Search

Excess export of reactive nitrogen in the form of nitrate (NO 3-) from suburban watersheds is a major source of water quality degradation and threatens the health of downstream and coastal waterbodies. Ecosystem restoration and best management practices (BMPs) can be introduced to reduce in-stream NO 3- loads by promoting vegetation uptake and denitrification in the upland and riparian areas. However, accurately evaluating the effectiveness of these practices and setting regulations for nitrogen inputs requires an understanding of how human sources of nitrogen interact with ecohydrological systems. We evaluated how the spatial and temporal distribution of nitrogen sources interacts with ecohydrological transport and transformation processes along surface and subsurface flow paths with respect to nitrogen cycling and export. Embedding distributed household sources of nitrogen and water within hillslope hydrologic systems influences the development of both planned and unplanned "hot spots" of nitrogen flux and retention in suburban ecosystems. We chose a well-monitored low-density suburban watershed, Baisman Run, in Baltimore County, Maryland, USA, to evaluate patterns of in-stream NO 3- concentrations and terrestrial nitrogen cycling processes in response to three common activities: irrigation, fertilization, and on-site sanitary wastewater disposal (septic systems). We augmented a distributed ecohydrological model, RHESSys (Regional Hydro-Ecological Simulator System), with estimates of the spatial distribution of these loads at household parcel level to develop a predictive understanding of the factors generating upland and riparian nitrogen cycling, transport, and stream NO 3- concentrations. We calibrate subsurface hydraulic parameters only without calibrating ecosystem and biogeochemical processes. The calibrated model predicted mean NO 3- concentrations of 1.43 mg NO 3- -N L−1 compared to the observed 1.6 mg NO 3- -N L−1 from water year 2013 to 2017. With spatially explicit irrigation, fertilizer, and septic effluent inputs, estimated denitrification rates in grass lawns, a dominant land cover in suburban landscapes, were also in the range of previously measured values. The highest predicted denitrification rates (N retention hot spots) were downslope of lawn and septic locations in a constructed wetland and at a riparian sediment accumulation zone at the base of a gully receiving street drainage. These locations illustrate the development of hot spots for nitrogen cycling and export in both planned and "accidental" retention features. Appropriate siting of suburban nutrient management and BMPs should assess and incorporate spontaneously developed nutrient hot spots to design improved landscape ecosystem N retention and water quality. [ABSTRACT FROM AUTHOR]

Stream, floodplain, and wetland restorations enhance water quality and ecological function; however, soil health is prioritized infrequently in restoration planning and monitoring. Buried, historic, hydric soils—common across U.S. mid‐Atlantic valley bottoms beneath legacy sediments—are not included in most floodplain restoration designs, though they may retain favorable biogeochemical characteristics and host legacy microbial communities that could support ecosystem recovery if exhumed and preserved. To assess the efficacy of including historic hydric soils in floodplain restoration for nitrogen (N) removal, we characterized pre‐Euro‐American settlement wetland soils buried below legacy sediments and now exposed along incised streambanks across the mid‐Atlantic. We compared carbon (C) and N contents; C:N ratios; nitrate‐N and ammonium‐N concentrations; denitrification rates; functional genes for denitrification (nosZ) and nitrification (amoA for ammonia oxidizing archaea [AoA] + ammonia oxidizing bacteria [AoB]); and phospholipid fatty acid biomasses of historic wetland soils with contemporary wetland soils before and after an 1‐year incubation in a recently restored floodplain. Compared to modern wetland soils, historic hydric soils buried by legacy sediment are less nutrient‐rich, have fewer functional genes for and lower rates of denitrification, and possess significantly less microbial biomass. Following the 1‐year incubation, many of these concentrations, rates, and gene counts increased in historic soils, though not substantially. Ultimately, our results suggest that while inclusion of historic, hydric soils and their legacy microbiomes is valuable for N‐removal in floodplain restoration, the recovery of historic, hydric soils is predictably slow, and attainment of restoration goals, such as increased denitrification, may require multiple years. [ABSTRACT FROM AUTHOR]

