Review of ozone and temperature lidar validations performed within the framework of the Network for the Detection of Stratospheric Change

The use of assimilation tools for satellite validation requires true estimates of the accuracy of the reference data. Since its inception, the Network for Detection of Stratospheric Change (NDSC) has provided systematic lidar measurements of ozone and temperature at several places around the world that are well adapted for satellite validations. Regular exercises have been organised to ensure the data quality at each individual site. These exercises can be separated into three categories: large scale intercomparisons using multiple instruments, including a mobile lidar; using satellite observations as a geographic transfer standards to compare measurements at different sites; and comparative investigations of the analysis software. NDSC is a research network, so each system has its own history, design, and analysis, and has participated differently in validation campaigns. There are still some technological differences that may explain different accuracies. However, the comparison campaigns performed over the last decade have always proved to be very helpful in improving the measurements. To date, more efforts have been devoted to characterising ozone measurements than to temperature observations. The synthesis of the published works shows that the network can potentially be considered as homogeneous within +/-2% between 20-35 km for ozone and +/-1 K between 35-60 km for temperature. Outside this altitude range, larger biases are reported and more efforts are required. In the lower stratosphere, Raman channels seem to improve comparisons but such capabilities were not systematically compared. At the top of the profiles, more investigations on analysis methodologies are still probably needed. SAGE II and GOMOS appear to be excellent tools for future ozone lidar validations but need to be better coordinated and take more advantage of assimilation tools. Also, temperature validations face major difficulties caused by atmospheric tides and therefore require intercomparisons with the mobile systems, at all sites.     

Influence of x-ray diffraction sample preparation on quantitative mineralogy: implications for chromate waste treatment

Powders of chromite ore processing residue (COPR) were mineralogically evaluated using quantitative X-ray powder diffraction (XRPD) to illustrate the impacts of sample preparation procedures. Chromite ore processing residue is strongly alkaline, reactive, contains minerals of varying hardness and absorption coefficients, and exhibits significant amorphicity. This poses a challenge to produce powders for XRPD analysis that are sufficiently fine and of uniform particle size while avoiding mineral reactions and overgrinding effects. Dry, hand pulverization to different grain sizes, and wet, mechanical pulverization (micromilling) using four milling liquids (cyclohexane, isopropanol, ethanol, and water), and variable milling durations (up to 15 min) were evaluated. Micromilling with a light, nonpolar, highly evaporative liquid such as cyclohexane with a milling time of 5 min mitigated systematic errors such as microabsorption and preferred orientation as it produced finer and more uniform particle size distributions than the hand-pulverized powders, while simultaneously affording the least time for sample preparation. Conversely, the use of water as milling liquid resulted in extensive hydration reactions during sample preparation, causing mischaracterization and significant underestimation of its reactive brownmillerite content, which can complicate the remediation design process for COPR. Hand pulverization emerged as a necessary complement to quantify Cr(VI)-containing, softer minerals destroyed during mechanical milling, the quantification of which has also important implications for COPR treatment design. The findings of this study may be applicable in a variety of geochemically complicated and reactive environmental media (metal-contaminated soils, stabilized/solidified media, inorganic waste), and points to the importance of the sample preparation method to obtain reliable quantitative XRPD results.     

Influence of biowaste compost amendment on soil organic carbon storage under arid climate

Organic matter amendments have been proposed as a means to enhance soil carbon stocks on degraded soils, particularly under arid climate. Soil organic carbon (SOC) plays a critical role in terrestrial carbon cycling and is central to preserving soil quality. The effects of biowaste compost (BWC) on soil carbon storage were investigated. In addition, changes in soil organic matter (SOM) and even soil organic carbon (SOC) in BWC-amended soils following different applications were studied. The added BWC quantities were as followed: BWC/soil (weight/weight (w/w) respectively: 1/8, 1/4, and 1/2). The different BWC-amended soils were assessed during 180 days under arid ambient conditions and in comparison with control soil. Results showed a significant increase in SOM and SOC with relation to BWC quantities applied. This increase was relatively clear up to 120 days, after which decrease in SOM and SOC levels were observed. Furthermore, results showed improved microbiological activities of the amended soils in comparison with the control soil. This was reflected by the increase of the amended soils’ respirometric activities as cumulative carbon dioxide carbon (C-CO₂) as function of incubation time and also in terms of specific respiration expressed as C-CO₂/SOC ratios.

Implications: Mediterranean soils under arid climate such as Tunisian soils are poor in organic matter content. Biowastes are potential source for soil fertilization. Composting process is the best method for the stabilization of organic matter of diverse origins. The biowaste compost amendment improves the soil organic carbon storage and enhances the soil microbial activity.     

Sensitivity of shortwave radiative fluxes to the vertical distribution of aerosol single scattering albedo in the presence of a desert dust layer

The aim of this work is to quantify the sensitivity of shortwave radiative fluxes to changes in the vertical distribution of aerosol absorption, taken into account through the aerosol Single Scattering Albedo (SSA). The case study represents a real atmospheric situation with a desert dust layer (DDL) in the mid troposphere over an urban Boundary Layer (BL) observed at Rome on 20 June 2007. A moderately high aerosol optical depth (AOD), 0.292 at 550 nm, and low Ångström exponent of 0.30 were measured. The observed case was reconstructed with a radiative transfer model, in which the SSA of the boundary layer aerosols was varied from that of a highly absorbing aerosol type (urban) to a highly scattering one (clear marine). The SSA of the DDL is determined keeping fixed the measured SSA of the whole atmospheric column. The simulations show notable changes in the surface and top of the atmosphere (TOA) diffuse fluxes depending on the boundary layer aerosol properties. The aerosol radiative forcing (ARF) at the surface changes by 6–19 W m^?2, depending on the solar zenith angle, when urban or clean marine particles are included in the boundary layer. The ARF differences observed at TOA are between 1 and 5 W m^?2 when urban and clean marine aerosol types in the BL are respectively used, showing a smaller dependency on the solar zenith angle than at the surface.     

