Elevated Nitrogen Research Articles

Phosphorus limitation on photosynthesis of two dominant understory species in a lowland tropical forest

Aims Elevated nitrogen (N) deposition in tropical regions may accelerate ecosystem phosphorus (P) limitation. However, it is not explicitly addressed that how changes in soil N and P availability affect foliar nutrients and photosynthesis of plants in tropical forests. In this study, we examined the effects of N and P additions on foliar nutrients and net photosynthesis of two dominant understory species, Randia canthioides (R. canthioides) and Cryptocarya concinna (C. concinna) in an N-saturated old-growth tropical forest (>400-year-old) in south ern China. Methods A full factorial NP addition experiment (2

Isotopic evidence for nitrogen mobility in peat bogs

Elevated nitrogen (N) input may reduce carbon (C) storage in peat. Under low atmospheric deposition, most N is bound in the moss layer. Under high N inputs, Sphagnum is not able to prevent penetration of dissolved N to deeper peat. Nitrogen may become available to the roots of invading vascular plants. The concurrent oxygenation of deeper peat layers, along with higher supply of labile organic C, may enhance microbial decomposition and lead to peat thinning. The resulting higher emissions of greenhouse gases may accelerate global warming. Seepage of N to deeper peat has never been quantified. Here we present evidence for post-depositional mobility of atmogenic N in peat, based on natural-abundance N isotope ratios. We conducted a reciprocal peat transplant experiment between two Sphagnum-dominated peat bogs in the Czech Republic (Central Europe), differing in anthropogenic N inputs. The northern site VJ received as much as 33kgNha−1yr−1 via spruce canopy throughfall. The southern site was less polluted (17.6kgNha−1yr−1). Isotope signatures of living moss differed between the two sites (δ15N of −3‰ and −7‰ at VJ and CB, respectively). After 18months, an isotope mass balance was constructed. In the CB-to-VJ transplant, a significant portion of original CB nitrogen (98–31%) was removed and replaced by nitrogen of the host site throughout the top 10cm of the profile. Nitrogen, deposited at VJ, was immobilized in imported CB peat that was up to 20years old. Additionally, we compared N concentration and N accumulation rates in 210Pb-dated peat profiles with well-constrained data on historical atmospheric N pollution. Nationwide N emissions peaked in 1990, while VJ exhibited the highest N content in peat that formed in 1930. This de-coupling of N inputs and N retention in peat might be interpreted as a result of translocation of dissolved pollutant N downcore, corroborating our δ15N results at VJ and CB. Data from a variety of peat bogs along pollution and climatic gradients would be needed to test to what extent the record of atmospheric N inputs in peat is overprinted by variable, locally-controlled decomposition rates.

Impacts of acid deposition, ozone exposure and weather conditions on forest ecosystems in Europe: an overview

In 1994, a “Pan-European Programme for Intensive and Continuous Monitoring of Forest Ecosystems” started to contribute to a better understanding of the impact of air pollution, climate change and natural stress factors on forest ecosystems. The programme today counts approximately 760 permanent observation plots including near 500 plots with data on both air quality and forest ecosystem impacts. This paper first presents impacts of air pollution and climate on forests ecosystems as reported in the literature on the basis of laboratory and field research. Next, results from monitoring studies, both at a European wide scale and related national studies, are presented in terms of trends and geographic variations in nitrogen and sulphur deposition and ozone concentrations and the impacts of those changes in interaction with weather conditions on (i) water and element budgets and nutrient-acidity status, (ii) forest crown condition, (iii) forest growth and carbon sequestration and (iv) species diversity of the ground vegetation. The empirical, field based forest responses to the various drivers are evaluated in view of available knowledge. Analyses of large scale monitoring data sets show significant effects of atmospheric deposition on nutrient-acidity status in terms of elevated nitrogen and sulphur or sulphate concentrations in forest foliage and soil solution and related soil acidification in terms of elevated aluminium and/or base cation leaching from the forest ecosystem. Relationships of air pollution with crown condition, however, appear to be weak and limited in time and space, while climatic factors appear to be more important drivers. Regarding forest growth, monitoring results indicate a clear fertilization effect of N deposition on European forests but the field evidence for impacts of ambient ozone exposure on tree growth is less clear.

