Cavity ring-down spectroscopy (CRDS) is rapidly becoming an invaluable tool to measure hydrogen (δ²H) and oxygen (δ18O)
isotopic compositions in water, yet the long-term accuracy and precision of this technique remain relatively underreported.
Here, we critically evaluate one-year performance of CRDS δ²H and δ18O measurements at ETH Zurich, focusing on high
throughput (~200 samples per week) while maintaining required precision and accuracy for diverse scientific investigations.

The newly promulgated regulations under 40 CFR 63 Subpart O have undergone profound changes from their prior version, through the draft regulation issuance and public comment period, to the present day. Amy Moore with Trinity Consultants reviews these changes and discusses the unique challenges and array of compliance options available under the new requirements.

This study addressed the scarcity of NH3 measurements in urban Europe and the diverse monitoring protocols,
hindering direct data comparison. Sixty-nine datasets from Finland, France, Italy, Spain, and the UK across
various site types, including industrial (IND, 8), traffic (TR, 12), urban (UB, 22), suburban (SUB, 12), and
regional background (RB, 15), are analyzed to this study. Among these, 26 sites provided 5, or more, years of
data for time series analysis. Despite varied protocols, necessitating future harmonization, the average NH3

The Picarro SI2108 gas concentration analyzer can provide real-time monitoring of hydrogen chloride (HCl) at a parts-per-trillion (ppt) sensitivity for a variety of applications, including indoor and outdoor air quality, atmospheric science, and hazard assessment.

Fluxes of carbon dioxide (CO2) and methane (CH4) from hydroelectric and water supply reservoirs are
receiving increasing attention around the world with a number of research groups having undertaken measurements
of these emissions across a range of lakes and reservoirs located in different climates and landscapes.
The use of floating chambers (aka flux chambers) is the most common technique for direct
measurement of these fluxes. However, the relative performance of different measurement systems, especially

Microwave extraction–isotope ratio infrared spectroscopy (ME-IRIS): a novel technique for rapid extraction and in-line analysis of δ¹⁸ORATIONALE

Traditionally, stable isotope analysis of plant and soil water has been a technically challenging, labour-intensive and time-consuming process. Here we describe a rapid single-step technique which combines Microwave Extraction with Isotope Ratio Infrared Spectroscopy (ME-IRIS).

METHODS

Stable isotopes in the water molecule (2H or D and 18O), carbon, and nitrogen are useful tracers and integrators of processes in plant ecohydrological systems across scales. Over the last few years, there has been growing interest in regional to continental scale synthesis of stable isotope data with a view to elucidating biogeochemical and ecohydrological patterns. Published datasets from the humid tropics, however, are limited.

The ability to measure the stable isotopic composition of plant and soil waters, surface waters and ambient atmospheric vapor is essential to understanding an ecosystem's water budget, including how water cycles between the air, plants and the subsurface. With the advent of laser-based spectroscopy, e.g., Cavity Ring-Down Spectroscopy (CRDS), the isotopic analysis of waters has become increasingly cost-effective and prevalent, with comparable precision to conventional isotope ratio mass spectrometry methods.

The demanding precision of triple oxygen isotope (17O) measurements in water has restricted its measurement to dual-inlet mass spectrometry until the recent development of commercially available infrared-laser analyzers, including cavity ringdown spectrometers (CRDS). 17O is now increasingly measured by laboratories in order to better constrain the source and history of meteoric waters.

Premise
Water is the most limiting factor in dryland ecosystems, and plants are adapted to cope with this constraint. Particularly vulnerable are phreatophytic plants from groundwater-dependent ecosystems (GDEs) in regions that have to face water regime alterations due to the impacts of climate and land-use changes.

While litter traits have been used for decades to predict decomposition rates through the Leaf Economics
Spectrum (LES) acquisitive to conservative trait lens, litter trait and litter mixture effects on soil carbon (C)
priming effects (PE) is less known. To assess whether the LES can predict soil C PE during the decomposition of
litter mixtures from complex ecosystems, a 99-day incubation experiment was conducted. The experiment
involved soil and leaf litter from three Canadian riparian land uses (grasslands, deciduous agroforests, and

Ammonia (NH₃) is typically present at higher concentrations in indoor air (∼10–70 ppb) than in outdoor air (∼50 ppt to 5 ppb). It is the dominant neutralizer of acidic species in indoor environments, strongly influencing the partitioning of gaseous acidic and basic species to aerosols, surface films, and bulk water. We have measured NH₃ emissions from humans in an environmentally controlled chamber.

Rationale
The accuracy determined in the routine analysis of water isotopes (δ17O, δ18O, δ2H) using cavity ring-down spectroscopy is greatly affected by the memory effect (ME), a sample-to-sample carryover that biases measurements. This study aims to develop a simple method that rapidly removes the ME.

