Effects of headwater wetlands on dissolved nitrogen and dissolved organic carbon concentrations in a suburban New Hampshire watershed

Abstract

Coupled processing of N and C in headwater wetlands can strongly affect downstream water quality. To understand how wetlands affect dissolved N and C concentrations in surface waters and the factors that influence changes in concentration, we measured landscape and physicochemical variables and dissolved N and C concentrations at the in-and outflows of 10 headwater wetlands in a suburban watershed (New Hampshire, USA) over 18 mo. We analyzed changes (Δ) in dissolved N and C concentrations (outflow -inflow) with linear mixed-effects models. A pulse in N 2 O concentrations that exceeded mean values by 2 to 3 orders of magnitude was observed during a summer characterized by rapidly fluctuating water-table elevations. NO 3 − concentrations were significantly lower, and DOC and DON concentrations were significantly higher at outflows than inflows. ΔNO 3 − was predicted by inflow concentrations of NO 3 − , NH 4 + , and DON, ΔDON, and season. ΔDON was predicted by inflow DON and DOC concentrations, ΔDOC, and dissolved O 2 (as the mean of in-and outflow concentrations). ΔTDN (total dissolved nitrogen) was predicted by inflow TDN and DOC concentrations, dissolved O 2 , and season. ΔDOC was predicted by DON inflow concentration and ΔDON, season, and the ratio of study-wetland to subwatershed area. No significant predictors of ΔN 2 O or ΔNH 4 + concentrations were found. In this suburban watershed, the passage of surface water through headwater wetlands is associated with decreased NO 3 − concentrations, increased DON and DOC concentrations, and seasonal shifts in TDN fractionation. Linear mixed-effects modeling was an effective approach to understanding coupled N and C dynamics in the study wetlands.

Helocrenic springs as sources of nutrient rich fine particulate organic matter in small foothill watershed

“…This principle is also supported by the marked decreases in dissolved forms of nitrogen and phosphorus reported in our study. Similar results from large New Hampshire headwater wetlands have been published by Flint and McDowell [63]. General view of the connection of spring wetlands and downstream waters provides a comprehensive review study by Alexander et al [64], describing retention and transformation of nutrients as one of the crucial functions of nonfloodplain wetlands.…”

Dissolved Organic Carbon and Nitrate Concentration‐Discharge Behavior Across Scales: Land Use, Excursions, and Misclassification

“…The c‐Q slopes of NO 3 − and TDN were positively correlated with forested land and negatively correlated with agricultural land, indicating a switch from transport limited to source limited behavior for dissolved inorganic nitrogen with the conversion of forest to agriculture. The annual c‐Q slopes of fDOM and DON were negatively correlated with percentage of wetland pointing to the distinct regulatory role of wetlands as the primary source of organic matter in these systems (Creed et al, 2003; Flint & McDowell, 2015; Zarnetske et al, 2018). These results indicate that catchment land use can explain a portion of the observed variation in annual c‐Q behavior among these 10 catchments and that the inorganic and organic components of the stream solute load have different drivers of their c‐Q relationships.…”

Assessment of Spatial Agglomeration of Agricultural Drought Disaster in China from 1978 to 2016

“…The Moran’s I statistic could be said to be the most widely used method of test area spatial autocorrelation 31 . According to the previous studies, the Moran’s I was widely used in phase separating mixtures 32 , analysis on urban traffic status 33 ,and pollution hotspot analysis, et al .…”