Measurements of Trace Gases in the Inflow of South China Sea Background Air and Outflow of Regional Pollution at Tai O, Southern China

We present a 16-month record of ozone (O₃), carbon monoxide (CO), total reactive nitrogen (NO_y), sulphur dioxide (SO₂), methane (CH₄), C₂ – C₈ non-methane hydrocarbons (NMHCs), C₁ – C₂ halocarbons, and dimethyl sulfide (DMS) measured at a southern China coastal site. The study aimed to establish/update seasonal profiles of chemically active trace gases and pollution tracers in subtropical Asia and to characterize the composition of the `background' atmosphere over the South China Sea (SCS) and of pollution outflow from the industrialized Pearl River Delta (PRD) region and southern China. Most of the measured trace gases of anthropogenic origin exhibited a winter maximum and a summer minimum, while O₃ showed a maximum in autumn which is in contrast to the seasonal behavior of O₃ in rural eastern China and in many mid-latitude remote locations in the western Pacific. The data were segregated into two groups representing the SCS background air and the outflow of regional continental pollution (PRD plus southern China), based on CO mixing ratios and meteorological conditions. NMHCs and halocarbon data were further analyzed to examine the relationships between their variability and atmospheric lifetime and to elucidate the extent of atmospheric processing in the sampled air parcels. The trace gas variability (S) versus lifetime (τ) relationship, defined by the power law, S_lnx = Aτ^{− b}, (where X is the trace gas mixing ratio) gives a fit parameter A of 1.39 and exponent b of 0.42 for SCS air, and A of 2.86 and b of 0.31 for the regional continental air masses. An examination of ln[n-butane]/ln[ethane] versus ln[propane]/ln[ethane] indicates that their relative abundance was dominated by mixing as opposed to photochemistry in both SCS and regional outflow air masses. The very low ratios of ethyne/CO, propane/ethane and toluene/benzene suggest that the SCS air mass has undergone intense atmospheric processing since these gases were released into the atmosphere. Compared to the results from other polluted rural sites and from urban areas, the large values of these species in the outflow of PRD/southern China suggest source(s) emitting higher levels of ethyne, benzene, and toluene, relative to light alkanes. These chemical characteristics could be unique indicators of anthropogenic emissions from southern China.     

温室效应变化及其地理意义

在过去100年间，全球平均气温上升0．3－0．5℃，这种增温幅度与温度效应的预报结果相一致。也与气候变化的自然幅度相一致，由于温室气体效应，现代的气候变化与过去气候变化已有本质不同，经过进一步研究，多数科学家认为，全球变暖主要是大气中的温室气体增加造成的，温室效应变化具有重要的地理意义，增温幅度存在普遍适应的规律。冬季大于夏季，高纬度大于低纬度，陆地大于海洋。植物种群的更新及迁移可能跟不上气候变化的步伐，土壤的形成更将远远落后于气候变化，过渡带的生态系统将长时期内存在，它们将是不稳定的，脆弱的，物种的灭绝速度可能会因此加快，人类对生物资源的利用也许会面临新的问题和挑战。     

西藏地热气体的地球化学特征及其地质意义

西藏水热活动是青苦恼高原碰撞造山过程的产物，其成因类型、物质来源和时空分布与青藏高原的隆升过程密切相关，地热流体（气、液相）中携带有中上地壳乃至地幔物质的深部信息。西藏地热流体可以区分出CO2型和N2型两类气体，其中绝大多数的地热气体样品属于CO2型气体，而典型的N2型气体则较少。前者具有岩浆热源和深循环两种成因类型，后者都是深循环成因。西藏气体样品中的He含量变化范围非常宽，最高的可达到1．5％。在门士热泉，首次检测到地幔He组分，这说明西藏地壳深处有地幔物质侵位。根据He同位素组成推断，羊八井、谷露等处的地壳熔融体中约有3％的地幔组分。西藏地热气体中的N2和Ar组分主要是大气成因，CO2组分大多以海相碳酸盐岩成因为主，混有少量有机沉积物成因CO2。当Log(H2/Ar)处于－0．8－0．3的区间时，H2／Ar地热温度计可以良好地指示热储层的温度范围。实际调查表明：西藏水热活动区大多分布在斑公错－怒江链合带以南地区，高温水热活动区主要出现在雅鲁藏布缝合带和那曲－羊八井－亚东活动构造带沿线。     

