Nanostructured semiconducting materials for efficient hydrogen generation

Massive production of hydrogen by water decomposition triggered by a solar light active photocatalyst is a major objective in chemistry and a promising avenue to overcome the global energy crisis. The development of efficient, stable, economically viable and eco-friendly photocatalysts for hydrogen production is a challenging task. This article reviews the use of nanocomposite in three combinations: metal oxide–metal oxide semiconductor, metal–metal oxide semiconductor and metal chalcogenide–metal oxide core–shell nanostructures. These core–shell structures occur in two forms: a simple form where the photocatalyst is either in the core or the shell or in a more complex system where the core–shell structure comprises a co-catalyst deposited on a semiconducting material. We discuss the design, synthesis and development of semiconductor-based nanocomposite photocatalysts for hydrogen production. The major points are the role of catalytic active sites, the chemical nature of sacrificial agents, the effect of light sources, the variable light intensity and the energy efficiency calculation. For TiO₂-based nanocomposites, the metal oxide or metal co-catalyst loading of 1.0–3.0 wt% was optimal. TiO₂ nanotube–CuO hybrid nanocomposites produce 1,14,000 µmol h^?1 \({\text{g}}^{ - 1}_{\text{cat}}\), whereas TiO₂/Au nanocomposites display 1,60,000 µmol h^?1 \({\text{g}}^{ - 1}_{\text{cat}}\). For core–shell catalysts, a shell thickness of 2–20 nm was found for the best activity, and its performance is as follows: (a) CdS–NiO system produces around 19,949 µmol h^?1 \({\text{g}}^{ - 1}_{\text{cat}}\) and (b) CuO–Cr₂O₃ as co-catalyst immobilized on TiO₂ system produces around 82,390 µmol h^?1 \({\text{g}}^{ - 1}_{\text{cat}}\).     

悬浮填料生物反应器处理低浓度氨氮的动力学特性分析

城市污水经一级强化处理后,NH3-N浓度为10~15mg/L,CODCr为40~60mg/L。试验利用悬浮填料床对一级强化处理出水中的氨氮进行深度处理,分析了悬浮填料表面负荷和硝化速率与水力停留时间的关系,并模拟分析了硝化速率与氨氮浓度的关系。结果表明,悬浮填料床内混合液氨氮浓度为0.5~2.5mg/L时,硝化反应符合半级反应动力学,半级反应速率常数k1/2为0.48(g/m)0.5/d;混合液氨氮浓度>2.1mg/L时,硝化反应遵循零级反应动力学,rmax为0.71g/(m2.d)。动力学理论计算值与实际运行结果基本吻合,说明动力学模型对悬浮填料床的硝化性能具有良好的预测和指导意义。     

A framework for evaluating regional-scale numerical photochemical modeling systems

This paper discusses the need for critically evaluating regional-scale (~200–2,000 km) three-dimensional numerical photochemical air quality modeling systems to establish a model’s credibility in simulating the spatio-temporal features embedded in the observations. Because of limitations of currently used approaches for evaluating regional air quality models, a framework for model evaluation is introduced here for determining the suitability of a modeling system for a given application, distinguishing the performance between different models through confidence-testing of model results, guiding model development and analyzing the impacts of regulatory policy options. The framework identifies operational, diagnostic, dynamic, and probabilistic types of model evaluation. Operational evaluation techniques include statistical and graphical analyses aimed at determining whether model estimates are in agreement with the observations in an overall sense. Diagnostic evaluation focuses on process-oriented analyses to determine whether the individual processes and components of the model system are working correctly, both independently and in combination. Dynamic evaluation assesses the ability of the air quality model to simulate changes in air quality stemming from changes in source emissions and/or meteorology, the principal forces that drive the air quality model. Probabilistic evaluation attempts to assess the confidence that can be placed in model predictions using techniques such as ensemble modeling and Bayesian model averaging. The advantages of these types of model evaluation approaches are discussed in this paper.     

