The main objective of this study is to estimate the total economic loss due to inefficient use of irrigation water in Tunisia. Several approaches have been used for this purpose. The optimal level of water application for different crops is calculated using the actual crop evapotranspiration which is based on FAO-56 method. The residual imputation and yield comparison methods have been used to estimate the economic value of irrigation water for different irrigated crops in different bioclimatic areas. For the empirical analysis, primary data were obtained from a series of surveys that covered 78% of the total irrigated areas and were collected within the framework of the BVirtual Water and Food Security in Tunisia project^ (2013–2015). Secondary data about land distribution of crops in Tunisia were taken from the Ministry of Agriculture (2016). Around 724 farms were randomly sampled considering their bioclimatic area, farm type, and production system. The survey included the main 20 crops produced in Tunisia. Results show that most of farmers are either under or over utilizing irrigation water. The value of total direct economic losses, at the country level, of both types of water inefficiencies, was estimated to around 470 million Tunisian Dinars. Therefore, an improvement of water use efficiency at field level through dissemination of information/knowledge on irrigation scheduling and crop water requirements by extension services to farmers is needed to reduce this huge economic loss, reach higher sustainability in water use and improve food security.

140 contaminants belonging to various classes (organochlorine and organophosphorus pesticides, pyrethroid insecticides, carbamates, fungicides, acaricides, herbicides, synergists, insect growth regulators, polychlorobiphenyls, polycyclic aromatic hydrocarbons) were simultaneously analysed by GC-MS/MS in marine sediments, aquatic plant leaves and fish tissues samples. A total of 260 samples from five stations along the coast of Tunisia were evaluated. The results highlight that only 28 residues (12 polychlorobiphenyls, 8 organochlorine pesticides, 7 polycyclic aromatic hydrocarbons and triphenyl phosphate) were detected at levels higher than relative LOQ values. The amounts in sediment samples were compared with Sediment Quality Guidelines (SQGs) showing that the values are acceptable and no toxic effect is expected on aquatic organisms. A little variation of contaminant residues in sediment samples among coastal stations was recorded. Namely, with respect to almost all polychlorobiphenyls and organochlorine pesticides, higher values were recorder in summer. With respect to almost all polycyclic aromatic hydrocarbons, higher values were recorder in autumn. Aquatic plant leaves showed a residue accumulation higher than that of other compartments of marine system. The data about fish samples (Sparus aurata and Sarpa salpa, the two most frequently caught fish species at five sites on the central coast of Tunisia) do not pose direct hazard to human health because values were lower than protection limits.

The aim of this study was to assess, for the first time, the concentrations, sources, dry deposition and human health risks of polycyclic aromatic hydrocarbons (PAHs), aliphatic hydrocarbons (AHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in total suspended particle (TSP) samples collected in Bizerte city, Tunisia (North Africa), during one year (March 2015–January 2016). Concentrations of PAHs, AHs, PCBs and OCPs ranged 0.5–17.8 ng m−3, 6.7–126.5 ng m−3, 0.3–11 pg m−3 and 0.2–3.6 pg m−3, respectively, with higher levels of all contaminants measured in winter. A combined analysis revealed AHs originating from both biogenic and petrogenic sources, while diesel vehicle emissions were identified as dominant sources for PAHs. PCB potential sources included electronic, iron, cement, lubricant factories located within or outside Bizerte city. The dominant OCP congeners were p,p′-DDT and p,p′-DDE, reflecting a current or past use in agriculture. Health risk assessment showed that the lifetime excess cancer risk from exposure to airborne BaP was negligible in Bizerte, except in winter, where a potential risk to the local population may occur.

Antimicrobial resistance is a growing and significant threat to global public health, requiring better understanding of the sources and mechanisms involved in its emergence and spread. We investigated the abundance of antibiotic resistance genes (ARGs) before and after treatment in five wastewater treatment plants (WWTPs) located in different areas of the Monastir Governorate (Tunisia). Three of these WWTPs (Frina, Sahline and Zaouiet) use a conventional activated sludge process as secondary treatment, whereas the WWTP located in Beni Hassen applies an ultraviolet disinfection step after the activated sludge process and the WWTP located in Moknine treats wastewater using naturally aerated lagoons as a secondary treatment process. The abundance of six ARGs (blaCTX-M, blaTEM, qnrA, qnrS, sul I and ermB) and the class 1 integron-integrase gene (intI1) were determined by quantitative PCR. All ARGs and the intI1 gene were detected in the wastewater samples, except the blaCTX-M gene, which was not detected in both influent and effluent samples from Sahline and Beni Hassen WWTPs, and the qnrS gene, which was not detected neither in the WWTP influent in Moknine nor in the WWTP effluent in Beni Hassen. Although the relative concentration of ARGs was generally found to be similar between samples collected before and after the wastewater treatment, the abundance of blaCTX-M, blaTEM, and qnrS genes was higher in the effluent of the Frina WWTP which, unlike other WWTPs, not only receives domestic or industrial sewage but also untreated hospital waste. To the best of our knowledge, this study quantified for the first time the abundance of ARGs in different Tunisian WWTPs, and the results agree with previous studies suggesting that conventional wastewater treatment does not efficiently reduce ARGs. Therefore, these findings could be useful to improve the design or operation of WWTPs.