Increased inorganic nitrogen leaching from a mountain grassland ecosystem following grazing removal: a hangover of past intensive land-use?

Heathlands and grasslands occur in montane regions, naturally or due to anthropogenic land-use. These are typically nutrient-poor but exposure to elevated nitrogen deposition and intensive livestock grazing causes large-scale ecological change. We studied the long-term implications of grazing removal on soil and drainage water biogeochemistry and the implications for nitrogen cycling in 50-year replicated grazing exclosures on a montane grassland exposed to high rates of ambient nitrogen deposition. Evidence of ‘ecosystem recovery’ represented by successional change from graminoid to shrub-dominance after cessation of grazing was not reflected in the soil biogeochemistry. Cessation of grazing had a negative impact, with increased soil extractable and soil solution nitrate concentrations; an apparent shift towards a more nitrogen-rich, bacterially dominated microbial community; and the acidification of soils and leachate. The increase in nitrate leaching appears to have been counterbalanced by a decrease in dissolved organic nitrogen leaching, approximately maintaining the overall nitrogen balance of the system, whilst apparently altering ecosystem functioning. High rates of organic matter cycling and inorganic nitrogen uptake in grazed grassland may have sustained ecosystem N limitation under elevated nitrogen deposition. Grazing removal caused long-term over-supply of nitrogen from mineralisation of enriched organic matter, exacerbated by continued high nitrogen deposition, exceeding the uptake demand of heath vegetation and resulting in nitrification and nitrate leaching. This disequilibrium between vegetation and soil following grazing removal has implications for restoration after periods of intensive grazing. Grazing may not simply leave a legacy of nutrient enrichment but its cessation may trigger nitrogen saturation and soil and freshwater eutrophication and acidification which counteract the immediate benefits of natural vegetation recovery. Long term, nitrogen saturation of abandoned grasslands is likely to reduce ecosystem resilience to invasion by nitrophilous species, pathogen attack and vulnerability to environmental pressures such as climate change. We conclude that partial and/or phased reduction in grazing levels may permit the more synchronised recovery of soils and vegetation, thereby avoiding imbalances between nitrogen supply and nitrogen demand and detrimental ecological effects.

Protective potential of Tamarindus indica against gentamicin-induced nephrotoxicity

Context: Gentamicin is an antibiotic that is effective against Gram-negative microorganisms. However, its clinical applications are often limited due to nephrotoxic effects.Objective: This study investigated the protective effects of aqueous-ethanol extract of Tamarindus indica L. (Leguminosae) fruits against gentamicin-induced renal toxicity.Materials and methods: A daily dose of 200 mg/kg of 70% aqueous-ethanol extract derived from T. indica was employed in male rabbits as a co-therapy with gentamicin (80 mg/kg) for a period of three weeks. Serum and urinary renal function parameters and histological assessments were carried out and compared with one way analysis of variance (Graphpad prism version 5.00, Graphpad Software, San Diego, CA).Results: The results showed that gentamicin-treated animals had significantly elevated blood urea nitrogen (54.1 ± 2.6 mg/dl), serum creatinine (4.0 ± 0.1 mg/dl), serum uric acid (2.3 ± 0.1 mg/dl) and urinary protein excretion (3.8 ± 0.3 mg/dl) with a fall in body weight (10 ± 1%), creatinine clearance (0.7 ± 0.09 ml/min), serum potassium (3.4 ± 0.1 mEq/l), serum calcium (7.6 ± 0.2 mg/dl), urinary volume (126 ± 9 ml/24 h) and urinary lactate dehydrogenase secretion (103.1 ± 4.2 U/l). However, animals treated by co-therapy with gentamicin and T. indica had significantly improved renal structure and function.Discussion and conclusion: Co-therapy of 200 mg/kg/d of T. indica for a period of three weeks successfully prevented functional and morphological derangements caused by gentamicin as assessed by different renal function parameters and histological examinations.

