Dissolved organic carbon concentration and its seasonal variation in the Huguangyan Maar Lake of Southern China

The dissolved organic carbon(DOC)in the surface water of Huguangyan Maar Lake was continuously monitored based on once per week sampling frequency of 4 locations from June 2018 to May 2019.The DOC concentrations and its seasonal variation were discussed by correlating with the rainfall,water temperature,and p H of lake water.The results showed that the weekly DOC varied from 8.15 to 32.65 mg/L with an annual average concentration of 17.96 mg/L.There was a significant difference in the average DOC concentrations between the rainy and dry seasons as the monthly average DOC concentration was 21.72 mg/L for the wet season compared to the dry season concentration of 14.21 mg/L.The rainfall shows a significant effect on the DOC concentration of lake water,as DOC concentration was much high during the wet season.There were no significant spatial variations in the average monthly concentration among the four sampling locations except occasional variation during the wet season.The reason for the wet season DOC differences among four sampling locations is likely due to the uneven runoff and underground water inputs and the relatively slow circulation of lake water.Finally,the seasonal fluctuation of DOC concentration in this closed lake water suggests that dissolved soil organic matter inputs through the rainfall related to surface runoff and subsurface infiltration from the surrounding watershed land is important to the primary production and organic matter deposition in the lake sediments.

Tracing the Provenance of the Huguangyan Maar Lake Sediments in Coastal Regions of South China

The Huguangyan Maar Lake（HML）（21°9＇N,110°17＇E）,situated on the Leizhou Peninsula in the southernmost of China's Mainland,is the deepest recent crater lake among the identified volcanic structures in the Leiqiong Volcanic Field.The bi-lobate lake.

Microbial diversity in Huguangyan Maar Lake of China revealed by high-throughput sequencing

Huguangyan Maar Lake is a typical maar lake in the southeast of China. It is well preserved and not disturbed by anthropogenic activities. In this study, microbial community structures in sediment and water samples from Huguangyan Maar Lake were investigated using a high-throughput sequencing method. We found significant differences between the microbial community compositions of the water and the sediment. The sediment samples contained more diverse Bacteria and Archaea than did the water samples. Actinobacteria, Betaproteobacteria, Cyanobacteria, and Deltaproteobacteria predominated in the water samples while Deltaproteobacteria, Anaerolineae, Nitrospira, and Dehalococcoidia were the major bacterial groups in the sediment. As for Archaea, Woesearchaeota (DHVEG-6), unclassified Archaea, and Deep Sea Euryarchaeotic Group were detected at higher abundances in the water, whereas the Miscellaneous Crenarchaeotic Group, Thermoplasmata, and Methanomicrobia were significantly more abundant in the sediment. Interactions between Bacteria and Archaea were common in both the water column and the sediment. The concentrations of major nutrients (NO^3-, PO4^3-, SiO3^2- and NH4^+) shaped the microbial population structures in the water. At the higher phylogenetic levels including phylum and class, many of the dominant groups were those that were also abundant in other lakes;however, novel microbial populations (unclassified) were often seen at the lower phylogenetic levels. Our study lays a foundation for examining microbial biogeochemical cycling in sequestered lakes or reservoirs.

Periodicity of Holocene climatic variations in the Huguangyan Maar Lake

There exist five primary periods of 2 930, 1 140, 490, 250 and 220 a in the Holocene climatic variations in the Huguangyan Maar Lake, according to the energy-spectrum and filter analyses of high-resolution time sequences (10-15 a) of the sediment dry density. The peak values of the three temperature-decreasing periods with the 2 930 a cycle occur at about 7 300, 4 250 and 1 200 Cal. aBP. There are 7-8 temperature-decreasing periods with the 1 140 a cycle, and the climate fluctuation range is largest in the early Holocene, and reduces gradually in the middle and late Holocene. The millennial-scale climatic change in the Holocene may adjust the global water cycle and the thermohaline circulation intensity through the harmonic tones of the earth’s precession cycle, which in turn influences the global climate change.

