Just like contemporary sediments, peat itself is a good repository of information about climate change, the effects of volcanic activity on climate change have been truly recorded in peat, since it is a major archive of volcanic eruption incidents. A section of sand was identified as tephra from the Jinchuan peat, Jilin Province, China, for the grains look like slag with surface bubbles and pits, characterized by high porosity, and loose structure with irregular edges and corners. According to the peat characteristics of uniform deposition, the tephra was dated at 2002-1976 a B.P. by way of linear interpolation, so the time of volcanic eruption was 15 B.C.-26 A.D. (the calibrated age). While the geochemical characteristics of tephra in this study are quite the same as those of tephra from the Jinlongdingzi volcano at Longgang and from alkaline basaltic magma, with the contents of SiO2<55%, and the similar contents to Al2O3 and Fe, but the contents of Na2O>K2O. We speculated that the tephra in this study came from the Longgang volcano group. Compared with 11 recorded volcanic eruption events as shown on the carbon and oxygen isotope curves of the Jinchuan peat cellulose, it is obviously seen that adjacent or large-scale volcanic eruptions are precisely corresponding to the minimum temperature and humidity. It seems that these volcanic eruptions indeed affected the local climate, leading to the drop of regional temperature and humidity. As a result, there was prevailing a cold and dry climate there, and all these changes can be well recorded in peat. So the comparison of volcanic eruption events with information about climate change developed from peat, can provide strong evidence for the impact of volcanism on climate change.
MAO XumeiCHENG ShenggaoHONG YetangZHU YongxuanWANG Fenglin
CO2-rich cold springs occur near the active volcanoes at Wudalianchi （五大连池）, Northeast China. The springs are rich in CO2, with HCO3-as the predominant anion and have elevated contents of total dissolved solid （TDS） （〉1 000 mg/L）, Fe^2＋ （〉20 mg/L）, Sr （〉1 mg/L）, and dissolved Si （〉20 mg/L）. The compositions of escaped and dissolved gases of the springs are similar. The δ^13C values of escaped gases and dissolved gases in mineral springs at Wudalianchi vary from -8.77‰ to -4.53‰ and -8.24‰ to -5.26‰, while δ^18O values vary from -10.68‰ to -7.65‰ and -10.30‰ to -8.84‰, respectively, indicating the same upper mantle origin of CO2 of escaped gases and dissolved gases in the springs. Carbon and oxygen isotope fractionations and water-CO2 exchange were weak in the process of groundwater flow. The 4He content exceeds 5 000×10-6 cm^3·STP/mL in escaped gases of the mineral springs, and the 3He/4He ratios of the escaped and dissolved gases vary from 2.64Ra to 3.87Ra and 1.18Ra to 3.30Ra, respectively. It can be postulated that the CO2 of mineral springs deriving from the magma chamber of the upper mantle moves upward to the surface, to increase the content of 4He in the mineral springs and decrease the ratio of 3He/4He. The helium origin of escaped gases in springs can be calculated with the MORB-crust mixing model, but that in the north spring can be better explained with the MORB-crust-air mixing model due to the effect of mixing with surface water. However, dissolved helium in springs, except the north spring, is better explained with the MORB-crust-ASW mixing model.
Floating tephra was deposited together with ice core, snow layer, abyssal sediment, lake sediments, and other geological records. It is of great significance to interpret the impact on the climate change of volcanic eruptions from these geological records. It is the first time that volcanic glass was discovered from the peat of Jinchuan （金川） Maar, Jilin （吉林） Province, China. And it is in situ sediments from a near-source explosive eruption according to particle size analysis and identification results. The tephra were neither from Tianchi （天池） volcano eruptions, Changbai （长白） Mountain, nor from Jinlongdingzi （金龙顶子） volcano about 1 600 aBP eruption, but maybe from an unknown eruption of Longgang （龙岗） volcano group according to their geochemistry and distribution. Geochemical characters of the tephra are similar to those of Jinglongdingzi, which are poor in silica, deficient in alkali, Na2O content is more than K2O content, and are similar to distribution patterns of REE and incompatible elements, which helps to speculate that they originated from the same mantle magma with rare condemnation, and from basaltic explosive eruption of Longgang volcano group. The tephra, from peat with age proved that the eruption possibly happened in 15 BC-26 AD, is one of Longgang volcano group eruption that was not recorded and is earlier than that of Jinglongdingzi about 1 600 aBP eruption. And the sedimentary time of tephra is during the period of low temperature alteration, which may be the influence of eruption toward the local climate according to the correlativity of eruption to local temperature curve of peat cellulose oxygen isotope.
The increase of CO2 in atmosphere is a main factor leading to "greenhouse effect", which causes more and more serious global environmental problems. The reduction of CO2 is a challenge for the survival of human beings, and it is also a big technical problem. CO2 fluid-rock interaction is a key scientific problem involved in geo-logical storage. The CO2 fluid-rock interaction has a variety of multi-scale changes. Due to great differences in the quantity of surface atoms and surface energy between micron-nano-sized minerals, and ions and crystals, the speed and efficiency of CO2 fluid-rock interaction on a micron-nano scale are much higher than those on other scales. As is known from the natural world, the micron-nano structures of pores and the surface chemical modification of natural porous minerals (zeolite, diatomite, sepiolite, palygorskite, halloysite, etc.) should be further investigated, which can be used as the micron-nano -mineral porous materials with high capacity and high efficiency for capturing CO2. Through simulating the adsorption capacity and process of CO2 by minerals in the natural world, the micron-nano technology is applied to calcium- and magnesium-based minerals (olivine, pyroxene, feldspar, clay, etc.) so as to improve the activity of calcium and magnesium and enlarge the reaction contact area. In this way, the efficiency of capturing and storage of CO2 by calcium- and magnesium-based minerals can be greatly improved. These minerals can also be used as the micron-nano-mineral materials with large capacity and high efficiency for capturing and storing CO2.
