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1. Seasonal N dynamics and fluxes of nitrogen in leachate and runoff from experimental rainfalls on fertilized and unfertilized lawns in Baltimore County, Maryland

   https://doi.org/10.6073/pasta/bccb237418362143cdbad53d871ae5eb  

   Suchy, Amanda K; Groffman, Peter M (January 2022, Environmental Data Initiative)

   The aim of this research was to examine the spatial and temporal variation in export control points of nitrogen on residential lawns (locations prone to mobilizing nitrogen during a rain event) and to examine if previously measured hydrobiogeochemical properties were predictive of N mobilization in lawns. This data set contains measurements of saturated infiltration rates, sorptivity, soil moisture, soil organic matter, bulk density, pH, soil nitrate, soil ammonium, N2O, N2 and CO2 fluxes from soil cores, nitrogen mineralization rates and fluxes of N in runoff and leachate from fertilized and unfertilized residential and institutional lawns. Study lawns were located at homes of people who agreed to volunteer their lawn for the study from a door knocking campaign. Four sampling houses were located in an exurban neighborhood in Baisman Run. Five sampling houses were located in a suburban neighborhood in Dead Run. Two sampling locations on institutional lawns were located at University of Maryland Baltimore County. At the exurban study houses and institutional lawns sites, we identified one hillslope to conduct sampling on. At the Dead Run houses we identified one hillslope on the front yard and one in the backyard as there were distinct locations that were not present in the exurban neighborhood. Locations within the yards for sampling were selected based on sampling conducted in October 2017. Locations were grouped into four categories based on have either high or low potential denitrification rates and high or low saturated infiltration rates (n=48). These locations were also distributed across yard types (exurban, suburban or institutional), fertilizer treatments, and hillslope location (top or bottom of hillslope). At each sampling location we ran a Cornell Sprinkle Infiltrometer to generate an experimental rainfall during which we collected runoff and leachate to quantity N flux. We also measure sorptivity and saturated infiltration rates. Volumetric water content was measured before and after infiltrometer runs with a Field Scout TDR 300 with 7.5 cm rods. In addition, at each sampling location we took two soil cores to 10 cm depth to measure gaseous N flux and soil N processes. Soil cores were stored on ice in the field, and then stored at 4°C in the lab until processed for variables mentioned above. Sampling was conducted across four seasons (April 2018, September 2018, November 2018 and March 2019) to capture seasonal variability including the timing of fertilizer applications. 

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2. Nitrogen cycling, soil properties and infiltration rates along a topographic gradient in lawns in Baltimore County, Maryland

   https://doi.org/10.6073/pasta/67615100eabd2f3d43718759f85c131e  

   Suchy, Amanda K; Groffman, Peter M (January 2020, Environmental Data Initiative)

   The aim of this research was to examine how topography and homeowner fertilizer practices affected soil and hydrologic properties of residential lawns to determine if there are locations within lawns that have the potential to act as hotspots of nitrogen transport during rain events. This data set contains measurements of saturated infiltration rates, sorptivity, soil moisture, soil organic matter, pH, soil nitrate, soil ammonium, denitrification potentials and limiting factors, and nitrogen mineralization rates from fertilized and unfertilized residential and institutional lawns. Study lawns were located at homes of people who agreed to volunteer their lawn for the study from a door knocking campaign. Four sampling houses were located in an exurban neighborhood in Baisman Run. Five sampling houses were located in a suburban neighborhood in Dead Run. Two sampling locations on institutional lawns were located at University of Maryland Baltimore County. At the exurban study houses and institutional lawns sites,we identified one hillslope to conduct sampling on. At the Dead Run houses we identified one hillslope on the front yard and one in the backyard as there were distinct locations that were not present in the exurban neighborhood. In total we sampled on 16 hillslopes. At each hillslope, we identified the top, toe and swale locations. At each hillslope location, we selected three sampling locations along a transect (maximum 10 meters in length; total of 144 sampling locations). At each sampling location we ran a Cornell Sprinkle Infiltrometer to measure sorptivity and saturated infiltration rates. Volumetric water content was measured before and after infiltrometer runs with a Field Scout TDR 300 with 7.5 cm rods. In addition, at each sampling location we took two soil cores to 10 cm depth, and combined and homogenized the two cores for that sampling location for a total of 144 soil samples. Soil cores were stored on ice in the field, and then stored at 4°C in the lab until processed for variables mentioned above. Sampling for soil cores was conducted in September 2017 with one house collected on 11/1/2017 due to changes in homeowner volunteers. Cornell Sprinkle Infiltrometer measurements were taken in October 2017 with one exception for house DR3. The front yard was conducted on 1/30/2018 and the back yard was completed on 2/27/2018 due to scheduling conflicts and weather interference during October and proceeding months. 