The early Holocene optimum inferred from a high-resolution pollen record of Huguangyan Maar Lake in southern China

A high-resolution pollen record of the past 13000 a from Huguangyan Maar Lake reveals the vegetation and environment changes in southern China during the Holocene. It shows that (i) pollen percentage of trees and shrubs reached 56% during the early Holocene (11600―7800 cal a BP), of which the pollen percentage of tropical trees reached a maximum at 9500―8000 cal a BP, reflecting a hot and wet envi- ronment; (ii) during the mid-Holocene (7800―4200 cal a BP), the pollen percentage of montane conif- erous trees and herbs increased, while the percentage of tropical-subtropical trees decreased, indi- cating lower temperature and humidity; (iii) in the late Holocene spanning from 4200 to 350 cal a BP, the pollen percentage of herbs and montane conifer increased significantly, indicating a marked decrease of temperature and humidity. Our pollen data reveal that the time period 9500―8000 cal a BP in south- ern China represents a climatic optimum for the Holocene characterized by hot and wet conditions. This is consistent with the Holocene optimum found in lower latitude regions globally. We speculate that strong insolation might cause the northward migration of the ITCZ and subtropical summer mon- soon front, which resulted in an early Holocene optimum in the Huguangyan area. The dry tendency and climate fluctuations of the middle and late Holocene could be associated with a decrease in solar insolation and frequent ENSO event.

High-resolution climate evolution derived from the sediment records of Erlongwan Maar Lake since 14 ka BP

Varve counts with AMS 14 C,137 Cs and 210 Pb dating of sediments(0-900 cm) from Erlongwan Maar Lake,NE China were used to establish a high-resolution chronology series for the late Quaternary.Dry density,total organic carbon(TOC) content,total nitrogen(TN) content,TOC/TN ratios and stable organic carbon isotope(13 C org) ratios were continuously analyzed on this sediment profile.On the basis of lithological characters,sporo-pollen assemblages and geochemical analyses,we identified 6 climate stages within the last 14 ka BP.The time before the Holocene(14-11.4 ka BP) represents a higher-order oscillation climatic transitional period(I).The entire Holocene climate development(from 11.4 ka BP to present) exhibited an increasing temperature trend,although there were cold and warm alternations(II-VI).The periods included were:II(11.4-9.05 ka BP) warm-wet stage,III(9.05-7.4 ka BP) cold and warm fluctuation stage,IV(7.4-4.2 ka BP) smoothly warming climate stage,V(4.2-1.67 ka BP) climate optimum stage,and VI(from 1.67 ka BP to present) cool and drier stage.Each climate stage began with a warming event and ended with an abrupt cooling event.This climate change cycle had unequal time spaces that were progressively shorter over time.Several abrupt climate shifts occurred at about 9.4-9.05,8.5-8.2,7.8-7.4,4.6-4.2,3.7-3.25,2-1.67 and 0.3-0.03 ka BP.Thus,it can be seen that the climate has been warming since 1920 AD,which indicates a new climate stage.

High-resolution records of Holocene from the Shuangchi Maar Lake in Hainan Island

The results of sedimentary characteristics, grain-size, clay mineral, C/N and pollen analysis reveal the evolution history of the Shuangchi Maar Lake of Hainan Island as well as the short-term climate variations in tropical areas. It is testified that the Maar sediment system was sensitive in recording the rapid climate changes in the Holocene. These multidisciplinary results demonstrate that the thermal maximum in the Holocene climate lasted from 7200 to 2700 aBP, with several abrupt ephemeral vibrations occurring between 7250-6120 aBP and at around 4460, 3850 and 2700 aBP. In the late Holocene, particularly at ~2700 aBP, a distinct environmental change indicating an important climate transition in the tropical eastern Asia was recorded, probably responding to the enhancement of ENSO phenomena in the Pacific Ocean. In addition, the high-resolution algae record clearly indicates periodical climate fluctuations at 500 a cyclicity during the last 2500 years.

The two-step monsoon changes of the last deglaciation recorded in tropical Maar Lake Huguangyan,southern China

The concentrations of biogenic silica, total organic carbon, total nitrogen and total hydrogen inferred from the sediments of tropical Maar Lake Huguangyan, southern China, provide a climate record of the last deglaciation with century resolution. The records fully demonstrate the existence of the two-step shape of the last deglaciation in tropic East Asia, and they point out noticeable differences between the low and high latitudes in the Northern Hemisphere. Thus, the Boiling first warming at the last deglaciation in the low latitude may have preceded that of the high latitude, whereas the cooling of the Younger Dryas occurred synchronously in the two regions. These results likely suggest that the links between the low and high latitude climates in the Northern Hemisphere during this period are complexity.

