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1.
The concentration of cadmium in sexually mature Nucella lapillus was investigated around the coast of Wales. Higher concentrations of cadmium were found in whelks located in the Bristol Channel compared with Cardigan Bay Nucella. Accumulation and toxicity of cadmium were investigated at 50–600 μg Cd l−1 over a period of 21 days. At the lower concentrations of 50–100 μg Cd l−1 all Nucella survived the 21 days of experimentation. The rate of cadmium uptake after exposure to cadmium was inconsistent and not related to the degree of site contamination. At all sites the concentration of cadmium in Nucella, after treatment with 50–600 μg Cd l−1 for 21 days, was significantly different from controls, but after 7 days it varied with the site and cadmium concentration. Only samples collected at Fishguard, Dale, and Swansea survived 21 days at 600 μg Cd l−1. Tissue cadmium concentrations did not significantly effect the whole body concentration of zinc.  相似文献   

2.
The concentration of cadmium in Nucella was investigated at different times of the year at one site. There was no significant difference in tissue cadmium at the times of the year investigated but tissue zinc was more variable. Accumulation and toxicity of cadmium were studied using 50–600 μg Cd l−1 for 21 days. There was no significant seasonal difference in the rate of cadmium uptake but mortality appeared to vary with the season. Nucella did not survive 21 days at 600 μg Cd l−1, but at lower concentrations 50–100 μg Cd l−1 all survived.

Although there was significant drop in oxygen consumption between 7 and 14 days it did not appear to be related to the cadmium exposure. Glycogen levels on the other hand showed a decrease after cadmium treatment, while lipid values remained unchanged. Results are discussed in relation to energy source, season, and adaptation to the environment.  相似文献   


3.
The impact and recovery from exposure to the herbicide diuron [DCMU; 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea] was assessed for three tropical seagrasses, maintained in outdoor aquaria over a 10-day period. Photosynthetic stress was detected using chlorophyll a fluorescence, measured with a Diving-PAM (pulse amplitude modulated fluorometer). Exposure to 10 and 100 μg l−1 diuron resulted in a decline in effective quantum yield (ΔF/Fm′) within 2 h of herbicide exposure in Cymodocea serrulata, Halophila ovalis and Zostera capricorni. Effective quantum yield also declined over the first 24 h of exposure in H. ovalis at even lower diuron concentrations (0.1 and 1.0 μg l−1). Effective quantum yield in H. ovalis and Z. capricorni was significantly depressed at all diuron concentrations (0.1–100 μg l−1) after 5 days exposure, whereas effective quantum yield in C. serrulata was only significantly lower in plants exposed to highest diuron concentrations (10 and 100 μg l−1). Effective quantum yield depression was present 5 days after plants exposed to 10 and 100 μg l−1 diuron were returned to fresh seawater. These results indicate that exposure to herbicide concentrations present in nearshore Queensland sediments present a potential risk to seagrass functioning.  相似文献   

4.
Tributyltin (TBT) concentrations in waters of Poole Harbour ranged between 2–139 ng l−1 (as Sn) and increased to 234–646 ng l−1 within marinas. Seasonal trends in contamination coincided with boat usage patterns and peaked during summer months. A combination of poor tidal flushing and removal of TBT to particulates restricts high levels of contamination to areas closest to marinas and moorings; TBT concentrations in benthic sediments decreased from 0.52 μg g−1 near such sites to 0.02 μg g−1 at the harbour mouth. Organotin accumulations in several benthic invertebrates including polychaetes (Nereis diversicolor), snails (Littorina littorea) and clams (Scrobicularia plana, Mya arenaria) reflect the distribution of contamination in the environment, though concentration factors (relative to water) vary considerably between species and were highest in sediment dwelling clams, notably Mya (1.3×105). Compared to organotins, biological availability of inorganic tin is low.

