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1.
Concentrations of Fe, Zn, Cu, Se, Mn, Mo, Hg, Cd, Cr, Ag, Pb, Sr and V were determined in skins of Dall's porpoises (Phocoenoides dalli) of the Pacific coast truei-type population (PT population) (N=45), and the Sea of Japan-Okhotsk dalli-type population (JD population) (N=31) from the northern waters of Japan. Cutaneous Hg concentrations in both PT and JD populations were significantly correlated with age, indicating a possible alternative method of age estimation. A significant correlation was also noted between Hg concentrations in skin and liver, suggesting that biopsy samples of skin can provide a non-lethal surrogate for monitoring Hg contamination in this species. Trace element accumulation patterns differed strongly between PT and JD populations, when analyzed by principal component analysis, suggesting these patterns could be utilized as non-lethal tracers of population identification.  相似文献   

2.
Total Hg (∑Hg), organic-Hg (O-Hg) and Se bioaccumulations in small cetaceans distributed in Taiwanese waters of the Taiwan Strait and the southwestern Pacific have been investigated for the first time. The results could represent the baseline metal concentrations of marine mammals in the southwestern Pacific, where volcanic activities are possibly the major source of mercury to the environments. Muscle samples of four species of small cetaceans were collected from animals accidentally caught by tuna-longline fisheries from 1994 through 1995. In total, 53 pantropical spotted dolphins, Stenella attenuata, nine spinner dolphins, S. longirostris, five bottlenose dolphins, Turiops truncatus and four Risso's dolphins, Grampus giseus were analyzed. In addition, two stranded pantropical spotted dolphins were investigated. Cold vapour AAS and ICP-MS were used in the analysis of Hg and Se, respectively. Significant species difference was found in the four species of small cetaceans. Among them, the pantropical spotted dolphin showed the highest mean concentration (mg/kg wet wt.) of both ∑Hg (3.64±2.19) and O-Hg (2.79±1.23), whereas the Risso's dolphin had the highest mean concentrations of Se (1.77±1.29). There was no significant sex difference with respect to metal bioaccumulation in the samples of S. attenuata. Significant correlations between body length (BL) and ∑Hg, as well as O-Hg concentrations were observed in pantropical spotted (Sa) and spinner dolphins (Sl). The linear relationships were Sa: ∑Hg=−8.290+0.066BL, r=0.421; Sl: ∑Hg=−2.735+0.025BL, r=0.875; Sa: O-Hg=−3.723+0.036BL, r=0.408; and Sl: O-Hg=−3.017+0.025BL, r=0.870. However, a demethylation phenomenon that decreasing the percentage of O-Hg coupled with increasing levels of Se was observed when the ∑Hg concentrations in the muscle tissues of dolphins reached 4 mg/kg wet wt.  相似文献   

3.
压制数值频散,提高正演模拟精度,一直是有限差分正演模拟研究的重要内容.基于时空域频散关系的有限差分法,比基于空间域频散关系的传统有限差分法,模拟精度更高.时空域声波方程数值模拟,普遍采用常规十字交叉型高阶有限差分格式.而在频率-空间域,普遍采用旋转网格和常规网格混合的有限差分格式,有效提高了模拟精度和计算效率.本文将频率-空间域混合网格有限差分的思想引入到时空域,提出了时空域混合网格2 M+N型声波方程有限差分方法.首先推导出基于时空域频散关系的混合网格差分系数计算方法,然后进行频散分析、稳定性分析,并和传统高阶、时空域高阶有限差分法对比,结果表明:计算量相同时,新方法能有效压制数值频散,显著提高模拟精度;新方法相比传统2 M阶有限差分法,稳定性增强,与时空域2 M阶有限差分法稳定性基本相当.最后利用新方法进行均匀介质、层状介质、盐丘模型的数值模拟和盐丘模型的逆时偏移,模拟效果和成像质量进一步证实了该方法的有效性和普遍适用性.  相似文献   

