Response of the barrier island coastal region of southwestern Nigeria to climate and non-climate forcing     

IB Danladi  M Gül  E Ateş 《African Journal of Marine Science》2020,42(1):43-51

Despite threats emanating from the influence of climate and non-climate forcing on the barrier island coastal region of southwestern Nigeria, the extent of the coastal erosion is poorly understood. We report evidence of coastal erosion and sediment accumulation in the region over a 34-year period (1973–2017), using Landsat imagery at intervals of approximately six years. Landsat image corrections and various water-extraction algorithms were used to systematically delineate coastal erosion and accumulation in the area. The region was subdivided into western and eastern subregions separated by Lagos Harbour. In the west, erosion took place during the periods 1973–1979, 1979–1984, 1990–1999 and 2005–2011, whereas in the east, erosion occurred during 1973–1979, 1990–1999 and 1999–2005. Coastal sediment accumulation occurred in the east during 1979–1984, 1984–1990, 2005–2011 and 2011–2017, whereas gains in the west occurred during 1984–1990, 1999–2005 and 2011–2017. The study revealed substantial net erosion of 1 228.1 ha in the region as a whole, over the full period. Sediment accumulation accompanying the coastal erosion appears to be linked to longshore drift. Erosion between 1973 and 2011 was probably attributable to climate change (storms and tidal conditions), longshore drift, the inflow and outflow of water at Lagos Harbour, coastal morphology and, possibly, human impacts. However, the coastal changes between 2011 and 2017 were more obviously associated with human activities, such as development of the Eko Atlantic construction project. Coastal surveillance, together with the use of environmentally sensitive protective measures, could possibly help to reduce coastal erosion in the region. Careful coastal management practices, including artificial nourishing and the installation of resilient structures (e.g. seawalls), should be undertaken to protect human settlements that are already at risk from sea-level rise.  相似文献   

Trichodesmium erythraeum (Ehrenberg) bloom along the southwest coast of India (Arabian Sea) and its impact on trace metal concentrations in seawater     

Anoop A. Krishnan  P.K. Krishnakumar  M. Rajagopalan 《Estuarine, Coastal and Shelf Science》2007,71(3-4):641-646

The incidence of a large scale Trichodesmium erythraeum bloom along the southwest coast of India (Arabian Sea) observed in May 2005 is reported. Around 4802 filaments of T. erythraeum ml⁻¹ seawater was observed and a colony consisted of 3.6 × 10⁵ cells. The bloom was predominant off Suratkal (12° 59′N and 74° 31′E) with a depth of about 47 m, covering an area of 7 km in length and 2 km width. The concentrations of Zinc, Cadmium, Lead, Copper, Nickel and Cobalt were determined in samples collected from the bloom and non-bloom sites using stripping voltammetry. The observed hydrographical and meteorological parameters were found to be favorable for the bloom. The concentrations of Zinc, Cadmium and Nickel were found to be higher at bloom stations, while the concentrations of Lead, Copper and Cobalt were found to be very low at bloom stations. Elevated concentrations of Cadmium and Cobalt were observed at Valappad mainly due to the decomposition of detrital material produced in the bloom. Statistically significant differences (P > 0.01) in metal concentrations between the bloom and non-bloom stations were not observed except for Copper. Metals such as Lead, Copper and Cobalt were removed from the seawater at all places where bloom was observed. Cadmium was found to be slowly released during the decaying process of the bloom.  相似文献   

黄河三角洲造陆速率对夏季风强度变化和人类活动的响应     

许炯心 《海洋学报》2007,29(5):88-94

以夏季风强度指数和年均气温作为反映气候变化的指数,以人类净引水量和流域水土保持面积作为反映人类活动变化的指标,并以黄河流域为例,研究了三角洲造陆对气候变化和人类活动的响应.研究表明,夏季风强度指数的变化可分为三个阶段:(1)在1951~1963年夏季风强度指数呈持续增强的变化趋势;(2)在1963~1965年夏季风强度指数呈突变式减弱;(3)在1966~2000年夏季风强度指数保持在较低的水平上,且呈缓慢减弱的趋势.年降水量变化与夏季风强度指数有同步关系.从1950到1970年的年均温度在波动中略呈降低趋势,然而从1970年开始年均温度在波动中具有持续上升的趋势.气候变化会导致入海泥沙通量的变化,并可能进一步导致三角洲造陆速率的变化.黄河三角洲造陆速率、入海泥沙通量在1952~1964年均呈增大的趋势,1964年后则呈减小的趋势,在总体上与夏季风强度指数的变化趋势相同.除了气候变化以外,流域水土保持和引水对三角洲造陆也有影响.多元回归分析表明,三角洲造陆速率随夏季风强度指数的减弱而减小,随年气温的升高而减小,随梯田林草面积的增加而减小,随年净引水量的增加而减小,同时还表明,夏季风强度指数、年均气温、水土保持措施面积和人类净引水量对三角洲造陆速率变化的贡献率分别为34.94%,3.80%,53.82%和7.44%.表示气候变化的两个变量的贡献率之和为38.7%,说明气候变化对黄河三角洲造陆过程的影响是不容忽视的.  相似文献   

