Obeidy Chelsea S, Polizzotto Matthew L
Department of Earth Sciences, University of Oregon, 100 Cascade Hall, 1272 University of Oregon, Eugene, OR 97403-1272, United States.
Geoderma. 2024 Feb;442. doi: 10.1016/j.geoderma.2024.116784. Epub 2024 Jan 25.
Weathering processes are recognized as drivers of soil and water resource sustainability, but how pedogenesis stage impacts contaminant reactivity and mobility in soils has been minimally investigated. The primary goal of this study was to quantify how soil development influences contaminant reactivity. To achieve this goal, soils from two depths (30 and 100 cm) across a chronosequence (ages 3.5, 20, 69, 140, 200, and 908 ky) in the Oregon Coast Range were subjected to arsenic (As) adsorption isotherms, with As removal from solution serving as a proxy for soil-contaminant reactivity. Langmuir models were applied to isotherm data to quantify relationships between contaminant retention capacity, soil age and soil physicochemical properties, and data revealed that 20 ky soils from a 30-cm-depth had the greatest affinity for As sorption (8,474.5 mg kg). Chemical extractions revealed that amorphous (oxy)hydroxides were the dominant mineral phases governing As sorption, even in the presence of abundant crystalline oxides. Micro-X-ray fluorescence spectroscopy revealed a strong spatial correlation between As and Fe in reacted soils. The abundance of amorphous minerals within soils is controlled by the balance between their production from weathering of primary minerals and their loss from ripening to crystalline minerals, and because the mode, extent and minerals governing contaminant sorption determine solid-aqueous phase partitioning, this knowledge will assist in improving models for predicting Critical Zone processes that govern the sustainability of soil and water quality.
风化过程被认为是土壤和水资源可持续性的驱动因素，但成土阶段如何影响土壤中污染物的反应性和迁移性却鲜有研究。本研究的主要目标是量化土壤发育如何影响污染物反应性。为实现这一目标，对俄勒冈海岸山脉一个时间序列（年龄分别为3.5、20、69、140、200和908千年）中两个深度（30厘米和100厘米）的土壤进行了砷（As）吸附等温线实验，用溶液中As的去除作为土壤 - 污染物反应性的指标。将朗缪尔模型应用于等温线数据，以量化污染物保留能力、土壤年龄和土壤理化性质之间的关系，数据显示，30厘米深度处20千年的土壤对As吸附具有最大亲和力（8474.5毫克/千克）。化学提取表明，即使存在大量结晶氧化物，无定形（羟基）氧化物仍是控制As吸附的主要矿物相。微X射线荧光光谱显示反应后土壤中As和Fe之间存在很强的空间相关性。土壤中无定形矿物的丰度受原生矿物风化产生与向结晶矿物熟化损失之间平衡的控制，并且由于控制污染物吸附的方式、程度和矿物决定了固 - 水相分配，这一知识将有助于改进预测控制土壤和水质可持续性的关键带过程的模型。
