神农架大九湖泥炭地孔隙水溶解有机碳特征及其影响因素

溶解性有机碳（Dissolved Organic Carbon, DOC）是泥炭地碳循环的重要组成部分。以往的研究大多集中在北方泥炭地，而对亚热带季风区泥炭地DOC动力学的认识十分有限。利用紫外可见光光谱（UV-Vis）和三维荧光光谱结合平行因子分析法（EEM-PARAFAC）研究了神农架大九湖泥炭地孔隙水的DOC浓度与化学组成及其影响因素。EEM-PARAFAC的结果表明：大九湖泥炭地孔隙水DOC主要包含3种类腐殖质组分。紫外可见光和荧光指标表明，泥炭孔隙水DOC表观分子较小，而芳香度较高。深度剖面数据表明，泥炭孔隙水DOC浓度随深度降低，0~10 cm深度浓度最高为24.16 mg/L，150~160 cm深度浓度最低为9.72 mg/L，并且深层DOC以微生物代谢产生的新鲜有机物为主，具有较低的腐殖化度。此外，氧化还原电位（ORP）与DOC浓度及化学性质关系密切。以上结果表明，在亚热带泥炭地中，微生物来源或受微生物改造的有机物是泥炭孔隙水DOC的重要组成部分；垂向输送或选择性保存是影响该亚热带亚高山泥炭地DOC动力学的重要因素。     

兰州与江汉平原有机碳同位素的古气候指示意义对比研究

选择以干冷气候为主的兰州和温暖湿润的江汉平原作为研究区域,结合其他多种指标和研究区的岩性特征,对有机碳同位素δ13Corg的古气候指示意义进行了初步探讨。结果表明,在兰州地区,δ13Corg值波动反映C3/C4植物比例的改变,指示温度变化。δ13Corg值偏正时,表明C4植物含量较大,反映温度较高,而δ13Corg值偏负时,表明气候较冷;江汉平原δ13Corg值主要反映降水信息, δ13Corg值偏负时指示相对暖湿气候,δ13Corg值偏正反映气候偏干。δ13Corg等指标同时还揭示了末次盛冰期以来两地古气候类同特征：即12.0 ka BP之前气候相对偏干;在全新世晚期,气候波动中转暖。不同之处表现为：约在12.0~10.0 ka BP,当兰州气候还很干冷时,江汉平原已进入暖湿的冰后期;而在全新世早中期,当兰州气候转为暖湿时,江汉平原气候则表现为略偏干。     

汉江辽瓦店全新世黄土-古土壤序列风化过程及古洪水事件记录

对汉江上游谷地包含古洪水滞流沉积层的辽瓦店(LWD)全新世黄土-古土壤剖面的常量元素含量、粘粒含量、磁化率和Rb/Sr比值等指标进行了对比分析。结果发现:在LWD剖面的风化成壤过程中,元素Na、Mg和Al表现为较强烈的迁移淋失,虽然元素K、Fe和Ca有一定程度的迁移淋失,但比较微弱,呈现NaMgAlKFeCaSi的迁移序列;磁化率、Rb/Sr、CIA值、钾纳比(K2O/N2O)和淋溶系数的分布随地层的变化而同步变化。上述变化指示古土壤S0形成时期,气候温暖湿润,成壤作用强烈,马兰黄土L1堆积时期气候寒冷干旱,风化成壤作用最弱,黄土L0堆积时期气候有所好转,风化成壤作用强于马兰黄土堆积时期,但弱于古土壤形成时期。古土壤S0形成的全新世中期可能出现过一次较为暖湿的次级环境变化,在剖面中上部夹有一层古洪水滞流沉积层(SWD),呈灰白色(10YR6/1),为十分均匀的细粉砂,与上下相邻地层呈突变接触关系且界线清晰,向垂直河岸方向快速尖灭,是一次剧烈的气候突变事件的产物。     

