Modelling to bridge many boundaries: the Colorado and Murray-Darling River basins

Increasing pressure on shared water resources has often been a driver for the development and utilisation of water resource models (WRMs) to inform planning and management decisions. With an increasing emphasis on regional decision-making among competing actors as opposed to top-down and authoritative directives, the need for integrated knowledge and water diplomacy efforts across federal and international rivers provides a test bed for the ability of WRMs to operate within complex historical, social, environmental, institutional and political contexts. This paper draws on theories of sustainability science to examine the role of WRMs to inform transboundary water resource governance in large river basins. We survey designers and users of WRMs in the Colorado River Basin in North America and the Murray-Darling Basin in southeastern Australia. Water governance in such federal rivers challenges inter-governmental and multi-level coordination and we explore these dynamics through the application of WRMs. The development pathways of WRMs are found to influence their uptake and acceptance as decision support tools. Furthermore, we find evidence that WRMs are used as boundary objects and perform the functions of ‘boundary work’ between scientists, decision-makers and stakeholders in the midst of regional environmental changes

Atmospheric iodine levels influenced by sea surface emissions of inorganic iodine

Naturally occurring bromine- and iodine-containing compounds substantially reduce regional, and possibly even global, tropospheric ozone levels. As such, these halogen gases reduce the global warming effects of ozone in the troposphere, and its capacity to initiate the chemical removal of hydrocarbons such as methane. The majority of halogen-related surface ozone destruction is attributable to iodine chemistry. So far, organic iodine compounds have been assumed to serve as the main source of oceanic iodine emissions. However, known organic sources of atmospheric iodine cannot account for gas-phase iodine oxide concentrations in the lower troposphere over the tropical oceans. Here, we quantify gaseous emissions of inorganic iodine following the reaction of iodide with ozone in a series of laboratory experiments. We show that the reaction of iodide with ozone leads to the formation of both molecular iodine and hypoiodous acid. Using a kinetic box model of the sea surface layer and a one-dimensional model of the marine boundary layer, we show that the reaction of ozone with iodide on the sea surface could account for around 75% of observed iodine oxide levels over the tropical Atlantic Ocean. According to the sea surface model, hypoiodous acid - not previously considered as an oceanic source of iodine - is emitted at a rate ten-fold higher than that of molecular iodine under ambient conditions

Elucidating mechanisms of chlorine toxicity: reaction kinetics, thermodynamics, and physiological implications

Industrial and transport accidents, accidental releases during recreational swimming pool water treatment, household accidents due to mixing bleach with acidic cleaners, and, in recent years, usage of chlorine during war and in acts of terror, all contribute to the general and elevated state of alert with regard to chlorine gas. We here describe chemical and physical properties of Cl2 that are relevant to its chemical reactivity with biological molecules, including water-soluble small-molecular-weight antioxidants, amino acid residues in proteins, and amino-phospholipids such as phosphatidylethanolamine and phosphatidylserine that are present in the lining fluid layers covering the airways and alveolar spaces. We further conduct a Cl2 penetration analysis to assess how far Cl2 can penetrate the surface of the lung before it reacts with water or biological substrate molecules. Our results strongly suggest that Cl2 will predominantly react directly with biological molecules in the lung epithelial lining fluid, such as low-molecular-weight antioxidants, and that the hydrolysis of Cl2 to HOCl (and HCl) can be important only when these biological molecules have been depleted by direct chemical reaction with Cl2. The results from this theoretical analysis are then used for the assessment of the potential benefits of adjuvant antioxidant therapy in the mitigation of lung injury due to inhalation of Cl2 and are compared with recent experimental results