Calculating nitrogen deposition in Europe

Nitrogen deposition calculations for Europe were performed by separate models describing the long-range transport of ammonia and oxidized N. A linearized version of a non-linear atmospheric chemistry model was used for calculating oxidized N. Model computations were found to be consistent with the observed spatial pattern of wet nitrate deposition in Europe. Interannual meteorological variability was estimated to cause a typical year-to-year variation in annual oxidized N deposition of about 6 to 10%. Nitrogen deposition was computed for several NO _x emissions reduction scenarios. These scenarios were derived from an OECD study and applied to the 27 largest countries in Europe. Most reduction scenarios affected the deposition pattern of oxidized N, but the most extreme NO _x emission reduction scenario did not change very much the overall pattern of total (oxidized N plus ammonia N) N deposition. Depending on the desired level of environmental protection, it may be necessary to reduce ammonia emissions in addition to NO _x emissions in order to reduce N deposition in Europe.     

Comparison of RADM dry deposition algorithms with a site-specific method for inferring dry deposition

Data collected during 1986 at seven widely separated sites in the eastern United States were used to estimate weekly averages of deposition velocities for SO₂, O₃, HNO₃, and SO _inf4 ^sup2? with both a modified version of the RADM dry deposition module and a site-specific inferential technique developed by the Atmospheric Turbulence and Diffusion Division of the National Oceanic and Atmospheric Administration's Air Resources Laboratory. The results show some systematic differences between the two techniques, even when the module uses distributions of landuse types that match as closely as possible the observed vegetation coverages used in the inferential technique. When one ignores the systematic differences that easily could be removed by minor changes in the algorithms for computing resistances to deposition, weekly averages of the deposition velocities calculated with the two methods are within approximately ±30% of each other for SO₂ and O₃. Overall, the relative differences in the deposition velocities for HNO₃ and SO _inf4 ^sup2? are about ±30 and ±50%, respectively. Use of the module with landuse types extrapolated to areas as large as RADM grid cells (approximately 80 km square) around the measurement stations produces weekly averages within ±20% of the site-specific estimates for SO₂, O₃, and SO _inf4 ^sup2? and approximately ±30% for HNO₃ if one avoids landuse types such as urban and water areas that are both nonrepresentative and have very different characteristics from the measurement sites. These estimates are not complete measures of the true uncertainty associated with the two techniques because they do not account for such effects as differences in the siting of instrumentation for collecting input data and the inability of the computational algorithms to include the many surface nonuniformities that typically exist in the areas surrounding measurement sites.     

A comparison of a multilayer regional-scale acid rain assessment model (MLRAPT) with a single-layer assessment model,RAPT

This study, which is part of the 1985 Assessment on Current Damages of Acid Deposition, examines uncertainty due to treating transport processes using a single-layer model compared to a multilayer model. The Multilayer Regional Air Pollutant Transport Model, MLRAPT, was run in both modes, single layer and multilayer, using 224 sources during a 22-day period in July 1978 for the northeastern United States. Comparison between the two modes indicated that the average air concentrations were highly correlated (a correlation coefficient of 0.98). However, for wet deposition of SO₄, a correlation coefficient of 0.55 between the two predicted wet deposition fields was obtained. Results of the comparison of the two modes with the observed air concentration fields and with a limited comparison of observed wet deposition indicate that caution should be used when interpreting results of a single-layer model to develop source/receptor relationships.     

Estimating the atmospheric input of pollutants into a watershed

Estimating the atmospheric input of ions to a watershed has traditionally been accomplished through either the extrapolation of point measurements of deposition or the integration of model estimated deposition. This paper examines the characteristics of precipitation chemistry on the eastern seaboard of the United States where precipitation quality could conceivably affect fish habitats in estuaries. The measured values presented here have been extracted from the data base of the Utility Acid Precipitation Sampling Program (UAPSP) precipitation chemistry network. These data illustrate the nature of ionic deposition at four points on the eastern seabord. The deposition of H' (acidity) is shown to be dependent upon the amount of sulfate and, to a lesser degree, nitrate in the precipitation. It is also shown that the quantity of ionic deposition on a storm-by-storm basis was influenced by the amount of water deposition but the relationship was not very strong. Thus the use of water deposition as a surrogate for ionic deposition is not justified in these watersheds. Finally, it is shown that the deposition of H⁺, SO₄ ^2?, NO₃ ^?, and NH₄ ⁺ were not clearly seasonal. While a large percentage of total ionic deposition occurred in a small number of precipitation events, these exceptional events were not confined to a particular season.     

