Biotechnological production of glycosides is an economically competitive manufacturing alternative to classical chemical synthesis. Due to continuous improvement in production, glycosides can now be ...used in low‐cost products by various industries. However, many production systems still suffer from low yields. Directed evolution, coupled with a suitable screening method, can tackle this challenge. We generated glycosyltransferase mutants through error‐prone‐PCR and screened the library using a small‐scale whole‐cell biotransformation system to identify highly productive strains. The screening of only 176 colonies yielded three putative candidates. Detailed analysis revealed that the reason for the increase in product titer was mainly due to different expression effects of the mutant genes rather than improved enzyme kinetics. An up to 60‐fold increase in whole‐cell product quantity was achieved. Therefore, in addition to the quality of the mutant library, an efficient and stable expression system is crucial to achieve high concentrations of active enzyme and product, as formation of inclusion bodies and other inactive forms of the biocatalyst reduces productivity.
The production yield of geranyl glucoside in a whole‐cell biotransformation system was improved up to 60‐fold by directed evolution. However, the increase in product titer was mainly caused by the adaptation of the expression system rather than by increasing the specific catalytic activity of the enzyme involved. The efficient and stable expression of the biocatalyst was crucial in this approach.
There is a long history in environmental sciences to investigate and understand the fate of chemicals in the environment. For pesticides, this has led to systematic assessments of compounds by both ...academic and regulatory bodies, particularly for soil and water. As we show here, in recent years, there is an increasing interest in the potential presence of pesticide residues in air and related exposure risks. Based on a literature review for the years 2002–2022, we find a growing number of air monitoring studies with an average of 6.7 studies/year since 2020, with passive sampling methods contributing significantly to this rise. Most studies are concentrated in Europe and North America, with France leading in the number of monitoring studies. However, due to a lack of harmonization, and thus, the use of diverse methods and approaches, it remains challenging to derive potential exposure risks, to assess data quality of studies, and to compare datasets. In this perspective, we focus on current and emerging trends of different air monitoring approaches and highlight how they influence the interpretation of data. To improve the comparability and utility of data, and to ensure that air monitorings meet certain quality requirements, we propose a path forward, including: (1) Standardization and harmonization of methods: Adopting well-characterized and widely applied methods from air quality research as a basis for standardizing pesticide monitoring, with a clear distinction between relevant exposure and total air concentrations. (2) Tiered approach for monitoring programs: A dynamic concept where initial passive sampling identifies potential exposure risks, followed by active sampling for quantitative data, and, if necessary, extensive monitoring programs. This approach balances the need for detailed data with resource constraints. (3) Data interpretation and transparency: Public availability of data and clear reporting of methods, analysis, and uncertainties are crucial for the credibility and utility of monitoring studies. Overall, we see that harmonization of standards is critical for assessing exposure risks from pesticides in air and for informing regulatory decisions and mitigation strategies. Collaboration with the air quality and atmospheric research community is strongly recommended to leverage existing expertise in sampling, analysis, and data interpretation.
Volcanoes are a natural source of several reactive gases (e.g., sulfur and halogen containing species) and nonreactive gases (e.g., carbon dioxide) to the atmosphere. The relative abundance of carbon ...and sulfur in volcanic gas as well as the total sulfur dioxide emission rate from a volcanic vent are established parameters in current volcano-monitoring strategies, and they oftentimes allow insights into subsurface processes. However, chemical reactions involving halogens are thought to have local to regional impact on the atmospheric chemistry around passively degassing volcanoes. In this study we demonstrate the successful deployment of a multirotor UAV (quadcopter) system with custom-made lightweight payloads for the compositional analysis and gas flux estimation of volcanic plumes. The various applications and their potential are presented and discussed in example studies at three volcanoes encompassing flight heights of 450 to 3300 m and various states of volcanic activity. Field applications were performed at Stromboli volcano (Italy), Turrialba volcano (Costa Rica) and Masaya volcano (Nicaragua). Two in situ gas-measuring systems adapted for autonomous airborne measurements, based on electrochemical and optical detection principles, as well as an airborne sampling unit, are introduced. We show volcanic gas composition results including abundances of CO2, SO2 and halogen species. The new instrumental setups were compared with established instruments during ground-based measurements at Masaya volcano, which resulted in CO2 ∕ SO2 ratios of 3.6 ± 0.4. For total SO2 flux estimations a small differential optical absorption spectroscopy (DOAS) system measured SO2 column amounts on transversal flights below the plume at Turrialba volcano, giving 1776 ± 1108 T d−1 and 1616 ± 1007 T d−1 of SO2 during two traverses. At Stromboli volcano, elevated CO2 ∕ SO2 ratios were observed at spatial and temporal proximity to explosions by airborne in situ measurements. Reactive bromine to sulfur ratios of 0.19 × 10−4 to 9.8 × 10−4 were measured in situ in the plume of Stromboli volcano, downwind of the vent.
