Seasonal dry deposition and canopy leaching of base cations in a subtropical evergreen mixed forest, China

Reactive nitrogen (Nr) compounds comprise essential nutrients for plants. However, a large supply of nitrogen by fertilization through atmospheric deposition may be harmful for ecosystems such as peatlands and may lead to a loss of biodiversity, soil acidification and eutrophication. In addition, nitrogen compounds may cause adverse human health impacts. Large parts of Nr emissions originate from anthropogenic activities. &#160;Emission hotspots of &#931;Nr, i.e. the sum of all Nr compounds, are related to crop production and livestock farming (mainly through ammonia, NH3) and fossil fuel combustion by transport and industry (mainly through nitrogen oxides, NO2 and NO). Such additional amount of Nr will enhance its biosphere-atmosphere exchange, affect plant health and can influence its photosynthetic capacity. Therefore, it is necessary to thoroughly estimate the nitrogen exchange between biosphere and atmosphere.For measuring the nitrogen mixing ratios a converter for reactive nitrogen (TRANC: Total Reactive Atmospheric Nitrogen Converter) was used. The TRANC converts all reactive nitrogen compounds, except for nitrous oxide (N2O), to nitric oxide (NO) and is coupled to a fast-response chemiluminescence detector (CLD). Due to a low detection limit and a response time of about 0.3s the TRANC-CLD system can be used for flux calculation based on the eddy covariance (EC) technique. Flux losses, which are related to the experimental setup, different response characteristics and the general high reactivity of most N gases and aerosols, occur in the high frequency range. We estimated damping factors of approximately 20% with an empirical cospectral approach.For getting a reliable prediction of &#931;Nr fluxes through deposition models, long-term flux measurements offer the possibility to verify the nitrogen uptake capacity and to investigate exchange characteristics of &#931;Nr in different ecosystems.In this study, we compare modelled dry deposition fluxes using the deposition module DEPAC (DEPosition of Acidifying Compounds) within the chemical transport model LOTOS-EUROS (LOng Term Ozone Simulation &#8211; EURopean Operational Smog) against &#931;Nr flux measurements of the TRANC-CLD for a remote mixed forest site with hardly any local anthropogenic emission sources. This procedure allows to determine the background load and the natural exchange characteristics of nitrogen under low atmospheric concentrations. Therefore, the broad-scale dry deposition predicted directly by LOTOS-EUROS was compared to site-specific modelling results obtained using measured meteorological input data as well as the directly measured &#931;Nr fluxes. In addition, the influence of land-use weighting in LOTOS-EUROS was examined. We further compare our results to &#931;Nr deposition estimates obtained with canopy budget techniques. Measured &#931;Nr dry deposition at the site was 4.5 kg N ha-1 yr-1, in close agreement with modelled estimates using DEPAC with measured drivers (5.2 kg N ha-1 yr-1) and as integrated in the chemical transport model LOTOS-EUROS (5.2 kg N ha-1 yr-1 to 6.9 kg N ha-1 yr-1 depending on the weighting of land-use classes).Our study is the first one presenting 2.5 years flux measurements of &#931;Nr above a remote mixed forest. Further verifications of long-term flux measurements against deposition models are useful to improve them and result in better understanding of exchange processes of &#931;Nr.

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Throughfall and stemflow chemistry under deciduous and coniferous forest canopies in south-central Ontario

Canadian Journal of Forest Research ◽

10.1139/x94-145 ◽

1994 ◽

Vol 24 (6) ◽

pp. 1089-1100 ◽

Cited By ~ 92

Author(s):

A.J. Neary ◽

W.I. Gizyn

Keyword(s):

