Nitrogen Saturation Research Articles

Atmospheric dry deposition in the vicinity of the Salton Sea, California—I: Air pollution and deposition in a desert environment

Abstract Air pollutant concentrations and atmospheric dry deposition were monitored seasonally at the Salton Sea, southern California. Measurements of ozone (O3), nitric acid vapor (HNO3), ammonia (NH3), nitric oxide (NO), nitrogen dioxide (NO2) and sulfur dioxide (SO2) were performed using passive samplers. Deposition rates of NO3−, NH4+, Cl−, SO42−, Na+, K+ and Ca2+ to creosote bush branches and nylon filters as surrogate surfaces were determined for one-week long exposure periods. Maximum O3 values were recorded in spring with 24-h average values of 108.8 μg m−3. Concentrations of NO and NO2 were low and within ranges of the non-urban areas in California (0.4–5.6 and 3.3–16.2 μg m−3 ranges, respectively). Concentrations of HNO3 (2.0–6.7 μg m−3) and NH3 (6.4–15.7 μg m−3) were elevated and above the levels typical for remote locations in California. Deposition rates of Cl−, SO 4 2 – , Na+, K+ and Ca2+ were related to the influence of sea spray or to suspended soil particles, and no strong enrichments caused by ions originated by human activities were detected. Dry deposition rates of NO 3 – and NH 4 + were similar to values registered in areas where symptoms of nitrogen saturation and changes in species composition have been described. Deposition of nitrogenous compounds might be contributing to eutrophication processes at the Salton Sea.

Nitrogen Retention, Removal, and Saturation in Lotic Ecosystems

Increased nitrogen (N) loading to lotic ecosystems may cause fundamental changes in the ability of streams and rivers to retain or remove N due to the potential for N saturation. Lotic ecosystems will saturate with sustained increases in the N load, but it is unclear at what point saturation will occur. Rates of N transformation in lotic ecosystems will vary depending on the total N load and whether it is an acute or chronic N load. Nitrogen saturation may not occur with only pulsed or short-term increases in N. Overall, saturation of microbial uptake will occur prior to saturation of denitrification of N and denitrification will become saturated prior to nitrification, exacerbating increases in nitrate concentrations and in N export downstream. The rate of N export to downstream ecosystems will increase proportionally to the N load once saturation occurs. Long term data sets showed that smaller lotic ecosystems have a greater capacity to remove instream N loads, relative to larger systems. Thus, denitrification is likely to become less important as a N loss mechanism as the stream size increases. There is a great need for long-term studies of N additions in lotic ecosystems and clear distinctions need to be made between ecosystem responses to short-term or periodic increases in N loading and alterations in ecosystem functions due to chronic N loading.

Nitrogen saturation in UK moorlands: the critical role of bryophytes and lichens in determining retention of atmospheric N deposition

Summary Anthropogenic nitrogen (N) deposition may have several impacts on upland moorland ecosystems, including changes in vegetation composition, eutrophication and surface water acidification through nitrate leaching, but few studies linking N deposition to key biogeochemical processes have been published. A stable isotope tracer (15N) was used to determine the fate of inorganic N inputs to four moorland catchments across gradients of N deposition and leaching, through 2‐weekly additions to experimental plots on major soil types over 1 year. An apparent decline in total 15N recovery from soils and vegetation as the proportion of leached N deposition increased was not significant at the P = 0·05 level, but a significant relationship was found for recovery in mosses and lichens. Vegetation retained 31–68% of 15N inputs, and 15N recovery increased significantly (P = 0·01) with biomass for all compartments except woody shrubs. Mosses and lichens showed far greater 15N recovery per unit biomass than grasses or ericaceous shrubs. There was no significant variation in the proportion of 15N recovered in higher plants across the N deposition gradient (24–29%). In contrast, the proportion recovered in mosses and lichens declined from 44% to 2% as deposition increased, mirroring a decline in their biomass and showing a highly significant inverse relationship (P = 0·01) with nitrate leaching. The proportion of 15N recovered in litter plus surface soils (33–39%) was remarkably constant across the deposition gradient for a variety of soil types. However, significantly declining recovery per unit biomass in litter (P < 0·05) suggested progressive N saturation of this sink and increasing importance of retention in underlying surface soils as deposition increased. Synthesis and applications. Past studies have demonstrated a decline in mosses and lichens in response to increasing N deposition, but we show here for the first time that reduced N retention might result together with increased nitrate leaching into surface waters. The conservation of bryophyte and lichen flora on moorlands is therefore critical to prevent excessive nitrate leaching and associated surface water acidification and eutrophication. Ensuring management practices such as grazing or burning are at an intensity that does not further degrade the bryophyte and lichen communities may help minimize the impact of N deposition on freshwaters, but the only effective means to reduce the risk of N leaching is a reduction in N emissions.

