Weed species diversity on arable land of the dryland areas of central Tanzania: impacts of continuous application of traditional tillage practices

This paper presents findings from a study that assessed influence of continuous application of a particular traditional tillage practice on weed species richness, diversity and composition and identifies weed species with positive benefits to the communities in semi-arid areas of Mpwapwa district, central Tanzania. In this area farmers apply three different traditional tillage practices which are no-till (NT), shallow tillage (ST) and Ridging System (RT). A total of 36 farm fields were surveyed in 2006/2007 cropping season where 63 weed species from 26 families were identified. Analysis of variance indicated significant differences between practices (p < 0.05), with NT practice having highest weed species richness and diversity. Among the five more prevalent weed species appearing, Bidens lineariloba was observed to exist in all the three practices. Community representatives during focus group discussions indicated 9 weed species out of 63 identified to have beneficial uses. These species are Cleome hirta, Amaranthus graecizans, Bidens lineoriloba, Bidens pilosa, Dactyloctenium aegyptium, Launaea cornuta, Heteropogon contortus, Tragus berteronianus and Trichodesma zeylanicum. Their main uses include leaf-vegetable, medicines, fodder and materials for thatching. From this study NT has highest weed species richness and diversity which therefore suggests that much more time is needed for weeding in this practice compared to other practice which was the farmers’ concern. It was also noted that although weed species have negative effects in crop production and production costs, they still play a vital role in food security and for the health of different people in marginal areas as well as for the complete ecosystem including micro and macrofauna.     

Coupled dynamics of tethered buoy systems

The three-dimensional coupled behavior during the interaction of buoys with their mooring systems is numerically analyzed. A time-domain model was developed to predict the response of a tethered buoy subject to hydrodynamic loadings. External loadings include hydrodynamic forces, tethers tensions, wind loadings and weight. System nonlinearities include large rotational and translational motions, and non-conservative fluid loadings. The mooring problem is formulated as a combined nonlinear initial-value and two-point-boundary-value problem which is directly integrated both in time and space. Buoy equations of motion are derived using small Eulerian angles. Coupling between rotational and translational degrees of freedom is included and coupling between the buoy and cable is effected by adopting the buoy equations of motion as boundary conditions at one end for the mooring problem. Numerical examples are provided to validate the formulation and solution technique; predicted responses of three types of buoy (sphere, spar, and disc) are compared with experimental results.     

Present groundwater status in Egypt and the environmental impacts

This article is an attempt to give a brief review on the status of groundwater studies in Egypt, their results, and the present plans for groundwater development that are usually based on the hydrogeological characteristics of the groundwater resources as well as on the environmental control of the discharge area.In terms of groundwater hydrology, Egypt can be divided into the following groundwater provinces: (1) the Western Desert, (2) the Eastern Desert, (3) the Nile Valley including the delta, (4) the Sinai Peninsula, (5) the Northern Coastal Zone, and (6) Wadi El-Natrun.The studies of volume and nature of groundwater and the environmental impact studies that were carried out in each of these provinces differed according to the importance given to development of projects in areas of interest and to the availability of funds. Recent studies and the surveys conducted for groundwater hydrological research by local and international organizations are described separately for each province. Special reference is made to groundwater hydro-geological setting, groundwater resources evaluation, and present and future utilization. The New Valley is the largest Egyptian irrigated agricultural development project that is solely dependent on groundwater resources. An outline showing its nature, objective, and size is included as an example of groundwater development.     

Engaging indigenous people as geo-crowdsourcing sensors for ecotourism mapping via mobile data collection: a case study of the Royal Belum State Park

ABSTRACT

Web 2.0 and the proliferation of built-in Global Positioning System (GPS) on smartphones have influenced the increase of geo-crowdsourcing activities in a number of different contexts. The aim of this paper is to evaluate the performance of indigenous people’s use of mobile collection applications that are embedded in a smartphone to facilitate ecotourism asset mapping. In order to achieve this, field usability testing was conducted where structured observational method was used to assess the performance. The findings indicate majority of them can complete the data entry tasks using mobile data collection. The performance of data entries using radio button, icons, camera and audio methods were identified as better than free text and drop-down list methods. There was a correlation between the level of education with the ability of using radio button, drop-down list and image icon as data entry methods. The paper also discusses the extent of local knowledge relating to ecotourism within the community. The findings should be useful in the understanding of the design of mobile geo-crowdsourcing tools for use within other contexts that focus on data collection by semiliterate and indigenous groups.     

