Preliminary investigation of the effects of purse seine size on estimates of density and species richness of estuarine fishes

Small purse seines are well suited to sampling open water habitats in estuaries, yet little is known about how variation in their design affects estimates of density and species richness of estuarine fishes. We tested whether purse seine size (length and depth) affected estimates of density or species richness of fishes in San Dieguito Lagoon, southern California, U.S.A. Twenty-one species were captured, with the open water speciesAtherinops affinis dominating the catch. The larger net (36.4 m long × 3.6 m deep) produced higher estimates of density than the smaller net (18.2 m long × 2.4 m deep). The average number of species captured per sample was lower for the smaller net than the larger net, but species accumulation curves for the small and large nets were similar, indicating that the difference in the number of species per sample was primarily caused by the larger area sampled by the larger purse seine. Sampling with the larger purse seine was more time efficient than the smaller seine. We found small purse seines to be useful tools for sampling fishes in open water habitats in a small estuary, but we recommend that care be taken in selecting the size of a purse seine.     

Long-term declines in two apex predators,bull sharks (<Emphasis Type="Italic">Carcharhinus leucas</Emphasis>) and alligator gar (<Emphasis Type="Italic">Atractosteus spatula</Emphasis>), in Lake Pontchartrain,an oligohaline estuary in southeastern Louisiana

We analyzed historic and current fishery independent data to determine if the abundance of two apex predators, bull sharks (Carcharhinus leucas) and alligator gar (Atractosteus spatula), in Lake Pontchartrain had changed significantly over the last half century. Lake Pontchartrain is an environmentally degraded oligohaline estuary in southeastern Louisiana that has experienced considerable changes in fish assemblage composition over this interval. Using gillnet, beach seine, and trawl data collected during three time periods (1953–1955, 1977–1978, and 1996–2005), we analyzed trends in abundance forC. leucas andA. spatula using generalized linear models with a negative binomial error structure and a log link. Lake Pontchartrain data were divided into four spatial locations (northwest, northeast, southwest, southeast) since each region represents a unique combination of anthropogenic and natural influences that could affect catches. For each species and gear type, we produced log-likelihood profiles for the instantaneous rate of change in relative abundance through time. Raw catches were generally lower for both species in the later surveys.C. leucas were not captured in beach seines since the 1950s andA. spatula were rarely captured in trawls or seines since the 1970s. Likelihood profiles of changes in abundance forC. leucas andA. spatula showed very large declines in both species since 1953.C. leucas declined by 98.6% (95% CI: 73.4–99.9%) in gillnets and became functionally extirpated in beach seines with a decline of 99.9% (95% CI: 23–99.9%). Among all gears,C. leucas declined by the same rate as in gillnets. The decline inA. spatula was also large with a decrease of 98.6% (95% CI: 73.4–99.9%) in beach seines and a decline of 99.2% (95% CI: 54.8–99.9%) in trawls since 1953. Catches ofA. spatula in gillnets did not show a significant change over the study period. The continued decline of these two apex predators could seriously affect efforts to restore this degraded estuarine ecosystem.     

Comparison of breder traps and seines used to sample Marsh Nekton

Effective sampling of marsh nekton is difficult due to the organisms’ use of the marsh-edge and/or marsh surface during high tide. Quantitative sampling approaches currently used are expensive, require permanent structures, and can require a considerable number of personnel for implementation. Our purpose was to assess the use of Breder traps (T) as a sampling method capable of documenting relative abundance of nekton. We sampled marsh habitats (within 1 m of marsh grass) in five bayous using seines at high (HS) and low (LS) tide and compared them with rank abundance and similarity data. Seining (n=3/tidal stage) was conducted adjacent to each set of traps (n=4) which were retrieved at low tide. Four transient (Engraulidae, 34.7%; Penaeidae, 12.4%; Portunidae, 6.8%; and Sciaenidae, 1.2%) and four resident families (Palaemonidae, 28.1% Fundulidae, 9.2%; Atherinidae, 3.2%; and Gobiidae, 1.1%) met our requirements (≥1% of all nekton captured) for analysis and accounted for 96.6% of the total nekton captured. High seine and LS collections were most similar (Jaccard's index, 0.58), followed by T and LS (0.46) and HS and T (0.37). Transient families were captured in greatest numbers and higher rank with seines (LS>HS>T) while two resident families (Palaemonidae and Fundulidae) dominated T collections (T>LS>HS). Our data suggests that Breder traps adequately sample resident nekton which use the marsh surface and should be considered in future studies which require only CPUE estimates of abundance.     