Discrimination of two kinds of sedimentary laminae in maar lakes of China

Varved lacustrine sediments have been found from high latitude to low latitude, even in tropical area. Paleoenvironmental and paleoclimatic research has increasingly relied on the use of varved sediments to provide high-resolution geochronologies and climatic reconstructions. However, a special depositional environment is necessary for varve formation and preservation. Generally, varves can be found in the sediments of maar lakes because of their special geological and hydrological environment. The preliminary research showed that a few carbonate laminations are developed in the Huguangyan maar lake, south China. They are poorly developed and not annual laminations, and may be related to periodically drought. Diatomaceous laminations are found in the maar lakes in northeast China. Diatomaceous laminations with cyclic nature corresponding with seasonal diatom blooming are the credible natural clock.

湛江湖光岩玛珥湖沿岸植物正构烷烃分布特征及其H同位素组成

从湛江湖光岩玛珥湖沿岸随机采集主要的草本和木本植物,分析其叶蜡正构烷烃分布特征及单体H同位素(δ^(2)H)。结果表明,湖光岩玛珥湖沿岸植物叶蜡正构烷烃主要由长链烷烃(n-C29~n-C31)组成,具有明显的奇偶优势;平均碳链长度(ACL值)与碳优势指数(CPI值)呈负相关关系;不同种类植物之间的正构烷烃δ^(2)H值差异明显,木本植物正构烷烃的δ^(2)H值(-247‰~-107‰)比草本植物(-222‰~-94‰)低,可能与它们的内在特性和所利用的土壤水深度有关。通过对比不同生境下低、中、高纬度地区湖泊沿岸植物叶蜡正构烷烃δ^(2)H值发现,低纬度热带、亚热带地区的植物叶蜡正构烷烃具有更长的链长和更高的δ^(2)H值,但植物与降水之间的δ^(2)H分馏值随纬度变化相对恒定(约-120‰),说明湖泊生境沉积叶蜡正构烷烃单体δ^(2)H值是具有较大潜力的古水文代用指标。

湖光岩玛珥湖沉积物雨水芳烃化合物组成研究

该文利用气相色谱-质谱联用仪,对大气降水、湖光岩玛珥湖表层湖水和沉积物中16种优控多环芳烃(PAHs)化合物进行研究。结果表明:(1)大气降水和表层湖水中检出15种优控PAHs,总浓度分别为244.78 ng/L和117.31 ng/L;沉积物中检出16种优控PAHs,总浓度为304.42 ng/g。大气降水、表层湖水、沉积物中2~3环PAHs占比呈顺序降低,4~6环PAHs占比呈顺序递增。(2)大气降水中Chr、BbF、BkF、BaP、IcdP致癌单体多环芳烃含量超过标准规定限值,BaA略低于标准规定限值;湖光岩玛珥湖表层湖水中的BaA、BbF、BkF、BaP等致癌性多环芳烃化合物含量低于标准规定的限值,Chr和IcdP含量略高于标准规定的限值。(3)湖光岩玛珥湖沉积物中Nap、Acy、Ace、Flu、Phe、Ant、Fla、Pyr、BaA、Chr、BaP、DahA化合物含量均远低于沉积物质量基准值ERL,无生态风险。而尚无规定安全值的BbF、BkF、InP和BghiP的生态风险需要进一步关注。总体上湖光岩玛珥湖表层湖水和沉积物PAHs生态风险低。

Eckfeld Maar:Window into an Eocene Terrestrial Habitat in Central Europe

To mark the occasion of the 175th anniversary of the Rheinische Naturforschende Gesellschaft in 2009 and of the centennial of the Mainz Natural History Museum in 2010, we present a short account of our present knowledge of the Eckfeld Maar after 20 years of continuous research. This paper does not attempt to include all of the detailed results on the geology of the Eckfeld site or its biota. To date, nearly 250 papers and books have been published since the start of our project. An up-to-date list of these publications can be found at www.eckfeldermaar.de.

