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81.
E. Roshan Ara Begum Shenbagarathai Rajaiah K. Bhavani Manjula Devi K. Karthika Chidambaranathan Gowri Priya 《Journal of Polymers and the Environment》2017,25(3):578-585
In recent years there is a growing need in generating a biocompatible and cost effective porous scaffold for tissue engineering purposes. Therefore, this study focused on conversion of the shell waste of locally available crab variety P.pelagicus (Blue swimming crab) into the chitosan scaffold. As the poor mechanical strength of chitosan limits its usage in tissue engineering, it was blended with alginate. The scaffolds were prepared by the freeze gelation method which requires less time and minimum energy, with fewer residual solvent and easier to scale up. To the best of our knowledge there are no reports on scaffold preparation from the extracted chitosan, blended with alginate by freeze gelation method. The biological properties of chitosan-alginate scaffolds (Cts–Alg) were evaluated and compared with those of chitosan scaffolds. The prepared scaffolds were characterized by SEM, swelling property, in vitro enzymatic degradation, and hemo, biocompatibility properties. Chitosan-alginate scaffolds had an average pore size of 40 μm and tensile strength of 0.564 ± 0.0.018 % MPa. Its swelling ratio was 27.5 ± 0.28 %, with mass loss percentage of 10 ± 0.33 % after 4 weeks of degradation. It has exhibited good hemocompatible properties too. Mouse fibroblast 3T3 cells were able to adhere and proliferate well in the blended scaffold. All these results indicated that chitosan-alginate scaffold is a suitable alternative substitute for tissue engineering. 相似文献
82.
Lal S Sahu LK Venkataramani S Mallik C 《Journal of environmental monitoring : JEM》2012,14(4):1159-1166
Measurements of light (C(2)-C(5)) non-methane hydrocarbons (NMHCs) were made along with ozone (O(3)), oxides of nitrogen (NO(x)), carbon monoxide (CO) and methane (CH(4)) at Hissar and Kanpur in the Indo-Gangetic Plain (IGP) in India during the month of December, 2004. Air samplings during noon and evening hours provided an opportunity to study the emission characteristics and changes during this period at these sites. The mixing ratio of O(3) was higher during noon hours due to photochemical formation, while the levels of precursor gases showed elevated values during the evening hours on a clear sky day. On foggy days there is no such variation. The lower mixing ratios of O(3) observed on foggy days could be due to the slower rate of photochemical formation caused by a reduction in solar flux and surface deposition caused by the presence of a stable planetary boundary layer. Propene and ethene show the highest evening to noon ratio due to their faster reactivities with OH radicals. Correlations among different species of the measured gases indicate contributions of emissions from biomass and biofuel burning as well as fossil fuel combustion. Although qualitatively in relation to O(3), the propylene (propene) equivalents of NMHCs have been calculated to investigate their roles in O(3) photochemistry and compared with the data from Ahmedabad, an urban site in western India. The important result, which has emerged from the analysis of the observed data, is that while the total amount of these NMHCs is least at Hissar and highest at Ahmedabad, the total propylene-equivalent is highest at Hissar and lowest at Ahmedabad. Further, these two sites in the IGP show significant contributions, almost 72-77%, by propene and ethene while the contribution by these two gases at Ahmedabad is only about 47%. The surface level mixing ratios of O(3) could be treated as representative for the chemical characterization of air mass at a regional scale over the IGP as the month long trends of O(3) show significant similarity compared to the trends in precursors at the two sites. 相似文献
83.
Subhendu Adhikari Rattan Lal Han-Ping Wang 《Environmental monitoring and assessment》2014,186(3):1569-1574
Soil samples were collected from four aquaculture ponds (yellow perch culture), a control pond (without aquaculture activities, fallow pond), crop land (under corn), and forest land to estimate the carbon (C) sequestration potential in the Piketon county, Ohio, USA. The averaged total of C was 6.5?±?2, 8.8?±?2, 8.53?±?0.2 and 10.49?±?1.1 Mg/ha (Mg=106g) in <?0.25 mm fraction; 15.2?±?2, 16.0?±?3, 11.49?±?0.8 and 17.23?±?3.4 Mg/ha in micro aggregates (0.25–2.5 mm); and 22.1?±?3, 26.4?±?3, 12.16?±?1.6 and 18.51?±?4.3 Mg/ha in macro aggregates (?>?2.5mm), for aquaculture ponds, control ponds, cropland and forest land, respectively. The soil/sediment C pool followed the order of forest?>?crop land soils?>?aquaculture pond soils. 相似文献
84.