Titanium oxide nanoparticle effects on composition of soil microbial communities and plant performance

We examined the effect of TiO₂ nanoparticles (NPs) on the growth of maize and soybean plants and associated soil microbial communities. Plants were grown in a greenhouse, and low levels of undoped or nitrogen-doped TiO₂ NPs were applied. Plant growth and nutrient content were determined, and effects of NPs on composition of soil microbial communities were examined using terminal restriction fragment length polymorphism analysis (TRFLP) of rDNA. We found no significant effects of TiO₂ NPs on plant growth, nutrient content, or the composition of bacterial communities within the rhizosphere. However, arbuscular mycorrhizal fungal communities were affected by application of undoped and nitrogen-doped TiO₂ NPs. This observation may be partially attributed to the small but significant TiO₂ NP uptake levels in the root tissues of both plants. Our results suggest that even low concentrations of TiO₂ NPs may influence some important groups of soil microbes, such as mycorrhizal fungi, but changes in the composition of microbial communities may not affect plant growth under conditions of adequate moisture and nutrients.     

Response surface methodology to understand the anaerobic biodegradation of organochlorine pesticides (OCPs) in contaminated soil—significance of nitrate concentration and bioaccessibility

Purpose

Problems associated with Organochlorine pesticide (OCP)-contaminated soils have received wide attention. To understand the anaerobic biodegradation process constraints, innovative mathematical analysis methods are effective.

Materials and methods

Response surface methodology (RSM) and Tenax TA extraction method combined with the first-three-compartment model were employed to systematically investigate the role of nitrate concentration and bioaccessibility enhancer (methyl-β-cyclodextrin, MCD) in the anaerobic biodegradation of OCPs in contaminated soil.

Results and discussion

The sole addition of either KNO₃ or MCD could facilitate the anaerobic biodegradation of OCPs. The highest biodegradation for total OCPs, hexachlorocyclohexanes, endosulfans, and chlordanes were 71.6, 82.1, 68.3, and 55.6 %, respectively, when 20 mM KNO₃ and 3.0 % (w/w) MCD were applied simultaneously. As predicted by RSM, the theoretical maximum biodegradation for total OCPs ranged from 60 to 80 % when 20 to 25 mM KNO₃ and >2.5 % (w/w) MCD were applied simultaneously. Tenax TA extraction method demonstrated the enhancement of OCP bioaccessibility caused by MCD addition. Changes in the soil microbial activities also suggested the positive effects of adding suitable amounts of KNO₃ as a cosubstrate to facilitate the anaerobic biodegradation of OCPs.

Conclusions

The amount of KNO₃ and MCD are crucial in influencing OCP biodegradation. RSM was demonstrated to be a powerful tool to estimate and predicting the optimal OCP biodegradation under KNO₃ and MCD application simultaneously.     

The experimental phytotoxicology of germanium in relation to silicon

The common belief that the sensitivity of plants to Ge is evidence for a Si requirement has been examined experimentally using barely, wheat, cucumber and radish cultivars. All 4 test plants were inhibited by Na₂GeO₃ (metagermanate) at 1 mM or less, including germination, shoot height, root length, and first leaf growth in barley and wheat. The application of Na₂SiO₃ (metasilicate) counteracted Ge-inhibition only in barley. Further, only barley growth was stimulated by the application of Na₂SiO₃. Necrotic lesions were characteristic of Ge-toxicity only in barley leaves, and were reduced when Na₂SiO₃ was supplied.     

Influence of labelled food type on the accumulation and retention of 60Co by a freshwater fish,Cyprinus carpio L.

The study was carried out on 3 groups of 10 fish, each fed on a different natural labelled food. The preys selected were a crustacean (Gammarus pulex), a midge larvae (Chironomus sp.) and the soft tissues from a snail (Lymnaea stagnalis), which are usually consumed by carp in the natural environment. The contaminated food consumption by the fish resulted in a ⁶⁰Co maximum transfer factor ranging from 1.2 × 10^?2 to 5.1 × 10^?2 depending on the food type. These values, and the contamination kinetics indicate that the biomagnification of the radionuclides cannot occur, even over the long term. ⁶⁰Co depuration from fish was also influenced by the contaminated food type, previously ingested. The lower elimination rate correspond to the higher value of the transfer factor (Gammarus pulex) and inversely (Lymnaea stagnalis).     

