Accumulation of Heavy Metals in Maga-Pouss Rice Fields (Far-North Region, Cameroon) and Transfer to Rice Grains

Monitoring of heavy metals contamination of agricultural products and their transfer and bioaccumulation in crops like rice has become a hot topic worldwide over the last two decades. The present study was carried out to determine the accumulation of heavy metals in rice fields and their transfer to rice grains. Soil, irrigation water and rice grains samples were gathered in Maga-Pouss, Far-North, Cameroon. Concentrations of six heavy metals (lead, cadmium, zinc, copper, iron and mercury) were evaluated by Atomic Absorption Spectrophotometer (AAS). Mercury was not detected in this study. Average concentrations of metals were in this order (in mg/kg): Fe (188.60 ± 97.06) > Pb (63.63 ± 7.11) > Cd (2.59 ± 0.29) > Zn (1.10 ± 1.05) > Cu (0.80 ± 0.73) in water and Pb (105.50 ± 31.11) > Fe (105.50 ± 31.11) > Cu (45.93 ± 14.39) > Zn (22.52 ± 6.40) > Cd (3.15 ± 0.49) in soil. Water in Maga-Pouss rice fields appears to be more harmful than the soil, notably for lead, cadmium and copper. In rice grains, heavy metals were found in this order (mg/kg): Fe (188.01 ± 82.62) > Cu (27.20 ± 0.00) > Zn (23.61 ± 12.42) > Pb (19.50 ± 19.91) > Cd (2.02 ± 1.05). The mean bioconcentration factor (BCF) of metals from soil to rice grains was in the following order: Fe (2.60) > Zn (1.05) > Cd (0.64) > Cu (0.59) > Pb (0.18). From water to rice grains, the order is: Cu (37.26) > Zn (22.49) > Cd (6.97) > Pb (2.74) > Fe (1.94). Rice field pH and electrical conductivity favored the uptake of lead, copper and cadmium by rice grains. The findings of this study will be good documentation for risk assessment, and decision-making by environmental managers in this region.

Comparison of Spatial Interpolation Methods of Precipitation Data in Central Macedonia, Greece

The purpose of this paper is to investigate the spatial interpolation of rainfall variability with deterministic and geostatic inspections in the Prefecture of Kilkis (Greece). The precipitation data where recorded from 12 meteorological stations in the Prefecture of Kilkis for 36 hydrological years (1973-2008). The cumulative monthly values of rainfall were studied on an annual and seasonal basis as well as during the arid-dry season. In the deterministic tests, the I.D.W. and R.B.F. checks were inspected, while in the geostatic tests, Ordinary Kriging and Universal Kriging respectively. The selection of the optimum method was made based on the least Root Mean Square Error (R.M.S.E.), as well as on the Mean Error (M.E.), as assessed by the cross validation analysis. The geostatical Kriging also considered the impact of isotropy and anisotropy across all time periods of data collection. Moreover, for Universal Kriging, the study explored spherical, exponential and Gaussian models in various combinations. Geostatistical techniques consistently demonstrated greater reliability than deterministic techniques across all time periods of data collection. Specifically, during the annual period, anisotropy was the prevailing characteristic in geostatistical techniques. Moreover, the results for the irrigation and seasonal periods were generally comparable, with few exceptions where isotropic methods yielded lower (R.M.S.E.) in some seasonal observations.

Contribution of GIS to Hydromorphometric Characterization of the Nkoup Watershed(Nun Plain-Cameroon)

