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This paper provides a detailed observation of pond hydrodynamics. Bathymetry and aerator deployment largely control the hydrodynamic regime. Aerators drive pond circulation, which is resisted by bottom and bank friction. Hydrodynamic friction is characterized by sediment grain size. One particular pond is offered as a proxy representative of Australian mariculture ponds in general: Pond X. The pond had been stocked with P. monodon at densities in the range 25–35 m−2 about ten times during the period from 1989 to 1995. Observations were made in the year 1996. The site was on the east coast of Australia at 18° south latitude. The location was sheltered by a mountainous offshore island, such that winds effecting the pond averaged 2.3 m s−1. Water exchange occurred at a rate of about 8.3% of pond capacity per day. Pond X was found to be rectangular, 120 m long and 87 m wide. The banks were found to slope between 1:1.5 and 1:7.6, with an average slope near 1:3. The pond was shallowest in one corner, where depth was 834 mm, and drained diagonally with 1872-mm maximum water depth. Aeration was provided by a total of six 1.5-kW machines, comprised of two of the paddlewheel type and four of the propeller-aspirator type. Each machine was found to deliver 200 N of horizontal thrust into the pond water column. The combined effect of the aerators created a circulation current averaging about 11 cm s−1 around the pond periphery. The central region of the pond was found to have a fluctuating velocity of less than 1 cm s−1. The mass-average size of pond soil and sediment was found to vary from 25 μm in the central region to 250 μm at the banks and where the bottom was swept by paddlewheels.  相似文献
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为了探究长江中游航道整治水下工程区不同恢复阶段沉积物粒度和有机质含量的特征和变化规律,2017年3月、6月、9月分别对长江中游6个恢复时间分别为2、3、4、5、10、15年的航道整治工程区进行了沉积物采集,室内利用Master size2000型激光粒度仪进行分析,并采用MMFr矩值法公式计算粒度特征,灼烧法测量沉积物有机质含量。分析沉积物粒度和有机质含量随恢复时间的变化情况,以及粒度特征参数和有机质含量之间的关系,结果表明,长江中游护岸水下工程区沉积物组成主要以砂为主,粘土、粉砂和砂的平均含量分别是(7.34±4.58)%、(24.26±1.00)%和(68.39±14.06)%。表层沉积物的粒径2.43~6.79 φ,平均值是3.95 φ,中值粒径2.41~6.05 φ,平均值为3.65 φ,整体上粒径偏小。航道整治工程区有机质含量在1.06%~4.82%,平均值为(3.06±1.30)%。3月、6月和9月沉积物的有机质含量分别是(2.75±1.05)%、 (3.65±1.01)% and (2.80±1.46)%。工程恢复越久,小颗粒组分占比越高,平均粒径越大;有机质含量随工程恢复时间的增长而增高,河流的涨枯期对有机质含量的影响不显著;表层沉积物中粘土和粉砂总含量、平均粒径、中值粒径与有机质含量关系极显著。本研究结果既符合河流纵向沉积物粒度分布规律,也反映了时间尺度对沉积物粒度组成和有机质含量的影响。  相似文献
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