The impact of human activities on the flushing properties of a semi-enclosed lagoon: Xiaohai, Hainan, China

In this study, a Lagrangian particle tracking model driven by hydrodynamic fields was used to investigate the changes of flushing properties in Xiaohai Lagoon resulting from natural evolution and influences of human activities. Comparisons of residence times between 1936 and 2001 indicate that the flushing efficiency of the lagoon has deteriorated greatly during the past seven decades. Over this period, the average residence time of the lagoon has increased from 45 to 71 days, an increase of 59%. The Lagrangian residual velocity has decreased from 1936 to 2001 in the large portions of the lagoon, and the spatial distribution pattern of the residual current has changed significantly. The well-developed horizontal circulations in 1936 disappeared. Instead, the horizontal Lagrangian residual velocity showed uniformly seaward motion with reduced velocity in 2001. Human activities have incurred great impacts on the deterioration of flushing efficiency. The reduction of river inflow imposed the most significant impact, causing an increase of average residence time by 33%. The land reclamation in the lagoon came as the second most significant factor, causing an increase of 15%. Closure of the North Opening had posed minor impact. The model results suggest that restoring the river inflow, as well as the dredging of the tidal channel and the inner lagoon, should be the top proprieties for future water quality management.     

农村电子商务与产品多样化影响因素探究——基于浙江淘宝村的实地调研分析

论文基于浙江省282个淘宝村的实地调研数据,从产品的垂直多样化和水平多样化2个方面衡量淘宝村抓住电子商务机遇并实现路径创造的能力,分析了电子商务对农村产品多样化的提升程度,并通过普通最小二乘法(ordinary least square, OLS)模型、空间计量模型构建淘宝村产品多样化的影响因素模型并分析其作用机制,以期弥补电子商务产业演化方面理论研究和经验分析的不足,同时为乡村经济发展与转型的实践提供建议与参考。研究表明：① 淘宝村产品多样化的提升情况呈现两极分化的趋势,垂直多样化和水平多样化的提升程度大致相同;② 浙江省淘宝村的产品多样化提升程度的空间集聚特征明显,产品垂直多样化提升程度的高值聚集点主要位于临安、湖州、慈溪、余姚等地,产品水平多样化提升程度的高值聚集点则位于杭嘉湖区域以及慈溪、余姚等县市,水平多样化提升程度和垂直多样化提升程度的低值聚集点都主要位于义乌市;③ OLS模型显示产品垂直多样化提升程度与产品深化加工及政策的支持情况呈显著正相关;④ 空间误差模型显示产品水平多样化的提升与机械化操作水平呈显著正相关,但电商协会的建立却逆向促进了产品水平多样化提升程度。     

中国土地利用变化遥感研究的回顾与展望——基于陈述彭学术思想的引领

20世纪80年代以来中国社会经济快速发展带来的工业化、城市化正深刻影响着中国土地利用空间格局并影响到区域和国家生态与环境状况。在陈述彭先生指导下,1992年以来中国科学院建立起了完整的土地利用/覆盖变化遥感监测与数据分析技术路线,以及独特的分类体系和动态区划体系,奠定了中国LUCC信息平台的基础。本文在系统回顾陈述彭学术思想指导中国LUCC研究的基础上,面向国家需求与国际科技前沿梳理了我国LUCC研究的核心科学问题,并总结了中国科学院团队在最近20年LUCC研究取得的成果,包括土地利用/覆盖动态时空表征与分析模型、土地利用/覆盖变化过程及驱动机制、基于大数据和云计算的土地利用/覆盖变化探测方法、城市土地利用变化的区域气候/生态效应、气候变化与土地利用变化对农田生态系统的影响、林业活动的区域气候/生态效应,在此基础上对未来LUCC研究的前景进行了展望。     

基于数学形态学算法的机载LiDAR点云数据快速滤波

机载LiDAR点云数据滤波是LiDAR数据处理领域研究的重点和难点之一.针对LiDAR点云数据量大的特点,以规则格网组织数据,按离散点或格网移动结构窗口,提出基于数学肜念学算法的LiDAR点云数据快速滤波方法,并详细介绍滤波的方法和流程.试验结果表明,该算法计算速度快,滤波效果好.最后选取两组小同区域的点云数据进行实验,并给出滤波前后的数字表面模型和局部断面图.     

赤潮藻类非线性动力学模型的随机分岔

选取典型赤潮藻类的硅藻和甲藻,建立了一个随机非线性动力学模型,运用随机平均法结合现代非线性动力学理论对模型进行了化简,运用拟不可积 Hamilton 系统的相关理论和 Oseledec 乘性遍历定理求解了模型的最大 Lyapunov 指数,得到了模型随机稳定性的条件;利用动态系统不变测度的 Lyapunov 指数分析了模型的随机分岔,得到了系统发生随机D-分岔时参数的取值条件,结果表明,系统在随机因素作用下变得更敏感、更不稳定.     