4.
基于三维Taylor模型的福建及邻近地区地磁模型研究   总被引：1，自引：1，他引：0       下载免费PDF全文
基于福建及邻近地区高密度的256个地磁场矢量(D、I、H分量)实测数据,结合全球陆地1km基准海拔高度工程的网格数据以及最新的第十二代国际地磁参考场模型(IGRF12),采用三维Taylor多项式模型构建了福建地区的地磁场模型.通过比较均方偏差(RMS)、磁场实际分布以及残差等,结果显示:(1)当三维Taylor模型的截断阶数(N)为2时,可基本反映N为6时的二维Taylor模型的拟合效果;(2)三维Taylor模型计算方便,精度较高,但较易出现龙格现象,因此在确定截断阶数时既要考虑模拟精度,还需要考虑边界效应问题.  相似文献   

5.
This paper presents the results of a 6-year (1998–2003) survey of trace toxics in the intertidal mussel Perna viridis conducted by the Hong Kong Environmental Protection Department. Concentrations of heavy metals and trace organics were measured in the soft bodies of P. viridis collected from five sites in Hong Kong waters, i.e. Wu Kai Sha (Tolo Harbour), Ma Wan (Northwest), Tsim Sha Tsui (Victoria Harbour), Tai Tam (Hong Kong South) and Lamma Island (Southern Waters) in order to establish the spatial patterns of contaminants in mussels. Among the metals analysed, Cd showed a significant concentration gradient in Hong Kong waters. The levels of Cd in P. viridis were significantly higher at Ma Wan as compared to the other sites studied. Ma Wan also had relatively higher concentrations of Pb. Mn concentrations were particularly prominent at Wu Kai Sha. Significantly higher concentrations of Hg and Cu were recorded at Tai Tam and Tsim Sha Tsui. Tai Tam and Wu Kai Sha had higher levels of V; whereas higher Ni concentrations were recorded at Lamma Island and Tai Tam. No clear spatial patterns for Al, As, Cr, Fe and Zn were observed.

Higher concentrations of PAHs in P. viridis were observed around urban centres impacted by sewage discharges (e.g. Tsim Sha Tsui); whereas higher PCB levels were found not only in Tsim Sha Tsui but also in less urbanised areas such as Lamma Island and Tai Tam, suggesting that these may be due to non-sewage related inputs. The study also shows that Northwest and Southern waters are subject to a higher degree of DDT pollution compared with other sites. Of the 17 dioxin compounds analysed, positive data were mostly recorded for two compounds which are of low toxicity (i.e. OCDD and 1,2,3,4,6,7,8-HpCDD) whereas the most toxic congeners (i.e. 2,3,7,8-TCDD and 1,2,3,7,8-PeCDD) were not detected in the 6 years of monitoring. In general, the levels of OCDD in P. viridis were found to be higher in Tai Tam and Lamma Island in Southern Waters of Hong Kong.

This study found that the levels of some highly toxic heavy metals (i.e. Cd, Hg and Pb) in the mussel P. viridis did not exceed the recommended limits for shellfish as food in Hong Kong (i.e. Cd: 2.0 ppm; Hg: 0.5 ppm; Pb: 6.0 ppm wet weight). The levels of As and Ni in P. viridis were also well below the action limits set by the US FDA (i.e. As: 86 ppm; Ni: 80 ppm wet weight). DDT and PCB contaminations in P. viridis were below the concentrations of concern. Compared with data obtained in the 1980s, the current levels of DDTs in P. viridis were 4–16 times lower; whereas Pb concentrations recorded in Tsim Sha Tsui have also been lowered significantly. This is mainly related to reduction in local and regional pollution sources in the past 20 years.  相似文献   


