Changes In CO2 Concentration Research Articles

Multiphase CO[formula omitted] dispersions in microfluidics: Formation, phases, and mass transfer

The dissolution and microfluidic mass transfer of carbon dioxide in water at high-pressure conditions are crucial for a myriad of technological applications, including microreactors, extractions, and carbon capture, utilization, and sequestration (CCUS) processes. In this experimental work, we use a high-pressure microfluidic method to elucidate the mass transfer process of CO2 in water at high pressure. An intriguing multiphase CO2 flow and dispersions are observed when operating at the pressure–temperature (P–T) condition close to the CO2 gas–liquid phase boundary (P=6.5MPa and T=23.5±0.5°C). We propose a series of strategies to unravel this complex multi-phase dynamics by calculating each phase's volume and mass change in a gas–liquid coexistent CO2 dispersion, estimating the possible CO2 concentration change in water, and comparing with the CO2 solubility data. Finally, we quantify the CO2 mass transfer by directly calculating the CO2 dissolution rate in water and estimating the volumetric mass transfer coefficient (kLa). The results show that the mass transfer may be influenced by the specific area (a), CO2 concentration gradient in the water slug, and the traveling speed of a dispersion.

Food Security Under The Era Of Climate Change Threat

Food Security Under The Era Of Climate Change Threat

Cultivating marine macroalgae in CO2-enriched seawater: A bio-economic approach

By the end of the current century atmospheric CO2 concentration may reach 1000 ppm, more than twice the present level set at ca. 400 ppm. Marine macroalgae (seaweeds) contribute to global primary production and by taking up CO2 they may ameliorate and regulate global climate change. Seaweeds also have direct and indirect economic importance by providing food and bioactive compounds for human benefit. Nonetheless, all these benefits could be jeopardized by the ongoing pressures, both local and global, on marine environments. In this study we examine the effects of dissolved CO2 and seasonal seawater temperature on the growth rates (measured weekly changes in biomass and expressed on a daily basis) of two model species, Ulva rigida (Chlorophyta) and Gracilaria conferta (Rhodophyta), which are common in the intertidal zone of the Israeli Mediterranean Sea, and cultivated by the local seaweed industry. The seaweeds were grown in land-based 40 L fiberglass tanks fertilized with sufficient N and P, supplied with running seawater and continuous air bubbling to keep equal exposure of the seaweeds to nutrients and light. The tanks were also provided with aeration with regular air (ambient CO2, ~ 400 ppm) or CO2-enriched air (~780 ppm). Seaweeds exposed to CO2–enriched seawater grew faster, 32.5 and 8.5% growth per day for U. rigida and G. conferta, respectively. Following calculations of productivity rates, market price, and input cost, we estimate production and show a quadratic production function with respect to temperature for each CO2 concentration. Thus, there is an optimal temperature that maximizes seaweed output. Based on the production function estimates and using market prices, maximal short-run profits were obtained at ca. 22.5 °C and 27.5 °C for U. rigida and G. conferta, respectively. These results may provide useful information for seaweed growers on what and where to grow seasonally, and how farming activities should adapt to external changes in temperature and CO2 concentration.

Changes in Urban Gas-Phase Persistent Organic Pollutants During the COVID-19 Lockdown in Barcelona

The composition of polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs), hexachlorobenzene (HCB), pentachlorobenzene (PeCB), and organophosphate flame retardants (OPFRs) present in the gas-phase fraction of the atmosphere of Barcelona was analyzed during the SARS-CoV-2 coronavirus disease (COVID-19) lockdown and prior to this period. The changes in daily concentrations of CO, NO, NO2, O3 and particulate matter smaller than 10 μm (PM10) were considered for comparison. Bayesian analysis considering serial dependencies and seasonality showed statistically significant decreases of CO, NO, NO2, and PM10 (between −28 and −76%) and O3 increases (+45%) during lockdown. However, the lockdown concentration decreases of PeCB (−90.5%, from 8.5 to 0.8 pg m–3), HCB (−79%, 25.5–5.4 pg m–3) and some PAHs, such as benz[a]anthracene (−87%, 120–17 pg m–3) and pyrene (−81%, 3,500–680 pg m–3), were even stronger. The PAH depletion ranged between −68 and −87% that could be primarily associated with the strong reduction of traffic mobility during this period (−80%). Besides traffic reduction, the observed air quality improvements could be related to lower generation of solid urban residues (−25%) and the subsequent decrease of urban waste incineration (between −25 and −28%). Tributyl phosphate also showed a reduction in concentration during lockdown but the other OPFRs were seemingly not affected by this restriction, possibly as a result of the uniform release from the emission sources, e.g., construction material, industrial applications, and household products.

