Abstract
Agricultural fields in drylands are challenged globally by limited freshwater resources for irrigation and also by elevated soil salinity and sodicity. It is well known that pedogenic ...carbonate is less soluble than evaporate salts and commonly forms in natural drylands. However, few studies have evaluated how irrigation loads dissolved calcium and bicarbonate to agricultural fields, accelerating formation rates of secondary calcite and simultaneously releasing abiotic CO
2
to the atmosphere. This study reports one of the first geochemical and isotopic studies of such “anthropogenic” pedogenic carbonates and CO
2
from irrigated drylands of southwestern United States. A pecan orchard and an alfalfa field, where flood-irrigation using the Rio Grande river is a common practice, were compared to a nearby natural dryland site. Strontium and carbon isotope ratios show that bulk pedogenic carbonates in irrigated soils at the pecan orchard primarily formed due to flood-irrigation, and that approximately 20–50% of soil CO
2
in these irrigated soils is calcite-derived abiotic CO
2
instead of soil-respired or atmospheric origins. Multiple variables that control the salt buildup in this region are identified and impact the crop production and soil sustainability regionally and globally. Irrigation intensity and water chemistry (irrigation water quantity and quality) dictate salt loading, and soil texture governs water infiltration and salt leaching. In the study area, agricultural soils have accumulated up to 10 wt% of calcite after just about 100 years of cultivation. These rates will likely increase in the future due to the combined effects of climate variability (reduced rainfall and more intense evaporation), use of more brackish groundwater for irrigation, and reduced porosity in soils. The enhanced accumulation rates of pedogenic carbonate are accompanied by release of large amounts of abiotic CO
2
from irrigated drylands to atmosphere. Extensive field studies and modelling approaches are needed to further quantify these effluxes at local, regional and global scales.
The behavior of gaseous components of forest soil was assessed by simultaneous monitoring of
222
Rn, CO
2
and its carbon isotopes (δ
13
C, Δ
14
C) in soil air under a semi natural forest in northern ...Japan. The isotope ratio of
14
C (Δ
14
C) in soil air CO
2
was found to decrease towards late summer, suggesting gradual depletion of easily decomposed soil organic matter. There was a specific case that soil air CO
2
with depleted
14
C appeared suddenly under snowpack in winter. It is not always appropriate to use soil
222
Rn as a tracer of CO
2
efflux from the soil surface to the atmosphere.
The Mediterranean diet is promoted as one of the healthiest and closely linked to socioecological practices, knowledge and traditions, promoting sustainable food production, and linking geographical ...origin with food quality and ecosystem services. Consumer adherence to this dietary pattern drives increased consumption of authentic "premium" foods, such as Iberian pig meat and dry-cured ham from Portugal and Spain, argan oil from Morocco, "Djebel" lamb from Tunisia and truffles from Italy and Slovenia, i.e., food products that respond to current ethical, environmental and socially sustainable demands. Geographical indication and appellation of origin can increase traditional food products competitiveness, but the high-value recognition of these products can also lead to economically motivated product adulteration. It is therefore imperative to protect the high added value of these unique food products by ensuring their quality, authenticity, provenance and sustainable production systems. In this review, we provide a critical evaluation of the analytical methods that are currently used for the determination of provenance and authenticity of these Mediterranean products as well as possible strategies for improving the throughput and affordability of the methods discussed.
The present knowledge of the carbonate system in the northern Adriatic is described in this short overview. Its buffer capacity is rather high, due to riverine input of carbonates dissolved from ...Alpine and Karstic watersheds, and the waters should have a higher resilience to acidification. In the shallow eutrophic areas, the combined effect of rising atmospheric CO2, warming and river-induced anthropogenic CO2 with the associated decrease in buffer capacity could act to acidification process. Significant effect on calcifying organisms is expected in the future.
This paper aimed to establish the optimal conditions for ultrasound-assisted extraction of polyphenols from domestic garlic (Allium sativum L.) using response surface methodology (RSM) and artificial ...neural network (ANN) approach. A 4-factor-3-level central composite design was used to optimize ultrasound-assisted extraction (UAE) to obtain a maximum yield of target responses. Maximum values of the two output parameters: 19.498 mg GAE/g fresh weight of sample total phenolic content and 1.422 mg RUT/g fresh weight of sample total flavonoid content were obtained under optimum extraction conditions: 13.50 min X1, 59.00 °C X2, 71.00% X3 and 20.00 mL/g X4. Root mean square error for training, validation, and testing were 0.0209, 3.6819 and 1.8341, respectively. The correlation coefficient between experimentally obtained total phenolic content and total flavonoid content and values predicted by ANN were 0.9998 for training, 0.9733 for validation, and 0.9821 for testing, indicating the good predictive ability of the model. The ANN model had a higher prediction efficiency than the RSM model. Hence, RSM can demonstrate the interaction effects of basic inherent UAE parameters on target responses, whereas ANN can reliably model the UAE process with better predictive and estimation capabilities.
