Shreeram Inamdar

BMP IMPACTS ON SEDIMENT AND NUTRIENT YIELDS FROM AN AGRICULTURAL WATERSHED IN THE COASTAL PLAIN REGION

The goal of the Nomini Creek watershed monitoring study was to quantify the effectiveness of BMPs at the watershed scale and to determine if the improvements in water quality could be sustained over a long–term period. Information on the long–term effectiveness of BMPs is critical since BMPs are being implemented under the state cost–share program to reduce nonpoint source pollution (NPS) to the Chesapeake Bay. The Nomini Creek project started in 1985 and was completed in 1997. A pre– versus post–BMP design was used. A combination of managerial and structural BMPs was implemented. Major BMPs implemented in the Nomini Creek watershed included no–tillage, filter strips, and nutrient management. The data collected at the 1463 ha Nomini Creek watershed consisted of land use, hydrologic, water quality, soils, and geographical information. The BMPs implemented at Nomini Creek reduced average annual loads and flow–weighted concentrations of nitrogen (N) by 26% and 41%, respectively. Average annual total–N loads discharged from the watershed were reduced from 9.57 kg/ha during the pre–BMP period to 7.05 kg/ha for the post–BMP period. Largest reductions were observed for dissolved ammonium–N, soluble organic–N, and particulate–N. In contrast, nitrate–N loads increased after BMP implementation. Increase in nitrate exports was likely due to ammonification and nitrification, and subsequent leaching of particulate–N species that were conserved on the field. In comparison to N, reductions in phosphorus (P) loads and concentrations were not significant. BMP implementation resulted in a mere 4% reduction for total–P with a corresponding 24% reduction in flow–weighted concentration. The average annual total–P loads exported from the watershed were 1.31 and 1.26 kg/ha for the pre– and post–BMP periods, respectively. Reductions in total–P loads were due to decreases in particulate–P. Exports of ortho–P and dissolved organic–P increased after BMP implementation. It is likely that some of this post–BMP increase in dissolved P fractions was associated with dissolution and leaching of particulate–P, and higher rainfall–runoff activity in the watershed during the post–BMP period. In comparison to nutrients, there was no significant change in suspended solids discharged from the watershed. Overall, the findings of this study indicate that the BMPs were effective in reducing the losses of some forms of nutrients, such as ammonium–N and particulate–P, from the Nomini Creek watershed, but additional BMPs are necessary to achieve significant reductions in all forms of N and P.

Seasonal pattern of dissolved organic matter (DOM) in watershed sources: influence of hydrologic flow paths and autumn leaf fall

Seasonal patterns of dissolved organic matter (DOM) were evaluated for multiple watershed sources and stream water during baseflow and stormflow to investigate the influence of hydrologic flow paths and key phenological events. Watershed sources sampled were throughfall, litter leachate, soil water, and deep groundwater. DOM data for a 4-year period (2008–2011) included: DOC concentrations and spectrofluorometric indices such as a254, humification index, protein-like and humic-like DOM. Seasons were defined as—winter (December–February), spring (March–May), summer (June–September) and autumn (October and November). Seasonal differences in DOM were most pronounced for surficial flow paths (e.g., stormflow, litter leachate, throughfall and soil water) but muted or absent for groundwater and baseflow. This was attributed to the loss of DOM by sorption on mineral soil surfaces and/or microbial breakdown. DOM in summer stormflow had higher DOC concentrations and was more humic in character versus DOM in spring and winter runoff. Storm events in early autumn produced a sharp increase in DOC concentrations and % protein-like DOM for stream waters and litter leachate. Elevated DOC concentrations for early spring throughfall were attributed to leaching of organic exudates associated with leaf emergence. Our results underscore that watershed and ecosystem studies need to pay a greater attention to surficial flow paths and runoff sources (including stormflow) for understanding seasonal patterns of DOM. Understanding the influence of phenological episodes such as autumn leaf-fall for DOM is important considering that these transitional events may be especially affected by climate change.