Proposal of an Effective Indicator of CO2 Concentration in Seawater

Since CO2 is easily soluble in water, when the concentration of CO2 in the atmosphere rises, that in seawater also rises. This causes the surface ocean acidification, which may alter the chemical and biological activities in the surface ocean. Therefore, it is important to know the temporal and spatial changes in CO2 concentration in the surface ocean. However, seawater CO2 concentration has large regional and seasonal variations mainly because of biological activities. In this study, we proposed an effective measure of the seawater CO2 concentration from the relationship between [DIC + kDO] and water temperature. A strong linear correlation was found for this relationship using seawater data off Tomakomai and in Osaka Bay, Japan. Furthermore, we confirmed that correction with salinity improves this correlation, because salinity is known to have a good correlation with alkalinity, which directly affects DIC. It is expected that this measure can also be applicable to judge the possibility of unexpected leakage of CO2 stored in the sub-seabed geological formation.

Effect of high hydrostatic pressure (HHP) and supercooling storage in leaf mustard (Brassica juncea L.) kimchi: Modelling of microbial activity and preservation of physicochemical properties

Kimchi products have a short shelf life due to continuous bacterial growth and fermentation. Herein, the microbiological and physicochemical properties of leaf mustard (Brassica juncea L.) kimchi were evaluated after high hydrostatic pressure (HHP) treatment (400 and 600 MPa for 5 min) and storage under supercooling (˗4.5 °C) or refrigeration (4 and 8 °C) conditions. Moreover, predictive models describing the growth kinetics of total lactic acid bacteria (TLAB) in leaf mustard kimchi were constructed. Treatment with 600 MPa reduced the total LAB and coliform counts in the samples before storage to 1.30 and > 1 log CFU/g, respectively. Supercooling storage prevented microbial growth for 30 days and allowed the maintenance of the titratable acidity, reducing sugar content, instrumental colour, total phenolic content, and antioxidant capacity of the samples. The Logistic and Gompertz models were relatively more acceptable to predict the growth behaviour of TLAB in leaf mustard kimchi treated/non-treated with 400 MPa during supercooled or refrigerated storage. Altogether, these findings suggest that HHP treatment combined with supercooling storage conditions that delay O2 and CO2 concentration changes in packaged kimchi's headspace could help maintain the initial microbiological and physicochemical qualities of leaf mustard kimchi.

Low-cost chamber design for simultaneous CO2 and O2 flux measurements between tree stems and the atmosphere.

Tree stem CO2 efflux is an important component of ecosystem carbon fluxes and has been the focus of many studies. While CO2 efflux can easily be measured, a growing number of studies have shown that it is not identical with actual in situ respiration. Complementing measurements of CO2 flux with simultaneous measurements of O2 flux provides an additional proxy for respiration, and the combination of both fluxes can potentially help getting closer to actual measures of respiratory fluxes. To date, however, the technical challenge to measure relatively small changes in O2 concentration against its high atmospheric background has prevented routine O2 measurements in field applications. Here, we present a new and low-cost field-tested device for autonomous real-time and quasi-continuous long-term measurements of stem respiration by combining CO2 (NDIR-based) and O2 (quenching-based) sensors in a tree stem chamber. Our device operates as a cyclic-closed system and measures changes in both CO2 and O2 concentration within the chamber over time. The device is battery powered with a >1-week power independence, and data acquisition is conveniently achieved by an internal logger. Results from both field and laboratory tests document that our sensors provide reproducible measurements of CO2 and O2 exchange fluxes under varying environmental conditions.

