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1.
Dissolved trace element (copper, nickel, cadmium, zinc, cobalt, and iron) concentrations were measured in surface water samples collected from 27 stations in the San Francisco Bay and Sacramento—San Joaquin Delta during April, August and December of 1989. The trace element distributions were relatively similar for all three sampling periods, and evidenced two distinct biogeochemical regimes within the estuarine system. The two regimes were comprised of relatively typical trace element gradients in the northern reach and anthropogenically perturbed gradients in the southern reach of the estuary. These dichotomous trace element distributions were consistent with previous reports on the distributions of nutrients and some other constituents within the estuary.In the northern reach, trace element and dissolved phosphate concentrations were non-conservative. Simple estuarine mixing models indicated substantial internal sources of dissolved copper (46–150%), nickel (250–500%) and cadmium (630–780%) relative to riverine inputs in April and August, and sizable internal sinks for dissolved cobalt (> 99%) and iron (> 70%) during the same periods. Dissolved zinc fluxes varied temporally, with a relatively large (135%) internal source in April and a relatively small (29%) internal sink in August.Concentrations of many trace elements (copper, nickel, cadmium, zinc, and cobalt) in the southern reach were anomalously high relative to concentrations at comparable salinities in the northern reach. Mass balance calculations indicated that those excesses were primarily due to anthropogenic inputs (waste-water discharges and urban runoff) and diagenetic remobilization from benthic sediments. The magnitude of these excesses was amplified by the long hydraulic residence time of dissolved constituents within the South Bay.The influence of other factors was evident throughout the system. Notably, upwelling appeared to elevate substantially dissolved cadmium concentrations at the mouth of the estuary and authigenic flocculation appeared to dominate the cycling of dissolved iron in both the northern and southern reaches of the system. Biological scavenging, geochemical scavenging and diagenic remobilization were also found to be important in different parts of the estuary. Additional complementary information is required to quantify accurately these processes. 相似文献
2.
Plankton samples have been carefully collected from a variety of marine environments for major and trace-chemical analysis. The samples were collected and handled under the rigorous conditions necessary to prevent contamination of the trace elements. Immediately after collection, the samples were subjected to a series of physical and chemical leaching-decomposition experiments designed to identify the major and trace element composition of the biogenic particulate matter. Emphasis was placed on the determination of the trace element/major element ratios in the various biogenic phases important in biogeochemical cycling.The majority of the trace elements in the samples were directly associated with the non-skeletal organic phases of the plankton. These associations include a very labile fraction which was rapidly released into seawater immediately after collection and a more refractory component which involved specific metal-organic binding. Calcium carbonate and opal were not significant carriers for any of the trace elements studied. A refractory phase containing aluminum and iron in terrigenous ratios was present in all samples, even from remote pelagic environments. This non-biogenic carrier contributed insignificant amounts to the other trace elements studied.The plankton samples were collected from surface waters with a wide range in the dissolved trace element/nutrient ratios, however, the same elemental ratios in the bulk plankton samples were relatively constant in all these environments. The bulk compositions and the rapid release of the metals and nutrient elements (specifically phosphorus) from the plankton after collection were used to examine the systematics of depletions of the dissolved elements from surface waters. These elemental ratios were combined with known fluxes of the major biogenic materials to estimate the significance of the plankton in the vertical flux of the trace elements. In parallel with the major surface ocean cycles of carbon and nitrogen, significant fractions of the trace elements taken up by primary producers must be rapidly regenerated in order to explain the observed elemental compositions and fluxes. 相似文献
3.
Systems for the determination of trace element compounds consisting of liquid chromatographs (LC) (high pressure liquid chromatographs, ion chromatographs) and graphite furnace atomic absorption spectrometers (GFAAS) or inductively coupled argon plasma emission spectrometers (ICP) as single- or multi-element-specific detectors are described. The applications of these systems to the determination of arsenic compounds are reviewed. The absolute detection limits of these systems for arsenic are in the low nanogram range. These detection limits can probably be improved by two-three orders of magnitude by coupling an inductively coupled argon plasma-mass spectrometer instrument to the liquid chromatograph. The advantages and drawbacks of the LC-GFAAS and LC-ICP systems are outlined. These systems can separate and identify trace element compounds that are kinetically or thermodynamically stable under the conditions of the chromatography. Labile compounds cannot be determined by these systems. Wide application of these systems to problems of trace element research will lead to the identification of hitherto unknown trace element compounds, to a better understanding of the nutritional and toxic properties of trace element compounds, and to a better definition of trace element cycles. 相似文献
4.
