Global CO_(2) concentration change induced by“trigger-connectors”model,especially since about 24 Ma?A preliminary hypothesis

Background,aim,and scope The tectonic uplift of the Cenozoic Tibetan Plateau has produced a chain effect,which is an excellent location for Earth system science research,and its uplift process,mechanism and environmental effects are the hot spot and frontier of the current research.The“Tibetan Plateau uplift-weathering-CO_(2) concentration-global climate change”model was put forward by Raymo and Ruddiman to interpret the Late Cenozoic climate change.However,there are still some questions suspended,such as does the weathering of the Tibetan Plateau have the ability to control the global climate?How to explain the modern-like global CO_(2) concentration starting at about 24 Ma?Here,a short space was taken to present a brainstorm about the above questions on account of existing geological pieces of evidence.Materials and methods In this paper,we integrate the formation and evolution of the Yangtze River and Pearl River,the origin and development of the Asian inland aridification-monsoon system,the Cenozoic tectonic uplift process of the Tibetan Plateau,and the westerly winds to discuss and analyze the relationship between the Cenozoic CO_(2) concentration changes and the uplift of the Tibetan Plateau and why the CO_(2) concentration similar to the present was formed at about 24 Ma.Results Similar correspondence of the surface uplift history of Xizang,other global mountains,and the declining CO_(2) concentration could support the theory Tibetan Plateau weathering inf luences CO_(2) concentration.Starting from 24 Ma,the most important character was the uplift and erosion of Xizang and Himalaya,collaborating with Ocean Iron Fertilization(OIF)together as an entity to control the atmospheric CO_(2) concentration because the great Asian rivers,Asian monsoons,and westerlies connected Xizang and surrounded seas together through materials transportation.Discussion Paleogeographic reconstructions from 40 Ma to 20 Ma illustrate that the main topographic change occurred in the Andes,Cordillera orogenic belt,and Xizang.We comprise a comprehensive set of evidence from independent data,which correspond temporally with the tipping point(about 24 Ma)of the atmospheric CO_(2) and we noticed that modern-like Asia monsoon,inland aridity,Asian great rivers,and climate zone formed at about 24 Ma and also there are tectonic activities for the Andes and Rockies.We raised the possibility that the modern-like atmospheric CO_(2) concentration at about 24 Ma was caused by the above geological factors.Here the rivers,monsoon,and westerlies are termed as“connectors”.In addition,these Asian rivers originated from Xizang,the monsoon,and inner Asian aridification are strongly a function of the uplift and growth of Xizang,thus,Xizang here is named as“trigger”.The distinct character of“trigger-connectors”model is that this not only takes the monsoon,westerlies,and the global great rivers into consideration but also expands the range which inf luences atmospheric CO_(2) concentration,from local points to a vast area since about 24 Ma,such as from Tibetan Plateau to Asia,including surrounded seas,after about 24 Ma.However,because the opening of the Late Oligocene-Early Miocene Antarctic periphery straits is highly coincident with the onset of modern-like global atmospheric CO_(2) concentration,we are forced to consider that they also had a significant impact on the reduction of atmospheric CO_(2) concentrations at this time.Conclusions“Trigger-connectors”was put forward to explain the Cenozoic CO_(2) variation,especially modern-like global CO_(2) concentration since about 24 Ma.Recommendations and perspectives Here we use the“trigger-connectors”model to explain the formation of modern-like CO_(2) concentrations starting at about 24 Ma,but there are still some problems.The most important premise for the“trigger-connectors”model is the constructed Cenozoic CO_(2) concentration record is reliable,which is the foundation of our hypothesis.In the future,potential improvements should focus on topographic reconstructions of Xizang and the global mountains.Here we have concentrated on Xizang in the considered timeslices but still,pay less attention to other global orogenic belts.Collaborations with geologist experts in those regions could provide valuable feedback to evaluate their potential role of them in CO_(2) evolution.What is more,considerable progress may be achieved with the addition and consideration of more and new geological data.