近百年来二龙湾沉积物粒度端元分析及其环境意义

沉积物粒度蕴含着区域降水强度、湖泊水位波动、沉积物物源等古环境信息。文章以二龙湾2个沉积物岩芯为研究对象,利用GMX30P-A高纯Ge同轴探测器和英国Mastersize2000型激光粒度仪对样品进行137Cs比活度和粒度测试,运用参数化EMA端元模型对沉积物样品的粒度数据集进行端元分解,探讨二龙湾近百年来沉积物质来源和沉积环境特征。二龙湾沉积物主要为水成沉积,含少量风成沉积,EM1和EM2指示水动力较弱的封闭湖泊沉积环境,EM3指示强地表径流搬运过程。坡面径流挟带的流域碎屑颗粒物是沉积物的主要物源,高空西风携带的远源粘粒级颗粒和中尺度区域风搬运的近源粉尘物质对沉积物有一定的贡献。近百年来二龙湾经历封闭湖泊沉积过程,沉积环境较为稳定,湖心沉积速率小于近岸沉积速率。1963年后沉积物中细颗粒物质含量增加,粗颗粒物质占比大幅下降,表明吉林龙湾国家级然保护区的建成对流域的水土保持有重要作用。

引发2021—2022年度湖光岩玛珥湖水华事件的主要藻种及原因分析

水华(algal bloom)是水体中藻类过度繁殖所引起的生态环境问题,水华的暴发会对水体环境以及水生生态平衡造成严重的破坏.湖光岩玛珥湖是低平地区火山口形成的湖泊,具有相对封闭的水体环境,是研究认识较为单纯的水文条件下水华形成与发展的理想场所,研究其水华暴发期间的主要藻种构成及水生态环境条件对认识水华形成的原因具有积极的意义.本文对2021年12月—2022年3月期间湖光岩水华暴发的主要藻类进行了分析鉴定,并从营养盐条件、水文条件、气象因素等方面探讨分析湖光岩水华暴发的原因.结果表明:(1)湖光岩水华暴发的主要藻种为绿藻门中的小球藻(Chlorella vulgaris)以及蓝藻门中的铜绿微囊藻(Microcystis aeruginosa);(2)湖光岩表层水营养盐含量分析显示,SiO_(3)^(2−)-Si的含量最高,PO_(4)^(3−)-P的含量最低,NO_(2)^(−)-N、NO_(3)^(-)-N、NH_(4)^(+)-N的含量在不同采样点基本保持稳定,而与前人在没有发生水华的年份所做的湖光岩水体营养盐含量分析相比,水华期间SiO_(3)^(2−)-Si、PO_(4)^(3−)-P以及NH4^(+)-N的含量显著增加,而其他营养盐组分则变化不大,PO_(4)^(3−)-P、NH4^(+)-N为调控湖光岩浮游藻类生长的重要营养盐因子,因此水体中PO_(4)^(3−)-P、NH_(4)^(+)-N含量的增加是造成湖光岩发生水华的主要原因;(3)湖光岩水华的暴发主要与水体中营养盐的浓度变化有关,而适宜的水文环境以及气候条件等也有利于水华的暴发.

62 kaBP以来湖光岩玛珥湖沉积物有机碳同位素记录及古气候环境意义

湖光岩玛珥湖HUG B孔岩心记录了62kaBP以来的古气候、古环境变化信息。全岩有机碳同位素组成(δ13CTOC)分析表明,62kaBP以来δ13CTOC值变化比较明显,其变化范围为-28.5‰～-15.5‰。结合孢粉和有机地球化学指标进行综合分析,湖光岩玛珥湖δ13CTOC变化曲线可划分为6个演化阶段:62～58和48～40.5kaBP两个时段的δ13CTOC值偏负,沉积物中有机质主要来源于热带—亚热带地区的陆生C3森林植被,反映了温暖潮湿的气候环境;58～48和40.5～17.2kaBP期间δ13CTOC值明显偏正,沉积物中有机质主要源自C4草本植物,反映了湖光岩地区有效降水量减少、干旱程度增加导致湖光岩玛珥湖湖面下降,大量C4草本植物生长在暴露的湖滨岸;17.2～4kaBP时段内δ13CTOC值尽管存在更加频繁的波动,但总体呈现逐渐偏负的趋势,反映了暖湿和冷干气候多次交替但总体上逐渐变暖、变湿的气候环境;4kaBP以来δ13CTOC值存在逐渐偏正的趋势,虽然不排除人类活动的影响,但很可能反映了干旱程度的再次增加。综合分析表明,有效降水量(降水量-蒸发量)是控制湖光岩玛珥湖地区C3/C4植物相对生物量变化的主导因素。湖光岩玛珥湖有机碳同位素的研究结果支持区域气候环境而不是大气CO2浓度变化是末期冰期以来热带低纬度地区C3/C4植被相对生物量变化的主要原因。

