scholarly journals Seasonality of nitrogen sources, cycling, and loading in a New England river discerned from nitrate isotope ratios

2021 ◽  
Vol 18 (11) ◽  
pp. 3421-3444
Author(s):  
Veronica R. Rollinson ◽  
Julie Granger ◽  
Sydney C. Clark ◽  
Mackenzie L. Blanusa ◽  
Claudia P. Koerting ◽  
...  
Keyword(s):  
New England ◽  
Warm Season ◽  
Nitrogen Sources ◽  
Isotope Ratios ◽  
Current Theory ◽  
Surface Flow ◽  
Forested Catchments ◽  
Nutrient Spiraling ◽  
Biological Cycling ◽  
N Loading

Abstract. Coastal waters globally are increasingly impacted due to the anthropogenic loading of nitrogen (N) from the watershed. To assess dominant sources contributing to the eutrophication of the Little Narragansett Bay estuary in New England, we carried out an annual study of N loading from the Pawcatuck River. We conducted weekly monitoring of nutrients and nitrate (NO3-) isotope ratios (15N / 14N, 18O / 16O, and 17O / 16O) at the mouth of the river and from the larger of two wastewater treatment facilities (WWTFs) along the estuary, as well as seasonal along-river surveys. Our observations reveal a direct relationship between N loading and the magnitude of river discharge and a consequent seasonality to N loading into the estuary – rendering loading from the WWTFs and from an industrial site more important at lower river flows during warmer months, comprising ∼ 23 % and ∼ 18 % of N loading, respectively. Riverine nutrients derived predominantly from deeper groundwater and the industrial point source upriver in summer and from shallower groundwater and surface flow during colder months – wherein NO3- associated with deeper groundwater had higher 15N / 14N ratios than shallower groundwater. Corresponding NO3- 18O / 16O ratios were lower during the warm season, due to increased biological cycling in-river. Uncycled atmospheric NO3-, detected from its unique mass-independent NO3- 17O / 16O vs. 18O / 16O fractionation, accounted for < 3 % of riverine NO3-, even at elevated discharge. Along-river, NO3- 15N / 14N ratios showed a correspondence to regional land use, increasing from agricultural and forested catchments to the more urbanized watershed downriver. The evolution of 18O / 16O isotope ratios along-river conformed to the notion of nutrient spiraling, reflecting the input of NO3- from the catchment and from in-river nitrification and its coincident removal by biological consumption. These findings stress the importance of considering seasonality of riverine N sources and loading to mitigate eutrophication in receiving estuaries. Our study further advances a conceptual framework that reconciles with the current theory of riverine nutrient cycling, from which to robustly interpret NO3- isotope ratios to constrain cycling and source partitioning in river systems.

scholarly journals Sources and cycling of nitrogen in a New England river discerned from nitrate isotope ratios

2020 ◽  
Author(s):  
Veronica R. Rollinson ◽  
Julie Granger ◽  
Sydney C. Clark ◽  
Mackenzie L. Blanusa ◽  
Claudia P. Koerting ◽  
...  
Keyword(s):  
New England ◽  
River Discharge ◽  
Waste Water Treatment ◽  
Isotope Ratios ◽  
Surface Flow ◽  
River Flows ◽  
Total N ◽  
Nutrient Spiraling ◽  
Biological Cycling ◽  
N Loading

Abstract. Coastal waters globally are increasingly impacted due to the anthropogenic loading of nitrogen (N) from the watershed. In order to assess dominant sources of N contributing to the eutrophication of the Little Narragansett Bay estuary in New England, we carried out an annual study of N loading from the Pawcatuck River. We conducted weekly monitoring of nutrients and nitrate (NO3−) isotope ratios (15N / 14N, 18O / 16O and 17O / 16O) at the mouth of the river and from the larger of two Waste Water Treatment Facilities (WWTFs) along the estuary, as well as seasonal along-river surveys. Our observations reveal a direct relationship between N loading and the magnitude of river discharge, and a consequent seasonality to N loading into the estuary – rendering loading from the WWTFs and from an industrial site upriver more important at lower river flows during warmer months, comprising ~23 % and ~18 % of N loading, respectively. Riverine nutrients derived predominantly from deeper groundwater and the industrial point source upriver during low base flow in summer, and from shallower groundwater and surface flow at higher river flows during colder months. Loading of dissolved organic nitrogen appeared to increase with river discharge, ostensibly delivered by surface water. The NO3− associated with deeper groundwater had higher 15N / 14N ratios than shallower groundwater, consistent with the expectation fractionation due to partial denitrification. Along-river, NO3− 15N / 14N ratios showed a correspondence to regional land use, increasing from agricultural and forested catchments to the more urbanized watershed downriver, with the agricultural and urbanized portions of the watershed contributing disproportionately to total N loading. Corresponding NO3− 18O / 16O ratios were lower during the warm season, a dynamic that we ascribe to increased biological cycling in-river. The 18O / 16O isotope ratios along-river were consistent with the notion of nutrient spiraling, reflecting NO3− input from the watershed and in-river nitrification and its coincident removal by biological consumption. Uncycled atmospheric NO3−, detected from its unique mass-independent NO3− 17O / 16O vs. 18O / 16O fractionation, accounted for

