The contribution of black carbon to global ice nucleating particle concentrations relevant to mixed-phase clouds

Black carbon (BC) aerosol plays an important role in the Earth’s climate system because it absorbs solar radiation and therefore potentially warms the climate; however, BC can also act as a seed for cloud particles, which may offset much of its warming potential. If BC acts as an ice nucleating particle (INP), BC could affect the lifetime, albedo, and radiative properties of clouds containing both supercooled liquid water droplets and ice particles (mixed-phase clouds). Over 40% of global BC emissions are from biomass burning; however, the ability of biomass burning BC to act as an INP in mixed-phase cloud conditions is almost entirely unconstrained. To provide these observational constraints, we measured the contribution of BC to INP concentrations ([INP]) in real-world prescribed burns and wildfires. We found that BC contributes, at most, 10% to [INP] during these burns. From this, we developed a parameterization for biomass burning BC and combined it with a BC parameterization previously used for fossil fuel emissions. Applying these parameterizations to global model output, we find that the contribution of BC to potential [INP] relevant to mixed-phase clouds is ∼5% on a global average.

Black carbon (BC) is the primary light-absorbing aerosol in the atmosphere. Its short lifetime (days to weeks) relative to CO2 and methane makes it an intriguing target for near-term climate mitigation (1). Errors associated with BC climate forcing, however, obfuscate its efficacy as a climate mitigator. The largest contributions to BC’s forcing uncertainties are often attributed to its effects on clouds, in particular mixed-phase clouds [i.e., clouds containing supercooled cloud droplets and ice particles, (2)]. Efforts to reduce these uncertainties are hindered by the complexity of aerosol–cloud interactions (3). Particularly vexing is quantifying the abundance and identity of ice nucleating particles (INPs). INPs provide the only pathway for primary ice formation in mixed-phase clouds; however, they are rare [e.g., ∼1 in 106 particles are INPs at −20 °C (4)]. Despite their rarity, INPs influence mixed-phase cloud ice concentrations and precipitation and therefore alter cloud albedo and lifetime (5). Furthermore, the INP properties of aerosols, such as BC, will affect their own lifetime, vertical structure, and transport to climate-sensitive regions such as the Arctic (6). Despite its importance to the Earth’s climate and near-term climate mitigation strategies, the INP efficiency of BC relevant to mixed-phase clouds remains almost entirely unconstrained from direct observations, encumbering attempts to estimate BC’s impact on mixed-phase clouds in modeling studies (7).BC’s efficacy as an immersion-freezing INP (henceforth, INP will refer only to freezing by particles encapsulated within supercooled cloud droplets, termed immersion freezing and pertinent to mixed-phase cloud conditions) has been studied in the laboratory for decades, with starkly conflicting results. Early laboratory studies showed that acetylene and kerosene flame-generated soot can nucleate ice below −20 °C. (8, 9); after normalizing for surface area, these studies indicated that BC may be more ice active than the well-known INP mineral dust (10). Results from later laboratory studies were contradictory, suggesting that BC was not active as an INP above instrument limits of detection. These included soot aerosols from miniCAST soot generators, graphite spark generator soot, hydrocarbon flame-generated soot, and fullerene soot, as well as various lamp blacks and carbon blacks (11–15).Unfortunately, field study measurements of the contribution of BC to INP concentrations ([INP]) have also been inconclusive. For example, in-cloud measurements from the high-altitude observatory at Jungfraujoch, Switzerland saw that BC is enriched in ice-particle residuals and therefore may efficiently nucleate ice (16); later measurements at the same site, however, saw that BC is depleted in the ice phase, which suggests that BC does not play a significant role in mixed-phase cloud ice nucleation (17, 18).These contradictions in laboratory and field studies suggest that fuel type and combustion conditions determine the ice nucleation properties of BC. Such conditions prescribe BC’s physical and morphological properties as well as its coemitted and coagulated species. Major BC fuel types include fossil fuels and flammable biomass, and major combustion sources include diesel exhaust, residential fuel burning, prescribed burns, and wildfires (2). BC particles from fossil fuel combustion and anthropogenic pollution are not significant sources of INPs. For example, studies on diesel exhaust have shown that less than 1 in 109 BC particles are ice nucleation active at −30 °C (19). Furthermore, ambient [INP] in Beijing, China were relatively constant over several weeks despite BC concentrations varying by a factor of 30 and reaching values as high as 17.26 μg⋅m−3 (20).Elevated [INP] have been observed in biomass-burning smoke during laboratory and field studies (21–23); however, it is unclear from these studies if the INPs are actually BC. Some studies have shown that BC may be the dominant INP type in select biomass burning conditions. For example, soot particles were found to contribute up to 64% of the INPs in prescribed burns within a predominantly wiregrass understory (24). Furthermore, BC contributed up to 70% to [INP] in controlled laboratory burns of grasses (25). As biomass burning represents ∼40% of global BC emissions (2), BC from biomass burning could be a significant source of INP globally. In both of these studies, however, the overall ice-active fractions may be too low to influence [INP], even on the regional level (21). Thus, it remains unclear whether BC contributes to [INP] outside of thick plumes and on a global scale (26).Regional- and global-scale estimates of BC [INP] rely on models that can implement theory-based or empirical ice nucleation parameterizations. Using parameterizations based on BC INP activity from the acetylene and kerosene-burner soot studies, models have found that BC contributes ∼50% to [INP] in springtime low-level Arctic mixed-phase clouds (27), and 23 to 61% to global [INP] depending on dust loadings (28). Taking into account the aforementioned negative results, these modeling studies highlight that BC’s contribution to [INP] is poorly constrained and is estimated to vary from no contribution to being the most abundant INP globally.To assess the role of BC from biomass burning as an INP, we determined the contribution of refractory BC (rBC)-containing particles to [INP] from field measurements of both prescribed burns and wildfires using the single-particle soot photometer coupled to a continuous-flow diffusion chamber (SP2-CFDC) (29, 30). The SP2-CFDC selectively removes rBC from an aerosol stream and quantifies that effect on [INP]. From these burns, we found that rBC-containing particles contributed ≤10% to [INP]. From these results, we developed a surface-area normalized parameterization for BC INPs from biomass burning. The parameterization aligns well with other surface-area normalized parameterizations derived from laboratory proxies of BC and diesel exhaust BC (15, 19, 31). These parameterizations are over four orders of magnitude lower than the parameterization derived from acetylene and kerosene-burner soot studies and used in the aforementioned modeling studies. Assuming the INP characteristics of BC from the burns in this study can be extended to different biomass-burning fuel types and combustion conditions, this study strongly suggests that BC is not an efficient INP. Under this assumption, we assessed the global importance of BC as an INP by applying our parameterization to simulated biomass-burning aerosol from a global chemical transport model. A similar parameterization for diesel exhaust (19) was applied to simulated fossil fuel BC. From these treatments, we estimate that BC’s contribution to simulated, potential [INP] is only ∼5% on a global average.     