Plastic film mulching and use of wastewaters for irrigation have been common agricultural practices for over half a century in Tunisia, especially in arid regions, resulting in the undesired creation of a pathway for microplastics (MPs) to enter farmland soil. In order to assess the extent and characteristics of soil contamination by MPs in the Moknine province, an area of intensive agricultural practices, 16 farmland soil samples were collected and characterized. The total concentration of targeted MPs was 50–880 items/kg; among them, the most common MPs type being polypropylene (PP), mainly occurring as white/transparent fibers with small size (cross section <0.3 mm). SEM images of MPs surfaces revealed multiple features related to environmental exposure and degradation. ATR-FTIR spectroscopy and pyrolysis-GC/MS analyses enabled the accurate identification of MPs separated from the embedding soil micro- and macro-aggregates. Finally, contamination of the polymeric microparticles with a broad range of metals was found by ICP-MS analysis, suggesting that MPs can be vectors for transporting heavy metals in the soil and indicators of soil contamination as a result of mismanagement of industrial wastewaters.

Little is known about the main sources of ambient particulate matter (PM) in the 22 Eastern Mediterranean Region (EMR) countries. We designed this study to systematically review all published and unpublished source apportionment (SA), identification and characterization studies as well as emission inventories in the EMR. Of 440 articles identified, 82 (11 emission inventory ones) met our inclusion criteria for final analyses. Of 22 EMR countries, Iran with 30 articles had the highest number of studies on source specific PM followed by Pakistan (n = 15 articles) and Saudi Arabia (n = 8 papers). By contrast, there were no studies in Afghanistan, Bahrain, Djibouti, Libya, Somalia, Sudan, Syria, Tunisia, United Arab Emirates and Yemen. Approximately 72% of studies (51) were published within a span of 2015–2021.48 studies identified the sources of PM₂.₅ and its constituents. Positive matrix factorization (PMF), principal component analysis (PCA) and chemical mass balance (CMB) were the most common approaches to identify the source contributions of ambient PM. Both secondary aerosols and dust, with 12–51% and 8–80% (33% and 30% for all EMR countries, on average) had the greatest contributions in ambient PM₂.₅. The remaining sources for ambient PM₂.₅, including mixed sources (traffic, industry and residential (TIR)), traffic, industries, biomass burning, and sea salt were in the range of approximately 4–69%, 4–49%, 1–53%, 7–25% and 3–29%, respectively. For PM₁₀, the most dominant source was dust with 7–95% (49% for all EMR countries, on average). The limited number of SA studies in the EMR countries (one study per approximately 9.6 million people) in comparison to Europe and North America (1 study per 4.3 and 2.1 million people respectively) can be augmented by future studies that will provide a better understanding of emission sources in the urban environment.

A microcosm experiment was carried out to study the ecotoxicity and interactions between heavy metals and polyvinyl chloride microplastics. Fifteen treatments were tested and results were examined after one month. In details, this work aims to study the ecotoxicological effects of cadmium (10 and 20 mg kg⁻¹ Dry Weight DW), polyvinyl chloride (PVC) and its modified forms; PVC-DETA (PD) and PVC-TETA (PT) (20 and 40 mg kg⁻¹ DW), separately and in mixtures, on meiofauna from Bizerte lagoon (NE Tunisia) with focus on nematode features. The results obtained showed that individual treatments were toxic for meiofauna and particularly for free-living nematodes. No clear trends characterized the numerical responses but significant reductions were observed for diversity indices. Moreover, the binary combinations of contaminants have a lesser toxic effect compared to their individual effects. This effect could be related to the high-capacity chelating ability of PVC and its polymers against cadmium.

A laboratory bioassay was conducted to investigate the ecotoxicity of a chromium-enriched superfood, Spirulina platensis, on the meiofauna collected from the Ghar El Melh lagoon, Tunisia. After 1 month of exposure, the abundances of meiobenthic taxa and the taxonomic and morpho-functional diversity of nematodes showed significant differences between the Spirulina and Spirulina + chromium groups. The nematodes were more tolerant of all types of stressors compared to harpacticoids, polychaetes, and oligochaetes, and the lowest taxonomic and morpho-functional diversity of nematodes was observed in the highest sedimentary concentration of S. platensis (50% DW). The mixed treatments may have been richer in micro-habitats and subject to low selective pressure, thereby hosting nematodes with a wide range of adaptations. The responses of the nematode species differed depending on their functional traits. Spirulina enriched with chromium induced two responses for the same feeding group: high toxicity for Daptonema fallax and low toxicity for two Theristus species (T. flevensis and T. modicus). The ecotoxicity of the Spirulina/chromium mixtures were lower than that of Spirulina alone, suggesting mutual neutralization between these two elements. The association between functional traits and taxonomic diversity showed that the effects of the mixtures were not additive and that one of the stressors camouflaged the effect of the other. Our findings should encourage the commercialization of chromium-enriched S. platensis owing to its lower ecotoxicity than Spirulina alone.