Health & Environmental Research Online (HERO)


ISA NOxSOxPM Ecology (2018)

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The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Experimentally increased water and nitrogen affect root production and vertical allocation of an old-field grassland

Authors: Xu, Z; Ren, H; Li, MaiHe; Brunner, I; Yin, J; Liu, H; Kong, D; Lu, XTao; Sun, Tao; Cai, J; Wang, R; Zhang, Y; He, P; Han, X; Wan, S; Jiang, Y (2017) Plant and Soil 412:369-380. HERO ID: 3845563

[Less] Background and aims Evidence for impacts of environmental changes on belowground net primary production . . . [More] Background and aims Evidence for impacts of environmental changes on belowground net primary production (BNPP) from long-term experiments is rather scarce. We aimed to understand how long-term changes in water and nitrogen availability affect production and vertical allocation of roots in semi-arid grasslands and its consequence on carbon (C) and nitrogen (N) cycles.

Methods We investigated changes of BNPP and its vertical allocation along the soil profile to 40 cm in depth in response to simultaneous increases in water and N availability over 11 years in an old-field grassland in northern China.

Results Water addition increased BNPP in all soil layers (0-10 cm, 10-20 cm, and 20-40 cm), and enhanced the percentage BNPP in the upper soils but decreased that in 10-20 cm soil layer. Nitrogen addition decreased BNPP in 10-20 cm and 20-40 cm soil layers as well as total BNPP in 0-40 cm, and increased the percentage BNPP in the upper soil layer but decreased that in 10-20 cm soil layer. Water addition increased soil total C and N concentrations in 0-10 cm and 10-20 cm soil layers, while N addition only marginally decreased soil C:N ratio in 0-10 cm and 20-40 cm soil layers. Both soil total N concentration and soil C: N ratio were closely related to BNPP.

Conclusions Our results highlight the importance of environmental factors, especially water availability, in determining BNPP, and in turn controlling soil nutrient accumulation in semi-arid grasslands, although the specific mechanisms remain unclear. The projected increase in precipitation in those semi-arid grasslands would enhance soil C and N sequestration. The increased allocation of BNPP in upper soils with long-term precipitation increment and N deposition may accelerate thecycles of C and N in these ecosystems, and thus increase the risk of soil C and N loss.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Response of alpine soils to nitrogen addition on the Tibetan Plateau: A meta-analysis

Authors: Fu, G; Shen, ZXi (2017) Applied Soil Ecology 114:99-104. HERO ID: 3848826

[Less] A meta-analysis approach was used to identify general tendency of alpine soil responses to nitrogen . . . [More] A meta-analysis approach was used to identify general tendency of alpine soil responses to nitrogen fertilizer on the Tibetan Plateau. Nitrogen addition increased ammonium nitrogen (NH4(+)) and nitrate nitrogen (NO3-), but decreased pH. Effects of nitrogen addition on soil organic carbon (SOC), total nitrogen (TN), C:N ratio and pH differed among forests, alpine meadows and alpine steppes. Effects of nitrogen addition on NH4+, NO3-, soil microbial biomass carbon (MBC) and nitrogen (MBN) differed between alpine meadows and forests. Effects of NH4NO3 addition on SOC, TN, C:N ratio, NH4+, NO3-, MBC and pH differed with those of urea addition. The effect of nitrogen addition on pH was negatively correlated with mean annual temperature and mean annual precipitation. Soil conditions in control plots were positively correlated with the effect of nitrogen addition on pH, but negatively correlated with the effect of nitrogen addition on TN. Nitrogen addition rate was correlated with the effect of nitrogen fertilizer on NO3- and pH. Nitrogen addition duration was positively correlated with the effect of nitrogen fertilizer on pH. Therefore, effects of nitrogen fertilizers on alpine soils varied with nitrogen fertilizer types; climatic warming and precipitation change regulated effects of nitrogen fertilizer on alpine soils; and response of alpine soils to nitrogen addition may depend on initial soil conditions, rate and duration of nitrogen addition on the Tibetan Plateau. (C) 2017 Elsevier B.V. All rights reserved.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Nitrogen addition increases the production and turnover of the lower-order roots but not of the higher-order roots of Bothriochloa ischaemum

Authors: Wang, G; Xue, Sha; Liu, F; Liu, G (2017) Plant and Soil 415:423-434. HERO ID: 3857758

[Less] Global nitrogen deposition alters grassland ecosystems. Whether added nitrogen changes root production . . . [More] Global nitrogen deposition alters grassland ecosystems. Whether added nitrogen changes root production and turnover by root orders is unclear.

