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Mid-estuary DS docks Preston docks US Preston Site

Fig. 9.9. TWA cadmium concentrations measured using the Chemcatcher passive sampler at various sites along the Ribble estuary. Data for the mid-estuary and DS docks sites are from a single sampler and data shown for Preston docks and upstream of Preston are the mean of two measurements (DS: downstream; US: upstream).

Mid-estuary DS docks Preston docks US Preston Site

Fig. 9.9. TWA cadmium concentrations measured using the Chemcatcher passive sampler at various sites along the Ribble estuary. Data for the mid-estuary and DS docks sites are from a single sampler and data shown for Preston docks and upstream of Preston are the mean of two measurements (DS: downstream; US: upstream).

The standard monitoring by the Environment Agency for England and Wales was conducted on two occasions during the trial. Cadmium concentrations were found below limits of detection (LOD: 0.04 mgLr1) for all sites monitored. This is in agreement with concentrations measured with Chemcatcher and emphasises the advantage of in situ time-integrative sampling over spot sampling in term of detection limits, since useful data that could be used in determining trends were obtained. This contrasts with the spot sampling where only categorical information (not detected) was obtained.

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