Increase In Total Nitrogen Concentration Research Articles

Hydrologic and water quality performance of regenerative stormwater conveyance installed to stabilize an eroded outfall

Conveying concentrated urban runoff to outfall locations frequently leads to stream bank erosion, channel incision, and the formation of headcuts. Installed in an incised eroded channel, regenerative stormwater conveyance (RSC) is a grade-control and treatment system that uses a series of pools and cascades with an underlying sand bed. As a recently developed practice, RSC performance evaluations are needed to improve the design and guide regulatory accreditation. An eroded channel with a 10% longitudinal slope was stabilized with a five-cell system and monitored for a 14-month period. A small capture volume (6-mm design event) and groundwater intrusion resulted in minimal hydrologic benefit. Hydrologic mitigation was attained only for storms less than 12.7mm. The RSC converted a substantial 50% of inflow to media flow at the second cell; however, the media flow entirely reemerged as surface flow in the saturated downstream pools. Small but statistically significant reductions in event mean concentrations occurred: 17% total suspended sediment (TSS), 17% total phosphorus (TP), and 3% total nitrogen (TN). Water quality improvements occurred primarily between the upstream and second cell, indicating limited processing by the wetter downstream pools. Comparisons between inter-event outflow grab samples and storm event outflow concentrations show nitrogen export during inter-event periods (47% increase in TN concentration). Due to elevated inter-event concentrations, overall mass loading of nitrogen increased. Hydrologic and water quality benefits were garnered only in the first three cells where groundwater intrusion was minimal. Future implementations of RSC are encouraged to account for seasonal high water table elevations that interact with the RSC media and adequately size pool and sand layer capture volumes.

Elucidating terrestrial nutrient sources to a coastal lagoon, Chincoteague Bay, Maryland, USA

Long-term non-linear ecosystem-scale changes in water quality and biotic communities in coastal lagoons have been associated with intensification of anthropogenic pressures. In light of incipient changes in Johnson Bay (an embayment of Chincoteague Bay, Maryland-Virginia, USA), examination of nitrogen sources was conducted through synoptic water quality monitoring, stable nitrogen isotope signatures (δ15N) of in situ bioindicators, and denitrification estimates. These data were placed in the context of long-term and broader spatial analyses. Despite various watershed protection efforts, multiyear summer time studies (2004–2007) suggested that high levels of terrestrially derived nutrients still enter Johnson Bay. Total nitrogen concentrations in Johnson Bay were 132% the concentrations in the broader Chincoteague Bay during the late 1970s (mean 2004–2007 was 40.0 – 73.2 μM). Comparing total nitrogen concentrations in Johnson Bay to St. Martin River (consistently the most eutrophic region of these coastal bays), Johnson Bay has increased from 62.5% to 82.5% of the concentrations in St. Martin River during the late 1970s. Though specific sources of nitrogen inputs have not yet been definitively identified, the long-term increase in total nitrogen concentrations occurred despite increased and continued conservation and protection measures. We suggest that investigating nutrient sources can reveal potentially ineffective nutrient policies and that this knowledge can be applied towards other coastal lagoons.

Long-Term Water Quality Trends in the Lake Okeechobee Watershed, Florida

A Seasonal Kendall Tau test was used to determine statistical significance of mean monthly total phosphorus (TP) and total nitrogen (TN) concentration trends during the time period of 1991–2007, by station and basin at 35 long-term water quality monitoring stations located within the northern Lake Okeechobee watershed. One drainage basin (S-154) had a significant decreasing trend for mean monthly TP concentrations during the analysis period. A significant increase in TN concentrations was detected for four basins during this same time period. The S-154 basin which had the significant decreasing trend for TP also had the highest percentage of implemented Best Management Practices (BMPs) and the most rigorous types of nutrient control projects. These findings emphasize the need for continued implementation of intensive P management strategies. The increasing trend in TN for this watershed signals the need for added focus on reductions of TN in future nutrient source control projects and BMPs.

Hydrological and nitrogen distributed catchment modeling to assess the impact of future climate change at Trichonis Lake, western Greece

According to regional climatic models, climate change may affect Mediterranean lakes significantly in terms of water availability and quality. Trichonis Lake catchment covers a semi-mountainous area of 403 km2 including the largest Greek lake by volume (2.6 × 109 m3), located in western Greece. The impact of climate change on the hydrology and water quality of the lake, in terms of lake water level and nutrient concentrations, has been assessed. Water balance estimates and geographical information system tools were then used to set up a physically based, spatially distributed model. The calibrated model was simulated for two future scenarios specified by the Intergovernmental Panel on Climate Change: A2 (pessimistic) and B2 (more optimistic), which involved temperature/evaporation/evapotranspiration increase and small precipitation decrease. The model was calibrated efficiently for the 1990–1992 period. The two basic climatic scenarios illustrated that the responses of the lake water levels will show a decrease of 24.2 and 12 cm, respectively, and an increase of total nitrogen concentrations by 3.4 and 10%, in relation to the early 1990s values. These important findings suggest that mitigation and optimum management plans should be developed to eliminate the aforementioned climate change impacts and further research should follow.