Levels of TBT in parts of Poole Harbour exceed Environmental Quality Targets designed to protect marine life and may be responsible for poor recruitment, particularly in bivalves, at heavily contaminated sites.  相似文献   


5.
The main aim of this study was to assess the hydrogen peroxide (HP) production rates (HPPR) related to anthropogenic pollution in coastal waters by laboratory and field experiments. HPPR's were assessed by simultaneous measurements of HP concentrations, cumulative solar UV irradiation and dissolved organic matter (DOM) fluorescence in the seawater samples at clean and polluted sites in the Mediterranean, Red and the Baltic Seas. The natural HP concentrations at all sites (8–100 nM) fall within the normal range recorded elsewhere, and follows a diurnal pattern. The polluted stations in the Mediterranean and Baltic Seas showed higher HPPR (3.2–16.6 nM m2 W−1 h−1) than the clean stations, while in the Red Sea no significant differences were found because the station that was considered a priori polluted was actually rather clean (2–3 nM m2 W−1 h−1). Laboratory experiments demonstrated that HPPR was positively linearly correlated to DOM fluorescence, however, this relationship was not found in the natural seawater samples examined in the field. The lack of relationship between HPPR and DOM in the field was attributed to enzymatic breakdown of HP as observed in dark decay experiments. HP dark decay rates were highest in polluted stations, probably due to larger bacterioplankton populations in these samples. Moreover, the HP dark decay rates were much lower in filtered than in non-filtered samples. Sun incubation of filtered (0.2 μm) seawater samples were performed to assess whether elimination of particles would yield higher HPPRs than in non-filtered samples. In the Baltic Sea (low UV irradiation) HPPR was higher in the filtered samples, while at sites with relatively high UV irradiation (Mediterranean and Red Seas), filtration of seawater did not stimulate HPPRs, probably due to UV-damage to planktonic microorganisms.  相似文献   

6.
This study examined the effect of copper on the settlement success of planula larvae of the reef-building coral Acropora tenuis during 1994 and 1996 at Magnetic Island, Great Barrier Reef. Copper concentrations of 2, 10, 20 μg l−1 did not inhibit larval settlement after 48-h exposure. However, copper concentrations of 42 μg l−1 and 81 μg l−1 significantly reduced settlement success of A. tenuis larvae after 48-h exposure compared with controls using normal seawater. At 200 μg l−1 copper, all larvae died. EC50 values for the effect of copper on A. tenuis larval settlement were calculated from the 1996 results using measured copper concentrations. The 48-h EC50 was 35 μg l−1 with an upper and lower 95% confidence limit of 37 μg l−1 and 32 μg l−1, respectively. The 48-h NOEC value for both experiments was 20 μg l−1 copper. These experiments provide some of the first data on sub-lethal effects of trace metals on tropical marine organisms, and demonstrate that relatively low copper concentrations impair or inhibit settlement of coral larvae.  相似文献   

7.
In the present work, we built a mathematical model of polychlorinated biphenyl (PCB) bioaccumulation in Perna viridis, namely, a one-compartment model with a time dependent incorporation rate R (μg g−1 lipid per ppb water per day), with positive substrate cooperativity as the underlying physical mechanism. The temporal change of the PCB concentration Q (μg g−1 lipid) in the soft tissues of the mussel depends on the competition of the input rate RW and the output rate kQ, where W is the concentration of PCB in water (ppb water) and k is the elimination rate (per day). From our experimental data, k=0.181±0.017 d−1. The critical concentration in water Wc for positive substrate cooperativity was found to be 2.4 ppb. Below Wc, R is a constant. For a water concentration of 0.5 ppb Aroclor 1254, R=24.0±2.4 μg g−1 lipid ppb−1 d−1. Above Wc, positive substrate cooperativity comes into effect and R becomes a function of time and dependent on the concentration Q in a form R=γQ/(Q+δ). This is the case for a water concentration of 5 ppb Aroclor 1254, where γ=15.1 μg g−1 lipid ppb−1 d1 and δ≈200 μg g−1 lipid. From this model, the uptake is exponentially increasing when the PCB concentration in the mussel is small compared to 200 μg g−1 lipid, and hyperbolically increasing when the concentration is large compared to 200 μg g−1 lipid, which are consistent with the experimental data. The model is useful for understanding the true processes taking place during the bioaccumulation and for risk assessment with higher confidence. Future experimental data which challenge the present model are anticipated and in fact desirable for improvement and perfection of the model.  相似文献   

8.
Muscle tissue of chinook salmon, Oncorhyncus tshawytscha, reared for 3 to 19 months in sea pens treated with an antifouling biocide, tri-n-butyltin (TBT), contained organotin concentrations of 0.28–0.90 μg g−1 (as TBT). Organotins are present in some pen-reared salmon sold in the United States: eleven of 15 salmon advertised as aquaculture products and purchased from public markets contained organotin concentrations of 0.081–0.20 μg g−1. Most common cooking practices do not effectively destroy or remove butyltins from salmon muscle tissue. We believe this is the first evidence of entry of organotins into the human diet in the United States.  相似文献   

