Long-Term Trends in Nitrogen Removal by an Aridland Constructed Treatment Wetland

A Decade of Ecosystem-Scale Research at an Aridland Constructed Treatment Wetland

“…To our knowledge, this is the first time that control of surface hydrology by wetland plants has ever been reported. Our whole system water budget includes this input of new water to the vegetated marsh, and our nutrient budget accounts for new nutrients and pollutants being delivered to the marsh via the biological tide (Treese et al, 2020).…”

“…Our research follows a dualgradient experimental design: The first gradient is the entire 42 ha system from inflow to outflow (blue arrows in Figure 1) and the second gradient is specific to the 21 ha vegetated marsh, with 10 evenly distributed transects (white lines in Figure 1). Every other month we collect triplicate surface-water grab samples at the inflow and outflow and at the open water interface and shore ends of three of the marsh transects (numbers shown in Figure 1; Sanchez et al, 2016;Treese et al, 2020). We analyze these samples for inorganic N content (nitrite = NO 2 − , nitrate = NO 3 − , and ammonium = NH 4 + ).…”

“…This new water volume is also multiplied by the open water and shore sample N concentration difference. The simple sum of the two is the total N being removed by the marsh either daily or monthly daily (see Treese et al, 2020 for methodological details).…”

“…As I noted earlier, our water quality analysis and nutrient budget calculations focus on dissolved inorganic nitrogen (N). Treese et al (2020) combined our water quality data with inflow and outflow data to calculate N fluxes and N uptake, or removal, rates for the entire 42 ha CTW system (Figure 4). We also calculated N fluxes for only the vegetated marsh system, and partitioned them into N uptake or removal associated with the Biological Tide vs. removal without it (Figure 5; Treese et al, 2020).…”

“…Treese et al (2020) combined our water quality data with inflow and outflow data to calculate N fluxes and N uptake, or removal, rates for the entire 42 ha CTW system (Figure 4). We also calculated N fluxes for only the vegetated marsh system, and partitioned them into N uptake or removal associated with the Biological Tide vs. removal without it (Figure 5; Treese et al, 2020). The Biological Tide clearly enhanced the efficacy of the vegetated marsh to take up and process N, particularly during the hot summer months.…”