6.
In the Mediterranean Sea, top predators, and particularly cetacean odontocetes, accumulate high concentrations of organochlorine contaminants and toxic metals, incurring high toxicological risk. In this paper we investigate the use of the skin biopsies as a non-lethal tool for evaluating toxicological hazard of organochlorines in Mediterranean cetaceans, presenting new data 10 years after the paper published by Fossi and co-workers [Mar. Poll. Bull. 24 (9) (1992) 459] in which this new methodology was first presented. Some organochlorine compounds, now with worldwide distribution, are known as endocrine disrupting chemicals (EDCs). Here the unexplored hypothesis that Mediterranean cetaceans are potentially at risk due to organochlorines with endocrine disrupting capacity is investigated. High concentrations of DDT metabolites and PCB congeners (known as EDCs) were found in the different Mediterranean species (Stenella coeruleoalba, Delphinus delphis, Tursiops truncatus and Balaenoptera physalus). In this paper we also propose benzo(a)pyrene monooxygenase (BPMO) activity in marine mammal skin biopsies (non-lethal biomarker) as a potential indicator of exposure to organochlorines, with special reference to the compounds with endocrine disrupting capacity. A statistically significant correlation was found between BPMO activity and organochlorine levels (DDTs, pp(')DDT, op(')DDT, PCBs and PCB99) in skin biopsies of males of B. physalus. Moreover a statistical correlation was also found between BPMO activity and DDT levels in skin biopsies of the endangered Mediterranean population of D. delphis. These results suggest that BPMO induction may be an early sign of exposure to organochlorine EDCs and can be used for periodic monitoring of Mediterranean marine mammal toxicological status.  相似文献   

7.
Concentrations of trace elements (V, Cr, Mn, Fe, Co, Cu, Zn, Ga, As, Se, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, T-Hg, Org-Hg, Tl and Pb) were determined in liver samples of estuarine dolphin (Sotalia guianensis; n = 20), Franciscana dolphin (Pontoporia blainvillei; n = 23), Atlantic spotted dolphin (Stenella frontalis; n = 2), common dolphin (Delphinus capensis; n = 1) and striped dolphin (Stenella coeruleoalba; n = 1) incidentally caught along the coast of Sao Paulo State and Parana State, Brazil, from 1997 to 1999. The hepatic concentrations of trace elements in the Brazilian cetaceans were comparable to the data available in literature on marine mammals from Northern Hemisphere. Concentrations of V, Se, Mo, Cd, T-Hg and Org-Hg increased with increasing age in liver of both estuarine and Franciscana dolphins. Very high concentrations of Cu (range, 262-1970 microg/g dry wt.) and Zn (range, 242-369 microg/g dry wt.) were observed in liver of sucklings of estuarine dolphin. Hepatic concentrations of V, Se, T-Hg, Org-Hg and Pb were significantly higher in estuarine dolphin, whereas Franciscana dolphin showed higher concentrations of Mn, Co, As and Rb. Ratio of Org-Hg to T-Hg in liver was significantly higher in Franciscana dolphin than estuarine dolphin, suggesting that demethylation ability of methyl Hg might be lower in liver of Franciscana than estuarine dolphins. High hepatic concentrations of Ag were found in some specimens of Franciscana dolphin (maximum, 20 microg/g dry wt.), and 17% of Franciscana showed higher concentrations of Ag than Hg. These samples with high Ag concentration also exhibited elevated hepatic Se concentration, implying that Ag might be detoxified by Se in the liver. Higher correlation coefficient between (Hg+0.5 Ag) and Se than between Hg and Se and the large distribution of Ag in non-soluble fraction in nuclear and mitochondrial fraction of the liver also suggests that Ag might be detoxified by Se via formation of Ag2Se in the liver of Franciscana dolphin.  相似文献   

