Regional variations in trace element concentrations in tissues of black tiger shrimp Penaeus monodon (Decapoda: Penaeidae) from South Vietnam

The goal of the present study was to examine the specific bioaccumulation of 22 trace elements in muscle, exoskeleton and hepatopancreas of black tiger shrimp Penaeus monodon from the Mekong River Delta (MRD), and the South Key Economic Zone (SKEZ), South Vietnam. The general tendency in most trace element concentrations among different tissues were hepatopancreas>exoskeleton>muscle. Comparisons of trace element levels in tissues between the two regions showed that concentrations of Se in muscle and As in all three tissues were higher in SKEZ; whereas in MRD, the higher concentrations of most elements such as Mn, Cu, Cd, Ba, Hg, were observed in tissues. These geographical variations in trace element levels may reflect the differences in human activities between the two regions of South Vietnam. The target hazard quotient (THQ) values for trace elements (<1) indicate that local residents are not exposed to potential health risks via the consumption of shrimp.     

Contamination status and accumulation profiles of organotins in sea otters (Enhydra lutris) found dead along the coasts of California, Washington, Alaska (USA), and Kamchatka (Russia)

Organotin compounds (OTs) including mono- to tri-butyltins, -phenyltins, and -octyltins were determined in the liver of adult sea otters (Enhydra lutris) found dead along the coasts of California, Washington, and Alaska in the USA and Kamchatka, Russia. Total concentrations of OTs in sea otters from California ranged from 34 to 4100ng/g on a wet weight basis. The order of concentrations of OTs in sea otters was total butyltins>total octyltins> or = total phenyltins. Elevated concentrations of butyltins (BTs) were found in some otters classified under 'infectious-disease' mortality category. Concentrations of BTs in few of these otters were close to or above the threshold levels for adverse health effects. Total butyltin concentrations decreased significantly in the livers of California sea otters since the 1990s. Based on the concentrations of organotins in sea otters collected from 1992 to 2002, the half-lives of tributyltin and total butyltins in sea otters were estimated to be approximately three years.     

Arsenic species and their accumulation features in green turtles (Chelonia mydas)

Total arsenic (As) and its compounds were determined in liver, kidney, muscle, and stomach contents of green turtles (Chelonia mydas). Total As concentrations in the muscle were higher than those in the kidney and liver. Arsenobetaine (AB) was the predominant compound in all the three tissues and its levels were positively correlated with total As concentrations. This indicates that AB greatly contributes to As accumulation in green turtles. Higher concentrations of remaining As in the sample after extraction were detected in the liver, implying that lipid-soluble or protein bound As compounds accumulate in the liver of green turtles. Total As levels in tissues showed significant negative correlations with standard carapace length. The size-dependence of As accumulation in green turtles may be related to their feeding habit, shifting from carnivore to herbivore at different growth stages. Concentrations of AB and dimethylarsinic acid (DMA) were low in the stomach contents but high in the tissues, implying bioaccumulation of these arsenicals in green turtles.     

Effects of fish farm waste on Posidonia oceanica meadows: synthesis and provision of monitoring and management tools

This paper provides a synthesis of the EU project MedVeg addressing the fate of nutrients released from fish farming in the Mediterranean with particular focus on the endemic seagrass Posidonia oceanica habitat. The objectives were to identify the main drivers of seagrass decline linked to fish farming and to provide sensitive indicators of environmental change, which can be used for monitoring purposes. The sedimentation of waste particles in the farm vicinities emerges as the main driver of benthic deterioration, such as accumulation of organic matter, sediment anoxia as well as seagrass decline. The effects of fish farming on P. oceanica meadows are diverse and complex and detected through various metrics and indicators. A safety distance of 400 m is suggested for management of P. oceanica near fish farms followed by establishment of permanent seagrass plots revisited annually for monitoring the health of the meadows.     

不同类型流冰碛物的特征和成因

对波兰东北部尾碛及其衍生的冲积扇的野外研究提供了一个对比流冰碛物与其来源物质结构变化的很好的机会。研究发现流冰碛物在很大程度上继承了其原始物质的结构特征，但特殊的物质搬运机制在决定他们结构中起更重要的作用。这一发现表明基于流冰碛物的结构特征，多数情况下可以重建他们的成因。26个测站的野外数据表明：所有流冰碛物都落在一个以结构和构造性质逐渐变化为特征的系列内，从传统的富含粘土的冰川混杂沉积物变化到以混积砂、砾为特征的冰水沉积物。可以将它们分为三类，每一类又可分为三种。冰碛物的六种主要的结构、构造组合的系列反映了从高粘滞性泥石流到超浓缩流的不同类型的块体流。     