汉江上游前坊村黄土剖面化学风化程度及其环境意义

通过对郧县前坊村黄土剖面常量元素及相关参数分析,采用Al为标准的变化率参数计算。结果表明：(1)古土壤S0形成时期，土壤磁化率、粘粒成分、CIA值较典型黄土L1高，Na/K值低于典型黄土L1。这表明古土壤形成时期，气候温暖湿润，土壤风化淋溶较强,反映了较强的成壤过程，在黄土堆积时期气候相对干冷，沙尘暴频繁出现，土壤的成壤作用较弱；(2)碳酸盐含量的剧烈变化是影响黄土元素分布特征很重要的因素，其中,一些元素如Mn和Fe在剖面中的含量较高，主要是碳酸盐被强烈淋溶造成的相对富集；(3)前坊村剖面中，常量元素风化成土过程中，Na、Ca、Mg、K、Si和Ti在古土壤S0为主要迁移元素，其迁移顺序为：Na>Ca>Mg>K>Si>Ti；Mn和Fe表现的轻微富集；常量元素的迁移特征指示了汉江上游谷地黄土已经完成初级的脱Ca、Na阶段，应进入了早期去K的中等风化阶段     

长江中游砂山的磁组构特征及古气候环境意义

为了建立长江中游风成砂的磁组构识别标志,讨论磁组构参数与古气候、古环境之间的关系,对新近发现的江西九江新港砂山剖面进行了野外考察和磁化率定向样品的采集和测试,结果表明：①新港风成砂剖面中砂层和古土壤化的亚黏土层的磁组构参数值具有较大的不同,亚黏土层的磁化率（〖WTBX〗κ〖WTBZ〗）在剖面中表现为峰值（均值143.27（10-6SI））,各向异性度（〖WTBX〗P〖WTBZ〗）值却表现为曲线的较低值段。砂层却与亚黏土层相反,〖WTBX〗κ〖WTBZ〗值为谷值（均值为2181（10-6SI））,〖WTBX〗P〖WTBZ〗值总体为高值段,但波动较大。②在新港风成砂剖面中大多数亚黏土层样品的磁面理度（〖WTBX〗F〖WTBZ〗）值大于磁线理度（〖WTBX〗L〖WTBZ〗）,而砂层中只有部分样品的〖WTBX〗F值大于L〖WTBZ〗,说明亚黏土层的磁面理发育程度较砂层的要好。③相对于河流和湖泊沉积物（河流沉积物长轴的倾角一般小于10°,短轴的倾角大于80°）而言,新港剖面风成砂的磁化率量值椭球体的长轴的倾角较大（22°～24°）,短轴的倾角较小（45°～51°）。④新港剖面风成砂的磁基质颗粒度（〖WTBX〗q〖WTBZ〗）的平均值（0668 8）比长江中游河流沉积物的〖WTBX〗q〖WTBZ〗值（024）偏大,反映风成砂的分选较河流沉积物的要差。上述特点可作为长江中游水成和风成沉积物的磁组构识别标志。⑤在325～262 m的地层剖面中共有9层发育程度不同的古土壤化的亚黏土层,说明在这一期间气候不仅有9次由干冷向暖湿的转变,且每次变化的强度也有所不同。〖     

湖北郧西县庹家湾剖面粒度组成特征及其环境意义

对湖北省郧西县庹家湾(TJW)剖面的地层序列、年代、磁化率及粒度组成进行研究。结果表明:TJW剖面具有表土(MS)→全新世黄土(L0)→古土壤(S0)→过渡层(Lt)→马兰黄土(L1)→黄土与砂互层(T1-al2)→砾石层(T1-al1)的地层序列;在马兰黄土层上部的黏粒含量、黏粒/粉砂值以及磁化率值明显高于典型马兰黄土,而接近古土壤(S0),其成壤作用明显,属于较典型的弱古土壤层(L1-S1和L1-S2),其年龄在27.3~21.6 ka B.P.之间。此现象反映了在汉江上游地区,晚更新世时期的冰期气候并不是持续稳定的,在27.3~21.6 ka B.P.期间存在相对短暂的温暖湿润阶段,这次气候事件可与黄土高原地区进行良好对比。     

Holocene dynamics of vegetation and ecological conditions in the southern Yamal Peninsula according to the results of comprehensive analysis of a relict peat bog deposit

A comprehensive analysis of samples from a frozen peat deposit in the upper reaches of the Khadytayakha River by palynological, carpological, entomological, and radiocarbon methods has been performed to reconstruct changes in the regional and local vegetation and climatic conditions during the Holocene. The results show that this peat deposit was formed from 8000 to 5000 years BP. During that period, the climate in the southern Yamal Peninsula was considerably warmer, and the present-day subarctic shrub tundra zone was occupied by plant communities of spruce, birch, and larch forests.     

