The late Quaternary development of three ancient tarns on southwestern Cumberland Peninsula, Baffin Island, Arctic Canada: paleolimnological evidence from diatoms and sediment chemistry

Sediment diatom and chemical analyses of cores from three poorly buffered extra-glacial lakes on the northeastern margin of the Canadian Shield (Cumberland Peninsula, Baffin Island) record interactions between aquatic and terrestrial spheres that were influenced by late Quaternary climatic conditions. Although differences exist between each of the lakes, notably with regards to the intensity of pre-Holocene catchment erosion and the timing of the onset of organic sedimentation, an underlying pattern of lake ontogeny, common to all three lakes, is identified. Although intensified watershed erosion characterized the Late Wisconsinan and Neoglacial cold periods, the lakes nonetheless remained viable ecosystems at these times. Sudden catchment stabilization during the late-glacial to earliest Holocene is associated with incipient organic sedimentation. Lake-water pH increased at this time, likely in response both longer base cation residence times as lake flushing rates decreased, and enhanced alkalinity production from sediment biogeochemical reactions. Subsequently, as the catchments remained stable during the productive early Holocene (c.9–7 ka BP), then gradually received a renewed increase of minerogenic sedimentation, the breakdown of sources of lake alkalinity resulted in natural acidification. Burial of cation-rich mineral sediments and the loss of permanent sedimentary sinks for the products of microbial reduction likely impeded within-lake alkalinity production, and catchment-derived base cations appeared ineffective in curtailing pH declines. The general nature of the Holocene development of these lakes is similar to that observed elsewhere on crystalline terrains, following deglaciation. Our data therefore suggest that catchment glaciation is not a necessary precursor for models of lake development characterized by initial base cation enrichment and subsequent gradual acidification.     

Topographic changes of a supply‐limited inland parabolic sand dune during the incipient phase of stabilization

Topographic surveys on an inland parabolic sand dune over a six‐year period provide insight into the effects of diminishing local sand supply on dune stabilization. During the interval (2003–2009) sparse vegetation cover (Psoralea lanceolata) increased despite drier than normal moisture conditions and steady wind power during the growing season. Whereas these climatic conditions are typically ascribed to sustaining or increasing dune activity, here they coincide with stabilization. Through the use of geographic information system (GIS) analysis of volumetric changes it is shown that the increase of P. lanceolata can be attributed to the reduction of local sand supply from two blowouts along the arms of the parabolic dune during the six‐year period. These results show that climate is not the only control on dune activity in vegetated inland dunefields. Copyright © 2010 John Wiley & Sons, Ltd.     

南海长链烯酮化合物的检测及U37^k值的应用

首次系统地在南海大面积站位中检测出长链烯酮化合物。通过长链烯酮指标Ｕ３７ｋ与实测表层海水温度（ＳＳＴ）的对比研究,发现海洋沉积物样品在室温下长期（１７ａ）密封保存,长链烯酮指标Ｕ３７ｋ值无明显变化。Ｕ３７ｋ值在南海海区指示的表层海水温度与季节有关,主要反映秋、冬两季,即１０月至次年３月间的ＳＳＴ。     

Plume and bloom: effect of the Mississippi River diversion on the water quality of Lake Pontchartrain

The opening of the Bonnet Carré spillway to prevent flood threat to New Orleans in April 2008 created a sediment plume in the Lake Pontchartrain. The nutrient rich plume triggered a massive algal bloom in the lake. In this article, we have quantified the spatio-temporal distribution of the plume (suspended solids) and the bloom (chlorophyll-a (chl-a)) in the lake using remotely-sensed data. We processed the Moderate-resolution Imaging Spectroradiometer satellite data for mapping the total suspended solids (TSS) and chl-a concentrations. An existing algorithm was used for estimating TSS whereas a novel slope model was developed to predict the per-pixel chl-a concentration. Both algorithms were successful in capturing the spatio-temporal trend of TSS and chl-a concentrations, respectively. Algal growth was found to be inversely related to TSS concentrations and a time lag of ～45 days existed between the spillway opening and the appearance of the first algal bloom at an observation location.     