Crop damage and livestock depredation by wildlife: a case study from Nanda Devi Biosphere Reserve,India

The success of conserving biological resources in any Biosphere Reserve or protected area depends on the extent of support and positive attitudes and perceptions of local people have towards such establishments. Ignoring the dependence of the local people for their subsistence needs on resources of such areas leads to conflicts between protected area managers and the local inhabitants. Crop yield losses and livestock depredation were serious problems observed in most buffer zone villages of Nanda Devi Biosphere Reserve. In the present study 10 villages situated in the buffer zone of Nanada Devi Biosphere Reserve (1612 km2 area) in Chamoli district of Uttaranchal, India were studied during 1996-97 using a questionnaire survey of each household (419 = households; 2253 = total population in 1991; 273 ha = cultivated area). Estimates of crop yield losses were made using paired plots technique in four representative villages for each crop species. The magnitude of crop yield losses varied significantly with the distance of agricultural field from forest boundary. The total crop yield losses were high for wheat and potato in all the villages. The spatial distribution of total crop yield losses in any village indicated that they were highest in the area near to forest and least in the area near to village for all crops. Losses from areas near to forest contributed to more than 50% of total losses for each crop in all villages. However, in Lata, Peng and Tolma villages, the losses are high for kidney bean and chemmi (local variety of kidney bean) which varied between 18.5% to 30% of total losses in those villages. Potato alone represents 43.6% of total crop yield loss due to wildlife in Dronagiri village in monetary terms. Among the crops, the monetary value of yield losses are least for amaranth and highest for kidney bean. The projected total value of crop yield losses due to wildlife damage for buffer zone villages located in Garhwal Himalaya is about Rs. 538,620 (US$ 15,389). Besides food grains, horticultural crops i.e. apple, also suffered maximum damage. Major wildlife agents responsible for crop damage were wild boar, bear, porcupine, monkey, musk deer and partridge (chokor). Monkey and wild boar alone accounted for about 50% to 60% of total crop damage in the study villages. Goat and sheep are the major livestock killed by leopard. The total value of livestock losses at prevailing market rates is about Rs. 1,024,520 (US$ 29,272) in the study villages. Due to existing conservation policies and laxity in implementation of preventive measures, the problems for local inhabitants are increasing. Potential solutions discussed emphasize the need to undertake suitable and appropriate protective measures to minimize the crop losses. Change in cropping and crop composition, particularly cultivation of medicinal plants (high value low volume crops), were also suggested. Besides, fair and quick disbursement of compensation for crop loss and livestock killing need to be adopted. Local people of the buffer zone area already have a negative attitude towards park/reserve establishment due to socio-political changes inducing major economic losses and this attitude may lead to clashes and confrontations if proper ameliorative measures are not taken immediately.     

Forestry for sustainable biomass production and carbon sequesteration in India

A sustainable forestry scenario aimed at meeting the projected biomassdemands, halting deforestation and regenerating degraded forests wasdeveloped and analyzed for additionality of mitigation and cost-effectivenessfor India. Similarly, mitigation potential of a commercial forestry scenarioaimed at meeting the biomass demands from forestry activities on privateland was assessed. India has a significant scale baseline scenario afforestationand effective forest conservation activities. India is afforesting at an averagegross rate of 1.55 × 10⁶ ha yr^-1 over the past 10 years, while the gross deforestation rate was 0.272 × 10⁶ ha yr^-1 during the same period. The sustainable forestry scenario could lead to an additional carbon (C) stock of 237 × 10⁶ Mg C during 2000 to 2012, while the commercial forestry scenario apart from meeting all the incremental biomass demands (estimated for 2000 to 2015) could potentially lead to an additional carbon stock of 78 × 10⁶Mg C during 2000 to 2012. Short- and Long-rotation forestry activities arecommercially viable. With appropriate policies and financial incentives allthe industrial wood, sawnwood and commercial fuelwood requirementcould be met through commercial forestry, so that government funds couldbe dedicated for conserving state owned forests and meeting subsistencebiomass demands. The commercial forestry activities could receive financialsupport under greenhouse gas (GHG) abatement programmes. The government, however, needs to develop institutions and guidelines to process, evaluate, approve and monitor forestry sector mitigation projects.     