The Nkoup watershed(10°35’-10°47’E and 5°27’-5°42’N)is a volcanic zone situated in Nun Plain West Came­roon.The high fertility of the soils makes it a strategic agropastoral area where water resources are heavily exploited and used for several purposes.Due to human activities,soils and water resources are deteriorating,giving birth to wa­ter pollution and hydromorphological hazards.This work aims to determine the hydromorphometric parameters of the Nkoup watershed so that the data obtained help in the sustainable management of water resources and conservation of soil.To achieve this aim,various data were collected from DEM dataset derived from SRTM and processed in specia­lized software(QGIS and ArGIS).The simplified hydrological balance was calculated using the upstream approach.The Nkoup watershed has:Axial length L_(ax)=25.8 km,Axial Width W_(ax)=11.1 km,Perimeter P=132.6 km,Area A=173.7 km^(2),Average Altitude Ha=1726.3 m,Compactness Index Icomp=2.8,Relief ratio Rr=3.9 m/km,Circularity ratio Rc=0.1,Elongation ratio R=0.1,Drainage texture ratio Rt=0.6,Drainage density Dd=0.5 km/km^(2).Stream Frequency Fs=0.4,Channel Sinuosity Index CSI=0.8,Stream gradient Sg=0.6 and global slope Index Ig=6.8 m/km.The specific height Difference Ds=89.4 m shows moderate relief.The precipitation and evapotranspiration are unevenly distributed.With P=187.7 mm/an,ETP=953.4 mm/an,Q=4.2 m3/s,R=762.5 mm/an,ETR=832.3 mm/an and I=282.9 mm/an.The Nkoup,36.9 km long,has a sinuous aspect due to the low slope and the high CSI.The piezometric levels vary according to the seasons and the groundwater flow follows the N-S direction as surface flow.

Meshless Method for Analysis of Permeable Breakwaters in the Proximity of A Vertical Wall

In the present work, the improved version of the meshless singular boundary method(ISBM) is developed for analyzing the performance of bottom standing submerged permeable breakwaters in regular normally incident waves and in the proximity of a vertical wall. Both single and dual prismatic breakwaters of rectangular and trapezoidal forms are examined. The physical problem is cast in terms of the Laplace equation governing an irrotational flow and incompressible fluid motion with appropriate mixed type boundary conditions, and solved numerically using the ISBM. To model the permeability of the breakwaters fully absorbing boundary conditions are assumed. Numerical results are presented in terms of hydrodynamic quantities of the reflection coefficients. These are firstly validated against the results of a multi-domain boundary element method(BEM) developed independently for a previous study. The agreement between the results of the two methods is excellent. The coefficients of reflection are then computed and discussed for a variety of structural conditions including the breakwaters height, width, spacing, and absorbing permeability. Effects of the proximity of the vertical plane wall are also investigated. The breakwater's width is found to have only marginal effects compared with its height. Permeability tends to decrease the minimum reflections. These coefficients show periodic variations with the spacing relative to the wavelength. Trapezoidal breakwaters are found to be more cost-effective than the rectangular breakwaters. Dual breakwater systems are confirmed to perform much better than single structures.

Gravel Accumulation in Deposits of Viscous Debris Flows with Hyper-concentration

According to the observational data of viscous debris flows with hyper-concentration, debris flows can be classified into three types:high-viscous, viscous, and sub-viscous debris flows.Distinct formation mechanism of different graded bedding structures in deposits of viscous debris flows was analyzed in this paper by using their yield-stress ratio and flow plug ratio.This paper specially analyzed the effect of Weissenberg which the gravels in squirm condition of hyper-concentration viscous flows would tend to move vertically, and the formation mechanism of the gravels accumulated at surface was also studied.The analysis in this paper can establish a foundation for the studies on differentiation of bedding structures of debris flow deposits and studies on dynamic parameters of debris flows.

Development and Validation of Two Methods to Quantify Volatile Acids (C2-C6) by GC/FID: Headspace (Automatic and Manual) and Liquid-Liquid Extraction (LLE)

The concentration of the volatile fatty acids (VFA) is an important indicator of the status of an-aerobic processes, but most of the existing methods require sample pretreatment and are labor-intensive. It was developed and validated a rapid Gas Chromatographic (GC) method to quantify seven VFA (acetic, propionic, isobutyric, butyric, isovaleric, valeric and caproic), acetone, methanol, ethanol and n-butanol by headspace (automatic and manual) and liquid-liquid extraction (LLE) with diethyl ether (only VFA). The determination was made in a Shimadzu Gas Chromatograph equipped with a Flame Ionization Detector (GC/FID), a headspace auto-sampler and an HP-INNOWAX column. Isobutanol and crotonic acid were utilized as internal standards (IS). The validation parameters evaluated were: precision (coefficient of variation—C.V.% for the retention times, from 0.02 to 0.87), linearity (R2 = 0.9291 - 0.9997), limits of detection (from 3.97 to 36.45 mg·L﹣1) and instrumental precision (from 0.01 to 0.53), which provide evidence that the methods are adequate to determine these analytes in samples from anaerobic reactors and from the environment.