Indoor gas-phase radical sources are poorly understood but expected to be much different from outdoors. Several potential radical sources were measured in a windowless, light-emitting diode (LED)-lit room in a college athletic facility over a 2 week period. Alternating measurements between the room air and the supply air of the heating, ventilation, and air-conditioning system allowed an assessment of sources. Use of a chlorine-based cleaner was a source of several photolabile reactive chlorine compounds, including ClNO2 and Cl2.

In early 2020, an international team set out to investigate trade-wind cumulus clouds and their coupling to the large-scale circulation through the field campaign EUREC⁴A: ElUcidating the RolE of Clouds-Circulation Coupling in ClimAte. Focused on the western tropical Atlantic near Barbados, EUREC⁴A deployed a number of innovative observational strategies, including a large network of water isotopic measurements collectively known as EUREC⁴A-iso, to study the tropical shallow convective environment.

Atmospheric oxidation is dominated by the OH radical, although Cl atoms can play an important role under certain conditions.

Ambient 0.5 Hz hydrogen chloride (HCl) measurements were made in Canadian cities to investigate chlorine activation and constrain the tropospheric chlorine budget. Springtime HCl mixing ratios in a coastal city (St. John’s, NL) were up to 1200 parts per trillion by volume (pptv) with a median of 63 pptv and were consistently elevated during daytime. High time-resolution measurements allowed the attribution of events to general sources, including direct emissions. Most coastal HCl was related to sea-salt aerosol acid displacement (R1) and chlorine activation.

Reliable, sensitive, and widely available hydrogen chloride (HCl) measurements are important for understanding oxidation in many regions of the troposphere. We configured a commercial HCl cavity ring-down spectrometer (CRDS) for sampling HCl in the ambient atmosphere and developed validation techniques to characterize the measurement uncertainties. The CRDS makes fast, sensitive, and robust measurements of HCl in a high-finesse optical cavity coupled to a laser centred at 5739 cm−1.

Total gaseous chlorine (TCl_g) measurements can improve our understanding of unknown sources of Cl to the atmosphere. Existing techniques for measuring TCl_g have been limited to offline analysis of extracted filters and do not provide suitable temporal information on fast atmospheric process. We describe high time-resolution in-situ measurements of TCl_g by combusting ambient air over a heated platinum (Pt) substrate coupled to a cavity ring-down spectrometer (CRDS).

Coastal wetlands play an important role in nitrogen removal and are a vital blue carbon sink. The produced methane (CH₄) in coastal wetlands has been recently identified as a possible carbon source for denitrification process, providing a significant contribution to coastal nitrogen cycling. However, the in-situ correlation between CH₄ emissions and denitrification rate, as well as their coupling mechanism is still unclear.

Ventilation is of primary concern for maintaining healthy indoor air quality and reducing the spread of airborne infectious disease, including COVID-19. In addition to building-level guidelines, increased attention is being placed on room-level ventilation. However, for many universities and schools, ventilation data on a room-byroom basis are not available for classrooms and other key spaces. We present an overview of approaches for measuring ventilation along with their advantages and disadvantages.

The reduced economic and social activities during the Chinese Spring Festival provide a unique experiment to evaluate reductions in anthropogenic NH₃ emissions in China. However, quantifying this unique scenario is challenging as meteorology may mask the real changes in observed NH3 concentrations. Here, we applied a machine learning technique to decouple the effects of meteorology and confirmed that the real (deweathered) NH3 concentration dropped to a minimum during the Spring Festival in 2019 and 2020 at both urban (Beijing) and rural (Xianghe) sites on the North China Plain.

A general feature in the diurnal cycle of atmospheric ammonia (NH₃) concentrations is a morning spike that typically occurs around 07:00 to 10:00 (LST). Current hypotheses to explain this morning’s NH₃ increase remain elusive, and there is still no consensus whether traffic emissions are among the major sources of urban NH₃. Here, we confirmed that the NH₃ morning pulse in urban Beijing is a universal feature, with an annual occurrence frequency of 73.0% and a rapid growth rate (>20%) in winter.

Natural gas stoves in >40 million U.S. residences release methane (CH₄)--a potent greenhouse gas--through post-meter leaks and incomplete combustion. We quantified methane released in 53 homes during all phases of stove use: steady-state-off (appliance not in use), steady-state-on (during combustion), and transitory periods of ignition and extinguishment. We estimated that natural gas stoves emit 0.8−1.3% of the gas they use as unburned methane and that total U.S. stove emissions are 28.1 [95% confidence interval: 18.5, 41.2] Gg CH₄ year−1.