Experimental evaluation of biases associated with sampling estuarine fishes with seines

Beach seines are widely used to estimate the density and species richness of fishes in estuaries. We evaluated the causes and extent of bias in estimates from seines using a series of field experiments in small estuaries in southern California, USA. Seining in spatially paired areas that were either enclosed by block nets or not, revealed that seines used without block nets und erestimated density by more than 4-fold and species richness by more than 2-fold relative to blocked areas. Seining in paired blocked areas with seines of two lengths revealed that net length affected estimates of density, but not species richness; a 7.6-m long seine produced 1.6-fold higher estimates of total density than did a 15.2-m long seine due to increased catches of demersal fishes, but not midwater species. Paired sampling in blocked areas also revealed that many fishes initially evaded capture by the seine. Estimates of density but not species richness were significantly higher in areas through which a seine was swept 5 times compared to once. This was due to higher catches of demersal fishes but not midwater fishes in areas seined 5 times. Repeated seining through blocked areas revealed that the vast majority (90% or more) of species and individuals of midwater fishes were captured within the first 5 sweeps, compared to only about 50% of the individuals of demersal species. A mark-recapture study in blocked areas revealed lower probabilities of capture for demersal species relative to midwater species.     

A comparison of fish assemblages and fisheries in intermittently open and permanently open coastal lagoons on the south coast of New South Wales,South-Eastern Australia

The fish assemblages inhabiting two intermittently open coastal lagoons and one permanently open coastal lagoon on the mid south coast of New South Wales were studied over several years during the mid to late 1980s. Fish were sampled either monthly or bimonthly using rotenone ichthyocide and beam trawls (in shallow vegetated habitats), beach seines (in shallow inshore sand habitats), and multiple-panel gill nets (in deep lagoon habitats with mud or sand floors). These fish assemblages were compared and contrasted spatially according to habitat both within lagoons and between the two lagoon types using a multivariate ordination technique. In the permanently open lagoon, Lake Conjola, dominant faunal elements of commercial or recreational fisheries importance included Girellidae, Clupeidae, Monacanthidae, Pomatomidae, Mugilidae, Sparidae, Sillaginidae, Gerreidae, Terapontidae, and Platycephalidae. Dominant faunal elements of no commercial or recreational fisheries importance here included Ambassidae, Scorpaenidae, Gobiidae, Atherinidae, and Eleotridae. In the intermittently open lagoons, Swan Lake and Lake Wollumboola, the dominant faunal elements included Sparidae, Mugilidae, Girellidae, Hemiramphidae, Pomatomidae, and Arripidae amongst the commercial group; and Atherinidae, Syngnathidae, Gobiidae, Eleotridae, and Scorpaenidae amongst the noncommercial group. The overall species richness of the permanently open lagoon (≈100 species, including 52 commercial species) was found to be approximately 2.5 times that of each of the two intermittently open lagoons (39 species, including 22 commercial species for Swan Lake; and 41 species, including 26 commercial species for Lake Wollumboola). The dominant faunal elements of the latter two south-eastern Australian intermittently open lagoons were also compared with those of similar lagoons in south-western Australia, southern Africa, and western Mexico, and the faunal similarities at the species, genus, and family levels are discussed. Available commercial and recreational fisheries catch data for the three south-eastern Australian coastal lagoons were also analyzed and compared. The two intermittently open lagoons were found to support number of species in the latter and also its greater water surface area.     

Suitability of fish scales as archives of temporal variations in ambient mercury levels in estuaries

To examine the suitability of fish scales as a historical archive, of environmental mercury (Hg) contamination, we analyzed a collection of scales taken from striped bass (Morone saxatilis) captured in the St. Lawrence Estuary between 1994 and 1962. The total mass of Hg in individual scales increases linearly with the weight of the scale, suggesting that Hg is well preserved in the scale tissue. Age, length, and sex of specimens captured during the same year did not significantly influence the concentration of Hg in the scales. The average Hg concentrations in scales of specimens captured in 1956 (53.2 ±9.1 ng g⁻¹) and 1962 (58.6±7.7 ng g⁻¹) are nearly twice as high as in scales from 1951 (30.2±3.0 ng g⁻¹). These results follow the trend revealed in sediment cores from the St. Lawrence Estuary. A high level of Hg in scales from 1945 (68.7±18.4 ng g⁻¹) could have been caused by an episode of Hg contamination around 1945 not recorded in the sediment or by a diet-related change in Hg exposure.     

