|REDDY, GUDIPORAM - North Carolina Agricultural And Technical State University|
|RACZKOWSKI, CHARLES - North Carolina Agricultural And Technical State University|
|CYRUS, JOHNSELY - North Carolina Agricultural And Technical State University|
Submitted to: Water Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/15/2016
Publication Date: 2/29/2016
Citation: Reddy, G., Raczkowski, C.W., Cyrus, J.S., Szogi, A.A. 2016. Carbon sequestration in surface flow constructed wetland after 12 years of swine wastewater treatment. Water Science and Technology. 73(10):2501-2508. doi:10.2166/wst2016.112.
Interpretive Summary: Constructed wetlands used for the treatment of swine wastewater have the potential to sequester significant amounts of carbon (C). In past studies, we evaluated the treatment efficiency of wastewater in a marsh-pond-marsh design wetland system planted to a mixture of cattails and American bulrush. The functionality of this system was highly dependent on soil C content and organic matter turnover rates. To better understand system performance and C dynamics, we measured plant dry matter, decomposition rates, and soil C fractions. On average, 73% of plant litter was decomposed during a 270 day period at a decay rate of 0.0052 g/day. Wastewater was the major C source in the pond section while in the marsh area C originated from both wastewater and decomposing plant biomass. As a result, more soil C was found in the marsh area than in the pond section. The soil C fractions measured in our study proved that these wetlands can be large sinks of stable C forms.
Technical Abstract: Constructed wetlands used for the treatment of swine wastewater may potentially sequester significant amounts of carbon. In past studies, we evaluated the treatment efficiency of wastewater in marsh-pond-marsh design wetland system. The functionality of this system was highly dependent on soil carbon content and organic matter turnover rate. To better understand system performance and carbon dynamics, we measured plant dry matter, decomposition rates and soil carbon (C) fractions. Plant litter decomposition rate was 0.0052 g/day (±0.00119 g/day) with an estimated half-life of 133 days. The detritus layer accumulated over the soil surface had much more humin than other C fractions. In marsh areas, soil C extracted with NaOH had four to six times higher amounts of humic acid, fulvic acid and humin than soil C extracted by cold and hot water, HCl/HF, and Na pyruvate. In the pond area, humic acid, fulvic acid and humin content were two to four times lower than in the marsh area. More soil C and N was found in the marsh area than in the pond area. These wetlands proved to be large sinks for stable C forms.