EPA Method T0-11A EPA outlines practices for measuring formaldehyde using the 4,2-DNPH denuder method, subsequent derivatization, and analysis by HPLC. While the DNPH method has been a stalwart of air quality monitoring for decades, it provides only time-averaged exposure estimates (typically 8 or 24-hour), requires offline analysis at third-party labs, and continues to experience suspected bias effects associated with ozone and water vapor. Because values are reported significantly post-hoc, formaldehyde also cannot be integrated into air quality monitoring forecasts.

Oxygen (¹⁸O/¹⁶O) and deuterium (D/H) isotopes are a widespread tool to trace physical and chemical processes in hydrology and biogeosciences. Precision and throughput are key parameters for water isotope analysis. Here, we will present two new methodologies for the Picarro L2130-i Cavity Ring-Down Spectroscopy (CRDS) water isotope analyzer that allow the user to increase the throughput with compromising data quality.

Spectroscopic instruments are becoming increasingly popular for measuring the isotopic composition and fluxes of a wide variety of gases in both field and laboratory experiments. The popularity of these instruments has created a need for automated multiplexers compatible with the equipment. While there are several such peripherals commercially available, they are currently limited to only a small number of samples (≤16), which is insufficient for some studies.

Agricultural peatlands are estimated to emit approximately one third of global greenhouse gas (GHG) emissions from croplands, but the temporal dynamics and controls of these emissions are poorly understood, particularly for nitrous oxide (N₂O). We used cavity ring-down spectroscopy and automated chambers in a drained agricultural peatland to measure over 70,000 individual N₂O, methane (CH₄), and carbon dioxide (CO₂) fluxes over 3 years.

Privacy curtain contamination, including with multidrug-resistant organisms, and the associated infection transmission risks have been well described; however, current approaches for addressing these risks and available guidance are limited. The present study describes the successful reduction of curtain contamination in five different units within a tertiary care hospital utilizing continuous dry hydrogen peroxide (DHP™). Microbial load was reduced by 99.47 percent on Day 1 and statistically significant reductions were maintained throughout the 28-day study.

https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/rcm.9078
https://doi.org/10.1002/rcm.9078

• The internal CO₂ gradient imposed by mesophyll conductance (gm) reduces substrate availability for C₃ photosynthesis. With several assumptions, estimates of gm can be made from coupled leaf gas exchange with isoflux analysis of carbon ∆¹³C‐gm and oxygen in CO₂, coupled with transpired water (H₂O) ∆¹⁸O‐gm to partition gm into its biochemical and anatomical components.

A total of 2 to 3 million tons of spring water flushes out from the foot of Mt. Fuji, the largest volcanic mountain in Japan. Based on the concept of piston flow transport, residence time of stored groundwater at Mt. Fuji was estimated at  ∼  15–30 years by the 36Cl ∕ Cl ratio (Tosaki et al., 2011). This range, however, represents the average residence time of groundwater that was mixed before it flushed out.

Catchment response to precipitation is often investigated using two-component isotope-based hydrograph separation, which quantifies the contribution of precipitation (i.e., event water Qe) or water from storage (i.e., pre-event water Qpe) to total discharge (Q) during storm events. In order to better understand streamflow-generating mechanisms, two-component hydrograph separation studies often seek to relate the event-water fraction Qe∕Q to storm characteristics or antecedent wetness conditions.

Sumatra Squalls, organized bands of thunderstorms, are the dominant mesoscale convective systems during the intermonsoon and southwest monsoon seasons in Singapore. To understand how they affect precipitation isotopes, we monitored the δ value of precipitation daily and continuously (every second and integrated over 30 s) during all squalls in 2015. We found that precipitation δ18O values mainly exhibit a “V”‐shape pattern and less commonly a “W”‐shape pattern.

A fundamental challenge in plant physiology is independently determining the rates of gross O₂ production by photosynthesis and O2 consumption by respiration, photorespiration, and other processes. Previous studies on isolated chloroplasts or leaves have separately constrained net and gross O2 production (NOP and GOP, respectively) by labeling ambient O₂ with ¹⁸O while leaf water was unlabeled. Here, we describe a method to accurately measure GOP and NOP of whole detached leaves in a cuvette as a routine gas-exchange measurement.

High-resolution data on a field scale is very important for improving our understanding of hydrological processes. This is particularly the case for water-demanding agricultural production systems such as rice paddies, for which water-saving strategies need to be developed. Here we report on the application of an in situ, automatic sampling system for high-resolution data on stable isotopes of water (¹⁸O and ²H).

