Geochemical behaviour of PM10 aerosol constituents under the influence of succeeding anticyclonic/cyclonic situations: case of Sfax City, southern Tunisia

Influence of anthropogenic activities on metals, sugars and PAHs in PM10 in the city of Fez, Morocco: Implications on air quality

Particulate matter (PM) is an important component in the atmosphere, affecting air quality, health, radiation balance, and global climate. To assess regional air quality in the city of Fez, an intensive field campaign was carried out in the autumn of 2019 in the Middle Atlas region of Morocco. Aerosol sampling was performed simultaneously at two urban sites in the city of Fez: (1) Fez University (FU), a sub-urban site, and (2) Fez Parc (FP), an urban site located in the city center of Fez, using PM10 collectors. Various laboratory analyses were carried out, including PM mass, trace metals, inorganic ions, OC/EC, sugar compounds, and PAHs. The results indicate that the PM10 mass (61 ng m-3) was comparable at both sites, with a 37-107 ng m-3 range. Most of the 19 investigated PAHs at the FU site (10.2 ± 6.2 ng m-3) were low-molecular-weight PAHs, while the most abundant PAHs at the FP site (6.9 ± 3.8 ng m-3) were mainly higher-molecular-weight PAHs. A diagnostic ratio analysis at both sites indicated that PAHs originated from fossil fuel combustion and traffic emissions from diesel engines, with Ant/(Ant + Phe) and Flu/(Flu + Pyr) ratios averaging 0.22 and 0.84, respectively. PMF analysis identified traffic emissions as a major source (30%), with secondary inorganic aerosols (20%) and biomass burning (14%). Polar plots highlight the dominance of local anthropogenic activities in PM pollution, with vehicular emissions, industrial activities, and biomass burning. This study shows that local sources and combustion processes significantly contribute to PM10 sources in Morocco, providing insights into air pollution mitigation in North Africa.

Analysis of Daily and Diurnal O3-NOx Relationships and Assessment of Local/Regional Oxidant (OX = O3 + NO2) Levels and Associated Human Health Risk at a Coastal Suburban Site of Sfax (Tunisia)

The present study investigated the temporal variability of surface ozone and its nitrogen precursors at the proximity of a traffic crossroad (≈ 22,580 vehicles per day) located in a coastal suburban site of Sfax city (Tunisia). It was performed during January-October, 2010. The study results show that the surface ozone is characterized by a slightly modulated regime between day and night. At traffic-peak hours, the decrease of ozone concentration levels is due to the oxidation reaction of NO into NO₂. Complementary statistical approaches (inter-variable correlation matrix, cluster analysis, representation quality of variables and multiple regression analysis) reveal that the excess of O₃ is mainly affected by the wind speed, temperature, solar radiation and NO₂ with contribution rates of 127, 21, 22 and 12%, respectively. The decrease of O₃ is, however, controlled by NO, relative humidity and boundary layer height with contribution rates of 25, 21 and 16%, respectively. The regional daytime and night-time contributions to O₃ are very different. The daytime intercept which is greater than that of night-time indicates there was a large NO_x independent regional contribution. This could be attributed to the biogenic VOCs effect interfering in the photochemical cycle. It, therefore, implies that the study site is VOC-sensitive. The investigation of the air quality index (AQI) for O₃ and NO₂ showed that more than 86% of the total studied period has a good quality level. Only about 14% of total days are characterized by an acceptable air quality level, however, for a very small number of people are unusually sensitive to air pollution.

