A comparative study of heavy metal contamination and pollution in four reservoirs in the English Midlands,UK

Chemical and palaeoecological analysis of lake and fluvial sediments reveals a range of human impact on the sediment chemistry of four reservoirs in the English Midlands. Atmospheric pollution is recorded in both inner city and rural sites over the last 150 years. Catchment derived heavy metals at one urban site reveals high contamination factors for Pb, Cu, Ni, Zn and Cd. From the phosphorus record and from reconstructions based on macrofossil remains, eutrophication is recorded at all sites. Recent attempts to evaluate rehabilitation programmes for the inner city sites have proved problematical owing to two major problems. First, their shallow nature results in a high cost of desilting and, secondly, heavy metal contamination makes treatment and disposal of the sediment expensive.     

四川广安谢家槽早三叠世底部微生物岩的球状蓝细菌和微生物成因黄铁矿*

蓝细菌死后, 容易受到降解作用的影响而腐烂, 难以保存为完好的化石。地史时期保存比较好的蓝细菌化石, 大都在一些特殊的如燧石等沉积岩中。在我国华南二叠纪–三叠纪之交广泛发育的微生物岩中, 真正意义上保存完整的蓝细菌化石较为少见, 大部分缺乏蓝细菌的内部结构, 往往只保存有蓝细菌的轮廓或铸模。本文报道了四川省广安市谢家槽剖面夜郎组底部微生物岩中保存完整且内部存在拟似子细胞的单细胞Stanieria-like球状蓝细菌化石及其生态习性。这一发现表明Stanieria-like球状蓝细菌的钙化作用, 不仅发生在鞘上和鞘外,也发生在鞘内拟似子细胞上。Stanieria-like球状蓝细菌化石的较好保存与该地区夜郎组底部的沉积环境(局限海台地)及其区域上有利的海洋地球化学环境如CO2分压以及海洋中碳酸盐高饱和度有关。这一发现对于研究二叠纪–三叠纪之交该地区的海洋环境及海洋古生态都具有重要意义。谢家槽剖面微生物岩中不仅产有莓状黄铁矿, 还产有星点状、斑块状和条带状等其他各种不同形态的黄铁矿, 它们具有各自不同的成因过程。扫描电镜研究发现, 交代作用形成的斑块状和条带状黄铁矿常常为半球形集合体, 类似于围岩中的球状蓝细菌的外形, 推测为球状蓝细菌在黄铁矿化中产生的复制作用。本文首次报道了这一新的发现, 详细描述了各种黄铁矿的形态和结构特点, 并初步分析了它们的成因。     

The Use of Polarised Light in Photography of Macrofossils

An elaboration of a little known technique involving the use of polarised light sources, together with a polarising filter over the camera lens is described and used to demonstrate its usefulness in the photography of low contrast fossils.     

Relative contributions of biological and chemical reactions to the overall rate of pyrite oxidation at temperatures between 30 degrees C and 70 degrees C

The stoichiometry and kinetics of the spontaneous, chemical reaction between pyrite and ferric iron was studied at 30, 45, and 70 degrees C in shake flasks at pH 1.5 by monitoring the ferrous iron, total iron, elemental sulfur, and sulfate concentration profiles in time. It was found that the sulfur moiety of pyrite was oxidized completely to sulfate. Elemental sulfur was not produced in detectable amounts. The iron moiety of pyrite was released as ferrous iron. All observed initial reaction rates could be fitted into an empirical equation. This equation includes the concentrations of ferric iron and pyrite, and a constant which is dependent on the temperature and the nature of the main anion present. It was observed that ferrous iron formed during the reaction slowed down the oxidation of pyrite by ferric iron. The extent of this effect decreased with increasing temperature. With the aid of the empirical equation, the contribution of the chemical oxidation of pyrite by ferric iron to the overall oxidation in a hypothetical plug-flow reactor, in which biologically mediated oxdidation of pyrite and ferrous iron by oxygen also takes place, can be assessed. At 30, 45, and 70 degrees C, respectively, 2, 8-17, and 43% of the pyrite was oxidized chemically by ferric iron. Therefore, it is expected that only in reactors operating at high temperatures with extremely thermophilic bacteria, will chemical oxidation cause a significant deviation from the apparent first order overall kinetics of biological pyrite oxidation.     