We compared the root dynamics across four root orders of Bothriochloa ischaemum treated with nitrogen addition (0-10 g N m(-2) year(-1)).

The higher order roots exhibited lower production, turnover, number, length, and biomass, indicating a hierarchical system of B. ischaemum. At whole root system level, nitrogen addition increased length production, biomass production and turnover. At root order level, nitrogen addition increased length production, biomass production, and turnover of the first two order roots but not of the third- and fourth-order roots. Nitrogen addition reduced root biomass, and the belowground to aboveground biomass ratio, supporting the functional equilibrium hypothesis. The increased root production, turnover and decreased root number, length and biomass were mainly attributed to the increasing ammonium and nitrate nitrogen.

Nitrogen addition increased the length production (7-30%), biomass production (10-34%) and turnover (8-35%) of the first two order roots but not of the higher order roots compared with the control pots. The discrepancy in root characteristics and their responses to nitrogen availability among root orders should be considered in establishing root dynamic models.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Nitrogen subsidies in glacial meltwaters have altered planktonic diatom communities in lakes of the US Rocky Mountains for at least a century

Authors: Slemmons, KEH; Rodgers, ML; Stone, JR; Saros, JE (2017) HERO ID: 4123292

[Less] We examined sedimentary diatom profiles from alpine lakes in the US Rocky Mountains to assess when glacially . . . [More] We examined sedimentary diatom profiles from alpine lakes in the US Rocky Mountains to assess when glacially fed lakes started receiving nitrogen subsidies and whether that timing varies across regions. We focused on lake sediment cores from Glacier National Park and compared them to previously published work from the Greater Yellowstone Ecosystem. The only contemporary feature of these glacially fed lakes that differs from snowmelt-fed lakes is nitrate concentration, with glacially fed lakes having about 40 times higher nitrogen than snow-fed lakes; lake thermal structure and temperatures do not differ between lake types. Increases in Asterionella formosa, a strong indicator of nitrogen enrichment, occurred much earlier in glacially fed compared to snow-fed lakes across both regions. Responses to nitrogen enrichment in glacially fed lakes started at least a century ago, and in some cases, many centuries ago, whereas they occurred after 1970 in the snow-fed lakes. Furthermore, diatom assemblages in glacially fed lakes showed declines in species richness over time and greater community turnover compared to snow-fed lakes. Multiple lines of evidence indicate that throughout the late Holocene glacially fed lakes in both regions of the Rocky Mountains have followed different ecological trajectories than snow-fed lakes as a result of increasing nitrogen concentrations.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Altered food-web dynamics under increased nitrogen load in phosphorus deficient lakes

Authors: Trommer, G; Poxleitner, M; Lorenz, P; Bitzilekis, E; Gogaladze, A; Schultes, S; Stibor, H (2017) HERO ID: 4126548