Crystal-poor, multiply saturated rhyolites (obsidians) from the Cascade and Mexican arcs: evidence of degassing-induced crystallization of phenocrysts

A detailed petrological study is presented for six phenocryst-poor obsidian samples (73–75 wt% SiO₂) erupted as small volume, monogenetic domes in the Mexican and Cascade arcs. Despite low phenocryst (+microphenocryst) abundances (2–6 %), these rhyolites are each multiply saturated with five to eight mineral phases (plagioclase + orthopyroxene + titanomagnetite + ilmenite + apatite ± zircon ± hornblende ± clinopyroxene ± sanidine ± pyrrhotite). Plagioclase and orthopyroxene phenocrysts (identified using phase-equilibrium constraints) span ≤30 mol % An and ≤15 % Mg#, respectively. Eruptive temperatures (±1σ), on the basis of Fe–Ti two oxide thermometry, range from 779 (±25) to 940 (±18) °C. Oxygen fugacities (±1σ) range from ?0.4 to 1.4 (±0.1) log units relative to those along the Ni–NiO buffer. With temperature known, the plagioclase-liquid hygrometer was applied; maximum water concentrations calculated for the most calcic plagioclase phenocryst in each sample range from 2.6 to 6.5 wt%. This requires that the rhyolites were fluid-saturated at depths ≥2–7 km. It is proposed that the wide compositional range in plagioclase and orthopyroxene phenocrysts, despite their low abundance, can be attributed to changing melt water concentrations owing to degassing during magma ascent. Phase-equilibrium experiments from the literature show that higher dissolved water concentrations lead to more Fe-rich orthopyroxene, as well as more calcic plagioclase. Loss of dissolved water leads to a progressive increase in melt viscosity, and phenocrysts often display diffusion-limited growth textures (e.g., dendritic and vermiform), consistent with large undercoolings caused by degassing. A kinetic barrier to microlite crystallization occurred at viscosities from 4.5 to 5.0 log₁₀ Pa s for these rhyolites, presumably because the rate at which melt viscosity changed was high owing to rapid loss of dissolved water during magma ascent.     

Secondary Ion Mass Spectrometry Bias on Isotope Ratios in Dolomite–Ankerite,Part I: δ18O Matrix Effects

We document the development of a suite of carbonate mineral reference materials for calibrating SIMS determinations of δ¹⁸O in samples with compositions along the dolomite–ankerite solid solution series [CaMg(CO₃)₂–CaFe(CO₃)₂]. Under routine operating conditions for the analysis of carbonates for δ¹⁸O with a CAMECA IMS 1280 instrument (at WiscSIMS, University of Wisconsin‐Madison), the magnitude of instrumental bias along the dolomite–ankerite series decreased exponentially by ~ 10‰ with increasing Fe content in the dolomite structure, but appeared insensitive to minor Mn substitution [< 2.6 mol% Mn/(Ca+Mg+Fe+Mn)]. The compositional dependence of bias (i.e., the sample matrix effect) was calibrated using the Hill equation, which relates bias to the Fe# of dolomite–ankerite [i.e., molar Fe/(Mg+Fe)] for thirteen reference materials (Fe# = 0.004–0.789); for calibrations employing either 10 or 3 μm diameter spot size measurements, this yielded residual values ≤ 0.3–0.4‰ relative to CRM NBS 19 for most reference materials in the suite. Analytical precision was ± 0.3‰ (2s, standard deviations) for 10‐μm spots and ± 0.7‰ (2s) for 3‐μm spots, based on the spot‐to‐spot repeatability of a drift monitor material that ‘bracketed’ each set of ten sample‐spot analyses. Analytical uncertainty for individual sample analyses was approximated by a combination of precision and calibration residual values (propagated in quadrature), suggesting an uncertainty of ± 0.5‰ (2s) for 10‐μm spots and ± 1‰ (2s) for 3‐μm spots.     

