The oxidized Ag(111) surface has been studied by a combination of experimental and theoretical methods, scanning tunneling microscopy, x-ray photoelectron spectroscopy, and density functional theory. A large variety of different surface structures is found, depending on the detailed preparation conditions. The observed structures fall into four classes: (a) individually chemisorbed atomic oxygen atoms, (b) three different oxygen overlayer structures, including the well-known p(4x4) phase, formed from the same Ag₆ and Ag₁₀ building blocks, (c) a c(4x8) structure not previously observed, and (d) at higher oxygen coverages structures characterized by stripes along the high-symmetry directions of the Ag(111) substrate. Our analysis provides a detailed explanation of the atomic-scale geometry of the Ag₆/Ag₁₀ building block structures and the c(4x8) and stripe structures are discussed in detail. The observation of many different and co-existing structures implies that the O/Ag(111) system is characterized by a significantly larger degree of complexity than previously anticipated, and this will impact our understanding of oxidation catalysis processes on Ag catalysts

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The interaction of water with solid surfaces is key to a wide variety of industrial and natural processes. However, the basic principles that dictate how stable and in which state (intact or dissociated) water will be on a given surface are not fully understood. Towards this end, we have used density functional theory to examine water monomer adsorption on the (001) surfaces of a broad range of alkaline earth oxides, alkaline earth sulfides, alkali fluorides, and alkali chlorides. Some interesting general conclusions are arrived at: (i) on all the surfaces considered only a few specific adsorption structures are favoured; (ii) water becomes more stable upon descending the oxide and fluoride series but does not vary much upon going down the chloride and sulfide series; (iii) water is stabilised both by an increase in the lattice constant, which facilitates hydrogen bonding to the substrate, and by the flexibility of the substrate. These are also factors that favour water dissociation. We hope that this study is of some value in better understanding the surface science of water in general, and in assisting in the interpretation and design of future experiments.

Surface water samples were collected from the sampling sites throughout the Xiangjiang River for investigating spatial variation, risk assessment and source identification of the trace elements. The results indicated that the mean concentrations of the elements were under the permissible limits as prescribed by guidelines except arsenic (As). Based on the health risk indexes, the primary contributor to the chronic risks was arsenic (As), which was suggested to be the most important pollutant leading to non-carcinogenic and carcinogenic concerns. Individuals, who depend on surface water from the Xiangjiang River for potable and domestic use, might be subjected to the integrated health risks for exposure to the mixed trace elements. Children were more sensitive to the risks than the adults, and the oral intake was the primary exposure pathway. Besides, multivariate statistical analyses revealed that arsenic (As), cadmium (Cd), lead (Pb), selenium (Se), and mercury (Hg) mainly derived from the chemical industrial wastewaters and the coal burning, and zinc (Zn) copper (Cu) and chromium (Cr) mainly originated from the natural erosion, the mineral exploitation activities, and the non-point agricultural sources. As a whole, the upstream of the Xiangjiang River was explained as the high polluted region relatively.

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