Evaluating Cover Crops (Sudex, Sunn Hemp, Oats) for Use as Vegetative Filters to Control Sediment and Nutrient Loading From Agricultural Runoff in a Hawaiian Watershed1

Abstract: A study was conducted to determine the effects of three land covers (sunn hemp –Crotalaria juncea, sudex, a sorghum‐sudangrass hybrid –Sorghum bicolor x S. bicolor var. sudanese, and common oats –Avena sativa) planted as vegetative filter strips on the reduction of sediment and nutrient loading of surface runoff within the Kaika‐Waialua watershed on the island of Oahu, Hawaii. Runoff samples were collected and analyzed for total suspended solids (TSS), total dissolved solids (TDS), phosphorous, and three forms of nitrogen (nitrate, ammonium, total nitrogen). Study results show that during seven out of 10 runoff events, the three cover crop treatments significantly reduced TSS as compared to the fallow treatment. Average removal efficiencies were 85, 77, and 73% for oats, sunn hemp, and sudex, respectively, as compared to the fallow treatment. Nutrient concentrations were low with phosphorous concentrations, lower than 1 (μg/ml) for all treatments, and total nitrogen (TN) concentrations below 7 (μg/ml) except in the sunn hemp treatment, where TN concentrations were less than 10 (μg/ml). Results of analysis of TDS showed that the cover crop treatments did not decrease dissolved solids concentrations in comparison with the fallow treatment. Analysis of nutrient concentrations in runoff samples did not detect any significant decreases in phosphorous, nitrogen, ammonium, or TN concentrations in comparison to the fallow treatment. However, a significant increase in TN concentrations in the sunn hemp treatment was detected and showed the nitrogen fixing capacity of sunn hemp. No treatment effects on runoff volume were detected, and runoff volumes were directly correlated with rainfall amounts showing no crops significantly impacted soil infiltration rates. These results were attributed to extremely low soil hydraulic conductivities (0.0001‐7 cm/day at the soil surface, 15 and 30 cm below the soil surface). This study showed that cover crops planted as vegetative filters can effectively reduce sediment loads coming from idle and fallow fields on moderately steep volcanically derived highly weathered soils.

Changes in N and P limitation induced by water level fluctuations in Nature Park Kopački Rit (Croatia): nutrient enrichment bioassay

The importance of nutrients as limiting factors might vary in environments with different limnological characteristics. In this article we evaluate the effect of frequency and duration of flooding on nutrient limitation in a riparian floodplain. Variations in N and P limitations were studied in the period of low (2003) and high (2004) water level in two different floodplain habitat types in the Nature Park Kopacki Rit (Croatia), a floodplain area of the Danube River. In 2003 and 2004, the limnological characteristics of floodplain lake (Lake Sakadas) and the channel (Stara Drava) differed due to their hydrological regimes. Potential for nutrient limitation was determined by DIN:TP and TN:TP ratios, while the actual nutrient limitation was assessed by nutrient enrichment bioassay. A change from non-limited to N-limited conditions in the channel, and consistent actual N limitation in the lake was determined by the nutrient enrichment experiment. Of the two ratios, DIN:TP matched better with the bioassay data. Phosphorus limitation was only occasionally evident. Changes in trophic conditions from hypereutrophy to eutrophy (between low and high water levels) reflected the importance of the hydrologic regime as a factor which can modify the trophic state of Lake Sakadas. Compared with 2003, the increase of total nitrogen concentrations in 2004 calls attention to the importance of nitrogen inputs from the Danube to the system with excessive phosphorus concentrations.

Multi-proxy evidence of long-term changes in ecosystem structure in a Danish marine estuary, linked to increased nutrient loading

This paper presents a study of changes in eutrophication over the past 100 years in a fertile estuary. The Danish estuary Mariager Fjord is a long, narrow sill-fjord with a permanently anoxic basin. In 1997 anoxia spread from the basin to the entire inner estuary, killing almost all eukaryotes and prompting debate on the causes. This paper reports a multi-proxy survey of 210Pb-dated sediment cores from the anoxic basin. Analyses of diatoms, dinoflagellates, pigments and geochemical proxies were used to determine changes in ecosystem structure over the past 100 years. The aim was to establish ‘base-line conditions’, for management purposes, of the biological structure prior to 1900, and to examine possible causes of changes observed. Geochemical proxies total nitrogen (TN), total carbon (TC) and biogenic silica (BSi) were consistently high throughout the sediment record. Increased concentrations of pigments and natural isotopes (δ 13C, δ 15N) suggested increasing production and nutrient loading. The main changes in the biological proxies occurred between 1915 and the 1940s, and indicated that the estuary has been somewhat eutrophic since 1900, but that the eutrophication process increased over the past 100 years. A reconstruction of TN concentration by a diatom-based transfer function supports this interpretation, with inferred TN ca. 1900 around 60 μmol l −1, and an increase in TN concentration over the past century to ca. 130 μmol l −1 by 1995. Inferred TN decreased to ca. 100 μmol l −1 by 2001, similar to present day monitoring data.