Singh SB Lal SP Pant S Kulshrestha G 《Journal of environmental science and health. Part. B》2008,43(1):27-33
A fungal strain able to use atrazine (2-chloro-4-ethylamino-5-isopropylamino-1,3,5-triazine) as a source of nitrogen was isolated from a corn field soil that has been previously treated with the herbicide. This strain was purified and acclimatized to atrazine at a higher level in the laboratory. A supplemented N was required to trigger the reaction. Atrazine was degraded at a faster rate in inoculated mineral salt medium (MSM) than non-inoculated MSM. Within 20 days, nearly 34% of the atrazine was degraded in inoculated medium while only 2% of the herbicide was degraded in non-inoculated medium. Degradation of atrazine by the isolated fungal strain was also studied in sterile and non-sterile soil to determine the compatibility of the isolated strain with native microorganisms in soil. The degradation of atrazine was found to be more in inoculated sterile soil than in inoculated non-sterile soil. Cell free extract (CFE) of fungal mycelium degraded about 50% of the atrazine in buffer in 96 hours compared to the control. Four atrazine metabolites were isolated and characterized by LCMS. On the basis of morphological parameters the isolate was identified as Penicillium species. Results indicated that the microorganism may be useful for remediation of atrazine-contaminated soil. 相似文献
85.
The broad climatological features associated with the Asian monsoon circulation, including its mean state and intraseasonal
and interannual variability over the Indian subcontinent as simulated in the National Center for Atmospheric Research (NCAR)
global coupled climate system model (CSM) in its control reference experiment, are presented in this paper. The CSM reproduces
the seasonal cycle as well as basic observed patterns of key climatic parameters reasonably well in spite of some limitations
in simulation of the monsoon rainfall. However, while the seasonality in rainfall over the region is simulated well, the simulated
area-averaged monsoon rainfall is underestimated to only about 60% of the observed rainfall. The centers of maxima in simulated
monsoon rainfall are slightly displaced southward as compared to the climatological patterns. The cross-equatorial flow in
simulated surface wind patterns during summer is also stronger than observed with an easterly bias. The transient experiment
with a 1% per year compound increase in CO2 with CSM suggests an annual mean area-averaged surface warming of about 1.73 °C over the region at the time of CO2 doubling. This warming is more pronounced in winter than during the monsoon season. A net increase in area-averaged monsoon
rainfall of about 1.4 mm day–1, largely due to increased moisture convergence and associated convective activity over the land, is obtained. The enhanced
intraseasonal variability in the monsoon rainfall in a warmer atmosphere is confined to the early part of the monsoon season
which suggests the possibility of the date of onset of summer monsoon over India becoming more variable in future. The enhanced
interannual and intraseasonal variability in the summer monsoon activity over India could also contribute to more intense
rainfall spells over the land regions of the Indian subcontinent, thus increasing the probability of extreme rainfall events
in a warmer atmosphere.
Electronic Publication 相似文献
86.
Atreya K Sharma S Bajracharya RM Rajbhandari NP 《Journal of environmental management》2008,88(3):547-555
In Nepal, soil erosion under maize (Zea mays) agro-ecosystems is most critical during the pre-monsoon season. Very few field experiments have been conducted on reduced tillage and rice straw (Oryza sativa) mulching, although these conservation approaches have been recommended. Thus, a five replicate field experiment was established in 2001 at Kathmandu University (1500 m above sea level) on land with 18% slope to evaluate the efficiency of reduced tillage and mulching on soil and nutrient losses and maize yield. The results showed non-significant differences among conservation approaches on runoff and maize yield. Mulching and reduced tillage significantly lowered annual and pre-monsoon soil and nutrient losses compared to conventional tillage. Soil organic matter (SOM) and nitrogen losses associated with eroded sediment were significantly higher in conventional tillage. However, due to limited availability and high opportunity cost of rice straw, reduced tillage would be a better option for soil and nutrient conservation without sacrificing economic yield in upland maize agro-ecosystems. 相似文献
87.
Paraffin deposition problems, that have plagued the oil industry, are currently remediated by mechanical and chemical means. However, since these methods are problematic, a microbiological approach has been considered. The bacteria, required for the mitigation of paraffin deposition problems, should be able to survive the high temperatures of oil wells and degrade the paraffins under low oxygen and nutrient conditions while sparing the low carbon chain paraffins. In this study, a thermophilic paraffinic wax degrading bacterial strain was isolated from a soil sample contaminated with paraffinic crude oil. The selected strain, Geobacillus TERI NSM, could degrade 600mg of paraffinic wax as the sole carbon source in 1000ml minimal salts medium in 7d at 55 degrees C. This strain was identified as Geobacillus kaustophilus by fatty acid methyl esters analysis and 16S rRNA full gene sequencing. G. kaustophilus TERI NSM showed 97% degradation of eicosane, 85% degradation of pentacosane and 77% degradation of triacontane in 10d when used as the carbon source. The strain TERI NSM could also degrade the paraffins of crude oil collected from oil wells that had a history of paraffin deposition problems. 相似文献
88.
