Acidification of Lower St. Lawrence Estuary Bottom Waters     

Alfonso Mucci  Michel Starr  Denis Gilbert  Bjorn Sundby 《大气与海洋》2013,51(3):206-218

Accumulation of metabolic CO₂ can acidify marine waters above and beyond the ongoing acidification of the ocean by anthropogenic CO₂. The impact of respiration on carbonate chemistry and pH is most acute in hypoxic and anoxic basins, where metabolic CO₂ accumulates to high concentrations. The bottom waters of the Lower St. Lawrence Estuary (LSLE), where persistently severe hypoxia has developed over the last 80 years, is one such case. We have reconstructed the evolution of pH in the bottom waters from historical and recent data, and from first principles relating the stoichiometry of CO₂ produced to oxygen consumed during microbial degradation of organic matter. Based on the value of the atmospheric partial pressure of CO₂ that best reproduces the preformed dissolved inorganic carbon concentration in the bottom waters, we estimate the average ventilation age of the bottom waters to be 16?±?3 years. The pH of the bottom waters has decreased by 0.2 to 0.3 over the last 75 years, which is four to six times greater than can be attributed to the uptake of anthropogenic CO₂. The pH decrease is accompanied by a decline in the saturation state with respect to both calcite and aragonite. As of 2007, bottom waters in the LSLE are slightly supersaturated with respect to calcite (Ω_c?≈?1.06?±?0.04) but are strongly undersaturated with respect to aragonite (Ω_a?≈?0.67?±?0.03).

  相似文献   

Diurnal variation of nitric oxide emission flux from a mangrove wetland in Zhangjiang River Estuary,China     

Juan Chen  Fei-Hua Wu  Qiang Xiao  Zhang-Hua Yang  Sheng-Kai Huang  Jian Wang  Yu-Guang Wu  Xue-Jun Dong  Zhen-Ming Pei  Hai-Lei Zheng 《Estuarine, Coastal and Shelf Science》2010

The diurnal variation of nitric oxide (NO) emission fluxes from a Kandelia obovata and Avicennia marina mangrove wetland were studied in the Zhangjiang River Estuary Mangrove National Nature Reserve using a dynamic chamber-based technique and a chemiluminescent analyzer. Results from field experiments show that NO emission from K. obovata and A. marina sampling sites reached maximal values of 1.07 ng N m⁻² s⁻¹ and 1.23 ng N m⁻² s⁻¹, respectively after the night tide. Meanwhile NO emission maintained at a steady lower level in daytime for both wetland sites. In laboratory experiments, NO emission from the mangrove wetland soil samples treated with simulated tides in the darkness exhibited higher values than those in the light, therefore it seems that tides and darkness could increase NO emission from mangrove wetlands, while intensive light, high temperature, and dryness in the daytime decreased NO emission. Compared with K. obovata soil samples, the diurnal average NO emission rate of the A. marina site was significantly higher, which was closely related to relatively higher diurnal average CO₂ emission rate, soil available nitrogen content and soil net nitrification rate of the A. marina site. Moreover, soil samples of the A. marina site were more responsive to simulated tides and the addition of nitrogen than those of the K. obovata site.  相似文献   

石油污染对黄河口沉积物工程性质的影响     

王林昌  袁守启  邢可军 《中国海洋大学学报(自然科学版)》2010,40(1)

对黄河口胜利油田某油井附近沉积物进行石油污染状况调查研究,采用坑探试验现场调查污染范围,发现油井沉积物在一定范围内存在石油污染,污染多在0.2～1.5 m深度内,水平距离在140～440 m之间.原位测试污染沉积物强度,取样进行室内石油浓度和沉积物物理力学指标测试.石油污染沉积物物理力学性质与未污染的有较大差别,污染后沉积物的重度、渗透系数和强度等均有所降低.污染后的沉积物结构,多成块状和板状结构.  相似文献   

