HUMAN INDUCED HYDROGEOLOGICAL CHANGES AND SINKHOLES IN THE COASTAL GYPSUM KARST OF LESINA MARINA AREA (FOGGIA PROVINCE, ITALY)

In 1930, a canal was excavated to connect the Lesina Lagoon with the Adriatic Sea, modifying the track of the previous existing Acquarotta canal. The 1100 m long stretch of the canal situated next to the coast exposed unknown highly cavernous gypsum bedrock underlying a loose sandy cover. During the last two decades, a large number of cover collapse and cover suffosion sinkholes have formed along two bands situated next to the canal, impinging the adjacent Lesina Marina residential area. The area affected by subsidence has increased exponentially from 1999 to 2009. The tight spatial correlation between the sinkholes and the canal reveals that the subsidence phenomenon has been induced by the local hydrogeological changes caused by the canal in the coastal evaporite aquifer: (1) Local lowering of the average water table. (2) Deflection of the groundwater flow lines towards the canal and increase in flow velocity. (3) Amplification of the groundwater level oscillations, largely controlled by the tidal regime. (4) Local reversals in the groundwater flow, changing the canal temporarily from effluent to influent. These changes in the hydrogeological functioning of the system have favoured both internal erosion and karstification processes. Hydrochemical evidence reveals that gypsum dissolution is a currently active process favoured by fresh water and sea water mixing and cationexchange processes. Most likely, the partial replacement of a concrete lining in the canal by pervious gabions in 1993 provided more adequate conditions for the evacuation of the sediments filling the karst conduits, accelerating internal erosion and sinkhole development

Characterization of the lowland coastal aquifer of Comacchio (Ferrara, Italy): Hydrology, hydrochemistry and evolution of the system

This study delineates the actual hydrogeochemistry and the geological evolution of an unconfined coastal aquifer located in a lowland setting in order to understand the drivers of the groundwater salinization. Physical aquifer parameterization highlights a vertical hydraulic gradient due to the presence of a heavy drainage system, which controls the hydrodynamics of this coastal area, forcing groundwater to flow from the bottom toward the top of the aquifer. As a consequence, relict seawater in stable density stratification, preserved within low permeability sediments in the deepest portion of the aquifer, has been drawn upward. The hydrogeochemical investigations allow identifying the role of seepage and water-sediment interactions in the aquifer salinization process and in the modification of groundwater chemistry. Mixing between freshwater and saltwater occurs; however, it is neither the only nor the dominant process driving groundwater hydrochemistry. In the aquifer several concurring and competing water-sediment interactions - as NaCl solution, ion-exchange, calcite and dolomite dissolution/precipitation, oxidation of organic matter, and sulfate bacterial reduction - are triggered by or overlap freshwater-saltwater mixing The hyper-salinity found in the deepest portion of the aquifer cannot be associated with present seawater intrusion, but suggests the presence of salt water of marine origin, which was trapped in the inter-basin during the Holocene transgression. The results of this study contribute to a better understanding of groundwater dynamics and salinization processes in this lowland coastal aquifer. © 2013 Elsevier B.V

Hydrochemistry of groundwater in a coastal region and its repercussion on quality, a case study—Thoothukudi district, Tamil Nadu, India

A hydrogeochemical study was conducted in Thoothukudi district situated in the southeast coast of Tamil Nadu, India to identify the influence of saltwater intrusion and suitability of groundwater for domestic and agricultural purposes. Scattered studies of this coastal region have reported signs of seawater intrusion, salt pan and industrial activity together with natural weathering process. To have a holistic picture of geochemical processes in the entire district, a total of 135 groundwater samples were collected and analyzed for major cations and anions. The geochemical parameters were compared with world and Indian standards and it was found that most samples are unsuitable for drinking purpose. The geochemical facies of the groundwater showed Na–Cl as the dominant water type indicating the saline nature of the groundwater. Chadda’s plots show that most of the samples fall in the Na–Cl type of water due to seawater intrusion. The samples were classified with parameters like sodium absorption ratio, residual sodium carbonate, total hardness, chloride, index to base exchange, electrical conductivity and facies to determine their suitability for irrigation purpose. It was inferred that the samples falling along the coast are not suitable for the irrigation purpose. The seawater-mixing percentage indicates that strong mixing was observed in the near shore and at the proximity of the salt pan. The permanent hardness was predominant in all the samples compared to the carbonate hardness reducing its domestic usability

Hormonal and Nutritional Changes in the Flavedo Regulating Rind Color Development in Sweet Orange [Citrus sinensis (L.) Osb.]

The objective of this research was to determine the changes in the levels of endogenous gibberellins GA(1) and GA(4), abscisic acid (ABA), and ethylene during fruit coloring of on-tree fruits of sweet orange. The time course of carbohydrates and nitrogen content in the flavedo prior to fruit color break and during peel ripening were also studied. To identify nutritional and hormonal changes in the fruit, 45 days before fruit color break the peduncles of 15-30 fruits per tree of 'Washington' navel, 'Navelate,' and 'Valencia Delta Seedless' sweet orange, located in single-fruited shoots, were girdled to intercept phloem transport. A set of 15-30 fruits per tree remained intact on the peduncle for control. Girdling significantly delayed fruit coloration for more than 2 months; the delay paralleled higher GA(1) and GA(4) concentrations in the flavedo and retarded the rise of ABA concentration prior to color break. Girdling also reduced carbohydrate concentrations and increased N concentrations in the flavedo compared to control fruits; no ethylene production was detected. Therefore, in sweet orange, fruit changes color by reducing active gibberellin concentrations in the flavedo, which are involved in regulating sugars and ABA accumulation and in reducing N fraction concentration as rind color develops. This was demonstrated in vivo without removing the fruit from the tree. Comparable results were obtained with experiments carried out over four consecutive years in two countries (Spain and Uruguay).This study was partially supported by the Programme ALssan, EU Programme of High Level Scholarships for Latin America (IN E03D15012UR), and Comision Sectorial de Investigacion Cientifica (Univ. de la Republica, Uruguay). The authors thank Dra. 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