Average Mineralization Research Articles

Characterization of groundwater in arid zones (case of Ouargla basin)

The preservation of natural water resources occupies a dominant position in the expectations of the population in Algeria, particularly in the south of the country. The region of Ouargla is fed by groundwater and it is subject to a strong demand for water, including the share of agriculture. The quality of these waters varies from one zone to another. According to previous studies, the quality of these resources is mediocre and requires treatment. Then, it is essential to bring elements of knowledge and explanation to make an analysis of the situation and to implement the strategies face of the threats looming over the quality of water resources. The objective of this work is to evaluate the physico-chemical quality of water from different aquifers and determine their quality according to potability standards.The obtained results reveal that the waters of water table are very poor quality and they are too mineralized, very hard, high conductivity, in the other hand lower values are observed in the water of Albian aquifer, but its high temperature and their great depth makes it exploitation difficult. The waters of terminal complex (miopliocene and senonian) the more interesting for drinking water supply, show an average mineralization, with acceptable temperature 22 C˚, nevertheless they are bad physico-chemical quality according of WHO standards, these waters require a further treatment before distribution.

Mineralization of aromatic amines liberated during the degradation of a sulfonated textile colorant using Klebsiella pneumoniae strain AHM

Abstract An indigenous bacterium; Klebsiella pneumoniae strain AHM was acclimated from the vicinities exposed to the frequent discharge of untreated textile recalcitrant compounds. The bacterium was employed to decolorize and mineralize a sulfonated textile colorant; reactive orange 16 (RO16). An equation for quantifying the average mineralization rate, AMRRO16 μM/min of the liberated aromatic amines was established during the biotransformation. The strain had average decolorization and mineralization rate (ADRRO16 and AMRRO16) of 333.33 μg/min and 0.46 μM/min respectively, when incubated with 50 mg/L RO16 under static condition. The inducible oxidoreductases along with the spectral and chromatographic analyses proved that the biotransformation was due to the metabolism of K. pneumoniae strain AHM. The toxicological assessment of plant growth parameters and the chlorophyll concentrations of Phaseolus mungo, Triticum aestivum and Sorghum bicolor seedlings revealed the reduced toxic nature of the mineralized products.

Concocted bacterial consortium for the detoxification and mineralization of azoic-cum-sulfonic textile mill effluent

A bacterial consortium, comprising of three isolates; Achromobacter xylosoxidans strain APZ, Klebsiella pneumoniae strain AHM and Bacillus mannanilyticus strain AVS was concocted using the mixture design (MD) matrix. The concocted consortium was employed to degrade and mineralize a textile mill effluent (TME) having sulfone and azo groups. The average mineralization rate (AMRTME) of the liberated aromatic amines were more rapid than that of the individual strains, among them K. pneumoniae strain AHM was predominant. The analytical techniques confirmed that TME decolorization was due to biodegradation by the extracellular oxidoreductases, induced by the bacterial consortium. The azoic groups of the TME and the sulfones were not found in the treated solution which was analyzed by the mass spectral analyses. The phyto-toxicological parameters revealed the reduced toxic nature of the biotransformed products.

The calculation of desalination of mineralized porous ice at thawing

The results obtained in this work demonstrate that dynamics of desalination of porous ice depends on a mobility of ions of salts, and the mobility is determined by the diffusion coefficient. The ice was made by freezing of mineralized water of different chemical composition. Model calculations of average mineralization of the porous ice at its thawing were made, and the ion concentrations of different salts were defined. Values of the diffusion coefficients of the salt ions in the film of brine ice pellets were obtained by means of comparison of results of measurements and calculations of dynamics of content of the salt ions in a porous ice at its thawing. The diffusion coefficient of ions Na+, Cl−, SO4 2− is by order of magnitude larger than that of Ca2+ and by two orders of magnitudethan HCO3 −. This results in that the content of ions Na+, Cl−, SO42− decreases in porous ice at its thawing 3 times faster than the content of the ions Ca2+. Basing on analysis of chemical composition of drainage water in some regions in Russia a possibility to desalinate the porous ice formed during the winter sprinkling is demonstrated.