RELATIONSHIPS OF STARCH CONCENTRATION WITH SPECIFIC LEAF WEIGHT AND MINERAL CONCENTRATIONS IN POTATO LEAVES UNDER VARIED CO_2 AND TEMPERATURE

Foliar concentrations of starch and major nutrients N, P, K, Ca, and Mg along with specific leaf weight (SLW) were determined in the potato (Solanun tuberosum L.) cvs "Denali", "Norland "'and "Russet Burbank" grown for 35 days under the CO2 concentrations of 500, 1 000, 1 500 and 2 000 mol mol-1 at both 16 and 20℃ air temperature. The starch concentration, pooled from the three cultivars, increased with increasing CO2 concentration at both 16 and 20℃,, and was consistently higher at 16℃ than at 20℃. The SLW (g m-2) was positively related to the foliar starch concentration on the basis of leaf area or dry weight. The concentrations of N, P, Ca, and Mg in leaves were negatively related to starch concentration under 14% starch on a dry weight basis. Above 14%, there was no significant relationship between nutrient and starch concentrations . The similar patterns were seen when the SLW and nutrient concentrations were expressed on a starch-free basis. In contrast, the leaf concentration of K was not closely related to the starch concentration. The results indicated that the changes in SLW and concentrations of N, P, Ca, and Mg in potato leaves only partially resulted from the changed starch concentration.

Recent progress of green sorbents-based technologies for low concentration CO_(2) capture

The increased concentration of CO_(2) due to continuous breathing and no discharge of human beings in the manned closed space,like spacecraft and submarines,can be a threat to health and safety.Effective removal of low concentration CO_(2) from the manned closed space is essential to meet the requirements of long-term space or deep-sea exploration,which is an international frontier and trend.Ionic liquids(ILs),as a widespread and green solvent,already showed its excellent performance on CO_(2) capture and absorption,indicating its potential application in low concentration CO_(2) capture.In this review,we first summarized the current methods and strategies for direct capture from low concentration CO_(2) in both the atmosphere and manned closed spaces.Then,the multi-scale simulation methods of CO_(2) capture by ionic liquids are described in detail,including screening ionic liquids by COSMO-RS methods,capture mechanism by density functional theory and molecular dynamics simulation,and absorption process by computational fluid dynamics simulation.Lastly,some typical IL-based green technologies for low concentration CO_(2) capture,such as functionalized ILs,co-solvent systems with ILs,and supported materials based on ILs,are introduced,and analyzed the subtle possibility in manned closed spaces.Finally,we look forward to the technology and development of low concentration CO_(2) capture,which can meet the needs of human survival in closed space and proposed that supported materials with ionic liquids have great advantages and infinite possibilities in the vital area.

Raman and infrared spectroscopic quantification of the carbonate concentration in K_(2)CO_(3)aqueous solutions with water as an internal standard

Carbonate-bearing fluids widely exist in different geological settings,and play important roles in transporting some elements such as the rare earth elements.They may be trapped as large or small fluid inclusions(with the size down to<1μm sometimes),and record critical physical-chemical signals for the formations of their host minerals.Spectroscopic methods like Raman spectroscopy and infrared spectroscopy have been proposed as effective methods to quantify the carbonate concentrations of these fluid inclusions.Although they have some great technical advantages over the conventional microthermometry method,there are still some technical difficulties to overcome before they can be routinely used to solve relevant geological problems.The typical limitations include their interlaboratory difference and poor performance on micro fluid inclusions.This study prepared standard ion-distilled water and K_(2)CO_(3)aqueous solutions at different molarities(from 0.5 to 5.5 mol/L),measured densities,collected Raman and infrared spectra,and explored correlations between the K_(2)CO_(3)molarity and the spectroscopic features at ambient P-T conditions.The result confirms that the Raman O-H stretching mode can be used as an internal standard to determine the carbonate concentrations despite some significant differences among the correlations,established in different laboratories,between the relative Raman intensity of the C-O symmetric stretching mode and that of the O-H stretching mode.It further reveals that the interlaboratory difference can be readily removed by performing one high-quality calibration experiment,provided that later quantifying analyses are conducted using the same Raman spectrometer with the same analytical conditions.Our infrared absorption data were collected from thin fluid films(thickness less than~2μm)formed by pressing the prepared solutions in a Microcompression Cell with two diamond-II plates.The data show that both the O-H stretching mode and the O-H bending mode can be used as internal standards to determine the carbonate concentrations.Since the IR signals of the C-O antisymmetric stretching vibration of the CO32ion,and the O-H stretching and bending vibrations from our thin films are very strong,their relative IR absorbance intensity,if well calibrated,can be used to investigate the micron-sized carbonate-bearing aqueous fluid inclusions.This study establishes the first calibration of this kind,which may have some applications.Additionally,our spectroscopic data suggest that as the K_(2)CO_(3)concentration increases the aqueous solution forms more large water molecule clusters via more intense hydrogen-bonding.This process may significantly alter the physical and chemical behavior of the fluids.