Isotope Dilution Determinations of Lu,Hf, Zr,Ta and W,and Hf Isotope Compositions of NIST SRM 610 and 612 Glass Wafers

Isotope dilution determinations of Lu, Hf, Zr, Ta and W are reported for nine test portions (five for W) of NIST SRM 610 and 612 glass wafers. Additionally, all test portions were analysed for their Hf isotope compositions. In general, high field strength elemental (HFSE) distributions in NIST SRM 610 and 612 were reproducible to ～± 1%, except for Zr (± 5%) in NIST SRM 612, and absolute reported concentrations agreed with previously published values, but with higher precision. The slightly worse reproducibility of Zr in NIST SRM 612 compared to other HFSE is interpreted to result from analytical scatter, rather than sample inhomogeneity. The analyses demonstrated elemental homogeneity for both glass wafers for samples of 1–2 mg with respect to the precision of the method, i.e., ± 1% or better. Average Hf isotope compositions for both glass wafers agreed within uncertainty and the weighted average of all determinations yielded a mean ¹⁷⁶Hf/¹⁷⁷Hf ratio of 0.282111 ± 0.000009 (95% confidence level). However, although mean values for NIST SRM 610 and 612 agreed within analytical limits, NIST SRM 610 test portions showed a tendency of systematically elevated isotope composition of ～ 0.5 _?Hf units when compared to NIST SRM 612, which may indicate a slightly more radiogenic Hf isotope composition of NIST SRM 610. The results of this study suggest that NIST SRM 610 and 612 are valuable calibrators for HFSE in situ analyses within the given uncertainties.     

The robustness of the Zr-in-rutile and Ti-in-zircon thermometers during high-temperature metamorphism (Ivrea-Verbano Zone, northern Italy)

This study investigates the behaviour of the Zr-in-rutile and Ti-in-zircon thermometers in granulite facies metapelites from the Ivrea-Verbano Zone lower crustal section. U–Pb ages of zircon constrain the timing of regional amphibolite–granulite facies metamorphism to 316 ± 3 Ma and record zircon recrystallisation and resetting of U–Pb ages at 276 ± 4 Ma and 258 ± 3 Ma. Zr-in-rutile thermometry records peak contact metamorphic temperatures related to intrusion of mafic magmatic rocks and gives peak temperatures between 900–930 °C and 1,000–1,020 °C that are consistent with the geological settings of the samples. Ti-in-zircon temperatures of 700–800 °C and 810–870 °C record growth or re-equilibration of zircon after cooling from peak temperatures. Ti-in-quartz thermometry for one sample records both peak and retrograde temperatures. Some rutiles in all samples record resetting of Zr-in-rutile temperatures at ~750–800 °C. Electron microprobe profiles across individual rutiles demonstrate that Zr expulsion occurred by recrystallisation rather than by diffusive exchange. Exsolution of small needles of baddelyite or zircon from rutile is an important method of Zr redistribution, but results in no net Zr loss from the grain. The demonstration that Zr-in-rutile thermometry can robustly record peak temperatures that are not recorded by any other thermometer emphasises the relevance of this technique to investigating the evolution of high-grade metamorphic terranes, such as those that characterise the lower crust.     

Setting seagrass depth, coverage, and light targets for the Indian River Lagoon system, Florida

Seagrass protection and restoration in Florida’s Indian River Lagoon system (IRLS) is a mutual goal of state and federal programs. These programs require, the establishment of management targets indicative of seagrass recovery and health. We used three metrics related to seagrass distribution: areal coverage, depth limit, and light requirement. In order to account for the IRLS’s spatial heterogeneity and temporal variability, we developed coverage and depth limit targets for each of its 19 segments. Our method consisted of two steps: mapping the union of seagrass coverages from all availabe mapping years (1943, 1986, 1989, 1992, 1994, 1996, and 1999) to delineate wherever seagrass had been mapped and determining the distribution of depth limits based on 5,615 depth measurements collected on or very near the deep-edge boundary of the union coverage. The frequency distribution of depth limits derived from the union coverage, along with the median (50th percentile) and maximum (95th percentile) depth limits, serve as the seagrass depth targets for each segment. The median and maximum depth targets for the IRLS vary among segments from 0.8 to 1.8 and 1.2 to 2.8 m, respectively.Halodule wrightii is typically the dominant seagrass species at the deep-edge of IRLS grass beds. We set light requirement targets by using a 10-yr record of light data (1990–1999) and the union coverage depth limit distributions from the most temporally stable seagrass segments. The average annual light requirement, based on the medians of the depth limit distributions, is 33 ± 17% of the subsurface light. The minimum annual light requirement, based on of the 95th percentile of the depth distributions, is 20 ± 14%; the minimum growing season light requirement (March to mid September) is essentially the same (20 ± 13%). Variation in depth limits and light requirements, is probably due to factors other than light that influence the depth limit of seagrasses (e.g., competition, physical disturbance). The methods used in this study are robust when applied to large or long-term data sets and can be applied to other estuaries where grass beds are routinely monitored and mapped.     