低场核磁共振定量测定松散沉积物中含水量的方法

核磁共振通过测定体系中氢质子弛豫的T2谱来确定液态水的含量。采用低场核磁共振技术定量测定松散沉积物体系中的含水量,探讨了沉积物粒径、黏土矿物种类与含量、孔隙水盐度、温度及气体压力等因素对测试结果的影响。由于不同介质体系中孔隙水表面弛豫机制不同,导致低场核磁测定松散沉积物中的含水量偏小。引入校正系数Cm对水量测试值进行了修正,结果表明：沉积物及孔隙水介质本身特性对水量测试结果几乎无影响,相对误差<0.5%,测试精密度<0.20%;温度变化对测试结果影响较大且呈负相关,温度从25 ℃降至1.7 ℃,水量测试值增加了10.71%;压力变化对测试结果的影响与充注气体是否含氢密切相关,不含氢气体的压力变化对测试结果没有影响,而对于含氢气体如甲烷,水量测试结果随压力变化线性增加,甲烷增加到5.05 MPa时,测试结果增加了12.15%。因此,在采用该法测量甲烷水合物生成分解过程中沉积物孔隙水的变化时,必须考虑体系的温度、压力对测试结果的影响,恒温恒压条件下监测的含水量变化能够准确指示甲烷水合物生成分解的微观过程,可望在海洋天然气水合物生成分解微观动力学研究方面得到广泛应用。     

粉砂质海岸大风天泥沙运动研究

根据黄河三角洲五号桩海域6级大风前后现场悬沙、沉积物和实测水流资料,研究了淤泥质粉砂海岸大风过程后泥沙分布特征和运动规律。发现大风天气海底泥沙对波浪作用反应灵敏,悬沙和底沙分布规律与波浪作用吻合,为波浪作用下海底泥沙运动的理论研究以及海区工程开发提供了科学依据。     

电感耦合等离子体质谱法(ICP-MS)测定水系沉积物中的铌钽锆铪

建立电感耦合等离子体质谱法(ICP-MS)测定水系沉积物中铌、钽、锆、铪四种元素的分析方法。将样品与氢氧化钠、过氧化钠混合物放入高温炉中,熔融分解完全,用热水提取,过滤后弃去滤液,将滤纸及沉淀用酒石酸-盐酸溶液溶解,稀释至刻度测定。方法检出限(3s)为:LD(Nb)=0.08μg/g,LD(Ta)=0.04μg/g,LD(Zr)=0.5μg/g,LD(Hf)=0.04μg/g,精密度(RSD%,n=6)为:0.84%~4.21%。该测定方法具有灵敏度高、精密度好、分析速度快、线性范围宽、操作性强等优势。采用该方法对国家一级标准物质进行测定表明,其结果与标准值吻合。此方法已在实际地质调查样品分析中得到应用。     

南麂列岛潮间带环境本底调查

本文系根据１９９２年８月和１９９３年２月（夏、冬两季）对南麂列岛潮间带的环境本底调查以及对水质、底质、生物样监测结果的资料整理而成。调查结果表明，潮间带水质、底质除个别断面外，均处于良好状态。生物体重金属残留量全部低于全国海岸带调查时统一的标准，生态环境条件较好。     

南海南部大陆架的残留沉积

研究了南海南部大陆架的残留沉积物的粒度、石英砂表面结构特征、生物分布等，并指出残留沉积普遍遭受改造。按其早期的形成环境差异和改造作用不同，划分出加里曼丹－巴拉望残留沉积区和亚南巴斯－纳土纳残留沉积区。     

南水北调对长江口粗颗粒悬沙来量的影响

探索了长江南水北调占总径流量10%情况下对长江粗颗粒悬沙(≥0.05mm)入海数量变化的可能影响。研究表明:南水北调对入海细颗粒泥沙的影响主要为南沙北调,但数量较小,在1%左右,而对粗颗粒悬沙的影响主要表现在入海流量减少导致的水体挟沙能力的降低。通过建立大通站典型枯水年(1978),平水年(1987)及洪水年(1983)月平均流量与月平均床沙质输沙率相关曲线,估算出各典型年在典型流量23000m3/s,30000m3/s与40000m3/s水平下调水流量3000m3/s时导致的入海床沙质输沙率的变化。结果表明,输沙率的相对变化在-39%至-24%之间,且在较高的流量水平下,输沙率相对变化较小,但绝对变化增大,经大通入海的床沙质数量每年约减少2350～4700万t.