•The first report of RSM and ANN models were applied to ultrasound-assisted extraction of phenolic compounds from domestic garlic.•We apply neural network to improve response surface methodology.•The ANN model was superior to RSM for predicting phenolic compounds extraction recovery.
This study aims to validate the stable carbon isotopic composition (δ13C) of phytoplankton as a tool for detecting submarine leakages of anthropogenic CO2(g), since it is characterised by δ13C values ...significantly lower than the natural CO2 dissolved in oceans. Three culture experiments were carried out to investigate the changes in δ13C of the diatom Thalassiosira rotula during growth in an artificially modified medium (ASW). Three different dissolved inorganic carbon (DIC) concentrations were tested to verify if carbon availability affects phytoplankton δ13C. Simultaneously, at each experiment, T. rotula was cultured under natural DIC isotopic composition (δ13CDIC) and carbonate system conditions. The available DIC pool for diatoms grown in ASW was characterised by δ13CDIC values (−44.2 ± 0.9‰) significantly lower than the typical marine range. Through photosynthetic DIC uptake, microalgae δ13C rapidly changed, reaching significantly low values (until −43.4‰). Moreover, the different DIC concentrations did not affect the diatom δ13C, exhibiting the same trend in δ13C values in the three ASW experiments. The experiments prove that phytoplankton isotopic composition quickly responds to changes in the δ13C of the medium, making this approach a promising and low-impact tool for detecting CO2(g) submarine leakages from CO2(g) deposits.
Purpose
The objective of this research is to detect abiotic sources of soil CO
2
above a subterranean cave in the Slovenian karst region.
Materials and methods
The research was performed in the ...forest above Pisani rov (Postojna Cave) near the town of Postojna (SW Slovenia) and also in the cave. Soil gas, atmospheric air and cave air carbon stable isotope composition (δ
13
C
CO2
) and CO
2
concentration were measured. Sampling and measurements were performed bi-monthly at the test and control sites above the cave. The abiotic source of soil CO
2
was estimated using a stable isotope mass balance calculation.
Results and discussion
Similar seasonal patterns of soil CO
2
and δ
13
C
CO2
values were observed at both the test and control sites until spring, with higher levels of CO
2
observed in summer and lower in winter. The δ
13
C
CO2
showed the opposite trend, i.e. lower values (−26 to −20 ‰) in summer and higher values (up to −17 ‰) in winter and early spring. In spring, the soil CO
2
concentration decreases and the δ
13
C
CO2
value increases only at the control site. A time series of a modelled “isotopically light” endmember revealed large shifts in the data values, due to the presence of an abiotic CO
2
source. Results suggest that the subterranean CO
2
pool and its ventilation is the main source of soil CO
2
, accounting for up to 80 % of the soil gas during cold periods.
Conclusions
Ventilation from subterranean cavities is an important source of soil CO
2
in karstic areas and should be taken into account during carbon cycling studies.
An increased frequency of fire events on the Slovenian Karst is in line with future climate-change scenarios for drought-prone environments worldwide. It is therefore of the utmost importance to ...better understand tree-fire-climate interactions for predicting the impact of changing environment on tree functioning. To this purpose, we studied the post-fire effects on leaf development, leaf carbon isotope composition (ẟ13C), radial growth patterns and the xylem and phloem anatomy in undamaged (H-trees) and fire-damaged trees (F-trees) of Q. pubescens with good re-sprouting ability in spring 2017, the growing season after a rangeland fire in August 2016. We found that the fully developed canopy of F-trees reached only half of the LAI values measured in H-trees. Throughout the season, F-trees were characterised by higher water potential and stomatal conductivity and achieved higher photosynthetic rates compared to unburnt H-trees. The foliage of F-trees had more negative δ13C values than those of H-trees. This reflects that F-trees less frequently meet stomatal limitations due to reduced transpirational area and more favourable leaf-to-root ratio. In addition, the growth of leaves in F-trees relied more on the recent photosynthates than on reserves due to the fire disturbed starch accumulation in the previous season. Cambial production stopped 3 weeks later in F-trees, resulting in 60% and 22% wider xylem and phloem increments, respectively. A novel approach by including phloem anatomy in the analyses revealed that fire caused changes in conduit dimensions in the early phloem but not in the earlywood. However, premature formation of the tyloses in the earlywood vessels of the youngest two xylem increments in F-trees implies that xylem hydraulic integrity was also affected by heat. Analyses of secondary tissues showed that although xylem and phloem tissues are interlinked changes in their transport systems due to heat damage are not necessarily coordinated.
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