Effects of Different Fertilizer and Irrigation Water Types, and Dissolved Organic Matter on Soil C and N Mineralization in Crop Rotation Farmland

Inorganic N fertilizer and irrigation water types on the C and N dynamics are poorly understood. This work aimed to evaluate the effect of different N fertilizer and irrigation water types on soil C and N mineralization. The farmland experiment was conducted with three types of N fertilizer (urea, ammonium sulfate, and slow-release urea) and drip irrigation with two types of water (groundwater and reclaimed water) for a summer maize-winter wheat crop rotation. Soil samples were collected from the experimental farmland for incubation experiments. The results showed that the average cumulative mineralization of soil C (incubation 20 days) and N (incubation 14 weeks) in different treatments ranged from 73.50 to 91.37 mg kg−1 and 52.65 to 64.04 mg kg−1, respectively. N fertilization significantly increased dissolved organic carbon (DOC), dissolved organic nitrogen (DON), soil organic carbon (SOC), and soil organic nitrogen (SON) contents in the soils, but N fertilizer and irrigation water types had no significant influence on them. Correspondingly, N fertilization significantly enhanced the mineralization of C by 14.14–21.22 % and N by 15.81–22.16 % in soils but no significant difference among different N fertilizer types. Compared with groundwater, reclaimed water irrigation enhanced the mineralization of C by 3.33 % and N by 1.01 %, but the difference was not statistically significant. The cumulative mineralization of C and N in soils after DOM removal average significantly decreased 9.83 and 14.83 %, respectively, which indicates that DOM plays an important role in soil C and N mineralization. Our results indicate that inorganic N fertilization promotes soil C and N mineralization, which may inevitably aggravate global warning. Reclaimed water irrigation had similar influence on soil C and N mineralization as groundwater irrigation; thus, we recommend irrigation with reclaimed water in water shortage areas.

The ecosystem of Lake Kenon: past and present (Transbaikal Territory, Russia)

Present-day conditions of the Lake Kenon ecosystem are determined by a combination of natural and anthropogenic factors. We have estimated the effects of a complex of factors on the condition of the abiotic environment and on specific biological components in the lake ecosystem. Change in biogenic load has caused an increase in the role of phytoplankton in the general balance of organic matter during the high-water period. Charophytes are the main dominants of bottom vegetation. Anthropogenic load has caused a decrease in both fish species and fish capacity. The lake application as a water reservoir-cooler has influenced the average annual water mineralization (from 420 mg/L to 530.0 mg/L with a maximum 654 mg/L in 1993) and fluctuations in its hydrochemical composition. The present composition of the lake is sulfate-hydrocarbonate-chloride calcium-sodic-magnesium in character. SO 4–content is twice as much as the maximum permissible concentration in fishery waters. Water drainage from an ash disposal area to the lake has caused an increase in chemical-element concentrations including the heavy metals. Hg concentration in Perca fluviatilis muscles is 0.5 μg/g dry wt. Thus, understanding directions in the ecosystem of the water reservoir-cooler under changing hydrological conditions will let us forecast the consequences of new combined heat and power plant operation.

Adsorption and photocatalysis of 2-ethyl-1-hexanol over graphene oxide–TiO2 hybrids post-treated under various thermal conditions

