Mutual feedback between algal blooming and global warming

Global warming and algal blooms have been two of the most pressing problems faced by the world today.In recent decades,numerous studies indicated that global warming promoted the expansion of algal blooms.However,research on how algal blooms respond to global warming is scant.Global warming coupled with eutrophication promoted the rapid growth of phytoplankton,which resulted in an expansion of algal blooms.Algal blooms are affected by the combined effects of global warming,including increases in temperatures,CO_(2)concentration,and nutrient input to aquatic systems by extreme weather events.Since the growth of phytoplankton requires CO_(2),they appear to act as a carbon sink.Unfortunately,algal blooms will release CH4,CO_(2),and inorganic nitrogen when they die and decompose.As substrate nitrogen increases from decompose algal biomass,more N2O will be released by nitrification and denitrification.In comparison to CO_(2),CH4has 28-fold and N2O has 265-fold greenhouse effect.Moreover,algal blooms in the polar regions may contribute to melting glaciers and sea ice(will release greenhouse gas,which contribute to global warming)by reducing surface albedo,which consequently would accelerate global warming.Thus,algal blooms and global warming could form feedback loops which prevent human survival and development.Future researches shall examine the mechanism,trend,strength,and control strategies involved in this mutual feedback.Additionally,it will promote global projects of environmental protection combining governance greenhouse gas emissions and algal blooms,to form a geoengineering for regulating the cycles of carbon,nitrogen,and phosphorus.

The oxygen isotopic composition of phosphate as an effective tracer for phosphate sources in Hongfeng Lake

In order to characterize the oxygen isotopic composition of internal phosphate and explore the possibility of using these data to identify phosphate sources, we measured oxygen isotopic compositions of phosphate(δ^(18)O_p) in sediment pore water in Hongfeng Lake, a typical deep-water lake in a mountainous area. These data, in combination with δ^(18)O_p in surface water samples and water column samples, were successfully used to identify phosphate sources. The δ^(18)O_p value of sediment pore water ranged from 15.2% to 15.8%, with an average value of 15.5%—the δ^(18)O_p value of internal phosphate. The δ^(18)O_p values decreased gradually through the water column from 19.4% in surface water to 16.4% in deeper water, implying that internal phosphate had more negative δ^(18)O_p values than external phosphate. This finding was substantiated by horizontal variations in δ^(18)O_p values, which decreased with increasing distance from inflowing rivers. All collected evidence suggests that external and internal phosphate have distinctly different isotopic signatures and that these signatures have not been considerably altered by biological mediation in Hongfeng Lake. Therefore, δ^(18)O_p can be used to distinguish phosphate sources. A two-endmember mixing model showed that internal phosphate had an average contribution of 40%, highlighting the influence of internal phosphorus loading on aqueous phosphate and eutrophication. This study illustrates the need to reduce the internal phosphorus load from sediment and provides guidance for nutrient management and in-lake restoration treatment in Hongfeng Lake. The data presented here are limited, but serve to highlight the great potential of δ^(18)O_p as an effective tracer for identifying phosphate sources. Systematic investigations of the oxygen isotopic compositions of external phosphate, internal phosphate, and phosphate through the water column, in combination with in-lake P biogeochemical cycle study, would be desirable in further research.

R123在套管式蒸发器中的换热特性

该文对饱和压力分别为0.152MPa和0.2MPa的R123在水平套管蒸发器中的换热特性进行了实验研究。探讨了工质质量流速、热流密度、蒸发压力以及工质干度对管内流动沸腾换热系数的影响规律。同时,分别采用Shah关联式、Gungor-Winterton关联式以及Kandlikar关联式对相同实验工况下R123的管内流动沸腾换热系数进行了计算,并与实验结果进行了对比。结果表明:当蒸发压力和热流密度一定时,管内流动沸腾换热系数随工质质量流速的增大而增大;当蒸发压力和质量流速一定时,随热流密度的增大而增大;当热流密度和质量流速一定时,随蒸发压力的升高而增大,而随工质干度的增大先增大后减小。相较于Shah关联式和Gungor-Winterton关联式,采用Kandlikar关联式计算精度更高。