Spatial variations in daily average CO_2 concentrations above wetland surface of Xianghai National Nature Reserve, China

Horizontal and vertical variations of daily average CO 2 concentration above the wetland surface were studied in Xianghai National Nature Reserve of China in August, 2000 The primary purpose was to study spatial distribution characteristics of CO 2 concentration on the four levels of height(0 1 m, 0 6 m, 1 2 m and 2 m) and compare the differences of CO 2 concentration under different land covers. Results showed that daily average CO 2 concentration above wetland surface in Xianghai National Natural Reserve was lower than that above other wetlands in northeast China as well as the worldwide average, suggesting that Xianghai wetland absorbed CO 2 in August and acted as “sink” of CO 2 The horizontal variations on the four levels of height along the latitude were distinct, and had the changing tendency of “decreasing after increasing” with the increase of height. The areas with obvious variations were consistent on different levels of height, and those with the highest variations appeared above surface of shore, sloping field, Typha wetland and Phragmites wetland; the vertical variations were greatly different, with the higher variations in Phragmites wetland and Typha wetland, and the lands near the shore and the sloping field with the lower variations. Spatial variations of daily average CO 2 concentrations above wetland surface were affected by surface qualities and land covers.

Spatial Inhomogeneity of Atmospheric CO_(2) Concentration and Its Uncertainty in CMIP6 Earth System Models

This paper provides a systematic evaluation of the ability of 12 Earth System Models(ESMs)participating in the Coupled Model Intercomparison Project Phase 6(CMIP6)to simulate the spatial inhomogeneity of the atmospheric carbon dioxide(CO_(2))concentration.The multi-model ensemble mean(MME)can reasonably simulate the increasing trend of CO_(2) concentration from 1850 to 2014,compared with the observation data from the Scripps CO_(2) Program and CMIP6 prescribed data,and improves upon the CMIP5 MME CO_(2) concentration(which is overestimated after 1950).The growth rate of CO_(2) concentration in the northern hemisphere(NH)is higher than that in the southern hemisphere(SH),with the highest growth rate in the mid-latitudes of the NH.The MME can also reasonably simulate the seasonal amplitude of CO_(2) concentration,which is larger in the NH than in the SH and grows in amplitude after the 1950s(especially in the NH).Although the results of the MME are reasonable,there is a large spread among ESMs,and the difference between the ESMs increases with time.The MME results show that regions with relatively large CO_(2) concentrations(such as northern Russia,eastern China,Southeast Asia,the eastern United States,northern South America,and southern Africa)have greater seasonal variability and also exhibit a larger inter-model spread.Compared with CMIP5,the CMIP6 MME simulates an average spatial distribution of CO_(2) concentration that is much closer to the site observations,but the CMIP6-inter-model spread is larger.The inter-model differences of the annual means and seasonal cycles of atmospheric CO_(2) concentration are both attributed to the differences in natural sources and sinks of CO_(2) between the simulations.

