Monitoring and modelling of biosphere/atmosphere exchange of gases and aerosols in Europe

What is the character of N deposition and its proportion to NH3 and NOX inside horticultural greenhouse?

Nitrogen (N) deposition is a vital process of N cycling and is consequently important for the evaluation of N budgets. However, the character and quantity of N deposition inside the horticultural greenhouse remain unknown, impeding a deep understanding of N cycling among soil, vegetable and atmosphere. Here, we measured the dry and wet N deposition, and disentangled the relative percentages of ammonia (NH3) and nitrogen oxides (NOX) gases deposition based on the greenhouse vegetable cultivation experiment. Results found the annual N deposition, was 7.2-17.5 kg N·ha-1 under different chemical/organic N fertilizer managements, consisting of 77.0%-85.5% by dry deposition and 14.5-23% by wet deposition. The proportions of N deposition from NH3 and NOX emissions ranged within 37.5-83.0% under different N managements. The NH3 emission was the dominant driving factor of dry N deposition, while soil moisture was the dominant driving factor of wet N deposition. Controlled-release fertilizer combined with organic fertilizer resulted in the lowest N deposition (10.2 kg N·ha-1) and NH3 and NOX emissions (12.5 kg N·ha-1), which could be recommended as the mitigation strategy in greenhouse cultivation. This study investigated the dry and wet N deposition characteristics and their influencing factors, as well as the proportion of N deposition attributed to NH3 and NOX emissions, which provides preliminary understanding of N deposition and the reactive N gas diffusion from greenhouse into the atmosphere.

Sharply and simultaneously increasing pollutant accumulations in cells of organisms induced by rare earth elements in the environment of Nanjing

Exploring the factors that simultaneously increase the accumulation of various pollutants in cells of organisms to restrict the toxic effects of pollutants on organisms has become a focus of research aimed at protecting ecosystems. Here, we found that the accumulation of organic [e.g., benzo(a)pyrene (BaP)], inorganic [e.g., cadmium (Cd)] and emerging [e.g., rare earth elements (REEs)] pollutants in leaf cells of different plants grown in Nanjing was 567-1022%, 547-922% and 972-1392% of those grown in Haikou, respectively, when the concentration of REEs in rainwater of Nanjing and Haikou was 4.31 × 10^-3 μg/L and 3.04 × 10^-6 μg/L. Unprecedentedly, endocytosis in leaf cells of different plants grown in Nanjing was activated by REEs, and then extracellular BaP, Cd and REEs (e.g. terbium) were transported into these leaf cells together via endocytic vesicles. Particularly, the co-accumulation of those pollutants in these leaf cells was sharply increased, thus magnifying their toxic effects on these plants. Furthermore, the co-accumulation of those pollutants in human cells was also significantly increased by REEs, in a similar way to these leaf cells. Therefore, REEs in environments are key factors that greatly increase the co-accumulation of various pollutants in cells of organisms. These results provide new insights into how pollutants are accumulated in cells of organisms in ecosystems, informing a reference for making policy to ensure the safety of ecosystems.

Forest Transformation Urgency for Topsoil Diversity Optimization During Environmental Change

Combined effect of environmental change and management variability leads to reduced soil diversity in homogenous forest stands. On the other hand, forest soil diversity is maintained with rich tree species composition. In this study, focus has been put on deriving urgency to change forest tree species composition in order to increase soil diversity in biogeographic regions with uneven impact of environmental change. The relation of forest tree species and soil diversities was compared between the periods of dominant sulphur deposition (1985–1994) and the period of regional environmental change (2003–2012) in the Czech Republic (Central Europe; 78 866 km2; 115–1602 m n.m.). Forest tree species and soil diversities were assessed using linear regression, discrimination analysis and geographically weighted regression including residue analysis. The effect of spatial differences of acid deposition on soil properties, though, decreased, still dependencies between the diversity of bedrock, soils and forest tree species increased significantly. Only 12.9 % of forests in the territory of the CR have optimum tree species diversity. The total of 65.9 % of forest require highly or moderately urgent transformation. An increase in spatial dependencies between soil and tree species diversities confirms the importance of site differentiation in forest transformation.