8.
Oyster tissues may be affected by the concentration of ions in the water (i.e. salinity) and by contaminants such as petroleum hydrocarbons and heavy metals. Oyster populations from three coastal lagoons (Mecoacan, Camen and Machona) in the Mexican state of Tabasco, in the southern Gulf of Mexico, were sampled for pollution studies during June, September and November 1992 and May 1993. No statistically significant relationships were found between the concentration of contaminants in the body tissues of organisms and their shell length, soft tissue weight and particulate matter; however, a significant correlation was found between condition index and salinity (r = −0.72). Generally, the lowest weights, shell lengths and indices of condition were found in Mecoacan. The concentrations of cadmium and zinc were inversely related to salinity (r = −0.52 and r = −0.32, respectively), so a riverine input is suspected. On average, 63% of the individual oysters showed histopathological lesions, which can be related to salinity and to the concentrations of cadmium and the unresolved fraction of hydrocarbons (UCM). The response of each of the tissues analysed was different. The percentage of individuals with damage in the digestive diverticulum increased linearly with UCM (r = 0.71), but in a saturation-response fashion (Y = B0 − B0/(1 + XB1) r = 0.66) with cadmium. The percentage of individuals with damage in the gills increased linearly with weight (r = 0.68), cadmium (r = 0.60) and UCM (r = 0.60). The lesions in the connective tissue decreased linearly (r = −0.82) with salinity, but increased in a saturation-response way (r = 0.83) with cadmium. Finally, the percentage of individuals with lesions in the digestive tube decreased linearly with salinity (r = −0.59). Only the damage to the gills and digestive diverticula were dependent on gonadal maturity, while damage to the connective tissue was dependent on the sex of the individual.  相似文献   

9.
Blubber samples of 2 cetacean species, the Indo-Pacific hump-backed dolphin (Sousa chinensis) (n=11) and finless porpoise (Neophocaena phocaenoides) (n=9), collected from Hong Kong coastal waters were analysed for persistent organochlorines. Mean concentration in the blubber of DDTs was ranked first (46 μg/g wet wt.), followed by PCBs (24 μg/g wet wt.), HCHs (0.76 μg/g wet wt.), chlordane compounds (0.38 μg/g wet wt.) and HCB (0.07 μg/g wet wt.). The present cetacean species may potentially be faced with high risk due to the elevated level of DDTs and PCBs. Relatively high concentrations of PCBs and DDTs can be attributed to the continuous environmental input of these compounds in the Far East region including Hong Kong. Highly chlorinated PCBs such as IUPAC Nos. 138, 153, 180 were the prominent congeners, accounting for 39% of the total PCBs. Mean concentrations of 6 non- and mono-ortho coplanar congeners were 2.1 and 2.8 μg/g wet wt. in the hump-backed dolphin and finless porpoise, respectively. Among highly toxic coplanar PCBs, mono-ortho congener IUPAC No. 118 and non-ortho congener IUPAC No. 126 were estimated to have the greatest toxicity contribution. Tris(4-chlorophenyl) methane (TCPMe) and tris(4-chlorophenyl) methanol (TCPMeOH), which have been the most recently identified microcontaminants, were also detected with the highest concentration of 290 and 300 ng/g (wet wt. basis), respectively. The concentrations of TCPMe relative to TCPMeOH in cetaceans from Hong Kong coastal waters were significantly higher than those found in various seals collected from other parts of the world, suggesting the different metabolic system of these two compounds between seals and cetaceans. Correlations between the concentrations of tris-chlorophenyl compounds with other persistent organochlorines such as HCHs, CHLs, DDTs and PCBs were significant, suggesting their accumulation nature similar to these organochlorines.  相似文献   

10.
Concentrations of 19 trace elements (V, Cr, Mn, Fe, Co, Cu, Zn, Se, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, Tl, Hg, and Pb) were determined in the liver of the striped dolphins (Stenella coeruleoalba) collected around Japan during 1977-1982 to examine the sex difference, age dependence, and interrelationships among trace elements. Tissue distribution of trace elements was also investigated in one adult and one fetus specimens. Generally, concentrations of Se, Sr, Ag, Cd, Cs, Ba, Hg, and Pb were higher in the tissues of adult than those of fetus, whereas the opposite trend was observed for Cr and Tl. There were no significant sex differences in the trace element levels in the liver. Significant positive correlations between age (0-26.5 years) and hepatic concentrations were found for Ag, Se, Hg, V, Fe, Pb, and Sr, suggesting their age-dependent accumulation in the liver. In contrast, hepatic concentrations of Mn and Zn decreased with age. Significant positive relationships were observed between Se, and Hg, Ag, V, Fe, and Sr in the liver.  相似文献   

