[Spatiotemporal Evolution Characteristics of Carbon Sources and Carbon Sinks and Carbon Balance Zoning in the Yangtze River Delta Region].

Mastering the spatiotemporal evolution laws of carbon sources and sinks is of great significance to promote the coordinated development of regional low-carbon, improve the science of carbon reduction and sink increase policies, and realize the goal of "double carbon." Taking 41 cities in the Yangtze River Delta Region as the research object, this study analyzed the spatiotemporal evolution characteristics of carbon sources and sinks in the Yangtze River Delta Region from 2000 to 2020 and conducted the carbon balance zoning. The results were as follows： ① The carbon emissions increased rapidly in the Yangtze River Delta Region from 2000 to 2011 but with some fluctuations after 2011. Carbon sinks increased slowly in the Yangtze River Delta Region from 2000 to 2020. The regional differences in carbon emissions and carbon sinks were significant, and the spatial pattern was relatively stable. ② The carbon compensation rate in the Yangtze River Delta Region showed a downward trend, and the carbon productivity, energy utilization efficiency, and carbon ecological support capacity were constantly enhanced. Interregional differences were the main source of carbon compensation rate in the Yangtze River Delta Region. Both the carbon compensation rate and carbon ecological support coefficient showed a spatial pattern of "high in the west and low in the east, high in the south and low in the north." The areas with high carbon economy contributive coefficient were concentrated in the central and southern areas of the Yangtze River Delta regions, and the areas with low carbon economy contributive coefficient were concentrated in Anhui Province. ③ Based on the carbon economy contributive coefficient and the carbon ecological support coefficient, cities in the Yangtze River Delta Region were classified into low-carbon maintenance areas, economic development areas, carbon sink development areas, and comprehensive optimization areas. Recommendations were proposed for each category of cities in order to promote the coordinated development of regional low-carbon and realize the goal of "double carbon".

Evolution characteristics and performance evaluation of extended end-plate joints with single and double side connections under cyclic loading.

Experimental studies were conducted on four extended end-plate joints subjected to cyclic loading at the column top, investigating the evolving patterns of the joints' mechanical performance. The paper provides a detailed analysis and discussion of the test joints' failure modes, ductility, stiffness degradation, and energy dissipation capacity. The Mann-Kendall (M - K) trend analysis tool was applied to the mechanical response curves, identifying key performance evolution points (evolution initiation point P and overall yield point Q). The trends in bolt forces, deformations, and strains at critical joints were effectively validated, revealing the transition of the energy system from quantitative to qualitative changes and the component's failure process from stability to instability. Additionally, based on the experimental joints' hysteresis curves and energy dissipation capacity, a theoretical hysteresis model was established to predict the joint's hysteresis curve and cumulative dissipated energy accurately. According to EC3 requirements, joints were classified as partially rigid connections. The experimental results of the initial rotational stiffness and plastic moment were further used to evaluate the calculated values in existing standards EN 1993-1-8, ANSI/AISC 358-16, and GB 51017-2017. The results indicate that extended end-plate connections possess sufficient strength, joint rotational stiffness, ductility, and energy dissipation capacity, making them suitable for seismic moment frames.

Research on the evolution characteristics, driving mechanisms and multi-scenario simulation of habitat quality in the Guangdong-Hong Kong-Macao Greater Bay based on multi-model coupling.

Since the 20th century, the global urbanization has led to a series of pollution issues, posing a severe threat to the habitat quality of human habitat. The quality of habitat determines whether ecosystems can provide suitable living conditions for humans and other species. Therefore, systematic study of the habitat quality is essential for the maintenance of sustainable development. In this study, we coupled models such as SD, InVEST and PLUS with a series of indicators to analyze the characteristics of land cover and habitat quality evolution in the Guangdong-HongKong-Macao Greater Bay Area (GBA) from 2000 to 2020 and deconstruct the driving mechanisms of habitat quality. Then simulate the evolution of land cover and habitat quality under different scenarios in 2030. The results show that: 1) Over the historical research period, the GBA exhibited "rapid expansion of artificial surfaces and rapid shrinkage of ecological land". Artificial surfaces increased by approximately 4878.95km2,while ecological land, such as agricultural land, decreased by about 3095.93km2.2) The degradation of habitat quality gradually accelerated and the habitat quality was characterized by "stepwise decline from the periphery to the interior", which was directly related to the land cover changes brought about by the topographic gradient effect in the Bay Area.3) Pollution control driven by environmental investments has had a moderating effect on habitat degradation, but it has not been able to change the overall degradation trend. 4) Scenario analysis suggests that future habitat quality in the GBA will degrade to a certain extent due to the impact of artificial surface expansion. We deduce that this will affect the structure of the city's ecological network as well as the conservation function of the ecological zones. This study provides a scientific basis for understanding the historical and future trends of habitat quality in the GBA, offering new insights into the intrinsic driving mechanisms of habitat quality. It also provides a theoretical support for relevant authorities to undertake sustainable development initiatives.