Large angular motions of tethered surface buoys

A three-dimensional coupled analysis of the interaction of a floating buoy and its mooring is studied. External loads include hydrodynamic forces, tether tensions, wind loads and system weight and buoyancy. Nonlinearities include large rotational and translational motions and non-conservative fluid loads. The mooring problem is formulated as a nonlinear two-point-boundary-value-problem. At each instant in time, the mooring problem is solved by direct integration using a successive iterative algorithm to satisfy boundary conditions. Buoy kinetic and kinematic equations are derived assuming large angles represented by Euler parameters. Coupling between the buoy and the mooring is enforced by matching the velocities of the tether and buoy at the attachment point. A predictor-corrector coupling algorithm is used with multiple sizes of time steps used to provide stability for the separate mooring and buoy models. Numerical results are compared to experimental responses of three types of buoys (sphere, spar and disc) subject to both regular and irregular waves.     

Variation and correlations of selected heavy metals in sediment and aquatic plants in Tasik Chini,Malaysia

This paper aims to determine the correlation between Cd, Cu and Pb concentration in the sediment and in five aquatic plants sampled during wet, normal and dry seasons. Analyses of the sediment showed that concentrations of exchangeable Cd and Cd after acid reduction were higher during the wet season (October) than on other sampling dates with mean values of 0.18 and 0.29 μg g⁻¹, respectively. The concentration of Cu in the organic oxidation phase was higher in the normal season (January) than on other sampling dates with a mean value of 11.1 μg g⁻¹. The concentrations of exchangeable Pb and that in the residual phase were higher during the wet season than on other sampling dates with mean values of 1.05 and 9.18 μg g⁻¹, respectively. Cd and Pb concentrations in the leaves, stems and roots varied between sampling dates with a reduced concentration during dry season (July) and the highest metal concentrations (Cd and Pb) during wet season. There were positive correlations between Cd and Cu concentrations in the plant tissues (leaves, stems and roots) of most aquatic plants in the acid reduction fraction. Conversely, there was no positive correlation between Pb concentration in the plant tissues of all aquatic plants and the acid reduction fraction of the sediment.     

Rapid analysis with energy-dispersive X-ray fluorescence spectrometry for bauxite investigation on the Mambilla Plateau, North Eastern Nigeria

Bauxite exploration involves routine analysis of a large number of samples for a wide range of elements. In Nigeria, though geological field exploration for bauxite started almost three decades ago very little has been achieved, mainly due to the non-availability of facilities for evaluating the dozens of suspected bauxite deposits scattered around the country. In this regard, a procedure for the rapid, accurate and precise measurement of a number of important elements in bauxite has been developed based on the newly acquired radioisotope based EDXRF spectrometer. Elements and oxides analyzed are Al₂O₃, SiO₂, TiO₂, Fe₂O₃, K₂O, Mn, Co, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb and Pb. The richest bauxite sample has concentrations of 48.08, 18.90, 1.26, 7.71 and 1.93 wt% for Al₂O₃, SiO₂, TiO₂, Fe₂O₃, and K₂O, respectively. The other values in ppm are Mn (3 0 2), Co (5 3 2), Cu (45), Zn (51), Ga (41), Rb (32), Sr (2 2 2), Y (32), Zr (8 4 9), Nb (89) and Pb (72). The measurement errors in terms of accuracy and precision are less than 5% and 10% and 5% and 15% for major and trace elements, respectively. Statistical correlation analysis carried out on the results shows the most significant relationships to be the negative correlations of alumina with silica, iron oxide and titanium. This is believed to be related to the processes of formation of bauxite, with the Si and Fe–Ti being removed as Al was being enriched.     

New in situ techniques for the estimation of the dielectric properties and moisture content of soils

Two original in situ HF techniques of dielectric characterization in two wide bands have been developed in order to estimate the moisture content of soils by complex impedance measurement. These techniques are based on the capacitive effect (1–20 MHz) and on the propagation of electromagnetic waves at high frequencies (0.1–4 GHz). The two measurement techniques use straight conductors that are inserted into the soil. Specific inversion algorithms were developed to estimate the apparent real permittivity of the soil versus frequency from the complex impedance. The validation of both instruments was made in the laboratory in the presence of dry and wet sands. In situ experiments were also made at high frequencies. These complementary devices should enlarge the range of usual soil moisture measurement techniques.     

Springs in Egypt

Examples of springs in Egypt deal only with examples of natural springs producing potable water. None of the natural springs producing highly mineralized thermal water for therapeutical are considered. No water from natural springs in Egypt is bottled. Egyptian standards state that the total dissolved solids in potable water should not exceed 1000 ppm, except in Siwa, where the only available source for water for human consumption is from springs that have water containing more than 2000 ppm TDS. Six natural springs in Egypt provide typical examples for the Sinai and the Western Desert: Ain Furtaga in the southern pre-Cambrian province of Sinai Peninsula; Ain El Gudeirat in the sedimentary plateau of North Sinai; and Ain El Bishmo, Ain El Bousa, and Ain El Gabal in the Western Desert Oases of Bahariya, Kharga, and Dakhla. They discharge from the Nubian Sandstone aquifer system. The sixth spring, Ain El Arayes, is a spring in Siwa Oasis.