Background and aims

Positive relationships between temperature and soil respiration rate are widely observed, but it remains unclear if the relationships are due to increases in soil organic matter mineralisation (R _om), or in root and rhizosphere respiration (R _roots), or increases in both. This study aims to determine the relative…

Chemical and stable isotopic compositions (δD, δ¹⁸O, and δ³⁴S) of non-volcanic hot spring waters around the Miocene Kofu granitic complex surrounding the Kofu basin in the South Fossa Magna region of central Honshu, Japan, were analyzed in order to investigate water–rock interactions and to determine the origin and sulfur isotopic characteristics of their trace amounts…

A new method of extracting regional background concentration of CO₂ in Yangtze River Delta was established based on the observations of both black carbon concentration and meteorological parameters. The concentrations of CO₂ and black carbon were observed at Lin'an regional background station from 2009 to 2011. The regional background concentration of CO_…

Radiocarbon can be used to trace fossil fuel CO₂ (CO₂ff) in the atmosphere, because radiocarbon has been depleted in fossil fuels. Here we present our study on the spatial distribution and temporal variations of CO₂ff in Xi'an City, China using Δ¹⁴C of both green foxtail (Setaria viridis, L. Beauv.) leaf samples and…

Assessing the impacts of methane released from hydrate-bearing environments on global carbon cycling would require detailed insights into the distributions and capacities of microbial communities at different horizons of sediment column. In this study, we conducted geochemical, gene abundance and diversity analyses for a sediment core retrieved from a potential hydrate-bearing region off…

The Siberian region is still sparsely covered by ecosystem observatories, which motivates the exploitation of existing data sets to gain spatially and temporally better-resolved carbon budgets. The Zotino Tall Tower Observatory (ZOTTO; 60°48' N, 89°21' E) observations of CO₂ and CH₄ mole fractions as well as meteorological parameters from six different…

Atmospheric carbon dioxide (CO₂) mole fractions were continuously measured from January 2009 to December 2011 at four atmospheric observatories in China using cavity ring-down spectroscopy instruments. The stations are Lin'an (LAN), Longfengshan (LFS), Shangdianzi (SDZ), and Waliguan (WLG), which are regional (LAN, LFS, SDZ) or global (WLG) measurement stations of the World…

Measurements of the ¹⁷O_excess of H₂O were obtained from ice cores in West and East Antarctica. Combined with previously-published results from East Antarctica, the new data provide the most complete spatial and temporal view of Antarctic ¹⁷O_excess to date. There is a steep spatial gradient of ¹⁷O_excess in present-…

Facilitation and competition between different vegetation layers may have a large impact on small-scale vegetation development. We propose that this should not only influence overall herbaceous layer yield but also species distribution and understory longevity, and hence the ecosystems carbon uptake capacity especially during spring. We analyzed the effects of trees on…

We report trends in springtime ozone (O₃) and carbon monoxide (CO) at the Mt. Bachelor Observatory (MBO) in central Oregon, U.S.A. from 2004 to 2013. Over the 10-year period the median and 95th percentile springtime O₃ increased by 0.76 ± 0.61 ppbv yr⁻¹ (1.7 ± 1.4% yr⁻¹) and 0.87 ± 0.73 ppbv…

Biogeochemical dynamics under seasonal ice cover were investigated in the shallow (<10 m) water column of highly productive Georgetown Lake, western Montana, USA. This high altitude (1,800 m) reservoir is well-mixed in summer, but becomes strongly stratified under ice cover (mid-November–mid-May). A rapid drop in dissolved oxygen (DO) concentration and rise in dissolved…

Stable isotopes in water (δ²H and δ¹⁸O) are important indicators of hydrological and ecological pattern and process. δ²H and δ¹⁸O of water are incorporated into geological and biological systems in a predictable manner and have been used extensively as tracers in hydrological, ecological and forensic studies. Physical processes result in spatial…

An instrumented sample holder was developed for time-lapse micro-tomography of snow samples to enable in-situ nondestructive spatial and temporal measurements under controlled advective airflows, temperature gradients, and air humidities. The design was aided by computational fluid dynamics simulations to evaluate the airflow uniformity across the snow sample. Morphological and mass…

In the Ziz Basin, located in arid area in southeastern Morocco, surface waters are scarce and local populations are entirely dependent on groundwater resources for drinking and irrigation. In order to evaluate the main factors controlling the origin and salinization of groundwater resources, we have investigated the chemical and stable isotope compositions of groundwater and surface water…

The chemical and physical properties of secondary organic aerosol (SOA) formed by the photochemical degradation of biogenic and anthropogenic volatile organic compounds (VOC) are as yet still poorly constrained. The evolution of the complex refractive index (RI) of SOA, formed from purely biogenic VOC and mixtures of biogenic and anthropogenic VOC, was studied over a diurnal cycle in the…

• The oxygen isotope signature of water is a powerful tracer of water movement from plants to the global scale. However, little is known about the short-term variability of oxygen isotopes leaving the ecosystem via transpiration, as high-frequency measurements are lacking.
• A laser spectrometer was coupled to a gas-exchange chamber directly estimating branch-level fluxes in order…

In order to better understand the constraints on the use of barium as a coastal paleo-freshwater tracer, we surveyed the dissolved Ba distribution in Louisiana Shelf waters, including the Mississippi (MR) and Atchafalaya (AR) River plumes, during May and November 2008, and June/July 2009, which represent high, low and intermediate river discharges, respectively. Dissolved Ba was found…