ANIMALWASTE BMP IMPACTS ON SEDIMENT AND NUTRIENT LOSSES IN RUNOFF FROM THE OWL RUN WATERSHED

The results of the 10-year study conducted in the Owl Run watershed clearly indicate the beneficial impacts of the best management practices (BMPs) on the surface water quality. The main objective of the study was to determine the effectiveness of a system of animal waste BMPs for improving surface water quality. Precipitation, streamflow, total suspended solids, nitrogen (N), and phosphorus (P) water quality parameters were measured at the main outlet and in three subwatersheds. A pre- and post-BMP comparisons of annual water quality parameters were performed. Reductions in all forms of N and most forms of P were observed due to the implementation of BMPs. For the average annual values at the main watershed outlet, BMPs were effective in reducing both loads and concentrations of all forms of N with the largest reductions in soluble organic N (62%) and the smallest reduction for nitrate-N (35%). Furthermore, BMPs were effective in reducing both loads and concentrations of most forms of P with the largest reductions in particulate-P (78%) and the smallest reduction for soluble P (39%). However, BMPs were not effective in reducing orthophosphorus-P. The system of BMPs implemented in the Owl Run watershed was effective in reducing nutrient loadings, especially N loadings. However, when P is the main water quality concern, implementation of P-based nutrient management plans should be considered.

Simultaneous Analysis of Free and Conjugated Estrogens, Sulfonamides, and Tetracyclines in Runoff Water and Soils Using Solid-Phase Extraction and Liquid Chromatography—Tandem Mass Spectrometry

The ability to monitor multiple analytes from various classes of compounds in a single analysis can increase throughput and reduce cost when compared to traditional methods of analyses. This method for analyzing free (parent estrogen) and conjugated estrogens (metabolites) along with sulfonamides and tetracyclines utilizes a high pH (10.4) mobile phase with an ammonium hydroxide buffer for both positive- and negative-mode electrospray ionization. A single-step sample preparation by solid-phase extraction (SPE) was used to isolate and concentrate all analytes simultaneously. The analytical method was developed and validated for recoveries at 3 concentration levels for water and soil and produced recoveries of 42-123% and 21-105% respectively. Method detection limits ranged from 0.3 to 1.0 ng/L for water samples and 0.01 to 0.1 ng/g for soils. The method quantification limit ranged from 0.9 to 3.3 ng/L for water samples and 0.06 to 0.7 ng/g for soils. The single-point standard addition calibration procedure was validated across a linear range of MQL to 100 ng/L with ≥82% accuracy against a matrix matched standard curve. Furthermore, sorption of tetracyclines onto glassware was investigated and minimized by 10% using nitric acid-rinsed glassware, while separation parameters were further optimized based on retention time and signal responses. This method has been used for the quantification of estrogens, tetracyclines, and sulfonamides in soil and runoff waters with multiple compounds detected simultaneously in a single analysis.

Nitrogen biogeochemistry in the Adirondack Mountains of New York: hardwood ecosystems and associated surface waters

Studies on the nitrogen (N) biogeochemistry in Adirondack northern hardwood ecosystems were summarized. Specific focus was placed on results at the Huntington Forest (HFS), Pancake-Hall Creek (PHC), Woods Lake (WL), Ampersand (AMO), Catlin Lake (CLO) and Hennessy Mountain (HM). Nitrogen deposition generally decreased from west to east in the Adirondacks, and there have been no marked temporal changes in N deposition from 1978 through 1998. Second-growth western sites (WL, PHC) had higher soil solution NO(3-) concentrations and fluxes than the HFS site in the central Adirondacks. Of the two old-growth sites (AMO and CLO), AMO had substantially higher NO(3-) concentrations due to the relative dominance of sugar maple that produced litter with high N mineralization and nitrification rates. The importance of vegetation in affecting N losses was also shown for N-fixing alders in wetlands. The Adirondack Manipulation and Modeling Project (AMMP) included separate experimental N additions of (NH4)2SO4 at WL, PHC and HFS and HNO3 at WL and HFS. Patterns of N loss varied with site and form of N addition and most of the N input was retained. For 16 lake/watersheds no consistent changes in NO(3-) concentrations were found from 1982 to 1997. Simulations suggested that marked NO(3-) loss will only be manifested over extended periods. Studies at the Arbutus Watershed provided information on the role of biogeochemical and hydrological factors in affecting the spatial and temporal patterns of NO(3-) concentrations. The heterogeneous topography in the Adirondacks has generated diverse landscape features and patterns of connectivity that are especially important in regulating the temporal and spatial patterns of NO(3-) concentrations in surface waters.