Effects of elevated CO<inf>2</inf> concentration and nitrogen addition on soil carbon stability in southern subtropical experimental forest ecosystems

Aims The influence of elevated atmospheric CO2 concentration and nitrogen(N) addition on soil carbon pool is one of the foci among international ecological research communities. The changes of soil carbon pool induced by atmospheric CO2 concentration and/or N deposition will lead to changes in atmospheric carbon pool and thus the global climate change. However, few studies have been carried out in the subtropical China. Our objective was to understand the effect of elevated CO2 concentration and N addition on soil carbon stability in south subtropical experimental forests. Methods Experimental forest ecosystems were constructed in open top chambers. Six native tree species in southern China were planted in these experimental forest ecosystems. The species were exposed to elevated CO2 and N addition in the open top chambers beginning in May 2005. The four treatments were: elevated CO2 and high N addition(CN), elevated CO2 and ambient N deposition(CC), high N addition and ambient CO2(NN), and ambient CO2 and ambient N deposition(CK). The elevated CO2 was(700 ± 20) μmol·mol–1. The total amount of added NH4NO3-N was 100 kg N·hm–2·a–1. In January 2010, soil samples were collected from the open top chambers and then relevant variables were measured. Important findings Elevated CO2 concentration and N addition(CN) effectively increased the soil total organic carbon in different soil layers, among which the increases in the lower soil layers(5–60 cm) were statistically significant. Different components of the active organic carbon pool differed in the responses to treatments. The differences in microbial biomass carbon were significant in the 0–5 cm, 5–10 cm and 10–20 cm soil layers amongthe treatments, and the readily oxidized carbon showed significant responses to the elevated CO2 concentration and N addition treatments in the 10–20 cm and 20–40 cm soil layers, while there was no significant difference in the dissolved organic carbon among different treatments in all the soil layers. The responses of carbon in different aggregate fractions differed among the treatments. The carbon in the 250–2 000 μm aggregates was significantly different among treatments in the 20–40 cm and 40–60 cm soil layers. The carbon in the 53–250 μm aggregates was susceptible to treatments in the 40–60 cm soil layer as both the CC and NN treatments facilitated the chronic carbon accumulation in deeper soil layers, especially under the CN treatment. Carbon in the 53 μm fraction showed significant differences among treatments in deeper soil layers(10–20 cm, 20–40 cm and 40–60 cm). In conclusion, elevated CO2 concentration and N addition increased soil organic carbon in the experimental forest ecosystems, and facilitated the accumulation of carbon in micro-aggregates and silt-clay fraction in deep soil layers, thus strengthened the stability of soil organic carbon pool.

FACTORS CONTROLLING KEY NITROGEN FLUXES IN GRASSLAND ECOSYSTEMS: CASE STUDIES - SOUTHERN ROMANIA

Enhanced nitrogen inputs to both terrestrial and aquatic ecosystems affects biodiversity at all its levels. Grasslands provide a complex range of functions, due to their wide representation throughout terrestrial ecosystems. Numerous studies demonstrate soil acidification, eutrophication and species richness reduction as a result of elevated reactive nitrogen availability. The present study aims to assess soil nitrogen stocks and transformations for two Romanian grasslands during November 2011 – November 2013, integrating the microbial population dynamics of two important functional groups involved in terrestrial nitrogen cycle: ammonifiers and denitrifiers. Our research focused on pristine systems, as well as on an experiment that simulated high nitrogen inputs of 100 kg N/ha/year (during 2012 and 2013) for one of the two selected study areas.