Hydrolytic enzyme screening and carotenoid production evaluation of halophilic archaea isolated from highly heavy metal-enriched solar saltern sediments

This paper aimed to screen the enzymatic activities and evaluate the carotenoid production level of twenty-two halophilic archaea isolated from Sfax solar saltern sediments. The molecular identification performed by sequencing the 16S rRNA genes showed that all strains have a high similarity degree (99.7-100%) with Halobacterium salinarum NRC-1. The strains were screened for the presence of eight hydrolase activities using agar plate-based assays. The most detected enzyme was gelatinase (77.27% of total strains), followed by protease (63.63%) and amylase activities (50%). The carotenoid production yields of the strains ranged between 2.027 and 14.880 mg/l. The UV-Visible spectroscopy of pigments revealed that it was a bacterioruberin type. When evaluated and compared to the standard β-carotene, the antioxidant capacities of these pigments showed a scavenging activity of more than 75% at a concentration of 5 μg/ml for three strains (AS16, AS17, and AS18). Then a sequence of one-step optimization processes was performed, using the one-factor-at-a-time approach, to define the optimum conditions for growth and carotenoid production of the highest carotenoid producing strain (AS17). Different environmental factors and nutritional conditions were tested. Variations in these factors were found to deeply influence growth and carotenoid production. A maximum carotenoid production (16.490 mg/l), higher than that of the control (14.880 mg/l), was observed at 37 °C, pH 7, 250 g/l of salinity, with 80% air phase in the flask at 110 rpm, in presence of light and in culture media containing (g/l) 10, yeast extract; 7.5, casamino acid; 20, MgSO4; 4, KCl; and 3, trisodium citrate.

Mobility of trace metals and microbiological pollution from dredged sediments to the Gulf of Gabes, Tunisia

Sediments are periodically dredged from the major ports in the Gulf of Gabes (GG) during maintenance operations. These sediments are dumped near the coats of Sfax and Gabes cities. In the present study, 6 trace metals (Cd, Cu, Cr, Ni, Pb, and Zn) concentrations were assessed in both sediments and column water taken from the different basins of Sfax port. This study is the first to focus on the microbial and microalgae contaminations of Sfax port sediments. The spatial distributions of trace metals in dredged sediments from the different basins of Sfax port show that the maximum concentrations of Cd (13.75 µg/g), Cu (892.5 µg/g), and Zn (1447 µg/g) exceeded the Geode standard thresholds. The same elements, also detected in the water column, exceeded the toxicity thresholds for phytoplankton, shellfish, and algae (Cd 0.095 µg/l, Cu 4.52 µg/l, and Zn 37 µg/l). The presence of coliforms, indicators of sewage pollution, as pathogenic germs (Pseudomonas), was shown through microbiological examinations of the sediments and water column. The microalgae enumeration showed the abundance of dinoflagellate cysts (stressed form) which attests to the presence of severe conditions in Sfax port. Different toxic species were identified as Prorocentrum lima and Alexandrium minutum. The same trace metal sources and abundance in Sfax port and GG sediments suggest the hypothesis of their transfer from their disposal sites in coastal areas to deeper depths in the GG and until Boughrara lagoon (BL). As trace metals, microalgae species were also transferred by hydrodynamic currents inside the GG where they found suitable conditions to their proliferation causing the seawater coloration phenomenon, eutrophication, and degradation of the aquatic system.

In-site and Ex-site Date Palm Exposure to Heavy Metals Involved Infra-Individual Biomarkers Upregulation

As a tree of considerable importance in arid regions-date palm, Phoenix dactylifera L. survival in contaminated areas of Sfax city has drawn our attention. Leaf samples of the plants grown in the study area showed high levels of cadmium (Cd), copper (Cu), and chromium (Cr). On the basis of this finding, the cellular mechanisms that explain these metal accumulations were investigated in controlled conditions. After four months of exposure to Cd, Cr, or Cu, high bioconcentration and translocation factor (TF>1) have been shown for date palm plantlets exposed to Cd and low TF values were obtained for plantlets treated with Cr and Cu. Moreover, accumulation of oxidants and antioxidant enzyme activities occurred in exposed roots to Cu and Cd. Secondary metabolites, such as polyphenols and flavonoids, were enhanced in plants exposed at low metal concentrations and declined thereafter. Accumulation of flavonoids in cells may be correlated with the expression of the gene encoding Pdmate5, responsible for the transport of secondary metabolites, especially flavonoids. Other transporter genes responded positively to metal incorporation, especially Pdhma2, but also Pdabcc and Pdnramp6. The latter would be a new candidate gene sensitive to metallic stress in plants. Expressions of gene coding metal chelators were also investigated. Pdpcs1 and Pdmt3 exhibited a strong induction in plants exposed to Cr. These modifications of the expression of some biochemical and molecular based-markers in date palm helped to better understand the ability of the plant to tolerate metals. They could be useful in assessing heavy metal contaminations in polluted soils and may improve accumulation capacity of other plants.