High temperature (>300°C) post-treatment of two-dimensional graphene oxide-coupled titania (GO–TiO2) hybrids may enhance their photocatalytic performances. This concept has not yet been fully assessed. In the present study, we explored the applicability of GO–TiO2 hybrids synthesized using a chemical mixing method, followed by post-treatment under various thermal conditions (200–500°C), for the degradation of low-concentration gas-phase 2-ethyl-1-hexanol (2E1H) in continuous-flow mode under visible-light illumination. The morphological and optical characteristics of the synthesized photocatalysts were investigated by field-emission transmission electron microscopy, thermal gravimetric analysis, X-ray diffraction technique, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, and N2 adsorption–desorption analysis. The GO–TiO2 hybrid post-treated at 400°C exhibited longer breakthrough and saturation times and a higher capacity for 2E1H adsorption than did GO–TiO2 post-treated at 200°C. The photocatalytic 2E1H degradation efficiencies of the post-treated GO–TiO2 hybrids were superior to those of the untreated GO–TiO2 hybrid and neat TiO2 samples. Moreover, the photocatalytic activities of the GOkTiO2 hybrids increased as the post-treatment temperature increased from 200 to 400°C, and decreased as the temperature was further increased to 500°C, indicating that the treatment temperature can be increased up to at least 400°C without significant reduction of the photocatalytic performance. The photocatalytic activity of the GO–TiO2 hybrid post-treated at 400°C depended strongly on three process parameters: relative humidity, initial contaminant concentration, and catalyst mass. There was no appreciable loss of photocatalytic efficiency for the GO–TiO2 hybrid post-treated at 400°C after five cycles. The average 2E1H mineralization efficiency was 55.1%, while the average photocatalytic efficiency was 99.3%. Two gaseous organic compounds, i.e., 3-heptanone and 2-ethyl hexanal, and carbon monoxide were identified as the primary partially oxidized intermediates. The average carbon monoxide concentration (0.49ppm) was well below the permissible 8-h exposure level (25ppm).

Sclerostin deficiency is linked to altered bone composition.

High bone mass in animals and humans with sclerostin deficiency is associated with increased bone strength, which is not the case for all disorders with high bone mineral density, some of which are even associated with fragility fractures owing to unfavorable bone composition. In the current study we investigated whether alterations in bone composition may contribute to the bone strength characteristics associated with lack of sclerostin. We examined cortical bone of Sost-knockout (KO) mice (n = 9, 16 weeks old) and sclerosteosis patients (young [4 to 14 years], n = 4 and adults [24 and 43 years], n = 2) by quantitative backscattered electron imaging and Raman microspectroscopy and compared it to bone from wild-type mice and healthy subjects, respectively. In Sost-KO mice endocortical bone exhibited altered bone composition, whereas subperiosteal bone was unchanged. When comparing endocortical bone tissue of identical tissue age as defined by sequential dual fluorochrome labeling the average bone matrix mineralization was reduced -1.9% (p < 0.0001, younger tissue age) and -1.5% (p < 0.05, older tissue age), and the relative proteoglycan content was significantly increased. Similarly, bone matrix mineralization density distribution was also shifted toward lower matrix mineralization in surgical samples of compact bone of sclerosteosis patients. This was associated with an increase in mineralization heterogeneity in the young population. In addition, and consistently, the relative proteoglycan content was increased. In conclusion, we observed decreased matrix mineralization and increased relative proteoglycan content in bone subcompartments of Sost-KO mice-a finding that translated into sclerosteosis patients. We hypothesize that the altered bone composition contributes to the increased bone strength of patients with sclerostin deficiency.

Do models of organic carbon mineralization extrapolate to warmer tropical sediments?

Freshwater sediments are important sites of organic carbon (OC) burial and mineralization. Previous studies indicate that warming can increase rates of OC mineralization, implying more CO2 release from sediments and, consequently, less OC burial, but temperatures typical of tropical ecosystems are poorly represented in the models of temperature and OC mineralization. We measured OC mineralization rates in 61 Brazilian tropical systems, including rivers, streams, lakes, coastal lagoons, and reservoirs from different regions (Pantanal, Amazonia, Atlantic Forest, and coastal areas). Oxygen consumption and dissolved inorganic carbon production in sediment core incubations were used for estimating OC mineralization rates. Multiple regression models were used to investigate the importance of temperature and other variables to predict OC mineralization. The average OC mineralization rate for all systems was 1223 ± 950 mg C m‒2 d‒1. Rates increased significantly with increasing temperature and varied across system types and regions. In addition, salinity, total nitrogen, and chlorophyll a were important factors controlling OC mineralization in tropical sediments. The pattern of increasing mineralization with temperature was remarkably consistent with theoretical and empirical expectations. The explanatory power of previous temperature vs. mineralization models is confirmed and enhanced by the addition of the tropical data that substantially extended the temperature range.

