Development of Stream Water Chemistry during Spring Melt in a Northern Hardwood Forest

The role of snowmelt and subsurface hydrology in determiningthe chemistry of a small headwater stream in the TurkeyLakes Watershed (TLW) was evaluated for the spring meltperiods 1992 to 1996. Spring runoff is the dominanthydrological event at the TLW each year. Processesoccurring within the snowpack during snowmelt wereprincipally responsible for the above-ground changes inchemical fluxes relative to bulk deposition (the effect ofwinter throughfall was minimal). Large changes in chemicalfluxes occurred below ground. Organic matter decomposition,weathering, nitrification, and element cycling are some ofthe more important below-ground processes that operateduring the snow accumulation and ablation season and controlthe composition of the water ultimately appearing in thestream. Maximum stream discharge was accompanied byelevated concentrations of H⁺, NO₃ ^-, K⁺,NH₄ ⁺, DOC, Al and Mn, but reduced levels ofCa²⁺, Mg²⁺, SO₄ ^2- and SiO₂. Theconcentration-discharge relationships were consistent withwater movement through and above the forest floor duringpeak discharge, a flowpath facilitated by rapid infiltrationof meltwater and the existence of a relatively impermeablelayer in the mineral soil creating a perched water table. Averaged over the five periods of snow accumulation andablation, it was estimated that pre-melt stream flow, andwater routed through the forest floor and through the uppermineral soil contributed 9, 28 and 63%, respectively, ofthe discharge measured at the outlet of the catchment. Theforest floor contribution would be greater at peak dischargeand at higher elevations. An end-member mixing modelestimated concentrations of SO₄ ^2-, NO₃ ^-,Cl^-, Ca²⁺, Mg²⁺, Na⁺ and Al that werecomparable to average values measured in the stream. Othervariables (NH₄ ⁺, H⁺, K⁺ and DOC) wereover-estimated implying retention mechanisms operatingoutside the model assumptions.     

Isotopic Assessment of Sources of Surface Water Nitrate within the Oldman River Basin, Southern Alberta, Canada

Concentrations and isotopic compositions of NO₃ ^- from the Oldman River (OMR) and some of its tributaries (Alberta, Canada) have been determined on a monthly basis since December 2000 to assess temporal and spatial variations of riverine NO₃ ^- sources within the OMR basin. For the OMR sites, NO₃ ^--N concentrations reached up to 0.34 mg L^-1, δ¹⁵N-NO₃ ^- values varied between –0.3 and +13.8‰, and δ¹⁸O-NO₃ ^- values ranged from –10.0 to +5.7‰. For the tributary sites, NO₃ ^--N concentrations were as high as 8.81 mg L^-1, δ¹⁵N-NO₃ ^- values varied between –2.5 and +23.4‰, and δ¹⁸O-NO₃ ^- values ranged from –15.2 to +3.4‰. Tributaries in the western, relatively pristine forested part of the watershed add predominantlyNO₃ ^- to the OMR with δ¹⁵N-NO₃ ^- values near +2‰ indicative of soil nitrification. In contrast, tributariesin the eastern agriculturally-urban-industrially-used part of the basin contribute NO₃ ^- with δ¹⁵N-NO₃ ^- valuesof about +16‰ indicative of manure and/or sewage derived NO₃ ^-. This difference in δ¹⁵N-NO₃ ^- values of tributaries was found to be independent of the season, but rather indicates a spatial change in the NO₃ ^- source, which correlates with land use changes within the OMR basin. As a consequence of tributary influx, δ¹⁵N-NO₃ ^- values in the Oldman River increased from <+3‰ to >+6‰ in the downstream direction (W to E), although [NO₃ ^--N] increased only moderately (generally <0.5 mg L^-1). This study demonstrates the usefulness of δ¹⁵N-NO₃ ^- and δ¹⁸O-NO₃ ^- values in identifying the addition of anthropogenic NO₃ ^- to riverine systems.     