莱州湾07钻孔沉积物晚更新世以来的元素地球化学特征 总被引：2，自引：0，他引：2
在莱州湾南岸的07孔岩心进行高分辨率采样的基础上,采用X荧光光谱法(XRF)、离子质谱法(ICP-MS)以及原子荧光光谱法(AF)等方法测试了研究区07孔的48种常微量元素以及稀土元素的含量,并对元素相对含量、随深度变化规律、特征比值以及稀土元素配分模式进行了研究。结果表明,07孔主要元素及特征比值在海陆地层分界处有明显变化,可以作为地层划分的指标之一。其中,Mn、Mg、Ca、Fe、Mg/Ca及K/Na等对沉积环境响应比较明显,Ba、Zr、Rb、Si/A1、Ti/A1和Rb/Sr对源区的母岩类型、风化程度及搬运距离的变化敏感;07孔常微量元素垂向变化较大,在3次海侵地层中呈明显变化,并对应多个峰值。化学元素的变化规律所反映的地层特征与晚更新世以来的气候和海平面的变化有较好的对应关系。07孔不同深度沉积物的稀土元素球粒陨石标准化配分模式与黄河沉积物的相似,呈轻稀土元素富集的右倾型。说明黄河是莱州湾南岸弥河-潍河多源河流三角洲沉积体系的物源之一,且对莱州湾南岸一定深度范围内的沉积地层有部分贡献。 相似文献
5.
渤海莱州湾表层沉积物中金属元素分布及环境质量 总被引：3，自引：1，他引：2
利用X-射线荧光光谱仪、等离子质谱仪或原子荧光光度计测定了莱州湾表层沉积物中金属元素的含量,探讨了它们的分布特征、来源及污染程度,结果表明,沉积物中铜、锌、铅、镉、砷、镍、铬、钴、钒、钪、铁、锰的含量由近岸向湾内递减,莱州湾北部海域的含量大于南部的。银含量高的沉积物主要分布在莱州湾中部偏西南的环流中心区。沉积物中砷和镍含量超过ERL值,潜在生态风险较高。富集系数和主成分分析显示,沉积物中铁、铜、锌、镉、砷、铬、镍、钴、锰、钒和钪为无富集,砷为轻度富集,铅和银为中度富集。铁、铜、锌、镉、铬、镍、钴、锰、钒、砷和钪主要来源于自然源,铅既有岩石和土壤风化产物硅酸盐矿物等自然源的贡献,又受到了人为活动的影响,银主要受人为活动的影响。聚类分析表明,可把莱州湾沉积物分为4类,其中黄河口西北缘沉积物中砷和镍污染生态风险最高,其次是莱州湾中部和北部。 相似文献
6.
The blue crab, Callinectes sapidus, is distributed along the east coast of the United States from Cape Cod, Mass., through the Gulf of Mexico, including both relatively unpolluted coastal areas and estuaries contaminated with trace metals. Cadmium is of particular concern because it is concentrated in the digestive glands of blue crabs and can be passed on to consumer organisms. Tissue concentrations and partitioning of trace metals from crabs exposed in the laboratory to 10 ppb dissolved cadmium for 40 days were compared with blue crabs collected from two locations on the Hudson River, NY, Foundry Cove and Haverstraw Bay, Foundry Cove and Haverstraw Bay, both of which have elevated trace metal levels relative to estuarine areas near Beaufort, NC. Crab digestive glands, gills and muscle were removed and analyzed for total cadmium, copper, zinc and nickel concentrations using acid digestion and atomic absorption spectrophotometry, and metal-binding (metallothionein-like) proteins were determined by gel-filtration chromatography. In crabs exposed to cadmium in the laboratory, the cytosolic partitioning was similar to previous investigations at our laboratory where higher levels of cadmium (100 ppb) and shorter exposure times (14 days) were used. The similarity in cadmium partitioning from these two separate experiments indicates dose independence. In crabs from polluted environments the digestive glands contained the highest concentrations of trace metals. Chromatograms of the cytosol from the digestive glands and gills from both field and laboratory exposed crabs showed similar distributions of cadmium, copper and zinc. The gills of both field and laboratory-exposed crabs had metal-binding proteins that contained mostly cadmium, and the digestive glands had metallothionein-like proteins that contained cadmium, copper and zinc. Estimated molecular weights for these proteins were similar to the metallothioneins found in other crustaceans and mammals. 相似文献
7.