11.
This paper reports on mercury (Hg) concentrations in different tissues (liver, muscle, kidney, blubber and brain) of harbour porpoises Phocoena phocoena found dead in the Black Sea between 1997 and 1999, mainly bycaught in fishing nets (n = 79). Total Hg and organic Hg (MeHg) were determined. The main factor affecting Hg accumulation was, as expected, age, with MeHg concentration increasing with age. Accumulation of high concentrations of inorganic Hg in the liver was probably due to a slow demethylation process implying the formation of tiemannite (HgSe). In older adults, liver concentrations reached 35 microg g(-1) dry weight ('ppm') total Hg and 3 microg g(-1) dw MeHg. A geographical comparison with existing data from other regions showed a generally low Hg contamination of Black Sea porpoises, one order of magnitude lower than, e.g. in the North Sea.  相似文献   

12.
《Marine pollution bulletin》2009,58(6-12):807-815
Concentrations of 19 trace elements (V, Cr, Mn, Fe, Co, Cu, Zn, Se, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, Tl, Hg, and Pb) were determined in the liver of the striped dolphins (Stenella coeruleoalba) collected around Japan during 1977–1982 to examine the sex difference, age dependence, and interrelationships among trace elements. Tissue distribution of trace elements was also investigated in one adult and one fetus specimens. Generally, concentrations of Se, Sr, Ag, Cd, Cs, Ba, Hg, and Pb were higher in the tissues of adult than those of fetus, whereas the opposite trend was observed for Cr and Tl. There were no significant sex differences in the trace element levels in the liver. Significant positive correlations between age (0–26.5 years) and hepatic concentrations were found for Ag, Se, Hg, V, Fe, Pb, and Sr, suggesting their age-dependent accumulation in the liver. In contrast, hepatic concentrations of Mn and Zn decreased with age. Significant positive relationships were observed between Se, and Hg, Ag, V, Fe, and Sr in the liver.  相似文献   

13.
Concentrations of 19 trace elements (V, Cr, Mn, Fe, Co, Cu, Zn, Se, Rb, Sr, Mo, Ag, Cd, Sb, Cs, Ba, Tl, Hg, and Pb) were determined in the liver of the striped dolphins (Stenella coeruleoalba) collected around Japan during 1977–1982 to examine the sex difference, age dependence, and interrelationships among trace elements. Tissue distribution of trace elements was also investigated in one adult and one fetus specimens. Generally, concentrations of Se, Sr, Ag, Cd, Cs, Ba, Hg, and Pb were higher in the tissues of adult than those of fetus, whereas the opposite trend was observed for Cr and Tl. There were no significant sex differences in the trace element levels in the liver. Significant positive correlations between age (0–26.5 years) and hepatic concentrations were found for Ag, Se, Hg, V, Fe, Pb, and Sr, suggesting their age-dependent accumulation in the liver. In contrast, hepatic concentrations of Mn and Zn decreased with age. Significant positive relationships were observed between Se, and Hg, Ag, V, Fe, and Sr in the liver.  相似文献   

14.
The concentrations of dissolved Cd, Cu, Hg and Pb in seawater and algae (Enteromorpha spp. and Porphyra spp.) were determined in parallel on three beaches located in the Oporto coast (Portugal), during 8 successive months, comprising periods of low and high biological productivity. The concentrations of dissolved metals in seawater varied markedly during the sampling period and exhibited seasonality. The concentrations of Cd were high in autumn and winter, but low in spring. The concentrations of Cu and Hg were high in autumn, low in winter and peaked in May. The concentrations of Pb were low in autumn and winter, and also peaked in May. It is likely that biological activity was, at least partially, responsible for the observed seasonal changes. The mean concentrations of dissolved metals in seawater were similar to those reported for polluted and industrialized european coastal areas. Metal concentration factors, calculated month-to-month for each alga, metal and site, varied markedly during the sampling period, indicating that concentration factors based on single or few determinations could be misleading. On the contrary, mean concentration factors (calculated by dividing the mean metal concentration in the algae by the mean metal concentration in seawater) were relatively constant at all three sites, indicating that in the Oporto coast, Enteromorpha spp. can be used to estimate the mean concentration of dissolved Cd, Cu and Hg in seawater, and Porphyra spp., the mean concentration of Cd, Cu and Pb. However, considering that future estimates of the concentrations of these metals in seawater should be based on determinations of the metal contents in Enteromorpha spp. and Porphyra spp. carried out on several occasions spanning a considerable period of time, the use of these algae as monitors of heavy metal pollution can have limited practical advantages over the direct assay of the metals in seawater.  相似文献   