Coexistence of nitrifying, anammox and denitrifying bacteria in a sequencing batch reactor

Elevated nitrogen removal efficiencies from ammonium-rich wastewaters have been demonstrated by several applications, that combine nitritation and anammox processes. Denitrification will occur simultaneously when organic carbon is also present. In this study, the activity of aerobic ammonia oxidizing, anammox and denitrifying bacteria in a full scale sequencing batch reactor, treating digester supernatants, was studied by means of batch-assays. AOB and anammox activities were maximum at pH of 8.0 and 7.8–8.0, respectively. Short term effect of nitrite on anammox activity was studied, showing nitrite up to 42 mg/L did not result in inhibition. Both denitrification via nitrate and nitrite were measured. To reduce nitrite-oxidizing activity, high NH3-N (1.9–10 mg NH3-N/L) and low nitrite (3–8 mg TNN/L) are required conditions during the whole SBR cycle. Molecular analysis showed the nitritation-anammox sludge harbored a high microbial diversity, where each microorganism has a specific role. Using ammonia monooxygenase α–subunit (amoA) gene as a marker, our analyses suggested different macro- and micro-environments in the reactor strongly affect the AOB community, allowing the development of different AOB species, such as N. europaea/eutropha and N. oligotropha groups, which improve the stability of nitritation process. A specific PCR primer set, used to target the 16S rRNA gene of anammox bacteria, confirmed the presence of the “Ca. Brocadia fulgida” type, able to grow in presence of organic matter and to tolerate high nitrite concentrations. The diversity of denitrifiers was assessed by using dissimilatory nitrite reductase (nirS) gene-based analyses, who showed denitifiers were related to different betaproteobacterial genera, such as Thauera, Pseudomonas, Dechloromonas and Aromatoleum, able to assist in forming microbial aggregates. Concerning possible secondary processes, no n-damo bacteria were found while NOB from the genus Nitrobacter was detected.

Reducing Runoff Loss of Applied Nutrients in Oil Palm Cultivation Using Controlled-Release Fertilizers

Controlled-release fertilizers are expected to minimize nutrient loss from crop fields due to their potential to supply plant-available nutrients in synchrony with crop requirements. The evaluation of the efficiency of these fertilizers in tropical oil palm agroecological conditions is not yet fully explored. In this study, a one-year field trial was conducted to determine the impact of fertilization with water soluble conventional mixture and controlled-release fertilizers on runoff loss of nutrients from an immature oil palm field. Soil and nutrient loss were monitored for one year in 2012/2013 under erosion plots of 16 m2on 10% slope gradient. Mean sediments concentration in runoff amounted to about 6.41 t ha−1. Conventional mixture fertilizer posed the greatest risk of nutrient loss in runoff following fertilization due to elevated nitrogen (6.97%), potassium (13.37%), and magnesium (14.76%) as percentage of applied nutrients. In contrast, this risk decreased with the application of controlled-release fertilizers, representing 0.75–2.44% N, 3.55–5.09% K, and 4.35–5.43% Mg loss. Meanwhile, nutrient loss via eroded sediments was minimal compared with loss through runoff. This research demonstrates that the addition of controlled-release fertilizers reduced the runoff risks of nutrient loss possibly due to their slow-release properties.

Nutrient limitation in three lowland tropical forests in southern China receiving high nitrogen deposition: insights from fine root responses to nutrient additions.