Geographic, seasonal, and precipitation chemistry influence on the abundance and activity of biological ice nucleators in rain and snow

Biological ice nucleators (IN) function as catalysts for freezing at relatively warm temperatures (warmer than −10 °C). We examined the concentration (per volume of liquid) and nature of IN in precipitation collected from Montana and Louisiana, the Alps and Pyrenees (France), Ross Island (Antarctica), and Yukon (Canada). The temperature of detectable ice-nucleating activity for more than half of the samples was ≥ −5 °C based on immersion freezing testing. Digestion of the samples with lysozyme (i.e., to hydrolyze bacterial cell walls) led to reductions in the frequency of freezing (0–100%); heat treatment greatly reduced (95% average) or completely eliminated ice nucleation at the measured conditions in every sample. These behaviors were consistent with the activity being bacterial and/or proteinaceous in origin. Statistical analysis revealed seasonal similarities between warm-temperature ice-nucleating activities in snow samples collected over 7 months in Montana. Multiple regression was used to construct models with biogeochemical data [major ions, total organic carbon (TOC), particle, and cell concentration] that were accurate in predicting the concentration of microbial cells and biological IN in precipitation based on the concentration of TOC, Ca²⁺, and NH₄⁺, or TOC, cells, Ca²⁺, NH₄⁺, K⁺, PO₄³⁻, SO₄²⁻, Cl⁻, and HCO₃⁻. Our results indicate that biological IN are ubiquitous in precipitation and that for some geographic locations the activity and concentration of these particles is related to the season and precipitation chemistry. Thus, our research suggests that biological IN are widespread in the atmosphere and may affect meteorological processes that lead to precipitation.     