CO_2 CONCENTRATION AND FLUX NEAR GROUND IN MARSH OF THE SANJIANG PLAIN OF NORTHEAST CHINA

There is limited information available on CO2 concentration and flux over marsh. The objective of this work was to characterize CO2 concentration and flux within and above marsh plant (Cares lasiocarpa Ehrh. and C. pseudoucuaica F. Schm) canopy at heights 0. 5, 1. 0 and 1. 5 m.CO2 concentration was measured sequentially every 3 bars by using an infrared gas analyzer. Soil and air temperature, wind speed, net radiation and soil heat flux were also measured simultaneously. Extremely drily minimum and maximum CO2 concentration rangal from 250 to 754 μmd/mol for the 4-year work. The typical minimum and maximum values ranged from 314 to 464 μmol/mol at the height of marsh plant (about 0. 5 m) during the fruiting perioed and mature date. The seasonal changes in CO2 concentration show that the minimum CO2 concentration occurred in the fruiting period and mature date, and both of their minimum values were 314 μmol/mol. This illustrates that CO2 consumed by photosynthesis was stable during the period. The flux of CO2 can be thought as a turbulent diffusion phenomenon. By micrometeorological methods, the diurnal CO2 fluxes were measured in the flowering peried, fruiting period, early mature date, late mature date and yellow-ripe stage. Their values were -0. 18, 38. 15,24. 13, 10. 9 and 4. 91 μmol/mol respectively.

Effect of elevated ambient CO_2 concentration on water use efficiency of Pinus sylvestriformis

Pinus Syvestfiformis is an important species as an indicator of global climate changes in Changbai Mountain, China. The water use efficiency (WUE) of this species (11 -year old ) was studied on response to elevated Co, concentration at 500±μLL' L-1 by directly injecting CO2 into the canopy under natural condition in 1998-1999. The results showed that the elevated Co, concentration reduced averagely stomatal opening, stomatal conductance and stomatal density to 78%, 80% and 87% respectively, as compared to normal ambient. The elevated Co, reduced the transpiration and enhances the water use efficiency (WUE) of plant.

Effect of Different High CO_2 Concentrations on the Development of 2-cell Mouse Embryos in vitro

Objective To investigate effects of different high CO_2 concentrations on the development of 2-cell mouse embryos in vitro Methods At levels of 5% CO_2 (control group), 5.7% CO_2, 6.0% CO_2 and 15% CO_2, embryos were incubated in drops with CZB medium, respectively, and the drops were covered by paraffin oil which was treated with three-distilled water. In addition, at the level of 15% CO_2, there were another two groups, in which paraffin oil was treated with phosphate-buffered saline (PBS) solution or the drops were uncovered. The development of embryos in all stages was noted. Results The developmental rates of blastocysts in five experimental groups were significantly lower than that of the control group (P<0.01). At the level of 5.7% CO_2, the developmental rate of blastocysts was 4.3%, and those of other experimental groups were 0. At the levels of 5.7% and 6.0% CO_2, embryos were blocked in the 2-cell or the 4-cell stage, and no significant difference was showed between the two groups (P>0.05). At the level of 15% CO_2, 15% embryos developed in the 4-cell stage with irregular blastomere and degenerated quickly in the group which paraffin oil was treated with distilled water; 2.2% embryos developed in the 4-cell stage in the group which paraffin oil was treated with PBS and the rest stagnated in the 2-cell stage. Conclusions High CO_2 concentrations had toxic effect on the in vitro development of 2-cell mouse embryos, and was responsible for the inhibition of the embryos. It is important for the development of embryos in vitro to detect strictly CO_2 concentration.

Spatio-temporal variation of soil CO_(2) concentration in Loess Area of northwestern Shanxi Province,China

