Data from: Mitigating acid sulfate soil development in sediment addition projects through application of sediment amendments

Sediment addition is an increasingly common strategy to promote coastal
resilience where sediment is added to salt marsh surfaces to increase
elevation and prevent marsh loss. Added sediments are typically dredged
materials from marine environments that may become acidic when exposed to
air because of their high reduced sulfide levels, known as potential acid
sulfate soils (PASS). Low soil pH inhibits plant growth and can delay
ecosystem recovery after sediment addition. We used a laboratory soil core
experiment to evaluate how a range of amendments altered pH (mulch,
crushed shells, pelletized lime, and recycled concrete), and a field study
to examine the effects of recycled concrete. We found both shells (7.46 ±
0.22; mean ± std dev) and concrete (laboratory: 8.24 ± 0.32; field: 8.15 ±
0.55) increased pH relative to adding unamended sediment (laboratory: 7.33
± 0.35; field: 7.21 ± 0.45). Environmental context is likely important for
sediment additions and even PASS may not become acidic in flooded, low
marsh environments. Under more oxidized conditions, particularly in
higher-elevation marsh or when deeper layers of sediment are added,
recycled concrete or crushed shells are potential amendments to neutralize
acidity. Sediment amendments may also affect other ecosystem responses,
including water chemistry and greenhouse gas emissions. We found that
concrete amendments lowered ferrous iron concentrations and decreased
carbon dioxide emissions compared to adding unamended sediment. Additional
testing of amendments under diverse environmental conditions and at field
scales would further our understanding of the effectiveness and
feasibility of amending soils during sediment additions.