利用臭氧氧化发光光谱特征检测水质污染     

侯广利  刘岩  蒋慧略  高杨  徐珊珊  尤小华 《海洋技术学报》2006,25(2):117-120

利用不同的污染物质在被臭氧氧化时发光特性不同的原理检测水质污染。检测出来的发光光谱与不同污染源的特征光谱进行对比,辅助发光时序等特征,检测几种污染物的含量和确定污染源。对涉及的有关技术问题进行了探讨。  相似文献   

罗氏沼虾育苗用水中Mg²⁺与Ca²⁺含量及Mg²⁺/Ca²⁺对出苗率的影响   总被引：13，自引：0，他引：13  

臧维玲  戴习林  张建达  朱正国 《海洋与湖沼》1995,26(5):552-557

１９９１年３－６月和１９９２年３－６月在南汇县东海水产养殖公司对罗氏沼虾育苗用水调配原则与不同基础水的调配方法进行试验研究。结果表明，育苗用水中Ｍｇ＾２＋与Ｃａ＾２＋含量及Ｍｇ＾２＋／Ｃａ＾２＋必须达到一定的范围，这是调配的基本原则。以鱼塘水作基础水时，需添加６种化学药品，其中Ｍｇ＾２＋与Ｃａ＾２＋含量可适范围分别为３００．０－４４０．０ｍｇ／Ｌ与１７０．０－２４４．０ｍｇ／Ｌ，Ｍｇ＾２＋／Ｃａ＾  相似文献   

Action of Cnoidal Waves on Vertical Walls     

Qiu Dahong  Zang Jun  Jia Ying Academician of the Chinese Academy of Sciences  Professor  the State Key Laboratory of Coastal  Offshore Engineering 《中国海洋工程》1996,(2)

Based on the 2nd order cnoidal wave theory, the characters of shallow water standing waves and their action on vertical walls are studied in this paper. The theoretical expressions of the wave surface elevation in front of and the wave pressure on the vertical wall are obtained. In order to verify the theoretical results, model tests were made in the State Key Laboratory of Coastal and Offshore Engineering at DUT. For the wave surface elevation in front of the wall and the wave forces on the wall at the moment when the wave surface at the wall surface goes down to the bottom of the wave trough, the calculated results coincide quite well with the experimental results. For the wave forces on the wall at the moment when the wave surface at the wall surface goes up to the top of the wave crest, the theoretical expressions are modified by the experimental results. For the convenience of practical use, calculations are made for the wave conditions which usually occur in enginering practice by use of the inves  相似文献   

山东蓬莱西庄附近海域波浪与海岸侵蚀     

陈雪英  胡泽建 《海洋科学进展》1992,(2)

本文探讨西庄附近海域的波浪状况,分析由于人工挖沙影响,使得登州浅滩的防护作用发生变化,导致近岸波浪作用增强,造成海岸侵蚀.最后讨论设计波要素的确定,为防浪护坡工程提供必要的设计依据.  相似文献   

长江三角洲晚更新世末期古土壤与古环境   总被引：4，自引：0，他引：4  

刘宝柱  李从先  业治铮 《中国海洋大学学报(自然科学版)》1997,(3)

长江三角洲地区第一暗绿色硬粘土层是上海地区主要建筑持力层之一，也是划分全新统与更新统的标志层，前人已做过大量研究，但尚缺乏古土壤方面的系统研究工作。本文首次从古土壤学的角度系统研究了该层的古土壤特征，通过粒度分析发现有粘粒的生成，微形态研究发现有粘粒及铁锰、碳酸盐等化学组分的迁移与淀积，化学全量分析得出该层的硅铝率为２．８０～３．３７，说明该层已发生较强的成土作用，可以确认该层为古土壤层，并进一步把该层划分为４个Ｂ层、３个Ａ层，亦即该层为复合古土壤层。根据该层的成土特征，将其命名为古潮土  相似文献   

胶州湾海域水质预测   总被引：3，自引：0，他引：3  

孙英兰  孙长青  王丽霞  徐鸿楷 《中国海洋大学学报(自然科学版)》1994,(Z1)

在已建潮流模型的基础上,用ADI法建立了胶州湾扩大域变动边界的平流—扩散输运模型,以COD为指示因子,预测了胶州湾海域1995年、2000年的水质、青岛环海公路海上段、沧口区北半部污水截流、北水南调、集中排放以及胶州湾西部经济开发对海域水质的影响等。为青岛市环保部门制定环保规划提供决策依据。  相似文献   

季节内SST和混合层深度变化的模式研究     

孙即霖  吴德星  李国璋 《中国海洋大学学报(自然科学版)》1993,(Z2)

用Niiler—Kraus类型的混合层积分模式,对TOGA—COARE强化观测期间由《实验3号》科学考察船观测资料得到的混合层深度和SST在季节内时间尺度的变化进行了模式研究。指出:1.混合层耗散参数与较长时间尺度过程风应力的变化存在着比较好的对应关系;2.模式可以较好的对风场和热通量场在季节内时间尺度的变化作出响应,模拟出季节内时间尺度SST的变化;3.Niiler,-Kraus模式在考虑耗散作用后,可用于海洋季节内时间尺度变化的模式研究。  相似文献