CO_(2) released by soil serves as an important link between terrestrial ecosystems and atmospheric CO_(2), whose small chang‐es may significantly affect the global carbon cycle. In order to reveal the spatio-temporal variations of CO_(2) concentrations in deep loess, this paper takes Qingliangsi Gully watershed in northwestern Shanxi Province, China as an example to sys‐tematically study soil CO_(2)concentration and its spatio-temporal variations and carbon sink significance under different watershed locations and different land use types. Results show that: (1) The release potential of the loess soil is larger in the depth range of 2 m, which is much more likely to be the CO_(2) release area. (2) Grassland and forest are more advanta‐geous in terms of soil microbial activity and soil carbon reserve compared with farmland. In addition, the change of land use type from farmland to grassland can increase soil organic carbon reserve, which is of far-reaching significance to the global carbon cycle. This is especially true in an area like the Loess Plateau with densely covered hills, gullies, and serious soil erosion in an area of 64×104 km2. (3) In the study area, the diurnal concentration of soil CO_(2) at different depths shows a weak "high-low-high-low" trend from 08:00 to 07:00 next day;and in deep soil it has a lag time compared with the daily change of temperature, generally about 4−12 h, which may be caused largely by the more compact loess structure. It is worth pointing out that the Loess Plateau in China, with a thickness of the loess of tens to hundreds of meters, has the most abundant soil resources in the world, and also stores a large amount of terrestrial soil carbon, which carries the hope of promoting the research of global carbon cycle.

大气CO_(2)浓度升高背景下秸秆还田对小麦土壤氮矿化的影响

为探讨小麦土壤氮矿化对CO_(2)浓度升高、秸秆还田及其交互作用的响应,本研究利用人工控制气候室设置2种CO_(2)浓度处理CK(CO_(2)浓度为400μmol·mol^(−1))、EC(CO_(2)浓度为600μmol·mol^(−1)),3种秸秆处理:秸秆不还田(R)、秸秆掺入(I)、秸秆覆盖(M),测定小麦土壤理化性质、碳氮相关酶活性;通过为期35 d的室内培养试验,分析土壤硝态氮、铵态氮含量动态变化和净氮矿化速率等。结果表明,培养35 d后与秸秆不还田相比,两种秸秆还田方式均增加了土壤碳氮有效性,秸秆掺入和秸秆覆盖处理土壤净硝化速率在两种CO_(2)浓度处理下分别平均增加0.76和0.55 mg·kg^(-1)·d^(-1)。3种秸秆处理方式中,以秸秆掺入土壤净矿化速率最大;秸秆覆盖土壤净氨化速率较低,导致其净矿化速率低于秸秆掺入。与CK相比,CO_(2)浓度升高使土壤无机氮含量平均下降8.1%,土壤氮矿化量平均降低14.98 mg·kg^(-1)。与CK相比,CO_(2)浓度升高下秸秆还田使土壤无机氮含量增加74.2 mg·kg^(-1),主要是由于土壤硝态氮含量增加了73.8 mg·kg^(-1),导致土壤净硝化速率提高了0.57 mg·kg^(-1)·d^(-1);CO_(2)浓度升高下土壤净氨化速率整体下降,其中秸秆覆盖下降幅度较大,导致其净氮矿化速率低于CK。综上,CO_(2)浓度升高下秸秆还田增加了土壤氮的可利用性,其中秸秆覆盖提高了土壤氮固持能力,减少了氮素淋失,秸秆掺入增加了土壤氮矿化,可提供更多无机氮以供作物利用。本研究为未来气候变化背景下选择适宜秸秆还田措施以维持土壤供氮潜力提供了理论依据和技术支持。

大气CO_(2)浓度升高背景下优化施氮对淹水稻田CH4排放的影响

为探讨未来气候变化条件下,合理管理氮肥以充分协调水稻产量与温室气体排放量之间的矛盾,实现低碳排放并保持水稻产量,本研究探讨了大气CO_(2)浓度升高120μmol·mol^(-1)与氮肥减施40%对淹水稻田水稻生产及CH4排放的影响及机理。利用开顶式气室(OTC)组成的CO_(2)浓度自动调控平台设置4个处理,即环境CO_(2)浓度+施氮250 kg·hm^(-2)(CK)、大气CO_(2)浓度升高120μmol·mol^(-1)+施氮250 kg·hm^(-2)(C+)、环境CO_(2)浓度+施氮150 kg·hm^(-2)(N-)、大气CO_(2)浓度升高120μmol·mol^(-1)+施氮150 kg·hm^(-2)(C+N-),分析了稻田CH4累积排放量(CAC)、水稻生物量及产量、土壤理化性质及酶活性等指标。结果表明:与CK处理相比,C+处理使CAC/产量显著提高了16.93%,N-处理使CAC/产量显著降低了13.33%,C+N-处理使CAC/产量降低了7.89%,但不显著;N-处理在一定程度上削弱了C+处理对CAC、CAC/产量、水稻生物量、土壤可溶性有机碳含量的促进作用;逐步回归分析表明,基于可溶性有机碳和硝态氮含量及土壤脲酶活性的线性模型,可解释稻田CH4累积排放64%的变异。综上,在大气CO_(2)浓度升高条件下,氮肥减施可通过影响土壤碳、氮基质及土壤脲酶活性来调节稻田CH4排放。