Zabramski classification in predicting the occurrence of symptomatic intracerebral hemorrhage in sporadic cerebral cavernous malformations.

OBJECTIVE: The authors aimed to investigate the evolutionary characteristics of the Zabramski classification of cerebral cavernous malformations (CCMs) and the value of the Zabramski classification in predicting clinical outcome in patients with sporadic CCM. METHODS: This retrospective study consecutively included cases of sporadic CCM that had been untreated from January 2001 through December 2021. Baseline and follow-up patient information was recorded. The evolution of the Zabramski classification of a sporadic CCM was defined as the initial lesion type changing into another type for the first time on MRI follow-up. The primary outcome was the occurrence of a hemorrhage event, which was defined as a symptomatic event with radiological evidence of overt intracerebral hemorrhage. RESULTS: Among the 255 included cases, 55 (21.6%) were classified as type I CCM, 129 (50.6%) as type II CCM, and 71 (27.8%) as type III CCM, based on initial MRI. During a mean follow-up of 58.8 ± 33.6 months, 51 (20.0%) patients had lesion classification transformation, whereas 204 (80.0%) patients maintained their initial type. Among the 51 transformed lesions, 29 (56.9%) were type I, 11 (21.6%) were type II, and 11 (21.6%) were type III. Based on all follow-up imaging, of the initial 55 type I lesions, 26 (47.3%) remained type I and 27 (49.1%) regressed to type III because of hematoma absorption; 91.5% of type II and 84.5% of type III lesions maintained their initial type during MRI follow-up. The classification change rate of type I lesions was statistically significantly higher than those of type II and III lesions. After a total follow-up of 1157.7 patient-years, new clinical hemorrhage events occurred in 40 (15.7%) patients. The annual cumulative incidence rate for symptomatic hemorrhage in all patients was 3.4 (95% CI 2.5-4.7) per 100 person-years. Kaplan-Meier survival analysis showed that the annual cumulative incidence rate for symptomatic hemorrhage of type I CCM (15.3 per 100 patient-years) was significantly higher than those of type II (0.6 per 100 patient-years) and type III (2.3 per 100 patient-years). CONCLUSIONS: This study suggests that the Zabramski classification is helpful in estimating clinical outcome and can assist with surgical decision-making in patients with sporadic CCM.

[Evolution Characteristics of Soil Active Organic Carbon and Carbon Pool Management Index Under Vegetation Restoration in Karst Area].