Pollution characteristics and health risk assessment of heavy metals in dry atmospheric deposits from Sfax solar saltern area in southeast of Tunisia

Concentrations of six heavy metals such as Fe, Pb, Cu, Cd, Ni and Zn in dry atmospheric deposits weekly collected through 20 sample sites from Sfax solar saltern during two successive sampling campaigns, selected from a long time monitoring, have been examined in order to evaluate their contamination levels as well as their human health risk; such concentrations (expressed in mg/kg) have shown that Fe varied from 7006.24 to 7856.45, Pb from 8.64 to 344.45, Cu from 9.33 to 298.67, Cd from 0.16 to 85.24, Ni from 6.02 to 150.02, and Zn from 12.23 to 624.57. During the study period, average concentrations (mg/kg) have been 7315.99, 103.08, 82.34, 15.93, 46.21 and 142.39, for Fe, Pb, Cu, Cd, Ni and Zn, respectively. Except for Fe, the other concentrations in dry atmospheric deposits have recorded the highest level during the first campaign especially in the sites which are close and more exposed to emissions of local pollutant industries, as well as nearby main road, resulting from high exposure frequencies. Statistical approaches, such as principal component analysis and hierarchical cluster analysis have been applied to all data, revealing an affinity between analyzed metals resulting from their origins, and confirming the influence of exposure frequencies on the spatial variability of heavy metal concentrations. Human health risk assessment has revealed that ingestion of heavy metals is the main exposure pathway for the local population. Computed Hazardous Quotient and Hazardous Index have been higher for children than for adults, thus indicating that the former may be subjected to potentially higher health risk than the latter especially during the first campaign. Calculated carcinogenic risks through ingestion and dermal contact, as well as the total carcinogenic risk for the selected heavy metals, have shown that cancer could occur more probably through ingestion than dermal contact, for children than adult, and during the first campaign (during C1: average values CRing = 8.72 × 10^-4 and CRder = 1.40 × 10^-6 for child; average values CRing = 5.61 × 10^-5 and CRder = 2.84 × 10^-6 for adult) than the second one (during C2: average values CRing = 1.59 × 10^-4 and CRder = 2.54 × 10^-7 for child; average values CRing = 1.02 × 10^-5 and CRder = 5.19 × 10^-7 for adult). The total calculated carcinogenic risk through all the sites have infrequently signaled high to very high carcinogenic risk in the first campaign (average CRA = 8.73 × 10^-4 for child and CRA = 5.89 × 10^-5 for adult) and occasionally exceeded the safe range for the local population in the second one (average CRA = 1.59 × 10^-4 for child and CRA = 1.07 × 10^-5 for adult).

Spatial and temporal variations of dust particle deposition at three "urban/suburban" areas in Sfax city (Tunisia)

Particle deposition in three selected "urban/suburban" sites in Sfax city, southern Tunisia, was studied through biweekly monitoring particulate deposits from April 12 to November 26, 2014. Two sites (S1 and S2) were located at the proximity of well-exposed cross-roads; however, the third (S3) was located at a street canyon. A very high fluctuation in those particle fluxes, ranging from 0.1 and 17.9 g/m(2), was clearly observed. Spatiotemporal distribution of the deposited particulate fluxes proved the concomitant effects of multiple (local and synoptic) sources. The industrial contribution rate in terms of particulate deposits was demonstrated to be negligible, and as for that of traffic, it was confirmed to be more significant. The highest particulate deposition seemed to be associated with the sirocco wind phenomenon. Humidity appeared as a main parameter reinforcing the particle deposition (by gathering process); however, the rain was considered as an important factor in terms of atmosphere washing. The intersite distribution was also threatened by local wind movements, shown as a non-negligible factor in terms of deposition, especially in the street canyon.