Figure 4
From: Do freshwater mussel shells record road-salt pollution?
High-resolution Na/Ca and δ18O values along the prismatic layer in shell Ck-1.
Annual growth lines are represented by vertical bars. Growth lines occur at maximum δ18O values (winter) confirming they are annual winter growth checks. Maxima δ18O values at 1.4 and 13 mm are assumed to be annual with indistinct growth lines. Shell growth and thus time is from right to left. Analytical precision is better than ±0.02 mmol/mol for Na/Ca ratios and ±0.1‰ for δ18O values.