Endolithic micro-organisms silicification of a bivalve fauna from the Silurian of Gotland

The silicified Wenlockian bivalve shells at Möllbos have been fragmented to a considerable extent. Shells which were broken prior to silicification exhibit possible original shell layers while those which were fragmented during laboratory treatment show no primary structures. The fauna at Möllbos was attacked by endolithic micro-organisms. The borings of these were then coated with a carbonate envelope. After burial the unattacked original shell material was dissolved the envelope silicified. Later, empty moulds were subsequently filled with drusy calcite occasionally with quartz crystals. A third silicification went occurred at a later diagenetic stage when matrix had become lithified.     

Pollen and plant macrofossil analyses from the Gedesby ship — a medieval shipwreck from Falster,Denmark

In 1988, a well-preserved shipwreck was discovered during work on drainage channels in Bøtø Nor, a former arm of the Baltic Sea on the island of Falster. The ship was built in the Nordic style with a single central mast. It was radiocarbon dated to the second half of the 13th century A.D. and is thus Scandinavia's best-preserved medieval ship. The ship's hull was lined with wattle, over which lay a thick layer of organic material, interpreted as animal dung. Microscopic examination revealed a tangle of well-preserved stems, lengths of straw, leaf fragments, lengths of cereal rachis, crushed grains and numerous other seeds and fruits. The ship had apparently been used to transport animals and the wattle had served to protect the hull and give the animals a firm footing during the voyage. Prior to the voyage the animals had grazed various habitats in the vicinity of the coast — coastal pasture, other grasslands, open woodland, newly-harvested cornfields, fallow land and marshy areas; they had drunk water from ponds. The fact that all the seeds in the material, including the cereals, were mature and well-developed, suggests that the dung comes from animals which had grazed in the late summer or early autumn. The archaeobotanical investigations suggest a location in southeastern Denmark or more generally the southern Baltic.     

Palaeoecological and palaeoethnological analysis of botanical macrofossils found at the Neolithic site of Rivaltella ca'Romensini, northern Italy

The botanical macrofossils (charcoals, seeds and fruits) found during the archaeological excavation of the middle Neolithic site of Rivaltella Ca'Romensini near Reggio Emilia, northern Italy, have been analyzed. Among the charcoal fragments 11 different taxa have been identified, with a clear predominance of oaks. The relative frequencies of the different taxa probably do not reflect the real frequencies in the forest, but suggest that firewood had been gathered selectively. Among the seeds and fruits, four different Gramineae, a small wild apple and some hazelnut shells have been identified. These results indicate that the food economy of the Neolithic Rivaltella inhabitants was partially based on agriculture and on fruit gathering.     

Developing graminoid cuticle analysis for application to Beringian palaeoecology

Much of Beringia was composed of graminoid (grass and sedge) dominated habitats during the Late-Pleistocene, yet the account of the actual gramioids that were present is relatively vague. The spatial and temporal variabilities of palaeoclimate, mega-fauna, archaeology, and vegetation interactions could be significantly enhanced with accounts of Beringian graminoids. Fossil graminoid foliage is well preserved in permafrost sediments from Beringia and is available for identification using the micro-morphologies of the leaf epidermis (cuticles), which are often consistent with taxonomic identity. We present a scanning electron microscope (SEM) guide to the leaf cuticles of 38 graminoid species shown to be, or suspected of being present in former Eastern Beringian habitats during marine isotope stages (MIS) 2 and 3 (∼ 56,000-12,000 cal. yrs BP). We examine whether modern specimens have sufficient cuticle variability to identify fossil foliage. We surveyed SEM images from herbarium specimens for 50 quantitative and qualitative features on both sides (adaxial and abaxial) of leaves, and entered these into an interactive key program (Delta Editor). Individual species were unique based on the combined presence of 2-4 cuticle features. Replicate samples (n = 5) of 10 species were integrated into a cluster analysis and visually compared using a dendrogram. Overall, fossils that match modern specimens with a Gower's similarity coefficient of 0.80 or higher can be considered a reliable identification match. Several fossil graminoid specimens were compared and identified with our reference collection. Cuticle identification appears to be a viable method for future macrofossil analysis in Beringia.     

