Long term effects of treated wastewater irrigation on calcisol fertility: A case study of Sfax-Tunisia

The use of treated wastewater (TW) for irrigation is increasingly being considered as a technical solution to minimize soil degradation and to restore nutrient content of soils. Indeed, TW usually contain large amounts of nutrient elements. The objective of this study is to evaluate the impact of long-term irrigation by TW on soil fertility under real field conditions. In the vicinity of the city of Sfax, a semi-arid region, a calcisol field has been irrigated for more 15 years with organic sodic TW;soil was modeled at three different depths (0 - 30, 30 - 60 and 60 - 90 cm) and along soil pits in the TW irrigated zone and in a nearby non-irrigated zone (control). Several parameters have been measured: soils pH, CEC, exchangeable cations, nitrate and ammonia, total contents of nitrogen, phosphorus and other essential macro and micro nutrients, electrical conductivity, soil organic carbon and dissolved organic carbon. C/N ratio and SUVA were calculated for each soil layer. The calculation of the isovolumic mass balance on soil profile scale was used to measure macro and micro nutrients supply. The TW irrigation has led to important supply in organic carbon (+100%), phosphorus (+80%) and in most essential nutrients (N, Mn, Zn). Due to the high rate of irrigation and low CEC of the studied soil, the added nutrient cations and nitrate are removed with leaching waters compared to the non-irrigated control soil. Moreover, Sfax’s TW bring about important amounts of salts and Na. Therefore the beneficial addition of nutrients could quickly be inhibited by the excessive supply of salts and available nitrogen. Apart from future crops production risk, groundwater degradation quality and soil fertility will be endangered over the long term.

Mapping Road Traffic Crashes in Sfax Governorate (Tunisia)

Sfax is one of the Tunisian governorates with a large number of road accidents, injuries and fatalities every year. This study aimed to analyze and map traffic accidents in this governorate. We analyzed the spatial distribution of accidents, their distribution by cause, by type of road, by size of traffic, by months of the year and days of the week. Accidents were correlated with several variables such as population numbers and densities, motorization rate, length and structure of the road network, and the amount of traffic. On the cartographic level, we have built a database, through which we have produced a series of thematic maps to argue this analysis. Through cartographic production, we also aimed to help road users, decision-makers and researchers in this area and in the field of transport. This work showed that Sfax occupies, among the other Tunisian governorates, an advanced position in gravity. Various human, climatic and technical factors explained this situation, of which human factors were the most important, and contributed to almost 90% of accidents. The current situation of accidents in Sfax requires a series of measures and actions to alleviate and mitigate the gravity of this phenomenon.

Spring phytoplankton variability along a south coast of Sfax at the water-sediment interface(Tunisia,Eastern Mediterranean Sea)

Objective:To compare the composition of the phytoplankton classes during the two spring studies,to study whether the spatial distribution of the phytoplankton is stable or not between spring 2010 and spring 2011 and to estimate the abiotic factor that mostly affects the structure and the richness of phytoplankton.Methods:Phytoplankton sub-samples were counted under an inverted microscope using the Utermöhl method.Phytoplankton identification was made from morphological criteria after consulting various keys.Results:Results showed a significant difference from spring 2010 to spring 2011 regarding nitrate/phosphate ratio,with high value in spring 2010(30.19±25.70).Relatively low nitrate/phosphate ratio(1.13±0.53)during spring 2011 might result from phosphogypsum.Phytoplankton was characterised by the proliferation of Bacillariophyceae(46%–78%of the total microphytoplankton)and by the large number of Euglenophyceae.Thirty two Bacillariophyceae species were identified at every station,represented essentially by Amphora sp.,Navicula sp.,Coscinodiscus sp.and Grammatophora sp.The results advise that Bacillariophyceae are usually adapted to particular ecological environment.Conclusions:This study shows that hydrological conditions in the south coast of Sfax present a high spatial and seasonal variability.The phytoplankton community distribution showed clear variations along the coastal stations during a spring cruises conducted in May 2010 and May 2011.The phytoplankton community found along the coast was dominated by opportunistic Bacillariophyceae species.

Olive Mill Waste Water Management Study by Using Principal Component Analysis

Olive mill waste water (OMWW) is a by-product issued after triturating olives. In Sfax, its management is different from urban to farming area. In this paper we treat it through a statistical analysis study during the season 2005-2006. Principal Component Analysis (PCA) and Hierarchical Classification (HC) methods are carried out on this work. Applied to variables issued from an exhaustive questionnaire including 274 mills, four Principal Components (PCs) are found to be significant, explaining 67% of the total variance. The coordinates of the 13 active variables retained by PCA were used to create a typology relative to the OMWW management and offered 7 groups of individuals which have the same characteristics, explaining 70% of the total inter-variance. This study showed that OMWW management in farming area could causes environmental problems because oleifactors haven’t controlled tanks and could evacuated OMWW on soil (causing oil deposit, waterproofing and possible asphyxia) or on public sewage network (causing corrosion, flow reduction). So, mills transfer from urban to farming areas in the form of agro-industrial complex is needed in the Sfax region.

A GIS-Agriflux Modeling and AHP Techniques for Groundwater Potential Zones Mapping

Groundwater is considered as the main portion of the water supply in arid and semi-arid regions. The Sfax plain area is part of the arid/semi-arid areas of Tunisia that are subject to the impact of climatic and human pressures. Water scarcity in combination with groundwater exploitation is a major concern in this region. Therefore, sustainable management and protection of groundwater resources, it necessary. The delineation of groundwater potential (GP) zones becomes an increasingly important tool for implementing successful management programs. The purpose of the present paper is to assess the potential zone of groundwater resources in the study area. An efficient approach using geographical information system (GIS), hydrological modelling and analytical hierarchy process (AHP) was developed. At first, six groundwater parameters that affect groundwater occurrences are derived from the spatial geodatabase. Those parameters are: Infiltration rate estimated from a GIS linked model, lineament density, drainage density, slope, rainfall and Land use/land cover. Then, the assigned weights of thematic layers based on expert knowledge were normalized by eigenvector technique of AHP. The parameter layers were integrated and modeled using a weighted linear combination (WLC). The resulting map was classified into four categories: very low, low, good, and excellent. The results showed that about 26% of the study area falls under very-low-potential zone, with 30% on low-potential zone, 21% with good potential zone, and 23% falling under excellent zone. The results of the analysis were validated using pumping rate data and curve trend of sensitivity classes theory validation of outcomes indicated a good prediction accuracy. The results of the present study can serve to prepare a comprehensive groundwater development and management plans proving its efficacy in this art of exploratory investigations.