Comparisons between marine productivity and terrestrial input records in the Gulf of California over the last 28 ka     

Elsa Arellano-Torres  Astrid J. Mora-Rivera  Paola Vázquez-Romero  Enrique H. Nava-Sánchez  Juan José Kasper-Zubillaga  M. Socorro Lozano-García 《第四纪科学杂志》2020,35(3):479-491

We study the marine and terrestrial contributions in the Gulf of California (GC) to understand the relationship between continental climate and oceanographic variability over the last 28 ka. In Core AII125-8-JPC-20, we examine aeolian and riverine inputs as nutrients for biological productivity. We use biogenic silica (%opal), total organic carbon (%TOC) and calcium carbonate (%CaCO₃) as proxies for primary productivity, and lithic fraction distributions as proxies for terrigenous transport. At the core site, biogenic and lithic components are in phase at millennial-scale in response to regional climate conditions. During the Late Pleistocene, the GC shelf area was above sea level and the western margin showed transient episodes of increased fluvial inputs. Episodic increases in %opal and reduced %TOC suggest upwelling events but ineffective C-export to the sediment. During stadial events (Heinrich 2, Heinrich 1, Younger Dryas), regional declines in %opal, but increases in %CaCO₃ and TOC, suggest efficient C-export by carbonate organisms. During most of the Holocene, dust inputs are higher. Episodic increases in %TOC suggest higher C-accumulation, although this is not controlled by siliceous or calcareous organisms. In the GC, besides upwelling and current advection, nutrient inputs driven by terrestrial climate have an impact on the biological C-pump. © 2020 John Wiley & Sons, Ltd.  相似文献   

风沙活动强度的常用判断指标及其应用评述   总被引：5，自引：3，他引：2  

李晋昌  苏志珠  胡光印 《中国沙漠》2010,30(4):788-795

风沙活动是风力作用下地表物质被吹蚀、搬运和再沉积的过程, 其强度主要决定于风力和下垫面状况两个因素。对风沙活动强度的判断在防沙和治沙研究中长期应用,近年来也成为全球变化研究中经常涉及到的指标之一,尤其是对气候变化和干旱化、沙漠化等研究。列举了国内外常见的18种风沙活动强度的判断指标,对各自的原理、应用方法和适用条件进行了详细的描述和分析,并认为沙漠化面积和湖泊沉积记录可能并不适合作为判断指标,并且各指标之间缺乏可比性,重新建立一种可适用于不同时空尺度的判断指标应是今后研究的重点,这将对反映风沙活动的演变历史、预测未来的发展趋势及指示中国黄土高原的形成环境均有极为重要的意义。  相似文献   

Aeolian dust transportation and deposition by near-surface winds in arid and semiarid China     

JinChang Li  ZhiBao Dong  GuangQiang Qian  WanYin Luo 《寒旱区科学》2010,2(2):0137-0142

Dustfall collections were carried out in April and May 2001 and in March 2002 at six sites in northern China.Our results showed that the total deposition of dust fractions 250 μm in diameter and the deposition of Fe both decreased exponentially with increasing distances from the source areas,and that the half-attenuation distance (HAD) for dust deposition was about 229 km in this re-gion.The HAD was closely related to the grain-size distribution of the dust,and the 15 to 20 μm fractions had the longest HAD.However,the fractions 15 μm in diameter can be easily adsorbed to coarse particles and deposited after only short distances,and the HAD for the fractions 15 to 100 μm in diameter showed a power relationship with the grain-size distribution.The HAD for Fe deposition was 233 km,which was a little longer than that of total dust deposition,which suggests that the Fe content is higher in fine particles than in coarse particles,as previous studies have suggested.In addition,our analysis showed that under the control of current climatic conditions,the coarse fractions in dust derived from northwestern China cannot be transported over long distances,instead,it is transported primarily by near-surface winds (3 km above the ground).The Fe in aeolian dust generated from arid and semiarid regions of China and deposited in the North Pacific region is usually transported by the upper westerlies.  相似文献   

