湖南市场和污染区稻米中As、Pb、Cd污染及其健康风险评价

为了更好地了解和评价湖南大米中As、Pb和Cd含量及其对人体的健康影响,在对湖南矿区和冶炼区水稻土壤重金属污染调查的基础上,分别以湖南各地市场大米和污染区当地生产的稻谷样品为例,对其进行重金属含量分析及对人体的健康风险评价.结果表明,湖南各地市场大米样品中As、Pb和Cd的平均含量分别是0.20、0.20和0.28mg·kg-1,其中,衡阳市场大米中的As、Pb和Cd含量最高,其次是株洲和湘潭市场的大米.污染区稻谷中As、Pb和Cd含量分布均为:谷壳糙米精米,污染区精米中As、Pb和Cd的含量分别是0.24、0.21和0.65mg·kg-1,其中,来自衡阳常宁市水口山铅/锌矿区的稻谷样品中的As、Pb和Cd含量最高,其次是株洲清水塘冶炼区和湘潭锰矿区的稻谷.与市场大米样品相比,污染区精米中As、Pb和Cd的平均含量比市场大米样品高.无论是市场大米样品,还是从污染区稻田采集的稻米,均以衡阳地区稻米中的As、Pb和Cd污染最为严重,其次为株洲和湘潭地区.在As、Pb和Cd的健康风险评价中,Cd是湖南各地稻米中影响人体健康的主要因子,株洲和湘潭的Cd污染区达到90%以上,其次是As和Pb.     

Graded recruitment in a ponerine ant

Summary (1) The giant tropical ant, Paraponera clavata, exhibits graded recruitment responses, depending on the type, quantity, and quality of a food source. More ants are initially recruited to a large prey or scavenge item than to a large quantity of sugar water. (2) Individual ants encountering prey items gauge the size and/or unwieldiness of the item, regardless of the weight, when determining whether to recruit. (3) The trail pheromone of this species is often used as an orientation device by individual ants, independent of recruitment of nestmates. (4) It is proposed that the foraging behavior of P. clavata represents one of the evolutionary transitions from the independent foraging activities of the primitive ants to the highly coordinated cooperative foraging activities of many higher ants.     

Feeding rates and diel vertical migration of copepods near South Georgia: comparison of shelf and oceanic sites

Seventeen Longhurst Hardy Plankton Recorder profiles were taken over a diel cycle in January 1990 to study the feeding of four major copepods over the South Georgia shelf. Ontogenetic changes in vertical migration were followed and feeding cycles determined by gut fluorometry for Calanoides acutus Stage CV, Calanus sinillimus CV and CVI, C. propinquus CV and Rhincalanus gigas CV and CVI. In common with a neighbouring oceanic site visited two weeks later and reported elsewhere, all four species had a diel cycle of feeding and migration. The vertical distributions of C. simillimus (all stages), R. gigas (nauplii) and Euphausia frigida (postlarvae) were similar at both sites, the night being spent within the chlorophyll maximum at 15 to 30 m. However, the biomass dominants, C. acutus and R. gigas, dwelt below the chlorophyll maximum, about 30 m deeper than their oceanic counterparts. Unlike the oceanic site, feeding at the shelf site was not restricted to darkness, but increased 6 to 10 h before nightfall and finished at dawn; the intervening period coincided with sinking and digestion. Daylight feeding may have been induced by the shorter night, lower light levels or greater food requirements at the shelf site, despite planktonic predators being over three times more abundant. Daily ration estimates for R. gigas at both sites were only 2% body carbon per day. These low values contrast with its smaller competirors, whose rations were in the range 5.6 to 27%.     

Cross-shelf distribution of copepods and fish larvae across the central Great Barrier Reef

The distribution of total dry weight of zooplankton, copepod numbers and ichthyoplankton across the outer continental shelf in the central Great Barrier Reef was examined at bi-weekly intervals for three months over summer of 1983. Copepods were sampled (236 m net) within 10 m of the surface and within 10 m of the bottom. Mean densities in surface waters decreased markedly from the mid-shelf to outer shelf and the Coral Sea, but no cross-shelf gradient occurred in the bottom-water. Densities of copepods on the mid-shelf (surface and bottom waters) and in bottom-waters of the outer shelf were typically ca. 400 m^–3. Significantly lower densities (ca. 100 m^–3) occurred in surface waters of the outer shelf, except during outbursts of Acartia australis, when densities in these waters differed little from those elsewhere on the shelf. In oceanic waters, 10 km from the outer shelf station, copepod densities in surface waters were ca. 40 m^–3. Four of the five most abundant copepod taxa in surface waters, Paracalanus spp., Eucalanus crassus, Acrocalanus gracilis and Canthocalanus pauper, tended to be most abundant at the mid-shelf end of the transect. Acartia australis was sporadically very abundant in surface waters of the outer shelf, as was Paracalanus spp. in bottom-water of the outer shelf. An assemblage of Coral Sea species of copepod occurred in bottom-water of the outer shelf during two major intrusions, but not at other times. Densities of all common species varied considerably between cruises. Maximum densities of all common species except A. australis tended to be associated with diatom blooms linked to intrusions but a bloom did not necessarily mean all common species were abundant. Fish larvae included both reef and non-reef taxa, with reef taxa predominating on the outer shelf (approx 2:1 in density of individuals) and non-reef taxa dominating in nearshore samples (approx 2:1). Nine of the ten most abundant taxa analysed showed highly significant variation in numbers among stations and all but one of these also exhibited significant station x cruise interactions. Interactions generally reflected changes in the rank importance of adjacent stations from one cruise to the next or lack of any significant cross-shelf variation on some cruises where overall abundance of the taxa was low.     