9.
Variations in some physical, chemical, and nutrient conditions were investigated at Turkwel Gorge Reservoir and its inflowing river, Suam between 1994 and 1995. Seasonal changes in inflow volume had the greatest impact on the reservoir and river conditions investigated. A wide fluctuation in inflow volume combined with a regulated outflow independent of season resulted in a draw down of over 10 m in each year. Flood inflows during the wet season resulted in the lowest values of Secchi depth (range, 0.09–2.16 m), electrical conductivity (EC, range = 140–200 mS cm−1) and total alkalinity (TA, range = 75–111 mg l−1) while the highest values were measured during the dry season. A functional relation between EC and TA (TA = 0.529 mg l−1, EC: R2 = 0.876) suggests a predominance of carbonates among the anions. Vertical profiles of temperature and dissolved oxygen (DO) revealed that the reservoir is monomictic with a wide variation in the depth of the daily mixed layer. High values of pH (range = 6.7–8.9) and DO (range = 4.9–9.2 mg l−1) were associated with periods of peak phytoplankton photosynthesis while the lowest values followed reservoir mixing. Peak total nitrogen (TN, range = 119–526 μg l−1) and total phosphorus (TP, range = 8.9–71.6 μg l−1) levels during the wet season resulted from increased river loading. Values of dissolved reactive silica (DRS, range = 0.41–9.77 mg l−1) showed a wet season decline which was related to diatom depletion during the wet season. Annual reservoir areal loading rates of 27.38, 10.90 and 408.5 mg m−2 were computed for TN, TP and DRS respectively based on estimates of inflowing river loads in 1994.

At the inflowing river Suam, low levels of EC (range = 107–210 μS cm−1) and TA (range = 62–125 mg l−1) occurred during the wet season while the highest levels occurred shortly before the river dried up. The first flood water at the resumption of river inflow in March was characterized by very low levels of DO (range = 1.8–8.2 mg l−1) and high levels of TN (range = 205–3354 μg l−1) and TP (102–1259 μg l−1). River pII (6.9–7.7) and DRs (range = 9.01–19.93 mg l−1) varied irregularly throughout the year.  相似文献   


10.
REE diffusion in calcite   总被引：6，自引：0，他引：6  
Chemical diffusion of four rare-earth elements (La, Nd, Dy and Yb) has been measured in natural calcite under anhydrous conditions, using rare-earth carbonate powders as the source of diffusants. Experiments were run in sealed silica capsules along with finely ground calcite to ensure stability of the single-crystal samples during diffusion anneals. Rutherford backscattering spectroscopy (RBS) was used to measure diffusion profiles. The following Arrhenius relations were obtained over the temperature range 600–850°C: DLa =2.6×10−14 exp(−147±14 kJ mol−1/RT) m2 s−1, DNd =2.4×10−14 exp(−150±13 kJ mol−1/RT) m2 s−1, DDy =2.9×10−14 exp(−145±25 kJ mol−1/RT) m2 s−1, DYb =3.9×10−12 exp(−186±23 kJ mol−1/RT) m2 s−1. In contrast to previous findings for refractory silicates (e.g. zircon), differences in transport rates among the REE are not pronounced over the range of temperature conditions investigated in this study. Diffusion of the REE is significantly slower than diffusion of the divalent cations Sr and Pb and slower than transport of Ca and C at temperatures above 650°C. Fine-scale zoning and isotopic and REE chemical signatures may be retained in calcites under many conditions if diffusion is the dominant process affecting alteration.  相似文献   