Vegetation restoration affects the carbon cycle of terrestrial ecosystems by changing the rate of carbon input and conversion. In order to explore the evolution characteristics of soil active organic carbon components and carbon pool management index during vegetation restoration in karst areas, the soil of a grassland sequence(5, 10, 15, and 20 a), shrub sequence(5, 10, 15, and 20 a), and garden sequence(5, 10, and 15 a) in a karst area was taken as the research object, and the adjacent farmland was taken as the control(CK). The effects of different vegetation restoration years on the evolution of soil organic carbon(SOC), readily oxidizable organic carbon(ROC333, ROC167, and ROC33 were all soil active organic carbon that could be oxidized by 333, 167, and 33 mmol·L-1 KMnO4), microbial biomass carbon(MBC), dissolved organic carbon(DOC), and carbon pool management index(CPMI) were analyzed. The results showed that compared with that of CK, the average grassland, shrub, and garden SOC contents in the 0-40 cm soil layer increased by 70.77%, 114.40%, and 50.17%, respectively. In the 0-20 cm soil layer, with the increase in restoration years, the SOC content of the grassland sequence and garden sequence increased first and then decreased, and that of the shrub sequence increased first, then decreased, and then increased again. ROC333, ROC167, and ROC33 were consistent with the SOC change trend of the corresponding sequence. In the 20-40 cm soil layer, the change trend of ROC333, ROC167, and ROC33 of each sequence was inconsistent with the SOC of the corresponding sequence. In the 0-40 cm soil layer, the MBC content of the grassland sequence decreased first, then increased, and then decreased, and the maximum value of MBC in each soil layer was in G15. The shrub sequence in the 0-10 cm soil layer increased first, then decreased, and then increased, and in the 10-40 cm soil layer it increased first and then decreased. The garden sequence increased first and then decreased in the 0-30 cm soil layer and gradually increased in the 30-40 cm soil layer. Kos of the three sequences decreased first, then increased, and then decreased, whereas L and LI showed the opposite of Kos. CPI increased first and then decreased; the CPMI of the grassland and garden sequences increased first and then decreased, whereas the CPMI of the shrub sequence increased first, then decreased, and then increased again. The contents of SOC, ROC333, ROC167, ROC33, and MBC and the annual growth of Kos were shrub>grassland>orchard, and the annual growth of DOC and CPMI were orchard>grassland>shrub. The contents of SOC and its components in the three sequences decreased with the increase in soil layer and had obvious surface aggregation. Redundancy analysis showed that alkali-hydrolyzable nitrogen(AN) was the main environmental factor affecting soil active organic carbon components and soil organic carbon pool under the vegetation restoration in the karst area. In summary, soil active organic carbon components and CPMI evolved with vegetation restoration years. Different vegetation restorations could increase the content of SOC and its components in karst areas to a certain extent, and shrub restoration promotes the accumulation of SOC.

[Evolution Characteristics of Atmospheric Formaldehyde Emissions in Guangdong Province from 2006 to 2020].

Atmospheric formaldehyde, a key precursor for ozone (O3) and secondary PM2.5, is carcinogenic and plays an important role in atmospheric photochemistry and the formation of secondary pollution. However, the lack of understanding of the emission sources of atmospheric formaldehyde limits the study on the formation mechanism of secondary pollution and the formulation of pollution control strategies. This study used the emission factor and source profile methods to establish the emission inventories of formaldehyde in Guangdong Province from 2006 to 2020 and identified the main emission sources of formaldehyde and spatial and temporal evolution characteristics. The results showed that the formaldehyde emissions in Guangdong Province fluctuated in the range of 39000-56000 tons during 2006 to 2020, exhibiting a very weak downward trend. Biomass combustion is an important source of formaldehyde emission in Guangdong Province, of which the contribution decreased from 58% in 2006 to 27% in 2020 owing to effective control measures implemented in Guangdong Province. The solvent use source became the predominant emission source of formaldehyde in 2020 by contributing up to 28%, primarily through plastic products and asphalt paving sources. The construction machinery and trucks fueled by diesel were important contributors of formaldehyde emissions from mobile sources. Although the formaldehyde emissions in the Pearl River Delta and the non-Pearl River Delta were equivalent, the spatial distributions showed that formaldehyde emission hotspots were concentrated in the center of the Pearl River Delta and the eastern and western areas of the non-Pearl River Delta. This was primarily because the solvent use and mobile sources were the main sources of formaldehyde emissions in the Pearl River Delta, whereas the biomass combustion source was the dominant source in the non-Pearl River Delta. Therefore, the formaldehyde emission mitigations of the industrial and mobile sources in the central region of the Pearl River Delta and the biomass combustion source in the western area of Guangdong should be further strengthened in the future.

Experimental research on the evolution characteristics of a bending hybrid ultrasonic motor during long-time operation.

