Residual impact of biochar on cadmium uptake by rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.) grown in Cd-contaminated soil

Cadmium (Cd) is the family member of toxic heavy metals, and its accumulation in food crops has become a global environmental constraint. Biochar potentially minimizes the metal contents in plants, but limited work has been reported on its residual effect on subsequent crops. The residual effect of various biochar levels (0, 1.5, 3.0, and 5.0% w/w) on Cd accumulation in rice has been investigated in this study. Biochar treatments enhanced the rice growth, photosynthesis, and antioxidant enzymes, whereas diminished the Cd contents and oxidative stress in rice. Cadmium concentration in shoots decreased by 24.4, 36.6, and 57.5% in 1.5, 3.0, and 5.0% biochar treatments over the control. Biochar supply enhanced the soil pH and electrical conductivity, whereas diminished the soil bioavailable Cd. Overall, the results depicted a significant residual impact of rice straw biochar on rice growth attributes and Cd uptake. However, studies are still needed to explore the long-term sustainability of biochars prepared from different feedstocks on bioavailability of toxic metals in soils and uptake by food crops under field conditions.     

Addition of Phosphorus and Nitrogen Support the Invasiveness of Alternanthera Philoxeroides Under Water Stress

Coordination of plant functional traits with changes in the environment is helpful to understand the mechanisms underlying both invasiveness and adaptation of plants. Thus, to investigate the performance and functional traits in invasive Alternanthera philoxeroides (Mart.), an experiment of water stress is conducted with different nutrient concentrations. Alternanthera philoxeroides plants are grown under natural and nutrient soils and subjected to three levels of nitrogen (N) and phosphorus (P) solution: ambient P and N concentration (P?N?), P addition with an ambient N concentration (P+N?), and P addition with high N concentration (P+N+) in combination with three different irrigation water levels as 1) 100% irrigation, 2) 50% irrigation, and 3) 25% deficit irrigation. Based on results, A. philoxeroides produces significantly higher biomass in both soils under 100% irrigation with P+N? treatment and exhibits higher values of leaf area and root length. However, 25% irrigation with P?N? treatment in both soils exerts a significant negative effect on relative growth rate and root/shoot ratio of A. philoxeroides plants. Under 50% irrigation in soils with both P+N? and P+N+ treatments, high values of leaf nitrogen are recorded. Moreover, nutrient soil is more supportive to A. philoxeroides than natural soil.     

Seismic settlement of a strip foundation resting on a dry sand

Natural Hazards - Seismic settlement of shallow foundations constructed in seismic active areas should be considered for a reasonable estimation of the total settlement. However, the trend of the...     

Nagmati River Sub-watershed Prioritization Using PCA,Integrated PCWS,and AHP: A Case Study

Prioritization of potential regions that are severely threatened by soil erosion is a prerequisite for formulating and implementing conservation measures and management practices, particularly in fragile semiarid regions. The present study prioritized eight delineated Nagmati sub-watersheds located in the Kutch District of Gujarat State, India, based on three approaches, namely principal component analysis (PCA), integrated PCA with weighted sum (I-PCWS), and analytical hierarchy process (AHP), and on 10 morphometric erosion risk parameters (ERPs). Sub-watersheds were categorized into three priority classes, namely high, medium, and low. PCA retrieved the three most significant ERPs (i.e., length of overland flow, Lo; drainage texture, Dt; and compactness coefficient, Cc) explaining 86.876% of the variance and exhibiting the highest correlation, i.e., r?=?0.961, 0.986, and 0.934 for the first three principal components. Sub-watersheds SW2 and SW7 were rated high priority, SW1 was rated low priority, and the rest were rated medium priority. The I-PCWS approach revealed that sub-watersheds SW2, SW6, and SW7 were in high-priority zone, followed by SW3, SW4, and SW8 in medium-priority zone and SW1 and SW5 in the low-priority zone. The AHP assigned the highest and lowest ranks to “Lo” and “Cc,” respectively, with consistency ratio of 8.1% and principal eigenvalue of 11.075. Results from AHP revealed sub-watershed SW2 to be the highest priority and sub-watersheds SW1 and SW5 to be the lowest priority. Out of eight prioritized sub-watersheds from three approaches, five were found to be the common priority classes, with SW2, SW6, and SW7 demanding urgent implementation of efficient soil conservation measures to prevent further degradation of the identified regions. Results from I-PCWS approach closely complied with the existing landforms within the study area, and this approach was considered more reliable and robust than the other two approaches. The methodology adopted in this study can be applied to different vulnerable, data-scarce regions to sustainably manage and conserve soil erosion through efficiently framed strategies.