Volcanoes are a significant halogen source to the atmosphere. After water, carbon dioxide and sulfur compounds, halogens are often the most abundant gases in volcanic plumes. In the past, less ...attention was given to the heavy halogens bromine and iodine. However, the discovery of bromine monoxide (BrO) in volcanic plumes led to new interest especially in volcanic bromine chemistry and its impact on atmospheric processes. The BrO detection came along with advances in volcanic remote sensing techniques, in particular, robust DOAS applications and the possibility of continuous measurements by automated instruments located at safe distances from the volcano. As one of the consequences, the volcanic community developed an increased interest to use BrO/SO 2 ratios as a potential tracer of volcanic activity. BrO is a secondary volcanic gas, but the only bromine species in volcanic plumes, which has been measured by remote sensing techniques today. For a better understanding on bromine chemistry in volcanic plumes and to gain information on the original amount of emitted bromine by only measuring BrO, additional techniques were developed (alkaline traps, diffusion denuders) and adapted for drone-based sampling to determine further gaseous bromine species (i.e. Br 2 , HBr, HOBr, interhalogens) at various plume ages. Additionally models of plume-atmospheric chemistry were developed to help the interpretation of field-measurements. Model studies simulating plume conditions indicated that a complex atmospheric chemistry mechanism transforms emitted HBr into BrO and other reactive bromine species such as BrOH, Br 2 , BrCl, BrONO 2 or BrNO 2. To reproduce the very rapid formation of BrO observed in volcanic plumes, the volcanic emission input to the (low-temperature) plume chemistry models also needs to consider the high-temperature near-vent plume conditions, as represented by thermodynamic models. The formation of BrO and other reactive bromine species depend not only on the amount of bromine emitted but also on plume mixing processes, relative humidity, and aerosol particle acidity. However, uncertainties remain in the validation of the plume chemistry models by a lack of field-measurements. This review provides a comprehensive summary on volcanic bromine data of the last 15 years achieved from established and cutting edge measurement techniques as well as their treatment and interpretation in recent model experiments. It points out controversially discussed relation of bromine degassing to volcanic activity and puts a light on remaining uncertainties.
Volcanic emissions are a source of halogens in the
atmosphere. Rapid reactions convert the initially emitted hydrogen halides
(HCl, HBr, and HI) into reactive species such as BrO, Br2, BrCl, ClO, ...OClO, and
IO. The activation reaction mechanisms in the plume consume ozone (O3),
which is entrained by ambient air that is mixed into the plume. In this study, we present
observations of the oxidation of bromine, chlorine, and iodine during the
first 11 min following emission, examining the plume from Santiago crater of the
Masaya volcano in Nicaragua. Two field campaigns were conducted: one in July
2016 and one in September 2016. The sum of the reactive species of each halogen was
determined by gas diffusion denuder sampling followed by gas chromatography–mass spectrometry (GC-MS) analysis,
whereas the total halogens and sulfur concentrations were obtained by
alkaline trap sampling with subsequent ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS) measurements. Both
ground and airborne sampling with an unoccupied aerial vehicle (carrying a
denuder sampler in combination with an electrochemical SO2 sensor) were
conducted at varying distances from the crater rim. The in situ measurements
were accompanied by remote sensing observations (differential optical absorption spectroscopy; DOAS). The reactive
fraction of bromine increased from 0.20 ± 0.13 at the crater rim to
0.76 ± 0.26 at 2.8 km downwind, whereas chlorine showed an increase in
the reactive fraction from (2.7 ± 0.7) × 10−4 to
(11 ± 3) × 10−4 in the first 750 m. Additionally, a
reactive iodine fraction of 0.3 at the crater rim and 0.9 at 2.8 km downwind was
measured. No significant change in BrO / SO2 molar ratios was observed
with the estimated age of the observed plume ranging from 1.4 to 11.1 min. This study presents a large complementary data set of different halogen
compounds at Masaya volcano that allowed for the quantification of reactive
bromine in the plume of Masaya volcano at different plume ages. With the
observed field data, a chemistry box model (Chemistry As A Boxmodel Application
Module Efficiently Calculating the Chemistry of the Atmosphere; CAABA/MECCA) allowed us to
reproduce the observed trend in the ratio of the reactive bromine to total
bromine ratio. An observed contribution of BrO to the reactive bromine
fraction of about 10 % was reproduced in the first few minutes of the
model run.