The characteristics evolution rules of an ultrasonic motor (USM) based on the hybrid of bending modes during long-time operation are tested and analyzed in this work. The alumina and nitride silicon ceramics are used as the driving feet and rotor respectively. The variations of mechanical performances including the speed, torque, and efficiency with time are tested and evaluated in the whole life period of the USM. Meanwhile, the vibration characteristics of the stator such as the resonance frequencies, amplitudes, and quality factors are also tested and analyzed every-four hours. Moreover, the real-time test for performances is conducted to assess the effect of temperature on mechanical performances. Furthermore, the effect of wear and friction behavior of the friction pair on the mechanical performances is analyzed. The torque and efficiency have apparent decreasing trends and fluctuated widely before about 40 h, and then gradually stabilize for 32 h, and finally fall rapidly. By contrast, the resonance frequencies and amplitudes of the stator only decrease by less than 90 Hz and 2.29 µm at first, and then keep fluctuant. During the continuous operation of the USM, the amplitudes will decrease as the increase of surface temperature, and followed by long-time wear and friction of the contact surface, the decrease of contact force is incapable to support the operation of the USM at last. This work is helpful to understand the evolution characteristics of the USM and provides the guidelines for the design, optimization, and practical application of the USM.

Research on the Evolution of Shield Segment Cracks Based on Acoustic Emission and CMOD.

In order to explore the cracking law and failure characteristics of segments, a model test of shield segment cracking was conducted. The microscopic and macroscopic crack evolution process of the segment is studied by using acoustic emission detection technology and crack opening displacement (CMOD). According to the acoustic emission signal and CMOD, characteristics generated in the process of segment cracking, in the form of numerical value, the evolution characteristics of each stage of segment cracking are directly reflected. Based on acoustic emission energy and CMOD, the segment cracking damage model was established to determine the segment fracture damage degree. The result shows that segment cracking can be divided into three stages, and the acoustic emission detection results and CMOD have different degrees of change in each cracking stage. This proves that both the acoustic emission acquisition results and CMOD can be used as evaluation indicators of damage degree. Acoustic emission can accurately identify the crack evolution process, and the yield strengthening is an important stage of crack damage evolution. The damage data points in this stage account for 76.83% of all the damage data points, the occurrence rate of damage data points is 0.225 s, and the density of data points in the damaged area is 3.219 × 10-4 mm3, which is larger than the other two stages. The segment cracking damage model can effectively reflect the segment cracking degree and provide a reference for the actual segment cracking assessment.

Spatial Evolutionary Characteristics and Influencing Factors of Urban Industrial Carbon Emission in China.

Climate warming caused by carbon emissions is a hot topic in the international community. Research on urban industrial carbon emissions in China is of great significance for promoting the low-carbon transformation and spatial layout optimization of Chinese industry. Based on ArcGIS spatial analysis, Markov matrix and other methods, this paper calculates and analyzes the temporal and spatial evolution characteristics of industrial carbon emissions in 282 cities in China from 2003 to 2016. Based on the spatial Dubin model, the influencing factors of urban industrial carbon emissions in China and different regions are systematically analyzed. The study shows that (1) China's urban industrial carbon emissions generally show a trend of first growth and then slow decline. The trend of urban industrial carbon emissions in the western, central, northeastern and eastern regions of China is basically consistent with the overall national trend; (2) In 2003, China's urban industrial carbon emissions were dominated by low carbon emissions. In 2016, China's urban industrial carbon emissions were dominated by high carbon emissions, and the spatial trend is gradually decreasing from the eastern region to the central region to the northeast region to the western region; (3) In 2003, the evolution pattern of China's urban industrial carbon emissions was "low carbon-horizontal expansion" dominated by positive growth, and in 2016, it was "low carbon-vertical expansion" dominated by scale growth; (4) China's urban industrial carbon emissions have spatial viscosity, and the spatial viscosity decreases with the increase of industrial carbon emissions. (5) In 2004, the relationship between urban industrial carbon emissions and gross industrial output value in China is mainly weak decoupling. In 2016, various types of decoupling regions are more diversified and dispersed, and strong decoupling cities are mainly formed from weak decoupling cities in southwest China and eastern coastal areas; (6) From a national perspective, indicators that are significantly positively correlated with industrial carbon emissions are urban industrial structure, industrial agglomeration level, industrial enterprise scale and urban economic development level, in descending order. Indicators that are significantly negatively correlated with urban industrial carbon emissions are industrial structure and industrial ownership structure, in descending order. Due to the different stages of industrial development and industrial structure in different regions, the influencing factors are also different.

New Insights Into the Social Rumor Characteristics During the COVID-19 Pandemic in China.