烟煤和无烟煤混煤燃烧特性和动力学分析

实验在高温热重差热综合分析仪上对烟煤和无烟煤混煤在不同配比下的燃烧特性和动力学参数进行了分析研究。分析了不同掺混比例下混煤的着火温度、燃烬温度、综合燃烧特性指数等燃烧特性参数,进行了反应动力学计算和分析。实验结果表明,随着烟煤中无烟煤掺入比例的不断增加,TG和DTG曲线逐渐向高温区移动,不同掺混比例下的混煤DTG曲线出现双峰,混煤的着火温度和燃烬温度逐渐升高,混煤高温段的活化能始终高于低温段的活化能,说明挥发分会在低温段挥发释放出来,放出大量的热量,从而改善了固定碳的燃烧环境,有利于固定碳的燃烧,烟煤和无烟煤混煤在低温段有更好的燃烧性能和表现。

Passive Cooldown Performance of Integral Pressurized Water Reactor

The design of an integral pressurized water reactor (IPWR) focuses on enhancing the safety and reliability of the reactor by incorporating a number of inherent safety features and engineered safety features. However, the characteristics of passive safety systems for the marine reactors are quiet different from those for the land nuclear power plant because of the more formidable and dangerous operation environments of them. This paper presents results of marine black out accident analyses. In the case of a transient, the passive residual heat removal system (PRHRS) is designed to cool the reactor coolant system (RCS) from a normal operation condition to a hot shutdown condition by a natural circulation, and the shutdown cooling system (SCS) is designed to cool the primary system from a hot shutdown condition to a refueling condition by a forced circulation. A realistic calculation has been carried out by using the RELAP5/MOD3.4 code and a sensitivity analysis has been performed to evaluate a passive cooldown capability. The results of the accident analyses show that the reactor coolant system and the passive residual heat removal system adequately remove the core decay heat by a natural circulation.

金属基有机硅树脂涂层复合材料的导热性能

以锌粉为导热填充剂对环氧有机硅树脂进行改性,考察了改性环氧有机硅树脂涂层干膜中锌粉含量对涂层导热系数的影响,分析了涂层厚度对碳钢基材导热性能的影响.结果表明,环氧有机硅树脂涂层的导热系数约为0.19 W/（m·K）,其耐温能力在200℃以上,可保证涂层在中低温烟气余热回收换热器表层长期工作而不发生任何热反应;添加锌粉可改善环氧改性有机硅涂层的导热性能,涂层干膜锌粉25wt%时,涂层材料导热系数达0.35 W/（m·K）,较未添加锌粉时增大了84%.复合材料的导热系数随涂层厚度增加而下降,无涂层的碳钢导热系数为47.59 W/（m·K）,涂层厚度为200？m时,导热系数降至34.33 W/（m·K）.

Microscale Chemical Features of Sediment-Water Interface in Hongfeng Lake

In situ microscale distributions of 02, H2S, pH and redox potential in sediments of Hongfeng Lake, SW China, were investigated using the powerful microsensor technique. Our results show that O2 was depleted within the top 3.9 mm in surface sediments, and H2S was subsequently detected at -6.0 mm depth, and reached its maximum concentrations at -25 mm. The degradation of organic matter and reduction of sulfate might be the major pathways of producing H2S in sediments, pH rapidly reduced in surface layers mainly due to H＋ release in the oxidation of organic matter. Eh also decreased sharply in surface sediments, probabl indicating the coexistence of Fe and Mn oxides with O2 in aerobic region. Furthermore, the programme of PROFILE was applied to model the 02 gradient, and good fit was obtained between the simulative values and the factual values both in sediments and in the diffusive boundary layer （DBL）. The results indicate that the depth-integrated O2 consumption rates within sediments were 0.083 and 0.134 nmol·m-3·s-1 in site S1 and site S2, respectively. In addition, there were distinct DBL in two sediment profiles, with 1.2 mm thickness in S1 and 0.9 mm thickness in S2. The diffusive fluxes of O2 within the DBL were 67.13 nmol·m-2·s-1 in S1 and 88.54 nmol·m-2·s-1 in S2.