An intercomparison study of voltammetric and atomic absorption spectrometric methods for determining cadmium, lead and copper in seawater samples was conducted. The voltammetric approach utilizes differential pulse anodic stripping voltammetry using a rotating, glassy carbon, mercury film electrode under conditions developed to minimize contamination sources and to enhance sensitivity for seawater matrices. The atomic absorption approach involves a concentration step using either an organic solvent extraction of metal dithiocarbamate chelates or a Chelex-100 column with detection by graphite furnace atomic absorption spectrometry. Similar and consistent results were obtained using both methods for the three trace metals studied on a wide range of natural seawater samples. Both methods are comparable in sensitivity for cadmium and copper, however the voltammetric method is better suited for the analysis of lead in seawater because of its enhanced sensitivity and low blank. An advantage of the voltammetric approach is its amenability towards real-time shipboard analysis. 相似文献
8.
D.J Mackey 《Marine Chemistry》1983,13(3):169-180
Metal-organic complexes were isolated from coastal seawater by adsorption onto octadecyl-bonded silica (SEP-PAK cartridges) and injected into a high-performance liquid chromatograph. Trace metals were identified in the eluate by a four-channel non-dispersive atomic fluorescence detector. Organic complexes of copper, zinc, iron, magnesium, nickel and manganese were found to be present but no complexes of chromium or cadmium were detected. The complexes covered a wide range of polarities with no specific complexes being predominant. Interference from the stainless-steel chromatograph was negligible. The technique provides a minimum estimate of the amount of metal organics and it is suggested that a significant fraction of the metal organics present are too polar to be completely retained by the SEP-PAK cartridges. Typical values of the amounts of trace metal isolated by this technique corresponded to concentrations in the original seawater of >65 ngl?1 (Cu), >27 ngl?1 (Fe) and >41 ngl?1 (Zn). 相似文献
9.
Fourteen trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn) were analyzed in livers and muscles from 22 fish species from the New Caledonia lagoon, which is subjected to important chemical inputs due to intense land-based mining activities (New Caledonia is the third largest world producer of Ni). The results of this baseline research indicated that livers generally concentrated trace elements to a greater extent than muscles. Nevertheless, the overall trace element concentrations in both tissues were barely above the levels reported in fish and thus contamination at the local scale was poorly discriminated. Although these levels were low, preliminary risk assessment from a global health standpoint suggests that As would be an element potentially leading to exposure of concern for fish consumers. Based on the trace element concentrations in livers and the fish trophic preferences, some trends have been observed among trophic groups: Ag, Cu, Fe, Hg, and Zn concentrations were generally higher in liver of fish with the highest trophic position whereas Cd concentrations were lower in these groups. The use of the leopard coral grouper Plectropomus leopardus as a resident top predator allowed determining the geographical variations in contamination levels with significant differences for six out of the fourteen elements investigated. The sampling sites influenced by anthropogenic inputs were revealed by high Ag, Cd, Cu, Hg, and Pb concentrations. Such geographic differences also applied to Zn but surprisingly not for the typical elements associated with Ni mining, i.e., Co, Cr, Mn and Ni. 相似文献
10.
This study assessed whether trace elements present at Deception Island, an active submarine volcano in the Antarctic Peninsula, show enhanced biological availability to the local marine community. Using a weak acid extraction method to dissolve organic material and leach associated but not constitutive trace elements of sediments, fifteen elements were measured from seafloor sediment, seawater particulates, and tissues of benthic (bivalves, brittlestars, sea urchins) and pelagic (demersal and pelagic fishes, krill) organisms collected in the flooded caldera. The highest element concentrations were associated with seafloor sediment, the lowest with seawater particulates and organism tissues. In the case of Ag and Se, concentrations were highest in organism tissue, indicating contamination through the food chain and biomagnification of those elements. The elements Al, Fe, Mn, Sr, Ti, and to a lesser extent Zn, were the most concentrated of the trace elements for all sample types. This indicates that the whole ecosystem of Deception Island is contaminated with trace elements from local geothermal activity, which is also reflected in the pattern of element contamination in organisms. Accordingly, element concentrations were higher in organisms collected at Deception Island compared to those from the neighboring non-active volcanic King George Island, suggesting that volcanic activity enhances bioavailability of trace elements to marine organisms. Trace element concentrations were highest in digestive tissue of organisms, suggesting that elements at Deception Island are incorporated into the marine food web mainly through a dietary route. 相似文献
11.