RIPARIAN ECOSYSTEM MANAGEMENT MODEL (REMM): I. TESTING OF THE HYDROLOGIC COMPONENT FOR A COASTAL PLAIN RIPARIAN SYSTEM

The Riparian Ecosystem Management Model (REMM) was used to simulate shallow groundwater movement, water table depths, surface runoff, and annual hydrologic budgets for a Coastal Plain riparian buffer system near Tifton, Georgia, USA. The riparian buffer consisted of zone 3 (grass downslope from a row-crop field); zone 2 (mature pine forest downslope from zone 3); and zone 1 (mature hardwood forest downslope from zone 2, adjacent to stream). Measured surface runoff and shallow groundwater movement from the adjacent agricultural field were used as the hydrologic input to REMM. Uncalibrated simulation results for a five-year period were compared to measured values for the same time period. The overall error in zone 2 and zone 1 mean water table depths was about 0.07 m, although absolute errors were higher. The water table dynamics simulated by REMM were similar to observed although lags were observed in the response of the simulated water table to large rainfall events. Mixed results were obtained from observed versus simulated surface runoff comparisons, primarily due to large variability in observed runoff depths along the riparian transect. Simulated surface runoff depths for zone 3 were within one standard deviation for four out of the five years. For zone 2, surface runoff depths could only be simulated within one standard deviation for two out of the five years. Simulated seasonal total depths of surface runoff did not always agree with observed values but usually followed both similar temporal and spatial patterns. Annual hydrologic budgets produced total streamflow comparable to those estimated for the riparian buffer site. These results provide an adequate basis for subsequent testing of other REMM model components including water quality and nutrient cycling.

Comparison of Two PARAFAC Models of Dissolved Organic Matter Fluorescence for a Mid-Atlantic Forested Watershed in the USA

The composition of dissolved organic matter (DOM) in a mid-Atlantic forested watershed was evaluated using two fluorescence models—one based on previously validated model (Cory and McKnight, 2005) and the other developed specifically for our study site. DOM samples for the models were collected from multiple watershed sources over a two-year period. The previously validated parallel factor analysis (PARAFAC) model had 13 DOM components whereas our site-specific model yielded six distinct components including two terrestrial humic-like, two microbial-derived humic-like, and two protein-like components. The humic-like components were highest in surficial watershed sources and decreased from soil water to groundwater whereas the protein-like components were highest for groundwater sources. Discriminant analyses indicated that our site-specific model was more sensitive to subtle differences in DOM and the sum of the humic- and protein-like constituents yielded more pronounced differences among watershed sources as opposed to the prevalidated model. Dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) concentrations and selected DOM metrics were also more strongly correlated with the site-specific model components. These results suggest that while the pre-validated model may capture broader trends in DOM composition and allow comparisons with other study sites, a site-specific model will be more sensitive for characterizing within-site differences in DOM.

RIPARIAN ECOSYSTEM MANAGEMENT MODEL (REMM): II. TESTING OF THE WATER QUALITY AND NUTRIENT CYCLING COMPONENT FOR A COASTAL PLAIN RIPARIAN SYSTEM