[Less] Atmospheric nitrogen deposition predominantly influences ecosystems by shifting their available nutrient . . . [More] Atmospheric nitrogen deposition predominantly influences ecosystems by shifting their available nutrient budgets towards excess nitrogen conditions. In temperate lakes nitrogen is often naturally in excess and phosphorus is deficient, when compared with the optimal Redfield ratio of 16:1. To investigate effects of future increasing nitrogen conditions on lake plankton communities, we performed mesocosm experiments in three different nitrogen rich lakes, all characterised by high nitrogen to phosphorus ratios. In order to determine functional responses to increased nitrogen loading, we conducted six nitrogen fertilization treatments. Nitrogen fertilization was based upon existing nitrate and ammonium concentrations in natural wet deposition and multiple loadings of these concentrations. Despite the initial conditions of excess nitrogen, removal of additional nitrogen by the plankton community was observed in all of the lakes. In one lake, an increasing phosphorus limitation became visible in seston stoichiometry. Over all of the lakes and within each lake's experimental nitrogen gradient, we found evidence for decreased mesozooplankton due to nitrogen enrichment. The negative responses of mesozooplankton to N enrichment were mainly restricted to cladocerans and nauplii. The results indicate that nitrogen enrichment within the magnitudes of projected future atmospheric nitrogen depositions may lead to a long-term reduction of mesozooplankton in phosphorus deficient lakes. The transfer of nitrogen enrichment effects on lower food-web dynamics could have consequences for higher trophic levels, such as fish.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Particulate matter accumulation - further differences between native Prunus padus and non-native P.serotina

Authors: Popek, R; Lukowski, A; Karolewski, P (2017) HERO ID: 4172395

[Less] Particulate matter (PM) is one of the most harmful inhaled pollutants. Where pollutants have been emitted . . . [More] Particulate matter (PM) is one of the most harmful inhaled pollutants. Where pollutants have been emitted into the atmosphere, the most effective method for cleaning the air is through phytoremediation, whereby plants act as biological filters. PM has a negative impact on plants, but knowledge of PM effects on the photosynthetic apparatus is limited. In European forests, species of the genus Prunus L. play a key role in the composition of the forest understory and urban as well as industrial plantings. Shrubs of the native P. padus L. and closely-related invasive alien P. serotina Ehrh. are particularly widespread. Thus, both are good model species in which to study the impact of PM pollution.

The aim of this study was to assess the accumulation of PM in the context of leaf morphology and amount of epicuticular waxes on foliage, and the efficiency of the photosynthetic apparatus of P. padus and P. serotina. The study was conducted under controlled conditions using two variants of dust, cement and roadside PM. In addition, we analyzed the absorption of dust by leaves dividing it into three fractions by size (10-100 mu m, 2.5-10 mu m and 0.2-2.5 mu m). Results showed that both P. padus and P. serotina accumulate PM mostly on the surface of their leaves (SPM), rather than in the wax layer (WPM). P. padus accumulated higher amounts of PM than did P. serotina. The higher presence of PM on leaves of P. padus resulted in a reduction of the efficiency of the photosynthetic apparatus, manifested by lower rates of photosynthesis and chlorophyll a fluorescence, coinciding with an increased stomatal resistance. A strong negative correlation was found between the amount of PM accumulation and the efficiency of the photosynthetic apparatus in P. padus, but not in P. serotina. We have concluded that alien P. serotina is more tolerant to the conditions of stress caused by PM pollution than is the native P. padus, which may partly explain its success in the invasion in Europe.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Traceable measurements and calibration: a primer on uncertainty analysis

Authors: Csavina, J; Roberti, JA; Taylor, JR; Loescher, HW (2017) Ecosphere 8. HERO ID: 4284796

[Less] Describing the quality of measurements is necessary to understand the level of confidence in any observation. . . . [More] Describing the quality of measurements is necessary to understand the level of confidence in any observation. Accuracy, precision, trueness, repeatability, reproducibility, and uncertainty are all used to describe quality of measurement, but the terms are inconsistently defined and measured and thus easily misunderstood. One purpose of quality parameters is for the comparison of observations, but when dissimilar methods for estimating quality terms are utilized, a comparison is misrepresented. A standardized approach to estimating uncertainty provides a basis for meeting measurement requirements and providing a level of confidence for observations. Here, we show the approach used by the National Ecological Observatory Network to estimate uncertainty of the calibration processes and measurements illustrated with an example of uncertainty assessment on a temperature sensor. Detailing the approach for uncertainty assessment provides the transparency necessary for network science and allows for the approach to be adopted in the scientific community. Reporting uncertainty with all measurements needs to become consistent and commonplace across disciplines.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Symbiosis revisited: phosphorus and acid buffering stimulate N-2 fixation but not Sphagnum growth