RESPONSE OF THREE WARM-SEASON GRASSES TO VARYING FERTILITY LEVELS ON FIVE SOILS

1982 ◽  
Vol 62 (3) ◽  
pp. 657-665 ◽  
Author(s):  
R. W. TAYLOR ◽  
D. W. ALLINSON
Keyword(s):  
New England ◽  
Panicum Virgatum ◽  
Warm Season ◽  
Late Summer ◽  
Control Treatment ◽  
Yield Response ◽  
Limiting Factor ◽  
Big Bluestem ◽  
P Fertilization ◽  
Warm Season Grasses

Animal production in New England has been limited by inadequate forage during mid- to late summer when cool-season grasses are in summer dormancy. Big bluestem (Andropogon gerardi Vitman), indiangrass [Sorghastrum nutans (L.) Nash] and switchgrass (Panicum virgatum L.) are warm-season grasses that may be a perennial source of summer forage. Since production of these warm-season grasses would be limited to the less fertile soils of the region, a greenhouse study was conducted to examine the growth and quality of these species in five acid, infertile soils as well as fertilizer-amended soils. The soils were fertilized with limestone (L), limestone plus nitrogen (LN), limestone, nitrogen plus phosphorus (LNP), and limestone, nitrogen, phosphorus plus potassium (LNPK). Limestone was applied to adjust soils to a pH of 6.5. Fertilizer was applied at rates of 45, 117 and 111 kg/ha of N, P and K, respectively. First harvest yields were greatest for switchgrass and big bluestem, but indiangrass produced significantly greater yields than either of the other grasses in the second harvest. In both harvests, the yields of all grasses were greatest under the LNP and LNPK fertility regimes. Nitrogen, without P, did not significantly increase yields above the control treatment in the first harvest. Yield responses to P fertilization varied with soils. Although P appeared to be the limiting factor insofar as growth was concerned, the yield response from P fertilization would probably be limited without N fertilization. Indiangrass was significantly higher in crude protein and K concentration and significantly lower in Ca concentration than big bluestem and switchgrass. Phosphorus concentrations were below the recommended levels for ruminant nutrition.

scholarly journals Velocity Fluctuations of the Bersækerbræ, East Greenland

1965 ◽  
Vol 5 (41) ◽  
pp. 739-747 ◽  
Author(s):  
T. W. Friese-Greene ◽  
G. J. Pert
Keyword(s):  
Current Theory ◽  
Surface Flow ◽  
Velocity Fluctuations ◽  
East Greenland

AbstractThe results of measurements of surface flow and ablation on the glacier Bersækerbræ, in the Staunings Alper, East Greenland, are presented. A correlation is shown between the rate of flow and rate of ablation, as suggested by current theory.

scholarly journals Velocity Fluctuations of the Bersækerbræ, East Greenland

1965 ◽  
Vol 5 (41) ◽  
pp. 739-747 ◽  
Author(s):  
T. W. Friese-Greene ◽  
G. J. Pert
Keyword(s):  
Current Theory ◽  
Surface Flow ◽  
Velocity Fluctuations ◽  
East Greenland

AbstractThe results of measurements of surface flow and ablation on the glacier Bersækerbræ, in the Staunings Alper, East Greenland, are presented. A correlation is shown between the rate of flow and rate of ablation, as suggested by current theory.

Observed Variability of Ocean Wave Stokes Drift, and the Eulerian Response to Passing Groups

2006 ◽  
Vol 36 (7) ◽  
pp. 1381-1402 ◽  
Author(s):  
Jerome A. Smith
Keyword(s):  
Surface Waves ◽  
Current Theory ◽  
Surface Flow ◽  
Stokes Drift ◽  
Wave Group ◽  
Lagrangian Surface ◽  
Wave Groups ◽  
Wide Range ◽  
Momentum Fluxes ◽  
Waves And Currents

Abstract Waves and currents interact via exchanges of mass and momentum. The mass and momentum fluxes associated with surface waves are closely linked to their Stokes drift. Both the variability of the Stokes drift and the corresponding response of the underlying flow are important in a wide range of contexts. Three methods are developed and implemented to evaluate Stokes drift from a recently gathered oceanic dataset, involving surface velocities measured continually over an area 1.5 km in radius by 45°. The estimated Stokes drift varies significantly, in line with the occurrence of compact wave groups, resulting in highly intermittent maxima. One method also provides currents at a fixed level (Eulerian velocities). It is found that Eulerian counterflows occur that completely cancel the Stokes drift variations at the surface. Thus, the estimated Lagrangian surface flow has no discernable mean response to wave group passage. This response is larger than anticipated and is hard to reconcile with current theory.

scholarly journals Speciated mercury at marine, coastal, and inland sites in New England – Part 1: Temporal variability