珠江磨刀门水道咸潮上溯加剧的原因   总被引：1，自引：0，他引：1  

韩志远  田向平  刘峰 《海洋学研究》2010,28(2):52-59

对磨刀门水道不同年份地形资料和多年枯季潮位资料进行了对比分析,结果表明:大规模的河床采砂,引起磨刀门上游河段河床大幅下切,河道深泓平均加深0.59~2.25 m,河槽容积平均增加8.91×106~12.11×106m3,使该河段枯季潮差增大,进潮量增加,潮汐动力增强,导致咸水界向上游河段推移;口门围垦整治后,磨刀门口门区由众多岛屿环抱而成的内海区变成人工导堤控制的"一主一支"两条水道,水域面积减少了80%,河槽容积减少了40%,深槽趋于顺直加深,使口门区的"调淡"作用消失,这是咸潮上溯的重要原因;根据多年水文频率分析,发生严重咸潮灾害时,西、北江枯季流量并非都是枯水流量,因此枯季上游来水量变化并不是近年来咸潮灾害加剧的主要原因。  相似文献   

Spatial and temporal patterns in the hyperbenthic community structure in a warm temperate southern African permanently open estuary     

Elodie Heyns  William Froneman 《Estuarine, Coastal and Shelf Science》2010

The spatial and temporal patterns in the hyperbenthic community structure (>500 μm) in the warm temperate, permanently open Kariega Estuary situated along the south-eastern coastline of South Africa was investigated monthly over a period of twelve months. Data were collected using a modified hyperbenthic sledge at six stations along the length of the estuary. Physico-chemical data indicate the presence of a constant reverse salinity gradient, with highest salinities measured in the upper reaches and lowest at the mouth of the estuary. Strong seasonal patterns in temperature, dissolved oxygen and total chlorophyll-a (chl-a) concentration were evident. Total average hyperbenthic densities ranged between 0.4 and 166 ind.m⁻³ in the lower net and between 0.2 and 225 ind.m⁻³ in the upper net. Hyperbenthic biomass values ranged between 0.02 and 11.9 mg.dry weight.m⁻³ in the lower net and between 0.02 and 17.4 mg.dry weight.m⁻³ in the upper net. Both the lower and upper nets were numerically dominated by decapods (mainly brachyuran crab zoea) with the exception of June and July 2008 when mysids (mainly Mesopodopsis wooldridgei) dominated, comprising up to 72.4 ± 58.14% of the total abundance in the lower net. A redundancy analysis (RDA) indicated that 99.2% of the variance in the hyperbenthic community structure could be explained by the first two canonical axes. Axis one, which accounted for 96.8% of the total variation detected in the ordination plot was highly correlated with sedimentary organic content and to a lesser extent the chl-a concentration within the Kariega Estuary. The correlations with the second canonical axis (2.4%) were less obvious, however, salinity and seston concentration were weakly correlated with this axis.  相似文献   

Analysis of the spatial variation of heavy metals in the Guadiana Estuary sediments (SW Iberian Peninsula) based on GIS-mapping techniques     

J. Delgado  J.M. Nieto  T. Boski 《Estuarine, Coastal and Shelf Science》2010

This work reveals the usefulness of the GIS (Geographic Information Systems) mapping techniques to show the distribution of pollutants along an estuarine environment, as the final stage of a thorough study. In the case of study, the environmental quality of the sediments in the Guadiana river estuary was determined by means of a complete geochemical characterization consisting on the calculation of enrichment factors for the most important metals and metalloids (compared with the local background of non-contaminated sediments). The obtained results were depicted in “enrichment distribution maps” which evidenced a distribution of the elements in two groups: Group-I, elements with natural origin (Al, Fe, Mn, Co, and Cr) distributed homogeneously along the basin, and Group-II, elements associated to anthropic origin (As, Cd, Cu, Pb, Ni and Zn) with clear punctual sources besides a high concentration all over the estuary. The enrichment factors for the elements of Group-II are indicative of the existence of a noticeable diffuse historical mining pollution associated with the acid mine drainage generated in the internal zones of the basin, which could overlap minor pollution inputs from other human activities. The obtained results lead us to a reconsideration of the traditionally thought “unpolluted” environment when it was compared to nearby estuaries.  相似文献   

Spatial and temporal distributions of nitrogen, phosphorus and heavy metals in the intertidal sediment of the Chang jiang River Estuary in China   总被引：2，自引：0，他引：2  

QUAN Weimin  SHI Liyan  HAN Jindi  PING Xianyin  SHEN Anglv  CHEN Yaqu 《海洋学报(英文版)》2010,29(1):108-115