Estimating Number and Dwell Time of Visitors in a Large-scale Indoor Space from HVAC Data and Its Evaluation in Different Seasons

The aim of this paper is to estimate the number and dwell time of visitors in a large-scale indoor space or room with a common heating-ventilation-air conditioning (HVAC) system that includes sensors for CO2 and indoor temperature in any season. Previous studies tried to estimate the number and dwell time of visitors from CO2 concentration in small rooms with or without a HVAC system. However, in a large-scale indoor space with large air-conditioning and ventilation systems, the number and dwell time of visitors are difficult to estimate for three reasons: 1) CO2 concentration changes much more slowly than the number and dwell time of visitors and with a delay, 2) the difference in changes is affected by the amount of ventilation, and 3) this difference may be affected by operation of HVAC, which is affected by seasonal climate. To solve these problems, we proposed partial modeling with a variable time window. This method can make a partial estimation model that automatically corresponds to differences in the change speed between two variables: visitors and CO2 concentration. We demonstrate the effectiveness of our proposal using measured sensor data in summer, fall, and winter to clarify its feasibility in different seasons in Japan.

Modeling maize and soybean responses to climatic change and soil degradation in a region of South America

AbstractClimatic change effects on crop yields are expected to be crop‐ and site specific. Here, Decision Support System for Agrotechnology Transfer models were used to evaluate climatic change effects and mitigation strategies on maize (Zea mays L.) and soybean [Glycine max (L.) Merr.] yields in soils of the subtropical and semi‐arid region of Chaco. Simulations were performed for the DK747 and A8000 genotypes, calibrated for the CERES‐Maize model in a previous report and for the CROPGRO‐Soybean model in the present study, respectively. Both crops markedly differ in their response to climatic change and putative levels of atmospheric CO2 concentration. The observed significant reductions in maize yields in future climate scenarios (5–42% compared with the baseline, 1986–2010) were more associated with increased temperatures that shortened the crop cycle than with water stress. Delaying the sowing date is a feasible strategy to mitigate this effect. Projected temperature increases are expected to play a secondary role in determining soybean yields. Instead, water stress will continue to be an important constraint to soybean yield in the context of global warming, but this effect is strongly affected by rainfall regimes. Responses to raising CO2 levels were more pronounced in soybean (+10–40%) than in maize (+2–4%). Soil degradation exacerbated the negative effects of global warming on crop yields, especially on maize, which highlights the importance of soil conservation practices. The observed high interannual climatic variability and the different sensitivities of maize and soybean to climatic variables indicate that crop diversification would be the key to improve the resilience of the agrosystems under the future scenarios.

Homeostatic response of Aptian gymnosperms to changes in atmospheric CO2 concentrations

Abstract The sensitivity of plant carbon isotope fractionation (13Δleaf) to changes in atmospheric CO2 concentrations (Ca) is the subject of heavy debate, with some studies finding no sensitivity, while others show a strong dependency. We tested the hypothesis of photosynthetic homeostasis by using δ13C of n-alkanes, cuticles, and bulk organic matter of gymnosperm-rich rocks (Arundel Clay) from two sites deposited during the Aptian, a time that experienced signifi-cant Ca variations. Our results show no effect of Ca on 13Δleaf, and a relatively constant Ci/Ca (0.64 ± 0.04, 1σ; i—intercellular space), a value that is similar to that of modern gymnosperms. These results suggest that Aptian gymnosperms used homeostatic adjustments with rising Ca, probably involving increased carbon assimilation and/or stomatal closure, a response also found in modern gymnosperms. The similarity between Aptian and modern gymnosperms suggests that the processes responsible for regulating CO2 and water vapor exchange during photosynthesis have remained unaltered in gymnosperms for the past 128 m.y.