11.
Zinc in muscle tissue from 28 species of fish, three species of sharks and rays, two species of squid and cuttlefish, and three species of crustacea collected from Cleveland Bay, together with some measurements made on oysters and mangrove flora and fauna are reported. In the fish species the mean Zn concentration in muscle tissue was 4.83 ± 2.82 μg/g wet weight, slightly lower than zinc measurements (7 μg/g wet weight) made in 14 fish species collected from the bay in 1975. Zinc in sharks and rays ranged from 3.5 to 7.2 μg/g wet wt, in squid and cuttlefish 13–16 μg/g wet wt, and in crustacea levels ranged from 14 to 18 μg/g wet wt. Zinc levels in fish varied between species with concentrations well below the ANZECC Maximum Residue Limit of zinc in seafood (150 μg/g wet wt). Although lower zinc concentrations were found in oysters collected from the Townsville Harbour area (2080 μg/g wet wt), compared with previous measurements made 25 years ago at this site, these levels are still above the Maximum Residue Limit for zinc in oysters (1000 μg/g wet wt). Concentrations of zinc in oysters from Orpheus Island (2547 μg/g wet wt), about 74 km away from industrial and urban activity, are also above the safe guideline values. Horseshoe Bay oysters transplanted to Ross Creek accumulated zinc at a rate of about 100 μg/g of oyster tissue per week, suggesting that dissolved zinc levels at this site are elevated, and that oysters rapidly accumulate zinc. Highest concentrations of zinc in mangrove leaves (30–65 μg/g dry wt) occurred in Osbornia octodonta, Exocaria agalocha, and Aegialitus annulata, compared with Ceriops tagal, and Avicennia marina (5–10 μg/g dry wt). No significant difference in zinc concentration occurred between leaves and litter fall for most of these species, with the sole exception of Exocaria, which showed almost a twofold increase in concentration. In seven species of mangrove fauna levels of zinc were very uniform and close to 50 μg/g (dry wt) Telescopium telescopium from the mouth of the Ross Estuary was the exception with levels at 400 μg/g (dry wt).  相似文献   

12.
Pesticides and herbicides including organochlorine compounds have had extensive current and past application by Queensland's intensive coastal agriculture industry as well as for a wide range of domestic, public health and agricultural purposes in urban areas. The persistent nature of these types of compounds together with possible continued illegal use of banned organochlorine compounds raises the potential for continued long-term chronic exposure to plants and animals of the Great Barrier Reef. Sediment and seagrass samples were collected from 16 intertidal and 25 subtidal sampling sites between Torres Strait and Townsville, near Mackay and Gladstone, and in Hervey and Moreton Bays in 1997 and 1998 and analysed for pesticide and herbicide residues. Low levels of atrazine (0.1–0.3 μg kg−1), diuron (0.2–10.1 μg kg−1), lindane (0.08–0.19 μg kg−1), dieldrin (0.05–0.37 μg kg−1), DDT (0.05–0.26 μg kg−1), and DDE (0.05–0.26 μg kg−1) were detected in sediments and/or seagrasses. Contaminants were mainly detected in samples collected along the high rainfall, tropical coast between Townsville and Port Douglas and in Moreton Bay. Of the contaminants detected, the herbicide diuron is of most concern as the concentrations detected have some potential to impact local seagrass communities.  相似文献   

13.
S. V. Panno  W. R. Kelly   《Journal of Hydrology》2004,290(3-4):229-242
This investigation was designed to estimate the mass loading of nitrate (NO3−) and herbicides in spring water discharging from groundwater basins in an agriculturally dominated, mantled karst terrain. The loading was normalized to land use and NO3− and herbicide losses were compared to estimated losses in other agricultural areas of the Midwestern USA. Our study area consisted of two large karst springs that drain two adjoining groundwater basins (total area of 37.7 km2) in southwestern Illinois' sinkhole plain, USA. The springs and stream that they form were monitored for almost 2 years. Nitrate–nitrogen (NO3–N) concentrations at three monitoring sites were almost always above the background concentration (1.9 mg/l). NO3–N concentrations at the two springs ranged from 1.08 to 6.08 with a median concentration of 3.61 mg/l. Atrazine and alachlor concentrations ranged from <0.01 to 34 μg/l and <0.01 to 0.98 μg/l, respectively, with median concentrations of 0.48 and 0.12 μg/l, respectively. Approximately 100,000 kg/yr of NO3–N, 39 kg/yr of atrazine, and 2.8 kg/yr of alachlor were discharged from the two springs. Slightly more than half of the discharged NO3− came from background sources and most of the remainder probably came from fertilizer. This represents a 21–31% loss of fertilizer N from the groundwater basins. The pesticide losses were 3.8–5.8% of the applied atrazine, and 0.05–0.08% of the applied alachlor. The loss of atrazine adsorbed to the suspended solid fraction was about 2 kg/yr, only about 5% of the total mass of atrazine discharged from the springs.  相似文献   