Topographic Controls of Nitrogen,Sulfur, and Carbon Transport from a Tolerant Hardwood Hillslope

The lateral down-slope movement of water, NO₃ ^-, NH₄ ⁺, SO₄ ^2-, H⁺ and DOC through an ablation till was examined from 1987 to 1990 for a one hectaresoil catena on a steep hillslope with uniform forest cover at the Turkey Lakes Watershed (TLW), Ontario, Canada. Natural variation in the export of nutrients from the soil profile via soil water to Little Turkey Lake was assessed in relation to nutrient distribution in soil at different topographic positions.Subsurface throughflow exhibited dramatic differences in nutrientconcentrations and fluxes with slope position, largely reflectingthat of the soil horizons through which the water passed. GreaterNO₃ ^-, SO₄ ^2-, and DOC concentrations in subsurface water in the upper, well-drained hillslope were a reflection of enrichment by contact with more acidic, more developed podzols, and more favorable soil physical and biological conditions for NO₃ ^- retention in solution.Nutrient inputs to the lake were strongly influenced by increaseddown-slope transport of water, and increased SO₄ ^2-, N, and C retention in wetter, less-developed podzolic soils that characterize lower slope positions. An understanding of water movement and soil development variation withtopographic position was required to accurately estimate nutrient budgets for steep slopes at TLW.     

Integrated Nitrogen Modeling in a Boreal Forestry Dominated River Basin: N Fluxes and Retention in Lakes and Peatlands

Two models, N_EXRET and INCA, were applied to the Simojoki river basin (3160 km²) in northern Finland in order to assess nitrogen retention in wetlands and lakes. N_EXRET is a spatial, export coefficient-based N export and retention model developed for large river basins. It utilizes remote sensing-based land use and forest classification, evaluated export coefficients, and data on areal N deposition and point sources of N. A new version (v1.7) of the Integrated Nitrogen in CAtchments model (INCA) is a semi-distributed, dynamic nitrogen process model, which simulates and predicts nitrogen transport and processes within catchments. Average retention of the gross total N load of 700 t a^-1 to the river system was estimated using N_EXRET model as 17 t N a^-1 to the wetlands and 77 t N a^-1 to the lakes. A good fit was found between modeled and measured values along the river. Inorganic N fluxes simulated by the INCA model were compared with measured fluxes along the river Simojoki, with a good fit between modeled and measured NH₄ ⁺-N fluxes, and an adequate fit for NO₃ ^--N fluxes. Both fluxes were overestimated at the first reach, below Lake Simojärvi. High percentage of peatlands led to high NH₄ ⁺-N/NO₃ ^--N ratios derived from data, indicating negligible nitrification in large river subbasins and particularly in small research catchments.     

Nitrogen Turnover and Nitrate Leaching after Bark Beetle Attack in Mountainous Spruce Stands of the Bavarian Forest National Park

More than 85% of the mountainous spruce forest of the Bavarian Forest National Park died after bark beetle attack during the last decade. The elemental budget of intact stands and of different stages after the dieback was investigated. N-fluxes in throughfall of intact stands were lower (12–16 kg ha^-1 a^-1) than in an earlier study in an intact mountainous spruce stand in the Bavarian Forest National Park and were reduced in the first years after the dieback (3–5 kg N ha^-1 a^-1). Nitrate-N fluxes by seepage water of intact stands at 40 cm depth, which is below the main rooting zone, were moderate (5–9 kg ha^-1 a^-1). After the dieback of the stands, NH₄ ⁺ concentrations were increased in humus efflux as were NO₃ ^- concentrations in mineral soil. Due to the relatively high precipitation, dilution of the elemental concentrations in seepage was considerable.Therefore, NO₃ ^- concentrations were usually below the level of drinking water (806 μmol NO₃ ^- L^-1), with lowest concentrations after the snowmelt and highest in autumn. Nitrate concentrations were elevated from the first year until the 7th year after the dieback. Total NO₃ ^--N losses by seepage until the 7th year after the dieback equalled 543 kg N ha^-1. Aluminium fluxesafter the dieback were enhanced in the mineral soil from 55 to 503 mmol_c m^-2 a^-1 (average of 8 yr), K⁺ fluxes from 8 to 37 mmol_c m^-2 a^-1, and Mg²⁺ fluxes from 13 to 35 mmol_c m^-2 a^-1. The consequences for the nutritional status of the ecosystem, the hydrosphere, and forest management are discussed in the paper.     