Performance Evaluation of Bottom-Standing Submerged Breakwaters in Regular Waves Using the Meshless Singular Boundary Method

In this paper, the improved version of the meshless singular boundary method (ISBM) is developed for analyzing the hydrodynamic performance of bottom-standing submerged breakwaters in regular normally incident waves. Both the single and dual prismatic breakwaters of rectangular and trapezoidal forms are examined. Only the impermeable breakwaters are considered in this study. The physical problem is cast in terms of the Laplace equation governing an irrotational flow and incompressible fluid motion with the appropriate mixed-type boundary conditions, and it is solved numerically using the ISBM. The numerical results are presented in terms of the hydrodynamic quantities of reflection and transmission coefficients. The values are first validated against the data of previous studies, computed, and discussed for a variety of structural conditions, including the height, width, and spacing of breakwater submergence. An excellent agreement is observed between the ISBM results and those of other methods. The breakwater width is found to feature marginal effects compared with the height. The present method is shown to accurately predict the resonant conditions at which the maximum reflection and transmission occur. The trapezoidal breakwaters are found to generally present a wide spectrum of reflections, suggesting that they would function better than the rectangular breakwaters. The dual breakwater systems are confirmed to perform much better than single structures.

Characterization and Modification of a Clay Mineral Used in Adsorption Tests

Clay minerals are widespread in natural systems and have been widely used for the removal of pollutants. In this study, natural expanded vermiculite was used in adsorption tests to remove ammonium nitrogen from landfill leachate. The modification of vermiculite was carried out using NaOH and HCl, and for both modifications the best concentration was 0.1 mol/L. The results produced by XRD (X-ray diffraction) showed that Al replaced K after modification of the vermiculite using HCl and that Mg and Na replaced K after modification using NaOH. It was observed that the adsorption capacity increased as the percentage in mass of K diminished. The Langmuir is the isotherm that presents the best fit of the data, and the values of RL (the Langmuir coefficient) suggest that the adsorption is linear. The thermodynamic parameters indicate that the process is spontaneous and endothermic, that there is a high affinity between the adsorbate and the adsorbent, and that physical adsorption is prevalent.

Evaluation of pan coefficient equations in a semi-arid Mediterranean environment using the ASCE-standardized Penman-Monteith method

Reference crop evapotranspiration (ETo) is essential for irrigation, water resources management and environmental assessment. The indirect estimation of ETo is based a) on energy budget approach using meteorological data and b) pan evaporation measurements (Epan) multiplied by pan coefficients (kp) adapted to the surrounding environmental conditions. Significant interest is shown for the kp equations, which have to be tested before their use. The purpose of this study is to evaluate six different kp equations, such as those of Cuenca, Allen and Puitt, Snyder, Pereira et al., Orang, Raghuwanshi and Wallender for the summer growing season (April to October) of Thessaloniki plain in Greece, which is characterized by a semi-arid Mediterranean environment. The evaluation of the kp equations is performed by two years Epan measurements, using as reference the daily ETo values estimated by the ASCE-standardized Penman-Monteith equation (ASCE-PM) in hourly time step. The results of this study showed that Cuenca’s equation provided more accurate daily estimations. Additional analysis is performed in other methods such as those of FAO-56 and Hargreaves based on the calculation time step (hourly or daily) and their correspondence to the ASCE-PM.

Experimental Study of Sand Bed Configurations in Front of a Vertical Wall Under Wave Action

When a 2-D progressive wave train normally or obliquely approaches a vertical wall and then is normally or obliquely reflected from it, the combination of the approaching and reflected waves may result in a standing wave or a short-crested wave in front of the wall. This paper presents the experimental observations of sand bed configurations under the action of these water waves in front of the wall. The geometry of sand ripples under these water waves in front of the vertical wall is presented as a function of flow parameters, such as the water particle semi-excursion and the mobility number.