The Riparian Ecosystem Management Model (REMM) was used to simulate nitrogen (N), phosphorus (P), and carbon (C) cycling and transport in a Coastal Plain riparian buffer system near Tifton, Georgia. The riparian buffer consisted of zone 3 (grass next to a row crop field); zone 2 (mature pine forest downslope from zone 3); and zone 1 (hardwood forest downslope from zone 2, adjacent to a stream). Uncalibrated simulation results for a five-year period were compared to measured values for the same time period at the research site. In general, simulated water table nutrient concentrations were within one standard deviation of observed values on an annual basis. Surface runoff loads exiting zone 3 for most N and P forms were simulated within one standard deviation of the observed. In contrast zone 2, surface runoff loads for inorganic N species were an order of magnitude lower than observed. Although some of the surface runoff differences (observed vs. simulated) were large in relative terms, the overall trends within the riparian buffer were generally well-represented and differences were not large in absolute terms. Simulated values for one of the most important processes responsible for effectiveness of riparian zones — denitrification, were within the range of those observed. Much of the temporal dynamics of the observed data were also captured in the REMM simulations. Certain constraints of the model use are discussed, but REMM appears to be useful for representing many of the specific processes and general trends in riparian ecosystem buffers.

Concentrations of Free and Conjugated Estrogens at Different Landscape Positions in an Agricultural Watershed Receiving Poultry Litter

Animal hormones can enter the aquatic environment along with runoff as a result of manure or litter application on agricultural landscapes. Our understanding of the transport of these hormones and their concentrations at various points along the watershed drainage is however limited. We investigated the transport of naturally produced poultry hormones in an agricultural watershed located on coastal plain soils of Delaware receiving land application of raw poultry manure. The objective of this study was to determine the concentrations of free and conjugated forms of estrogens in agricultural runoff at selected landscape positions in the agricultural watershed. Estrogen concentrations were determined for surface water, soil water, and runoff sediment. Estrogen forms that were analyzed were: Estrone (E1), Estradiol (E2β and E2α), Estriol (E3), and their sulfate and glucuronide conjugates. Poultry litter application occurred at a rate of 9 Mg ha−1 in early spring (April 2010). Sampling was performed for surface runoff, subsurface drainage, and sediment for nine storm events extending over 187 days before and after manure application (March–October 2010). Runoff was collected from the field edge, upland and lowland riparian positions and from the stream. Samples were analyzed by for liquid chromatography with tandem mass spectrometry (LC-MS/MS). Concentrations of estrogens were low (<20 ng l−1) for most of the samples and decreased from the field edge into the riparian zone. Estrogens were not detected in soil water and runoff sediments. Overall, this study suggests that manure application practices at our sites in Delaware such as incorporation of litter into the soil likely reduced the concentrations of estrogens in runoff and reduced the threat posed to aquatic ecosystems.

Particulate nitrogen exports in stream runoff exceed dissolved nitrogen forms during large tropical storms in a temperate, headwater, forested watershed

Although lasting only a fraction of the year, large storms may represent a significant, but highly variable, control on watershed nitrogen (N) fluxes. We determined the exports of particulate N (PN) and total dissolved N (TDN) including nitrate-N (NO3-N) and dissolved organic N (DON) in streamflow from a 12 ha temperate forested watershed. Sampling was performed for 15 storms over September 2010 to December 2012 and included four large tropical storms – Nicole (2010), Irene and Lee (2011) and Sandy (2012). PN composed a substantial portion (39-87%) of the storm event N export with storms constituting 65% of the 2011 PN export. Tropical storm Irene alone generated 1.76 kg N ha−1 of PN which was 27% of the annual watershed N (6.43 kg N ha−1) export for 2011. In contrast, tropical storm Sandy (October 2012), yielded low sediment and PN exports, likely due to low precipitation intensity and a freshly-fallen leaf cover that may have reduced soil erosion. Streamwater concentrations of PN, NO3-N, and DON ranged from 0–17.5, 0–2.02, and 0.01–0.54 mg N L−1, respectively. Nitrate-N concentrations displayed a dilution trajectory for peak stormflows suggesting supply limitation, a response that was not as strong for PN. These results underscore the importance of large storms for PN export which is significant given that climate-change predictions indicate an increasing intensity of large tropical storms for the northeast USA. Elevated PN exports could further exacerbate water quality and eutrophication problems in sensitive aquatic ecosystems already subjected to excess dissolved nitrogen loads.