Nitrate Leaching From a Mountain Forest Ecosystem with Gleysols Subjected to Experimentally Increased N Deposition

Nitrate leaching was measured over seven years of nitrogen (N) addition in a paired-catchment experiment in Alptal, central Switzerland (altitude: 1200 m, bulk N deposition: 12 kg ha^-1 a^-1). Two forested catchments (1500 m² each) dominated by Picea abies) were delimited by trenches in the Gleysols. NH₄NO₃ was added to one of the catchments using sprinklers. During the first year, the N addition was labelled with ¹⁵N. Additionally, soil N transformationswere studied in replicated plots. Pre-treatment NO₃ ^--N leaching was 4 kg ha^-1 a^-1 from both catchments, and remained between 2.5 and 4.8 kg ha^-1 a^-1 in the control catchment. The first year of treatment induced an additional leaching of 3.1 kg ha^-1, almost 90% of which was labelled with ¹⁵N, indicating that it did not cycle through the large N pools of the ecosystem (soil organic matter and plants). These losses partly correspond to NO₃ ^- from precipitation bypassing the soil due to preferential flow. During rain or snowmelt events, NO₃ ^- concentration peaks as the water table is rising, indicating flushing from the soil. Nitrification occurs temporarily along the water flow paths in the soil and can be the source of NO₃ ^- flushing. Its isotopic signature however, shows that this release mainly affects recently applied N, stored only between runoff events or up to a few weeks. At first, the ecosystem retained 90% of the added N (2/3 in the soil), but NO₃ ^- losses increased from 10 to 30% within 7 yr, indicating that the ecosystem became progressively N saturated.     

Study of Bulk and Sub-Event Wet Deposition in Gebze,Turkey

This study presents the chemical composition of bulk deposition during the period of February 1996–May 1997 and the chemical composition of sub-event wet deposition on 13 August 1997 in Gebze. Samples were analyzed for SO₄ ^2-, NO₃ ^-, Cl^-,Ca²⁺, Mg²⁺, K⁺, Na⁺, and NH₄ ⁺ in addition to pH. The source of some ionic components in the bulk deposition such as K⁺ and Ca²⁺ were found to be the terrestrial regions, as expected. The (non-sea Cl^-)/Cl^- ratio of 0.05 suggests that the very large portion of Cl^- in the bulkdeposition was of marine origin. The ratio of (non-sea SO₄ ^2-)/SO₄ ^2- varied between 0.86 and 0.99,indicating that the main source of sulfate was not the sea. It is found that the sulfate and calcium concentrations were highest in summer and lowest in fall. The analysis of bulk deposition also indicated that nearly 24% of the events were acidic (pH < 5.6). During sub-event wet deposition collectedon the same site pH decreased continually, and during the passageof cold front concentrations of Cl^-, SO₄ ^2- and NO₃ ^- increased.     

Integrated Nitrogen and Flow Modelling (INCA) in a Boreal River Basin Dominated by Forestry: Scenarios of Environmental Change

A new version (v1.7) of the Integrated Nitrogen in CAtchments model(INCA) was applied to the northern boreal Simojoki river basin (3160 km²) in Finland. The INCA model is a semi-distributed, dynamic nitrogen (N) process model which simulates N transport and processes in catchments. The INCA model was applied to model flow and seasonal inorganic N dynamics of the river Simojoki basin over the period 1994–1996, and validated for two more years. Both calibration and validation of the model were successful. The model was able to simulate annual dynamics of inorganic N concentrations in the river. The effects of forest management and atmospheric deposition on inorganic N fluxes to the sea in 2010 were studied. Three scenarios were applied for forestry practices and two for deposition. The effects of forest cutting scenarios and atmospheric deposition scenarios on inorganic N flux to the sea were small. The combination of the maximum technically possible reduction of N deposition and a decrease of 100% in forest cutting and peat mining areas decreased NO₃ ^--N flux by 6.0% and NH₄ ⁺-N flux by 3.1%.     