土壤水分和氮添加对华北平原高产农田有机碳矿化的影响

A highly productive soil from the North China Plain was used for a homoeothermic incubation study at 25 ℃ for105 d to identify the characteristics of soil organic C mineralization and investigate the impacts on that mineralization of soil moisture,and addition of inorganic and organic nitrogen. Four fertilizer input levels and four moisture gradient treatments were used in the experiment,including a control( S0),inorganic nitrogen( urea,S1),inorganic and organic nitrogen( 50% urea+50% chicken manure,S2) and organic nitrogen( chicken manure,S3). The N application rate of the S1,S2 and S3 treatments was 200 kg N /hm2,with 20% field capacity( M0),50% field capacity( M1),75% field capacity( M2) and 100% field capacity( M3) used with each soil treatment,giving a total of sixteen treatments with three replicates. The soil organic C mineralization rate of all treatments sharply declined at the first day of incubation,decreased by 57. 2% —75. 0% over the first 7 d,and appeared as secondary peaks at the 20 thday of incubation. Soil organic C mineralization ranged from 208. 8 to 1161 mg /kg and mainly happened in the first 50 days,especially in the first 30 days( accounting for 59.1%—69.9% of the total mineralized soil C). The net mineralization rate of all treatments ranged from0. 07% to 2. 01%. According to simulation using a double exponential model,the potential organic C mineralization flux and rate were 219. 1—1204 mg /kg and 1. 75% —9. 66%,respectively. The active and resistant pools were 53. 0—135. 1mg /kg and 156. 9—1069 mg /kg,respectively. Organic C mineralization of soil with fertilizer was significantly affected by the soil water content( P 0. 05). The higher the soil water content( from 25% to 100% of field capacity),the more organic C accumulated in the soil under the same fertilizer addition conditions. The relationship between organic C mineralization and soil water content was well fitted by a quadratic function equation( P 0. 05). When the soil water content increased from M0 to M3,the average organic C mineralization rate significantly increased to 18. 4 mg·kg-1·d-1,20. 9 mg·kg-1·d-1,22.3 mg·kg-1·d-1and 23. 5 mg·kg-1·d-1from 4. 47 mg·kg-1·d-1,4.64 mg·kg-1·d-1,4.61 mg·kg-1·d-1and 4. 88 mg·kg-1·d-1,respectively. However,the increasing rate gradually reduced to 30.0%—43.9% and-3.08%—12. 4% from 66. 9% —261%. The amount of C mineralized in the soils amended with fertilizer was significantly higher than that in the control treatment. The average mineralization rates of the S1,S2 and S3 treatments increased above that in the S0 treatment by 3. 86% —27. 9%,3. 28% —39. 5% and 9. 27% —31. 5%,respectively. However,there were no significant differences among the S1,S2 and S3 treatments at the same soil water content conditions. Thus there were no significant differences between the forms of added nitrogen,i. e. organic nitrogen( chicken manure) or inorganic nitrogen( urea). The amounts of soil organic C mineralization were linearly related to the microbial biomass carbon( P0.01) and mineral nitrogen( P0. 05),indicating that the contents of microbial biomass carbon and mineral nitrogen were the key factors affecting the mineralization of C. It can be concluded that soil organic C mineralization was significantly affected by soil moisture and nitrogen addition,and that there was a significant interaction with soil moisture and nitrogen addition( P0. 05).