Accretion and canal impacts in a rapidly subsiding wetland. III. A new soil horizon marker method for measuring recent accretion

A new methodology used on a large scale is reported by which short-term (≤1 yr) marsh accretion rates were measured in saltwater and brackish marshes and compared to first-time measurements made in freshwater marshes. The stable rare-earth elements (REE) dysprosium and samarium were used for soil horizon markers that were collected by a cryogenic field coring method and detected by instrumental neutron activation analysis (INAA). Accumulation in saltwater marshes for 6 months was estimated to be 0.76±0.26 cm (n=11) and accumulation for 1 year was 1.29±0.49 cm (n=7). Accumulation in brackish marshes for 6 months was 0.51±0.34 cm (n=6) and for 1 year, 0.84±0.32 cm (n=10). These data from saline and brackish environments can be compared to first-time measurements of accumulation in a freshwater marsh of 1.53±0.66 cm (n=8) for 6-month accumulation and 2.97±0.92 cm (n=11) for 1-year accumulation. The cryogenic REE-INAA method for sampling and measuring 6-month and 1-year accretion is nonpolluting, does not alter natural marsh soil processes, and is effective in salt, brackish, and freshwater marshes. Additionally, the marker is essentially immobile, long lasting in the soil profile, and inexpensive to buy, apply, and sample. INAA analysis of the cores is expensive and time-consuming, yet the REE-INAA method yields accretion data, especially in freshwater habitats, that are obtainable in no other way. A comparison between short-term accretion and the presence or absence of man-made canals showed no statistically significant differences of accretion along transects from 0- to 50-m distance into brackish and saltwater marshes (no freshwater transects were established). Sediment depositions measured at 50 m into fresh, brackish, and saltwater marshes from natural or man-made waterways showed no statistically significant differences of accretion within each habitat over a 6-month or a 1-year time period.     

The application of ICP-MS methods to tephrochronological problems

The accurate recognition of tephra deposits is of great value to Earth scientists because they facilitate stratigraphic correlation. The most useful tephra deposits form from violent volcanic eruptions; they are isochronous and widespread. Most are dacitic and rhyolitic in composition, and can be difficult to identify unequivocally using major element chemistry alone. Distal tephras are typically thin and are prone to contamination and thus are awkward to analyse by bulk methods. Here, the authors review their previous work in the development of analytical techniques for the analysis of small volumes of glass separates from tephra deposits, both by solution nebulisation and by laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS), placing particular emphasis on the precision and accuracy of the various methods. In solution nebulisation ICP-MS, accurate data can be obtained from samples as small as 0.025 g. LA-ICP-MS methods are described for the analysis of small bulk samples and single glass shards as small as 40 μm in diameter. Accurate and reproducible analyses can be achieved by ICP-MS by both solution and laser ablation methods on homogeneous materials. Solution analyses are normally accurate to ±5% and have typical precisions (1 σ) of around ±4% for abundant trace elements (e.g. Zr, Rb) but this can deteriorate to about ±20% for rare elements in small samples (e.g. HREE in a 25 mg sample). Laser ablation methods are slightly less accurate (typically ±5–10%) and precision decreases from about ±3% at concentrations of a few hundred ppm, to about ±10% at 1 ppm and about ±30% at 0.05 ppm. An apparent lack of precision in the bulk analysis of small volumes of glass shards by LA-ICP-MS often represents within sample heterogeneity (and not analytical error), inter-shard variation becoming abundantly clear in some tephra deposits when individual glass shards are analysed. Single grain analysis on shards as small as 40 μm can provide an accurate analysis of the pure glass phase, which may not be achieved in solution or bulk sample LA-ICP-MS methods. Analyses affected by micro-phenocryst phases, such as feldspar or zircon can be easily removed following careful inspection of the data. Single shard LA-ICP-MS also allows any compositional variation within the parental magma to be defined.     

