Analysis of hydrochemical characteristics and assessment of organic pollutants (PAH and PCB) in El Fahs plain aquifer, northeast of Tunisia

The availability of good quality groundwater constitutes a major concern in many developing countries. The El Fahs shallow aquifer, northeastern Tunisia, is an important source of water supply for various economic sectors in the agricultural region. The intensive exploitation of this groundwater has led to its quality degradation. In fact, assessment of water quality degradation is very useful in planning the conservation and management practices of water resources in this watershed. This research aims to evaluate the groundwater quality and its suitability for irrigation uses, identify the main processes to assess their chemical composition, and investigate the potential sources of persistent organic pollutants (POPs). The hydrogeochemical investigation is thus conducted by collecting groundwater samples and analyzing their physicochemical characteristics. Polycyclic aromatic hydrocarbons (16 PAHs) and polychlorinated biphenyls (7 PCBs) were determined in groundwaters from nine stations. The sampling took place in July 2020. The relative abundance of ions was Na > Mg > Ca > K for cations and Cl > SO4 > HCO3 for anions. The groundwater exhibits two predominant hydrochemical facies: Ca-Mg-Cl/SO4 and Na-Cl. The relevant recorded pollutant is nitrate, which was generally far above values of pollution thresholds indicating the influence by the intensive agricultural activity. The suitability for irrigation purposes was assessed using several parameters (EC, SAR, %Na, TH, PI, Mh, and Kr). As a matter of fact, the results mentioned that the majority of the samples are unsuitable for irrigation uses. An analysis of the organic pollutants indicates that the total PAH and PCB concentrations are above the permissible values. Therefore, a considerable predominance of naphthalene and PCB28 was observed in order to discriminate between pyrolitic and petrogenic PAH sources; low-molecular-weight (LPAH)/high-molecular-weight (HPAH) ratio was calculated. Results showed that PAHs were mainly of petrogenic origin. The results revealed also that the chemical composition of groundwater is influenced by evaporation process, ion exchange, and water-rock interaction during the flow. A high risk of organic contamination has been highlighted linked to anthropogenic activities which have exerted increasing pressure on groundwater quality. The presence of organic pollutants in groundwater is becoming a serious threat to the environment and human health.

GIS-based multi-criteria decision-making techniques and analytical hierarchical process for delineation of groundwater potential

The profound knowledge and management of groundwater resources is a prerequisite in order to ensure the sustainability of these resources. In this research, multi-criteria decision-making (MCDM) and analytical hierarchical process (AHP) method based on GIS were used to determine the groundwater potential recharge model of the Mornag plain (coastal area in North Tunisia). Influential eight factors were used in the groundwater recharge modeling: lithology, land use/land cover, hydrogeomorphology, elevation, rainfall, drainage density, lineament density, and soil. The influence of each factor was examined by the weighted linear combination method. The results reveal a very high to high groundwater recharge potential in the order of 20% of the total area. The validation of results by the histogram method showed that 41% of the total area corresponds to the moderate to very high recharge potential classes. The groundwater recharge potential model (GIS-MCDM-AHP) is useful in better management and planning of groundwater resources and implementation of wells and hydraulic structures in arid and semi-arid areas.

Zincum Metallicum, a homeopathic drug, alleviates Zn-induced toxic effects and promotes plant growth and antioxidant capacity in Lepidium sativum L

In this study, we investigated the effect of the homeopathic drug Zincum Metallicum (ZM) on zinc (Zn) toxicity in the plant species Lepidium sativum L. We focused on growth parameters, Zn uptake and numerous biochemical parameters. Seedlings were hydroponically subjected during 7 days to 0.05, 500, 1000, 1500 and 2000 µM Zn²⁺, in the absence or presence of 15ch or 9ch ZM. In the absence of ZM, Zn induced negative effect on growth especially at the dose of 2 mM. Zn induced also chlorosis, reduced total chlorophyll and/or carotenoid content and increased the level of malondialdehyde (MDA). Under Zn toxicity (500, 1000 and 1500 µM), the superoxide dismutase (SOD), catalase (CAT), gaiacol peroxidase (GPX) and glutathione reductase (GR) activities were increased or not significantly affected, while at 2000 µM Zn affected the activity of these enzymes. At the highest Zn level (2 mM), proline and total polyphenol and flavonoid contents were markedly increased in leaves and roots of L. sativum. Additionally, ZM supply considerably ameliorated the plant growth, photosynthetic pigment contents and increased non-enzymatic antioxidant molecules and enzymatic activities against Zn-induced oxidative stress. Our data suggest that homeopathic properties of ZM may be efficiently involved in the restriction of Zn-induced oxidative damages, by lowering Zn accumulation and translocation in the leaves and roots of Lepidium sativum L.