Impact of water mass mixing on the biogeochemistry and microbiology of the Northeast Atlantic Deep Water

The extent to which water mass mixing contributes to the biological activity of the dark ocean is essentially unknown. Using a multiparameter water mass analysis, we examined the impact of water mass mixing on the nutrient distribution and microbial activity of the Northeast Atlantic Deep Water (NEADW) along an 8000 km long transect extending from 62°N to 5°S. Mixing of four water types (WT) and basin scale mineralization from the site where the WT where defined to the study area explained up to 95% of the variability in the distribution of inorganic nutrients and apparent oxygen utilization. Mixing-corrected average O2:N:P mineralization ratios of 127(±11):13.0(±0.7):1 in the core of the NEADW suggested preferential utilization of phosphorus compounds while dissolved organic carbon mineralization contributed a maximum of 20% to the oxygen demand of the NEADW. In conjunction with the calculated average mineralization ratios, our results indicate a major contribution of particulate organic matter to the biological activity in the NEADW. The variability in prokaryotic abundance, high nucleic acid containing cells, and prokaryotic heterotrophic production in the NEADW was explained by large scale (64-79%) and local mineralization processes (21-36%), consistent with the idea that deep-water prokaryotic communities are controlled by substrate supply. Overall, our results suggest a major impact of mixing on the distribution of inorganic nutrients and a weaker influence on the dissolved organic matter pool supporting prokaryotic activity in the NEADW.

Investigating the performance of a novel cyclic rotating-bed biological reactor compared with a sequencing continuous-inflow reactor for biodegradation of catechol in wastewater

The main objective of this study was to investigate the performance of a cyclic rotating-bed biological reactor (CRBR) in comparison to a sequencing continuous-inflow reactor (SCR) for the biodegradation and mineralization of catechol. Results showed that catechol degradation and mineralization in the SCR at the organic loading of 7.82kgCOD/m(3)d and the hydraulic retention time (HRT) of 9h were 28.2% and 10.3%, respectively. Under similar operating conditions to SCR, steady-state performance of CRBR with polyurethane foam (PUF) media for degradation and mineralization of catechol achieved was 98.7% and 97.9%, respectively. In comparison, the CRBR with 2H media attained average steady-state catechol degradation and mineralization of 89.1% and 83.6%, respectively, under similar conditions. Accordingly, the CRBR with PUF media presents a promising process for efficiently treating wastewater containing high concentrations of toxic, inhibitory and resistant compounds at a relatively short HRT.

Gross nitrogen mineralization in pulse-crop rotations on the Northern Great Plains

Pulse crops represent an ever-increasing proportion of cropping systems in the Northern Great Plains. Previous studies have noted apparent benefits associated with pulse crop production that extend beyond the reduced need for N fertilizer in the year of production; these benefits have been attributed to the quality of pulse residues and their effects on N dynamics in subsequent years. This study used isotope dilution techniques to quantify the N-cycling effects of pulse crops in the rotation. Gross N mineralization was measured over three growing seasons at two Agriculture and Agri-Food Canada research sites in Saskatchewan, Canada: Scott (four rotations; one with pulse crop) and Swift Current (three rotations; one with pulse crop). Gross nitrification and the relative contribution of nitrification vs. denitrification to N2O emissions were also measured. Across all dates and rotations, the average gross mineralization rate at Scott was 2.0 ± 4.0 mg NH4+-N kg−1 soil d−1 and at Swift Current was 1.4 ± 3.9 mg NH4+-N kg−1 soil d−1. At both sites, rates were highly variable across the growing season, but tended to be higher at anthesis than either pre-seeding or post-harvest. The only significant difference among rotations was at Swift Current, where the fertilized continuous wheat rotation had the highest gross mineralization rates (rotation average: 2.3 mg NH4+-N kg−1 soil d−1). The lack of difference among most rotations was particularly notable given the differences in residue quantity among the crops. Ultimately, the lower quantity of residues produced by pulse crops appears to be offset by their higher quality.