Spatial distribution and diurnal variation of chemical oxygen demand at the beginning of the rainy season in the Changjiang （Yangtze） River Estuary

A field observation was carried out in the Changjiang （Yangtze） River Estuary from May 19 to 26, 2003. A total of 29 stations, including 2 anchored stations, were occupied through almost the whole salinity gradient. Based on the observation data, biogeochemistry of chemical oxygen demand （COD） was examined. Spatial distribution pattern of COD shows that it decreased downstream. The COD concentration varied generally within a narrow range of 1.24-1.60 mg/L in the zone around the river mouth, beyond which it decreased rapidly to 0.20 mg/L. In the mixed water zone, the fluctuation in COD was smaller at 2 m above the bottom layer than at the surface layer in 48 h. In the seawater zone, the 48-h fluctuation at the surface was the largest, followed by that of 5 m below the surface and 2 m above the bottom layers in a range of from 2.50 to 0.55 mg/L. Freshwater discharge was the dominant source of COD in the estuary. The average COD beyond the river mouth was 2.7 mg/L, which accorded with the Chinese seawater quality Grade I. Relationships between dissolved oxygen and biogeochemical parameters such as suspended particulate matter, dissolved organic matter and chlorophyll-a were also discussed.     

广东沿海牡蛎体Cu含量水平及其时空变化趋势

为了解广东沿海 Cu含量水平的时空变化趋势 ,1989～ 1997年实施“南海贻贝观察”对广东沿海 12个地点进行了连续监测。实测数据和有关历史资料综合分析结果显示 ,广东沿海牡蛎体 Cu含量(湿重 )范围为 2 .70～ 352 mg· kg-1,平均值为 94 .1mg·kg-1,总超标率达 35.1% ;局部海区属重污染水平。牡蛎体 Cu含量的空间分布特点呈珠江口海区 >粤西海区 >粤东海区格局 ;Spearman顺位相关分析结果表明 ,1989～ 1997年间 ,广东沿海牡蛎体 Cu含量年际间无明显的趋势性变化。     

The release behavior of inorganic nitrogen and phosphorus in sediment during disturbance

Sediments and surface water were sampled in a tide flat in the Huiquan Bay, Qingdao, China in January 2004 to simulate the exchange of NH4-N/NO3-N/ PO 43- between sediments and surface water. A working system was designed with which samples were shaken at 60, 120 and 150 revolutions per minute (r/min). Experiment results show that NH4-N concentration in water at shaking rate of 60r/min decreased gradually, while at 120r/min increased gradually. In resuspension, fine-grained sediments contributed most NH4-N to the seawater, followed by medium-grained and coarse-grained sediments. The NO3-N concentration in water had a negative relation with the shaking rate; the medium-grained sediments contributed more NO3-N to seawater than the coarse-and fine-grained sediments. The PO 43- concentration is positively related with the shaking rate, the fine-grained sediments were the main N and P contributor to the seawater, followed by medium-and coarse-grained sediments.     

Three-Dimensional Mineral Potential Mapping for Reducing Multiplicity and Uncertainty: Kaerqueka Polymetallic Deposit,QingHai Province,China

Natural Resources Research - This study focuses on the selection of a method combining simulations of mineralizing processes with three-dimensional (3D) mapping to quantitatively predict locations...     

Effects of the undecomposed layer and semi-decomposed layer of Quercus variabilis litter on the soil erosion process and the eroded sediment particle size distribution

Simulated rainfall experiments were performed on bare, undecomposed litter layer and semi-decomposed litter layer slopes with litter biomasses of 0, 50, 100 and 150 g m⁻², respectively, to evaluate the effect of the undecomposed layer and semi-decomposed layer of Quercus variabilis litter on the soil erosion process and the particle size distribution of eroded sediment. The undecomposed layer and semi-decomposed layer of litter reduced the runoff rate by 10.91–27.04% and 12.91–36.05%, respectively, and the erosion rate by 13.35–40.98% and 17.16–59.46%, respectively. The percentage of smaller particles (clay and fine silt particles) decreased and the percentage of larger particles (coarse silt and sand particles) increased with an increased rainfall duration on all treated slopes, while the extent of the eroded sediment particle content varied among the treated slopes with the rainfall duration, with bare slopes exhibiting the largest variability, followed by undecomposed litter layer slopes and finally semi-decomposed litter layer slopes. The clay and sand particles were transported as aggregates, and fine silt and coarse silt particles were transported as primary particles. Compared with the original soil, sediment eroded from all treated slopes was mainly enriched in smaller particles. Furthermore, the loss of the smaller particles from the undecomposed litter layer slopes was lower than that from the semi-decomposed litter layer slopes, indicating that the undecomposed litter layer alleviated soil coarsening to some extent. The findings from this study improve our understanding of how litter regulates slope erosion and provide a reference for effectively controlling soil erosion.