基于上海高层建筑观测冬季大气CO_(2)/CH_(4)垂直变化

采用便携式温室气体分析仪于2021年12月6日~2022年3月31日在上海中心大厦255和500m高度以及浦东新区环境监测站25m高度连续观测大气CO_(2)和CH_(4)浓度.结果表明:(1)城市中不同高度上温室气体的日变化趋势存在差异,25m高度CO_(2)和CH_(4)浓度白天低夜间高,255和500m高度的浓度则白天高夜间低.各高度处CO_(2)和CH_(4)浓度变化都明显受大气边界层高度的影响,因此城市内部温室气体浓度垂直观测中观测点高度设置要充分考虑城市大气边界层的变化特征.(2)CO_(2)和CH_(4)浓度的垂直差异受到人为活动以及气象等条件的影响,可以指征城市大气CO_(2)和CH_(4)浓度增强的局地和区域贡献.(3)各高度处(25,255,500m)CO_(2)浓度与CH_(4)浓度均显著相关,但观测高度越高所代表的浓度贡献源区越大,多种排放源的干扰使得温室气体之间的同源性变差,导致其相关性随着高度增加而降低.城市温室气体浓度的垂直观测提供了从水平方向上无法获得的独特信息,因此有必要在城市开展立体化的温室气体监测,以便更好地捕捉大气温室气体浓度的变化,从而服务于城市碳减排政策.

大气CO_(2)浓度缓增、骤增和不同施氮水平对稻田CH4排放的影响

为探究大气CO_(2)浓度缓增、骤增和不同施氮水平对稻田CH_(4)排放的影响,基于CO_(2)浓度自动调控平台开展水稻试验,以“南粳9108”为试验品种,采用静态箱-气相色谱法测定CH_(4)通量。在背景大气CO_(2)浓度(CK)的基础上,设置CO_(2)浓度缓增(C_(1)处理,从2016年开始逐年增加40μmol·mol^(-1),至2018年增加120μmol·mol^(-1))和骤增(C_(2)处理,CO_(2)浓度每年均增加200μmol·mol^(-1))处理;在常规施氮量(N 1处理,25 g·m^(-2))的基础上设置氮肥减施处理(N_(2)处理,15 g·m^(-2))。结果表明,CO_(2)浓度缓增、骤增和不同施氮量均没有改变稻田CH_(4)通量的季节变化规律,总体上呈现先增加后减小的趋势。在整个生育期,CO_(2)浓度缓增、骤增对稻田单位产量CH_(4)排放量无显著影响。在C_(2)条件下,与N 1处理相比,N_(2)处理水稻产量显著降低45.2%(P=0.037),同时稻田单位产量CH_(4)排放量显著增加63.3%(P=0.008)。综上所述,随着CO_(2)浓度升高,氮肥减施至15 g·m^(-2)会减少水稻产量,同时增加稻田单位产量CH_(4)排放。

