Soil organic carbon (SOC) is an important parameter to study the carbon cycle as soil carbon stock inventory as well as to serve as prime indicator in assessing soil health and soil quality. The present study was attempted to investigate C-equivalent correction factor for SOC by Walkley-Black (wet oxidation) and loss on ignition (LOI) methods in relation to TOC analyzer (dry combustion) method. TOC analyzer method supposed to be the best method of total soil organic carbon estimation. Soil sample from 77 sites representing dominant land use/land cover types of crop land, forest and scrub cover were collected in Himalayan region of Uttarakhand state, India. Surface (0-15 cm) and sub-surface (15-30 cm) soil samples were used for estimation of SOC by these three methods. C-equivalent correction factor ranged from 1.10 to 1.17 for SOC determination by Walkley and Black method to TOC analyzer method, whereas it varied from 0.257 to 0.417 for soil organic matter (SOM) by LOI method to TOC analyzer for soils under various land use/land cover types in the Himalayan region. The recovery of SOC by Walkley-Black method varied from 86.84 to 91.04% in the soils of various land use/land cover in the Himalayan landscape. Thus, there is need to develop specific correction factor for soils under various land use/land cover types for improved estimation of soil carbon stock. The regression models developed in the study can be directly used to obtain TOC analyzer equivalent total carbon contents in the soils (surface and sub-surface) for computation of soil carbon stock in Himalayan region.
Article Info Received : 29.01.2018 Accepted : 18.05.2018 Soil organic carbon (SOC) is a key component in maintaining soil quality. Mapping the local scale variations in the distribution and stratification of SOC and other soil quality parameters across different layers has always been a challenging task, in the current global scenario of changing climates. The study was aimed to investigate the spatial distribution of SOC and other soil quality parameters including SOC stratification ratio and CN ratio in a small hilly watershed (̴ 10 km 2 ) located in the mid Himalayan region of Himachal Pradesh, India. Soil samples were collected in November 2015, from 75 points at two depths (0-15 cm and 15-30cm), along with their geographical coordinates using a Global Positioning System (GPS). The results revealed that SOC concentration (g kg -1 ) decreased with increasing soil depth, throughout the study area and differed significantly (P<0.01) between the two depths in vertical soil profile. The SOC stratification ratio values were greater than 1.2 in major portion of watershed indicating a spatial improvement in soil quality. C: N ratio, another important soil quality attribute values were found to be <12:1, indicating high degree of soil quality and increased rate of organic matter mineralization. The spatial distribution maps of SOC content (g kg -1 ), SOC stratification ratio as well as CN ratio of study area were generated using Inverse Distance Weighted (IDW) interpolation approach. Additionally soil quality index (SQI) was also computed using various soil quality parameters based on Analytical Hierarchy Process (AHP) and their spatial distribution was analyzed in the watershed. Nearly 76% of the study area had SQI values in the range of 60-75, whereas 22.16% of the area had SQI<60 and 2.59% had SQI>75. The overall results indicated that a higher degree of soil quality existed at the higher elevation regions of the watershed. Majority of the soils in the watershed accounted for only 60% of the maximum possible value of SQI, which necessitates the adoption of better management practices for improving the soil quality.
The requirement of lightweight components for interplanetary missions explore the possibilities of the application of composite materials. Carbon Fibre Reinforced polymers (CFRP) are most practical and widely used in space industries. Enhancement of mechanical, thermal, and electrical properties by reinforcing CFRP with Carbon Nanotubes (CNTs) is advantageous, considering the potential applications of such a modified CFRP material in space payload. CNT composites for space use opens new horizons to improve specific stiffness and electrical conductivity of the CFRP components without degrading the performance index. Composite characterization and space qualification are critical and essential, which demonstrate the capability of fulfilling functional as well as specific requirements for space. CNT Composites have to undergo severe environmental tests without degradation. This paper addresses the synthesis of CNT-CFRP composites, its Characterisation and Space Qualification aspects. Synthesis of CNT-CFRP sample with single-walled CNT (Ø1.6µm & L>5µm) 0.5%wt by solution mixing method is attempted. The characterization in terms of measurement of tensile strength, electrical resistivity, shielding effectiveness, thermal conductivity, Co-efficient of thermal expansion (CTE) is carried out. Limited Space qualification on samples and electroplated coupons has been carried out by conducting various environmental tests. The results indicate that CNT reinforced CFRP composites are a promising potential candidate for use in the space domain.
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