Biogeochemistry of newly created riparian wetlands: Evaluation of water quality changes and soil development

Biogeochemical development of created riparian wetlands was investigated in full-scale systems and replicated mesocosms. Water quality changes and soil development were evaluated over two years in two newly created freshwater marshes (1 ha each) with similar hydrology. One wetland was planted; the other received no planted vegetation. Wetlands received pumped river water impacted by nonpoint source pollution. Hydrologic budgets were dominated by pumped surface flows (mean inflow = 1480 m{dollar}sp3{dollar}/day). Two floods accounted for 32% of inflow in 1995. Both wetlands significantly decreased turbidity (62 to 27 NTU) and increased dissolved oxygen (9 to 11 mg L{dollar}sp{lcub}-1{rcub}{dollar}).; Inflow soluble reactive phosphorus (SRP) and total phosphorus (TP) concentrations (17 {dollar}pm{dollar} 3 and 169 {dollar}pm{dollar} 11 {dollar}mu{dollar}g P/L) were significantly higher (p {dollar}<{dollar} 0.05) than outflow concentrations (SRP: 5 {dollar}pm{dollar} 1 and 6 {dollar}pm{dollar} 1 {dollar}mu{dollar}g P/L; TP: 69 {dollar}pm{dollar} 8 and 74 {dollar}pm{dollar} 9 {dollar}mu{dollar}g P/L for planted and unplanted wetlands, respectively). Mean removal rates were 1.0 g P m{dollar}rmsp{lcub}-2{rcub} yrsp{lcub}-1{rcub}{dollar} for SRP and 5.4 g P m{dollar}rmsp{lcub}-2{rcub} yrsp{lcub}-1{rcub}{dollar} for TP and did not differ significantly between wetlands (p {dollar}<{dollar} 0.05). Approximately 40% of TP mass removal occurred during two floods. A conservative tracer (Cl) indicated limited dilution. Flow and concentration did not affect P removal which was loading-limited and seasonal.; Soil submergence resulted in physicochemical changes indicating hydric soil genesis. Deposition and decomposition of algal mats affected biogeochemical development, resulting in muck layers (1-15 cm) in both wetlands. Soil organic C increased significantly to 2.21 {dollar}pm{dollar} 0.11% for planted and 1.88 {dollar}pm{dollar} 0.11% for unplanted wetlands and differed significantly (p {dollar}<{dollar} 0.05). Retention of allochthonous sediments and P, coupled with autochthonous production by algae, increased soil Ca, Fe, P and C. Planted vegetation development demonstrated little effect on biogeochemistry over the first two years.; In 20 mesocosms (0.9 m{dollar}sp2{dollar}), soil effects (hydric or non-hydric) on wetland development were studied. Submergence resulted in initial convergence of soil physicochemical attributes. Growth and elemental composition of Scirpus tabernaemontani exhibited no distinct differences due to soil type, although the hydric soil exhibited a viable seed bank.