Detecting,sourcing, and age-dating dredged sediments on the open shelf,southern California,using dead mollusk shells     

Matthew T. Bizjack  Susan M. Kidwell  Ronald G. Velarde  Jill Leonard-Pingel  Adam Tomašových 《Marine pollution bulletin》2017,114(1):448-465

Molluscan shell debris is an under-exploited means of detecting, sourcing, and age-dating dredged sediments in open-shelf settings. Backscatter features on the Southern California shelf are suggestive of dredged sediment hauled from San Diego Bay but deposited significantly inshore of the EPA-designated ocean disposal site. We find that 36% of all identifiable bivalve shells > 2 mm (44% of shells > 4 mm) in sediment samples from this 'short dump' area are from species known to live exclusively in the Bay; such shells are absent at reference sites of comparable water depth, indicating that their presence in the short-dump area signals non-compliant disposal rather than natural offshore transport or sea level rise. These sediments lack the shells of species that invaded California bays in the 1970s, suggesting that disposal preceded federal regulations. This inexpensive, low-tech method, with its protocol for rejecting alternative hypotheses, will be easy to adapt in other settings.  相似文献   

城镇地震防灾与应急处置一体化服务系统研究     

郭红梅  陈维锋  申源  张莹 《震灾防御技术》2017,12(4):924-935

随着城镇化水平的快速提高,处于地震灾害高风险区域的城镇数量也不断增加。在城镇防震减灾工作管理体系中,市县地震部门的防震减灾工作是关键。然而,这些基层部门在推进防震减灾工作中面临着公共服务科技含量不高、工作手段缺乏、基础数据缺乏等难题。本文针对城镇地震防灾与应急处置的关键环节和薄弱部位,研究针对性强、操作简便的城镇地震防灾与应急处置一体化服务系统,为市县地震部门平时的震害防御、防震减灾科普宣传、应急准备以及震时应急响应和震后应急处置提供重要依据、工具和手段,全面提高市县防震减灾能力。从而提高为城镇人民的生命财产安全和经济建设保驾护航的能力,为城镇化建设营造安全的抗震环境。  相似文献   

A groundwater quality survey of an unsewered,semi‐rural area     

L. W. Sinton 《新西兰海洋与淡水研究杂志》2013,47(3-4):317-326

A baseline groundwater quality survey of 120 household wells in an unsewered area at Yaldhurst, near Christchurch, was carried out between September and December, 1976. Ammonia‐N levels were below the detection limit (0.02 g m^‐3) in all samples. Nitrate‐N, conductivity, and chloride levels tended to vary according to well depth and location, being lower in the deeper wells and in wells located in an area of shallow, stony soils. Approximately 33% of the wells contained coliform bacteria, faecal coliform bacteria or faecal streptococci. A subset of 25 wells was sampled fortnightly from January to August 1977. From January to June, mean nitrate‐N and conductivity levels remained stable at approximately 1.5 g m^‐3 and 11.2 mS m^‐1 respectively. An increase in these levels to 3.3 g m^‐3 and 15.8 mS m^‐1 in July‐August corresponded with a rise in the water table. Leaching losses from soils probably accounted for most of the nitrate entering the Yaldhurst aquifers, the contribution by septic tank systems being estimated at 20–30%. No direct evidence of contamination of the wells by septic tank effluent was found, although 23 of the 25 wells exhibited intermittent contamination by indicator bacteria throughout the 8 month sampling programme. Although a localised health hazard may exist, septic tank systems in the area were not considered likely to constitute a health threat to the confined aquifers underlying Christchurch city.  相似文献   

温室性气体地质处置研究进展及其问题   总被引：7，自引：0，他引：7  

强薇  李义连  文冬光  吴登定  许天福 《地质科技情报》2006,25(2):83-88

温室性气体地质处置的机理有3个:①将深部含水地层作为容器封闭CO2;②含水(油)介质,即岩石矿物与CO2发生化学反应而消耗掉CO2,使CO2长期安全保存于地下介质中;③在低渗透含水层中,CO2的运移与滞留时间较长,属于水力学控制CO2的机制.尽管CO2的地质处置存在费用和安全稳定性问题,但国际上已开展的研究表明,地质处置温室性气体是人类积极解决全球环境问题极具前景的方法之一.  相似文献   

高放处置罐铁释放诱发膨润土矿物相变研究进展          下载免费PDF全文

张明  谢敬礼 《岩石矿物学杂志》2021,40(4):778-785

作为高放废物处置罐候选金属材料,低碳钢在处置库服役期间,其腐蚀产物侵入缓冲屏障,导致缓冲材料矿物相变与性能变异,威胁多重屏障体系的长期安全稳定。本文详细综述了国内外处置库深部还原环境所处的弱碱性化学场与中低温度场的变化趋势,认为处置库深部化学-温度还原条件可导致处置罐Fe腐蚀释放Fe~(2+)。在处置库长期运行过程中,蒙脱石与Fe~(2+)接触发生矿物相变,一方面Fe~(2+)置换蒙脱石八面体晶格中的Al~(3+)和Mg~(2+),还原Fe~(3+)或直接占据空位,生成次生矿物;另一方面Fe~(2+)交换蒙脱石层间的Na~+、K~+和Ca~(2+),转化为铁基蒙脱石。矿物相变可诱发缓冲屏障性能变异甚至退化。基于"抗矿物转化"理念,提出了下一阶段缓冲材料矿物相变研究方向,为地下实验室碳素钢选型、缓冲屏障验证试验设计以及屏障体系安全评价提供科学依据。  相似文献   

UASB和ABR在常温下处理生活污水的性能比较研究   总被引：1，自引：0，他引：1  

邓华健 《海洋技术学报》2010,29(1)

沿海城市生活污水的排放,对海洋环境有着重要影响。通过试验,在常温条件下研究了升流式厌氧污泥床反应器(Upflow Anaerobic Sludge Blanket Reactor,简称UASB)与厌氧折流板反应器(Anaerobic Baffled Reactor,简称ABR)处理生活废水的性能。试验结果表明:UASB与ABR对生活污水都有良好的处理效果,在HRT较长时,ABR反应器对COD和SS的去除效果优于UASB反应器;而当HRT缩短,小于12 h,UASB反应器内上升流速增加,改善了对COD的去除效果。ABR和UASB反应器对COD的去除效果都随温度的降低而降低。  相似文献   

海水冲厕技术研究与应用进展   总被引：1，自引：0，他引：1  

寇希元  张雨山  王静 《海岸工程》2009,28(2):83-89

推广海水冲厕是解决沿海城市淡水资源紧缺的有效措施之一。综述了近年来我国海水冲厕技术的研究现状和发展趋势，介绍了海水冲厕在香港的应用现状和在青岛等内地沿海城市的推广应用情况。总结并探讨了海水冲厕推广应用存在的问题及解决这些问题的应对措施。  相似文献