Influence of thermal hydrolysis treatment on chemical speciation and bioleaching behavior of heavy metals in the sewage sludge

In this study, the transformation of chemical speciation of Cr, Mn, As and Cd in the sewage sludge before and after thermal hydrolysis treatment was investigated using modified BCR method. The effect of thermal hydrolysis treatment and chemical speciation change on the subsequent bioleaching behavior was also researched. The results showed that the concentrations of Cr, Mn, As and Cd in oxidizable fraction decreased in the sludge treated by thermal hydrolysis. Meanwhile, the proportions of Cr, Mn and As in the mobile fractions (acid-soluble/exchangeable and reducible fraction) all decreased, while Cd was concentrated in the sludge treated by thermal hydrolysis. The final pH value of bioleached sludge treated by thermal hydrolysis was lower than that in the bioleached raw sewage sludge. And faster increase of oxidation-reduction potential (ORP) was also found in the bioleaching process of the sludge treated by thermal hydrolysis. The removal percentage of Mn and Cd increased in the bioleached sludge treated by thermal hydrolysis. Thermal hydrolysis treatment can promote the bioleaching to some extent. Furthermore, the environmental risk of Cr, Mn, As and Cd in the bioleached sludge treated by thermal hydrolysis was all alleviated according to risk assessment analysis compared with the bioleached raw sewage sludge.

Geochemical Explorations of Leached Fe in Tiga Warna Beach, Indonesia

To explore Fe minerals in Tiga Warna Beach, we investigated to assess the geochemical fraction of Fe in sediment. The samples were leached of Fe using the optimized BCR microwave method. The optimized of BCR microwave method revealed the high accuracy and precision before Fe assessment. The leached of Fe in each of fraction in sediment were measured by AAS. The same patterns of explored Fe in the geochemical fractions from the sediment fraction 1 (mobile fraction) to fraction 3 (oxidizable fraction) as stated nonresistant sediment fractions showed a lower portion of Fe compared with the Fe levels in sediment fraction 4 (residual fraction) or resistant sediment fraction. The Pollution Load Index (PLI) value and the geoaccumulation Index (I-geo) value of sediment samples in blue, green, and red waters indicating that the sediments of Tiga Warna Beach are still natural and has not been categorized as polluted.

Chemical Speciation of Heavy Metals and Trace Element in Urban Street Dusts of Beijing, China

Sequential extraction was used to characteristic the heavy metals (Cd, Cr, Zn, Cu, Ni and Pb) and trace element (As) studied in these urban dusts. The ratio of the average total content (F1+F2+F3+F4+R) to the corresponding background value of Beijing soil decreased in the order of Cd>Pb>Cu>Zn>Ni>Cr>As. For fraction distribution, residual form predominated among for Zn, Ni, Cr and Pb. Oxidizable fraction was the leading fraction for Cd and Cu and was the second dominated fraction for Zn and Ni. The results of Risk assessment code (RAC) showed the medium environmental risk of Cd was found in Dongcheng and East 4thRing districts, while a high environmental risk for Cr was present in Xizhimen and Yongdingmen areas.

Chemical Speciation of Mg, K, Ca and Na in Soils

The chemical speciation of metal (Mg, K, Ca and Na) in agricultural and non-agricultural soils was investigated in upstream of the Pearl River, China. The result showed that the four metals speciation distributions of the agricultural soils were similar to those of the non-agricultural soils. Mg were dominated by the residual fraction, the order of Mg in each fraction was residual fraction > weak acid soluble fraction reducible fraction > oxidizable fraction. The distribution patterns of Na and K were similar, in most of the samples, the orders of Na and K in each fraction were residual fraction > weak acid soluble fraction > oxidizable fraction > reducible fraction. The order of Ca in each fraction was weak acid soluble fraction > reducible fraction > oxidizable fraction residual fraction. The bioavailability of Ca in the area was very high in both agricultural and non-agricultural soils.

Oxidizable fraction of organic carbon in an Argisol under different land use systems

The objective of this study was to evaluate carbon input in labile and stable fractions in an ARGISOL of northwestern Brazil under different land use systems. Use systems being evaluated include: forest - MA (reference), agrosilvopasture - TCP (teak, cocoa and pasture); agroforest - TC (teak and cocoa); teak forest at 8 and 5 years - T8 and T5, and pasture - PA. In each system three furrows were made at depths of 0-5 cm, 5-10 cm and 10-20 cm. An area consisting of native vegetation (forest) adjacent to the experiment was sampled and used as control treatment. The use systems MA, T8 and T5 had higher levels of total organic carbon (COT) and the MA system had higher levels of labile carbon (CL) than the other systems, with the exception of TC at a depth of 10-20 cm. In the MA system, COT levels were higher in comparison to use systems TCP, TC and PA while CL levels were higher than the levels observed in use systems TCP and TC. In most cases being analyzed, CL levels were lower than COT levels, therefore this trait can be used as an indicator to assess anthropogenic changes relating to the maintenance or condition of soil organic matter.

Detection of an oxidizable fraction of cytochrome oxidase in intact rat brain

Rapid-scanning reflectance spectrophotometry was used to evaluate the reduction-oxidation state of cytochrome oxidase in normoxic rat brain. Reflectance spectra were recorded from intact blood-perfused cerebral cortices after increased oxidative metabolic activity induced by direct cortical stimulation. Reflectance spectra taken from blood-free rat brain and from the rat ear vascular bed were used to identify cytochrome and hemoglobin components of spectra taken from intact brain. Cortical stimulation provoked shifts toward increased oxidation of cytochrome oxidase that were detectable in reflectance spectra. Observations of an oxidizable fraction of cytochrome oxidase demonstrate that a fraction of the cytochrome oxidase pool exists in a reduced state in normoxic brain. The presence of reduced cytochrome oxidase suggests that oxygen delivery to the brain is restricted by microvascular control mechanisms either as a function of brain metabolic physiology or as protection against oxygen toxicity.