In older persons, muscle loss is accelerated during physical inactivity and hypoenergetic states, both of which are features of hospitalization. Protein supplementation may represent a strategy to offset the loss of muscle during inactivity, and enhance recovery on resumption of activity. We aimed to determine if protein supplementation, with proteins of substantially different quality, would alleviate the loss of lean mass by augmenting muscle protein synthesis (MPS) while inactive during a hypoenergetic state.

Raindrops interact with water vapour in ambient air while sedimenting from the cloud base to the ground. They constantly exchange water molecules with the environment and, in sub-saturated air, they evaporate partially or entirely. The latter of these below-cloud processes is important for predicting the resulting surface rainfall amount. It also influences the boundary layer profiles of temperature and moisture through evaporative latent cooling and humidity changes. However, despite its importance, it is very difficult to quantify this process from observations.

Formaldehyde (HCHO) and nitrogen dioxide (NO₂) often co-exist in urban environments at levels that are hazardous to health. There is a demand for a solution to the problem of their combined removal. In this paper, we investigate catalysts, adsorbents and composites for their removal efficiency (RE) toward HCHO and NO₂, in the context of creating a pollution control device (PCD). Proton-transfer-reaction mass spectrometry and cavity ring-down spectrometry are used to measure HCHO, and chemiluminescence and absorbance-based monitors for NO₂.

Carbon content constitutes a major fraction of atmospheric particulate matter (PM) and directly influences the earth’s climate and human health. The stable carbon isotope ratios (δ¹³C) can be used to track potential sources and atmospheric processes of carbonaceous aerosols. Previously, determination of δ¹³C was always conducted in offline carbonaceous aerosol samples. The poor time-resolution results cannot provide information regarding the temporal evolution of δ¹³C at a short-time scale.

As part of manufacturing a sterile drug product, we quantified the impact of H₂O₂ sorption by polymers  on the duration of aeration in pharmaceutical decontamination. Five polymers, which are typically used as materials/parts in sterile isolators, were investigated: polyethylene, polyvinyl chloride, Silicone, polyoxymethylene (POM), and chlorosulfonated polyethylene. Experiments were performed to estimate the storage capacity and diffusion coefficients of H₂O₂ in the polymer. Considering these key properties of

We developed regression models for designing rapid and effective H₂O₂ decontamination processes in the manufacturing of sterile drug products such as injectables. Decontamination, which is typically performed by using H₂O₂, is a critical changeover process used to establish a sterile environment for filling products. In the process, there is a = trade-off relationship between the duration of the process and the level of sterility assurance that needs to be considered in the design.

Isolators are commonly used in filling operations of pharmaceutical products. To ensure an aseptic inner environment, isolators are regularly sterilized with vaporized hydrogen peroxide. However, despite extensive purging with air, some residual H₂O₂ remains within the isolator atmosphere and may thus end up in the liquid pharmaceutical drug product, which subsequently may cause oxidation and impact the product’s safety and efficacy. We aimed to evaluate the extent of this phenomenon and to model it.

A monoclonal antibody drug product (DP) manufacturing process was transferred to a different production site, where aseptic filling took place within an isolator that was sanitized using vapor phase hydrogen peroxide (VPHP). A quality-by-design approach was applied for study design to understand the impact of VPHP uptake in the isolator on DP quality. A combination of small-scale and manufacturing-scale studies was performed to evaluate the sensitivity of the monoclonal antibody to hydrogen peroxide (H₂O₂) as well as VPHP uptake mechanisms during the filling process.

Atmospheric sulfate aerosols have important impacts on air quality, climate, and human and ecosystem health. However, current air-quality models generally underestimate the rate of conversion of sulfur dioxide (SO₂) to sulfate during severe haze pollution events, indicating that our understanding of sulfate formation chemistry is incomplete. This may arise because the air-quality models rely upon kinetics studies of SO₂ oxidation conducted in dilute aqueous solutions, and not at the high solute strengths of atmospheric aerosol particles.

Formaldehyde (HCHO) and nitrogen dioxide (NO₂) often co-exist in urban environments at levels that are hazardous to health. There is a demand for a solution to the problem of their combined removal. In this paper, we investigate catalysts, adsorbents and composites for their removal effciency (RE) toward HCHO and NO₂, in the context of creating a pollution control device (PCD). Proton-transfer-reaction mass spectrometry and cavity ring-down spectrometry are used to measure HCHO, and chemiluminescence and absorbance-based monitors for NO₂.

To improve our understanding of chlorine chemistry indoors, reactive chlorine species such as hydrogen chloride (HCl) must be analyzed using fast time-response measurement techniques. Although well studied outdoors, sources of HCl indoors are unknown. In this study, mixing ratios of gaseous HCl were measured at 0.5 Hz in the indoor environment using a cavity ring-down spectroscopy (CRDS) instrument. The CRDS measurement rate provides a major advance in observational capability compared to other established techniques.