14.
Located in the Yunnan–Guizhou Plateau in southwest China, Fuxian Lake covers an area of 211 km2, with maximum depth of 155 m. It is known to have a unique fauna, including 14 described endemic species. In order to describe the zoobenthic community of the lake more completely, the present study was conducted from August 2002 to August 2003. Altogether 62 benthic taxa, including 22 oligochaetes, 21 molluscs and 18 insects were identified, of which the dominant taxa belonged to Potamothrix, Procladius and Paraprososthenia. The standing stocks of benthos were much higher in the littoral (824 ind/m2 in density, 3.72 g/m2 in biomass) than in the profundal region (23 ind/m2 in density, 0.10 g/m2 in biomass). Species richness was greatest in summer and standing stocks were larger in spring and summer than in other seasons. Analyses of functional feeding groups indicated that collector-gatherers and scrapers were predominant in entire lake. Stepwise multiple regression analysis demonstrated that the water depth is the most important factor affecting the distribution of macrozoobenthos.  相似文献   

15.
We investigated the upper mantle anelastic structure beneath the northern Philippine Sea region, including the Izu-Bonin subduction zone and the Shikoku Basin. We used regional waveform data from 69 events in the Pacific and the Philippine Sea slabs, recorded on F-net and J-array network broadband stations in western Japan. Using the S–P phase pair method, we obtained differential attenuation factors, δt*, which represent the relative whole path Q. We conducted a tomographic inversion using 978 δt* values to invert for a fine-scale (50–100 km) three-dimensional anelastic structure.

The results shows two high-Q regions (QP>1000) which are consistent with the locations of the Pacific and the Philippine Sea slabs. Also there is a low-Q (QP110) area extending to the deeper parts (350–400 km) of the model just beneath the old spreading center and the Kinan Seamount Chain in the Shikoku Basin. A small depth dependence of the laterally averaged QP was found, with values of 266 (0–250 km), 301 (250–400 km), and 413 (400–500 km).  相似文献   


16.
Input and distribution of linear alkylbenzenesulphonates (LAS) in the highly stratified Krka River estuary were studied during 1990–1991. Determinations of individual LAS homologues in wastewater and estuarine waters were performed using reversed-phase high-performance liquid chromatography (HPLC) with spectrofluorimetric detection. The investigated municipal wastewaters contained LAS homologues with alkyl-chain lengths from C10 to C13 at total concentrations in the range of 285–1041 μg l−1. Total LAS input via wastewaters into ibenik Harbour, the most polluted part of the estuary, was estimated at 12.6 kg day−1. A relatively large fraction of total LAS, depending on the wastewater particle load, was found in particulate form (11–59%). Distributions of the individual homologues in dissolved and particulate fractions were rather different, the latter being significantly enriched in higher homologues (C12, C13). The LAS concentration in the estuary was quite low (0.2–23.9 μg l−1) which was caused chiefly by a strong and fast dilution process. However, characteristic vertical distribution of LAS in the estuarine water column indicated that the wastewater plume spreads almost exclusively in the upper (brackish) layer. The concentration maxima were observed in the surface microlayer and at the brackish water/seawater boundary.  相似文献   

17.
The clam Ruditapes decussatus L. was collected from Ria Formosa, Faro, southern Portugal, and exposed to a sublethal copper concentration of 0.01 mg l−1 for 20 days. Physiological measurements, respiration rates, clearance rates and absorption efficiency, were undertaken initially and after 2, 5, 9, 14 and 20 days and used to calculate Scope for Growth. Copper accumulation rate was calculated through the analysis of copper in the tissues at the same sampling times. The experiment showed two phases. Initially, copper was rapidly accumulated (1.95 μg Cu g−1 dw day−1 in the first 48 h), clearance rates declined markedly (lowest value 13.5% of control) and respiration rates increased (116% of control), resulting in a rapid decline of Scope for Growth, which showed a negative value after 5 days. In the second phase, (from day 9 on), the rate of copper uptake declined to 0.55 μg Cu g−1 day−1 and physiological responses were more stable. After 20 days, copper concentration in the tissues was 38.4 μg Cu g−1 dw (bioconcentration factor 3840). Clearance rates were 50% of control rates and respiration rates were still high, 145% of control rates. Therefore, Scope for Growth and performance of the clams was still greatly affected (ca. 23% of the control values), indicating that though animals partially recovered through detoxifying mechanisms, excess copper caused sustained impairment of physiological functions. This experiment confirms that the physiological energetics approach and the integrated Scope for Growth measurement is a sensitive methodology to detect deviations from normal performance and assess stress at environmental realistic copper concentrations.  相似文献   