南极冰藻 Berkeleya rutilans H-15中清除自由基活性物质的分离纯化及其结构分析

目的 研究和发现极端环境下南极冰藻中清除自由基活性物质.方法 以南极冰藻Berkeleya rutilans H-15为试验材料,在国内外首先建立起了从南极冰藻中获取清除白由基活性物质的一套完整的方法,包括用甲畔提取活性化合物,用DPPH法和Godin法来追踪和检测活性化舍物的分离效果及变化情况,用硅胶柱层析对活性化舍物进行初步的分离和纯化,用Sephadex LH柱层析来进一步纯化,通过高效液相来进行化舍物纯度检测,高纯度化舍物用红外光谱和液质联用方法来确定化合物的类型和有关的功能基团.结果 在Berkeleya rutilans H-15中获得了一个纯的活性化舍物,经红外光谱和液质联用图谱初步进行分子结构分析,推测此化合物属于酚类化舍物,并具有很强的清除自由基的活性.结论 在南极冰藻中寻找并获得高活性的抗氧化剂是完全可行的.     

冻干蜂王浆软胶囊的制备及稳定性影响因素研究

目的:制备冻干蜂王浆软胶囊并对其稳定性及影响因素进行实验研究。方法:以内容物沉降体积比为考察指标,筛选出适宜的助悬剂和工艺,轧制软胶囊,并考察其在冷藏、室温和高温高湿下的稳定性。HPLC法测定稳定性及不同影响因素下10-HAD含量的变化。结果:中试生产成品率90以上,软胶囊成品冷藏质量稳定,室温及高温高湿条件下产品质量明显下降,软胶囊壳中的水分对10-HAD的含量有明显影响。结论:冻干蜂王浆软胶囊的制剂成型工艺可行,产品贮存以冷藏为宜。     

Epimerization Kinetics of Moxalactam in Frozen Solution

The epimerization rate constants of R- and S-epimers of moxalactam (LMOX) in a frozen aqueous solution decreased as the temperature decreased. The reaction proceeded in the unfrozen region remaining in the frozen solution, without being affected by the ice. The reaction stopped completely below the collapse temperature of the LMOX aqueous solution. The ratio of R- and S-epimers at equilibrium, which was equal to the ratio of the epimerization rate constant, increased as the temperature decreased. This change in the ratio at equilibrium could be ascribed to the difference in the activation energy between the two epimers.     

The speed of ice growth as an important indicator in cryosurgery

PURPOSE: We consider the speed of ice growth as an indicator of the speed of cooling and investigated its impact on the factors at the cell death boundary in an in vitro simulated cryosurgical system. MATERIALS AND METHODS: PC-3 cells were cultured in culture plates and simulated cryosurgery was performed under different speeds of ice growth using an in vitro simulated cryosurgical system. The freezing front was closely monitored. Cells were fixed and stained 24 hours after cryosurgery. The distance from the cell death boundary to the ice front was measured and defined as the distance gap. It was correlated with the speed of ice growth. Temperature history at the cell death boundary was retrieved and also correlated with the speed of ice growth. RESULTS: A high correlation between the speed of ice growth and the temperature gradient plus an inverse correlation between the speed of ice growth and the distance gap were found. The distance gap narrowed when the speed of ice growth was around 3 mm per minute but widened when the speed of ice growth was slower than 1.5 mm per minute. CONCLUSIONS: Changes in ice growth speed indicate changes in the temperature gradient, and the distance between the ice front and the cell death boundary. Different treatment end points should be chosen according to the speed of ice growth to increase accurate cell killing.     