Recommended Values of 239Pu, 240Pu and 239+240Pu Concentrations in Reference Material IAEA-315 (Marine Sediment) Estimated by Thermal Ionisation Mass Spectrometry, Inductively Coupled Plasma-Mass Spectrometry and Alpha Spectrometry

The recommended concentrations of ²³⁹Pu, ²⁴⁰Pu and ^239+240Pu in reference material IAEA‐315 (marine sediment) were estimated by three analytical methods: isotope dilution thermal ionisation mass spectrometry (TIMS), isotope dilution inductively coupled plasma‐mass spectrometry (ICP‐MS) and alpha spectrometry. The determination of ²³⁹Pu and ²⁴⁰Pu (^239+240Pu by alpha spectrometry) was carried out with samples from randomly selected bottles using each method. Plutonium‐238 was also measured by alpha spectrometry. A plutonium‐242 reference material was used as a spike for the quantitative analysis. The influence of ²⁴²Pu in the samples was therefore calculated; however, this contribution was less than the range of uncertainty and did not influence the final results. The obtained data were statistically analysed using variance component analysis and paired comparison. The combined standard uncertainties from “method/measurement”, “bottle” and “sub‐sample” were in the order of 3 to 6%. The main contributions to the uncertainty were from the material heterogeneity and from systematic differences between methods. Based on this study with twenty‐seven analyses using 10–14 g sample mass, concentrations of (38 ± 3) Bq kg^?1, (28 ± 3) Bq kg^?1 and (66 ± 4) Bq kg^?1 are proposed as recommended values for ²³⁹Pu, ²⁴⁰Pu and ^239+240Pu, respectively, and (9.5 ± 0.4) Bq kg^?1 for ²³⁸Pu as an information value in reference material IAEA‐315. In mass concentration units, these amount to (16.4 ± 1.2) ng kg^?1, (3.3 ± 0.4) ng kg^?1 and (0.015 ± 0.003) ng kg^?1 for ²³⁹Pu, ²⁴⁰Pu and ²³⁸Pu, respectively. The certified reference materials NIST 4350B and NIST 4354 were also analysed by TIMS for quality assurance of the method used in this study.     

Leachability of radium-226 from industrial phosphogypsum waste using some simulated natural environmental solutions

This study investigated the leaching of radium-226 from phosphogypsum (PG) waste produced from the fertilizer industry by synthetic solutions that replicate water that may contact the waste in natural conditions. The results indicated that the activity concentration of Ra-226 in the PG was 461 ± 12 Bq kg^?1 and compared with other studies carried out worldwide. The leached percentage of Ra-226 represents the exchangeable fraction loosely bounded in the matrix of the PG waste. The leached fraction of Ra-226 was 6.5 ± 0.6 and 9.0 ± 0.5% when the waste was exposed to rainwater and saline solution, respectively. It is also found that the leaching fraction increased 10–12 ± 0.4% when the waste was exposed to the admixture of saline solution containing Sr²⁺ or Ba²⁺ cations, whereas it was lowered to 4–5 ± 0.5% in the presence of carbonate or sulfate anions. When the PG is used as an economic fertilizer, the irrigation water can leach 7.8 ± 0.6% of Ra-226 that could contribute to plant uptake, thereby to animal and/or human consumption. The primary tests of the drinking water (well and tap resources) consumed by the populations surround the PG facility showed that the activity concentration of Ra-226 was below the minimum detectable activity.     

Desorption of tetracycline from montmorillonite by aluminum,calcium, and sodium: an indication of intercalation stability

As the uptake of cationic drugs, such as tetracycline (TC), was attributed to cation exchange, the stability of adsorbed TC on a Ca-montmorillonite SAz-2 was studied using cationic solutions of different valence charges under different pH conditions. At the initial loading of 356 mg g^?1, the amounts of TC desorbed by 0.05 M AlCl₃, CaCl₂, and NaCl were 133 ± 4, 83 ± 6, and 50 ± 4 mg g^?1, respectively, or 37, 23, and 14 %. However, when the amount or percentage of TC desorbed was normalized to the equivalence of each cation, the values were in the range of 44–50 mg g^?1 or 11–14 % per 10 mmol of charge. The kinetics of TC desorption were moderately fast and almost reached equilibrium in 6 h. The results followed the pseudo-second-order kinetic model with reaction rate in the order of AlCl₃ > CaCl₂ > NaCl at a higher initial TC loading level. The total amount of TC desorbed after five desorption cycles followed the order of AlCl₃ > CaCl₂ > NaCl, too, suggesting that cations with higher positive charges, thus, less hydrated, are preferred to remove adsorbed cationic drugs. The FTIR analyses showed larger band shift when Al³⁺ was used as the desorbing reagent. The XRD patterns before and after TC desorption revealed no changes in basal spacing, even after five desorption cycles, suggesting that the removal of TC from SAz-2 was largely from the external surfaces.     