The Long Lens of Forest History

The Long Lens of Forest History

Effects of a Cretaceous structural inversion and a postulated high heat flow event on petroleum system of the western Lower Saxony Basin and the charge history of the Apeldorn gas field

AbstractThermal history and evolution of the Palaeozoic petroleum system of the western Lower Saxony Basin as well as charge history of the Apeldorn gas field was reconstructed using 2-D forward basin modelling software. The Apeldorn gas field is located on an inverted western rim of the Lower Saxony Basin (LSB) and belongs with its relatively anomalous nitrogen content of 73.9 vol. % to one of the most unique gas accumulations in North Germany. Based on thermal calibration studies utilising both, vitrinite reflectance and corrected bottom hole temperatures as calibration parameters, a shallow burial model and an anomalous event of Coniacian high heat flow of 80 to 120 mW/m2was derived. As result, Lower Triassic and younger successions became subjected to slight changes in thermal maturity as opposed to Carboniferous and Permian successions, which show no assessable impact of the high heat flow event on the coalification pattern. The deep burial model in contrary to the shallow burial model is not supported by the structural reconstruction and backstripping in this more marginal setting. According to the modelling results, the key charge of the present Apeldorn gas field began in Tithonian (late Upper Jurassic) during the major phase of rifting in the Lower Saxony Basin. The present Westphalian coal-derived gas accumulations of the Lower Triassic Buntsandstein reservoir were sourced directly from modelled methane pools at top Rotliegend level. The hydrocarbon potential of the Westphalian source rocks became exhausted in Oxfordian (early Upper Jurassic). Reduction of the hydrostatic pressure during the Coniacian high heat flow event together with uplift during the Coniacian-Santonian inversion led to an extensive free gas exsolution. The resulting gas mixture between the exsolved free gas and the Westphalian coal-derived gas reached and saturated Buntsandstein reservoir. The structural trap became destroyed in course of the inversion leading to a sharp decrease of methane and nitrogen saturation.

Nitridation anisotropy in SiO2∕4H–SiC

Nitrogen incorporation at the SiO2∕SiC interface due to annealing in NO is measured and shown to be a strong function of crystal face. The annealing process involves two major solid-state chemical reactions: nitrogen uptake at the interface and N loss associated with second-order oxidation. An ad hoc kinetics model explains the experimental observations of anisotropy and nitrogen saturation.