2012 ◽  
Vol 12 (11) ◽  
pp. 5099-5112 ◽  
Author(s):  
H. Mao ◽  
R. Talbot
Keyword(s):  
New England ◽  
Marine Boundary Layer ◽  
Limit Of Detection ◽  
Inversion Layer ◽  
Warm Season ◽  
Elemental Mercury ◽  
Positive Trend ◽  
Gaseous Elemental Mercury ◽  
Mixing Ratios ◽  
Nocturnal Inversion

Abstract. A comprehensive analysis was conducted using long-term continuous measurements of gaseous elemental mercury (Hg0), reactive gaseous mercury (RGM), and particulate phase mercury (HgP) at coastal (Thompson Farm, denoted as TF), marine (Appledore Island, denoted as AI), and elevated inland (Pac Monadnock, denoted as PM) sites from the AIRMAP Observatories in southern New Hampshire, USA. Decreasing trends in background Hg0 were identified in the 7.5- and 5.5-yr records at TF and PM with decline rates of 3.3 parts per quadrillion by volume (ppqv) yr−1 and 6.3 ppqv yr−1, respectively. Common characteristics at these sites were the reproducible annual cycle of Hg0 with its maximum in winter-spring and minimum in fall, comprised of a positive trend in the warm season (spring – early fall) and a negative one in the cool season (late fall – winter). Year-to-year variability was observed in the warm season decline in Hg0 at TF varying from a minimum total (complete) seasonal loss of 43 ppqv in 2009 to a maximum of 92 ppqv in 2005, whereas variability remained small at AI and PM. The coastal site TF differed from the other two sites with its exceptionally low levels (as low as below 50 ppqv) in the nocturnal inversion layer possibly due to dissolution in dew water. Measurements of Hg0 at PM exhibited the smallest diurnal to annual variability among the three environments, where peak levels rarely exceeded 250 ppqv and the minimum was typically 100 ppqv. It should be noted that summertime diurnal patterns at TF and AI were opposite in phase indicating strong sink(s) for Hg0 during the day in the marine boundary layer, which was consistent with the hypothesis of Hg0 oxidation by halogen radicals there. Mixing ratios of RGM in the coastal and marine boundary layers reached annual maxima in spring and minima in fall, whereas at PM levels were generally below the limit of detection (LOD) except in spring. RGM levels at AI were higher than at TF and PM indicating a stronger source strength in the marine environment. Mixing ratios of HgP at AI and TF were close in magnitude to RGM levels and were mostly below 1 ppqv. Diurnal variation in HgP was barely discernible at TF and AI in spring and summer. Higher levels of HgP were observed during the day, while values that were smaller, but above the LOD, occurred at night.

scholarly journals A 70-yr record of oxygen-18 variability in an ice core from the Tanggula Mountains, central Tibetan Plateau

2010 ◽  
Vol 6 (2) ◽  
pp. 219-227 ◽  
Author(s):  
D. R. Joswiak ◽  
T. Yao ◽  
G. Wu ◽  
B. Xu ◽  
W. Zheng
Keyword(s):  
Tibetan Plateau ◽  
Monsoon Rainfall ◽  
Ice Core ◽  
Warm Season ◽  
Ice Cores ◽  
Isotope Ratios ◽  
Rainfall Amount ◽  
North India ◽  
Annual Average ◽  
Central Tibetan Plateau

Abstract. A 33 m ice core was retrieved from the Tanggula Mts, central Tibetan Plateau at 5743 m a.s.l. in August 2005. Annual average δ18O values were determined for the upper 17 m depth (14.6 m w.eq.), representing the time series since the mid-1930s. Data are compared to previous results of an ice core from Mt. Geladaindong, 100 km to the northwest, for the period 1935–2003. During the time 1935–1960, δ18O values differed by 2–3‰ between the two ice cores, with generally lower ratios preserved in the Tanggula 2005 core. Differences in interannual variability and overall average ratios between the two study locations highlight the spatially variable climate controls on ice core isotope ratios within the boundary of monsoon- and westerly-impacted regions of the central Tibetan Plateau. Average annual net accumulation was 261 mm w.eq. for the period 1935–2004. The overall average δ18O value was −13.2‰ and exhibited a statistically significant increase from the 1935–1969 average (−13.7‰) to the 1970–2004 average (−12.6‰). Despite the observed increase in isotope ratios, isotopic temperature dependence was not evident, based on comparison with long-term data from meteorological stations to the north and southwest of the study location. Lack of correlation between average δ18O values and temperature is likely due to monsoon influence, which results in relatively greater isotopic depletion of moisture during the warm season. Evidence of monsoon impacts on precipitation in the central Tibetan Plateau has been previously documented, and statistically significant negative correlation (r=−0.37, p<0.01) between the annual average ice core δ18O values and North India monsoon rainfall was observed for the period 1935–2004. Although the δ18O data agree well with the monsoon rainfall amount, no significant correlation was observed between the core accumulation and the monsoon rainfall amount. Previous model and observational results suggest monsoon impact on δ18O in precipitation may extend beyond the immediate extent of heavy monsoon rainfall, reaching the central Tibetan Plateau. These results provide evidence that the δ18O variability at this study location may be sensitive to southern monsoon intensity.

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