The influence of atmospheric n deposition on nitrous oxide and nitric oxide fluxes and soil ammonium and nitrate concentrations

The deposition of atmospheric N to soils provides sources of available N to the nitrifying and denitrifying microbial community and subsequently influences the rate of NO and N₂O emissions from soil. We have investigated the influence of three different sources of enhanced N deposition on NO and N₂O emissions 1) elevated NH₃ deposition to woodlands downwind of poultry and pig farms, 2) increased wet cloud and occult N deposition to upland forest and moorland and 3) enhanced N deposition to trees as NO^? ₃ and NH⁺ ₄ aerosol. Flux measurements of NO and N₂O were made using static chambers in the field or intact and repacked soil cores in the laboratory and determination of N₂O by gas chromatography and of NO by chemiluminescence analysis. Rates of N deposition to our study sites were derived from modelled estimates of N deposition, NH₃ concentrations measured by passive diffusion and inference from measurements of the ²¹⁰Pb inventory of soils under tree canopies compared with open grassland. NO and N₂O emissions and KCl-extractable soil NH⁺ ₄ and NO^? ₃ concentrations all increased with increasing N deposition rate. The extent of increase did not appear to be influenced by the chemical form of the N deposited. Systems dominated by dry-deposited NH₃ downwind of intensive livestock farms or wet-deposited NH⁺ ₄and NO^? ₃ in the upland regions of Britain resulted in approximately the same linear response. Emissions of NO and N₂O from these soils increased with both N deposition and KCl extractable NH⁺ ₄, but the relationship between NH⁺ ₄ and N deposition (ln NH⁺ ₄ = 0.62 ln N_deposition+0.21, r ² = 0.33, n = 43) was more robust than the relationship between N deposition and soil NO and N₂O fluxes.     

Nitrous Oxide in Agricultural Drainage Waters Following Field Fertilisation

Dissolved nitrous oxide (N₂O), nitrate (NO₃ ^-), and ammonium (NH₄ ⁺) concentrations in an agricultural field drain were intensively measured over the period of field nitrogen (N) fertilisation and for several weeks thereafter. Supersaturations of dissolved N₂O were observed in field drain waters throughout the study. On entry to an open drainage ditch, concentrations of dissolved N₂O rapidly decreased and a total N₂O-N emission via this pathway of 13.2 g over the period of study (45 days) was calculated. This compared with a predicted emission of the order of 300 g, based on measured losses of NO₃ ^- and NH₄ ⁺ in the field drainage water, and the default IPCC emission factor of 0.01 kg N₂O-N per kg Nentering rivers and estuaries. In contrast to widespread evidence of a clear relationship between the amount of N applied to agricultural land and subsequent direct N₂O emission from the soil surface, the relationship between the amount of N₂O in soil drainage waters and the amount of N applied was poor. We conclude that the complexity, both spatially and temporally, of the processes ultimately responsible for the amount of N₂O in agricultural drainage waters make a straightforward relationship between N₂O concentration and N application rate unlikely in all but the simplest of systems.     

Simulation of Nitrogen Dynamics and Fluxes in Contrasting Catchments in Norway by Applying the Integrated Nitrogen Model for Catchments (INCA)

The process-based INCA model was applied to Dalelva Brook (3.2 km²) and the Bjerkreim River (685 km²) including several subcatchments, in order to test the model's ability to simulate streamwater nitrate (NO₃ ^-) dynamics and output fluxes under highly contrasting climatic conditions and nitrogen (N) loading. The simulated runoff volumes and mean NO₃ ^- concentrations at Dalelva and Bjerkreimwere within +2 to +10% of the measured average during 1993–1995 (–19 to +31% within individual years). INCA to a great extent also reproduced the observed streamwater flow dynamics at both study sites (coefficient of determination, r ² > 0.70). Temporal variation of streamwater NO₃ ^- during 1993–1995 was captured quite well by the model, especially at small catchments with a distinct seasonal NO₃ ^- pattern (r ² = 0.46–0.68). At the Bjerkreim River outlet, the relationship were somewhat weaker (r ² = 0.26, p < 0.01). Despite a few situations where the model failed to capturethe streamwater NO₃ ^- dynamics, INCA proved to be a quite robust tool for simulating NO₃ ^- dynamics and output fluxes in the two study catchments.     