中国玛珥湖的时空分布与地质特征

自新生代以来 ,在亚洲东部大陆边缘的裂谷系和青藏高原内部及周边地区 ,火山活动频繁发生 ,形成大量火山和火山岩 ,在一些火山区还发育有大小不等、形态不一的玛珥湖 ,其中有的积水 ,有的干枯 ,它们集中分布于雷琼、东北、青藏高原等地区 ,跨越了热带、亚热带、温带和高寒地带。从中新世的山东山旺盆地 ,早更新世东北龙岗地区的龙湾 ,到雷琼地区中晚更新世的田洋、湖光岩等 ,几乎各个时代、各种类型的玛珥和玛珥湖都有 ,玛珥湖中的沉积物从几十米到一二百米厚度不等 ,记录了不同地区、不同时段气候环境演变的历史 ,对全球变化研究有着重要意义。

末次冰期以来湛江湖光岩玛珥湖孢粉记录及古环境变化

通过对湛江湖光岩玛珥湖钻孔孢粉记录的研究认为 ,末次冰期以来 ,该区植被类型从早期的南亚热带季风常绿阔叶林依次演替为 ,中亚热带常绿、落叶阔叶林→南亚热带季风常绿阔叶林→中亚热带常绿 落叶阔叶 针叶混交林 (湖边草地 )→热带季雨林→半常绿季雨林。气候最寒冷的时期温度比目前至少降低了 4— 6°C以上。全新世早期相对干旱。

18.5kaB.P.以来东北四海龙湾玛珥湖全岩有机碳同位素记录及其古气候环境意义

结合含水量、TOC含量和TOC/TN比值变化曲线,18·5kaB·P·以来的四海龙湾玛珥湖沉积物全岩有机碳同位素组成(δ13CTOC)记录可划分为3个阶段:1)末次冰期晚期(18·5~14·7kaB·P·),δ13CTOC值偏正,变化范围为-29·50‰^-26·18‰,平均值约为-28·10‰;2)末次冰消期(14·7~11·7kaB·P·),δ13CTOC值显著偏负,变化范围为-33·92‰^-28·40‰,平均值约为-31·75‰,在δ13CTOC值变化曲线上表现为一个低谷,但在类似YoungerDryas的冷干事件期间(12·7~11·7kaB·P·),δ13CTOC值再次显著偏正,最高可达-28·4‰;3)全新世以来(11·7kaB·P.至今),δ13CTOC值变化幅度不大(-30·85‰^-27·37‰),基本上都在平均值-29·1‰左右。研究表明,大气CO2浓度变化是影响18·5kaB·P·以来四海龙湾玛珥湖δ13CTOC值变化的主导因素。

湖光岩玛珥湖的浮游植物

本文对广东省湛江市湖光岩玛珥湖的浮游植物进行了周年的调查和分析,结果共检出浮游植物99属260种(包括变种和变型):春季119种,夏季121种,秋季150种,冬季122种,其中蓝藻门20属43种,占种类数的16.5%;硅藻门20属79种,占种类数的30.4%;绿藻门49属117种,占种类数的45%;甲藻门2属8种,占种类数的3.1%;裸藻门2属2种,占种类数的0.8%;金藻门2属6种,占种类数的2.3%;黄藻门3属4种,占种类数的1.5%;红藻门1属1种,占种类数的0.4%。全年广布种有40种:蓝藻门15种,硅藻门6种,绿藻门14种,甲藻门3种,金藻门和黄藻门各1种。各两季节间的共有种数在57—78种,Jaccard种类相似性指数范围在0.28—0.42。优势种(Y>0.02)共有29种:春季8种、夏季16种、秋季13种、冬季11种,分别隶属于蓝藻门13种,绿藻门8种,硅藻门8种,其中Chroococcus m inor、M icrocystis flos-aquae、Pleurocapsa fuliginosa、Chlorella vulgaris为全年广布优势种。在春、夏、秋3季以蓝藻的优势种类居多,而在冬季则以硅藻的优势种类居多。细胞丰度在6.3×104—56.1×104ind/L,春季最高,冬季次之,夏季最低。多样性指数平均为4.53,均匀度平均为0.65,其排序都为冬季>秋季>夏季>春季,物种非常丰富。浮游植物群落中存在着os、βm、αm的优势种群,其群落结构具有典型的亚热带特征。从浮游植物吸收N、P的配比分析,P成为全年唯一的营养限制因子,但从N、P的绝对值看,N和P都是全年的营养限制因子。综合分析结果,湖光岩玛珥湖水质营养类型属于亚热带贫营养型。