BOD/TOC correlations and their application to water quality evaluation

The error residual for TOC analysis is examined with the result that two BOD₅/TOC models are suggested, both of which use a multiplicative error structure. A comparison of these models with the historically-assumed linear BOD₅/TOC model is created for data collected from the City of Waterloo's Water Pollution Control Plant. The predictive capabilities of the derived BOD₅/TOC models are examined for interpolation and extrapolation potentials for augmenting water quality data information bases. Use of the models to reduce the statistical uncertainty associated with BOD measurements is considered.     

A mechanism for hydrochloric acid production in cloud

A theoretical model describing the general interaction between atmospheric trace gases, such as S0₂, NH₃, C0₂ and 0₂, chemical reactant gaseous product H₂SO₄ and hydrometeors containing NaCl is proposed to study a possible mechanism for HCl production in non-precipitating cloud and the determination of the pH value of cloud droplets. Four different cloud droplet distributions have been used to estimate the upper limit of the amount of gaseous HCl released into the atmosphere resulting from the evaporation of cloud droplets. It is shown that the acid production and the amount of HCl released depend on the following factors: (a) the temperature of the cloud; (b) the oxidation rates; (c) the ambient concentration of SO₂, NH₃, and H₂SO₄; (d) the life cycle of the cloud; and (e) the liquid content of the cloud. This proposed chemical model also predicts a pH value spectrum depending on the cloud droplet distribution. Field measurements for the dependence of pH value on particle size and spatial distribution of gaseous HCl are recommended.     

The role of atmospheric deposition in an eastern U.S. deciduous forest

Atmospheric sources contributed significantly to the annual flux of trace metals and sulfate to the forest floor of Walker Branch Watershed, a forested catchment in the southeastern United States. Atmospheric deposition supplied from 14% (Mn) to≈40% (Zn, Cd, So ₄ ⁼ ) to 99% (Pb) of the annual flux to the forest floor; the remainder was attributable to internal element cycling. The measured water solubility of these metals in suspended and deposited particles indicates that they may be readily mobilized following deposition. Dry deposition constituted a major fraction of the total annual atmospheric input of Cd and Zn (≈20%), SO=(≈35%), Pb(≈55%), and Mn (≈90%); however, wet deposition rates for single events exceeded dry deposition rates by one to four orders of magnitude. Interception of rain by the canopy resulted in loss of Cd, Mn, Pb, Zn, and SO⁼ from the canopy, but uptake of H⁺ which increased with increasing free acidity of the incoming rain, and with increasing residence time of the rain on the leaf surface.     

Deposition of nutrients and major ions by precipitation in south-central Ontario

As part of a study of the substance budgets of lakes in south-central Ontario, a network of precipitation collectors (8 bulk, 7 wet only) was operated to measure the deposition of nutrients and major ions. Results are reported for total P, total Kjeldahl N, NO ₃ ^? ?N, NH ₄ ⁺ ?N, total N, Fe, H⁺, Ca⁺⁺, Mg⁺⁺, Na⁺, K⁺, SO ₄ ⁼ and CL^? for a two year period (August 1976–July 1978). On an equivalent basis the dominant anion in both bulk and wet precipitation was SO ₄ ⁼ , with H⁺ the dominant cation. Precipitation in the study area is more acidic than that analyzed at any other location on the Canadian Shield to date. Concentrations of ions varied by 1 to 3 orders of magnitude between individual precipitation events and annual deposition varied by as much as 2-fold in the two years of study. Annual wet deposition contributed >60% of bulk deposition for all substances except total P. Seasonal trends in deposition with summer maxima were noted for most ions. For Harp Lake, a small Precambrian Lake with a lake area of 12.6% of its total drainage area, precipitation input directly to the lake surface was an important source of nutrients and major ions. This was especially the case for P, N and H⁺ because these substances were retained by the terrestrial drainage basin.     

The origin and deposition history of polycyclic aromatic hydrocarbons in the finger lakes region of New York

Studies aimed at determining the deposition history of energy related, potentially carcinogenic, polycyclic aromatic hydrocarbons (PAHs) deposited in the sediments of Cayuga Lake, in the Finger Lakes Region of central New York State, are described. PAH fluxes in the 1850's were at least an order of magnitude less than the maximum rates in the period of 1940 to 1955. PAH fluxes began to decline before the Milliken coal fired power plant, located on Cayuga Lake, started service in 1955. Correlation between the PAH flux into the sediments and fossil fuel usage and emissions for the states of New York, Ohio and Pennsylvania and the United States as a whole, suggests that modern, high efficiency fossil fuel fired power plants are minor sources of PAHs compared to coal related residential heating and industrial combustion. Similar comparisons with historic emissions data do not support the hypothesis that PAH flux is a useful indicator of the combustion sources which produce the `acidifying' compounds SO₂ and NO_x for the Finger Lakes region.     