Effects of mineral content on the fracture properties of equine cortical bone in double-notched beams

We recently developed a method to measure cortical bone fracture initiation toughness using a double-notched beam in four-point bending. This method was used to test the hypothesis that mineralization around the two notch roots is correlated with fracture toughness and crack extension (physical damage). Total energy absorbed to failure negatively correlated with average mineralization of the beam (r2=0.62), but not with notch root mineralization. Fracture initiation toughness was positively correlated to mineralization at the broken notch root (r2=0.34). Crack length extension at the unbroken notch was strongly negatively correlated with the average mineralization of the notch roots (r2=0.81) whereas crack length extension at the broken notch did not correlate with any of the mineralization measurements. Mineralization at the notch roots and the average mineralization contributed independently to the mechanical and damage properties. The data are consistent with a hypothesis that a) high notch root mineralization results in less stable crack length extension but high force to initiate unstable crack propagation while b) higher average mineralization leads to low post-yield (and total) energy absorption to failure.

Transport of dissolved load in the hydrologically extreme conditions in the Crnica river basin

During 2010, 62065.3 t of the dissolved load were transported from the Crnica Basin, which was 5.1 times higher than the long-term average value. In hydrological terms the studied year was specific. In the period from January to May the amount of runoff water was significantly above the average perennial values, while in the period from August to November the amount was below the perennial average. According to the hydrological conditions in the period January-May 82.3% were transported, and in the period August-November only 5.1% of the annual dissolved load amount. Most of the year (54.2% of the time) the specific runoff was less than 10 l/s/km2, the average water mineralization was 374.9 mg/l, and in that time 13% of the total annual amount of the dissolved load was evacuated. On the other hand, the specific runoffs greater than 50 l/s/km2 represented 13.4% of the annual frequency, the average water mineralization was 263.3 mg/l, but for that time period even 53.9% of the annual quantity of the dissolved load was evacuated.

Characterization of the transglutaminase gene family in zebrafish and in vivo analysis of transglutaminase-dependent bone mineralization

We have characterized the protein cross-linking enzyme transglutaminase (TGs) genes in zebrafish, Danio rerio, based on the analysis of their genomic organization and phylogenetics. Thirteen zebrafish TG genes (zTGs) have been identified, of which 11 show high homology to only 3 mammalian enzymes: TG1, TG2 and FXIIIa. No zebrafish homologues were identified for mammalian TGs 3-7. Real-time PCR analysis demonstrated distinct temporal expression profiles for zTGs in larvae and adult fish. Analysis by in situ hybridization revealed restricted expression of zTG2b and zFXIIIa in skeletal elements, resembling expression of their mammalian homologues in osteo-chondrogenic cells. Mammalian TG2 and FXIIIa have been implicated in promoting osteoblast differentiation and bone mineralization in vitro, however, mouse models lacking either gene have no skeletal phenotype likely due to a compensation effect. We show in this study that mineralization of the newly formed vertebrae is significantly reduced in fish grown for 5 days in the presence of TG inhibitor KCC-009 added at 3-5 days post fertilization. This treatment reduces average vertebrae mineralization by 30%, with complete inhibition in some fish, and no effect on the overall growth and vertebrae number. This is the first in vivo demonstration of the crucial requirement for the TG-catalyzed cross-linking activity in bone mineralization.

Mineralização e desnitrificação do nitrogênio no solo sob sistema plantio direto

O conhecimento da dinâmica do N no solo pode facilitar na decisão da rotação de culturas empregada e aplicação de fertilizante para as culturas. O objetivo deste estudo foi avaliar os estoques de N, o N-inorgânico, a mineralização do N e a desnitrificação sob sistema plantio direto (SPD). O experimento foi desenvolvido na Fazenda Santa Branca em Tibagi (PR), em Latossolo Vermelho distroférrico de textura argilosa, no período de setembro de 2000 a outubro de 2001. Os tratamentos dispostos em faixas não casualisadas com parcelas subdivididas foram: plantio direto por 12 e 22 anos com as sucessões milho/trigo (M/T) e soja/trigo (S/T). As quantidades de N-inorgânico e a mineralização e nitrificação líquidas foram maiores no SPD com 22 anos que no SPD 12 anos. A sucessão de culturas empregada não influenciou a mineralização líquida e a nitrificação líquida. As emissões de N2O foram 25% superiores na sucessão M/T em relação a S/T. O tempo de SPD aumentou o estoque de N no solo, assim como as quantidades de N-inorgânico e a mineralização e nitrificação, contudo, não foram observados maiores emissões de óxido nitroso.

