Crystallographic and NMR studies on sterols from green alga Chaetomorpha basiretorsa Setchell

Chemical investigation of the ethanol extract of the marine green alga Chaetomorpha basiretorsa Setchell led to the isolation of a new sterol stigmast-4,28-dien-3α,6β-diol 1 in addition to the five known sterols of β-lawsaritol 2, saringosterol 3, 24-hydroperoxy-24-vinyl - cholesterol 4, β-stigmasterol 5, 29-hydroxystigmasta-5, 24 （28） -dien-3β-ol 6. Compounds were isolated by normal phase silica gel and Sephadex LH - 20 gel colum chromatography, reverse phase HPLC and recrystalization. Their structures were elucidated by spectroscopic methods including MS, IR 1D/2D NMR and X-ray analysis. Cytotoxicity of compounds was screened by using the standard MTF method. All these compounds were isolated from the green alga Chaetomorpha basiretorsa Setchell for the first time and they were inactive （50% inhibitory concentration was greater than 10 μg/cm^3） against KB, Bel -7402, PC - 3M, Ketr 3 and MCF-7 cell lines.     

Spatial and temporal distributions of nitrogen, phosphorus and heavy metals in the intertidal sediment of the Chang jiang River Estuary in China

Spatial and temporal distributions of nutrients (N and P) and heavy metals (Cu, Zn, Pb and Cd) in the intertidal sediments at Dongtan wetland of the Changjiang River (Yangtze River) Estuary were examined by laying one transect running seaward to landward during January, April, June, August and October of 2005. Total nitrogen (TN) and heavy metal concentrations in the intertidal sediment showed an increasing trend from open bare °at to the high marsh, with the maximum concentrations in the high marsh and the minimum values in open bare °at. In contrast, sediment total phosphorus (TP) concentrations changed little among sampling sites. One-way ANOVA found that there were signiˉcantly temporal variations of nutrients and heavy metals concentrations in the intertidal sediment (P <0.05). The concentrations of heavy metals generally showed an increasing trend from January to October. As compared with other large estuaries, heavy metal contamination in the intertidal sediment of the Changjiang River Estuary was relatively low.     

Nutrient composition and distributions in coastal waters impacted by the Changjiang plume

Four cruises were conducted during 2002--2003 in the Changjiang Estuary and adjacent coastal areas. The data presented show a clear coast to open sea gradient in nutrients related to the river inputs. Maximum values of chlorophyll a were typically observed at intermediate salinities at surface water and coincided with non-conservative decreases in nutrients along the salinity gradient, indicating that removal of nutrients was related to phytoplankton uptake. The seasonal variations of nutrient concentrations were just opposite to those of chlorophyll a, indicating that the seasonal variations of nutrients were mainly controlled by phytoplankton uptake, whereas riverine inputs merely weakened or balanced its extent. During the estuarine mixing, phosphate demonstrated some remobilization during all the four cruises; whereas both conservative and non-conservative behaviors for dissolved inorganic nitrogen and silicate were observed in the study area, indicating that both biotic and abiotic events may affect their behaviors during the estuarine mixing. Under the influence of freshwater inputs with high value of ratio of nitrogen to phosphorus, the estuarine and coastal waters impacted by the Changjiang plume were high （ 〉 30） in ratio of nitrogen to phosphorus, but rates of primary production were apparently not constrained by any kind of nutrient elements. However, the low （ 〈 1 ） ratio of silicate to nitrogen in most of the study area might be linked with the rapidly increasing frequency of harmful algal bloom （HAB） incidents in recent years in the coastal waters impacted by the Changjiang plume.     

Nutrient compositions of cultured Skeletonema costatum,Chaetoceros curvisetus,and Thalassiosira nordenskildii

We cultured different-sized fractions of dominant phytoplankton species,Skeletonema costatum,Chaetoceros curvisetus,and Thalassiosira nordenski ldii,collected in different sea areas in various seasons,and measured and compared their C,N,P,Si contents.The N content of these species is similar,while the C,P,and Si contents of S.costatum from eutrophic Changjiang (Yangtze River) estuary are higher than those from Jiaozhou Bay (JZB),particularly the content of Si.The C,N,P,and Si contents of cultured phytoplank...     