In atmospheric and environmental sciences, optical spectrometers are used for the measurements of greenhouse gas mole fractions and the isotopic composition of water vapor or greenhouse gases. The large sample cell volumes (tens of milliliters to several liters) in commercially available spectrometers constrain the usefulness of such instruments for applications that are limited in sample…

In this paper, we report the vertical profiles of CO₂ and CH₄ measured with a cavity ring-down spectrometer (CRDS) on a research aircraft from near-ground level to 8 km above mean sea level. The airborne platform employed in this paper is an Alpha Jet aircraft operated from NASA's Ames Research Center. Flights were undertaken to Railroad Valley, NV, USA, to…

Hillslopes are the dominant landscape components where incoming precipitation is transferred to become groundwater, streamflow or atmospheric water vapor. However, directly observing flux partitioning in the soil is almost impossible. Hydrological hills-lope models are therefore being used to investigate the involved processes. Here we report on a modeling experiment using the Catchment…

Precise methods for the detection of geologically stored CO₂ within and above soil surfaces are an important component of the development of carbon capture and storage (CCS) under terrestrial environments. Although CO₂ leaks are not expected in well-chosen and operated storage sites, monitoring is required by legislation and any leakage needs to be quantified…

A Particle-into-Liquid Sampler – Total Organic Carbon and fraction collector sys-tem was flown aboard a Twin Otter aircraft sampling prescribed burning emis-sions in South Carolina in November 2011 to obtain smoke marker measure-ments. The fraction collector provided 2min time-integrated off-line samples for car-bohydrate (i.e., smoke markers levoglucosan, mannosan, galactosan) analysis by…

Water is the key resource limiting world agricultural production. Although an impressive number of research reports have been published on plant drought tolerance enhancement via genetic modifications during the last few years, progress has been slower than expected. We suggest a feasible alternative strategy by application of rhizospheric bacteria coevolved with plant roots in harsh…

Silage is an important dietary water source that influences the oxygen and hydrogen isotopic composition of domestic herbivores and their products. Silage sampled fresh from the silo had¹⁸O- and ²H-depleted tissue water when compared with fresh pasture grass sampled around midday during the silage-making seasons. During exposure in the feed bunk, silage water…

Degradation of plant material by animals is an important transformation pathway in the nitrogen (N) cycle. During the involved processes, volatile reduced alkaline nitro-gen compounds, mainly ammonia (NH₃) and aliphatic amines such as trimethylamine (TMA), are formed. Today, animal husbandry is estimated to constitute a main source of aliphatic amines into the atmosphere with TMA…

Hydrological and geochemical processes controlling the pore water chemistry in a permafrost wetland, with loam overlain by sphagnum peat, were investigated. The vertical distributions of dissolved Cl, and of pore water δ¹⁸O, appeared unrelated to ion freeze-out and isotope ice-water fractionation processes, respectively, dismissing solute freeze-out as a main control on the water…

Hydrogeochemistry of 32 hot springs in the western Sichuan Province after the Wenchuan  8.0 earthquake was investigated by analyzing the concentrations of cation and anion and the isotopic compositions of hydrogen and oxygen. The water samples of the hot springs were collected four times from June 2008 to April 2010. Hydrogeochemical data indicated the water samples can be…

The East Scotia Ridge is an active back-arc spreading centre located to the west of the South Sandwich island arc in the Southern Ocean. Initial exploration of the ridge by deep-tow surveys provided the first evidence for hydrothermal activity in a back-arc setting outside of the western Pacific, and we returned in 2010 with a remotely operated vehicle to precisely locate and sample…

Suitable predictors of degradability are sought to support the identification of biochars with large potential to increase C sequestration in soils. We determined the biodegradation of 9 chars from hydrothermal carbonization and pyrolysis in two agricultural soils. The 200- and 115-day degradation correlated strongly with the O:C- and slightly with the H:C-atomic ratio of 9 and 14 biochars…

A dedicated system for airborne ship emission measurements of SO₂, NO_x and particles has been developed and used from several small aircraft. The system has been adapted for fast response measurements at 1 Hz, and the use of several of the instruments is unique. The uncertainty of the given data is about 20% for SO₂ and 24% for NO_x …

There is a pressing need to verify air pollutant and greenhouse gas emissions from anthropogenic fossil energy sources to enforce current and future regulations. We demonstrate the feasibility of using simultaneous remote sensing observations of column abundances of CO₂, CO, and NO₂ to inform and verify emission inventories. We report, to our knowledge, the first ever…

A reliable and precise in situ CO₂ and CO analysis system has been developed and deployed at eight sites in the NOAA Earth System Research Laboratory's (ESRL) Global Greenhouse Gas Reference Network. The network uses very tall (> 300 m) television and radio transmitter towers that provide a convenient platform for mid-boundary-layer trace-gas sampling. Each analyzer has…

High-precision analysis of the ¹⁷O / ¹⁶O isotope ratio in water and water vapor is of interest in hydrological, paleoclimate, and atmospheric science applications. Of specific interest is the parameter ¹⁷O excess (Δ¹⁷O), a measure of the deviation from a‾linear relationship between ¹⁷O / ¹⁶O and…

RATIONALE

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

Plant, soil and insect water is extracted into a dry air stream by…

Dissolved oxygen (DO) is commonly recognized as an important factor influencing nitrous oxide (N₂O) production by ammonia-oxidizing bacteria (AOB). However, it has been difficult to separate the true effect of DO from that of nitrite, as DO variation often affects nitrite accumulation. The effect of DO on N₂O production by an enriched nitrifying sludge, consisting of…