Comparative evaluation of NTA and EDTA for extractive decontamination of Pb-polluted soils

Nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) were compared for their ability to solubilize Pb from a highly-contaminated (PbT 21%) soil collected from a battery recycling facility. For chelant concentrations below 0.04 M (representing a 1:1 chelant-to-Pb_T molar ratio), EDTA released 10 to 30% more Pb than NTA. NTA-to-Pb T ratios greater than 1:1 reduced Pb recovery because of readsorption of Pb(NTA)₂ ^4? onto positively-charged oxide soil components at pH < 8.5. For the EDTA system, however, complexation completely bound all coordination sites of Pb and EDTA, leaving no functional groups available for surface adsorption. Thus, Pb recovery progressively increased with higher EDTA concentrations, although the additional Pb release with each EDTA increment became smaller. For pH < 5 and EDTA/Pb of 2:1, Pb recovery exceeded 90%. The addition of 0.5 M NaC1O₄ enhanced Pb recovery by EDTA for pH 5 to 12, but substantially suppressed recovery by NTA for pH < 11. Because Pb release by NTA was diminished by high ionic strength and chelant-to-metal ratios, NTA may be limited as a soil washing reagent. Stronger complexation and consistent Pb desorption behavior by EDTA favors its use.     

Pyro- and tripoly-phosphate contents of sediments

A method to determine pyrophosphate (PP) and tripolyphosphate (TPP) in sediments was developed. Sediment was extracted with 2% EDTA + 0.1 M NH₄F followed by a second extract of 2% EDTA + 1 N NaOH. Orthophosphate (OP), PP, and TPP were separated by anion exchange chromatography, the fractions collected, and P determined after extraction into isobutanol. The limit of detection of the method was 0.5 μg P g^?1 sediment. Fourteen sediments were tested and the highest TPP found was 1.8 μg P g^?1 sediment. Thirteen of the sediment samples contained less than 1 μg P g^?1 as TPP. Only three of the 14 samples contained more than 1 μg P g^?1 as PP. The highest level of PP (8.5 μg P g^?1) was found in sediment from an animal waste lagoon. Estimates of error and reproducibility were made from analysis of samples with added PP and TPP. The error for samples containing 36.9 μg P g^?1 as PP was ± 7.6, and for TPP at 12.3 μg P g^?1 the error was ± 3.3. The values for PP and TPP were underestimated by 6 and 36%, respectively.     

Structural Influence on Photooxidative Degradation of Halogenated Phenols

The influence of structure on degradation of five halogenated phenols (XPs) by UV/H₂O₂ process was investigated. The combined influence of type or number of substituents and UV/H₂O₂ process parameters (pH and [H₂O₂]) on the degradation kinetics of 2-fluorophenol (2-FP), 2-chlorophenol (2-CP), 2-bromophenol (2-BP), 2,4-dichlorophenol (2,4-DCP), and 2,4,6-trichlorophenol (2,4,6-TCP) was studied using modified miscellaneous 3³ full factorial design and response surface modeling (RSM). Studied XPs obey first-order degradation kinetics within the investigated range of process parameters. Determined degradation rate constants (k _obs) were correlated with process and structural parameters by the quadratic polynomial models. Analysis of variance (ANOVA) demonstrated RSM models’ accuracy and showed that, in addition to pH and [H₂O₂], model terms related with the pollutant structure are highly influential. k _obs of mono-XPs follow the decreasing order 2-FP, 2-CP, and 2-BP, while CPs follow the decreasing order 2-CP, 2,4-DCP, and 2,4,6-TCP. Biodegradability (biochemical oxygen demand (BOD)₅/chemical oxygen demand (COD)) and toxicity (TU) were evaluated prior to the treatment and at the reference time intervals. The observed differences are correlated with the structural characteristics of studied XPs.     