Dry Deposition ◽

Forest Canopy ◽

Coniferous Forest ◽

Base Cations ◽

Ion Sources ◽

Regression Technique ◽

Forest Canopies ◽

South Central ◽

Internal Sources ◽

Scavenging Efficiency

By measuring incident precipitation, throughfall, and stemflow chemistry, the roles of coniferous- and deciduous-dominated forest canopies as a source of and sink for ions in precipitation were examined. A regression technique for distinguishing between external (dry deposition) and internal (canopy leaching) sources of ions in the throughfall flux was evaluated. The effect of seasonal changes in the forest canopy on throughfall and stemflow chemistry was also examined. Throughfall comprised 74 and 84%, respectively, of the hydrologic flux at the coniferous and deciduous sites. Sulphate fluxes were highest at the coniferous site during both growing and dormant seasons, suggesting either a higher scavenging efficiency of the needles for atmospheric SO42−, or higher SO42− leaching from the foliage. The deciduous site neutralized acidic inputs, as demonstrated by its net negative H+ flux year round. The buffering capacity of the coniferous forest was exceeded by the higher amount of acid interception by the canopy. Nitrate behaved conservatively and base ions were exported from the canopy. Stemflow contributions of ions, although low, were generally higher than the contribution of stemflow to the hydrologic flux (2–3%). Independent dry deposition measurements for the growing season, when compared with net SO42− flux, overestimated dry deposition collected by the deciduous canopy, but were comparable to the flux at the coniferous site. These data suggest that dry SO2−SO42− deposition may be responsible for all SO42− enrichment seen in throughfall at these sites. A regression technique for separating internal and external ion sources in throughfall yielded inconsistent results, and attributed virtually all ion enrichment to internal sources. Problems with false assumptions and spurious correlations are discussed. We conclude that this method is not satisfactory for separating ion sources. Seasonal patterns in throughfall chemistry are present. During the growing seasons bases exchange for H+ and are exported similarly with SO42−. Hydrogen retention mirrors SO42− export. Base cations (particularly K+) are leached from the canopy primarily during senescence, but from the stem of the tree primarily during the dormant period. This was most evident at the deciduous site. Chloride behaved in a similar manner, while NH4+ and H+ were retained during the senescent period.

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Changes in the Physical Properties of Precipitation in Pine Stands in the Area with A Low Degree of Air Pollution (Western Pomerania)

Quaestiones Geographicae ◽

10.2478/quageo-2013-0017 ◽

2013 ◽

Vol 32 (3) ◽

pp. 27-37 ◽

Cited By ~ 1

Author(s):

Robert Kruszyk

Keyword(s):

Air Pollution ◽

Physicochemical Properties ◽

Physical Properties ◽

Dry Deposition ◽

Bulk Precipitation ◽

Total Load ◽

Low Degree ◽

Canopy Leaching ◽

Pine Stands

Abstract The study presents the results of research conducted in the years 2010-2012 in pine stands in Western Pomerania. The research included physicochemical properties of bulk precipitation and throughfall. The results confirm that despite a decrease in the total throughfall in the interception process, the size of mineral and organic depositions in pine stands exceeded values recorded for bulk precipitation. It was caused both by the process of enriching the throughfall with (K+, Mg2+) rinsed out of needles and leaves and by washing off the dry deposition (NH4+, Cl-, Na+, SO42-, NO3 -). The share of leaching processes for K+ was 74.1%, while for Mg2+ 23.6% of the total load of these elements brought to the ground with throughfall. In the case of Ca2+ no canopy leaching was observed for this element. The throughfall acidification processes were mostly caused by NO3-.

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Cation and anion fluxes in northern hardwood throughfall along an acidic deposition gradient

Canadian Journal of Forest Research ◽

10.1139/x93-064 ◽

1993 ◽

Vol 23 (3) ◽

pp. 457-467 ◽

Cited By ~ 11

Author(s):

Hal O. Liechty ◽

Glenn D. Mroz ◽

David D. Reed

Keyword(s):

Dry Deposition ◽

Acidic Deposition ◽

Strong Acid ◽

Northern Hardwood ◽

Ionic Concentrations ◽

Anionic Composition ◽

Canopy Leaching ◽

Atmospheric Inputs ◽

Deposition Gradient ◽

Precipitation Acidity

Ionic concentrations and fluxes were measured for 2 years in five northern hardwood stands along an acidic deposition gradient that extends from northern Minnesota (lowest deposition) to southeastern Michigan (highest deposition). Precipitation fluxes of H+, SO42−, and NO3− were, respectively, 340, 69, and 83% greater at the site with the highest deposition than at the site with the lowest deposition. No significant differences among sites were evident for precipitation fluxes of cations along the gradient. Fluxes of H+, SO42−, NO3−, Ca2+, and Mg2+ in throughfall increased along the gradient and were positively correlated with increased atmospheric inputs of H+, SO42−, and NO3− measured at the sites. Fluxes of SO42− and NO3− in throughfall were greater than precipitation fluxes, indicating dry deposition in excess of any assimilation of these anions from precipitation. Dry deposition inputs of SO42− increased from the northwestern to southeastern sites and were estimated to range from 23 to 49% of precipitation inputs. Precipitation acidity was neutralized by the canopy in all stands, but the amount of H+ retained by the canopy was significantly greater at sites with the greatest precipitation acidity. Throughfall fluxes of Ca2+ and Mg2+ in excess of precipitation fluxes were positively correlated with the canopy retention and deposition of H+ along the gradient. Increased throughfall fluxes of these cations were consistent with hypothesized increases in canopy leaching of cations with increased acidic deposition. Increased canopy leaching of Ca2+ and Mg2+, resulting from elevated acidic deposition, was estimated to represent as much as 6.2 and 12.9% of foliar contents of these cations, respectively. Although HCO3− and organic anions were found to play an important role in maintaining electroneutrality in throughfall along the gradient, strong acid anions increasingly dominated anionic composition of throughfall with increasing acidic deposition.