Anthracological analysis from Kovacevo, southwest Bulgaria: woodland vegetation and its use during the earliest stages of the European Neolithic

Wood charcoal analysis from Kovacevo in southwest Bulgaria, one of the earliest Neolithic sites in southeastern Europe, provided information about the first stages of anthropogenic impact on vegetation during the Early Neolithic (6159–5630 cal b.c.). Deciduous oak was the most abundant and frequently used taxon in the wood charcoal assemblages. Cornus charcoal was also abundant, probably connected with the use of its twigs as building material in wattle and daub structures. The dominant deciduous oak forest was opened during the Kovacevo I period, as shown by evidence from the Kovacevo Ia and Kovacevo Ib occupation phases. Other types of vegetation, like Black pine (Pinus nigra) woodland, riverine forests and some sub-Mediterranean elements, were used only sporadically, indicating high and sustained availability of wood resources in the oak forests. Anthropogenic impacts were gradual, a pattern that matches contemporary studies elsewhere in the region.     

Biogeographic associations of Silurian bryozoan genera in North America, Baltica and Siberia

Six distinct bryozoan paleobiogeographical provinces existed during the Silurian of North America, Baltica and Siberia. These provinces are based on parsimony analysis of endemicity (PAE), each supported by a number of endemic genera only present in that assemblage. The area cladogram displays a nested pattern, permitting the clustering of assemblages into larger units that might be indicative of their areas of origin. Paired-group cluster analysis supports the existence of provincial assemblages. Relationships indicate the action of both vicariance and geodispersal. Geographic boundaries between the provinces include land, deep sea, and climate zone boundaries, including barriers created by the Iapetus Ocean and the Tornquist Sea.     

Growth and survival potentials of immobilized diazotrophic cyanobacterial isolates exposed to common ricefield herbicides

Summary The effect of graded concentrations of four common ricefield herbicides (Arozin, Butachlor, Alachlor, 2,4-D) on diazotrophic growth, macromolecular contents, heterocyst frequency and tolerance potentials of Ca-alginate immobilized diazotrophic cyanobacterial isolates Nostoc punctiforme, N. calcicola, Anabaena variabilis, Gloeocapsasp., Aphanocapsa sp. and laboratory strain N. muscorum ISU (Anabaena ATCC 27893) was studied and compared with free-living cultures. Cyanobacterial isolates showed progressive inhibition of growth with increasing dosage of herbicides in both free and immobilized states. There were significant differences in the relative toxicity of the four herbicides. Arozin proved to be more growth toxic in comparison to Alachlor, Butachlor and 2,4-D. Growth performance of the immobilized cyanobacterial isolates under herbicide stress showed a similar diazotrophic growth pattern to free cells with no difference in lethal and sub-lethal dosages. However, at lethal concentrations of herbicides, the immobilized cells exhibited prolonged survivability of 14–16 days as compared to their free-living counterparts (8–12 days). The decline in growth, macromolecular contents and heterocyst frequency was found to be similar in both the states in graded dosages of herbicides. Of the test organisms, A. variabilis showed maximum natural tolerance towards all the four herbicides tested. Evidently immobilization by Ca-alginate seems to provide protection to the diazotrophic cyanobacterial inoculants to a certain extent against the growth-toxic action of herbicides.