Numerical Simulation of TWo Different Flexible Bodies Immersed in Moving Flow

The coupled motion of two flexible bodies with different lengths immersed in moving fluid is studied numerically. The flapping frequency, flapping amplitude and average drag coefficient of each body are calculated and the influences of the arranging manner and separation distance are analyzed. In our simulation, when placed in the flow individually, the flexible body with a longer length will flap in period and the shorter one will maintain still straightly in the flow direction. The numerical results show that, two different flexible structures near placed in moving flow would strongly interact. When they are placed side by side, the existence of the stable shorter flexible body will restrain the flapping of the longer one while the existence of the longer flexible body may also induce the shorter one to flap synchronously. When placed in tandem with the shorter flexible body in upstream, the flapping of the longer one in downstream will be obviously enhanced. In the situation for the longer flexible body placed in upstream of the shorter one, the coupled flapping amplitude and average drag coefficients increase and decrease periodically with increasing the arranging space, and peak values appear as a result of the mediate of the tail wakes.

Rainfall patterns of Algerian steppes and the impacts on natural vegetation in the 20^th century

Since 1960, the steppe regions of North Africa have been subject to an increasing desertification, including the degradation of traditional pastures. The initially dominant species （Artemisia herba-alba, Lygeum spartum and Slipa tenacissima） declined and were progressively replaced by other species （Atractylis serratuloides and Salsola vermiculata） that are more tolerant to the new conditions. It is not clear whether these changes are due to anthropogenic reasons or climatic determinism. We have carried out a statistical analysis of the climate to detect putative rainfall changes during the 20th century in the Algerian steppes based on data from 9 meteorological stations, including 2 Saharan stations （El Oued and Touggourt）, 3 pre-Saharan stations （Biskra, Laghouat and Ain Sefra） and 4 steppe stations （Djelfa, Saida, M6ch6ria and E1-Bayadh） located in the arid high plains, which represent the bioclimate diversities of the region. Previous studies suggested that significant rainfall changes for the 20th century only had records in the south of the Oran region. Most of the studies, however, looked at restricted territories over limited periods, and did not integrate the rainiest period 2004-2014. Our work is designed to integrate all the longest time series of meteorological data available for the steppe regions of Algeria. Our results confirm the spatial rainfall distribution （significant rainfall changes only recorded in the southwestern region） evidenced by previous studies, and reveal a decreasing rainfall gradient from northeastern to southwestern Algeria. Moreover, the results reveal a trend of significant decrease of rainfall in the southern Oran region, marked by two drought periods in 1980- 1985 and 1999-2003. However, with the exception of the southwestern region, rainfall overall has not declined since the beginning of the 20th century. While less marked in other regions, the drought appear to have affected all territories of the Algerian steppe. Consequently, our study implies that the climate was not a leading influence in the on-going degradation of the vegetation cover of steppe landscapes. Such a vegetation evolution thus appears to be have been determined more by human activities than by climate forcing.

Feeding Strategies for Enrichment and Characterization of Anammox Biomass in a Sequencing Batch Reactor

Anammox bacteria represent a promising alternative for treating ammonium-rich wastewater. In this work reported, biomass performing anaerobic oxidation of ammonium was enriched in a sequencing batch reactor, from sludge used for the treatment of high-nitrogen waste from an amino acid-producing industry. After 89 days of operation, both ammonium and nitrite were consumed. During operation under a 24-hour cycle, the applied nitrogen load (ANL) was increased from 155 to 802 mg N/L·d. This strategy resulted in efficiencies of nitrogen removal and nitrogen conversion rate of 91.7% and 98.5%, respectively. Specific anammox activity increased proportionally to ANL and it was partially inhibited at 802 mg N/L·d. Sequencing analysis using 16S rRNA anammox primers, after 170 days of operation, showed that 21 clones were grouped into two OTUs (operational taxonomic units). The identity of the 16S rRNA gene of OTU esp 1 showed similarity to Brocadia species, and OTU esp 2 displayed 99% similarity to Anammoxoglobus propionicus. After 450 days of operation, sequencing analysis using universal primers showed that 48 clones were grouped into 19 OTUs representing six major groups of bacteria: Planctomycetes, beta-Proteobacteria, green sulfur bacteria of the Chlorobi phylum, Nitrospira, Chloroflexi and OP 11. Brocadia sp. was the only anammox bacteria in the biomass at this time.