Nitrogen input–output budgets for lake-containing watersheds in the Adirondack region of New York

The Adirondack region of New York is characterized by soils and surface waters that are sensitive to inputs of strong acids, receiving among the highest rates of atmospheric nitrogen (N) deposition in the United States. Atmospheric N deposition to Adirondack ecosystems may contribute to the acidification of soils through losses of exchangeable basic cations and the acidification of surface waters in part due to increased mobility of nitrate (NO3−). This response is particularly evident in watersheds that exhibit ‘nitrogen saturation.’ To evaluate the contribution of atmospheric N deposition to the N export and the capacity of lake-containing watersheds to remove, store, or release N, annual N input–output budgets were estimated for 52 lake-containing watersheds in the Adirondack region from 1998 to 2000. Wet N deposition was used as the N input and the lake N discharge loss was used as the N output based on modeled hydrology and measured monthly solute concentrations. Annual outputs were also estimated for dissolved organic carbon (DOC). Wet N deposition increased from the northeast to the southwest across the region. Lake N drainage losses, which exhibited a wider range of values than wet N deposition, did not show any distinctive spatial pattern, although there was some evidence of a relationship between wet N deposition and the lake N drainage loss. Wet N deposition was also related to the fraction of N removed or retained within the watersheds (i.e., the fraction of net N hydrologic flux relative to wet N deposition, calculated as [(wet N deposition minus lake N drainage loss)/wet N deposition]). In addition to wet N deposition, watershed attributes also had effects on the exports of NO3−, ammonium (NH4+), dissolved organic nitrogen (DON), and DOC, the DOC/DON export ratio, and the N flux removed or retained within the watersheds (i.e., net N hydrologic flux, calculated as [wet N deposition less lake N drainage loss]). Elevation was strongly related with the lake drainage losses of NO3−, NH4+, and DON, net NO3− hydrologic flux (i.e., NO3− deposition less NO3− drainage loss), and the fraction of net NO3− hydrologic flux, but not with the DOC drainage loss. Both DON and DOC drainage losses from the lakes increased with the proportion of watershed area occupied by wetlands, with a stronger relationship for DOC. The effects of wetlands and forest type on NO3− flux were evident for the estimated NO3− fluxes flowing from the watershed drainage area into the lakes, but were masked in the drainage losses flowing out of the lakes. The DOC/DON export ratios from the lake-containing watersheds were in general lower than those from forest floor leachates or streams in New England and were intermediate between the values of autochthonous and allochthonous dissolved organic matter (DOM) reported for various lakes. The DOC/DON ratios for seepage lakes were lower than those for drainage lakes. In-lake processes regulating N exports may include denitrification, planktonic depletion, degradation of DOM, and the contribution of autochthonous DOM and the influences of in-lake processes were also reflected in the relationships with hydraulic retention time. The N fluxes removed or stored within the lakes substantially varied among the lakes. Our analysis demonstrates that for these northern temperate lake-containing watershed ecosystems, many factors, including atmospheric N deposition, landscape features, hydrologic flowpaths, and retention in ponded waters, regulated the spatial patterns of net N hydrologic flux within the lake-containing watersheds and the loss of N solutes through drainage waters.

Protecting Resources on Federal Lands: Implications of Critical Loads for Atmospheric Deposition of Nitrogen and Sulfur

Critical loads are a potentially important tool for protecting ecosystems from atmospheric deposition and for promoting recovery. Exceeding critical loads for nitrogen and sulfur can cause ecosystem acidification, nitrogen saturation, and biotic community changes. Critical loads are widely used to set policy for resource protection in Europe and Canada, yet the United States has no similar national strategy. We believe that ecosystem science and resource protection policies are sufficiently advanced in the United States to establish critical loads for federal lands. Communication and interaction between federal area managers and scientists will ensure that critical loads are useful for assessing ecosystem conditions, influencing land management decisions, and informing the public about the status of natural resources. Critical loads may also be used to inform air pollution policy in the United States, regardless of whether critical loads are directly linked to air quality regulations and emissions reductions agreements, as they are in Europe.