作物-内生微生物响应CO_(2)浓度升高与干旱胁迫的作用机制研究进展

全球变暖、二氧化碳(CO_(2))浓度升高和局部地区干旱加剧等环境变化对作物生长发育及产量造成的影响日趋明显。内生微生物是一类与宿主植物形成互利共生机制的微生物,由于其长期生活在植物体的特殊环境中,对作物的生长发育和抗逆性具有重要作用,两者的共生关系会直接影响作物对环境变化的响应。本文主要综述作物-内生微生物共生系统及其在CO_(2)和干旱胁迫下对作物生理过程的调控,探讨了作物内生微生物群落的多样性以及促生效果、抑菌作用、抗逆能力,并重点关注了作物-内生微生物系统如何提高环境的耐受特性。具体而言,内生微生物可以通过提高宿主的气孔调节能力、增加根系吸收水分和养分的能力等方式,帮助作物适应CO_(2)浓度升高和干旱胁迫,从而减小环境变化对作物生长的负面影响,提高作物产量。此外,内生微生物还可以激活宿主的防御系统,提高其对病原体的抵抗能力,从而减轻病害对作物的影响。未来的研究应关注作物-内生微生物共生系统在不断升高的CO_(2)浓度和干旱复合胁迫下的响应机制,以提高作物对极端环境变化的抗性,为作物抗逆性育种提供新的思路和策略。

CO_(2)浓度缓增对冬小麦田N_(2)O排放的影响

为研究CO_(2)浓度缓增对冬小麦田N_(2)O排放的影响,利用由开顶式气室(OTC)组成的CO_(2)浓度自动调控平台,扬麦22号为供试材料开展田间试验。将大气CO_(2)浓度作为对照(CK),设置CO_(2)浓度缓增处理C_(80)(CO_(2)浓度缓慢增加80μmol/mol)和C_(120)(CO_(2)浓度缓慢增加120μmol/mol)。结果表明,CO_(2)浓度缓增处理没有改变小麦田N_(2)O排放通量的季节性变化特征。在2017-2018年冬小麦生长季,CK、C_(80)处理土壤N_(2)O累积排放量分别为(25.49±3.33) mg/m^(2)、(26.83±3.21) mg/m^(2);2018-2019年冬小麦生长季,CK、C_(120)处理土壤N_(2)O累积排放量分别为(113.06±2.66) mg/m^(2)、(121.20±9.28) mg/m^(2)。在2017-2018年冬小麦生长季,CK、C_(80)处理土壤-冬小麦系统N_(2)O累积排放量分别为(25.99±1.39) mg/m^(2)、(29.83±4.20) mg/m^(2)。各生育期土壤N_(2)O累积排放量与冬小麦地上部分生物量呈极显著正相关(P<0.01),土壤-冬小麦系统N_(2)O累积排放量与冬小麦地上部分生物量呈极显著正相关(P<0.01)。

不同CO_(2)浓度和氮肥水平对稻田呼吸速率的影响

为研究不同CO_(2)浓度和氮肥水平对稻田呼吸速率的影响,利用12个开顶式气室开展田间试验,CO_(2)浓度设置对照(CK,自由大气CO_(2)浓度)、CO_(2)浓度比CK增加120μmol·mol-1(C1)和200μmol·mol-1(C2)3个水平,氮肥设置低氮(N1,15 g·m^(-2))和常规氮肥(N2,25 g·m^(-2))2个水平,试验共6种处理。结果表明:在相同施氮水平下,在灌浆期和蜡熟期,C1N1比CKN1处理的呼吸速率分别下降了23.4%(P=0.045)和49.1%(P=0.010);在抽穗期和灌浆期,C2N2比CKN2处理的呼吸速率分别升高了12.3%(P=0.009)和16.8%(P=0.047)。同一CO_(2)浓度下,不同施氮水平处理的呼吸速率表现为N2>N1,且在拔节期和抽穗期达到显著水平,在灌浆期达到极显著水平;其中在灌浆期和蜡熟期,C1N1比C1N2处理的呼吸速率分别下降了31.1%(P=0.004)和42.7%(P=0.010)。研究表明,大气CO_(2)浓度升高对稻田呼吸速率的影响因生育时期而异,氮肥减施可以降低稻田呼吸速率及CO_(2)累积释放量。