Analysis of Changes in the Concentration of Carbon Dioxide in Indoor Air of a Sports University

Introduction: Air quality of the premises of a sports university determines comfort and effectiveness of the educational and training processes and can be considered as a risk factor for students’ health. The purpose of our study was to give a hygienic assessment of changes in the indoor CO2 concentration at a sports university during the school day. Materials and methods: Air quality measurements were taken in twelve classrooms, six lecture halls, three sports halls, and a gym. The subjective assessment of air quality in classrooms was analyzed using data of a questionnaire-based survey of 651 students. Results: We found that differences in the proportion of air samples with elevated CO2 concentrations between the rooms were insignificant and ranged from 32 ± 4.66 % to 41.33 ± 2.84 % in the cold season (CS) and from 42.33 ± 2.85 % to 49.33 ± 4.08 % in the warm season (WS). Average CO2 concentrations in non-standard samples were 1,132.11 ± 93.21 ppm and 1,124.98 ± 98.51 ppm in the cold and warm season, respectively. We established that in the cold season, indoor CO2 concentration exceeded the permissible limit in 100 % of the classrooms, 50 % of the lecture halls and the gym already by 3.40 p.m. (15:40); by the end of the school day, the excess was registered in 100 % of the university rooms. In the warm season, CO2 concentrations were above the limit in the gym and in 33.3% of the lecture halls by 1 p.m. (13:00), and by 3.40 p.m. the excess was observed in 100 % of the rooms examined. Subjective air quality assessments indicated that most students often complained about stuffiness in classrooms; 25.25 ± 1.2 % of the respondents mentioned a strong odor in sports halls and the gym. Conclusion: In a significant part of sports university rooms, CO2 concentrations did not exceed permissible values for more than 80 % of school hours. Yet, after the fourth double lesson, this air quality indicator went beyond the standard value, and by the end of the school day indoor concentrations of carbon dioxide were above the permissible limit in 100 % of the university rooms.

Non-stationary response of rain-fed spring wheat yield to future climate change in northern latitudes

The non-stationary response of crop growth to changes in hydro-climatic variables makes yield projection uncertain and the design and implementation of adaptation strategies debatable. This study simulated the time-varying behavior of the underlying cause-and-effect mechanisms affecting spring wheat yield (SWY) under various climate change and nitrogen (N) application scenarios in the Red Deer River basin in agricultural lands of the western Canadian Prairies. A calibrated and validated Soil and Water Assessment Tool and Analysis of Variance decomposition methods were utilized to assess the contribution of crop growth parameters, Global Climate Models, Representative Concentration Pathways, and downscaling techniques to the total SWY variance for the 2040–2064 period. The results showed that the cause-and-effect mechanisms, driving crop yield, shifted from water stress (W-stress) dominated (27 days of W-stress days) during the historical period to nitrogen stress (N-stress) dominated (27 to 35 N-stress days) in the future period. It was shown that while higher precipitation, warmer weather, and early snowmelts, along with elevated CO2 may favor SWY in cold regions in the future (up to 50% more yields in some sub-basins), the yield potentials may be limited by N-stress (only up to 0.7% yield increase in some sub-basins). The N-stress might be partially related to the N deficiency in the soil, which can be compensated by N fertilizer application. However, inadequate N uptake due to limited evapotranspiration under elevated atmospheric CO2 might pose restrictions to SWY potentials even in the least N deficient regions. This study uncovers important information on the understanding of spatiotemporal variability of hydrogeochemical processes driving crop yields and the non-stationary response of yields to changing climate. The results also underscore spatiotemporal variability of N-stress due to N deficiency in the soil or N uptake by crops, both of which may restrain SWY by changes in atmospheric CO2 concentrations in the future.

N2 periodic pulsation process intensification to improve ethanol productivity in solid state fermentation of steam-exploded corn stalk

Long fermentation time and high oxygen partial pressure were significant challenges for high ethanol productivity in solid state fermentation (SSF). In this study, the feasibility of N2 periodic pulsation to improve ethanol productivity was investigated. Changes of CO2 concentration and water state distribution in N2 periodic pulsation SSF were examined. A metabolic flux model was developed to understand the effect of N2 periodic pulsation on ethanol production. The results indicated that ethanol productivity of 1.75 g/(L·h) in N2 periodic pulsation group (NPPG) was 34.4% higher than that in control group (CG) within 24 h. The maximum ethanol concentration and yield were 47.52 g/L and 70.80% at 70% moisture content, respectively. The CO2 concentration in NPPG was well below 5000 ppm at 21 h, which was much lower than 38,080 ppm in CG. Metabolic flux analysis revealed that the metabolic flux towards ethanol increased by 25% with the application of N2 periodic pulsation. These results confirmed that N2 periodic pulsation is an effective method for improving ethanol production in solid state fermentation.