Site and Regional Trend Analysis of Precipitation in Central Macedonia, Greece

The purpose of this paper is to investigate the trend of precipitation in Kilkis region (Greece) at the site and regional level in various time scales. At the site level, the precipitation trend was analyzed using three tests: 1) Mann-Kendall, 2) Sen’s T and 3) Spearman while the trend slope was estimated using the Sen’s estimator. At a regional level, nonparametric spatial tests such as Regional Average Mann-Kendall (RAMK) and BECD’s (Bootstrap Empirical Cumulative Distributions) were elaborated with and without the effect of cross correlation. The trend of precipitation was noticed generally downward at annual time scale and statistically significant at 5% level of significance only in only one station. The results of the analysis of trends at the regional level showed in total the influence of cross correlation in the time series since the number of trends detected is reduced when cross correlation is preserved. Precipitation data from 12 stations were used. The study results benefit water resource management, drought mitigation, socio-economic development, and sustainable agricultural planning in the region.

Trends and Geostatistical Interpolation of Spatio-Temporal Variability of Precipitation in Northern Cameroon

This paper examines the spatial and temporal variability of the mean annual precipitation in the Northern Cameroon on the context of climate change during the time period 1950-2013. The study used homogeneous monthly and annual precipitations database of twenty-five stations located in the Northern Cameroon and Southern Chad Republic. Geostatisticals interpolation methods (Kriging and Inverse Distance Weighting method) associated with Digital Elevation Model were used to establish the spatial distribution of annuals precipitations. The non-parametric Mann- Kendall test and Sen’s slope method were performed to determine respectively trend and magnitude. The result indicates a spatial distribution of precipitation mainly determined by the topography and the geography of the study area. The trend analysis shows a decrease of annual average precipitation across the Northern Cameroon at a rate of ?0.568 mm/year over the time period 1950-2013. The magnitude of decreasing trends ranged between 0.11 and 3.92 mm/year. Statistically significant decreasing trends at the 95% level of confidence were noted at 10% while 5% of stations showed statistically significant increasing. However, 60% of stations indicate a decreasing trend. Monthly analysis of rainfall shows a decreasing trend during June and September while July and August present an increasing trend.

Estimation of Hydraulic Conductivity of Soils at a Watershed-Scale Using Porchet’s Method: Application in the Olezoa Waterhed, Yaounde, Cameroon

Contamination analysis of the unsaturated zone requires information on the spatial variability of hydraulic conductivity. Two types of hydraulic tests (variable and constant charge) were identified to estimate the spatial variability of the hydraulic conductivity of the surface portion of the unsaturated zone in the Olezoa watershed. These tests were performed on 100 holes at depths ranging between 50 and 90 cm, spread throughout the watershed. The hydraulic conductivity values obtained at 50 and 90 cm are close to the absolute value for each method. However, they show a difference of 10-1 m/s between the two types of test regardless of the depth of investigation. The representation of data in the graph indicates a staircase quartile distribution for the variable charge test. The test at constant charge, rather presents a log normal distribution which is also supported by the Kolmogorov-Smirnov test. Hydraulic conductivities have a random component and a spatial organization which results from soil and/or morphological factors. This organization thus permits the distinction of zones which could show high pollution risk.

Comparisons between unsteady sediment-transport modeling

The comparative study between unsteady flow models in alluvial streams shows a chaotic residue as for the choices of a forecasting model. The difficulty resides in the choice of the expressions of friction resistance and sediment transport. Three types of mathematical models were selected. Models of type one and two are fairly general, but require a considerable number of boundary conditions, which related to each size range of sediments. It can be a handicap during rivers studies which are not very well followed in terms of experimental measurements. Also, the use of complex models is not always founded. But then, the model of type three requires a limited number of boundary conditions and solves only a system of three equations at each time step. It allows a considerable saving in calculating times.

On Radiation Boundary Conditions and Wave Transformation Across the Surf Zone

The purpose of this paper is to extend the validity of Li's parabolic model (1994) by incorporating a combined energy factor in the mild-slope equation and by improving the traditional radiation boundary conditions. With wave breaking and energy dissipation expressed in a direct form in the equation, the proposed model could provide an efficient numerical scheme and accurate predictions of wave transformation across the surf zone. The radiation boundary conditions are iterated in the model without use of approximations. The numerical predictions for wave height distributions across the surf zone are compared with experimental data over typical beach profiles. In addition, tests of waves scattering around a circular pile show that the proposed model could also provide reasonable improvement on the radiation boundary conditions for large incident angles of waves.