The holocene dynamics of vegetation and environmental conditions on the eastern slope of the Northern Urals

Consideration is given to changes in the vegetation and climatic conditions on the eastern slope of the Northern Urals in the second half of the Holocene as reconstructed on the basis of integrated palynological, botanical, paleocarpological, and radiocarbon analysis of material from a peat bog section in the floodplain of the Loz’va River. The results show that the northern taiga zone of the study region in the period between approximately 5000 and 700 years BP was occupied by forests of southern taiga facies, as the climate was significantly warmer than it is today.     

Climatic dependence of the Late Holocene dynamics of tree species cenotypes in the intrazonal ecotone of Eastern Sayan forests

A comprehensive study of paleobotanical materials collected in the northern part of the Eastern Sayan was performed, including botanical analysis of peat, palynological and carpological analysis, and radiocarbon dating. The results provided a basis for reconstructing in detail the spatiotemporal distribution of ecocenotic complexes and corresponding paleoclimate types and calculating quantitative gradients of heat and moisture supply in the Late Holocene, beginning from 3500 ka.     

Evidence for a warm and humid Mid-Holocene episode in the Aegean and northern Levantine Seas (Greece,NE Mediterranean)

Marine and terrestrial biological and biogeochemical proxies in three sediment cores from North and SE Aegean and northern Levantine Seas record continuous warm and humid conditions between 5.5 and 4.0 ka BP related to the establishment of relatively stratified conditions in the upper water column. These conditions may have resulted from the concordant albeit weak Mid-Holocene South Asian monsoon forcing, combined with lighter Etesian winds. During this interval, sea surface temperatures fluctuate in the Aegean Sea, although exhibiting a strong positive shift at ~4.8 ka BP. The warm and humid climatic conditions triggered upper water column stratification and enhancement of the deep chlorophyll maximum (DCM), leading to dysoxic conditions and the deposition of a sapropel-like layer, but only in the SE Aegean site. In contrast to the shallow water SE Aegean, the deeper North Aegean and the northern Levantine sites, although experiencing stratification in the upper parts of the water column, did not achieve bottom-water dysoxia. Thus, a top–bottom mechanism of stratification–DCM development accompanied by fast transport and burial of organic matter is a likely explanation for the preservation of productivity signal in the shallow sites of the SE Aegean and establishment of sapropelic conditions during the warm and humid Mid-Holocene. The termination of the Mid-Holocene warm and humid phase coincides with the “4.2 ka” climate event. Our data exhibit an N–S time transgressive aridification gradient around the Aegean Sea, most probably associated with the reorganization of the general atmospheric circulation during the Mid-Holocene.     

The Holocene dynamics of vegetation and climatic conditions on the eastern slope of the Subpolar Urals

Changes in the vegetation and climatic conditions on the eastern slope of the Subpolar Urals over the past 10000 years have been reconstructed on the basis of integrated palynological, botanical, and radiocarbon analysis of material from two sections of peat deposits in the floodplains of the Lyapin and Man’ya rivers (the Severnaya Sos’va basin). The dynamics of regional vegetation have been traced: from the herb–shrub tundra in the late postglacial time to the spruce–larch forest–tundra and sparse larch–birch–spruce stands in the Early Holocene, to birch–pine–spruce forests with an admixture of fir in the Middle Holocene, and to northern taiga forests with dominance of Scots pine and Siberian stone pine (similar to present-day forests) in the Late Holocene. The results show that the northern taiga zone of the study region in the period between approximately 5500 and 2500 years BP was occupied by forests of middle and southern taiga facies, as the climate was significantly warmer than it is today.