Elevated nitrogen (N) deposition to tropical forests may accelerate ecosystem phosphorus (P) limitation. This study examined responses of fine root biomass, nutrient concentrations, and acid phosphatase activity (APA) of bulk soil to five years of N and P additions in one old-growth and two younger lowland tropical forests in southern China. The old-growth forest had higher N capital than the two younger forests from long-term N accumulation. From February 2007 to July 2012, four experimental treatments were established at the following levels: Control, N-addition (150 kg N ha–1 yr–1), P-addition (150 kg P ha–1 yr–1) and N+P-addition (150 kg N ha–1 yr–1 plus 150 kg P ha–1 yr–1). We hypothesized that fine root growth in the N-rich old-growth forest would be limited by P availability, and in the two younger forests would primarily respond to N additions due to large plant N demand. Results showed that five years of N addition significantly decreased live fine root biomass only in the old-growth forest (by 31%), but significantly elevated dead fine root biomass in all the three forests (by 64% to 101%), causing decreased live fine root proportion in the old-growth and the pine forests. P addition significantly increased live fine root biomass in all three forests (by 20% to 76%). The combined N and P treatment significantly increased live fine root biomass in the two younger forests but not in the old-growth forest. These results suggest that fine root growth in all three study forests appeared to be P-limited. This was further confirmed by current status of fine root N:P ratios, APA in bulk soil, and their responses to N and P treatments. Moreover, N addition significantly increased APA only in the old-growth forest, consistent with the conclusion that the old-growth forest was more P-limited than the younger forests.

Elevated Blood Urea Nitrogen and Medical Outcome of Psychiatric Inpatients

Elevated blood urea nitrogen (BUN) is associated with increased severity of illness and mortality, but its predictive value has not been studied in patients admitted to free-standing psychiatric hospitals. To determine the clinical outcome of psychiatric inpatients with elevated BUN on admission and to create a quantitative method of using BUN for predicting deteriorations requiring transfers of psychiatric inpatients to a general hospital we conducted a retrospective cohort study of 939 adults consecutively admitted to a free-standing psychiatric hospital in 2010. Transfer to a general hospital was used as a proxy marker for poor medical outcome. The score Age (years) plus BUN (mg/dL) was used in sensitivity analyses to identify patients with medical deterioration in derivation (N = 523) and validation (N = 414) samples. Fifty-two (5.5%) patients had admission azotemia (BUN >25 mg/dL). Medical deteriorations requiring emergency transfer to a general hospital occurred in 24 (46.2%; 95% confidence interval = 32.6-49.8%) of azotemic patients and 112 (12.6%; 95% confidence interval = 10.4-14.8%) of those with normal BUN (p < 0.0001). Age + BUN ≥ 90 identified 51 transferred patients and had positive and negative predictive values of 39.8 and 89.5%, respectively, in the entire sample. We conclude that psychiatric inpatients with BUN >25 mg/dL or Age + BUN ≥ 90 are at risk for medical deterioration. Free-standing psychiatric hospitals should develop models of care requiring frequent, scheduled medical follow-up and enhanced monitoring for this vulnerable populations.

Bioenergy that supports ecological restoration

Bioenergy development can offer beneficial ecological and economic synergies through the expansion of ecological restoration projects. Such synergies are demonstrated by means of a case study conducted in central Washington State, where a 52.4‐ha ecological restoration site on the Yakama Reservation generated 34 mega‐grams (Mg) of invasive tree biomass per hectare, costing $988 ha−1. A geospatial model of transportation costs estimated that extracted invasive tree biomass can generate revenues throughout 1103 803 ha when delivered to a proposed bioenergy facility in White Swan, Washington, providing 53 000–180 000 Mg of biomass per year for several decades. Thermochemical analyses revealed that the elevated nitrogen, sulfur, and ash content in two prolific invasive trees – Russian olive (Elaeagnus angustifolia) and salt cedar (Tamarix spp) – will limit demand for either of these invasive species. We compare our regional data to national estimates, and show the broader potential for expanding ecological restoration activities and biomass supplies through the revenues generated by the sale of invasive tree wood‐waste into bioenergy markets.