18.
Germination inhibition of the marine macrophyte Phyllospora comosa was utilized as a sub-lethal end-point to assess and compare the effects of four oil dispersants and dispersed diesel fuel and crude oil combinations. Inhibition of germination by the water-soluble fraction of diesel fuel increased following the addition of each of the dispersants; the nominal 48-h EC50 concentration of diesel fuel declined from 6800 to approximately 400 μl l−1 nominal for each dispersed combination. This contrasted with crude oil, where the addition of two dispersants resulted in an enhanced germination rate and an increase in nominal EC50 concentrations from 130 μl l−1 for the undispersed crude to 4000 and 2500 μl l−1. The results indicate that, while germination inhibition of P. comosa may be enhanced by the chemical dispersal of oil, the response varies with type of both oil and oil dispersant.  相似文献   

19.
A case study on fuel oil contamination in a mangrove swamp in Hong Kong   总被引：5，自引：0，他引：5  
Tam NF  Wong TW  Wong YS 《Marine pollution bulletin》2005,51(8-12):1092-1100
Mangroves commonly found along tropical and subtropical coastlines are susceptible to oil pollution. In December 2000, around 500 1 m tall Kandelia candel saplings at the age of 3–5 years old located at the foreshore region of Sheung Pak Nai swamp, Hong Kong SAR, were found to be damaged by oil pollution. More than 80% of the saplings were either dead or washed away and leaving less than 5% healthy saplings with dense green leaves. Elevated concentrations of light n-alkanes (ranging from n-C14 to n-C20), pristane and phytane were recorded in surface sediments collected in December 2000. The ratio between light and total n-alkanes was 0.4. The total petroleum hydrocarbons (60–80 μg g−1 TPH) and unresolved complex mixtures (60–70 μg g−1 UCM) were higher than the background values of other mangrove sediments in Hong Kong, which were 40 and 20 μg g−1, respectively. In certain root zone sediments, TPH concentrations were above 1000 μg g−1. These results suggest that surface sediments in Sheung Pak Nai were contaminated by petroleum oil, most likely by illegal discharge of fuel oil which occurred between 1998 and 2002. One year later, in December 2001, unhealthy saplings had recovered and re-grown. The concentrations of TPH and UCM in sediments declined to around 40 μg g−1, pristane and phytane dropped by 80%, and the ratio of light to total n-alkanes was 0.15, suggesting that residual oil in sediments was weathered leading to a remarkable recovery of the unhealthy saplings.  相似文献   

20.
Noble gases were extracted in steps from grain size fractions of microdiamonds ( < 100 μm) from the Kokchetav Massif, Northern Kazakhstan, by pyrolysis and combustion. The concentration of 4He in the diamonds proper (liberated by combustion) shows a 1/r dependence on grain size. For grain diameters > 15 μm the concentration also decreases with the combustion step. Both results are clear evidence that 4He has been implanted into the diamonds from -decaying elements in the surrounding matrix. The saturation concentration of 4He(5.6 × 10−4 cm3 STP/g) is among the very highest observed in any terrestrial diamonds. Fission xenon from the spontaneous fission of 238U accompanies the radiogenic 4He; the 136Xef/4He ratio of (2.5 ± 0.3) × 10−9 agrees well with the production ratio of 2.3 × 10−9 expected in a reservoir where Th/U 3.3. Radiogenic 40Ar is predominantly ( > 90%) set free upon combustion; it also resides in the diamonds and appears to have been incorporated into the diamonds upon their formation.

3He, on the other hand is mainly released during pyrolysis and hence is apparently carried by ‘contaminants’. The concentration in the diamonds proper is of the order of 4 × 10−12 cm3 STP/g, with a 3He/4He ratio of 1 × 10−8. Excess 21Ne, similarly, appears to be present in contaminants as well as in diamonds proper. These two nuclides in the contaminants must have a nucleogenic origin, but it is difficult to explain their high concentrations.  相似文献   


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