A methodology for the assessment of accidental copper pollution using the aquatic moss Rhynchostegium riparioides

Laboratory experiments using aquatic mosses were carried out in order to develop strategies for the monitoring of accidental metal discharges into rivers. A flow-through system was used to simulate 24 different accidental discharges of Cu by combining 4 exposure intensities (42, 82, 178 and 342 μg L−1) and 6 durations (1, 6, 12, 24, 72 and 168 hours). Exposure to Cu was followed by a 10-day depuration phase. Uptake kinetics can be described by non linear equations. Most of the Cu accumulation in the mosses occurred in the first 96 hours and reached an equilibrium state within 168 hours. All depuration kinetics can be described by decreasing logarithmic equations. The extent of Cu release from the mosses depends on the maximum Cu levels reached at the end of the uptake phase. Copper levels in mosses during the depuration phase reached an equilibrium state and remained higher than the initial level. Specific sampling strategies and calculations allow us to estimate both the mean aqueous Cu concentration during the discharge and the duration of exposure if the mosses are sampled before the aqueous Cu concentration starts to decrease. Retrospective assessment of the maximum Cu level reached in the mosses during the Cu discharge is also possible if the mosses are sampled during the first 10 days of the depuration phase while the aqueous Cu concentration is returning to the background level.