Carius管直接蒸馏快速分离锇方法的改进

蒸馏法是Re-Os同位素测量体系从基质中分离Os的一种快捷方法,但装置繁琐,清洗工作量大,已成为限制其应用的瓶颈。文章对Carius管传统蒸馏装置进行了改进,利用橡胶滴头代替硅胶管和玻璃堵头自制Carius管直接蒸馏接口装置,简化了气体进出口管路,使用电蒸笼代替电热套,对蒸馏时间、样品溶液稀释倍数和吸收液体积等蒸馏条件进行了优化。改进后的装置升温速度、稳定性和简便性得到提高,简化了实验器皿,有利于降低空白,实现在较小操作空间内大批量样品的同时处理。Carius管直接蒸馏实验结果表明,Os的回收率可达86.7%～95.2%。在长时间(2 h)蒸馏条件下,Os回收率比传统蒸馏瓶法高约41%。针对不同样品类型和测试仪器,可选择相应的蒸馏条件,有效压缩了样品处理时间,提高了测量计数。对Re-Os定年标准物质GBW 04436(JDC)测定5次的模式年龄为(139.5±1.9)Ma～(142.0±2.1)Ma,标准物质GBW 04435(HLP)测定2次的模式年龄为(220±3.3)Ma～(223.0±3.2)Ma,分别与标准值(139.6±3.8)Ma和(221.4±5.6)Ma在不确定度范围内一致。改进后的Carius管直接蒸馏装置已应用于日常样品处理。     

郑州邙山马兰黄土的光释光(OSL)测年初步研究

对郑州市西北邙山黄土塬赵下峪(34°58'N,113°22'E)剖面上部马兰黄土(厚约87m)不同层位的24个样品作了细颗粒(4-11μm)组分红外释光(IRSL)测年,其中8个样品同时进行了细颗粒组分绿光释光(GLSL)测年。样品的IRSL和GLSL信号强度都在Daybreak1100TL/OSL检测系统中测量。该系统的本底计数为70-80光子/秒。被检测的IRSL和GLSL波长分别为340-480nm和340±25nm;激发光束波长分别为880±80nm和514±14nm,功率为18mW和15-16mW。所有样品的等效剂量都用再生释光法测定;环境剂量率是通过测定样品的铀、钍和钾含量,按Aitken(1985)的转换系数确定的,考虑了含水量的影响及宇宙射线的贡献。从这批样品的光释光测年结果可得以下初步认识:
(1)8个样品细颗粒组分的IRSL和GLSL测定的等效剂量和年龄值,除1个样品外,都在1-2σ范围内一致。这可能提供了沉积物光释光测年可靠性的一种自检方法。(2)邙山剖面马兰黄土不同层位段的沉积速率变化十分显著,从0.4m/ka到5.6m/ka,并与剖面上质量磁化率测定值的变化大致相吻合。该剖面马兰黄土至少有4个快速堆积层(沉积速率>3m/ka),其磁化率低而变化小;3个缓慢堆积层(沉积速率<0.5m/ka),其磁化率大或变化显著,它们之间有一系列过渡层。(3)邙山马兰黄土大体可三分即上部(L_1-1)埋深2.7-27.5m,中部(L_1-2)埋深27.5-57.9m)和下部(L_1-3)埋深57.9-87.9m。它们的形成年代分别为10.8-36.2ka B P,36.2-70.3ka B P和70.3-80.2ka B P。较详细的黄土-古土壤序列年代表将在文中讨论      

Isotopic variability of organic carbon in a phytoplankton-based,temperate estuary