Background: In the early stage of the COVID-19 outbreak in China, several social rumors in the form of false news, conspiracy theories, and magical cures had ever been shared and spread among the general public at an alarming rate, causing public panic and increasing the complexity and difficulty of social management. Therefore, this study aims to reveal the characteristics and the driving factors of the social rumors during the COVID-19 pandemic. Methods: Based on a sample of 1,537 rumors collected from Sina Weibo's debunking account, this paper first divided the sample into four categories and calculated the risk level of all kinds of rumors. Then, time evolution analysis and correlation analysis were adopted to study the time evolution characteristics and the spatial and temporal correlation characteristics of the rumors, and the four stages of development were also divided according to the number of rumors. Besides, to extract the key driving factors from 15 rumor-driving factors, the social network analysis method was used to investigate the driver-driver 1-mode network characteristics, the generation driver-rumor 2-mode network characteristics, and the spreading driver-rumor 2-mode characteristics. Results: Research findings showed that the number of rumors related to COVID-19 were gradually decreased as the outbreak was brought under control, which proved the importance of epidemic prevention and control to maintain social stability. Combining the number and risk perception levels of the four types of rumors, it could be concluded that the Creating Panic-type rumors were the most harmful to society. The results of rumor drivers indicated that panic psychology and the lag in releasing government information played an essential role in driving the generation and spread of rumors. The public's low scientific literacy and difficulty in discerning highly confusing rumors encouraged them to participate in spreading rumors. Conclusion: The study revealed the mechanism of rumors. In addition, studies involving rumors on different emergencies and social platforms are warranted to enrich the findings.

[Evolution Characteristics and Clinical Significance of Blood Separation in Patients with Multiple Myeloma].

OBJECTIVE: To investigate the evolution of blood separation results by gel extraction of multiple myeloma (MM) patients, and to evaluate the clinical value of abnormal blood separation results for the evaluation of disease and prognosis. METHODS: The clinical data of 5 patients diagnosed newly MM patients with abnormal blood separation of gel collection vessels in our hospital were retrospectively analyzed, and the changes of blood separation results and blood index levels were followed up with the improvement of treatment effect, and the correlation of different blood index levels was analyzed. RESULTS: In 5 patients with newly diagnosed MM, the blood separation result showed floating phenomenon after centrifugation, which divided into three layers and the order from top to bottom is separator gel, serum, and red blood cells(RBC). With partial remission of clinical symptoms, the blood separation results were still abnormal, which were divided into three layers from top to bottom: serum, RBC and separator gel. Finally, with complete remission of the disease, blood separation results returned to normal, from top to bottom: serum, separator gel, RBC. With the blood separation results from abnormal to normal, the blood routine indicators: Hb, Hct levels gradually increased, neutrophil/lymphocyte ratio (NLR), monocyte/lymphocyte ratio (MLR) gradually decreased; biochemical indexes: TP, GLB, Ig and ß2-MG levels gradually decreased. Tumor load related indicators: serum IL-6, TNF-α, IL-17 levels gradually decreased, and IL-35 levels gradually increased; and the differences were statistically significant (P<0.05). Pearson correlation analysis showed that serum ß2-MG was positively correlated with IL-6, TNF-α and IL-17 levels (r=0.710, 0.756, 0.581, P<0.05), and negatively correlated with IL-35 level (r=-0565, P<0.05). CONCLUSION: Abnormal blood separation exists in MM patients, and there are significant differences in blood, tumor load and immune balance related indexes in patients with different blood separation results, which provides partial experimental basis for evaluation of disease, efficacy and prognosis with different blood separation results.

Spatiotemporal evolution characteristics of the late frost damage risk to shrubby tea trees in tea region, southwest China from 1971 to 2020.

Understanding the spatiotemporal evolution characteristics of the risk of late frost damage has scientific guiding significance for optimizing the regional agricultural production layout and varie-ty tuning. Based on the daily meteorological data of 65 weather stations in the southwest China tea region from 1971 to 2020, we analyzed variation characteristics of the last frost date (LFD), tea bud open date (BOD), and their relationships, constructed frost damage probability index and frost damage severity index of spring shoots of shrubby tea trees, and analyzed the spatiotemporal evolution chara-cteristics of the late frost damage risk of shrub tea trees in the southwest tea region. The results showed that both the BOD and LFD had a significant ahead of trend from 1971 to 2020 and the early rate of the LFD was relatively faster than that of the BOD in the southwest tea region. The number of days that the tea buds were exposed to late frost damage after germination showed an non-significant declining trend. The risk of late frost damage of shrubby tea trees in most parts of the southwest tea region showed a declining trend, but Guizhou tea planting region showed an insignificant increasing trend. The risk of late frost damage to shrubby tea trees was high in the western marginal mountai-nous areas of Sichuan tea region, and the junction of Guizhou and Yunnan tea region. The risk of late frost damage was at low level in Sichuan Basin, southern Yunnan tea region, and southern Guizhou tea region. The risk of late frost damage to shrubby tea trees in the northern and central-eastern parts of Yunnan tea region showed an obvious decreasing trend, but increased significantly in the central and eastern parts of Guizhou tea region.