Impact of Blood Urea Nitrogen on In-Hospital Mortality in Patients with Acute Heart Failure

Backgrounds: In heart failure (HF), several studies have demonstrated that elevated blood urea nitrogen (BUN) is associated with adverse outcomes. This purpose is to assess the relationship between BUN and in-hospital outcomes in patients with HF. Methods: Objectives were 281 cases with HF admitted in ICU (77610 years, Male 155) from April 2007 through September 2008, in which IHD, valve disease, cardiomyopathy, tachycardia, hypertension, bradycardia, acute coronary syndrome and others were 111, 42, 36, 31, 18, 11, 8 and 24 cases. The relationships between in-hospital outcomes and hemodynamics, anemia, renal function, serum electrolytes, neurohormonal factors at admission, pre-hospital medication were evaluated retrospectively. Results: Systolic blood pressure (SBP), uric acid, BUN were 150637mmHg, 7.162.5mg/dl, 28.4618.3mg/dl (median 23.0). Median of plasma aldosterone concentration (PAC) and plasma rennin activity (PRA) were 5.3pg/ml and 1.7ng/ml/h. Death in hospital was 27 cases (9.6%). Non-survivors have significantly lower SBP, higher PAC, higher PRA, higher uric acid and higher BUN than survivors in-hospital (p!0.05). In Cox’s proportional hazards analysis, BUNO23mg/dl was an independent predictive factor of in-hospital death (HR 1.181, 95%CI 0.067-0.488, p!0.01). Age, SBP, uric acid, PACO5.3, PRAO1.7, renin-angiotensin blockers before admission were not independent predictive factor of in-hospital death. Conclusion: These results may suggest that higher BUN is the risk factor of short-term mortality in acute HF patients.

Nitrogen-oxide emissions from tropical forest soils exposed to elevated nitrogen input strongly interact with rainfall quantity and seasonality

In tropical forests, multi-year studies on the impact of chronic nitrogen (N) enrichment on soil N-oxide fluxes are lacking. Our objectives were to: (1) assess the changes in soil N-oxide (NO+N2O) fluxes from a montane forest in response to 3–4 years of N addition and compare these to the response of a lowland forest with 11–12 years of N addition, (2) quantify the contributions of nitrification and denitrification to nitrous oxide (N2O) emissions, and (3) assess how deep in the soil profile the N2O concentrations are affected by N input. These measurements were conducted in montane and lowland forests in Panama in 2008–2009, which covered the last 2 years of a 4-year investigation that started in 2006. Each forest had a control and N addition treatment (125 kg urea N ha−1 year−1) with four replicate plots (1,600 m2 each) per treatment. N-oxide emissions from the montane forest started to increase within the first 2 years of treatment and continued to increase in the 3rd and 4th years of N addition, during which the emissions were already equivalent to those from the lowland forest with 11–12 years of N addition. The large N-oxide response of the montane forest to N addition were due to the large increases in gross nitrification rates in the organic layer and the high moisture contents of the mineral soil due to the high rainfall (5.5 ± 0.2 m year−1). In the lowland forest (2.7 ± 0.1 m rain year−1), N-oxide response to N addition was more pronounced in wet years (i.e. 2006–2007 with 5–17 % higher rainfall than average) than in dry years (i.e. 2008–2009 with 5–26 % lower rainfall than average). Denitrification was the dominant source of N2O not only for the organic layer and the top 5 cm of mineral soil but possibly also for the entire 2 m depth. Soil–air N2O concentrations were elevated by N addition down to at least 2 m. Our results suggest that the best indicators of these responses were the presence of an organic layer and rainfall quantity and seasonality.

Stable isotopes document resource partitioning and effects of forest disturbance on sympatric cheirogaleid lemurs