Hysteresis in Reversal of Central European Mountain Lakes from Atmospheric Acidification

Extremely high emissions of S and N compounds in Central Europe (both 280 mmol m^-2 yr^-1) declined by 70and 35%, respectively, during the last decade. Decreaseddeposition rates of SO₄ ^-2, NO₃ ^-, and NH₄ ⁺ in the region paralleled emission declines. The reduction in atmospheric inputs of S and N to mountain ecosystemshas resulted in a pronounced reversal of acidification in the Tatra Mountains and Bohemian Forest lakes. Between the 1987–1990and 1997–1999 periods, concentrations of SO₄ ^-2 and NO₃ ^- decreased (average ± standard deviation) by 22±7 and 12±7 mol L^-1, respectively, in theTatra Mountains, and by 19±7 and 15±10 mol L^-1, respectively, in the Bohemian Forest. Their decrease was compensated in part (1) by a decrease in Ca²⁺ + Mg²⁺ (17±7 mol L^-1) and H⁺ (4±6 mol L^-1), and an increase in HCO₃ ^-(10±10 mol L^-1) in the Tatra Mountains lakes, and (2) by a decrease in Al (7±4 mol L^-1), Ca²⁺ + Mg²⁺ (9±6 mol L^-1), and H⁺ (6±5 mol L^-1), in Bohemian Forest lakes. Despite the rapid decline in lake water concentrations of SO₄ ^-2 and NO₃ ^- in response to reduced S and N emissions, their present concentrations in some lakes are higher than predictionsbased on observed concentrations at comparable emission rates during development of acidification. This hysteresis in chemical reversal from acidification has delayed biological recovery of the lakes. The only unequivocal sign of biological recovery hasbeen observed in erné Lake (Bohemian Forest) where a cladoceran species Ceriodaphnia quadrangular has recentlyreached its pre-acidification abundance.     

Trends in Water Chemistry in a Maple Forest on a Steep Slope

Year-to-year variation in SO₄ ^2-,NO₃ ^-, Ca²⁺, K⁺, and Mg²⁺concentrations in forest floor and mineral soil percolatefrom a forested, podzolic soil at the Turkey Lakes Watershedon the Precambrian Shield was assessed for monotonic trendsbetween 1986 and 1995. Our objective was to examine howrapidly ion concentrations in soil percolate equilibratedafter stabilization of SO₄ ^2- concentrations inprecipitation. Significant negative trends were detected inmonthly Ca²⁺, and Mg²⁺ concentrations in forestfloor and SO₄ ^2-, Ca²⁺, and Mg²⁺ inmineral soil percolate during the 10-year-period. Thedecline in Ca²⁺ and Mg²⁺ was greater than annualdecreases in SO₄ ^2- and NO₃ ^- in forestfloor percolate and proportional to the reduction inSO₄ ^2- in mineral soil percolate. Response ofmineral soil percolate to a 15 mol_c L^-1SO₄ ^2- decrease in wet-only precipitation between1985 and 1986 was a gradual decline in SO₄ ^2-concentration through 1995. The five-year meanSO₄ ^2- concentration in bulk precipitation, forestfloor percolate, and mineral soil percolate decreased 8, 9and 18 mol_c L^-1 from 1986–90 to 1991–95.Microbial (mineralization of organic S) and sorption(release from and/or retention in the pool of insolubleSO₄ ^2-) processes in the soil were logicalexplanations for the observed changes in SO₄ ^2- inmineral soil percolate.     

Acidification Trends and the Evolution of Neutralization Mechanisms through Time at the Bear Brook Watershed in Maine (BBWM), U.S.A.