X射线分析显微镜(XGT-2000V, Horiba Co.,Japan,1993年制造)是一种新颖、快速的元素分析仪器,可以用来分析海藻中元素的组成特点。本研究对1997年4,5月在山东省威海市采集的22种海藻进行了研究,测定了海藻的Ⅹ射线荧光光谱(XRF),并根据Ⅹ射线特性荧光的能量分析海藻的主要元素组成。然后采用基本参数法(FP法)对每种海藻的主要元素进行了半定量分析。研究结果表明,Ⅹ射线分析显微镜可以快速观测海藻中的主要元素如钾、硫、钙、铁、锌、溴、锶等,是研究元素组成与化学种态的有效的非破坏分析手段。从Ⅹ射线荧光光谱可以看出,绿藻的特征元素是钾、钙、硫,孔石莼(Ulva pertusa)含有较多的铁元素,而浒苔则含有较多的溴元素。褐藻的特征元素除钾、钙、硫之外,还含有较多的锶元素。另外,酸藻 (Desmarestia viridis)含有大量的硫及溴元素,鼠尾藻(Sargassum thunbergii)、单条髓藻(Myelophycus simplex)及酸藻 (Desmarestia viridis)中尚含有较多的铁元素。红藻的特征是多种红藻均含有较大量的溴元素,例如波登仙菜(Ceramium kondai)、松节藻(Rhodomela confervoides)、多管藻(Polysiphonia urceolata)、石花菜(Gelidium amansii)及亮管藻(Hyalosiphonia caespitosa)。另外,珊瑚藻(Corallina pilulifera)中含有大量的钙质。 相似文献
12.
P. Bienfang E.H. De Carlo S. Christopher S. DeFelice P. Moeller 《Marine Chemistry》2009,113(3-4):164-171
The objective of this work is to characterize the concentrations of selected trace elements (V, Mn, Ni, Fe, Co, Cu, Zn, Se, As, Mo, Cd, Pb, U) in diverse nearshore (50 m), coastal (1.5 km) and seawater well environments within the Hawaiian Archipelago using robust analytical methods that are appropriate for metals analyses in seawater. The sampling sites include locations having varying type, quality and quantity of freshwater input. In most coastal and nearshore cases, the trace element concentrations approximate values characteristic of offshore waters. Concentrations of trace elements in coastal waters that were enriched through either urban or agricultural inputs declined sharply within a short distance from shore; this is taken to indicate the predominant importance of physical mixing/advective processes along with particle scavenging in these dynamic areas. Trace element levels in seawater wells did not evidence any concentration trends consistent with island age suggesting little or no impact of island weathering on metal concentrations; concentration differences among wells appeared to be more dependent on well depth, redox conditions, and/or salinity. Sampling also targeted nearshore locales where ciguatera fish poisoning is prominent because of suggested linkages between trace element concentrations and aberrant dinoflagellate growth. Nearshore stations where ciguatera is prevalent failed to show clearly different trace element levels except for two prominent locales which showed elevated Mn and Fe concentrations. 相似文献
13.
基于2010年10月国家自然科学基金委东海调查公共航次所获得的数据和悬浮体样品,使用ICP-AES、ICP-MS仪器对悬浮体中的主、微量元素含量进行了测定,对悬浮体中元素组成、空间分布及其影响因素进行了研究,结果表明:长江口及邻近海域悬浮体中主量元素铝、镁、铁、钙等含量为1%~30%,含量以铝为主;微量元素镉、铬、钴、铜、锰、镍、铅、钒等含量为n×10-6~n×10-9,以锰最高;铝与铁、锰以及大部分的微量元素都有良好的相关性,指示这些主量元素以陆源输入为主和微量元素被细颗粒物质吸附为主的特征。水团对长江口及邻近海域颗粒态地球化学组分的空间分布具有重要的影响,其中铝、铁及铬、钴、铜、锰、镍、钒等元素受水团的制约更加显著。 相似文献
14.