Excess export of reactive nitrogen in the form of nitrate (NO3-) export from exurban watersheds is a major source of water quality degradation and threatens the health of downstream and coastal waterbodies. Ecosystem restoration and best management practices (BMPs) can be introduced to reduce in-stream NO3- loads by promoting vegetation uptake and denitrification on uplands. However, accurately evaluating the effectiveness of these practices and setting regulations for nitrogen inputs requires an understanding of how human sources of nitrogen interact with ecohydrological systems. We evaluated how the spatial and temporal distribution of nitrogen sources, and the transport and transformation processes along hydrologic flowpaths control nitrogen cycling, export, and the development of "hot spots" of nitrogen flux in suburban ecosystems. We chose a well-monitored exurban watershed, Baisman Run in Baltimore County, Maryland, USA, to evaluate patterns of in-stream NO3- concentrations and upland nitrogen-related processes in response to three common activities: irrigation, fertilization, and on-site sanitary wastewater disposal (septic systems). We augmented a distributed ecohydrological model, RHESSys, with estimates of these additional loads to improve prediction and understanding of the factors generating both upland nitrogen cycling and stream NO3- concentrations. The augmented model predicted streamflow-weighted NO3- concentrations of 1.37 mg NO3--N/L, compared to observed 1.44 mg NO3--N/L, while the model predicted concentrations of 0.28 mg NO3--N/L without the additional loads from human activities from water year 2013 to 2017. Estimated denitrification rates in grass lawns, a dominant land cover in suburban landscapes, were in the range of measured values. The highest predicted denitrification rates were downslope of lawn and septic locations in a constructed wetland, and at a sediment accumulation zone at the base of a gully receiving street drainage. These locations illustrate the development of hot spots for nitrogen cycling and export in both planned and "accidental" retention features. Appropriate siting of best BMPs and the identification of spontaneously developed nutrient hot spots should be pursued to retain nutrients and improve water quality. [ABSTRACT FROM AUTHOR]

Based on a follow-up mail survey conducted in 2009, we found that structured, one-time workshops can influence and impact participant behavior change. Survey results suggest that brief workshops, staffed by key resource personnel, can have a powerful influence on participant behavior change and fill an important gap in rural drinking water protection. As a result of these educational workshops, we have learned that single-session workshops with supporting materials can encourage: (1) Testing of drinking water wells, (2) Contacting resource experts for more information and assistance, and (3) Sharing management information with other private well owners.

Soil C supplies vary spatially within and among riparian wetlands. Understanding this variability is essential to assessments of C-dependent riparian wetland functions such as water quality enhancement and C storage. In this study, we examined the distribution of C with depth across the riparian landscape. Our objectives were to describe the spatial distribution of various C forms in the subsurface of riparian wetlands, and to identify the watershed, landscape, and soil characteristics that govern the distribution of these forms. Twenty-two riparian sites, mapped as alluvial or outwash soils, were examined along first- through fourth-order streams. Soils were described from pits and auger borings along transects established perpendicular to the stream. Roots and buried A horizons represent the majority of C in the subsurface, representing an important source of C for riparian zone functions. Buried A horizons and C-rich lenses, indicative of alluvial soils, were identified in 21 of the 22 sites. Higher order riparian zones tended to have greater quantities of alluvium. Roots were generally distributed to the greatest depths close to the streams where alluvial deposits were thickest. All first-, second-, and third-order riparian zones were mapped as outwash soils on county-scale soil surveys. These sites, however, contained predominantly alluvial soils, suggesting that soil surveys at the 1:15,840 scale are inadequate for identifying alluvial soils along lower order streams. To assess the best predictors of alluvium distribution within riparian zones, 11 watershed characteristics were examined. A forward stepwise regression revealed that watershed size and floodplain width are two of the most important indicators of the quantity, width, and depth of alluvium, and subsequently subsurface C, within glaciated riparian zones. Abbreviations: FOM, fragmental organic matter.