The paired catchment study at the forested Bear Brook Watershed in Maine (BBWM) U.S.A. documents interactions among short- to long-term processes of acidification. In 1987–1989, runoff from the two catchments was nearly identical in quality and quantity. Ammonium sulfate has been added bi-monthly since 1989 to the West Bear catchment at 1800 eq ha^-1 a^-1; the East Bear reference catchment is responding to ambient conditions. Initially, the two catchments had nearly identical chemistry (e.g., Ca²⁺, Mg²⁺, SO₄ ^2-, and alkalinity ≈82, 32, 100, and 5 μeq L^-1, respectively). The manipulated catchment responded initially with increased export of base cations, lower pH and alkalinity, and increased dissolved Al,NO₃ ^- and SO₄ ^2-. Dissolved organic carbon and Si have remained relatively constant. After 7 yr of treatment, the chemical response of runoff switched to declining base cations, with the other analytes continuing their trends; the exports of dissolved and particulate Al, Fe, and P increased substantially as base cations declined. The reference catchment has slowly acidified under ambient conditions, caused by the base cation supply decreasing faster than the decrease of SO₄ ², as pollution abates. Export of Al, Fe and, P is mimicking that of the manipulated watershed, but is lower in magnitude and lags in time. Probable increasing SO₄ ^2- adsorption caused by acidification has moderated the longer-term trends of acidification of both watersheds. The trends of decreasing base cations were interrupted by the effects of several short-term events, including severe ice storm damage to the canopy, unusual snow pack conditions, snow melt and rain storms, and episodic input of marine aerosols. These episodic events alter alkalinity by5 to 15 μeq L^-1 and make it more difficult to determine recovery from pollution abatement.     

Non-biodegradable landfill leachate treatment by combined process of agitation,coagulation, SBR and filtration

This study describes the complete treatment of non-biodegradable landfill leachate by combined treatment processes. The processes consist of agitation as a novel stripping method used to overcome the ammonia toxicity regarding aerobic microorganisms. The NH₃-N removal ratio was 93.9% obtained at pH 11.5 and a gradient velocity (G) 150 s^?1 within a five-hour agitation time. By poly ferric sulphate (PFS) coagulation followed the agitation process; chemical oxygen demand (COD) and biological oxygen demand (BOD₅) were removed at 70.6% and 49.4%, respectively at an optimum dose of 1200 mg L^?1 at pH 5.0. The biodegradable ratio BOD₅/COD was improved from 0.18 to 0.31 during pretreatment step by agitation and PFS coagulation. Thereafter, the effluent was diluted with sewage at a different ratio before it was subjected to sequencing batch reactor (SBR) treatment. Up to 93.3% BOD₅, 95.5% COD and 98.1% NH₃-N removal were achieved by SBR operated under anoxic–aerobic–anoxic conditions. The filtration process was carried out using sand and carbon as a dual filter media as polishing process. The final effluent concentration of COD, BOD₅, suspended solid (SS), NH₃-N and total organic carbon (TOC) were 72.4 mg L^?1, 22.8 mg L^?1, 24.2 mg L^?1, 18.4 mg L^?1 and 50.8 mg L^?1 respectively, which met the discharge standard. The results indicated that a combined process of agitation-coagulation-SBR and filtration effectively eliminated pollutant loading from landfill leachate.     