Identification of novel eubacteria from spent mushroom compost (SMC) waste by DNA sequence typing: ecological considerations of disposal on agricultural land

A small study was undertaken to examine the microbiological characteristics of spent mushroom compost (SMC), which is the major waste by-product of the mushroom industry and which is regularly disposed off by application to agricultural land. The primary aim of this study was to examine SMC for the presence of faecal bacterial pathogens, including Campylobacter spp., Salmonella spp. and Listeria monocytogenes. Secondly it was desirable to quantify bacterial and fungal populations within SMC, and also qualitatively identify the diversity of bacterial populations within SMC, through employment of rDNA PCR and direct sequencing techniques on the culturable microflora. Conventional microbiological analyses of SMC material (n=30) from six commercial operations in both Northern Ireland and the Republic of Ireland, failed to detect Salmonella spp, Listeria spp. or Campylobacter spp. in any of the SMC material examined. Total aerobic plate counts gave a mean count of log10 7.01 colony forming units (cfu) per gram SMC material (range: log10 6.53-7.52 cfu/g). Fungal counts gave a mean count of log(10) 4.57 cfu per gram SMC material (range: log10 3.93-4.98 cfu/g). From a total of greater than 50 colony picks, a total of 12 bacterial morphotypes were identified and were further examined by employment of partial 16S rRNA gene amplification and sequencing techniques, yielding several genera and species, including Bacillus licheniformis, Bacillus subtilis, Klebsiella/Enterobacter sp. Microbacterium sp. Paenibacillus lentimorbus, Pseudomonas mevalonii, Sphingobacterium multivorum and Stenotrophomonas sp. This is the first preliminary report on the microbial diversity of SMC waste and demonstrates the presence of several species that have not been previously described in SMC, in addition to two potentially novel species within the genera Microbacterium and Stenotrophomonas. It is thereby important to examine the ecological microbe-microbe and plant-microbe interactions that are occurring between the native bacterial soil flora and those added annually (theoretically estimated at approximately 10(18) cells) through the application of SMC. Such studies would be beneficial in helping to ascertain the ecological consequences involved in the disposal of SMC waste on agricultural land.     

Fractionation studies and bioaccumulation of sediment-bound heavy metals in Kolleru lake by edible fish

Kolleru lake is the largest fresh water lake in the districts of East and West Godavari of Andhra Pradesh, India. Many anthropogenic sources contribute to the heavy metal pollution in the lake and the bioaccumulation of heavy metals in fish helps in assessing the aquatic pollution. Total contents and fractionation of selected heavy metals, viz., Zn, Cu, Cd, Pb, Cr, Ni and Co were measured in sediment sample and three edible fish. The investigation aimed at revealing differences in the accumulation pattern of heavy metals in fish inhabiting sediments characterized by varying metal bioavailability. The metal concentrations were found to be greater than the background concentrations of sediments indicating the anthropogenic origin of metals. Good recovery values were obtained for metal contents in sediments and fish. Large fractions of Zn, Cd and Cu were associated with mobile fraction of sediment and showed greater bioaccumulation in fish whereas Ni and Co were least mobilisable. The results clearly indicate that the fish of Kolleru lake are contaminated with metals and not advisable for human consumption.     

Effect of slaughter house pollution on the biochemical composition of Channa orientalis

The present study deals with the biochemical composition of Channa orientalis from a habitat polluted by slaughter house wastes in comparison to an unpolluted habitat of Mudasarlova stream of Visakhapatnam. The total proteins, carbohydrates and lipids were found to be less in the organisms collected from the polluted habitat. The probable reasons for these variations are discussed in detail.     

Metal Content in Selected Tissues and Shell of Pern A Virwis (L) From Pondicherry, East Coast of India

Mussels are good bioaccumulators of metals and have been used as indicators for environmental monitoring. in this study on P. viridis from Pondicherry coast, metal content (aluminium, lead, cadmium, copper and zinc) were analysed in selected tissues and shell nacre for a period of one year. the metal content shows that digestive gland accumulates higher concentrations of metal ions followed by gill, mantle and shell. of the different components (digestive gland, gill, mantle and shell nacre) of the organism, only shell nacre exhibited a significant relationship with ambient levels and therefore can be applied to temporal monitoring of metal contamination.