Köpek ve kedilerin periton diyalizinde diyalizatın drenaj oranlarının ve üre, kreatinin doygunluklarının değerlendirilmesi

Bu çalışmada çift taraflı tam üreter tıkanmalı köpek ve kedilerde uygulanan periton diyalizinde, abdominal boşluktan drene edilen diyalizatın geri alınabilme yüzdeleri, diyalizat ve kandaki üre-nitrojen ve kreatinin miktarları ve diyalizattaki ürenitrojen ve kreatinin kana göre doygunlukları değerlendirildi. Diyaliz, %1.5 dextroz içeren diyalizat 40ml/kg dozda, 60 dakika süren seanslar halinde ve 6 saat ara ile 8 seans uygulandı. Verilen diyalizatın geri alınabilme yüzdesi köpeklerde %77.3-81 ve kedilerde %73.6-87.9 arasında oldu. Diyalizatın geri alınabilme yüzdesi, üre-azotu ve kreatinin değerleri seanslar ilerledikçe artış gösterdi. Bu yükselme istatistik olarak kedilerde önemli olurken (p

CHARACTERISTIC OF NITROGEN OUTFLOW FROM MOUNTAIN AREA IN THE NORTHWEST OF KANTO PLAIN

The runoff characteristics of NO3-N in forested mountain areas located in the northwest of Kanto Plainis investigated by field observation from 2001. The observation consists of two components, one is NO3-N concentration in mountain stream water and the other is vertical profile of NO3-N concentration in soil water. It is clarified that the large difference of NO3-N concentration in mountain stream water exists between the west side and the east side of Tone River. Though NO3-N concentration in soil water shows the almost similar tendency, vertical profile shows three types that do not exactly correspond to the areal distribution of concentration. By the correlation analysis, there is positive correlation between rainfall events and increase of NO3-N concentration in mountain stream water in the east side of Tone River, where the concentration is low. On the contrary, no correlation is found out in the west side of Tone River, where the concentration is high. These phenomena correspond to the nitrogen saturation.

Water chemistry of high elevation Colorado wilderness lakes

High elevation alpine and subalpine Rocky Mountain lakes in Colorado and southeastern Wyoming were examined to determine regional variability in water chemistry and their sensitivity to atmospheric deposition. Acid neutralizing capacity, pH, conductivity and concentrations of major anions and cations were compared. Regional differences in water chemistry are evident. The south-eastern most lakes have significantly higher pH, conductivity, ANC, and sums of acid and base concentrations than lakes in the other regions of the state. In contrast the north-western most lakes are significantly more dilute than those from other regions. Despite these two regional differences, most regions are similar in having a wide range of variability in potential sensitivity of their lakes to acidification and nitrogen export. Many wilderness areas in western and eastern regions contains lakes that are extremely sensitive and other lakes not susceptible to deposition. Overall, 70% of the Colorado lakes are sensitive to acidification and 15% are extremely sensitive to acidification. All of the regions had lakes that are classified as susceptible or sensitive to acidification, with 12 of the 17 areas having all of their sampled lakes susceptible or sensitive. Generally NO concentration in surface waters decreased from mid-season to late season; yet a large number of the lakes export NO late in the season, suggesting nitrogen saturation. The results confirm the sensitivity of high elevation wilderness aquatic ecosystems in all regions of Colorado to acidification and nitrogen deposition.

Kudzu (Pueraria montana): History, Physiology, and Ecology Combine to Make a Major Ecosystem Threat