Spatial and temporal patterns of nitrogen concentrations in pristine and agriculturally-influenced prairie streams

Long-term data on nitrogen chemistry of streams draining Konza Prairie Biological Station (Konza), Kansas were analyzed to assess spatial and temporal patterns and examine the influence of agricultural activity on these patterns. Upland watersheds of Konza are predom- inantly tallgrass prairies, but agricultural fields and riparian forests border the lower reaches of the streams. We have up to 11 years of data in the relatively pristine upland reaches and 4 years of data on wells and downstream reaches influenced by fertilized croplands. Seasonal and spatial patterns in total nitrogen (TN) concentrations were driven largely by changes in the nitrate (NO 3 ) concentrations. A gradient of increasing NO 3 concentrations occurred from pristine upland stream reaches to the more agriculturally-influenced lowland reaches. Nitrate concentrations varied seasonally and were negatively correlated with discharge in areas influenced by row-crop agriculture (p = 0.007). The NO 3 concentrations of stream water in lowland reaches were lowest during times of high precipitation, when the relative influ- ence of groundwater drainage is minimal and water in the channel is primarily derived from upland prairie reaches. The groundwater from cropland increased stream NO 3 concentrations about four-fold during low-discharge periods, even though significant riparian forest corridors existed along most of the lower stream channel. The minimum NO 3 concentrations in the agriculturally influenced reaches were greater than at any time in prairie reaches. Analysis of data before and after introduction of bison to four prairie watersheds revealed a 35% increase of TN concentrations (p < 0.05) in the stream water channels after the introduction of bison. These data suggest that natural processes such as bison grazing, variable discharge, and local- ized input of groundwater lead to variation in NO 3 concentrations less than 100-fold in prairie streams. Row-crop agriculture can increase NO 3 concentrations well over 100-fold relative to pristine systems, and the influence of this land use process over space and time overrides natural processes.

Change in Primary Production in Lake Kasumigaura(1986-1989)Accompanied by Transition of Dominant Species.

Seasonal changes in phytoplankton species and primary production were inves-tigated from 1986 to 1989 in Lake Kasumigaura. The large bloom of Microcystis, which had occurred every summer up to 1986, was not observed from 1987 to 1989, and Planktothrix (Oscillatoria) agardhii, Phormidium tenue and Gomphosphaeria lacustris var. compacta co-dominated in addition to Microcystis. In particular, Planktothrix became the most abundant from September 1987 to January 1988 and in the summer and autumn of 1988 and 1989.The values for Pmex and the initial slope of the P-I curve in summer during this period did not differ from those observed from 1981 to 1985. However, the chlorophyll a concentrations and primary production in the summer and autumn from 1987 to 1989 were apparently lower than those of the previous 7 years. This phenomenon was closely related to the low abundance of Microcystis during this period. Use of multiple stepwise regression suggested that gross primary production was determined mostly by solar radiation, water temperature and/or chlorophyll a concentration, results similar to those obtained for 1981-1985.The annual means of total nitrogen (TN) concentrations in the lake water have increased since 1986, although those of total phosphorus (TP) have scarcely changed (AIZAKI et al. 1990). The present study showed an interesting phenomenon: the primary production decreased because of the species shift from Microcystis to Plan-ktothrix, in spite of the increase of TN concentrations.

Changes in soil nitrogen concentration around Alnusglutinosa in a mixed, short-rotation plantation with hybrid Populus

Soil nitrogen concentration around AlnusglutinosaL. (Gaertn.) stems differed significantly both spatially and with the proportion of hybrid Populus in a 4-year-old mixed plantation near Rhinelander, Wisconsin. Single rows of Alnus bounded by adjacent rows of hybrid Populus had the greatest increase and concentration of nitrogen in the top 16 cm of soil. Alnus, with an adjacent row of Populus and an adjacent row of Alnus, had less total nitrogen concentration in the soil and there was little significant increase in total nitrogen concentration. Where Alnus trees had a row of Alnus on either side, the total nitrogen concentration was least, having decreased significantly from concentrations in soil prior to tree planting. Soil nitrogen accretion and concentration was always highest in the top 4 cm of soil. Results are consistent with speculation that competition-induced stress from shading by Populus or Populus allelochemicals results in early accretion of nitrogen in soil around Alnus intermixed with Populus.

Elevation of serum calcium concentration and changes in other blood parameters after death

A postmortem rise in serum total and ultra-filterable calcium concentrations was observed in man and in the rat, the changes occurring more rapidly at room temperature than at 4°C. The mechanism responsible for this rise was investigated in the rat by measuring the concentrations of magnesium, sodium, potassium, chloride, and nitrogen in serum, whole blood, and skeletal muscle. Among the changes observed were an increase in total nitrogen concentration in serum and whole blood, a decrease in total nitrogen concentration in muscle, an increase in red cell volume, and a decrease in the extracellular fluid volume, as measured by inulin. It is concluded that postmortem hypercalcemia is due mainly, to hemoconcentration resulting from failure of the “sodium pump,” movement of sodium and chloride ions into cells, a temporary rise in osmotic pressure within the cells, and consequent movement of water from the extracellular fluid compartment into cells.