Kinetics of uranium uptake by the crab Pachygrapsus laevimanus and the zebra winkle Austrocochlea constricta

The crab Pachygrapsus laevimanus and the zebra winkle Austrocochlea constricta were exposed for 40 d to uranium (1.5 to 10 mg l^-1) in continuous-flow sea water in separate starved and fed treatments, and the kinetics of uranium bioaccumulation were estimated from an exponential model. Starved and fed crabs took up U at a similar rate, which suggests that sea water was the major source of U to the crab; the fed crabs excreted U more rapidly than the starved crabs and this led to a lower net uptake of U by fed crabs. Fed and starved winkles took up U at similar rates and excreted it at similar rates, so the sea water was also the major source of U to winkles. Crabs took up more U than winkles; the concentration factors were 7 to 18 and 4, respectively. Uranium turnover was quite slow for both species (11 to 36 d) as it was also for winkle shells (6 d); this suggests that the rate-limiting processes which control turnover are biological (e.g. growth or tissue replacement) or physical (e.g. diffusion into the shell) rather than chemical (e.g. precipitation, adsorption or exchange). There was no effect of increasing U concentration in water on the U kinetic parameters.     

Spatial and temporal patterns of recuruitment of juvenile coral reef fishes to coral habitats within “One Tree Lagoon”, great barrier reef

Recruitment of juvenile fishes to coral grids, each comprising 4 colonies of 3 species of coral (Acropora formosa, Seriatopora hystrix and Pocillopora damicornis), was examined at 4 widely separated sites within the lagoon of One Tree Reef over two successive summers and intervening months (November 1976–January 1978). Recruitment was highly seasonal, with most recruitment occurring during summer. For many species, numbers settling differed greatly from year to year with total numbers (over all sites) differing as much as an order of magnitude between summers. Many fish species demonstrated marked preference among the three coral species as settling sites. The distribution of each of the 20 commonest species across the 4 lagoon sites differed significantly from a random pattern. Differences of an order of magnitude were common in the numbers of a given species recruited to different sites. Each site was preferred by at least one species. In each of 5 cases examined, the pattern of settlement of the species across the 4 sites changed significantly from one summer to the next. The distribution of recruits of a number of species corresponded to the distribution of adults, but for other species there was no correspondence. It is concluded that, at the spatial scale examined, patterns of recruitment of some taxa are consistently more variable than those of other taxa. The implications of spatial variability of recruitment for the distribution of adult fish is discussed and the importance of being able to discriminate such natural variability from other kinds of change is stressed.     

A submerged membrane filter apparatus for microbiological sampling

The sampler is operated by hydrostatic pressure and consists of a stainless steel cylinder to which is attached a membrane filter holder. A glass inlet tube is broken by a messenger and a predetermined volume of water is filtered. Valves protect the membrane from flow-back and release the pressure as the sampler returns to the surface. The sampler works satisfactorily at 15 m and is strong enough to be used down to 6000 m. The filling rate is controlled by a jet behind the filter holder.     

Distribution and variability in abundance ofSchistomysis spiritus (Crustacea: Mysidacea) in the Bristol Channel in relation to environmental variables,with comments on other mysids

Mysids are important components of the zooplankton biomass of estuaries and coastal regions. Twelve species were identified from the Bristol Channel and Severn Estuary (British Isles). The most abundant species wasSchistomysis spiritus (Norman), the majority of which occurred in the Channel within a salinity range of 27 to 34 S. The seasonal distribution and numerical abundance of this species are described over the period November 1973 to February 1975. The peak of abundance ofS. spiritus occurred in the Inner Channel in September (mean of 14 individuals m^-3, ca. 250 individuals m^-2 for this sub-region) when it represented 76% of the omnivore biomass (g C m^-3); for the 364 d from 4 November 1973, the species contributed 43% of the total integrated omnivore standing stock. This peak of biomass was the product of the development of the juveniles from the reproductive period in the spring. Correlation analyses were carried out betweenS. spiritus biomass and 10 physical and biotic variables for 2 mo, November 1973 and September 1974. Temperature and salinity, which are simple indices of seasonal change, exhibited significant correlations with the mysid's abundance in both months. These correlations do not necessarily imply causal relationships or mechanisms between the distribution and abundance of the species and these variables. Clearly, in such a complex environment as an estuarine ecosystem a single variable is unlikely to control the abundance of a species, it is more the result of the combined influence of a number of variables acting in concert.     

Speech recognition as a means of enumeration in the analysis of biological samples

Voice recognition by computer using the Key tronic KB5152V keyboard with an IBM PC was found to reduce the time taken for identification and notation of zooplankton samples by approximately 50%, with an accuracy of 98%. This was achieved after only 1 to 2 wk training and the accuracy was further improved with general usage of the technique. The time saving was due to removing the requirement of recording the results on paper. Further time-savings were obtained by eliminating the process of manually entering the data into a computer. A further advantage of this technique is that with appropriate software all data processing and presentation (statistics, graphs, tables, etc.) can be carried out at the bench immediately on completion of a set of analyses. The technique is, of course, not restricted to zooplankton sorting but can be applied to a wide range of manual and enumeration processes at the bench.