The future of Madagascar's forests and their resident lemurs is precarious. Determining how species respond to forest fragmentation is essential for management efforts. We use stable isotope biogeochemistry to investigate how disturbance affects resource partitioning between two genera of cheirogaleid lemurs (Cheirogaleus and Microcebus) from three humid forest sites: continuous and fragmented forest at Tsinjoarivo, and selectively logged forest at Ranomafana. We test three hypotheses: (H1) cheirogaleids are unaffected by forest fragmentation, (H2) species respond individually to disturbance and may exploit novel resources in fragmented habitat, and (H3) species alter their behavior to rely on the same key resource in disturbed forest. We find significant isotopic differences among species and localities. Carbon data suggest that Microcebus feed lower in the canopy than Cheirogaleus at all three localities and that sympatric Cheirogaleus crossleyi and C. sibreei feed at different canopy heights in the fragmented forest. Microcbus have higher nitrogen isotope values than Cheirogaleus at all localities, indicating more faunivory. After accounting for baseline isotope values in plants, our results provide the most support for H3. We find similar isotopic variations among localities for both genera. Small differences in carbon among localities may reflect shifts in diet or habitat use. Elevated nitrogen values for cheirogaleid lemurs in fragments may reflect increased arthropod consumption or nutritional stress. These results suggest that cheirogaleids are affected by forest disturbance in Eastern Madagascar and stress the importance of accounting for baseline isotopic differences in plants in any work comparing localities.

Chemical Composition of Salmon Ovary Outer Membrane and Its Protein Increases Fecal Mucins Content in C57BL/6J and Type 2 Diabetic/Obese KK-Ay Mice

Salmon ovary outer membrane (SOM) is a byproduct of the salmon industry; however, the effective utilization of SOM for food materials and supplements is anticipated as the demand for fish and seafood increases worldwide. The purposes of the present study were to assess the chemical composition of SOM, the characteristics of SOM protein (SOMP), and its effects on serum and fecal biochemical parameters in mice. SOM contained high levels of crude protein (61.9 g/100 g) and crude lipid (18.9 g/100 g). The protein pattern of SOMP was different from those of fish muscle protein and roe; it was abundant in collagen, as calculated from the hydroxyproline content. In addition, SOMP exhibited lower protein digestibility during in vitro digestion analyses compared with casein. Male C57BL/6J and KK-Ay mice were fed a casein-based semi-purified diet or a diet with replacement of part of the dietary protein (50%) by SOMP for four weeks. Mice fed the diet containing SOMP showed elevated fecal nitrogen and mucins contents and reduced levels of serum liver injury markers and fecal ammonia. These results show for the first time that chemical composition of SOM, and SOMP, contain a resistant protein fraction and a large amount of collagen. Therefore, SOM is a potential source of marine collagen and functional food material for promoting the health of the liver and colon.

Exchange of Nitrogen and Phosphorus Between a Shallow Lagoon and Coastal Waters

West Falmouth Harbor, a shallow lagoon on Cape Cod, has experienced a threefold increase in nitrogen load since the mid- to late 1990s due to input from a groundwater plume contaminated by a municipal wastewater treatment plant. We measured the exchange of nitrogen and phosphorus between the harbor and the coastal waters of Buzzards Bay over several years when the harbor was experiencing this elevated nitrogen load. During summer months, the harbor not only retained the entire watershed nitrogen load but also had a net import of nitrogen from Buzzards Bay. During the spring and fall, the harbor had a net export of nitrogen to Buzzards Bay. We did not measure the export in winter, but assuming the winter net export was less than 112 % of the load, the harbor exported less than half of the watershed nitrogen load on an annual basis. For phosphorus, the harbor had a net import from coastal waters in the spring and summer months and a net export in the fall. Despite the large increase in nitrogen load to the harbor, the summertime import of phosphorus from Buzzards Bay was sufficient to maintain nitrogen limitation of primary productivity during the sum- mer.Ourfindingsillustratethatshallowsystemsdominatedby benthic producers have the potential to retain large terrestrial nitrogen loads when there is sufficient supply of phosphorus from exchange with coastal waters.