Grazing and landscape controls on nitrogen availability across 330 South African savanna sites

AbstractThe availability of nitrogen (N) is an important determinant of ecosystem and community dynamics for grasslands and savannas, influencing factors such as biomass productivity, plant and herbivore composition, and losses of N to waters and the atmosphere. To better understand the controls over N availability at landscape to regional scales, we quantified a range of plant and soil characteristics at each of 330 sites in three regions of South Africa: Kruger National Park (KNP), private game reserves adjacent to KNP (private protected areas – PPAs) and Hluhluwe‐iMfolozi Park (HiP). In comparing regions and sites within regions, grazing appeared to have a strong influence on N availability. Sites in the PPAs adjacent to KNP as well as sodic and alluvial sites in general typically had the highest N availability. The high N availability of these sites was not generally associated with greater potential N mineralization, but instead with less grass biomass and more forb biomass that indicated greater grazing pressure. Whereas sodic sites had a long history of high N availability as evidenced by their high soil δ15N, the greater N availability in the PPAs over the two parks appeared to be relatively recent. Grazer biomass, average potential mineralization rates and grass biomass for HiP were greater than KNP, yet there were no differences in N availability as indexed by soil and foliar δ15N between sites in the two parks. Although the short‐term increase in N availability in PPAs is not necessarily deleterious, it is uncertain whether current productivity levels in those ecosystems is sustainable. With differences in management causing herbivore biomass to be 150% greater in the PPAs than the adjacent KNP, changes in plant communities and nitrogen cycling might lead to long‐term degradation of these ecosystems, their ability to sustain herbivore populations, and also serve as an economic resource for the region.

Effect of applied potential on photocatalytic phenol degradation using nanocrystalline TiO2 electrodes

The activity of transparent and highly porous nanocrystalline TiO2 electrodes for phenol degradation by heterogeneous photocatalysis was investigated. Electrochemical characterization, performed for electrodes with areas=1.0cm2, revealed that the capacitance values increased under irradiation. Electrodes with areas=9.0cm2 were used for remediation of 10mL of an aqueous solution containing 50mgL−1 of phenol. Irradiated by a solar simulator, removal of 48% of total organic carbon was achieved after 3h. The efficiency was significantly enhanced for electrochemically assisted photocatalysis; the average mineralization was 78% after 3h and was almost complete after 6h for a TiO2 electrode externally connected to a Pt counter-electrode and biased at +0.7 or +1.1V with a potentiostat, or by a series connection to a solar cell. Phenol degradation exhibited pseudo-first-order kinetics, and application of the bias potential increased the rate constant from 0.21 to 0.47h−1. Applying a potential bias to the TiO2 electrode minimizes the recombination of photogenerated charge carriers and enhances the photocatalytic activity towards organic pollutant degradation.

The chemical composition of surface water in the influence zone of the Severonikel smelter

This paper reports data on the chemical composition of surface waters (predominant ions and trace elements: approximately 40 parameters and elements) in the influence zone of the Severonikel Cu-Ni smelter in the town of Monchegorsk, Murmansk oblast. The long-continued discharge of waste waters has increased the mineralization and changed the proportions of ions in surface waters in the area: water in the sewage pond of the smelter is classed with brackish waters of the S 4 2− class, Na+ group. The sequence of major ions in water bodies under aerotechnogenic load retains the natural succession of major cations, but their concentrations slightly increase. The maximum concentration of ions in the surface waters of the Monchegorsk testing area were detected in wintertime, and the minimum contents occur during the high water period. Water bodies under aerotechnogenic load are characterized by average mineralization values much higher than is natural. The highest concentrations of Ni and Cu (two to three orders of magnitude higher than the assumed background values) and practically all trace elements were found in water bodies receiving waste waters from the smelter. The concentrations of Ni and other heavy metals in the Moncha River are much lower than in other water bodies but more than one order of magnitude higher than the assumed background concentrations.