2007年春季沙尘暴对辽宁中部城市群空气质量的影响   总被引：3，自引：1，他引：2  

周德平  王扬锋  洪也  刘宁微 《中国沙漠》2010,30(4):976-982

根据大气降尘量和可吸入颗粒物PM10 、PM2.5、 PM1的观测资料,分析了2007年春季发生于我国北方的两次沙尘暴天气过程对辽宁中部城市群空气质量的影响。结果显示,沙尘天气使各城市大气降尘量与可吸入颗粒物PM10和PM2.5的质量浓度明显增高,空气质量明显下降。在3月31日和5月7日的两次沙尘暴过程中,城市群的大气降尘量比当月日平均值分别增加了1.5倍和2.5倍,各城市PM10的日均质量浓度比沙尘出现前一日分别增加了0.2～2.6倍和1.5～3.8倍。3月31日除铁岭和鞍山空气质量状况为良外,均达到轻微污染程度;5月7日鞍山达严重污染程度;沈阳、辽阳、本溪、铁岭和抚顺的空气质量均为中度污染或中度重污染。沙尘暴期间1.0～10.0 μm的粗粒子为影响辽宁中部城市空气质量的主要成分,其小时平均质量浓度最大时是沙尘出现前的10～30倍。  相似文献   

Spatial trends of dustfall over northern China in the spring and their influencing factors     

JinChang Li  ZhiBao Dong  GuangQiang Qian  WanYin Luo 《寒旱区科学》2010,2(6):0529-0537

The spatial trends of dustfall of different sizes over northern China during April and May 2001,and March 2002,and their influencing factors,were analyzed.We divided the dustfall into seven grades based on particle size.Total dustfall and dustfall for each grade were highest in desert regions then in regions undergoing desertification,and the total dustfall,dustfall 100 μm and dustfall 250 μm were higher in western agricultural regions closer to desert areas than in eastern agricultural regions.The spatial trends in dustfall 300 μm in diameter were most strongly correlated with dust events,and the content of coarse particles increased with increasing severity of dust events.Because the spatial trend for dust events appears to be controlled by geomorphic conditions,vegetation coverage,soil moisture,and the distance from dust source,dustfall 300 μm in diameter appears to have the same controlling factors as dust events,but the control decreases with increasing particle size.Wind,the driving force for dust emissions,also influenced the spatial trends in dustfall 200 μm in diameter,and especially for dustfall 50 to 100 μm in diameter.Although dustfall 300 μm in diameter and precipitation were not strongly spatially correlated,there is some evidence that high precipitation decreased deposition by restraining blowing sand.The coarser the dustfall,the weaker the correlation with wind speed;however,transport of larger particles still occurs,and further research will be required to test the possibility that this dust is entrained mainly by the small-scale dust devils that are commonly observed in the study area.  相似文献   

淄博市大气降尘矿物组合特征及其环境意义     

王永在  姚德  李功胜  王志国 《吉林大学学报(地球科学版)》2010,40(6):1429-1434

用多晶X-射线衍射法对淄博市中心城区逐月采集的大气降尘矿物组成及其含量进行了分析。研究结果表明:淄博市大气降尘的矿物组合比较稳定,降尘中以源于自然成因的石英、长石和粘土质矿物为主,质量分数变化范围为59.1%～95.1%。降尘中的石膏和方解石与大气化学反应有关,其中石膏质量分数为36.3%～1.0%,反映了大气SO₂污染具有明显的时间性特征。降尘中的赤铁矿源于高温工业活动,含量变化幅度最小。气象因素可能是导致降尘中石膏含量变化的主要原因,降尘中石膏含量的变化是大气酸污染程度的重要矿物指示剂。  相似文献   

黄土高原25万年以来粉尘堆积与侵蚀的定量估算   总被引：4，自引：0，他引：4  

李郎平  鹿化煜 《地理学报》2010,65(1):37-52

黄土高原广泛分布第四纪以来的粉尘堆积,是古气候变化的良好记录。但是,将黄土高原视为一个整体、从地质历史的角度来定量分析粉尘堆积-侵蚀的动态过程及其驱动机制的研究较少。本文利用遥感分析和地统计学中的克里格空间估值法,根据对具有代表性的84个实测黄土-古土壤剖面的分析,计算出黄土高原250ka以来各冰期和间冰期的粉尘堆积量和平均堆积速率,为认识区域粉尘沉降与轨道尺度气候变化的关系提供了新证据:间冰期气候偏暖湿,粉尘堆积较慢;冰期气候偏干冷,粉尘堆积加快。结合黄土高原现代降尘观测数据,进一步估算出黄土高原250ka以来各冰期和间冰期的面状侵蚀速率。初步结果发现,自然背景下黄土高原就存在较强的侵蚀作用;冰期的面状侵蚀速率略强于间冰期。  相似文献   