A multi-rotor drone has been adapted for studies of volcanic gas plumes. This adaptation includes improved capacity for high-altitude and long-range, real-time SO.sub.2 concentration monitoring, ...long-range manual control, remotely activated bag sampling and plume speed measurement capability. The drone is capable of acting as a stable platform for various instrument configurations, including multi-component gas analysis system (MultiGAS) instruments for in situ measurements of SO.sub.2, H.sub.2 S, and CO.sub.2 concentrations in the gas plume and portable differential optical absorption spectrometer (MobileDOAS) instruments for spectroscopic measurement of total SO.sub.2 emission rate, remotely controlled gas sampling in bags and sampling with gas denuders for posterior analysis on the ground of isotopic composition and halogens.
Trends in Air Pollution in Europe, 2000-2019 Aas, Wenche; Fagerli, Hilde; Alastuey, Andres ...
Aerosol and Air Quality Research,
04/2024, Letnik:
24, Številka:
4
Journal Article
Recenzirano
Odprti dostop
This paper encompasses an assessment of air pollution trends in rural environments in Europe over the 2000-2019 period, benefiting from extensive long-term observational data from the EMEP monitoring ...network and EMEP MSC-W model computations. The trends in pollutant concentrations align with the decreasing emission patterns observed throughout Europe. Annual average concentrations of sulfur dioxide, particulate sulfate, and sulfur wet deposition have shown consistent declines of 3-4% annually since 2000. Similarly, oxidized nitrogen species have markedly decreased across Europe, with an annual reduction of 1.5-2% in nitrogen dioxide concentrations, total nitrate in the air, and oxidized nitrogen deposition. Notably, emission reductions and model predictions appear to slightly surpass the observed declines in sulfur and oxidized nitrogen, indicating a potential overestimation of reported emission reductions. Ammonia emissions have decreased less compared to other pollutants since 2000. Significant reductions in particulate ammonium have however, been achieved due to the impact of reductionsin SO_x and NO_x emissions. For ground level ozone, both the observed and modelled peak levels in summer show declining trends, although the observed decline is smaller than modelled. There have been substantial annual reductions of 1.8% and 2.4% in the concentrations of PM_(10) and PM_(2.5), respectively. Elemental carbon has seen a reduction of approximately 4.5% per year since 2000. A similar reduction for organic carbon is only seen in winter when primary anthropogenic sources dominate. The observed improvements in European air quality emphasize the importance of comprehensive legislations to mitigate emissions.
The long-range transport (LRT) of trace gases and aerosol particles plays an important role for the composition of the Amazonian rain forest atmosphere. Sulfate aerosols originate to a substantial ...extent from LRT sources and play an important role in the Amazonian atmosphere as strongly light-scattering particles and effective cloud condensation nuclei. The transatlantic transport of volcanic sulfur emissions from Africa has been considered as a source of particulate sulfate in the Amazon; however, direct observations have been lacking so far. This study provides observational evidence for the influence of emissions from the Nyamuragira–Nyiragongo volcanoes in Africa on Amazonian aerosol properties and atmospheric composition during September 2014. Comprehensive ground-based and airborne aerosol measurements together with satellite observations are used to investigate the volcanic event. Under the volcanic influence, hourly mean sulfate mass concentrations in the submicron size range reached up to 3.6 µg m−3 at the Amazon Tall Tower Observatory, the highest value ever reported in the Amazon region. The substantial sulfate injection increased the aerosol hygroscopicity with κ values up to 0.36, thus altering aerosol–cloud interactions over the rain forest. Airborne measurements and satellite data indicate that the transatlantic transport of volcanogenic aerosols occurred in two major volcanic plumes with a sulfate-enhanced layer between 4 and 5 km of altitude. This study demonstrates how African aerosol sources, such as volcanic sulfur emissions, can substantially affect the aerosol cycling and atmospheric processes in Amazonia.