“陆态网络”Ⅱ期西部绝对重力测定结果分析

介绍了2013~2014中国大陆构造环境监测网络的基本情况及西部地区绝对重力观测的情况,并对观测结果进行分析。结果表明,成果稳定性良好,89.5%的成果观测精度优于±5.00μGal,能够满足"陆态网络"的技术要求。     

青海循化盆地晚更新世沉积序列与古气候

河流阶地作为河谷中常见地貌, 其堆积物特征对气候变化过程研究具有重要的意义.通过对循化黄河Ⅲ级阶地剖面沉积特征、粒度、磁化率、孢粉以及光释光测年的研究, 初步厘定循化黄河Ⅲ级阶地形成时代为75 ka.循化盆地晚更新世气候演化可以大致划分为6个阶段: 120~114 ka, 气候暖湿; 114~105 ka, 气候较为干冷; 105~98 ka, 气候较暖湿; 98~85 ka, 气候转为温凉; 85~75 ka, 气候暖湿; 75~63 ka, 气候干冷.这6个阶段分别与MIS5e-4段相对应.      

细度和染色杂质对方解石白度的影响

方解石经超细粉碎后通过水力分级分成若干粒级；考察细度对方解石白度的影响；运用高梯度强磁选考察弱磁性染色杂质对方解石白度的影响。     

成熟探区资源潜力评价:以松辽盆地敖南地区为例

勘探实践证明,松辽盆地葡萄花油层成藏条件优越,具有“满凹含油”特征,是开展石油资源精细勘探的主力层系,剩余资源主要分布于成熟探区及其周边。优选位于成熟源岩区内的敖南地区作为典型刻度区,利用岩芯、测井和试油等资料,对葡萄花油层的源岩、储层及油藏进行了详细解剖和刻画,认为该区具备3个有利成藏的地质条件:①有效烃源岩控制油气分布范围;②三角洲前缘亚相薄互层砂体构成油气储集层;③砂体、构造匹配发育大面积岩性油藏。通过综合评价,确定敖南地区含油面积为256.3 km^2,采用容积法和油藏规模序列法估算该区资源量为5057.1×10^4 t,并获取运聚系数、可采系数和资源丰度等可代表资源评价的关键参数。     

近30年青海贵南县土地利用与景观格局变化

基于1977、1999、2007年:三期生长季的Landsat遥感影像,利用RS、GIS及景观生态学方法,对青海省贵南县1977-2007年的土地利用/覆被进行监测.并计算土地利用转移矩阵和景观格局指数;在此基础上对研究区土地利用与景观格局动态变化进行分析.结果表明:1977-2007年间贵南县的土地利用/覆被状况发生了显著变化,草场面积总体呈现退化趋势,其中东南部芒曲镇和森多乡地区的高覆盖度草场持续退化.而木格滩地区的中覆盖度草场则经历了被开垦为耕地后又退耕还草的过程;耕地先增后减,总体呈减少趋势:另外研究区东部和南部山地地带的疏木灌林有所增加,龙羊峡水库的修建淹没了周围一些裸岩和低覆盖度草场,而2000年后政府实施的退耕还草工程也逐步见效.木格滩沙地面积被控制.30年间贵南县景观总体发生破碎化,前期破碎化程度剧烈.优势斑块呈分散趋势,景观异质性上升;后期因退耕还草等保护措施,破碎化程度有所缓和,优势斑块倾向聚集,景观内部聚合度增加.研究区景观变化是自然因素与人为因素共同作用的结果,但近几十年来人口和牲畜数量急剧增加、人类对草场乱采滥伐、不合理发展畜牧业等人为干扰因素还是占主导.