Ikonomopoulou MP Olszowy H Limpus C Francis R Whittier J 《Marine environmental research》2011,71(1):10-16
The blood and eggs of the flatback turtle (Natator depressus) sampled when nesting at Curtis Island, Queensland, Australia. In the blood, zinc was present at the highest concentration of 151.15 ± 1.45 μg/L followed by copper (7.74 ± 0.09 μg/L). Lead was found only in some individuals. The measured trace elements in the blood were maternally transferred into the eggs. Other metals and metalloids detected in eggs were chromium, manganese, arsenic and selenium. Eggs showed a more complex trace element profile than blood, suggesting that they provided more representative tissues for determining maternal levels of trace element accumulation in N. depressus. Intra-clutch variation was over 15% for most of the studied trace elements suggesting one egg is not in sufficient to determine trace element accumulation within a clutch. Copper was the only element which was positively correlated with breeding age. Furthermore, no detectable levels of tin compound derivates were measured in N. depressus. 相似文献
15.
To establish a base line against which future pollution may be measured, eight common commercial species of New Zealand sea fish were analysed for cadmium, chromium, copper, iron, lead, manganese, nickel, and zinc. One sample of edible muscle tissue was analysed for each of 70 samples of each species. The internal organs of up to five specimens of each species were also analysed. The fish studied were: kahawai, Arripis trutta, trevally, Caranx lutescens, tarakihi, Cheilodactylis macropterus, snapper, Chrysophrys auratus, moki, Latridopsis ciliaris, hapuku, Polyprion oxygeneios, kingfish, Seriola grandis and gurnard, Trigla kumu. Although, none of the edible parts of the fish appeared to have trace element levels likely to be a public health problem (cadmium 0.002–0.02 ppm, chromium 0.01–0.04 ppm, copper 0.04–0.95 ppm, iron 0.9–13.5 ppm, lead ‘ 0.14–0.95 ppm, manganese 0.04–2.00 ppm, nickel 0.01–0.08 ppm, zinc 2.0–36.0 ppm), some of the organs (particularly the liver) had relatively high concentrations of elements such as cadmium (up to 54 ppm). Only if some industry were to seek to exploit internal organs of fish for human consumption would such levels become important. There was some evidence for a relationship between trace element concentrations and fish size for copper in kingfish and snapper, iron in hapuku, manganese in gurnard, and for zinc in kingfish and tarakihi. Some element pairs such as copper and zinc, iron and manganese, appeared to have concentrations which were mutually related. It was assumed that the elemental concentrations reported represent natural levels and are not the result of significant man‐made pollution because there are no major industries or large urban centres adjacent to the fishing grounds. 相似文献
16.
胶州湾的生态环境演变与营养盐变化的关系 总被引：1，自引：0，他引：1
作为我国人为影响海洋研究与海洋学基础研究的典型海域,胶州湾历经90年的科学调查和研究,获得了系统的对胶州湾海洋学的认识。本文总结归纳了近年来胶州湾的生态环境变化状况、营养物质输入以及百年来生态环境演变的主要结果和结论。近年来,胶州湾海水呈现“高氮-低磷-低硅富营养化”状况较明显,浮游生物生物量有增加的趋势,输入到胶州湾营养物质的量巨大,总溶解态氮的年输入通量为6 945.4 t/a,其中无机氮、有机氮分别为4 453.1 t/a,2 492.3 t/a。点源和河流是总溶解态氮的主要输入方式,分别占无机氮输入通量的39%和20%,有机氮输入通量的31%和41%。总溶解态磷的年输入通量为160.6 t/a,其中无机磷的输入略高于有机磷,二者分别为88.0 t/a,72.6 t/a。河流和点源是无机磷的主要输入方式,分别占无机磷输入通量的40%和30%,而对于有机磷而言,河流是其主要的输入方式,可占其输入通量的51%,而地下水和点源也分别占输入通量的24%和15%,这些大量输入的营养物质对胶州湾生态环境变化起了关键作用。胶州湾百年来经历了三个阶段的演变,20世纪70年代以前,胶州湾受人为影响很小,其化学要素水平基本呈现“背景值”且比较稳定,从20世纪80年代起,胶州湾明显受到人为活动的影响,其沉积物中的化学组分持续增加,直到20世纪90年代中到2000年达到高峰,2000年后,由于环保治理措施的加强,沉积物中的化学组分呈明显降低趋势,基本稳定在较低的水平。 相似文献
17.