Three-dimensional refined modeling of water quality in Victoria Harbour

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青藏高原东北缘岩石层结构:高原横向生长的机制

青藏高原东北缘及其周边亚洲板块(北部到阿拉善块体,东部到鄂尔多斯块体)岩石层结构的探测对了解青藏高原的抬升和横向生长具有重要的意义。本研究利用布设在青藏高原东北缘和周边区域的高密度地震台阵所记录的波形,计算S波和P波接收函数,研究岩石层结构。结果表明,鄂尔多斯块体和阿拉善块体下方的地幔岩石层中存在较强、相对稳定的负速度梯度,其深度范围在70~150km,这与典型稳定的大陆岩石层类似;相比之下,在青藏高原东北部下方地幔岩石层的速度梯度相对较弱和较模糊,这可能是由于地幔岩石层高温和存在部分熔融物质造成的;青藏高原与鄂尔多斯块体和阿拉善块体边界之间的岩石层结构变化剧烈,这两个块体作为刚性边界限制了青藏高原的横向变化。此外,在青藏高原东北角到银川地堑区域的地幔岩石层结构是相似的,这可能意味着从青藏高原东北角到鄂尔多斯块体和阿拉善块体之间的过渡间隔区内存在横向地幔流。这个过渡带的地壳结构为青藏高原横向生长提供了证据。特别是,在海原断裂和天景山断裂之间出现了地壳增厚和双地壳的证据,该区域可能是青藏高原在东北缘横向生长的前沿。     

区域地震滑坡体积优化模型

求取滑坡体积在当前是一个难题,原因是其为三维分量,并且部分滑面往往在地下。本文提出了3个区域地震滑坡体积优化模型来计算2008年中国汶川M W7.9地震触发滑坡的体积。本文首先基于20m分辨率的震前和震后SPOT 5卫星影像提取到的数字高程模型(DEM)数据,结合少数滑坡的剖面图,获得了1 415处汶川地震滑坡堆积区体积,作为地震滑坡体积模型训练样本。在常规区域滑坡"体积—面积"模型基础上,提出了3个优化模型。分别利用数据的对数化线性拟合与直接非线性拟合方法对1个常规模型和3个优化模型进行拟合。结果表明,采用直接非线性拟合方法并考虑了滑坡长、宽、高、岩性、坡度和峰值地动加速度后,坡向的优化模型标准误差最小,回归得到的滑坡总体积与滑坡真实总体积也非常接近。将这一模型应用于所有汶川地震滑坡,分别得到每个滑坡的体积。最终结果表明,汶川地震滑坡相对密集分布区内的196 007处滑坡的堆积物体积约为1.2×1010 m~3,源区体积约为1×1010 m~3。根据前人"地震震级—滑坡总体积"经验公式得到的结果仅仅是本文结果的7.5%~9%,这提醒我们有必要基于更多的单次地震触发滑坡总体体积数据对"地震震级—滑坡总体积"的关系进行更新。同时,文中的优化模型对同类研究也有显著的参考价值。     

基于计算智能技术的巴基斯坦北部地区地震活动性预测

本文针对巴基斯坦北部地区进行了地震预测研究。研究方法包含了地震学和计算智能技术领域不同学科的交叉融合。针对历史地震活动计算了8种地震学参数。通过计算它们的信息增益来评估这8种参数的预测效能,进而选择了其中6种应用于预测试验。基于这6种参数发展了多个计算智能模型用于预测试验。这些模型包括前馈神经网络、循环神经网络、随机森林、多层感知、径向基神经网络和支持向量机。本文评估了每一种模型的效能,同时利用McNemar统计检验方法来研究计算方法的统计显著性。前馈神经网络模型在巴基斯坦北部地区可表现出统计显著性为75%准确率和78%正确预报的预测结果。     

汶川—芦山地震之间地震空区及邻区的微震时空分布特征及指示意义

在龙门山西南段,汶川和芦山两次地震之间地震空区产生的物理机制及其未来的地震活动性仍然是亟需进一步研究的问题。现有研究结果也无法完全解释地震空区挤压应变/应力的调节模式。我们使用Match and Locate方法获取了2015年5月至12月时段内空区及邻区的详细的背景地震目录,完备性震级为M_c=0.2,微震的时空分布特征凸显了小震级事件的丛集(簇)特征。在深度域上,微震在空区两端的优势深度存在明显差异,南端深于北端,表明空区作为汶川和芦山两次地震破裂的转换带。我们的微震探测结果表明空区存在明显的微震"亏空",否定了其通过微地震释放累积应力的调节模式。我们发现该区域内,不同震级范围内的背景地震活动性都与降雨变化率存在明显的反相关关系。在夏、秋季节,地震活动性极值滞后于降水极值1～2个月,库仑模型计算表明增强的地震活动性很可能被浅地表含水量的减少所触发,季节性降水在一定程度上调节了背景地震活动性。相较于震级大于3.0的背景地震,背景微震对降水的变化具有更敏感的响应,这可能由其更短的起始周期所致。