Groundwater residence time and movement in the Maltese islands – A geochemical approach

Abstract

12The Maltese Islands are composed of two limestone aquifers, the Upper and Lower

An isotope study of the sources of nitrate in Malta’s groundwater

“…In agreement with the hydrological settings, tritium and SF 6 data suggest that the perched aquifers contain relatively young groundwater (Bakalowicz and Mangion, 2003;Stuart et al, 2010) This was confirmed by the presence of E. Coli, often at high concentrations, in 10 of the 12 perched aquifer sources sampled in this study (Stuart et al, 2010). The major ion chemistry is predominantly Ca + Mg bicarbonate, but also with high concentrations of Na and Cl (median ca.…”

“…Since the islands rise to a maximum altitude of 239 m above sea level, the MSL aquifers are overlain by a thick unsaturated zone, typically from 40 to 120 m for boreholes sampled in this study (Stuart et al, 2010). In western parts of Malta, and over a large area of Gozo this zone is capped by the Blue Clay and Upper Coralline Limestone.…”

“…250 mg Cl L -1 ) in ratios close to that of seawater (Table 1). This is presumed to derive mainly from sea salts in rainfall concentrated by evaporation (Stuart et al, 2010), or by minor sea water contamination where perched aquifers are close to sea level (Sapiano et al, 2006).…”

“…As part of Malta's programme to address this problem, the British Geological Survey and the Malta Resources Authority conducted a preliminary study on the identification of the sources of nitrate contamination in groundwater in Malta. Geochemical aspects of groundwater movement are reported elsewhere (Stuart et al, 2010); the present work reports on the results of the isotope study of nitrate.…”

Residence time, mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone

“…The BMM applied in this paper is usually appropriate for multi-layers aquifers (La Salle et al, 2012;Stuart et al, 2010). This model reveals the presence of "young" and "old" water bodies, in agreement with groundwater temperatures and only slightly influenced by the seasonal surface atmospheric conditions and by the tritium concentrations below 1-2 TU linked to an important ratio of pre-1950's water.…”