Authors: van Den Elzen, Eva; Kox, MAR; Harpenslager, SF; Hensgens, G; Fritz, C; Jetten, MSM; Ettwig, KF; Lamers, LPM (2017) Biogeosciences 14:1111-1122. HERO ID: 3843580

[Less] In pristine Sphagnum-dominated peatlands, (di) nitrogen (N-2) fixing (diazotrophic) microbial communities . . . [More] In pristine Sphagnum-dominated peatlands, (di) nitrogen (N-2) fixing (diazotrophic) microbial communities associated with Sphagnum mosses contribute substantially to the total nitrogen input, increasing carbon sequestration. The rates of symbiotic nitrogen fixation reported for Sphagnum peatlands, are, however, highly variable, and experimental work on regulating factors that can mechanistically explain this variation is largely lacking. For two common fen species (Sphagnum palustre and S. squarrosum) from a high nitrogen deposition area (25 kg N ha(-1) yr(-1)), we found that diazotrophic activity (as measured by N-15-15(2) labeling) was still present at a rate of 40 nmol N gDW(-1) h(-1). This was surprising, given that nitrogen fixation is a costly process. We tested the effects of phosphorus availability and buffering capacity by bicarbonate-rich water, mimicking a field situation in fens with stronger groundwater or surface water influence, as potential regulators of nitrogen fixation rates and Sphagnum performance. We expected that the addition of phosphorus, being a limiting nutrient, would stimulate both diazotrophic activity and Sphagnum growth. We indeed found that nitrogen fixation rates were doubled. Plant performance, in contrast, did not increase. Raised bicarbonate levels also enhanced nitrogen fixation, but had a strong negative impact on Sphagnum performance. These results explain the higher nitrogen fixation rates reported for minerotrophic and more nutrient-rich peatlands. In addition, nitrogen fixation was found to strongly depend on light, with rates 10 times higher in light conditions suggesting high reliance on phototrophic organisms for carbon. The contrasting effects of phosphorus and bicarbonate on Sphagnum spp. and their diazotrophic communities reveal strong differences in the optimal niche for both partners with respect to conditions and resources. This suggests a trade-off for the symbiosis of nitrogen fixing microorganisms with their Sphagnum hosts, in which a sheltered environment apparently outweighs the less favorable environmental conditions. We conclude that microbial activity is still nitrogen limited under eutrophic conditions because dissolved nitrogen is being monopolized by Sphagnum. Moreover, the fact that diazotrophic activity can significantly be upregulated by increased phosphorus addition and acid buffering, while Sphagnum spp. do not benefit, reveals remarkable differences in optimal conditions for both symbiotic partners and calls into question the regulation of nitrogen fixation by Sphagnum under these eutrophic conditions. The high nitrogen fixation rates result in high additional nitrogen loading of 6 kg ha(-1) yr(-1) on top of the high nitrogen deposition in these ecosystems.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Species-specific phenological responses to long-term nitrogen fertilization in an alpine meadow

Authors: Yin, T-F; Zheng, L-L, Cao, G-M,; Song, M-H; Yu, F-H (2017) Journal of Plant Ecology 10:301-309. HERO ID: 3848393

[Less] Aims

Long-term nitrogen (N) fertilization has profound impacts on community structure and . . .
[More] Aims



Long-term nitrogen (N) fertilization has profound impacts on community structure and ecosystem function, but little is known about its effects on plant phenology. Furthermore, no published study has examined effects of N chemical forms on plant phenology.



Methods



In an alpine meadow on the Tibetan Plateau, we monitored reproductive phenology of six common plant species after 8 years of fertilization with different N chemical forms (addition of 7.5 g N m(-2) yr(-1) in the forms of ammonium, nitrate and ammonium nitrate), with no N addition as the control.