     

Effect of turbulence modelling on the computation of the near-wake flow of a circular cylinder

An evaluation of four well-known Reynolds-Averaged Navier-Stokes (RANS)-based turbulence models was performed in comparison with the results of a dedicated experimental measurement on the near-wake of a circular cylinder in a large water (cavitation) tunnel using a state-of-the-art two-dimensional Digital Particle Image Velocimetry (DPIV) device.The turbulence models investigated were Spalart-Allmaras (S-A), Realizable k-ε (RKE), Wilcox k-ω (WKO) and Shear-Stress-Transport k-ω (SST), which were assessed based on their comparative performances in predicting some important flow field characteristics of the near-wake region of the experimental circular cylinder flow. Within the flow range investigated in this study, which implied a cylinder diameter-based Reynolds Number of 41,300, the qualitative and quantitative comparisons revealed that the application of the SST model to the wall-bounded unsteady flow - that experienced severe adverse pressure gradient, massive flow separation and vortex shedding - presents more successful predictions compared to other models investigated for such challenging flow conditions.     

Teaching GIS in the Gulf Co-operation Council Universities – With a case study of the geography department, University of the United Arab Emirates

Within universities there has developed a clear theoretical convergence between Geographical Information Systems (GIS) and geography (Antenuccl, 1991). Studies have revealed that one of the qualified departments to teach GIS within universities is the geography department. This study focuses on: the importance of establishing GIS as a major curriculum element within universities. In geography departments, economic geography students require a strong statistical/mathematical background to allow them to work with major databases. They should know how to design a specific database for economic activities, such as agriculture and manufacturing, and tertiary industry and how to relate this database to a map, so that changes can be monitored more accurately. In any aspect of geography spatial location is a key factor and GIS allows spatial patterns to be interpreted with great facility. Therefore it is important that students have a good knowledge not only of computers and related software on economic geography, but also on GIS systems (Burrough, 1993). The work of geography students from the United Arab Emirates (UAE) and other Gulf Co-operation Council (GCC) geography departments is examined to evaluate the importance of training in GIS technology. This paper evaluates the effects of implementing GIS as a tool in teaching economic geography. At present there are 15 geography departments in the GCC which offer economic geography. Of those 15 departments, only 3 provide GIS courses within their curriculum, and 4 have basic equipment, although 6 additional departments are to introduce GIS in the near future. This revised version was published online in July 2006 with corrections to the Cover Date.     

Depositional Environment and Lithofacies Analyses of Eocene Lacustrine Shale in the Bohai Bay Basin: Insights from Mineralogy and Elemental Geochemistry

The effect of various depositional parameters including paleoclimate, paleosalinity and provenance, on the depositional mechanism of lacustrine shale is very important in reconstructing the depositional environment. The classification of shale lithofacies and the interpretation of shale depositional environment are key features used in shale oil and gas exploration and development activity. The lower 3^rd member of the Eocene Shahejie Formation(Es₃^x shale) was sel...     

Transport and exchange of U-series nuclides between suspended material,dissolved load and colloids in rivers draining basaltic terrains

This study presents uranium and thorium concentrations and activity ratios for all riverine phases (bedload, suspended load, dissolved load and colloids) from basaltic terrains in Iceland and the Azores. Small basaltic islands, such as these, are thought to account for ~ 25% of CO₂ consumed by global silicate weathering, and for ~ 45% of the flux of suspended material to the oceans. These data indicate that [U] and [Th] in the dissolved and colloidal fractions are strongly controlled by pH, and to a much lesser extent by levels of dissolved organic carbon (which are low in these environments). At high pH, basalt glass dissolution is enhanced, and secondary mineral formation (e.g. Fe-oxyhydroxides and allophane) is suppressed, resulting in high dissolved [U], and low colloidal [U] and [Th], indicating a direct chemical weathering control on elemental abundances. When the dissolved (²³⁴U/²³⁸U) activity ratio is >~1.3 (i.e. when physical weathering, groundwater contribution or soil formation are high), there is little isotope exchange between dissolved and colloidal fractions. At lower activity ratios, the dissolved load and colloids have indistinguishable activity ratios, suggesting that when chemical weathering rates are high, secondary clay formation is also high, and colloids rapidly adsorb dissolved U. Many of the suspended sediment samples have (²³⁴U/²³⁸U) activity ratios of > 1, which suggests that uptake of U onto the suspended load is important. Identical (²³⁰Th/²³²Th) in suspended, dissolved and colloidal samples suggests that Th, like U, is exchanged or sorbed rapidly between all riverine phases. This particle-reactivity, combined with poorly constrained contributions from groundwater and hydrothermal water, and short-term variations in input to soils (volcanic and glacial), suggests that U-series nuclides in riverine material from such basaltic terrains are unlikely to reflect steady state erosion processes.