Kudzu, Pueraria montana (Lour.) Merr. variety lobata (Willd.) was introduced into the United States at the 1876 Centennial Exposition in Philadelphia, PA. Subsequently, it was planted widely to reduce soil erosion by the Soil Erosion Service and Civilian Conservation Corp. Over 85 million seedlings of kudzu were provided to landowners by government agencies in the southeast in the first half of the 20th century. In 1953, kudzu was removed from the list of approved plants for erosion control, in 1970 it was officially labeled a weed, and in 1997 it was placed on the Federal Obnoxious Weed List. Its rapid elongation rates, high leaf area indices, high photosynthetic rates, and frequent rooting at stem nodes make kudzu an aggressive competitor with native shrubs and trees. Estimates are that kudzu currently covers 3 million hectares throughout the eastern United States and is spreading by 50,000 ha per year. Despite widespread anecdotal statements, little quantitative information is available regarding the ecological effects of kudzu. The ability of kudzu to overtop and shade forest trees, fix atmospheric nitrogen, and emit isoprene suggest that it may have substantial effects on native forest biodiversity, forest nitrogen cycles, watershed nitrogen saturation, freshwater eutrophication, and regional air quality. Kudzu's growth rate increases strongly in response to increased CO2, and without the constraint of allocation to woody tissue this response may increase the competitive dominance of kudzu as atmospheric levels of CO2 increase. This fact, combined with its sensitivity to cold temperatures, implies that kudzu may increase its range in future warmer, high-CO2 environments. The lack of quantitative investigations on the ecological effects of kudzu is a severe impediment to our understanding of its current and future effects on native plant and animal communities and forest ecosystems.

HISTORY AND PROSPECT OF CATCHMENT BIOGEOCHEMISTRY: A EUROPEAN PERSPECTIVE BASED ON ACID RAIN

Hydrochemical monitoring of catchments provided a philosophical framework as well as hard data to understand and quantify the linked biological and abiotic processes that explain how atmospheric deposition of S and N changed soils and waters in nonagricultural areas across Europe. Initially, as a tool to collect relevant data in a representative and systematic way, hydrochemical monitoring provided evidence for widespread surface water acidification related to atmospheric pollution and long-range air transport. Recognizing the strong effect biota can have on their chemical environment, in the context of catchment biogeochemistry, these data provided new insights into individual processes of soil and water acidification and helped to quantify the relative importance of natural and anthropogenic sources of H+. Furthermore, combined with large-scale ecosystem manipulation and modeling, catchment biogeochemistry offered an effective tool to investigate risks of acidification and of nitrogen saturation of soil...

Nutrient Seepage from Operating Turkey Buildings with a Litter System

Core soil samples were collected from nine operating turkey buildings with different ages located in areas of different soil types in Minnesota. These samples were analyzed for pH, phosphorus, organic matter, ammonium nitrogen, and nitrate nitrogen to investigate the potential of groundwater pollution by turkey operations. According to the data, for clay loam soil, the chance of leaching of phosphorus to groundwater is slight if the water table is 153 cm below the ground surface. Saturation of ammonium nitrogen in the topsoil can be reached in 20 yr of continuous operation. Therefore, it may be suggested that the topsoil layer in turkey buildings be replaced every 20 yr for areas of high groundwater (within 91 cm or so), and every 40 yr for areas with low groundwater (greater than 153 cm in depth). Also for clay loam soil, the nitrate nitrogen may be able to move down in soil about 91 cm deep in ten years. For barns older than ten years, it is observed that the nitrate nitrogen concentrations are significantly higher inside than outside of barns throughout the entire sampling depth. As a preventive option for turkey producers for nitrate nitrogen in particular, replacing the topsoil layer every ten years may be helpful to obviate the potential pollution of groundwater resource by nitrate leaching. Similar measures may also be applied to loam soil. Due to limited data, the performance of silt and sandy loam soils in preventing nutrient leaching cannot be determined and should receive further research.

Soil emissions of nitric oxide in two forest watersheds subjected to elevated N inputs