Volcanic degassing provides important information for the assessment of volcanic hazards. Santa Ana and San Miguel are open vent volcanoes along the Central American Volcanic Arc–CAVA, where the ...magmatism, basaltic to dacitic, is related to the near-orthogonal convergence of the Caribbean Plate and the subducting Cocos Plate. Both volcanoes are the most active ones in El Salvador with recent eruptive events in October 2005 (Santa Ana) and December 2013 (San Miguel), but still not much data on gas composition and emission are available today. At each volcano, SO
2
emissions are regularly monitored using ground-based scanning Differential Optical Absorption Spectrometer (Scan-DOAS) instruments that are part of the global “Network for Observation of Volcanic and Atmospheric Change” (NOVAC). We used the data series from these NOVAC stations in order to retrieve SO
2
and minimum bromine emissions, which can be retrieved from the same spectral data for the period 2006–2020 at Santa Ana and 2008–2019 at San Miguel. However, BrO was not detected above the detection limit. SO
2
emission ranged from 10 to 7,760 t/d, and from 10 to 5,870 t/d for Santa Ana and San Miguel, respectively. In addition, the SO
2
emissions are complemented with
in situ
plume data collected during regular monitoring surveys (2018–2020) and two field campaigns in El Salvador (2019 and 2020). MultiGAS instruments recorded CO
2
, SO
2
, H
2
S and H
2
concentrations. We determined an average CO
2
/SO
2
ratio of 2.9 ± 0.6 when peak SO
2
concentration exceeded 15 ppmv at Santa Ana, while at San Miguel the CO
2
/SO
2
ratio was 7.4 ± 1.8, but SO
2
levels reached only up to 6.1 ppmv. Taking into account these ratios and the SO
2
emissions determined in this study, the resulting CO
2
emissions are about one order of magnitude higher than those determined so far for the two volcanoes. During the two field campaigns Raschig tubes (active alkaline trap) were used to collect plume samples which were analyzed with IC and ICP-MS to identify and quantify CO
2
, SO
2
, HCl, HF, and HBr. Additionally, also 1,3,5-trimethoxybenzene (TMB)-coated denuders were applied and subsequently analyzed by GC-MS to determine the sum of the reactive halogen species (RHS: including Cl
2
, Br
2
, interhalogens, hypohalous acids). The RHS to sulfur ratios at Santa Ana and San Miguel lie in the range of 10
−5
. Although no new insights could be gained regarding changes with volcanic activity, we present the most comprehensive gas geochemical data set of Santa Ana and San Miguel volcanoes, leading to a solid data baseline for future monitoring purposes at both volcanoes and their improved estimate of CO
2
, SO
2
and halogens emissions. Determining the reactive fraction of halogens is a first step towards a better understanding of their effects on the atmosphere.
Gas measurements using unmanned aerial vehicles, or drones, were undertaken at Turrialba volcano, Costa Rica, and Masaya volcano, Nicaragua, in 2016 and 2017. These two volcanoes are the largest ...time‐integrated sources of gas in the Central American Volcanic Arc, and both systems are currently extremely active with potential for sudden destabilization. We employed a series of miniaturized drone‐mounted instrumentation including a mini‐DOAS, two MultiGAS instruments, and an optical particle counter, supplemented by ground‐based measurements. Payloads were typically 1–1.5 kg and flight times were 10–15 min. The measurements were both accurate and precise due to the inherent sensitivity of the instrumentation and the high gas concentrations, which the drones were able to sample. The quality of data obtained by our drones was comparable to that obtained by our ground‐based measurements. At Turrialba in April 2017, we measured an average SO2 flux of 1,380 ± 280 T/day, CO2/SO2 of 6.5, and H2O/SO2 of 27.8. Using these values, we calculated a CO2 flux of 6,170 T/day and an H2O flux of 10,790 T/day. At Masaya in May 2017, the average SO2 flux was 1,560 ± 180 T/day, with CO2/SO2 of 3.9 and H2O/SO2 of 62.3, giving a mean CO2 flux of 4,150 T/day and mean H2O flux of 27,330 T/day. The elevated carbon and water fluxes and ratios are indicative of underlying magmas that are enriched in these components, resulting in the high levels of activity observed.
Key Points
This paper reports on new, lightweight instrumentation to measure volcanic gases from unmanned aerial vehicles (drones)
We measured gas ratios and gas fluxes from Turrialba and Masaya volcanoes in Central America
Our measurements show large degassing of these two systems, reflecting their currently elevated states of unrest
PDF