Global warming risks from emissions of green house gases (GHGs) by anthropogenic activities, and possible mitigation strategies of terrestrial carbon (C) sequestration have increased the need for the identification of ecosystems with high C sink capacity. Depleted soil organic C (SOC) pools of reclaimed mine soil (RMS) ecosystems can be restored through conversion to an appropriate land use and adoption of recommended management practices (RMPs). The objectives of this paper are to (1) synthesize available information on carbon dioxide (CO2) emissions from coal mining and combustion activities, (2) understand mechanisms of SOC sequestration and its protection, (3) identify factors affecting C sequestration potential in RMSs, (4) review available methods for the estimation of ecosystem C budget (ECB), and (5) identify knowledge gaps to enhance C sink capacity of RMS ecosystems and prioritize research issues. The drastic perturbations of soil by mining activities can accentuate CO2 emission through mineralization, erosion, leaching, changes in soil moisture and temperature regimes, and reduction in biomass returned to the soil. The reclamation of drastically disturbed soils leads to improvement in soil quality and development of soil pedogenic processes accruing the benefit of SOC sequestration and additional income from trading SOC credits. The SOC sequestration potential in RMS depends on amount of biomass production and return to soil, and mechanisms of C protection. The rate of SOC sequestration ranges from 0.1 to 3.1 Mg ha(-1) yr(-1) and 0.7 to 4 Mg ha(-1) yr(-1) in grass and forest RMS ecosystem, respectively. Proper land restoration alone could off-set 16 Tg CO2 in the U.S. annually. However, the factors affecting C sequestration and protection in RMS leading to increase in microbial activity, nutrient availability, soil aggregation, C build up, and soil profile development must be better understood in order to formulate guidelines for development of an holistic approach to sustainable management of these ecosystems. The ECBs of RMS ecosystems are not well understood. An ecosystem method of evaluating ECB of RMS ecosystems is proposed. 相似文献
89.
Soil erosion and the global carbon budget 总被引:62,自引:0,他引:62
Lal R 《Environment international》2003,29(4):437-450
Soil erosion is the most widespread form of soil degradation. Land area globally affected by erosion is 1094 million ha (Mha) by water erosion, of which 751 Mha is severely affected, and 549 Mha by wind erosion, of which 296 Mha is severely affected. Whereas the effects of erosion on productivity and non-point source pollution are widely recognized, those on the C dynamics and attendant emission of greenhouse gases (GHGs) are not. Despite its global significance, erosion-induced carbon (C) emission into the atmosphere remains misunderstood and an unquantified component of the global carbon budget. Soil erosion is a four-stage process involving detachment, breakdown, transport/redistribution and deposition of sediments. The soil organic carbon (SOC) pool is influenced during all four stages. Being a selective process, erosion preferentially removes the light organic fraction of a low density of <1.8 Mg/m(3). A combination of mineralization and C export by erosion causes a severe depletion of the SOC pool on eroded compared with uneroded or slightly eroded soils. In addition, the SOC redistributed over the landscape or deposited in depressional sites may be prone to mineralization because of breakdown of aggregates leading to exposure of hitherto encapsulated C to microbial processes among other reasons. Depending on the delivery ratio or the fraction of the sediment delivered to the river system, gross erosion by water may be 75 billion Mg, of which 15-20 billion Mg are transported by the rivers into the aquatic ecosystems and eventually into the ocean. The amount of total C displaced by erosion on the earth, assuming a delivery ratio of 10% and SOC content of 2-3%, may be 4.0-6.0 Pg/year. With 20% emission due to mineralization of the displaced C, erosion-induced emission may be 0.8-1.2 Pg C/year on the earth. Thus, soil erosion has a strong impact on the global C cycle and this component must be considered while assessing the global C budget. Adoption of conservation-effective measures may reduce the risks of C emission and sequester C in soil and biota. 相似文献
90.
Soil carbon dynamics in cropland and rangeland 总被引:36,自引:0,他引:36
Lal R 《Environmental pollution (Barking, Essex : 1987)》2002,116(3):353-362
Most soils in the Midwestern USA have lost 30 to 50% of their original pool, or 25 to 40 Mg C/ha, upon conversion from natural to agricultural ecosystems. About 60 to 70% of the C thus depleted can be resequestered through adoption of recommended soil and crop management practices. These practices include conversion from plow till to no till, frequent use of winter cover crops in the rotation cycle, elimination of summer fallow, integrated nutrient management along with liberal use of biosolids and biological nitrogen fixation, precision farming to minimize losses and enhance fertilizer use efficiency, and use of improved varieties with ability to produce large root biomass with high content of lignin and suberin. The gross rate of soil organic carbon (SOC) sequestration ranges from 500 to 800 kg/ha/year in cold and humid regions and 100 to 300 kg/ha/year in dry and warm regions. The rate of SOC sequestration can be measured with procedures that are cost effective and credible at soil pedon level, landscape level, regional or national scale. In addition to SOC, there is also a large potential to sequester soil inorganic carbon (SIC) in arid and semi-arid regions. Soil C sequestration has numerous ancillary benefits. It is truly a win-win situation: extremely cost-effective, and a bridge to the future until alternative energy options take effect. 相似文献