Short-Term Monitoring of Geogenic Soil CO2 Flux in a Non-Volcanic and Seismically Inactive Emission Site, South Korea

Temporal changes of soil CO2 flux (FCO2) and soil CO2 concentration ([CO2]v) were surveyed in a natural CO2 emission site to characterize the factors controlling the short-term temporal variation of geogenic FCO2 in a non-volcanic and seismically inactive area. Due to a lack of long-term monitoring system, FCO2 was discontinuously measured for three periods: Ⅰ, Ⅱ at a high FCO2 point (M17) and Ⅲ about 30 cm away. Whereas [CO2]v was investigated at a point (60 cm depth) for all periods. A 2.1 magnitude earthquake occurred 7.8 km away and 20 km deep approximately 12 h before the period Ⅱ. The negative correlation of FCO2 with air pressure suggested the non-negligible advective transport of soil CO2. However, FCO2 was significantly and positively related with air temperature as well, and [CO2]v showed different temporal changes from FCO2. These results indicate the diffusive transport of soil CO2 dominant in the vadose zone, while the advection near the surface. Meanwhile [CO2]v rapidly decreased while an anomalous FCO2 peak was observed during the period Ⅱ, and the CO2 emission enhanced by the earthquake was discussed as a possible reason for the synchronous decrease in [CO2]v and increase in FCO2. In contrast, [CO2]v increased to 56.8% during the period Ⅲ probably due to low gas diffusion at cold weather. In addition, FCO2 was low during the period Ⅲ and showed different correlations with measurements compared to FCO2 at M17, implying heterogeneous CO2 transport conditions at the centimeter scale. The abnormal FCO2 observed after the earthquake in a seismically inactive area implies that the global natural CO2 emission may be higher than the previous estimation. The study result suggests a permanent FCO2 monitoring station in tectonically stable regions to confirm the impact of geogenic CO2 to climate change and its relation with earthquakes.

Influence of Heat Disturbance on the Performance of YSZ based CO2 Sensor with Compound of Li2CO3-BaCO3-Nd2O3 as Auxiliary Sensing Electrode

Suddenly changes and fluctuations of temperature often occur in the operational environment of the CO2 electrochemical sensor. In this work, the YSZ based potentiometric CO2 sensor having Li2CO3-BaCO3-Nd2O3 compound as its auxiliary sensing material was prepared. And the effects of several types of heat disturbance on the performance of this kind of sensor ware studied. The results indicate that the sensors after heat disturbances respond similarly with the sensor as prepared, which presents rapid and correct response for the change of CO2 concentration within the experimental range of 271-576802 ppm. The sensors, with or without heat disturbance, respond well as different extents of abrupt alteration of CO2 concentration occurs, and the EMF outputs recover rapidly as the concentration of CO2 change back to the base value. At the constant concentration of CO2, the EMFs of the sensors with or without heat treatment decrease slowly as the time increases, the reason for this phenomenon might be the accumulation of inert substances on the electrode interfaces and ageing of electrodes. However, heat treatment can improve the long-term stability of the sensor to some extent. Furthermore, this type of sensor works stably with the existence of water vapor (10%), it has similar response curve in the dry and water vapor content system. After some further investigations and improvements, it might be potentially applied in the practical combustion atmosphere.

Interactive Effect of Elevated CO2 and Reduced Summer Precipitation on Photosynthesis is Species-Specific: The Case Study with Soil-Planted Norway Spruce and Sessile Oak in a Mountainous Forest Plot

