In this study, we focus on the behavior of geogenic, toxic trace elements, particularly As, Cs, Cd, and Pb, during their transportation in two rivers for irrigation commonly used in monsoon Asia; one river originates from an active volcano, Mt. Asama, and the other originates from a currently inactive volcano, Yatsugatake Mountains in Nagano, Japan. These rivers were investigated to understand the role of river water as a pollutant of rice and other aquatic plants (via irrigation) and aquatic animals. The results indicated that the behavior of toxic trace elements in river water are likely controlled by their interactions with particulate Fe, Al, and Ti compounds. The majority of Pb and Cd is transported as particulate matter with Fe, Al, and Ti, while the majority of As is transported in the dissolved form, predominantly as arsenate, with low abundance of particulate matter. Cs is transported either as the dissolved form or as particulate matter in both rivers. The investigated elements are transported in the rivers as particulate and dissolved forms, and the ratio of these forms is controlled by the pH and presence of particulate Fe, Al, and Ti phases in the river water. With respect to Cs in both rivers, the parameter governing the concentration and transportation of Cs, in the bimodal form (i.e., particulate and dissolved forms), through the river possibly shifts from sorption to pH by particulate Fe–Al–Ti, according to the abrupt increase in the concentration of Cs in the river. The chemical attraction of particulate Fe–Al–Ti for Cs is weaker than that for Pb and Cd, indicating that the lower electronegativity of Cs weakens the chemical attraction on a colloid for the competitive sorption with the other trace elements. The different relationships between As and Fe in the river and in the irrigation water and soil water, as well as those in paddy rice, suggested that As in paddy rice is not directly derived from As in the irrigation water from the river under flooding.

在这项研究中，我们着眼于在季风化亚洲普遍使用的两条灌溉河流中运输的成因，有毒微量元素，特别是As，Cs，Cd和Pb的行为。一条河流起源于一座活火山。浅间（Asama）和其他源于目前不活跃的火山，即日本长野县的八岳山脉（Yatsugatake Mountains）。对这些河流进行了调查，以了解河水作为水稻和其他水生植物（通过灌溉）和水生动物的污染物的作用。结果表明，河水中有毒微量元素的行为可能受其与颗粒状Fe，Al和Ti化合物的相互作用控制。大多数Pb和Cd与Fe，Al和Ti一起作为颗粒物运输，而大多数As以溶解形式（主要是砷酸盐）运输，颗粒物含量低。Cs以溶解形式或颗粒物质形式在两条河流中运输。被调查的元素以颗粒形式和溶解形式在河流中运输，这些形式的比例受pH值以及河流水中颗粒状Fe，Al和Ti相的存在控制。关于两条河流中的Cs，控制Cs浓度和以双峰形式（即颗粒形式和溶解形式）通过河流的参数可能由Fe-Al-Ti颗粒从吸附转变为pH，根据河流中的Cs浓度突然增加。Fe-Al-Ti颗粒对Cs的化学吸引力弱于对Pb和Cd的化学吸引力，表明较低的Cs电负性削弱了对胶体的化学吸引力，从而与其他微量元素发生竞争性吸附。河流，灌溉水和土壤水以及水稻中As和Fe之间的关系不同，这表明水稻中的As不是直接来自洪水淹没的河流灌溉水中的As。