Important Findings



Eight years of N fertilization affected plant reproductive phenology, and such effects depended on the species, N form and phenological phase. Fertilization with ammonium generally delayed, advanced or did not change flowering and fruiting phases of the alpine plants. Furthermore, fertilization with ammonium affected the temporal dispersion of reproductive phenology among the six species, especially among the late-flowering species. This could reduce the overlap of flowering and fruiting and increase phenological complementarity. Fertilization with nitrate only delayed the senescence phase of Elymus nutans, and fertilization with ammonium nitrate did not affect reproductive phenology of the six alpine plants. N fertilization with any form increased the overlap in senescence among the six species. We conclude that long-term N fertilization can cause shifts in plant phenology and such effects depend on N chemical forms. Our results also suggest that phenological complementarity could be a mechanism underlying resource partitioning and thus species coexistence in the face of changing N availability with different chemical forms.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Description and evaluation of the Community Multiscale Air Quality (CMAQ) modeling system version 5.1

Authors: Appel, KW; Napelenok, SL; Foley, KM; Pye, HOT; Hogrefe, C; Luecken, DJ; Bash, JO; Roselle, SJ; Pleim, JE; Foroutan, H; Hutzell, WT; Pouliot, GA; Sarwar, G; Fahey, KM; Gantt, B; Gilliam, RC; Heath, NK; Kang, D; Mathur, R; Schwede, DB; Spero, TL; Wong, DC; Young, JO (2017) Geoscientific Model Development 10:1703-1732. HERO ID: 3846692

[Less] The Community Multiscale Air Quality (CMAQ) model is a comprehensive multipollutant air quality modeling . . . [More] The Community Multiscale Air Quality (CMAQ) model is a comprehensive multipollutant air quality modeling system developed and maintained by the US Environmental Protection Agency's (EPA) Office of Research and Development (ORD). Recently, version 5.1 of the CMAQ model (v5.1) was released to the public, incorporating a large number of science updates and extended capabilities over the previous release version of the model (v5.0.2). These updates include the following: improvements in the meteorological calculations in both CMAQ and the Weather Research and Forecast (WRF) model used to provide meteorological fields to CMAQ, updates to the gas and aerosol chemistry, revisions to the calculations of clouds and photolysis, and improvements to the dry and wet deposition in the model. Sensitivity simulations isolating several of the major updates to the modeling system show that changes to the meteorological calculations result in enhanced afternoon and early evening mixing in the model, periods when the model historically underestimates mixing. This enhanced mixing results in higher ozone (O-3) mixing ratios on average due to reduced NO titration, and lower fine particulate matter (PM2.5) concentrations due to greater dilution of primary pollutants (e.g., elemental and organic carbon). Updates to the clouds and photolysis calculations greatly improve consistency between the WRF and CMAQ models and result in generally higher O-3 mixing ratios, primarily due to reduced cloudiness and attenuation of photolysis in the model. Updates to the aerosol chemistry result in higher secondary organic aerosol (SOA) concentrations in the summer, thereby reducing summertime PM2.5 bias (PM2.5 is typically underestimated by CMAQ in the summer), while updates to the gas chemistry result in slightly higher O-3 and PM2.5 on average in January and July. Overall, the seasonal variation in simulated PM2.5 generally improves in CMAQv5.1 (when considering all model updates), as simulated PM2.5 concentrations decrease in the winter (when PM2.5 is generally overestimated by CMAQ) and increase in the summer (when PM2.5 is generally underestimated by CMAQ). Ozone mixing ratios are higher on average with v5.1 vs. v5.0.2, resulting in higher O-3 mean bias, as O-3 tends to be overestimated by CMAQ throughout most of the year (especially at locations where the observed O-3 is low); however, O-3 correlation is largely improved with v5.1. Sensitivity simulations for several hypothetical emission reduction scenarios show that v5.1 tends to be slightly more responsive to reductions in NOx (NO + NO2), VOC and SOx (SO2 + SO4) emissions than v5.0.2, representing an improvement as previous studies have shown CMAQ to underestimate the observed reduction in O-3 due to large, widespread reductions in observed emissions.