We investigated how reduced summer precipitation modifies photosynthetic responses of two model tree species—coniferous Norway spruce and broadleaved sessile oak—to changes in atmospheric CO2 concentration. Saplings were grown under mountainous conditions for two growing seasons at ambient (400 μmol CO2 mol–1) and elevated (700 μmol CO2 mol–1) CO2 concentration. Half were not exposed to precipitation during the summer (June–August). After two seasons of cultivation under modified conditions, basic photosynthetic characteristics including light-saturated rate of CO2 assimilation (Amax), stomatal conductance (GSmax), and water use efficiency (WUE) were measured under their growth CO2 concentrations together with in vivo carboxylation rate (VC) and electron transport rate (J) derived from CO2-response curves at saturating light. An increase in Amax under elevated CO2 was observed in oak saplings, whereas it remained unchanged or slightly declined in Norway spruce, indicating a down-regulation of photosynthesis. Such acclimation was associated with an acclimation of both J and VC. Both species had increased WUE under elevated CO2 although, in well-watered oaks, WUE remained unchanged. Significant interactive effects of tree species, CO2 concentration, and water availability on gas-exchange parameters (Amax, GSmax, WUE) were observed, while there was no effect on biochemical (VC, J) and chlorophyll fluorescence parameters. The assimilation capacity (Asat; CO2 assimilation rate at saturating light intensity and CO2 concentration) was substantially reduced in spruce under the combined conditions of water deficiency and elevated CO2, but not in oak. In addition, the stimulatory effect of elevated CO2 on Amax persisted in oak, but completely diminished in water-limited spruce saplings. Our results suggest a strong species-specific response of trees to reduced summer precipitation under future conditions of elevated CO2 and a limited compensatory effect of elevated CO2 on CO2 uptake under water-limited conditions in coniferous spruce.

Simulating Growth and Competition on Wet and Waterlogged Soils in a Forest Landscape Model

Changes in CO2 concentration and climate are likely to alter disturbance regimes and competitive outcomes among tree species, which ultimately can result in shifts of species and biome boundaries. Such changes are already evident in high latitude forests, where waterlogged soils produced by topography, surficial geology, and permafrost are an important driver of forest dynamics. Predicting such effects under the novel conditions of the future requires models with direct and mechanistic links of abiotic drivers to growth and competition. We enhanced such a forest landscape model (PnET-Succession in LANDIS-II) to allow simulation of waterlogged soils and their effects on tree growth and competition. We formally tested how these modifications alter water balance on wetland and permafrost sites, and their effect on tree growth and competition. We applied the model to evaluate its promise for mechanistically simulating species range expansion and contraction under climate change across a latitudinal gradient in Siberian Russia. We found that higher emissions scenarios permitted range expansions that were quicker and allowed a greater diversity of invading species, especially at the highest latitudes, and that disturbance hastened range shifts by overcoming the natural inertia of established ecological communities. The primary driver of range advances to the north was altered hydrology related to thawing permafrost, followed by temperature effects on growth. Range contractions from the south (extirpations) were slower and less tied to emissions or latitude, and were driven by inability to compete with invaders, or disturbance. An important non-intuitive result was that some extant species were killed off by extreme cold events projected under climate change as greater weather extremes occurred over the next 30 years, and this had important effects on subsequent successional trajectories. The mechanistic linkages between climate and soil water dynamics in this forest landscape model produced tight links between climate inputs, physiology of vegetation, and soils at a monthly time step. The updated modeling system can produce high quality projections of climate impacts on forest species range shifts by accounting for the interacting effects of CO2 concentration, climate (including longer growing seasons), seed dispersal, disturbance, and soil hydrologic properties.

Fossil seed fern Lepidopteris ottonis from Sweden records increasing CO2 concentration during the end-Triassic extinction event

The end-Triassic event (ETE), a short global interval occurring at the end of the Triassic Period (~201.5 Ma), was characterized by climate change, environmental upheaval, as well as widespread extinctions in both the marine and terrestrial realms. It was associated with extensive perturbations of the carbon cycle, principally caused by the volcanic emplacement of the Central Atlantic Magmatic Province in relation to the break-up of Pangea. The correlated change in atmospheric CO2 concentrations (pCO2) can be reconstructed with the stomatal proxy, which utilizes the inverse relationship between stomatal densities of plant leaves (here stomatal index (SI), which is the percentage of stomata relative to epidermal cells) and pCO2. Fossilized Lepidopteris leaves are common and widespread in Triassic strata, thus offering great potential for high-resolution pCO2 reconstructions. A dataset of leaf cuticle specimens belonging to the seed fern species Lepidopteris ottonis from sedimentary successions in Skåne (Scania), southern Sweden, provided the possibility of pCO2 reconstruction at the onset of the ETE. Here, we tested the intra- and interleaf variability of L. ottonis SI, and estimated the pCO2 during the onset of the ETE. Our findings confirm L. ottonis as a valid proxy for palaeo-pCO2, also when using smaller leaf fragments. Importantly, the statistical analyses showed that the SI values of abaxial and adaxial cuticles are significantly different, providing a tool to distinguish between the two sides and select cuticles for analysis. Reconstructed pCO2 increased from ~1000 pre ETE to ~1300 ppm at the onset of the event, a significant increase of ~30% over a relatively short time period. The pCO2 recorded here is similar to previously published estimates, and strongly supports the observed pattern of elevated pCO2 at the onset of the ETE.