Aluminum speciation in soil solutions: Equilibrium calculations

A computer simulation was done to illustrate how the equilibrium solubility and speciation of Al in well-aerated soil solutions may be affected by pH (from 2.0 to 10.0), organic acids (citric, oxalic, phthalic, and salicylic acid), metal ions (K, Mg, Ca, Al, Fe), inorganic ligands (F, OH, SO₄, PO₄, CO₃, and SiO₃), and type of Al-containing solid [kaolinite, gibbsite, or amorphous Al(OH)₃] thought to be present. The simulation indicated that the type of Al-oxide/hydroxide considered has a substantial influence on the inorganic and organic equilibrium composition of the soil solution, and on the occurrence (or non-occurrence) of other Al-minerals such as KA1₃(SO₄)₂(OH)₆ (alunite) and Al(SO₄)(OH)-5H₂O (jurbanite).     

Mercury volatilization from a floodplain soil during a simulated flooding event

Purpose

Middle-European floodplain soils are often contaminated with mercury (Hg) and periodically flooded. In this study, the influence of a flooding event and subsequent dewatering on the volatilization of elemental Hg and methylated species was investigated in a laboratory experiment.

Material and methods

Undisturbed soil cores were taken from a topsoil (12.1?±?0.75 mg kg^?1 Hg) at the Elbe River in Lower Saxony, Germany. Soil columns were incubated at 20 °C with varying soil moisture (water-saturated for 2 weeks, 95 and 90 % water content for 1 week each), and the redox potential (E_H) was recorded. The gaseous Hg that accumulated in the headspace of the flux chamber of the columns was pumped over cooled traps filled with adsorber material and analyzed by gas chromatography/inductively coupled plasma mass spectrometry for the various Hg species.

Results and discussion

The watering of the soil resulted in a rapid decrease in the E_H and the achievement of strongly reducing conditions (E_H??1 Hg at the beginning to 5.78 μg L^?1 Hg at the end of the experiment. Species analyses revealed that exclusively elemental Hg volatilized. The volatilization rate was between 1.73 and 824 ng m^?2 h^?1 Hg, which is consistent with other studies at the Elbe River.

Conclusions

Even when flooded for a longer period of time, floodplain soils should show neither emission of methylated Hg nor exceptionally high volatilization of elemental Hg.     

Mobilization of heavy metals from river sediments of Northern Greece by complexing agents

The influence of NTA, EDTA, STPP, Triton X100, PO _inf4 ^sup3 and NO _inf3 ^sup? on the mobilization of Pb, Cd, Cu, Cr and Mn from sediments of two rivers located in Northern Greece was studied. The release caused by all examined complexing agents was higher in deionized water than either Axios or Aliakmon river water due to the lack of competition of Ca and Mg cations with the heavy metals for the studied complexing agents, and the decrease of ionic strength. From all examined agents NTA and EDTA showed the greater mobilization ability. Copper showed the greater tendency for remobilization by all examined agents, (according to the order: EDTA?NTA, Triton X1004 PO _inf4 ^sup3? > NO _inf3 ^sup3? ?STPP) while Cr and Mn the smallest following the orders: NTA, PO _inf4 ^sup3? >> NO _inf3 ^sup? , Triton X1004 EDTA, STPP and STPP > EDTA > NTA > Triton X 100 ? PO _inf4 ^sup3? NO₃, respectively. An increase in mobilization was noticed with an increase of agent concentration and time of shaking.     

Atmospheric pollution and fallout by PCBS and organochlorine pesticides (Ile-De-France)

Air pollution and atmospheric deposition by PCBs and organochlorine pesticides (isomers of HCH and p,p′-DDE) were studied at Paris from January 1986 to June 1987. The deposition measured as total (wet plus dry) was also followed during 1986 on two suburban and two rural sites. The distribution of the pollutants between the vapor phase and aerosols was evaluated by sampling air through a glass microfiber filter connected to a Tenax resin cartridge. The study shows that in the atmosphere as in waters of the catchment area of the Seine river, PCBs are the main organochlorine pollutants. Pollution by OCL is of the same order as the one described in literature (mean γ-HCH concentration 1.4 ng m^?3) while PCB concentrations in the atmosphere are equal to or higher than those observed in USA and Europe (range 5 to 44 ng m^?3). On the average, 93% of the PCBs are in the vapor phase with a composition approximating Aroclor 1242. In aerosols and precipitations the composition is closely related to Aroclor 1254. The total fallout for 1986 was 40 μg m^?2 for PCBs and 20 μg m^?2 for γ-HCH, rainfall being 611 mm.