Quantitative biomonitoring of nitrogen deposition with TONIS (Total N Input Biomonitoring System)

Monitoring of air pollutants is an important instrument to detect threats and to observe temporal trends of emissions. Determining the spatial distribution of oxidized and reduced N species via modelling requires sufficient knowledge about innumerous small sources from traffic, settlements and agriculture. Empirical studies are required to validate the model data but measurements of the total N deposition (e.g. micrometeorological measurements) are very expensive. Against this background, the TONIS, a new suitable technique which combines a biomonitoring with plants and technical measurements was developed. During 6 exposures between 2012 and 2016 at different polluted sites in Northwest Germany, TONIS accumulated between 17 and 25 kg N ha-1 yr^-1t. The results are feasible compared to simultaneously measured NH₃ and NO₂ concentration and bulk N deposition. At one site within a peat bog the accumulated N in TONIS was found to be in the range of total N deposition derived from a micrometeorological approach.

Even low to medium nitrogen deposition impacts vegetation of dry, coastal dunes around the Baltic Sea

Coastal dunes around the Baltic Sea have received small amounts of atmospheric nitrogen and are rather pristine ecosystems in this respect. In 19 investigated dune sites the atmospheric wet nitrogen deposition is 3-8kg Nha(-1)yr(-1). The nitrogen content of Cladonia portentosa appeared to be a suitable biomonitor of these low to medium deposition levels. Comparison with EMEP-deposition data showed that Cladonia reflects the deposition history of the last 3-6 years. With increasing nitrogen load, we observed a shift from lichen-rich short grass vegetation towards species-poor vegetation dominated by the tall graminoid Carex arenaria. Plant species richness per field site, however, does not decrease directly with these low to medium N deposition loads, but with change in vegetation composition. Critical loads for acidic, dry coastal dunes might be lower than previously thought, in the range of 4-6kg Nha(-1)yr(-1) wet deposition.

Critical loads and their exceedances at intensive forest monitoring sites in Europe

Intensive forest monitoring by means of harmonised methods has been conducted in Europe for more than a decade. Risks of atmospheric nitrogen and sulphur deposition are assessed by means of calculations of critical loads and their exceedances. In the present study throughfall and bulk deposition of nitrate (N-NO(3)), ammonium (N-NH(4)) and sulphate (S-SO(4)) show marked spatial patterns and temporal trends. In the period of observation (1999-2004), sulphate deposition on intensive monitoring plots decreased by about one quarter. This is in line with the reduction of S deposition by 70% since 1981 in Europe as a result of successful air pollution control politics under the Convention on Long-range Transboundary Air Pollution (CLRTAP). However, sulphate and especially nitrate and ammonium deposition were found to still exceed critical loads at many forest sites, indicating a continued need for further implementation of air pollution abatement strategies.

The essential oil qualitative and quantitative composition in the needles of Pinus sylvestris L. growing along industrial transects

The aim of this study was to evaluate composition of the essential oils in the needles of Pinus sylvestris growing in the areas affected by a cement factory (CF), and an oil refinery (OR). Volatile components of the needles were analyzed by GC and GC/MS. The most heavily polluted CF stand had significantly higher concentration of gamma-Terpinene, Caryophyllene oxide in the current-year needles, while higher concentration of delta-3-Carene, alpha-Terpinene, gamma-Terpinene and Terpinolene was documented for 1-year-old needles. The most heavily polluted OR stand had a significantly higher concentration of Sabinene+beta-Pinene, 1-epi-Cubenol in the current-year needles and a significantly higher concentration of Camphene, Sabinene+beta-Pinene, Myrcene, alpha-Cadinene, 1-epi-Cubenol in the 1-year-old needles than the least polluted site. Along transects an increase in the amount of some diterpenes and a decrease in the components of the shorter chain essential oils was observed. These effects could be at least partially attributed to SO(2).

Low cost measurements of nitrogen and sulphur dry deposition velocities at a semi-alpine site: gradient measurements and a comparison with deposition model estimates

The conditional time averaged gradient method was used to measure air-surface exchange of nitrogen and sulphur compounds at a semi-alpine site in Southern Norway. Dry deposition velocities were then obtained from the bi-weekly concentration gradient measurements. Annual deposition velocities were found to be 1.4, 11.8 and 4.0 mm s(-1) for NH3, HNO3 and SO2, respectively, if all data were included, and to be 10.8, 11.8 and 13.0 mm s(-1), respectively, if only positive values were included. Measured deposition velocities were compared to two sets of values estimated from a big-leaf dry deposition module applying to two different land types (short grass and forbs, and tundra), driven by measured micrometeorological parameters. The deposition module gives reasonable values for this site throughout the year, but does not reproduce the large variability as shown in the measured data. No apparent seasonal variations were found from either measurements or module estimates due to the very low productivity of the studied area.