Fluxes of NO3-, NH4+, NO,NO2, and N2O in an Old Danish Beech Forest

The fluxes of the major nitrogen compounds havebeen investigated in many ecosystem studies over the world.However, only in few studies has attention been drawn to theimportance of the fluxes of minor gaseous nitrogen compoundsto complete the nitrogen cycle. In Denmark a detailed study onthe nitrogen cycle in an old beech forest has been implementedin 1997 at Gyrstinge near Sorø, Zealand. The study includesthe fluxes of the gases NO, N₂O and water mediatedtransport of NO₃ ^- and NH₄ ⁺. Measurementsof the fluxes of the gaseous compounds are performed withmicro-meteorological methods (eddy-correlation and gradient)and with chambers. Water mediated fluxes encompass rain,throughfall, stem-flow and leaching from the root zone. Thehydrological model is verified by TDR measurements. The findings show that the total water mediated N input tothe forest floor with throughfall and stemflow was 25.6 kg Nha^-1 yr ^-1, and open field wet deposition withprecipitation was 19.0 kg N ha^-1 yr ^-1. The internalcycling of N in the ecosystem measured as turnover oflitterfall and plant uptake was 100 kg N ha^-1 yr ^-1and 14 kg N ha^-1 yr ^-1, respectively. The fluxes ofthe gaseous N compounds NO and N₂O were of minorimportance for the total N turnover in the forest, NO_xemission being <1 kg N ha^-1 yr ^-1 and N₂Oemission from the soil being 0.5 kg N ha^-1 yr ^-1 withno significant difference between wet and dry soils.Concentrations of NO₃ ^- and NH₄ ⁺ in thesoil solution beneath the rooting zone are very small andconsequently the N leaching is almost negligible. It isconcluded that the nitrogen mass balance of this old beechforest ecosystem mainly is controlled by the input by dry andwet deposition and a large internal N cycle with a fast litterturnover. The nitrogen input tothe forest ecosystem which currently exceeds the critical loadby 5 kg N ha^-1 yr ^-1is mainly accumulated in the soil and no significant nitrateleaching is occurring.     

Effects of Nitrogen Deposition on Bryophyte Species Composition of Calcareous Grasslands

Regular additions of NH₄NO₃ (35–140 kg N ha⁻¹ yr⁻¹) and (NH₄)₂SO₄ (140 kg N ha⁻¹ yr⁻¹) to a calcareous grassland in northern England over a period of 12 years have resulted in a decline in the frequency of the indigenous bryophyte species and the establishment of non-indigenous calcifuge species, with implications for the structure and composition of this calcareous bryophyte community. The lowest NH₄NO₃ additions of 35 kg N ha⁻¹ yr⁻¹ produced significant declines in frequency of Hypnum cupressiforme, Campylium chrysophyllum, and Calliergon cuspidatum. Significant reductions in frequency at higher NH₄NO₃ application rates were recorded for Pseudoscleropodium purum, Ctenidum molluscum, and Dicranum scoparium. The highest NH₄NO₃ and (NH₄)₂SO₄ additions provided conditions conducive for the establishment of two typical calcifuges – Polytrichum spp. and Campylopus introflexus, respectively. Substrate-surface pH measurements showed a dose-related reduction in pH with increasing NH₄NO₃ deposition rates of 1.6 pH units between the control and highest deposition rate, and a further significant fall in pH, of >1 pH unit, between the NH₄NO₃ and (NH₄)₂SO₄ treatments. These results suggest that indigenous bryophyte composition may be at risk from nitrogen deposition rates of 35 kg N ha⁻¹ yr⁻¹ or less. These effects are of particular concern for rare or endangered species of low frequency.     

Controls on leaching of N species in upland moorland catchments

Spatial and temporal changes in mobility of N species have been studied for three UK upland river networks, the Etherow in the South Pennines, the Nether Beck in the Lake District and the Dee in NE Scotland. The catchments are subject to N deposition at 35.1, 22.0 and 10.8–15.6 kg N ha^?1 yr^?1, respectively. The NH⁺ ₄ leaching appears to be predominantly regulated by flow path in more polluted upland catchments. It is greatest where water draining acidified peaty soils contributes more to total discharge. Soluble organic matter may provide the dominant counter anion. In the Etherow and Dee catchments, which are dominated by acid mineral and organic soils, at high discharge NO^? ₃ also appears to be associated with greater input of water from acidified soils. In contrast, for the Nether Beck, higher NO^? ₃ concentrations are associated with tributaries draining soils contributing water with higher alkalinity, suggesting nitrification is important. For the Etherow and Dee, dissolved organic N (DON) appears to originate predominantly from acidified, peaty soils. Spiking experiments with peat soil from the Etherow catchment confirmed the limited capacity of these soils to utilize inorganic N inputs, favouring equilibration with NH⁺ ₄ inputs and leaching losses of inorganic N throughout the year.     