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Aerosol dynamics and gas-particle conversion in dry deposition of inorganic reactive nitrogen in a temperate forest

10.5194/acp-2019-703 ◽

2019 ◽

Author(s):

Genki Katata ◽

Kazuhide Matsuda ◽

Atsuyuki Sorimachi ◽

Mizuo Kajino ◽

Kentaro Takagi

Keyword(s):

Dry Deposition ◽

Land Surface ◽

Mixed Forest ◽

Chemical Transport ◽

Reactive Nitrogen ◽

Surface Model ◽

Deposition Flux ◽

Transport Models ◽

Aerosol Dynamics ◽

Chemical Transport Models

Abstract. Although dry deposition has an impact on nitrogen status in the forest environments, the mechanism for high dry deposition rates of fine nitrate aerosols (NO3-) observed in forests remains unknown and is a potential source of error in chemical transport models. Here we developed a new multi-layer land surface model coupled with dry deposition and aerosol dynamics processes for a temperate mixed forest in Japan. The processes of thermodynamics, kinetics, and dry deposition for mixed inorganic aerosols are modeled by a triple-moment modal method. The new model overall reproduces observed turbulent fluxes above the canopy and vertical micrometeorological profiles, as well as inorganic mass and size-resolved total number concentrations within the canopy. Sensitivity tests revealed that the within-canopy evaporation of ammonium nitrate (NH4NO3) under dry conditions significantly enhances deposition flux for fine NO3- and NH4+ aerosols, while reducing deposition flux for nitric acid gas (HNO3). A dry deposition scheme coupled with aerosol dynamics may be required to improve the predictive accuracy of chemical transport models for the surface concentration of inorganic reactive nitrogen.

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Dry deposition and canopy leaching rates in deciduous and coniferous forests of the Georgia Piedmont: an assessment of a regression model

Journal of Hydrology ◽

10.1016/0022-1694(94)02653-s ◽

1995 ◽

Vol 169 (1-4) ◽

pp. 131-150 ◽

Cited By ~ 27

Author(s):

Rosanna Cappellato ◽

Norman E. Peters

Keyword(s):

Regression Model ◽

Dry Deposition ◽

Coniferous Forests ◽

Canopy Leaching ◽

Georgia Piedmont

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Dry deposition of O 3 and SO 2 estimated from gradient measurements above a temperate mixed forest

Environmental Pollution ◽

10.1016/j.envpol.2015.11.052 ◽

2016 ◽

Vol 210 ◽

pp. 202-210 ◽

Cited By ~ 8

Author(s):

Zhiyong Wu ◽

Ralf Staebler ◽

Robert Vet ◽

Leiming Zhang

Keyword(s):

Dry Deposition ◽

Mixed Forest ◽

Temperate Mixed Forest ◽

Gradient Measurements

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Extension of a gaseous dry deposition algorithm to oxidized volatile organic compounds and hydrogen cyanide for application in chemistry transport models

10.5194/gmd-2021-41 ◽

2021 ◽

Author(s):

Zhiyong Wu ◽

Leiming Zhang ◽

John T. Walker ◽

Paul A. Makar ◽

Judith A. Perlinger ◽

...

Keyword(s):

Volatile Organic Compounds ◽

Organic Compounds ◽

Dry Deposition ◽

Hydrogen Cyanide ◽

Deposition Velocity ◽

Mixed Forest ◽

Chemical Species ◽

Flux Divergence ◽

Diel Cycles ◽

Volatile Organic

Abstract. With increasing complexity of air quality models, additional chemical species have been included in model simulations for which dry deposition processes need to be parameterized. For this purpose, the gaseous dry deposition scheme of Zhang et al. (2003) is extended to include 12 oxidized volatile organic compounds (oVOCs) and hydrogen cyanide (HCN) based on their physicochemical properties, namely the effective Henry's law constants and oxidizing capacities. Modeled dry deposition velocity (Vd) values are compared against field flux measurements over a mixed forest in the southeastern U.S. during June 2013. The model captures the basic features of the diel cycles of the observed Vd. Modeled Vd values are comparable to the measurements for most of the oVOCs at night. However, modeled Vd values are mostly around 1 cm s−1 during daytime, which is much smaller than the observed daytime maxima of 2–5 cm s−1. Analysis of the individual resistance terms/uptake pathways suggests that flux divergence due to fast atmospheric chemical reactions near the canopy was likely the main cause of the large model-measurement discrepancies during daytime. The extended dry deposition scheme likely provides conservative Vd values for many oVOCs. While higher Vd values and bi-directional fluxes can be simulated by coupling key atmospheric chemical processes into the dry deposition scheme, we suggest that more experimental evidence of high oVOC Vd values at additional sites is required to confirm the broader applicability of the high values studied here. The underlying processes leading to high measured oVOC Vd values require further investigation.

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