15.
Different sizes of the dogwhelk Nucella lapillus were collected from eight locations along the southwest and north coasts of Iceland. Concentrations of total metallothioneins (MTs) and heavy metals (Cd, Cu, Cr, Mn, Ni, and Zn) were analysed using the silver saturation method and inductively coupled plasma-atomic emission spectrometry. The level of tributyltin (TBT) contamination was also assessed using imposex indices, the vas deferens stage index (VDSI) and relative penis size index (RPSI). Gufunes N. lapillus presented the highest values of VDSI (4.0) and RPSI (11.1), followed by Grenivík individuals (VDSI = 3.0; RPSI = 0.9), while the Strandakirkja population showed the lowest VDSI (0.3) and zero RPSI. At a standardised size (0.25 g dry soft-body weight), Grenivík N. lapillus exhibited significantly higher concentrations of all metals whereas overall metal concentrations were significantly lower in individuals from Strandakirkja and Garðskagi compared to other study sites. Partial correlation analyses with size correction indicated that MT concentrations were better correlated with Cd and Cu concentrations than with other metals. At the standard size, the pattern of MT concentrations in N. lapillus from different sites was, however, very different from those of metal profiles. Such discrepancies between the patterns of MT and metals in N. lapillus might be explained by the fact that MT induction could be influenced by various factors such as temperature, dietary metal intake, growth rate and co-existence of other MT-inducing chemicals.  相似文献   

16.
Individual based simulations of population dynamics require the availability of growth models with adequate complexity. For this purpose a simple-to-use model (non-linear multiple regression approach) is presented describing somatic growth and reproduction of Daphnia as a function of time, temperature and food quantity. The model showed a good agreement with published observations of somatic growth (r2 = 0.954, n = 88) and egg production (r2 = 0.898, n = 35). Temperature is the main determinant of initial somatic growth and food concentration is the main determinant of maximal body length and clutch size. An individual based simulation was used to demonstrate the simultaneous effects of food and temperature on the population level. Evidently, both temperature and food supply affected the population growth rate but at food concentrations above approximately 0.4 mg Cl−1 Scenedesmus acutus temperature appeared as the main determinant of population growth.

Four simulation examples are given to show the wide applicability of the model: (1) analysis of the correlation between population birth rate and somatic growth rate, (2) contribution of egg development time and delayed somatic growth to temperature-effects on population growth, (3) comparison of population birth rate in simulations with constant vs. decreasing size at maturity with declining food concentrations and (4) costs of diel vertical migration. Due to its plausible behaviour over a broad range of temperature (2–20 °C) and food conditions (0.1–4 mg Cl−1) the model can be used as a module for more detailed simulations of Daphnia population dynamics under realistic environmental conditions.  相似文献   


17.
The focus of this work is to explore the use of the netted whelk, Nassarius reticulatus (L.), as an indicator of mercury (Hg) contamination, by assessing the concentration of Hg in the sediments and in the whelk along the entire Portuguese coast. Total Hg concentrations ranged from below the detection limit (0.01 ng absolute mercury) up to 0.87 mg kg(-1) dry weight (dwt) in sediments and between 0.06 and 1.02 mg kg(-1) (dwt) for organisms, with no significant differences between males and females. Although organic mercury was not detected in the sediments, it represented, on average, 52% of the total Hg in the whelk tissues, and as high as 88% in some cases, suggesting mercury accumulation from dietary intake. Significant negative correlations were found between the total Hg concentrations in the sediments and the log(10) of Hg concentrations in whelk tissues males (r=-0.64; P<0.01) and females (r=-0.52; P<0.01) indicating that the species is a poor indicator of Hg contamination. Nevertheless, since the highest concentrations of organic mercury in the whelk tissues were found in the least contaminated areas, this species must be highly relevant in the trophic web, namely on the possible biomagnification of mercury. The high dietary mercury accumulation from feeding on carrion and the low bioavailability of mercury to whelks in estuarine sediments may be the basis of the mercury accumulation pattern in N. reticulatus.  相似文献   