The evolution characteristics and influence factors of carbon productivity in China's industrial sector: from the perspective of embodied carbon emissions.

In the context of low-carbon economic development, carbon productivity has effectively integrated the two major objectives of carbon reduction and economic growth, and increasing carbon productivity has become the main approach to address global climate change. Using data from China's input-output table for 2002-2017, this study measures the evolutionary characteristics and influencing factors of carbon productivity from the perspective of embodied carbon emission in China's industrial sector. The results indicate that, first, China's industrial sectors' carbon productivity shows an increasing trend from 25.22 to 65.3 million yuan/10,000 tons of CO2 in 2002-2017, but the overall level is low. The energy efficiency factor is a major element affecting improvement in carbon productivity. Second, the carbon productivity of the 28 industrial sectors shows an increasing trend. There is a significant gap in the carbon productivity between different industrial sectors. The energy efficiency factor in all industrial sectors is positive, indicating that energy efficiency is a positive factor in increasing carbon productivity. Third, from largest to smallest in the carbon productivity are the primary, tertiary, and secondary industries. Finally, this paper recommends several approaches to improve carbon productivity from the perspectives of technology, differentiated policies of carbon emission reduction, and industrial structure adjustment.

Experimental investigation on the characteristics of temporary cavity in BABT with 9 mm projectiles.

Temporary cavity, one physical phenomenon in BABT reflects the dynamic response of biological tissues and is used to evaluate the trauma. To clarify the characteristics of cavity evolution during 9 mm Luger penetration, we obtain the deformation profiles by using an experimental method with a high-speed camera and thereby visualize the cavity formation and development. According to the dynamic impact experiments at the velocity from 220 to 420 m/s, the temporary cavity profile can be approximately regarded as a semi-ellipsoid. The maximum depth increases as a quadratic function of velocity. Additionally, the maximum volume of the temporary cavity is attained significantly after the maximum depth. The change rate of cavity volume in the expansion stage is larger than that in the contraction stage.

Analysis of hydrochemical evolution in main discharge aquifers under mining disturbance and water source identification.

To discuss the hydrochemical evolution characteristics of the mining process of Peigou Coal Mine, based on the test results of 43 water samples collected at different times from three main discharge aquifers, namely, Carboniferous Taiyuan Formation limestone water (L7-8 + L5-6 water), Ordovician limestone water (including Taiyuan Formation L1-4), and Permian main mining coal seam roof and floor sandstone water (roof and floor water), a hydrochemical evolution model of the mining disturbances since 2003 has been established. The carbonate and sulphate dissolution and pyrite oxidation in Ordovician limestone water significantly decreased and then increased in 2006, and silicate weathering was weak. The carbonate and sulphate dissolution, silicate weathering and pyrite oxidation of roof and floor sandstone water increased. At the same time, a water source identification model suitable for the Peigou Coal Mine was developed by comparing the Fisher discriminant and the BP (back propagation) neural network discriminant. The accuracy rates of Fisher discriminant and BP neural network discriminant are 81.40% and 83.72% respectively, which indicates that BP neural network is more accurate. Finally, the evolution of hydraulic connection between aquifers is analysed. We speculate that there is a fracture development channel between Ordovician limestone water and roof and floor water aquifers that is affected in 2005 by the mining disturbance. This study has significance for examining the hydrochemical evolution of groundwater in mines and acting as a guideline to prevent and control water inrushes.

[Characteristics of Water-soluble Inorganic Ions in PM2.5 in Beijing During 2017-2018].