大气CO_(2)浓度升高背景下冬小麦冠层光谱特征和地上生物量估算

本研究旨在探究大气CO_(2)浓度升高对冬小麦全生育时期冠层光谱特征的影响,并基于筛选的敏感波段建立地上生物量(AGB)与光谱参数的定量关系。为此,在2021—2022年的冬小麦生长季,利用开放式CO_(2)富集系统(Mini-FACE),设定大气CO_(2)浓度(ACO_(2),(420±20)μL L^(–1))和高CO_(2)浓度(ECO_(2),(550±20)μL L^(–1))两个处理水平,分析了高CO_(2)浓度下光谱特征变化,基于连续投影算法(SPA)、逐步多元线性回归(SMLR)和偏最小二乘法回归(PLSR)筛选AGB敏感波段并构建估算模型。结果表明:CO_(2)浓度升高使冬小麦拔节期和开花期AGB显著增加。红边和近红边反射率及红边面积在拔节期增加,在开花期和灌浆期降低,蓝边、黄边和红边位置在不同生育时期均发生移动;AGB的敏感光谱波段主要分布在红边和近红边区域,CO_(2)浓度升高缩小了AGB敏感波段范围,但不影响AGB的估算;AGB的SMLR和PLSR模型均取得了较高的估算精度(R^(2)>0.8),其中SMLR模型中的R_(799′)、D_(y)、SD_(y)和PRI等特征参数与AGB显著相关,R^(2)为0.866。PLSR模型(R^(2)>0.9)在估算精度和稳定性上优于SMLR模型。本研究可为未来高CO_(2)浓度下冬小麦生长发育的遥感监测提供理论基础和技术方法。

基于激光吸收光谱的CO/CO_(2)/H_(2)S浓度同步在线测量研究

CO、CO_(2)、H_(2)S是燃煤锅炉炉内气氛重要组成部分,其浓度不仅能够反映燃烧工况,还可作为水冷壁高温腐蚀程度判断依据,因此实现CO、CO_(2)、H_(2)S浓度的准确测量意义重大。首先采用波长调制-直接吸收(WM-DAS)方法结合约40 m长光程Herriott池,在室温低压下,开展不同CO/CO_(2)浓度配比下三种气体吸收率同步测量实验,结果表明三种气体的吸收率测量值与理论计算值相近,相对误差在6.82%以内,测量结果可靠性较高;然后对不同浓度CO/CO_(2)(0~2000μL·L^(-1))、H_(2)S(0~20μL·L^(-1))进行动态测量,结果表明,测量系统对三种组分浓度变化的响应具有较好的线性度。

大气CO_(2)浓度对萝卜生长及氮磷钾养分吸收的影响

【目的】探明CO_(2)浓度升高是否改变土壤养分状况进而影响萝卜生长及养分吸收,为大气CO_(2)浓度升高条件下萝卜合理施肥方式提供理论依据。【方法】以糖晶萝卜为试验材料,设置4个CO_(2)浓度水平:C_(0)(大气CO_(2)浓度)、C_(1)(C_(0)+33%C_(0))、C_(2)(C_(0)+67%C_(0))和C_(3)(C_(0)+100%C_(0)),研究不同CO_(2)浓度对萝卜生长、氮磷钾养分吸收及土壤养分的影响。【结果】与C_(0)相比,C_(1)、C_(2)和C_(3)处理萝卜地上生物量增加0.52%~34.68%,地下生物量增加63.00%~100.46%,总生物量增加37.83%~67.61%,CO_(2)浓度升高促进萝卜生长和干物质积累,且C_(2)处理最适宜;CO_(2)浓度升高降低萝卜地下氮磷和地上钾含量,但植株氮磷钾积累量分别增加39.77%~43.30%、2.08%~17.27%和38.38%~72.26%。土壤硝态氮、有效磷和速效钾在CO_(2)浓度升高条件下分别降低29.62%~34.20%、10.03%~14.12%和1.92%~16.62%。植株氮和钾积累量与植株干重呈显著正相关,与土壤硝态氮、有效磷和速效钾呈显著负相关。【结论】CO_(2)浓度升高通过增加脲酶和磷酸酶活性改善土壤肥力,促进植株氮磷钾养分吸收,进而提高萝卜产量。在大气CO_(2)浓度升高条件下,应合理增施氮肥、磷肥、钾肥,且氮肥施用量应大于磷肥和钾肥。