Bidirectional ammonia exchange above a mixed coniferous forest

Two canopy compensation point models were used to study the bidirectional exchange of ammonia over a mixed coniferous forest subjected to high nitrogen deposition. The models were tested for 16 time series, average fluxes of which ranged between -270 and +1 ng m(-2)s(-1). The static model consisted of a bidirectional stomatal flux and a unidirectional cuticular flux component. The dynamic model also allowed for desorption of ammonia from the leaf surface and took into account ammonia fluxes from precedent periods. The apoplastic ammonium/hydrogen ion ratio (Gamma), which was derived to estimate the stomatal compensation point (chi(s)), amounted to 3300 in spring and 1375 during the summer/autumn. Empirical descriptions for cuticular resistances (R(w)) in the static model, developed as a function of micrometeorological conditions and codeposition effects, failed to reproduce the measured fluxes. A better match with measurements was obtained using the dynamic model, which succeeded in simulating net-emission during the daytime.

Multivariate statistics as means of tracking atmospheric pollution trends in Western Poland

This study was carried out over a period of 4 years (2002-2005) at 2 sites located in western Poland differing as regards to human impact by analysis of chemical composition of bulk precipitation. The aim of the study was to determine the sources of pollutions and assess their quantitative contribution to the bulk precipitation composition and to analyse long term-changes in the chemical quality of precipitation. Based on this information the possible transboundary impacts of pollution were also determined. The samples were characterized by determining the values of pH, electrolytic conductivity and concentration levels of Cl(-), F(-), SO(4)(2-), NO(3)(-), Na(+), K(+), Mg(2+), Ca(2+) and NH(4)(+). Analytical measurements were connected with application of principal component regression (PCR) and time series analysis (TS). Based on PCR results three major sources of pollutants in central part of Poland have been identified and quantitatively assessed as follows: "combined" (Poznań - 31%, WNP - 32%), "soil-particulates" (Poznań - 2%, WNP - 26%), "anthropogenic-fossil fuels" (Poznań - 43%, WNP - 23%). Time series analysis enabled discovering 12-month time cycle for NO(3)(-), NH(4)(+), Cl(-), F(-) and SO(4)(2-) in average monthly concentration values in bulk precipitation collected in Wielkopolski National Park. Seasonal variation in the emission of precursors of NO(3)(-) and NH(4)(+) was caused by changes in intensity of fertilizer application in agriculture and automobile exhaust emissions. Decreasing trend was visible for sulphates, nitrates, chlorides and fluorides which is an important indication of the acid rain reduction in the ecologically protected area and in Poznań.

Fluxes of oxidised and reduced nitrogen above a mixed coniferous forest exposed to various nitrogen emission sources

Concentrations of nitrogen gases (NH(3), NO(2), NO, HONO and HNO(3)) and particles (pNH(4) and pNO(3)) were measured over a mixed coniferous forest impacted by high nitrogen loads. Nitrogen dioxide (NO(2)) represented the main nitrogen form, followed by nitric oxide (NO) and ammonia (NH(3)). A combination of gradient method (NH(3) and NO(x)) and resistance modelling techniques (HNO(3), HONO, pNH(4) and pNO(3)) was used to calculate dry deposition of nitrogen compounds. Net flux of NH(3) amounted to -64 ng N m(-2) s(-1) over the measuring period. Net fluxes of NO(x) were upward (8.5 ng N m(-2) s(-1)) with highest emission in the morning. Fluxes of other gases or aerosols substantially contributed to dry deposition. Total nitrogen deposition was estimated at -48 kg N ha(-1) yr(-1) and consisted for almost 80% of NH(x). Comparison of throughfall nitrogen with total deposition suggested substantial uptake of reduced N (+/-15 kg N ha(-1) yr(-1)) within the canopy.

Practical considerations for addressing uncertainties in monitoring bulk deposition

The assessment of the deposition of both wet (rain and cloud) and dry sedimenting particles is a prerequisite for estimating element fluxes in ecosystem research. Many nations and institutions operate deposition networks using different types of sampler. However, these samplers have rarely been characterized with respect to their sink properties. Major errors in assessing bulk deposition can result from poor sampling properties and defective sampling strategies. Relevant properties are: sampler geometry and material, in particular the shape of the rim; sink properties for gases and aerosols; and microbial transformations of the collected samples. An adequate number of replicates allows the identification of samples which are contaminated, in particular by bird droppings. The paper discusses physical and chemical properties of the samplers themselves. The dependence of measurement accuracy on the number of replicates and the sampling area exposed is discussed. Recommendations are given for sampling strategies, and for making corrections and substitution of missing data.