Magmatic gas scrubbing: implications for volcano monitoring

Despite the abundance of SO_2(g) in magmatic gases, precursory increases in magmatic SO_2(g) are not always observed prior to volcanic eruption, probably because many terrestrial volcanoes contain abundant groundwater or surface water that scrubs magmatic gases until a dry pathway to the atmosphere is established. To better understand scrubbing and its implications for volcano monitoring, we model thermochemically the reaction of magmatic gases with water. First, we inject a 915°C magmatic gas from Merapi volcano into 25°C air-saturated water (ASW) over a wide range of gas/water mass ratios from 0.0002 to 100 and at a total pressure of 0.1 MPa. Then we model closed-system cooling of the magmatic gas, magmatic gas-ASW mixing at 5.0 MPa, runs with varied temperature and composition of the ASW, a case with a wide range of magmatic–gas compositions, and a reaction of a magmatic gas–ASW mixture with rock. The modeling predicts gas and water compositions, and, in one case, alteration assemblages for a wide range of scrubbing conditions; these results can be compared directly with samples from degassing volcanoes. The modeling suggests that CO_2(g) is the main species to monitor when scrubbing exists; another candidate is H₂S_(g), but it can be affected by reactions with aqueous ferrous iron. In contrast, scrubbing by water will prevent significant SO_2(g) and most HCl_(g) emissions until dry pathways are established, except for moderate HCl_(g) degassing from pH<0.5 hydrothermal waters. Furthermore, it appears that scrubbing will prevent much, if any, SO_2(g) degassing from long-resident boiling hydrothermal systems. Several processes can also decrease or increase H_2(g) emissions during scrubbing making H_2(g) a poor choice to detect changes in magma degassing.We applied the model results to interpret field observations and emission rate data from four eruptions: (1) Crater Peak on Mount Spurr (1992) where, except for a short post-eruptive period, scrubbing appears to have drastically diminished pre-, inter-, and post-eruptive SO_2(g) emissions, but had much less impact on CO_2(g) emissions. (2) Mount St. Helens where scrubbing of SO_2(g) was important prior to and three weeks after the 18 May 1980 eruption. Scrubbing was also active during a period of unrest in the summer of 1998. (3) Mount Pinatubo where early drying out prevented SO_2(g) scrubbing before the climactic 15 June 1991 eruption. (4) The ongoing eruption at Popocatépetl in an arid region of Mexico where there is little evidence of scrubbing.In most eruptive cycles, the impact of scrubbing will be greater during pre- and post-eruptive periods than during the main eruptive and intense passive degassing stages. Therefore, we recommend monitoring the following gases: CO_2(g) and H₂S_(g) in precursory stages; CO_2(g), H₂S_(g), SO_2(g), HCl_(g), and HF_(g) in eruptive and intense passive degassing stages; and CO_2(g) and H₂S_(g) again in the declining stages. CO_2(g) is clearly the main candidate for early emission rate monitoring, although significant early increases in the intensity and geographic distribution of H₂S_(g) emissions should be taken as an important sign of volcanic unrest and a potential precursor. Owing to the difficulty of extracting SO_2(g) from hydrothermal waters, the emergence of >100 t/d (tons per day) of SO_2(g) in addition to CO_2(g) and H₂S_(g) should be taken as a criterion of magma intrusion. Finally, the modeling suggests that the interpretation of gas-ratio data requires a case-by-case evaluation since ratio changes can often be produced by several mechanisms; nevertheless, several gas ratios may provide useful indices for monitoring the drying out of gas pathways.     

Physical mechanisms of man-made influences on the magnetosphere

Since the discovery of the Luxembourg effect in the 1930s, it is clear that man-made activities can perturb the ionosphere and the magnetosphere. The anthropogenic effects are mainly due to different kinds of waves coming from the Earth's surface. Acoustic-gravity waves are generated by large explosions, spacecraft launches, or flight of supersonic planes. Electromagnetic waves are active in different frequency ranges. Power line harmonic radiation which is radiated in the ELF range by electrical power systems can be observed over industrial areas. At VLF and HF, the ground-based transmitters used for communications or radio-navigation heat the ionosphere and change the natural parameters. A large variety of phenomena is observed: wave-particle interaction, precipitation of radiation belt electrons, parametric coupling of EM whistler waves, triggered emissions, frequency shift, and whistler spectrum broadening. This paper will review the different physical mechanisms which are relevant to such perturbations. The possibility of direct chemical pollution in the ionosphere due to gas releases is also discussed.     