Quantification of Saharan dust contribution to PM10 concentrations over Italy during 2003–2005

Italy is frequently affected by Saharan dust intrusions, which result in high PM₁₀ concentrations in the atmosphere and can cause the exceedances of the PM₁₀ daily limits (50 μg m^?3) set by the European Union (EU/2008/50). The estimate of African dust contribution to PM₁₀ concentrations is therefore a key issue in air quality assessment and policy formulation. This study presents a first identification of Saharan dust outbreaks as well as an estimate of the African dust contribution to PM₁₀ concentrations during the period 2003–2005 over Italy. The identification of dust events has been carried out by looking at different sources of information such as monitoring network observations, satellite images, ground measurements of aerosol optical properties, dust model simulations and air mass backward trajectory analysis. The contribution of Saharan dust to PM₁₀ monthly concentrations has been estimated at seven Italian locations. The results are both spatially (with station) and temporally (with month and year) variable, as a consequence of the variability of the meteorological conditions. However, excluding the contribution of severe dust events (21st February 2004, 25th–28th September 2003, 23rd–27th March 2005), the monthly contribution of dust varies approximately between 1 μg m^?3 and 10 μg m^?3 throughout year 2005 and between 1 μg m^?3 and 8 μg m^?3 throughout year 2003. In 2004 the dust concentration is lower than 2003 and 2005 (<5 μg m^?3 at all sites). The reduction in the number of daily exceedances of the limit value (50 μg m^?3) after subtraction of the dust contribution is also calculated at each station: it varies with station between 20% and 50% in 2005 and between 5% and 25% in 2003 and 2004.     

On the nonlinear effects of energy consumption,economic growth,and tourism on carbon footprints in the USA

Environmental Science and Pollution Research - The present paper implements the quantile autoregressive lagged (QARDL) approach of Cho et al. (2015) and the Granger causality in quantiles tests of...     

Degradation of chlordecone and beta-hexachlorocyclohexane by photolysis, (photo-)fenton oxidation and ozonation

Intensive use of chlorinated pesticides from the 1960s to the 1990s has resulted in a diffuse contamination of soils and surface waters in the banana-producing areas of the French West Indies. The purpose of this research was, for the first time, to examine the degradation of two of these persistent pollutants – chlordecone (CLD) and beta-hexachlorocyclohexane (β-HCH) in 1 mg L^?1 synthetic aqueous solutions by means of photolysis, (photo-) Fenton oxidation and ozonation processes. Fenton oxidation is not efficient for CLD and yields less than 15% reduction of β-HCH concentration in 5 h. Conversely, both molecules can be quantitatively converted under UV-Vis irradiation reaching 100% of degradation in 5 h, while combination with hydrogen peroxide and ferrous iron does not show any significant improvement except in high wavelength range (>280 nm). Ozonation exhibits comparable but lower degradation rates than UV processes. Preliminary identification of degradation products indicated that hydrochlordecone was formed during photo-Fenton oxidation of CLD, while for β-HCH the major product peak exhibited C₃H₃Cl₂ as most abundant fragment.     

Study of engine performance,emission and combustion characteristics fueled with diesel-like fuel produced from waste engine oil and waste plastics

Utilizing oil extracted from waste engine oil and waste plastics, by pyrolysis, as a fuel for internal combustion engines has been demonstrated to be one of the best available waste management methods. Separate blends of fuel from waste engine oil and waste plastic oil was prepared by mixing with diesel and experimental investigation is conducted to study engine performance, combustion and exhaust emissions. It is observed that carbon monoxide (CO) emission increases by 50% for 50% waste plastic oil (50WPO:50D) and by 58% for 50% waste engine oil (50WEO:50D) at full load as compared to diesel. Unburnt hydrocarbon (HC) emission increases by 16% for 50WPO:50D and by 32% for 50WEO:50D as compared to diesel at maximum load. Smoke is found to decrease at all loading conditions for 50WPO:50D operation, but it is comparatively higher for 50WEO:50D operation. 50WPO:50D operation shows higher brake thermal efficiency for all loads as compared to 50WEO:50D and diesel fuel operation. Exhaust gas temperature is higher at all loads for 50WPO:50D and 50WEO:50D as compared to diesel fuel operation.

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Biological treatment of fish processing wastewater: A case study from Sfax City (Southeastern Tunisia)

The present work presents a study of the biological treatment of fish processing wastewa at salt concentration of 55 g/L. Wastewater was treated by both continuous stirred-ta reactor(CSTR) and membrane bioreactor(MBR) during 50 and 100 days, respectively. Th biological processes involved salt-tolerant bacteria from natural hypersaline environme at different organic loading rates(OLRs). The phylogenetic analysis of the correspond excised DGGE bands has demonstrated that the taxonomic affiliation of the most domin species includes Halomonadaceae and Flavobacteriaceae families of the Proteobacteria(Gamm proteobacteria class) and the Bacteroidetes phyla, respectively. The results of MBR w better than those of CSTR in the removal of total organic carbon with efficiencies from 97 to 98.6%. Nevertheless, salinity with increasing OLR aggravates fouling that requires m cleaning for a membrane in MBR while leads to deterioration of sludge settleability a effluent quality in CSTR.