an early marker of metabolic syndrome manifestations.

Lead levels in retail samples of Spanish infant formulae and their contribution to dietary intake of infants.

Lead concentrations in 82 different types of infant formulae (cow's milk and soy based) marked in Spain were analysed by acid-microwave decomposition and anodic stripping voltammetry. Dietary lead intake from infant formula and tap water used for powder formula reconstitution were estimated in comparison with the provisional tolerable weekly intake (PTWI). Additionally, the influence of physical state (powder and ready-to-use formulae), the type of container used and the impact of the industrial process from different manufacturers on lead levels were evaluated. According to the results, lead exposure from drinking water was negligible with respect to formulae investigated; where soya formulae contributed the highest intake (58-73% PTWI), non-adapted starter and specialized formulae gave an moderate intake (31-42 and 26-37% PTWI, respectively), and, finally, pre-term, adapted starter and follow-up formulae provided the lowest lead intake (22-25, 22-26 and 16-22% PTWI, respectively). Based on the current state of knowledge about lead toxicity, manufacturers are called to make an additional effort in order to keep a maximum lead level at 20 microg l-1 for all infant formulae, although it is recommendable that these formulations supply the upper limit (5 microg l-1) of 'normal' human milk.

Aluminium content of Spanish infant formula.

Levels of aluminium in 82 different infant formulae from nine different manufacturers in Spain were determined by acid-microwave digestion and graphite furnace atomic absorption spectrophotometry. The influence of aluminium content in tap water in reconstituted powder formulae was examined and an estimate was made of the theoretical toxic aluminium intake in comparison with the provisional tolerable weekly intake (PTWI). Possible interactions between aluminium and certain essential trace elements added to infant formulations have been studied according to the type or main protein-based infant formula. In general, the infant formulae contained a higher aluminium content than that found in human milk, especially in the case of soya, preterm or hydrolysed casein-based formulae. Standard formulae gave lower aluminium intakes amounting to about 4% PTWI. Specialized and preterm formulae resulted in a moderate intake (11-12 and 8-10% PTWI, respectively) and soya formulae contributed the highest intake (15% PTWI). Aluminium exposure from drinking water used for powder formula reconstitution was not considered a potential risk. In accordance with the present state of knowledge about aluminium toxicity, it seems prudent to call for continued efforts to standardize routine quality control and reduce aluminium levels in infant formula as well as to keep the aluminium concentration under 300 microg l(-1) for all infant formulae, most specifically those formulae for premature and low birth neonates.

Cardiovascular risk factors in relation to the serum concentrations of copper and zinc: epidemiological study on children and adolescents in the Spanish province of Navarra.

This investigation was carried out to show the possible association between groups of children with extreme values of copper and zinc concentrations and cardiovascular risk indicators. Serum copper and zinc concentrations were analysed in a group of 3887 children from Navarra, Spain (both sexes. aged 4-17 years). Hypertension, unfavourable serum lipid profile (total cholesterol, high density lipoprotein cholesterol, low density lipoprotein cholesterol, triglycerides, and cholesterol/HDL and LDL/HDL ratios), and degree of adiposity (weight, height, subcutaneous skinfolds, Quetelet's index and mean of subcutaneous skinfolds) were evaluated. Positive correlation was found between several lipid parameters and copper and zinc concentrations, i.e. degree of correlation related with age, except for copper/HDL and triglycerides/zinc ratios, where correlation remained negative at all points. Copper levels were correlated with adiposity parameters in an age-dependent fashion (Quetelet's index: r = 0.01 for ages 4-7 years to r = 0.10, p < 0.01 for ages 14-17 years; mean skinfold thickness: r = 0.05 for ages 4-7 years up to r = 0.18, p < 0.01 for ages 14-17 years). Most correlations between lipid parameters and copper and zinc are markedly amplified if adiposity parameters are taken into account. However, the only significant association was the established relation between high copper concentrations (> x + 2SD) and unfavourable serum lipid profile (LDL/HDL > 2.2).