An isotopic survey was made of organic carbon in phytoplankton, sediments, Zooplankton, larval fish, and benthic fauna from Narragansett Bay and the Marine Ecosystems Research Laboratory, Rhode Island; the results quantify the extent of variability in a phytoplankton-based ecosystem and elucidate some of its causes. Carbon from primary producers (phytoplankton) varied with taxon and size, ranging from ?20.3 ± 0.6%. (mean ± 1 s.d.) for diatoms (primarily Skeletonema costatum) to ?22.2 ± 0.6%. for nanoplankton (primarily microflagellates and non-motile ultraplankton). Planktonic isotope ratios varied little with either water temperature (0 to 20°C) or degree of preservation (up to 2-year aerobic diagenesis in sea water). Isotopically, sediments from East and West Passages of the bay were homogeneous with location and depth, with a mean (?21.8 ± 0.6%.) similar to a mixture of carbon from diatoms and nanoplankton. Providence River sediments reflected terrigenous and anthropogenic carbon (sewage) in their isotopic ratios (?24.2 ± 0.7%.). Ratios of macrozooplankton (> 150 μm) were statistically separable from those of concurrently collected phytoplankton, being, on average, 0.5 to 0.6%. more positive. Secondary consumers in the water column (shrimp and larval fish) were 2.4%. heavier than diatoms. Thirty-four taxa of benthic fauna had relatively positive isotope ratios (?18.1 ± 1.5%.) which may indicate preferential use of carbon originally from diatoms rather than nanoplankton. The wide range of benthic ratios (?22.7 to ?14.9%.) resulted from both intraspecific variability (mean range = 3%.) and the variety of trophic positions occupied. Some of the intraspecific variability could be related to size. Among species, the isotope ratios increased from meiofauna (?19.5 ± 0.4%.) to macrofaunal non-carnivores (?18.6 ± 1.3%.) and carnivores (?16.6 ± 0.8%.).     

Finfish utilization of man-initiated and adjacent natural creeks of South Creek estuary,North Carolina using multiple gear types

Three gear types were used to collect finfish species from several tributaries of the South Creek estuary near Aurora, North Carolina, to ascertain whether a man-initiated marsh and creek system resembled adjacent natural areas in finfish species composition and abundance. Project Area II was the man-initiated area constructed in 1983 as up-front mitigation by North Carolina Phosphate Corporation prior to its anticipated mining in the headwaters of nearby natural wetlands. Two creeks served as controls throughout the study: Drinkwater Creek and Jacks Creek. Otter trawls were used monthly from July 1984 through December 1988. Wegener rings were used in April, July, and October from 1984 through 1987. An experimental gill net was used monthly from June 1984 through 1985. A total of 48 finfish species was captured during the study; only 14 species (29.2%) were common among gear types. The species collected were mud sunfish, blueback herring, alewife American shad, striped anchovy, bay anchovy, inland silverside, American eel, silver perch, Atlantic menhaden, crevalle jack, common carp, spotted seatrout, weakfish, sheepshead minnow, gizzard shad, ladyfish, chain pickerel, banded killifish, mummichog, striped killifish, rainwater killifish, mosquitofish, naked goby, green goby, white catfish, brown bull-head, pinfish, longnose gar, green sunfish, pumpkinseed, bluegill, redear sunfish, spot, Atlantic croaker, largemouth bass, white perch, striped bass, striped mullet, white mullet, golden shiner, summer flounder, southern flounder, yellow perch, bluefish, Atlantic needlefish, hogchoker, andTilapia species. Abundance of finfish species was a function of gear type. Bay anchovy and spot represented about 85% of all fish in trawl samples. The remainder was comprised of 27 other species. In Wegener rings, five species—bay anchovy, menhaden, rainwater killifish, spot, and inland silverside—each represented over 10% of all fish collected. Croaker and striped mullet each comprised more than 5% of all fish collected in Wegener rings, but were present in substantial numbers only in 1985. Based on trawl samples, the total number of finfish collected from Project Area II during the period 1984–1988 was statistically similar to those collected from the control creeks; Wegener ring data analysis indicated significantly greater catches in Project Area II compared to the control creeks. Bay anchovy catches were not significantly different among the three creeks by either trawl or Wegener ring. The same result was true for Atlantic menhaden and southern flounder. The abundance of spot in trawl samples from Project Area II was significantly greater than for the control creeks; abundance in ring samples from Project Area II was statistically similar to Jacks Creek, but significantly higher than Drinkwater Creek. The number of Atlantic croaker in Project Area II trawl samples was significantly lower than for the cotnrol creeks. Wegener rings did not sample croaker effectively.