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3. Investigating potential hydrological ecosystem services in urban gardens through soil amendment experiments and hydrologic models

   https://doi.org/10.1007/s11252-021-01191-7  

   Chapman, Eric J.; Small, Gaston E.; Shrestha, Paliza (January 2022, Urban Ecosystems)

   Abstract Among the ecosystem services provided by urban greenspace are the retention and infiltration of stormwater, which decreases urban flooding, and enhanced evapotranspiration, which helps mitigate urban heat island effects. Some types of urban greenspace, such as rain gardens and green roofs, are intentionally designed to enhance these hydrologic functions. Urban gardens, while primarily designed for food production and aesthetic benefits, may have similar hydrologic function, due to high levels of soil organic matter that promote infiltration and water holding capacity. We quantified leachate and soil moisture from experimental urban garden plots receiving various soil amendments (high and low levels of manure and municipal compost, synthetic fertilizer, and no inputs) over three years. Soil moisture varied across treatments, with highest mean levels observed in plots receiving manure compost, and lowest in plots receiving synthetic fertilizer. Soil amendment treatments explained little of the variation in weekly leachate volume, but among treatments, high municipal compost and synthetic fertilizer had lowest leachate volumes, and high and low manure compost had slightly higher mean leachate volumes. We used these data to parameterize a simple mass balance hydrologic model, focusing on high input municipal compost and no compost garden plots, as well as reference turfgrass plots. We ran the model for three growing seasons under ambient precipitation and three elevated precipitation scenarios. Garden plots received 12–16% greater total water inputs compared to turfgrass plots because of irrigation, but leachate totals were 20–30% lower for garden plots across climate scenarios, due to elevated evapotranspiration, which was 50–60% higher in garden plots. Within each climate scenario, difference between garden plots which received high levels of municipal compost and garden plots which received no additional compost were small relative to differences between garden plots and turfgrass. Taken together, these results indicate that garden soil amendments can influence water retention, and the high-water retention, infiltration, and evapotranspiration potential of garden soils relative to turfgrass indicates that hydrologic ecosystem services may be an underappreciated benefit of urban gardens. 

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4. Disentangling the responses of dissolved organic carbon and nitrogen concentrations to overlapping drivers in a northeastern United States forested watershed

   https://doi.org/10.3389/frwa.2023.1065300  

   Ruckhaus, Manya; Seybold, Erin C.; Underwood, Kristen L.; Stewart, Bryn; Kincaid, Dustin W.; Shanley, James B.; Li, Li; Perdrial, Julia N. (March 2023, Frontiers in Water)

   The concurrent reduction in acid deposition and increase in precipitation impact stream solute dynamics in complex ways that make predictions of future water quality difficult. To understand how changes in acid deposition and precipitation have influenced dissolved organic carbon (DOC) and nitrogen (N) loading to streams, we investigated trends from 1991 to 2018 in stream concentrations (DOC, ~3,800 measurements), dissolved organic nitrogen (DON, ~1,160 measurements), and dissolved inorganic N (DIN, ~2,130 measurements) in a forested watershed in Vermont, USA. Our analysis included concentration-discharge (C-Q) relationships and Seasonal Mann-Kendall tests on long-term, flow-adjusted concentrations. To understand whether hydrologic flushing and changes in acid deposition influenced long-term patterns by liberating DOC and dissolved N from watershed soils, we measured their concentrations in the leachate of 108 topsoil cores of 5 cm diameter that we flushed with solutions simulating high and low acid deposition during four different seasons. Our results indicate that DOC and DON often co-varied in both the long-term stream dataset and the soil core experiment. Additionally, leachate from winter soil cores produced especially high concentrations of all three solutes. This seasonal signal was consistent with C-Q relation showing that organic materials (e.g., DOC and DON), which accumulate during winter, are flushed into streams during spring snowmelt. Acid deposition had opposite effects on DOC and DON compared to DIN in the soil core experiment. Low acid deposition solutions, which mimic present day precipitation, produced the highest DOC and DON leachate concentrations. Conversely, high acid deposition solutions generally produced the highest DIN leachate concentrations. These results are consistent with the increasing trend in stream DOC concentrations and generally decreasing trend in stream DIN we observed in the long-term data. These results suggest that the impact of acid deposition on the liberation of soil carbon (C) and N differed for DOC and DON vs. DIN, and these impacts were reflected in long-term stream chemistry patterns. As watersheds continue to recover from acid deposition, stream C:N ratios will likely continue to increase, with important consequences for stream metabolism and biogeochemical processes. 