The production of nitric oxide (NO) in forest soils can indicate that the ecosystem is progressing toward a state of nitrogen (N) saturation. Soil NO emissions may also have impacts on local tropospheric ozone (O 3) levels. During 2000–2001, we made first-time measurements of NO emissions in two paired watershed studies. In each study, one watershed had been amended with aerial applications of 2.5–3.5 g N m −2 per year above background atmospheric deposition rates since 1989, and an adjacent watershed served as a reference. In plots at the Fernow Experimental Forest (FEF) in West Virginia and the Bear Brook Watershed in Maine (BBWM), NO emissions in N-amended watersheds (0.61–6.8 μg NO-N m −2 h −1) were higher than in the reference watersheds (0.21–1.4 μg NO-N m −2 h −1). In the N-amended watershed at BBWM, NO fluxes in plots dominated by hardwood species were higher than in plots dominated by softwood species, in contrast to previous studies in other forests. Field NO fluxes were correlated with mineral soil nitrate (NO 3 −) concentrations ( r 2=0.65, P=0.016) across all plots, suggesting that NO emissions may be a reliable indicator of NO 3 − leaching potential. Laboratory experiments indicated that nitrification was the dominant source of NO at both sites. At BBWM, increased NO emissions in N-amended soil appeared to result from more rapid nitrification. In contrast, reduced soil pH in N-amended soil at FEF may have caused increased protonation of nitrification-derived nitrite, and the subsequent abiotic formation of NO, even though nitrification rates were not significantly higher than in unamended soil. The results suggest that enhanced soil NO emissions are a characteristic response in forests subjected to elevated N inputs. One possible consequence of higher NO emissions is an increase in O 3-related phytotoxicity. This effect may mitigate the ability of forests to accumulate carbon in response to N inputs or increasing atmospheric CO 2.

Gross nitrogen process rates in temperate forest soils exhibiting symptoms of nitrogen saturation

In order to examine how fundamental soil N cycling processes are affected by elevated N inputs to temperate forest ecosystems, we made concurrent laboratory measurements of gross rates of nitrogen (N) mineralization, nitrification, nitrate (NO 3 −) consumption, ammonium (NH 4 +) immobilization, nitrous oxide (N 2O) and nitric oxide (NO) production, and NO consumption in soils from the Harvard Forest Chronic N Amendment Study. Gross nitrification rates varied with N addition rate in a manner that was entirely consistent with patterns of NO 3 − leaching and NO emissions that have been previously observed in field studies. Gross nitrification was elevated above controls in soils from a pine stand receiving 5 and 15 g N m −2 per year, and in soils from a hardwood stand receiving 15 g N m −2 per year. Gross nitrification tended to increase with decreasing soil pH, suggesting that acid-tolerant nitrifying bacteria predominate in these soils. Different patterns of inorganic N consumption in the two stands may provide some clues to understanding the more rapid onset of N saturation that has been historically observed in the pine stand. Absolute rates of NH 4 + immobilization, and rates of NO 3 − consumption per unit of available NO 3 −, each tended to decrease with increasing N addition in the hardwood stand, but did not vary significantly in the pine stand. Gross NO production rates increased in a manner that was consistent with nitrification rate increases, and represented up to 19% of gross nitrification. Production of N 2O was generally ≤15% of NO production and <1% of gross nitrification. Consumption of NO represented ≥96% of gross NO production and may have contributed up to 25% of total NO 3 − production.

Climate effects on stream nitrate concentrations at 16 forested catchments in south central Ontario.

Increased nitrate (NO3) concentrations in streamwaters draining forested catchments are reportedly an early indicator of nitrogen (N) saturation. Nitrate concentrations in streams draining 16 forested catchments in south central Ontario were monitored over a 16-year period, during which time N bulk deposition was relatively constant (approximately 9 kg ha(-1) yr(-1)). Mean annual NO3 concentrations in streams were both highly variable among catchments and among years, although patterns of annual concentration were similar among many catchments. Coherence analysis identified two stream groupings. Shallow soils, moderate slopes, low NO3 concentration, and a large wetland component characterized the first group. The second group had primarily upland characteristics including deeper soils, steeper slopes, higher NO3 concentrations, and a much smaller wetland component. Patterns in NO3 concentration in wetland-influenced streams appeared to be related to summer drought and cumulative frost depth, whereas NO3 concentrations in upland-draining streams appeared to be related to both mean annual air temperature and summer drought. Because a number of different climate parameters as well as the physical character of the catchments apparently influence NO3 export, NO3 concentrations in streams are not a good indicator of N saturation in this region.

