The worldwide consumption of bottled water has experienced an annual increase of 5.5% since 2004 and different authors have speculated that this is due to beliefs of superior flavor and health qualities of bottled water over tap water. The content of certain minerals varies by 2 to 6 orders of magnitude between bottled water brands. The major cations Ca, Mg, Na, and K can be found in concentrations up to 730, 450, 1900, and 270 mg/L but are usually below 100 mg/L; higher concentrations have only been found in some European and North American bottled water samples. The dominating anions are HCO 3 − , Cl − , and SO 4 2− . Sensory evaluation and description of water strongly depend on personal preferences and sensitivities. The major cations can be detected by taste in concentrations down to 2 digits in the mg/L range; however, the intensity depends on which anions are present. Most cations add different degrees of salty, sour, sweet, and bitter tastes to water depending on their concentrations. Al, Ca, Cu, Fe, Mg, and Zn may introduce metallic, astringent, and irritative sensations and for Fe and Cu also retro-nasal odors may influence the metallic sensation. Drinking water with total dissolved solids in the range of 100 to 400 mg/L results in good sensory quality. Known offflavor problems originate from by-products of ozonation and leaching of organics from bottling material which may also be enhanced by ozonation, and microbial by-products from the source water such as geosmin and 2-methylisoborneol, lubricants, or cleaning agents used in the bottling industry.

Mobility and bioavailability of nickel (Ni) in soil strongly depends on the interaction between Ni(II), ligands, and sorbents like organic matter and minerals. Sorption of Ni(II) and Ni(II)-citrate complexes to goethite and montmorillonite was examined in batch experiments with and without citrate as ligand in the pH range pH 4-7.5. Without citrate, montmorillonite shows higher Ni sorption than goethite. Citrate strongly decreases Ni sorption to montmorillonite; in presence of 100 microM citrate goethite becomes a stronger Ni sorbent than montmorillonite. Ni and citrate sorption was modeled successfully using the diffuse double layer model with the following reactions: Goethite: 3 [triple bond]FeOH + Citrate(3-) + 3H+ <=> [triple bond] Fe3Citrate + 3H2O, [triple bond]FeOH + Ni2+ <=> [triple bond] FeONi + H+ and 2 [triple bond] FeOH + Citrate(3)- + Ni2+ <=> [triple bond] FeONiCitrate(2-) + H+. Montmorillonite: 2X- + Ni2+ <=> X2Ni and [triple bond] AIOH + Ni2+ <=> AIONi+ + H+. Sorption of Ni to a mixture of goethite and montmorillonite could be calculated by use of reactions and constants for the monomineral systems. Without citrate, the sorbed amount of Ni per mass unit in the mixture can be found as a simple average of sorption to the two single sorbents, while in presence of citrate Ni sorption to montmorillonite is strongly influenced by citrate sorption to goethite.

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Extensive aquatic or semi-aquatic production of water spinach (Ipomoea aquatica Forssk.) for human consumption takes place in Southeast Asia. The aim of this study was to assess the concentrations of 38 elements in soil and water spinach cultivated under different degrees of wastewater exposure in Hanoi, Vietnam. The results showed no effect of wastewater use on the overall element concentrations in soil and water spinach. Mean soil concentrations for selected potentially toxic elements at the studied field sites had the following ranges 9.11-18.7 As, 0.333-0.667 Cd, 10.8-14.5 Co, 68-122 Cr, 34.0-62.1 Cu, 29.9-52.8 Ni, 32.5-67.4 Pb, 0.578-0.765 Tl and 99-189 Zn mg kg(-1) dry weight (d.w.). In all samples Cd, Pb and Zn soil concentrations were below the Vietnamese Guideline Values (TCVN 7209-2002) for agricultural soils whereas As and Cu exceeded the guideline values. Maximum site element concentrations in water spinach were 0.139 As, 0.032 Cd, 0.135 Cr, 2.01 Cu, 39.1 Fe, 57.3 Mn, 0.16 Ni, 0.189 Pb and 6.01 Zn mg kg(-1) fresh weight (f.w.). The site and soil content of organic carbon were found to have high influence on the water spinach element concentrations whereas soil pH and the total soil element concentrations were of less importance. The estimated average daily intake of As, Cd, Cu, Fe, Pb and Zn for adult Vietnamese consumers amounts to <11% of the maximum tolerable intake proposed by FAO/WHO for each element. It is assessed that the occurrence of the investigated elements in water spinach will pose low health risk for the consumers.

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