Heavy metals release from contaminated sediments is one of the most important chemical processes affecting overlying water quality in river, lake, and ocean. The objective of this study was to determine the leaching properties, kinetic rate, and leaching amount of zinc (Zn) and cadmium (Cd) from the river sediment contaminated by gold mining. Speciation of Zn and Cd in the sediments was extracted by a modified BCR extraction procedure. Release kinetics of Zn and Cd were studied by a simulated leaching experiment using a stirred-flow reactor and a two-site equilibrium-kinetic model. The sediments we studied were significantly contaminated by Zn (620–5878 mg kg⁻¹) and Cd (2–67 mg kg⁻¹), and both have high content of weak acid extractable forms. There were much more smaller particles on the surface of sediment JH01 and JH02 than sediment JH03 and JH04. The two-site equilibrium-kinetic model fits the release data of Zn and Cd well, and it was demonstrated as an effective tool to describe the kinetic release of Zn and Cd from river sediments. Kinetic rates obtained from curve fitting showed large variation among sediments indicating different reaction mechanisms. The rapid release stage (before the second stop-flow) of Zn and Cd was controlled both by the equilibrium sites and the kinetic sites, while the slow release stage (after the second stop-flow) was mainly controlled by the kinetic sites. The total leaching amount of Zn and Cd in JH01 (27.1 mg kg⁻¹, 0.4 mg kg⁻¹), JH02 (474 mg kg⁻¹, 7.5 mg kg⁻¹), JH03 (320 mg kg⁻¹, 7.6 mg kg⁻¹), and JH04 (52.4 mg kg⁻¹, 2.0 mg kg⁻¹) demonstrated that large amount of Zn and Cd in sediments can be leached into solution. Thus, effective measures should be taken to prevent leaching of heavy metals from river sediment.

从受污染的沉积物中释放出的重金属是影响河流，湖泊和海洋中上层水质的最重要的化学过程之一。这项研究的目的是确定金矿污染的河流沉积物中锌（Zn）和镉（Cd）的浸出特性，动力学速率和浸出量。通过改进的BCR提取程序提取了沉积物中锌和镉的形态。通过使用搅拌流反应器和两点平衡动力学模型的模拟浸出实验研究了Zn和Cd的释放动力学。我们研究的沉积物被锌（620-5878 mg kg ^-1）和镉（2-67 mg kg ^-1）严重污染。），并且都具有高含量的弱酸可提取形式。与沉积物JH03和JH04相比，沉积物JH01和JH02表面的颗粒小得多。两点平衡动力学模型很好地拟合了Zn和Cd的释放数据，并被证明是描述Zn和Cd从河流沉积物中动态释放的有效工具。从曲线拟合获得的动力学速率显示出沉积物之间的较大差异，表明不同的反应机理。Zn和Cd的快速释放阶段（第二停止流之前）由平衡位点和动力学位点控制，而缓慢释放阶段（第二停止流之后）主要由动力学位点控制。Zn和Cd的在JH01（总浸出量27.1毫克千克^-1，0.4毫克千克^-1），JH02（474毫克千克^-1，7.5毫克千克^-1），JH03（320毫克千克^-1，7.6毫克千克^-1），和JH04（52.4毫克千克^-1，2.0毫克千克^-1）证明了大沉积物中大量的锌和镉可以浸出到溶液中。因此，应采取有效措施防止河流沉积物中重金属的浸出。