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.  相似文献   

闽江河口湿地典型植物群落及交错带植硅体碳分布特征研究     

米慧珊  高会  翟水晶  孙志高  何涛 《第四纪研究》2019,39(1):99-107

湿地既是"碳汇"也是"碳源",研究发现,碳可以被长久稳定地封存在植硅体内,不同植物的植硅体封存碳的能力有明显差异。选取闽江河口鳝鱼滩湿地芦苇群落、短叶茳芏群落、互花米草群落及交错带为研究对象,研究这3种植物植硅体碳(Phytolith-Occluded Carbon,简称PhytOC)含量和储量的空间变化特征和影响因素,探讨PhytOC含量在纯群落和交错带的差异,为研究植物竞争和碳循环过程提供依据。结果表明:受水文条件、植物生长和空间扩展等影响,闽江河口湿地植物PhytOC含量整体表现为近岸区高于近海区,PhytOC储量表现为纯群落高于交错带。PhytOC含量依次表现为芦苇纯群落(4.14 mg/g) > 交错带芦苇(3.67 mg/g) > 与芦苇交错的短叶茳芏(3.08 mg/g) > 互花米草纯群落(2.70 mg/g) > 与互花米草交错的短叶茳芏(1.96 mg/g) > 交错带互花米草(1.86 mg/g) > 短叶茳芏纯群落(1.75 mg/g)。短叶茳芏与芦苇相互扩展中短叶茳芏植物整体及各器官PhytOC含量均升高,而与互花米草相互扩展时短叶茳芏除了根系、茎以外各器官PhytOC含量均下降。3种植物各器官在交错带中PhytOC储量分配比明显不同于纯群落,根系PhytOC储量的分配比上升,提高了根系竞争力。芦苇、短叶茳芏、互花米草通过植硅体封存的碳储量分别占植物碳储量的0.27%、0.15%和0.07%,但植物间的扩展过程影响了植物的PhytOC储量,其中短叶茳芏与互花米草形成的交错带中短叶茳芏下降幅度最高(56.29%),互花米草下降幅度最低(26.15%)。由此可见,植物的空间扩展对植物PhytOC含量、储量以及在不同器官的分配比都有一定的影响,短叶茳芏在与芦苇和互花米草竞争时分别采取不同的PhytOC分配机制。  相似文献   

土地利用方式对珠江河口生态环境的影响分析   总被引：1，自引：1，他引：0  

李英  王中根  彭少麟  陈宝明 《地理科学进展》2008,27(3):55-59

本文探讨了珠江三角洲近年来主要土地利用方式的变化,其中城市化和植被覆盖的减少,以及农业施肥量 的增加,是造成陆源污染物增加的主要原因。分析了影响珠江河口生态环境的主要陆源污染物(泥沙、氮磷营养元 素、重金属和有机物)的产生和迁移过程,以及对河口生态环境的影响关系。从分析中可以看到,土地利用的变化能 够影响陆源污染物质的产生和迁移,合理的土地利用方式是降低陆源污染物质,改善珠江河口生态环境的重要措 施。陆源物质的产生与水循环密切相关,利用流域分布式水循环模型量化研究不同土地利用下的陆源物质产生、迁 移以及对河口生态环境的影响是未来主要发展方向。  相似文献   

闽江河口湿地芦苇和互花米草生物量季节动态研究     

ZHANG Lin-hai  ZENG Cong-sheng  TONG Chuan 《福建地理》2008,(2)

通过对闽江河口湿地芦苇(Phragmites australis)和互花米草(Spartina alterniflo-ra)群落特征和生物量的调查,结果表明:2种植物株高和密度呈显著负相关.芦苇地上部各构件生物量最大值出现在夏季,其值为1 524.8±78.85 g.m-2;互花米草最大值出现在秋季,其值为3 037.2±248.78 g.m-2.互花米草地上生物量显著大于芦苇(P<0.05),但立枯量无显著差异(P>0.05).2种植物地下生物量均为0~15 cm>15~30 cm>30~60 cm;芦苇夏季各层生物量极显著大于其他季节(P<0.05),互花米草地下各层生物量在冬季达到最大,生长季节逐渐下降,夏季最小.芦苇和互花米草总生物量积累动态呈典型的单峰值曲线,总生物量互花米草高于芦苇,但二者差异不显著.随着入侵时间推移,互花米草总生物量还要持续增长.  相似文献