Environmental dew point and skin and lip weathering

Xerosis represents a physiological response of the stratum corneum (SC) to environmental threats. The influence of the environmental dew point (DP) is not fully understood. This parameter is the air temperature at which the relative humidity is maximum. This study aimed to assess the relationship between the environmental DP and the water‐holding capacity of the skin and lower lip vermilion. For comparison, SC property was evaluated after occlusive application of cooled and uncooled hydrogel pads. Electrometric measurements using a dermal phase meter (DPM) device were performed on the back of the hands, the cheeks and the lower lip of 40 healthy menopausal women. Assessments were performed in the outdoor conditions during winter and spring. The same measurements were recorded after hydrogel pads, at room temperature or cooled to 4 °C, were placed for 15 min on the test sites. The environmental DP was recorded at each evaluation time. The SC water‐holding capacity was discretely influenced by the DP. In the open‐air environmental conditions, a positive linear relationship was found on the cheeks between the DP and DPM values. The relationship was weaker on the lips. Conversely, a consistent increase in DPM values was recorded immediately after removal of the cooled and uncooled hydrogel pads. The observations made in the open‐air testing conditions are consistent with the predicted events following the Arrhenius law. By contrast, the combination of cooling and occlusion by the hydrogel pads is responsible for the reverse effect on the SC.     

冰敷对不同血脂水平高热大鼠降温效果的实验研究

目的探索冰敷对不同血脂水平高热大鼠降温效果的影响,为不同血脂水平的高热患者实施冷疗提供参考。方法将同一批大鼠随机分为高脂组和对照组,每组10只。高脂组采用高脂饲料饲养,对照组采用普通饲料饲养。饲养3周后采用20%干酵母混悬液将其致热,致热成功后将大鼠麻醉,再使用10mL清水冰袋对其颈部和腋下冰敷30min。冰敷结束0、15、30、45、60、75、90、120、180、240、300、360min监测两组大鼠体温。体温观察结束采集两组大鼠血液检测血脂水平。结果两组大鼠血清总胆固醇和低密度脂蛋白比较,差异有统计学意义(均P<0.01)。冰敷结束45min内高脂组体温显著高于对照组(P<0.05,P<0.01)。结论使用高脂饲料喂养大鼠可在短期内改变血脂状况。血脂水平对降温效果有一定影响,血脂水平高者降温效果差。冰敷过程中针对血脂水平高者应适当增加冰袋或延长冰敷时间,以达到更好的降温效果。     

廉泉穴不同针刺深度联合冰刺激治疗脑卒中后吞咽障碍患者临床疗效研究

目的：观察廉泉穴不同针刺深度联合冰刺激治疗中风后吞咽障碍患者临床疗效。方法：80例脑卒中后伴吞咽障碍患者随机分为浅刺组和深刺组各40例，2组患者给与常规药物治疗和冰刺激，浅刺组针刺廉泉穴30～40mm，深刺组针刺廉泉穴60～70 mm。治疗前后运用电视X线透视吞咽功能（VFSS）、标准吞咽功能评定量表（SSA）对2组患者进行评定，并统计临床疗效及不良反应情况。结果：治疗12周和治疗后第8周随访时，2组口腔期通过时间、咽期延迟时间、咽期通过时间与组内治疗前比较均明显减少(均P＜0.05)，SSA评分均明显降低(均P＜0.05)；治疗后第8周随访时与治疗12周比较，2组口腔期通过时间、咽期延迟时间、咽期通过时间均明显减少(均P＜0.05)，SSA评分均明显降低(均P＜0.05)；治疗12周和治疗后第8周随访时，深刺组口腔期通过时间、咽期延迟时间、咽期通过时间较浅刺组同时间点比较均明显减少(均P＜0.05)，SSA评分均明显降低(均P＜0.05)。深刺组临床疗效的总有效率明显高于浅刺组(P＜0.05)，2组不良反应比较差异无统计学意义。结论：廉泉穴深刺联合冰刺激可有效改善中风后吞咽障碍患者吞咽功能，远期效果稳定。     

医用冰毯用于中枢性高热患者的临床观察

医用冰毯用于２１例中枢性高热患者，应用４ｈ后体温平均降至３７℃，降温幅度最大为４．３℃，最小为０．１℃，平均降温１．５℃。２１例患者治疗前后体温经配对ｔ检验，有显著性差异（Ｐ＜０．００１）。