Hydrothermal Manganese Deposits from the Tonga-Kermadec Ridge and Lau Basin Region,Southwest Pacific
T. D. S. Rogers R. A. Hodkinson D. S. Cronan 《Marine Georesources & Geotechnology》2013,31(4):245-268
Hydrothermal Mn-oxide deposits from the Tonga-Kermadec Ridge and the Valu Fa Ridge back-arc spreading center in the Lau Basin have been studied mineralogically and by bulk and partition geochemical techniques. The Mn-oxides are present as three main morphological types; of these, a dense, grey submetallic material is most common. Common lamination of this material suggests an intermittent rate of formation. Mineralogically, the crusts comprise variable proportions of 10Å and 7Å manganite. Concentrations of some trace elements, including Li, Mo, and Zn are generally significantly higher than those observed in Mn-crusts of hydrogenous origin, suggesting that the observed trace element enrichments are due to a hydrothermal source. Both temporal and geographical controls are seen to affect these trace element concentrations. Although most of the hydrothermally enriched elements are associated with the Mn-oxide phases, Li appears to reflect either a surficial adsorption or the presence of a separate Li-rich phase. Observed variations in deposit composition could reflect differences in the geochemistry of the basement rocks from which the elements have been leached, the proximity of high-temperature sulphide deposits and temporal variability in the hydrothermal systems. 相似文献
18.
The oceanic biogeochemical cycles of many trace elements are dominated by their association with the growth, death, consumption and sinking of phytoplankton. The trace element content of marine phytoplankton reflects nutritional status, species composition, surface area to volume ratios, and interactions with bioactive and toxic elements in the ambient seawater. Despite the ecological and environmental importance of trace element assimilation by autotrophs, there are few modern measurements of trace elements in phytoplankton assemblages from the natural environment. Here we introduce a new method for collection and analysis of size-fractionated particulate samples from practical seawater volumes. We pay particular attention to accurate determination of trace element filter blanks which are typically the limiting factor for analysis of such samples. Metals were determined at very low detection limits by high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) for 11 elements (Ag, Al, Cd, Co, Cr, Cu, Fe, Mn, U, Zn and P, which is used as a biomass normalizer) in three types of polymer filters (0.45, 5.0, and 53 μm pore size) and a quartz fiber filter (0.8 μm pore size). To place these new determinations in a practical context, results are presented for a vertical profile of samples filtered from 1–4 l of coastal seawater (0.3–1.0 mg total solid dry weight) at a station off central California. The results demonstrate that the blanks of the evaluated filter types, precleaned appropriately, are sufficiently low to allow accurate determination of the trace metal content of three size-classes of phytoplankton. At the Pacific station, measured phytoplankton Zn content (as Zn/P) agrees with values predicted from single-species culture studies growing at seawater Zn concentrations expected for coastal waters. The new method has utility as a generally applicable and simple size fractionation technique, and allows determination of natural and pollutant elements in small samples of phytoplankton and particles in coastal, estuarine and offshore marine regimes. 相似文献
19.
Frequency distribution characteristics of trace elements Fe. Mn, Zn, Cu. Sr and Ba are studied for the marine organisms collected from typical Chinese coastal waters and compared with those of major elements Ca and Mg. Nearly all the distributions for trace elements in macroalgae, benthic molluscs, crustaceans, cephalopods and different tissues of fish (muscle, liver and bone ) are found to show some degree of positive skewness, indicating a relatively large number of marine organisms with low concentrations for a particular element and only a few organisms with disproportionately high concentrations. Their distribution types are generally logarithmic normal distribution or nearly logarithmic normal distribution. Distribution of Ca is similar to that of trace elements, while Mg shows normal distribution. Average elemental concentrations of major types of organisms are calculated based on their frequency distributions. 相似文献
20.
Capture fisheries and aquaculture provide a large quantity of bivalve molluscs for human consumption in Thailand each year. The existing information on trace elements in these bivalves is fragmentary and contradictory. This paper reports data for eight metals (cadmium, chromium, copper, iron, lead, nickel, mercury and zinc) in the four major species marketed. These are the clam Pahia undulata, the cockle Anadara granosa, the green mussel Perna viridis and the rock oyster Crassostrea commercialis. The bivalves analysed were taken at markets or in the field to cover as many of the major sources as possible. The results indicate no major threat to public health from trace elements in these species from Thailand and lend confidence to the expansion of aquaculture operations. In particular, the levels of lead found in the samples analysed are considerably lower than those previously reported by other authors. 相似文献