The Impact of Climate Change on Wheat, Barley, and Maize Growth Indices in Near-Future and Far-Future Periods in Qazvin Plain, Iran

The current noticeable climate change that has a significant impact on the environment and agricultural systems has become a serious concern for human society. Followed by the industrial activities of the global community and increased concentrations of greenhouse gases in the atmosphere, these changes are still considered as a threat to food safety and the environment. Changes in minimum and maximum temperature, rainfall amounts, and precipitation pattern, changes in CO2 concentrations, and complex interactions between these factors and different crops are studied in the form of different probabilistic scenarios to get a glimpse of the future cultivation situation. Agriculture in Qazvin Plain is based on the water transferred from Taleqan Dam and groundwater. Since today these resources are facing issues like restriction on transfer and draw off, which is because of growth of interest in city dwelling, inappropriate water consumption patterns and over-exploitation, agriculture is sensitive to probable changes in water requirements and it is necessary to predict these changes for better management in the future. This study was carried out to investigate the effect of climate change on growth indices for three crops including wheat, barley, and maize in Qazvin Plain with different possible climate change scenarios, in the form of five large-scale climate models and three greenhouse gas emissions scenarios in 30 years’ time from 2021 to 2050 as well as from 2051 to 2080. Results showed that biomass production, grain yield, and water use efficiency in three crops of wheat, barley, and maize have increased up to 20–40% in future periods in Qazvin region climate. Growing degree-days (GDD) of these three crops have increased by 20%. Transpiration has risen by 10% in wheat and maize; however, it was stable on average in the first period and slightly decreased in the second period in barley. The transpiration coefficient has reduced by 5% for wheat and barley and has increased by 15% for maize. Results are valid as long as the initial growing conditions of these three plants are done as before, and the irrigation scheduling is performed according to the present period in spite of climate change.

Century-scale climatic oscillations during the Last Glacial Maximum revealed by stalagmite isotopic records from Longfugong Cave, China

The isotopic records of two 230Th-dated stalagmites from Longfugong Cave, Mt. Shennongjia, central China, reveal a highly resolved Asian summer monsoon (ASM) history from 29.5 to 14.5 ka BP. The two δ18O records are consistent with other Chinese cave δ18O records, suggesting that our new records are of regional significance. Due to the reservoir mixing of seepage water in the epikarst system, the stalagmite δ18O signals in this cave are more severely muted than those in other caves. Here, we observed that the amplitude of the δ13C variability is approximately twice that of the δ18O signal and can be used as a sensitive proxy of East Asian monsoon climates. First, the two stalagmite δ13C records are consistent with each other on decadal to centennial timescales. Second, there are high correlation coefficients between the δ13C and δ18O signals over shorter timescales. Third, from 25.2 to 19.6 ka BP, six peaks in the δ13C records were identified and are coincident with corresponding warming events in the Greenland ice-core δ18O records, suggesting that strong coupling occurred between the high- and low-latitude northern climates on centennial timescales. Therefore, we propose that atmospheric transmission mechanisms probably played an important role in linking the ASM and Greenland climates on short timescales. A shift in westerly winds associated with variability in the extent of temperature in the North Atlantic likely influenced changes in hydrological and thermal conditions at the cave site, leading to changes in vegetation cover and soil CO2 concentrations above the cave. Therefore, the calcite δ13C records probably had faster and more sensitive responses to rapid climate shifts compared with their related δ18O records.