Effects of Silvicultural Practices on Soil Carbon and Nitrogen in a Nitrogen Saturated Central Appalachian (USA) Hardwood Forest Ecosystem

Silvicultural treatments represent disturbances to forest ecosystems often resulting in transient increases in net nitrification and leaching of nitrate and base cations from the soil. Response of soil carbon (C) is more complex, decreasing from enhanced soil respiration and increasing from enhanced postharvest inputs of detritus. Because nitrogen (N) saturation can have similar effects on cation mobility, timber harvesting in N-saturated forests may contribute to a decline in both soil C and base cation fertility, decreasing tree growth. Although studies have addressed effects of either forest harvesting or N saturation separately, few data exist on their combined effects. Our study examined the responses of soil C and N to several commercially used silvicultural treatments within the Fernow Experimental Forest, West Virginia, USA, a site with N-saturated soils. Soil analyses included soil organic matter (SOM), C, N, C/N ratios, pH, and net nitrification. We hypothesized the following gradient of disturbance intensity among silvicultural practices (from most to least intense): even-age with intensive harvesting (EA-I), even-age with extensive harvesting, even-age with commercial harvesting, diameter limit, and single-tree harvesting (ST). We anticipated that effects on soil C and N would be greatest for EA-I and least with ST. Tree species exhibited a response to the gradient of disturbance intensity, with early successional species more predominant in high-intensity treatments and late successional species more predominant in low-intensity treatments. Results for soil variables, however, generally did not support our predictions, with few significant differences among treatments and between treatments and their paired controls for any of the measured soil variables. Multiple regression indicated that the best predictors for net nitrification among samples were SOM (positive relationship) and pH (negative relationship). This finding confirms the challenge of sustainable management of N-saturated forests.

Input-Output Budgets of Inorganic Nitrogen for 24 Forest Watersheds in the Northeastern United States: A Review

Input-output budgets for dissolved inorganic nitrogen (DIN) are summarized for 24 small watersheds at 15 locations in the northeastern United States. The study watersheds are completely forested, free of recent physical disturbances, and span a geographical region bounded by West Virginia on the south and west, and Maine on the north and east. Total N budgets are not presented; however, fluxes of inorganic N in precipitation and streamwater dominate inputs and outputs of N at these watersheds. The range in inputs of DIN in wet-only precipitation from nearby National Atmospheric Deposition Program (NADP) sites was 2.7 to 8.1 kg N ha −1 yr −1 (mean = 6.4 kg N ha −1 yr −1 ;m edian =7 .0 kg Nh a −1 yr −1 ). Outputs of DIN in streamwater ranged from 0.1 to 5.7 kg Nh a −1 yr −1 (mean = 2.0 kg N ha −1 yr −1 ;m edian =1 .7 kg Nh a −1 yr −1 ). Precipitation inputs of DIN exceeded outputs in streamwater at all watersheds, with net retention of DIN ranging from 1.2 to 7.3 kg N ha −1 yr −1 (mean = 4.4 kg N ha −1 yr −1 ;m edian =4 .6 kg Nh a −1 yr −1 ). Outputs of DIN in streamwater were predominantly NO3-N (mean = 89%; median = 94%). Wet deposition of DIN was not significantly related to DIN outputs in streamwater for these watersheds. Watershed characteristics such as hydrology, vegetation type, and land-use history affect DIN losses and may mask any relationship between inputs and outputs. Consequently, these factors need to be included in the development of indices and simulation models for predicting 'nitrogen saturation' and other ecological processes.

Ion Nitriding of Coatings Deposited from a Liquid-Metal Carrier

Laws of nitrogen saturation (in glow discharge) of stainless steel 08Kh18N10T with coating preliminarily deposited from a liquid-metal carrier are studied. Nitriding regimes are suggested. The structure and properties of the obtained titanium-nitrogen coatings are described.