Chemometric approach for assessing the quality of olive cake pellets

This article investigates the influence of processing parameters (conditioning and binder content), on quality of fuel agro-pellets produced from four olive cultivars (Istarska Bjelica, Buža, Pendolino, Leccino) grown in experimental filed in Croatia (Istria). Physical and chemical properties of pellets have been determined to assess their quality. Low ash and sulphur levels were detected, with elevated nitrogen levels for all samples. Analysis of variance and post-hoc Tukey's HSD test at 95% confidence limit have been utilised to show significant differences between various samples. Low coefficients of variation have been obtained for each applied assay (0.09–2.98%), which confirmed the high accuracy of the measurements. Score analysis and principal component analysis have been used for assessing the effect of process variables and variety of cultivars on final quality of pellets. For PCA modelling, experimental data for physical and chemical properties have been used. Standard score analysis revealed that equally good physical and chemical characteristics of pellets can be obtained with conditioning at 50°C, but also without conditioning. The use of binders didn't affect the quality of pellets as much.

PEATBOG: a biogeochemical model for analyzing coupled carbon and nitrogen dynamics in northern peatlands

Abstract. Elevated nitrogen deposition and climate change alter the vegetation communities and carbon (C) and nitrogen (N) cycling in peatlands. To address this issue we developed a new process-oriented biogeochemical model (PEATBOG) for analyzing coupled carbon and nitrogen dynamics in northern peatlands. The model consists of four submodels, which simulate: (1) daily water table depth and depth profiles of soil moisture, temperature and oxygen levels; (2) competition among three plants functional types (PFTs), production and litter production of plants; (3) decomposition of peat; and (4) production, consumption, diffusion and export of dissolved C and N species in soil water. The model is novel in the integration of the C and N cycles, the explicit spatial resolution belowground, the consistent conceptualization of movement of water and solutes, the incorporation of stoichiometric controls on elemental fluxes and a consistent conceptualization of C and N reactivity in vegetation and soil organic matter. The model was evaluated for the Mer Bleue Bog, near Ottawa, Ontario, with regards to simulation of soil moisture and temperature and the most important processes in the C and N cycles. Model sensitivity was tested for nitrogen input, precipitation, and temperature, and the choices of the most uncertain parameters were justified. A simulation of nitrogen deposition over 40 yr demonstrates the advantages of the PEATBOG model in tracking biogeochemical effects and vegetation change in the ecosystem.

Aerosol species concentrations and source apportionment of ammonia at Rocky Mountain National Park

Changes in ecosystem function at Rocky Mountain National Park (RMNP) are occurring because of emissions of nitrogen and sulfate species along the Front Range of the Colorado Rocky Mountains, as well as sources farther east and west. The nitrogen compounds include both oxidized and reduced nitrogen. A year-long monitoring program of various oxidized and reduced nitrogen species was initiated to better understand their origins as well as the complex chemistry occurring during transport from source to receptor. Specifically, the goals of the study were to characterize the atmospheric concentrations of nitrogen species in gaseous, particulate, and aqueous phases (precipitation and clouds) along the east and west sides of the Continental Divide; identify the relative contributions to atmospheric nitrogen species in RMNP from within and outside of the state of Colorado; identify the relative contributions to atmospheric nitrogen species in RMNP from emission sources along the Colorado Front Range versus other areas within Colorado; and identify the relative contributions to atmospheric nitrogen species from mobile sources, agricultural activities, and large and small point sources within the state of Colorado. Measured ammonia concentrations are combined with modeled releases of conservative tracers from ammonia source regions around the United States to apportion ammonia to its respective sources, using receptor modeling tools. Implications: Increased deposition of nitrogen in RMNP has been demonstrated to contribute to a number of important ecosystem changes. The rate of deposition of nitrogen compounds in RMNP has crossed a crucial threshold called the “critical load.” This means that changes are occurring to park ecosystems and that these changes may soon reach a point where they are difficult or impossible to reverse. Several key issues need attention to develop an effective strategy for protecting park resources from adverse impacts of elevated nitrogen deposition. These include determining the importance of previously unquantified nitrogen inputs within the park and identification of important nitrogen sources and transport pathways.