The study aims to get insight about the depth wise distribution of fractions of cationic micronutrients (Fe, Mn, Zn and Cu) and their availability across various landscape positions in an elevational gradient of Meghalaya.Soils were collected from four different soil depth viz. 0-15, 15-30, 30-45 and 45-60 cm representing major landscape positions, i.e., plateau top, side slope, foot slope and valley in a catenary sequence in the Umsning block of Ri-bhoi district, Meghalaya.Cationic micronutrients and their fractions varied with soil depth and landscape positions in the study area. DTPA extractable Fe, Mn, Zn and Cu content was higher in surface layer as compared to the sub surface and found in higher amount in valley as compared to the other landscape positions. Zinc is the most limiting cationic micronutrient found in the study area, whereas poor availability of Mn was also observed in few sub-surface samples. Residual fraction was the largest fraction of cationic micronutrients in soil and varied from 58.4 to 71.0, 33.8 to 64.9, 66.0 to 84.1 and 30.1 to 65.6% of total Fe, Mn, Zn and Cu, respectively in the study area. Soluble and exchangeable fraction is the most labile pool of cationic micronutrients in the study area though its content was less. Organically complexed fraction contributed in large to the availability of Fe, Zn and Cu. Whereas, amorphous and crystalline Fe oxide occluded fractions of Zn and Cu and crystalline oxide occluded fractions of Mn were also found to contribute the availability of respective cationic micronutrients as an indirect source.Landscape position influences the distribution and availability of cationic micronutrients and their fractions in undulating terrain of Meghalaya through the distribution of clay, organic carbon and water content in soil profile. Moreover, present land use further modifies the availability of cationic micronutrients in the study area.Catenary sequence, Depth-wise distribution, Meghalaya, Micronutrient fraction. Vertical distribution of cationic micronutrients across landscape positions on Meghalayan plateau in the North-Eastern Region of India
The Public Utilities Board (PUB) of Singapore is currently progressing Phase 2 of the Deep Tunnel Sewage System (DTSS) project. Leighton Contractors Asia Limited (LCAL) have been awarded Contract T-09 of the project which runs approximately 8 km from the intersection of Clementi Road and the Ayer Rajah Expressway (AYE) to the intersection at Jurong Pier Road and AYE. LCAL have appointed COWI to act as their designer. Contract T-09 includes eight shafts, including Shaft O1 located between the Jurong River to the west and Penjuru Road to the east in the Jurong region of south-west Singapore. This paper discusses the rock engineering aspects of Shaft O1, including the engineering geological aspects and the methods of analysis used to design the reinforcement and support of the section of the shaft excavated in rock. Finally, the conditions encountered and the support installed during the engineering geological mapping of the shaft are described. The geology at Shaft O1 comprises made ground overlying Kallang Formation deposits and then weathered rocks of the Jurong Formation. Development of the ground model included several stages of desk study and ground investigation and ultimately six boreholes and eight probeholes were carried out at and around the shaft location. The analysis methods used included the Q-system, analytical closed-form calculations, use of the Unwedge software package, rock bolt and sprayed concrete design and a stand-up time assessment. The design was prepared during 2018-19 and the shaft was successfully constructed during 2019.
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