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5. Baltimore Ecosystem Study: Stream chemistry for Gwynns Falls Upper Tributaries

   https://doi.org/10.6073/pasta/5f15b7aa8d3f57d9e05a0392c6f57749  

   Groffman, Peter M; Rosi, Emma; Martel, Lisa D (January 2020, Environmental Data Initiative)

   In the Baltimore urban long-term ecological research (LTER) project, (Baltimore Ecosystem Study, BES) we use the watershed approach to evaluate integrated ecosystem function. The LTER research is centered on the Gwynns Falls watershed, a 17,150 ha catchment that traverses a gradient from the urban core of Baltimore, through older urban residential (1900 - 1950) and suburban (1950- 1980) zones, rapidly suburbanizing areas and a rural/suburban fringe. Our long-term sampling network includes four longitudinal sampling sites along the Gwynns Falls as well as several small (40 - 100 ha) watersheds located within or near to the Gwynns Falls. The longitudinal sites provide data on water and nutrient fluxes in the different land use zones of the watershed (rural/suburban, rapidly suburbanizing, old suburban, urban core) and the small watersheds provide more focused data on specific land use areas (forest, agriculture, rural/suburban, urban). Each of the gaging sites is continuously monitored for discharge and is sampled weekly for chemistry. Additional chemical sampling is carried out in a supplemental set of sites to provide a greater range of land use. Weekly analyses includes nitrate, phosphate, total nitrogen, total phosphorus, chloride and sulfate, total suspended solids, turbidity, fecal coliforms, temperature, dissolved oxygen and pH. Cations, dissolved organic carbon and nitrogen and metals are measured on selected samples. This dataset presents stream chemistry from the Upper Gwynns Falls tributaries. From April 1999 to August 2000 Johns Hopkins University graduate student Mark Colosimo sampled a group of sites in the Upper Gwynns Falls (Red Run, Horsehead Branch, Scotts Level Branch, Holly Branch). There were two sites in the Red Run drainage. This watershed drains approximately 19 km2 and has been rapidly suburbanizing since the early 1990s. Percent impervious surface was approximately 10% as of 2002. Sampling station Red Run 1 (RR1) was approximately 35 m upstream of the crossing of Painters Mill Bridge Road, and 350 m upstream of the confluence with the Gwynns Falls. Sampling station Red Run 2 (RR2) was farther upstream, between the Pleasant Hill and Dolfield road crossings. There were two sites along Scotts Level Branch, an older suburban watershed which was approximately 25% impervious surface in 1970. Site SL1 drains approximately 11 km2 and is located at the outlet of the sub-watershed, just above the confluence with Gwynns Falls. Site SL2 is at the McDonogh Rd. bridge crossing. The Horsehead Branch (HH) sampling site was located at the McDonogh Road crossing. It drains approximately 5 km2 that has undergone rapid urbanization since the mid 1980s. As of 1997 percent impervious surface was approximately 12%. The Holly Bank (HB) sampling site was located just upstream of Gwynnbrook Ave. Seventy percent of land in this drainage is classified residential. The Gwynns Falls at McDonogh (GF5) site was located at the McDonogh school / McDonogh road crossing of the Gwynns Falls and samples a drainage area of approximately 51 km2, with approximately 20% impervious surface. 

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