Evaluation of pollution by heavy metals of an abandoned Pb-Zn mine in northern Tunisia using sequential fractionation and geostatistical mapping

This study investigates the contents of lead, zinc, and cadmium in 109 near-surface soil samples collected around the abandoned mine of Fedj Lahdoum, northern Tunisia, to assess the risk of pollution they generate. The study involved some analytical procedures such as pH measurements, X-ray diffraction techniques, sequential fractionation, and geostatistical mapping using the ordinary Kriging techniques. The sequential fractionation revealed that the bioavailability of Pb, Zn, and Cd follows the orders F5 > F3 » F4 > F2 » F1, F5 > F3 » F4 » F2 > F1 and F5 > F2 » F4 > F1, respectively; their associations with organic matter and residual sulfides (F4) are relatively low. However, their high cumulated contents are dominantly associated with the residual (F5) and reducible (F3) fractions. The geostatistical mapping was endeavored to predict the spatial distribution of the studied heavy metals at unsampled sites and to produce a cumulated risk map of soil pollution. The latter is discussed with emphasis of the main factors responsible for the scattering of the pollution as much as the landscape conditions, the chemical composition of the mine tailings, the surface drainage of meteoric water and the wind. This study provides insight into the delineation of the spatial spreading of Pb, Zn, and Cd around the abandoned mine Fedj Lahdoum and their surrounding urban areas. It reveals that the mine infrastructure areas encompassing both extraction and processing and tailing deposition areas are the main sources of contamination. And the landscape conditions together with the surface drainage of meteoric water and the wind are the main factors responsible for the scattering of the pollution.

Pneumatosis cystoides intestinalis revealed after a hand-to-hand aggression: A case report

INTRODUCTION

Pneumatosis cystoides intestinalis (PCI) is a condition defined by the presence of multiple gas-filled cysts within the intestinal wall. We demonstrated a case of PCI presenting as pneumoperitoneum following a hand-to-hand aggression. Consent was obtained from the patient for publication of this paper.

PRESENTATION OF THE CASE

This article describes a case of an 28 year-old man with medical history of gastroduodenal ulcer admitted in the emergency room with an acute abdominal pain secondary to a hand-to-hand aggression. Computed tomography (CT-scan) revealed signs of PCI, the presence of pneumoperitoneum and a small amount of fluid in the Douglas pouch. The patient underwent an urgent laparotomy in front of a high suspicion of a bowel perforation. Per operative findings revealed multiple small cysts of the terminal ileum and there were no bowel perforation.

DISCUSSION

Pneumatosis cystoides intestinalis may be related to a wide spectrum of gastrointestinal conditions. The diagnosis of PCI can be established by endoscopic ultrasound or CT-scan imaging. Management of PCI is conditioned by the clinical and radiological presentation which is essentially related to the primary cause. Conservative approach is allowed in a stable patient with no signs of complications. In the presence of predictive factors of pathologic PCI, namely transmural ischemia and bowel perforation, surgical operation is required.

CONCLUSION

The management of PCI may be challenging particularly in the presence of pneumoperitoneum. Complications must be excluded before considering a conservative therapy. Therefore, PCI should be interpreted with relevance to the entire clinical context.

Sulfide influence on metal behavior in a polluted southern Mediterranean lagoon: implications for management

The degree of pyritization and degree of trace metal pyritization (DTMP) were investigated in sediments from Ghar El Melh Lagoon (northern Tunisia) in order to study metal deposition. A sediment core and 28 samples were thus taken in summer 2008, and metals and sulfate were analyzed in pore water/pyrite. Acid-volatile sulfide and metals were simultaneously extracted from these two fractions and the role of pyrite in the metal cycling studied. To examine pyrite presence and mineralogical form in sediments, X-ray diffraction of the washed and decarbonated sediment was performed along with scanning electron microscopy. Results showed that pyrite is present in fromboidal and euhedral forms. Thermodynamic calculation highlighted the formation of metallic sulfides and the co-precipitation of metals with iron sulfides. The DTMP increases with depth, indicating that these metals are either sequestered as sulfides or that they co-precipitate with pyrite into the deep sediment.

Mobilization of lead-zinc rich particles from mine tailings in northern Tunisia by aeolian and run-off processes

Dispersion of metal rich particles from mine tailings is an important hazard for the environment. Specially, in Mediterranean context, this is potentially more risky because of the violence of climatic events. Northern Tunisia includes about 50 mining districts with an ore mineralogy consisting mainly of galena, iron sulphides and subordinate sphalerite embedded in a calcitic and baritic gangue. A century of mining exploitation left waste rich in potentially toxic elements (PTE) with values up to 46900 mg/kg for Pb and 49501 mg/kg for Zn, stored in uncontrolled and untreated deposits. The PTE contents observed in the surrounding soils generally devoted to agricultural activities are as high as 12488 mg/kg for Pb, 3485 mg/kg for Zn and 15 mg/kg for Cd. The contents in sediments downstream are also high, in the range of 47800 mg/kg for Pb, 5767 mg/kg for Zn and 36 mg/kg for Cd. PTE-bearing phases are mainly sulphides, carbonates and iron oxyhydroxydes. Because of the lack of vegetation and the presence of fine particles in the mining wastes, PTE were dispersed to nearby areas, resulting in the contamination of agricultural soils and river sediments.

Under the Mediterranean climate which includes a long dry summer with windy episodes and heavy rainfall in the winter, mine tailings are exposed to two types of erosion: hydraulic erosion with transport during heavy rainfall events and aeolian erosion inducing fine particle dispersion. Dispersion of the PTE from mine tailings in northern Tunisia presents a risk of environmental contamination and of toxicity by inhalation for the habitants near the former mining districts. Furthermore these PTE can be transferred from agricultural soils surrounding the tailings to the cultivated plants (mainly cereals).