Downstream hydrochemistry and irrigation water quality of the Syr Darya, Aral Sea Basin, South Kazakhstan

New hydrochemical measurements from the Syr Darya provide insights into factors affecting the composition and quality of a major freshwater source replenishing the Aral Sea. This river is heavily used for power and irrigation and crosses territories of four Central Asia republics. It is intensely managed, draining several major tributaries, many reservoirs, and numerous irrigation distribution systems and canals. Analysis of seasonal changes in dissolved ion concentrations using geochemical diagrams, elemental ratios, statistical correlation, and equilibrium modeling allowed the characterization of mineral formation processes that control the dissolved chemical composition. Measured water hydrochemistry and composition type differs substantially from previous reports from the upper reaches of the Syr Darya in Kyrgyzstan. Element ratios, statistical correlation, and the presence of NO3- and NO2- suggest that the downstream trend of increasing total dissolved solids (TDS) from Zhetysay city to the Aral Sea in June is controlled by evaporation–crystallization processes, which contribute to the river dissolved load through soil runoff and return irrigation waters following leaching of secondary salts. Downstream sample composition during the growing season shows significant changes in magnesium-to-calcium ratios in the river water. Elevated magnesium levels in Syr Darya waters may pose a problem to sustainable uses for irrigation

Гидротермальный синтез моноструктурного LaPO4: морфология и структура

Область применения материалов на основе ортофосфата лантана (LaPO4), в том числе наноматериалов, в последнее время постоянно расширяется. Высокий уровень механических свойств и совместимость со многими оксидами позволяют рассматривать возможность ис­пользования ортофосфата лантана в качестве компонента композиционного материала кон­струкционного назначения. Такое применение особенно перспективно при использовании наночастиц с квазиодномерной морфологией (наностержней). Большая изоморфная ёмкость фазы на основе LaPO4 по отношению к щёлочноземельным ионам, ионам лантаноидов и акти­ноидов, высокая химическая и радиационная стойкость делают перспективным использова­ние этого соединения в качестве матрицы для иммобилизации радиоактивных отходов. В работе рассматривается возможность получения ортофосфата лантана (LaPO4) гидро­термальным методом. Приведены результаты исследования влияния рН, температуры и вре­мени обработки и гидротермального синтеза на морфологию и структуру моноструктурного фосфата лантана. Установлено, что с ростом рН меняется морфология фосфата и размеры кристаллитов, при этом наблюдается переход кристаллической структуры с гексагональной в моноклинную

Downstream hydrochemistry and irrigation water quality of the Syr Darya, Aral Sea Basin, South Kazakhstan

New hydrochemical measurements from the Syr Darya provide insights into factors affecting the composition and quality of a major freshwater source replenishing the Aral Sea. This river is heavily used for power and irrigation and crosses territories of four Central Asia republics. It is intensely managed, draining several major tributaries, many reservoirs, and numerous irrigation distribution systems and canals. Analysis of seasonal changes in dissolved ion concentrations using geochemical diagrams, elemental ratios, statistical correlation, and equilibrium modeling allowed the characterization of mineral formation processes that control the dissolved chemical composition. Measured water hydrochemistry and composition type differs substantially from previous reports from the upper reaches of the Syr Darya in Kyrgyzstan. Element ratios, statistical correlation, and the presence of NO3- and NO2- suggest that the downstream trend of increasing total dissolved solids (TDS) from Zhetysay city to the Aral Sea in June is controlled by evaporation–crystallization processes, which contribute to the river dissolved load through soil runoff and return irrigation waters following leaching of secondary salts. Downstream sample composition during the growing season shows significant changes in magnesium-to-calcium ratios in the river water. Elevated magnesium levels in Syr Darya waters may pose a problem to sustainable uses for irrigation. HIGHLIGHTS Water composition transitions from Ca–Mg–HCO3 to Ca–Mg–SO4–Cl to Na–SO4–Cl downstream the Syr Darya.; Seasonal and downstream differences in composition suggest that irrigation water inputs are likely controlled by different mineral equilibria.; Water quality indices showed that, generally, Syr Darya water is suitable for irrigation.