Noble gases dissolved in groundwater in a volcanic aquifer: Helium isotopes in the Kumamoto Plain

This study Investigates a tracing method using dissolved noble gases to survey the groundwater flow in a large groundwater basin. The tracing method is based on measuring the concentrations of noble gases and the ratio of helium isotopes in groundwater samples. Since it is very difficult to detect trace amounts of noble gases and helium with high accuracy in a 15-ml groundwater sample, dissolved gases were extracted and purified, then a high-resolution mass spectrometer was used for measurement and comparison with standard samples. We used this method with samples from a confined aquifer formed by the deposition of pyroclastic flow in the Kumamoto Plain on the west side of Mt. Aso in central Kyushu, Japan. The groundwater basin under the plain is divided into four small basins, based on the helium concentrations and isotope ratios, with two major groundwater flows. One flow is buried by the Aso pyroclastic flow along the old Kase River; the other is along the Tsuboi River Valley. These two groundwater flows were identified from the different helium isotope-ratios. The helium component from the deep mantle is mixed into the groundwater under the Kumamoto Plain. Finally, data on the concentrations and ratios of³He to⁴He in groundwater samples were used to determine the location of faults in the volcanic aquifer.     

Natural gas generation model and its response in accumulated fluids in the Yinggehai basin

The generation of natural gases is much more complicated in comparison with liquid petro-leum in that natural gases could be generated from both humic and sapropelic organic matter at different stages and that natural gases could be organic and inorganic …     

东海天然气水合物地热研究及其环境意义

依据地热资料研究天然气水合物稳定带厚度在东海海域的分布情况。东海在地质构造上位于新生代环太平洋构造带西部边缘岛弧的内侧,又是欧亚板块、太平洋板块和菲律宾海板块的相互作用带。依据国际热流委员会(IHFC)提供的东海地热数据,经过统计确定出该区域的热流分布,热流平均值为121·0mW/m2,最小值为73·0mW/m2,最大值为168·0mW/m2。同时利用天然气水合物温压模型计算了稳定带厚度,数据显示稳定带厚度平均值为92·2m,最小值为1·4m,最大值为190·6m,薄于其他已经发现的海洋天然气水合物稳定带厚度(约400m)。天然气水合物大部分分布在条件适宜的陆坡和岛坡上,冲绳海槽底部水合物稳定带厚度相对较薄。统计分析表明本区热流值与水合物稳定带厚度相关性很差,相关系数仅有0·12。这是由于天然气水合物所在海域水深较浅时,海底温度的变化迫使运算所应用的非线性方程影响因子迅速积累,从而导致相关系数降低。最后结合东海陆坡的地质条件,探讨了在天然气水合物存在的情况下,陆坡失稳的可能性及其造成的环境影响。     

西太平洋海底海山富钴结壳惰性气体同位素组成及其来源

采用高真空气体质谱系统测定了西太平洋麦哲伦海山富钴结壳不同层圈及其基岩的惰性气体丰度和同位素组成,结果显示:(1)西太平洋富钴结壳主要是水成成因,其中惰性气体来源不同,He 绝大多数来自宇宙尘(IDPs),少量来自陆源风成微粒;Ar 主要来自海水溶解的大气,少量来自陆源风成微粒或沉积岩建造水;Ne 和 Xe 主要来自海水中溶解大气, 少量来自宇宙尘;(2)在具三层结构的结壳中,亮煤层(致密层)的惰性气体同位素相对外层和疏松层有较大的不同,显示大洋磷酸岩化对早期沉积的结壳惰性气体组成有较大的影响,如导致~4He 的升高和~3He/~4He 的显著降低;(3)太平洋富钴结壳玄武岩基岩的~3He/~4He 非常低,为0.0095～0.074Ra,与本区磷块岩基岩(0.087Ra)相似,而远低于正常海底玄武岩的~3He/~4He 比值,显示这些基岩曾与富含放射性成因~4He 和 P 的上升洋流或沉积物中建造水发生过水/岩反应,这个过程将释放出较多的成矿元素,有利于富钴结壳的形成,海底海山玄武岩中较低的 He 同位素组成可作为富钴结壳的找矿标志之一。     

温室气体源汇及其对气候影响的研究现状

温室气体对全球气候变化将产生深远的影响。本文拟从温室气体源汇研究以及温室气体对气候环境的影响等方面论述温室气体研究进展。尽管目前国内外对主要的温室气体源与汇研究报道很多,但不同的研究结果不尽一致,有些研究间甚至出现相反的结论。温室气体增加对气候的影响及其检测,主要是利用不同复杂程度的数值模式进行研究。