北京城市广场及校园表土(灰尘)中重金属水平与健康风险   总被引：24，自引：4，他引：20  

李晓燕  陈同斌  雷梅  谢云峰  周广东  宋波 《地理研究》2010,29(6):989-996

通过对北京市城市广场和学校表层土壤与相应的地表灰尘中重金属含量调查,探讨土壤与灰尘之间元素分布的差异及来源,评估青少年在校期间通过灰尘摄入重金属的健康风险。研究表明:城市广场和校园土壤中Cu、Pb和Zn、灰尘中As、Cu、Pb、Zn和Cd显著高于北京市土壤重金属背景值,土壤(灰尘)中As、Ni、Cu、Pb、Zn和Cd超过背景值的样本比率分别为67%(27%)、13%(63%)、83%(100%)、73%(100%)、83%(100%)和53%(100%)。土壤中Cu、Pb和Zn存在一定积累,灰尘中Cd、Cu、Pb和Zn积累较重。灰尘中Cu、Pb和Zn显著高于土壤。校园土壤中Ni显著高于城市广场土壤,其他元素两者之间差异不大;校园灰尘中Ni、Pb和Zn显著高于城市广场。中学生通过校园灰尘摄入没有导致明显的健康风险。  相似文献   

沙尘气溶胶的光学特性及辐射强迫效应   总被引：5，自引：4，他引：1  

郝丽  杨文  吴统文  赵剑琦  石广玉 《中国沙漠》2010,30(6):1477-1482

在采用OPAC折射指数资料库和对数分布的基础上,利用MIE散射理论和一个简单的概念模型研究了沙尘气溶胶的辐射特性及全球直接辐射强迫值,分析了单相系沙尘气溶胶的消光、散射、吸收效率因子与粒径的关系,讨论了多相系沙尘气溶胶的光学参数随波长的变化特征。结果表明,消光效率因子和散射效率因子随粒径增大而衰减振荡,随波长增大振荡特性逐渐消失。消光系数对众数半径的变化很敏感,单次散射反照率和非对称因子对众数半径的变化不敏感。沙尘气溶胶的直接辐射强迫受气溶胶的单次散射反照率影响很大,随着众数半径的增大,沙尘气溶胶的负的直接辐射强迫值在减小,正辐射强迫值在增大。  相似文献   

中国北方不同区域典型站点降尘特性的对比   总被引：1，自引：0，他引：1  

李晋昌  董治宝  钱广强  罗万银 《中国沙漠》2010,30(6):1269-1277

2001年4月—2002年3月,选择位于中国北方沙尘源区的沙坡头和奈曼及位于黄土高原的古县进行了一年的大气降尘监测,并对不同季节降尘量、降尘粒度分布和元素组成进行了系统分析。不同站点大气降尘的这些特性的相同点可能反映了中国北方大气降尘的共性,不同点则反映了沙尘源区与沉降区大气降尘的差异。相同点主要表现为:降尘均主要源于地表沙尘释放,且以地方性颗粒物为主;季节分布均为春季最大、夏季次之、秋季最小;冬半年降尘中远源粉尘含量均大于夏半年,且降尘均主要表现为常态存在的非尘暴降尘。差异性主要表现为:奈曼和古县降尘中人为影响较大;古县降尘受远源影响最大,奈曼次之,沙坡头最小;降尘中粗颗粒物含量以沙坡头最高,古县略低于奈曼;粒度特征的季节变化受风力、源区距离、搬运方式和源区物质组成等因素的共同影响,且具有明显的区域差异。此外,降尘粒度大小与风力并不一定呈正相关,因此,利用黄土粒度来指示冬季风强度时必须结合其他代用指标才能做出较正确的判断。  相似文献