2.3.2. Wave Flume Experiment Processes

The wave flume experiment included three sequential stages, namely static diffusion stage (Stage I), 7 cm wave height (Stage II), and 13.5 cm wave height (Stage III). Table 1 shows the wave parameters and sampling intervals in the experiments.


**Table 1.** Wave parameters and sampling intervals in the wave flume experiments.

In Stage I, the overlying water was left still for 40 h and the sediments remained in a consolidation state. Stages II and III were the wave action stages, with the wave actions lasted for 180 min in each stage.

In Stage I, water samples were collected every 8 h using self-design water sampling devices at 5 cm and 20 cm above the center line of sediments, namely at water depths of 30 cm and 45 cm (Figure 3). Each water sample was 50 mL in volume. Since the volume of water samples were relatively small, standard seawater was not replenished into the wave flume. Three parallel samples were collected at each sampling point. Nitric acid was added to the samples, which were stored at low temperatures (4 ◦C) for analysis of dissolved Cu concentrations. During Stages II and III, after the wave height was steady, water samples were collected every 10 min for the first 60 min and every 20 min for the last 120 min. The sampling points and method were the same as that in Stage I.

At the end of each stage, a polyvinyl chloride (PVC) tube was inserted in the sediment at the central position of the sediment tank to collect columnar samples of sediments (Figure 3). These PVC tubes were remained in the sediment tank until the end of Stage III. All sediment columnar samples were incised into 2 cm segments for the analysis of Cu concentrations at different depths of the sediments.
