What needs to be clarified
Compare metal content in comparable sediment settings and assess spatial differences without prematurely assigning a source.
Materials to prepare
- Separate georeferenced surface-sediment samples
- Map of outfall, flow and comparison points
- Metal, moisture, organic-matter and grain-size results
What to compare
Use replicate points on comparable beds, record sampled thickness and avoid fine-particle loss. Check equipment cleanliness and controls. Compare metal concentrations on the same mass basis, considering grain size and organics as possible explanations.
Possible outcome of the analysis
A sampling map and comparable-results table may describe uncertainty and identify further locations needed to test an outfall-influence hypothesis.
Limits of the conclusions
Spatial differences prove neither a unique source nor ecological damage. Findings concern sampled layers and period; normalization cannot remove every difference.