To explore the characteristics of water-soluble inorganic ions (WSIIs) in PM2.5 during the process of continuous improvement of air quality in Beijing in recent years, a continuous collection of PM2.5 sample campaign was conducted in Beijing from 2017 to 2018. The PM2.5 mass concentration and WSIIs were then determined. The results showed that the average concentration of PM2.5 in Beijing was (77.1±52.1) µg ·m-3, with the highest and lowest values during spring [(102.9±69.1) µg ·m-3]and summer [(54.7±19.9) µg ·m-3], respectively. The average concentration of WSIIs was (31.7±30.1) µg ·m-3, accounting for 41.1% of the PM2.5 mass, and the seasonal contributions were: autumn (45.9%) > summer (41.9%) > spring (39.9%) ≥ winter (39.2%). SNA was an important component of the WSIIs that accounted for 86.0%, 89.5%, 74.6%, and 73.0% of the total WSIIs during spring, summer, autumn, and winter, respectively. With an increase in temperature, the concentration of NO3- increased initially and then decreased, while the concentration of SO42- increased. When the relative humidity was less than 90%, the concentrations of both NO3- and SO42- increased with an increase in relative humidity. With the aggravation of pollution, the overall contribution of WSIIs in PM2.5 increased significantly, and the evolution characteristics of different ions were different. Among them, the concentration and contribution of NO3- continued to increase, while the contributions of SO42- and the ions from dust (Mg2+, Ca2+, and Na+) decreased. During the observation period, the primary sources of WSIIs were secondary conversion, combustion source, and dust. The control of coal combustion and motor vehicles is critical to reduce the emission of WSIIs. The backward trajectory analysis showed that the air masses from the south and west of Beijing corresponded to the high PM2.5 concentration and proportion of WSIIs, and the contribution of secondary ions was significant. However, the concentrations and proportions of the air masses from the northwest and north were relatively low, but the contribution of Ca2+ was high.

[Characteristics of Carbonaceous Species in PM2.5 in Southern Beijing].

To investigate the characteristics of carbonaceous species in PM2.5 in Beijing after the implementation of the Action Plan for the Prevention and Control of Air Pollution, PM2.5 was continuously sampled in the heavily polluted southern urban area of Beijing from December 2017 to December 2018. The characteristics of organic carbon (OC) and element carbon (EC) were then determined. The results showed that the annual concentrations of PM2.5, OC, and EC in Beijing varied in wide ranges of 4.2-366.3, 0.9-74.5, and 0.0-5.5 µg ·m-3, respectively, and the average mass concentration were (77.1±52.1), (11.2±7.8), and (1.2±0.8) µg ·m-3. Overall, the carbonaceous species (OC and EC) accounted for 16.1% of the PM2.5 mass. The seasonal characteristics of the OC mass concentrations were: winter [(13.8±8.7) µg ·m-3] > spring [(12.7±9.6) µg ·m-3] > autumn [(11.8±6.2) µg ·m-3] > summer [(6.5±2.1) µg ·m-3]. The concentration of the EC during the four seasons was low, ranging from 0.8 to 1.5 µg ·m-3. The annual average mass concentration and contribution of secondary organic carbon (SOC) were (5.4±5.8) µg ·m-3 and 48.2%, respectively, highlighting the significant contribution of the secondary process. With the aggravation of pollution, although the contribution proportion of OC and EC decreased, their mass concentrations during "heavily polluted" days were 6.3 and 3.2 times that of "excellent" days, respectively. Compare to non-heating period, the mass concentrations of PM2.5, OC, and SOC increased by 14.4%, 47.9%, and 72.1% in heating period, respectively, which emphasized the importance of carbonaceous species during heating periods. Potential source contribution function (PSCF) analysis showed that the southwest areas of Beijing (such as Shanxi and Henan province) were the main potential source areas of PM2.5 and OC. The high value area of the PSCF of EC was less and the main potential source area was in the south of Beijing (such as Shandong and Henan province).

[Spatiotemporal variability characteristics and driving forces of land use in the Pan-Pearl River Basin, China]. / æ³›ç æ±ŸæµåŸŸåœŸåœ°åˆ©ç”¨æ—¶ç©ºå˜åŒ–ç‰¹å¾åŠé©±åŠ¨å› å­.

