Determination of heavy metals (Cd, Cr, Cu, Fe, Ni, Pb, Zn) by ICP-OES and their speciation in Algerian Mediterranean Sea sediments after a five-stage sequential extraction procedure

Surface sediment samples (n = 18) were collected from the Algerian Mediterranean coasts and analyzed for seven metals using inductively coupled plasma-optical emission spectrometry in order to asses the distribution and bioavailability of metals and to study the anthropogenic factors affecting their concentrations. Sediment samples were size-fractionated into three sizes: 1,080–500 (coarse), 500–250 (medium), and <250 mm (fine). Bulk sediments were subjected to both sequential extraction and total digestion to evaluate the reliability of the sequential extraction procedure (SEP), while the fractions have been only sequentially extracted for metals speciation. The metals were sequentially extracted into five phases namely exchangeable (P1), carbonates (P2), Fe–Mn oxides (P3), organic (P4) and residual (P5). Metal recoveries in sequential extractions were ±20% of the independently measured total metal concentrations; the high recovery rates indicate the good reliability of the SEP used in this study. Correlation coefficients indicated that the grain size has an effect on the distribution of metals in the investigated samples. The order of metal levels in the fractions was medium > fine > coarse for all the metals. The average total extractable metal concentrations for Cd, Cr, Cu, Fe, Ni, Pb, and Zn were 1.1, 8.8, 4.7, 1,291.3, 13.9, 5.7 and 20.4 μg/g, respectively. The northeastern shelf had the lowest metal levels while the highest were in northwestern part mainly due to the significant tourism activities in the northwestern part. Comparison of our results to Earth’s crust values and to previous studies points out that our samples were relatively unpolluted with respect to the heavy metals investigated; most of the metals are not from anthropogenic sources. Enrichment factors as the criteria for examining the impact of the anthropogenic sources of heavy metals were calculated, and it was observed that the investigated samples were not contaminated with Cr, Cu, and Fe, moderately contaminated with Ni, Pb, and Cd, and contaminated with Cd in some sites. The P5 phase had the highest percents of Cr, Cu, Fe, Ni, and Zn. Cadmium and lead were predominant in the P4 phase, while Cu, Fe and Zn were distributed in the order P5 > P3 > P4 > P2 > P1. The following order of bioavailability was found with the heavy metals Pb > Cr > Cd > Ni > Zn > Cu > Fe.     

CFD analysis on the performance of a solar chimney power plant system: Case study in Algeria

The solar chimney power plant (SCPP) is a power generator which uses solar radiation to increase the internal energy of the air circulating in the system, thereby transforming the useful gain of the solar collector into kinetic energy. The produced kinetic energy then can be converted into electrical energy by means of an appropriate turbine. In this paper, four locations in Algeria

(Constantine, Ouargla, Adrar, and Tamanrasset) were considered as case studies to describe the SCPP mechanism in detail. Numerical simulation of an SCPP which has the same geometrical dimensions was performed to estimate the power output of SCPP in these regions. Using the CFD software FLUENT we simulated a two-dimensional axisymmetric model of a SCPP with the standard k-ε turbulence model. The simulation results show that the highest power output produced monthly average value 68–73 KW over the year and the highest hourly power produced in June is around 109–113 KW.     

Nexus between renewable energy consumption,economic growth,and CO2 emissions in Algeria: New evidence from the Fourier-Bootstrap ARDL approach

Governments often impose new energy strategies to support new CO₂ emission-reducing technologies without affecting economic growth. Hence, this study aims to re-investigate the relationship between economic growth, renewable energy use, and CO₂ emissions in Algeria from 1990 to 2018. Motivated by the mixed findings of the existing literature, which ignore the Fourier function and bootstrap test and apply the newly developed Fourier bootstrap autoregressive distributed lag model (FARDL). Our findings indicate that renewable energy use and growth have a long-run relationship with CO₂ emissions and do not accept the existence of the Environmental Kuznets Curve (EKC) hypothesis for CO₂ emissions in Algeria. In the long term, the results show that renewable energy use has a negative and significant impact, and growth has a positive and statistically significant effect on CO₂ emissions. In the short run, the findings indicate that renewable energy use reduces CO₂ emissions, while both the growth and squared growth had positive and statistically insignificant impacts on CO₂ emissions, confirming the lack of evidence supporting the EKC hypothesis. Moreover, the causality test indicates a one-way causation from growth to renewable energy use, confirming the conservation hypothesis for Algeria and from growth to CO₂ emissions. Interestingly, we found one-way causality from CO₂ emissions to renewable energy use, attributing this to the fact that renewable energy usage has yet to reach a point that it can significantly cause a CO₂ emissions reduction. Based on the results, we recommend that policymakers design appropriate policies to decarbonize energy consumption, e.g., increasing fossil fuel costs and implementing a carbon tax. In contrast, Algeria should promote new CO₂ emission-reducing technologies without affecting economic growth, e.g., tax exemptions and reductions for enterprise owners in the renewable energy industry.