Chemical Composition and Acidity of Rain at the Gulf of Iskenderun,North-East Mediterranean

The purpose of the present work was to investigate the chemistry of rain in the Gulf of Iskenderun, North East Mediterranean, Turkey. The Gulf region has a large number of industries. Main industries existing in the region are iron and steel works, fertilizer plants, a cement plant, and several medium and mini size steel mills in addition to the international pipe line terminals. This study aims to apportion the local sources contributing to the overall pollution of the region. To this end a precipitation sampling program was started in January 2000, and over 48 precipitation samples were collected from each of 5 stations located at Iskenderun city center, Iskenderun industrial zone, Payas city center, the campus of Iskenderun Technical College and the campus of Mustafa Kemal University. Samples were analysed for pH, NO₃ ⁺, Cl^-. Ca, Al, Ba, Na, Cd, Co, Cr, Cu, Pb, Li, Mg, Mn, Ni, Zn, Fe, K. Concentrations of metal ions were determined by ICP-AES. NO₃ ^- ions and pH were determined by using NO₃ ^- selective electrode and pH meter, respectively.pH values of the collected samples at the industrial zone and at Payas city center, ranged between 5.02 and 7.38, respectively. NO₃ ^- and metal ions concentrations were highly variable. Concentrations of Ca and Fe ions were higher in the industrial zone and Payas city center. In the other three stations, concentrations of metal ions and NO₃ ^- ion were lower than that of industrial zone and the values of pH ranged between 6 and 7.4. The average pH values at Iskenderun Gulf showed that the precipitation was not acidic, because of the high concentration of Ca. The highest concentrations of Na and Cl ions were recorded in the University campus because the campus is located by the Mediterranean Sea.     

Comparison of PM2.5 and PM10 in A Suburban Area in Korea During April, 2003

Airborne particulate matter (PM) concentrations were measured in Iksan, a suburban area in South Korea during April, 2003. PM_2.5 (particles with an aerodynamic diameter less than 2.5 μm) and PM₁₀ (particles with an aerodynamic diameter less than 10 μm) samples were collected, and the chemical characteristics of particles were examined for diurnal patterns, yellow dust/rainfall influences, and scavenging effects. Average concentrations of PM_2.5 and PM₁₀ mass measured were 37.3 ± 16.2 μg m⁻³ and 60.8 ± 29.5 μg m⁻³, respectively. The sum of ionic chemical species concentrations for PM_2.5 and PM₁₀ was 16.9 ± 7.3 and 23.1 ± 10.1 μg/m³, respectively. A significant reduction in PM mass concentrations during rainfall days was observed for coarse mode (PM_{2.5 − 10}) particles, but less reduction was found for fine (PM_2.5) mass concentration. SO₄ ²⁻, NH₄ ⁺, and K⁺ predominated in fine particulate mode, NO₃ ⁻ and Cl⁻ predominated in fine particle mode and coarse particle mode, but Na⁺, Mg²⁺, and Ca²⁺ mostly existed in coarse mode. The high concentration of ammonium due to local emissions and long-range transport neutralized sulfate and nitrate to ammonium sulfate and ammonium nitrate, which were major forms of airborne PM in Iksan. Average mass concentrations of PM₁₀ in daytime and at night were 57.6 and 70.0 μg m⁻³, and those of PM_2.5 were 35.4 and 42.5 μg m⁻³, respectively. NO₃ ⁻ and Cl⁻ in both PM_2.5 and PM₁₀ were about double at night than in the daytime, while the rest of the chemical species were equal or a little higher at night than in the daytime. The results suggest the formation of ammonium nitrate and chloride when high ammonia concentration and low air temperature are allowed. Backward air trajectory analyses showed that air masses arriving at the site during yellow dust period were transported from arid Chinese regions, which resulted in high concentrations of airborne PM mass concentrations. In the meantime, air mass trajectories during a rainfall period were mostly from the Pacific Ocean or the East China Sea, along with a relatively low PM concentration.