The Pan-Pearl River Basin is a bridgehead for China's reform and opening-up and the construction of the Belt and Road at Sea, with vital strategic significance in Chinese overall development. Land use data and climate and socio-economic indicators were integrated to probe the spatiotemporal change and its driving forces of land use in the Pan-Pearl River basin with ArcGIS spatial analysis tool and SPSS factor analysis tool. Results showed that land use in the Pan-Pearl River Basin significantly changed between 1990 and 2015, with decreases of the area of paddy field and woodland and rapid increases of urban land and other construction land. Outflow of grassland occurred in the northwestern part of the basin. Reduction of cultivated field was mainly concentrated in the central part of the basin and coastal areas. Increases in urban and rural land, industrial and mining land, and residential land were centrally distributed in the Guangdong-Hong Kong-Marco Greater Bay Area. The prominent change areas were Guangdong-Hong Kong-Marco Greater Bay Area : central and southeast of Guangxi Province : northern Hainan Province. Land use changes during 1990-2000 were most obvious in the basin. The main driving factor of spatiotemporal variation of land use was the rapid development of social economy and industry and the improvement of residents' consumption level.

[Evolutionary characteristics of soil organic carbon storage in soil plough layer under a cropland reclamation process in desert oasis]. / è’æ¼ ç»¿æ´²å†œç”°åž¦æ®–è¿‡ç¨‹ä¸­è€•å±‚åœŸå£¤ç¢³å‚¨é‡æ¼”å˜ç‰¹å¾.

The reclamation time was examined by combining field investigation and remote sensing image analysis in the Linze desert oasis area in the middle of the Hexi Corridor. Characteristics of soil organic carbon storage (SOCD) in cropland (0-20 cm) with different reclamation backgrounds were compared to understand the evolution trend of SOCD during reclamation. The SOCD of cropland (0-20 cm) varied from 2.41 to 32.97 t·hm-2, with an average of 17.22 t·hm-2. The ave-rage SOCD of cropland in saline-alkali land, Gobi and sandy land background was 19.36, 16.10, and 15.93 t·hm-2, respectively. The SOCD under three different reclamation conditions showed an increasing trend after cultivation. The cropland in sandy land and the Gobi background slowly increased after 20 years reclamation. The cropland in saline-alkali background showed a slowdown after 25 years reclamation. The SOC sequestration rates of the cropland under sandy land, Gobi and saline-alkali land background were 0.424, 0.485 and 0.811 t·hm-2·a-1, respectively. The SOCD were positively correlated with total nitrogen, total phosphorus, available nitrogen, and available phosphorus content, but had no significant correlation with available potassium and soil pH. In conclusion, the SOC sequestration rate in the saline-alkali land background was significantly higher than that in Gobi and sandy land background. However, SOCD were at a relatively low level after 30 years reclamation. Therefore, cropland management needs to be carried out for different reclamation backgrounds to improve land use efficiency and productivity in desert oasis.

Changes of soil physical and chemical properties of albic soil in the meadow of Sanjiang Plain after rice planting.

The changes and renewal of soil quality are the criteria for judging agricultural development and soil management. The albic soil is the main paddy field soil in Sanjiang Plain. There is limited knowledge about the changes of soil quality after the dry field was changed into the paddy field. Taking albic soils from different years of rice planting as study objects, the changes of soil physical and chemical properties were investigated. The results showed that the total amount of soil organic carbon and reducing substances increased in the ploughing layer (16-23 cm thick) and the bottom ploughing layer (6-8 cm thick). The depth of ploughing layer gradually increased with the increases of rice planting years. There was no significant change after the bottom layer was changed into the paddy field. There was no significant difference in the subsoil layer (20 cm thick) compared with dryland. The Fe2+ and Mn2+ in the soil tended to migrate downward, but only to the plough bottom layer. The ratio of soil solid phase of the ploughing layer and the ploughing bottom layer increased after rice planting, with the ratio of soil solid phase of the ploughing bottom layer increased from 47.8% to 70.0% and the bulk density increased from 1.22 g·cm-3 to 1.77 g·cm-3. Decreases of the total amount of soil porosity, increases of the proportion of micropores, and cohesive leaching deposition in the albic soil were observed after rice planting. The changes of soil physical and chemical properties of albic soil after rice planting were generally consistent with the evolution of paddy soil except for several particularities.