18.
秦乃岗 《地震》2007,27(1):105-113
探讨了东南沿海地震带20世纪以来在时间分布方面存在的密集－平静相互交替的丛集现象。 对以往按地震能量释放的分布划分出的活跃—平静幕数目不等的多种结果; 对东南沿海地区54次M≥43/4地震的时间间隔序列, 在使用有序样品聚类分析中的“离差平方和”法及误差函数法, 从误差随分段数增加而减少的拐点值及误差函数比值认为四段活跃幕划分是合理的。 从 1943 年之后, 计算得出的东南沿海地区中强以上地震序列的时间变异系数δ值为1.2 , 明显处于丛集状态。 对东南沿海地震区20世纪以来四个地震活跃幕中, 其丛集非线性时间结构演化幂指数, 即各幕地震的累积频次与发震系统内部时间的关系基本符合为N=ctd。 4个活跃幕的演化幂指数d变化范围分布在0.7~0.8。 东南沿海地震区20世纪以来M6.0以上的强震也基本符合该关系式。 只是其活跃幕演化幂指数d为 0.47 。  相似文献   

19.
This study aimed at comparing toxic element (Hg, Cd) bioaccumulation in relation to age for bottlenose (Tursiops truncatus) and striped dolphins (Stenella coeruleoalba) from Mediterranean and Atlantic waters. Metal concentrations were also measured in selected prey to infer metal exposure through the diet. As expected, Mediterranean prey exhibited the highest Hg levels, probably as a consequence of the Hg enrichment of the Mediterranean Sea. Comparing the predators from each area and taking age into account, Mediterranean bottlenose dolphins displayed higher Hg levels than Atlantic dolphins (p = 0.032), whereas Mediterranean striped dolphins did not (p = 0.691). The consumption of Myctophid fish, which showed the highest Hg levels (105+/-80 ngg(-1) w.wt.) among Atlantic prey, may explain the high Hg levels in the liver of the Atlantic striped dolphins and suggested a preferential offshore feeding behaviour in this area. Concerning Cd, no clear differences were found between geographical areas.  相似文献   

20.
Mercury(Hg) is a global pollutant and can be accumulated in the food chain, posing exposure risks to humans. In this study, rice plants and corresponding rhizosphere soil samples were collected from a watershed of the Wawu River Basin that is heavily impacted by historic Hg mining and retorting activities. Total mercury(THg)and methylmercury(MeHg) in rice grains, as well as other tissues and soil samples, were measured. Five soil Hg fractions, as well as soil parameters, were also determined.The results show that the average concentrations of THg and MeHg in rice grains were 14 ± 7.0 lg kg-1 and7.2 ± 4.0 lg kg-1. Soil organic-bound(Hg-o) and strong complex-bound(Hg-s) were the main Hg fractions,accounting for 44% of the total. To estimate the Hg–ligand interaction in the soils, soil-N/Hg(R = 0.451, p \ 0.05),-S/Hg(R = 0.372, p \ 0.1), and-OM/Hg ratio(R = 0.320,p \ 0.5) with MeHgsoil were observed with significant positive correlations, indicating that the formation of Hg–OM, Hg–N–OM or Hg–S–OM complexes could prevent Hg(II) from methylation in soils. The significant positive correlations of the-N/Hg ratio,-S/Hg ratio and-OM/Hg ratio with MeHg in rice tissues suggested that Hg methylation and MeHg demethylation occurred throughout the rice paddy ecosystem. The estimated MeHg daily intake(EDI) was 0.075 ± 0.041 lg kg-1 bw d-1 and was lower than the RfD level of 0.1 lg kg-1 bw d-1 recommended by the US EPA. However, approximately 29% of the hazardous index(HI) of MeHg in grain exceeded 1, posing a potential threat to local populations, particularly pregnant women and children.  相似文献   

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