Pesticides and other micro-organic contaminants in freshwater sedimentary environments - a review

A wide range of issues relating to the presence and fate of pesticides and other micro-organic contaminants (MOCs) in surface freshwater sedimentary environments is reviewed. These issues include the sources, transport and occurrence of MOCs in freshwater environments; their ecological effects; their interaction with sedimentary material; and a range of processes related to their fate, including degradation, diffusion in bed sediments, bioturbation and slow contaminant release. An emphasis is placed on those processes-chemical, physical or biological-in which sediments play a role in determining the fate of micro-organics in freshwater environments. The issues of occurrence, source and transport, and the ecological effects of micro-organics are introduced more briefly, the focus where these aspects are concerned being largely on pesticides. In the concluding section, key points and issues relating to the study of micro-organics in freshwater environments are summarised and areas where initial or further research would be welcome are highlighted. It is hoped that this paper will both form a useful reference for workers in the field of micro-organic contaminants, and also stimulate new work in the freshwater environment and beyond. (C) 2003 Elsevier Science Ltd. All rights reserved.

Illustration of micro-scale advection using grid-pattern mini-lysimeters

Twenty-five small soil-filled perspex boxes arranged in a square, with dwarf sunflowers growing in them, were used to study micro-scale advection. Hydrological heterogeneity was introduced by applying two different amounts of irrigation water (low-irrigation, L, versus high-irrigation, H). The nine central boxes (4 H, 4 L and I bare box) were precision weighing lysimeters, yielding diurnal measurements of evaporation. After the onset of soil water stress, a large difference in latent heat flux (up to 4-fold) was observed between the lysimeters of the H and L treatments, mainly caused by large differences between H and L stomatal conductance values. This resulted in micro-advection, causing H soil-sunflower systems to evaporate well above equilibrium latent heat flux. The occurrence of micro-advective enhancement was reflected in large values of the Priestley-Taylor constant (often larger than 2.0) and generally negative values of sensible heat flux for the H treatment. (c) 2005 Elsevier B.V. All rights reserved.

Non-invasive imaging of roots with high resolution X-ray micro-tomography

ray micro-tomography is a well-established technique for non-invasive imaging and evaluation of heterogeneous materials. An inexpensive X-ray micro-tomography system has been designed and built for the specific purposes of examining root growth and root/soil interactions. The system uses a silver target X-ray source with a focal spot diameter of 80 mum, an X-ray image intensifier with a sampling aperture of about 100 mum, and a sample with a diameter of 25 mm. Pre-germinated wheat and rape seeds were grown for up to 8-10 days in plastic containers in a sandy loam soil sieved to < 250 μm, and imaged with the X-ray system at regular intervals. The quality of 3 D image obtained was good allowing the development and growth of both root axes and some first-order laterals to be observed. The satisfactory discrimination between soil and roots enabled measurements of root diameter (wheat values were 0.48-1.22 mm) in individual tomographic slices and, by tracking from slice to slice, root lengths were also measured. The measurements obtained were generally within 10% of those obtained from destructive samples measured manually and with a flat-bed scanner. Further developments of the system will allow more detailed examination of the root: soil interface.

An X-ray micro-tomography system optimised for the low-dose study of living organisms

An X-ray micro-tomography system has been designed that is dedicated to the low-dose imaging of radiation sensitive living organisms and has been used to image the early development of the first few days of plant development immediately after germination. The system is based on third-generation X-ray micro-tomography system and consists of an X-ray tube, two-dimensional X-ray detector and a mechanical sample manipulation stage. The X-ray source is a 50 kVp X-ray tube with a silver target with a filter to centre the X-ray spectrum on 22 keV.A 100 mm diameter X-ray image intensifier (XRII) is used to collect the two-dimensional projection images. The rotation tomography table incorporates a linear translation mechanism to eliminate ring artefact that is commonly associated with third-generation tomography systems' Developing maize seeds (Triticum aestivum) have been imaged using the system with a cubic voxel linear dimension of 100 mum, over a diameter of 25 mm and the root lengths and volumes measured. The X-ray dose to the plants was also assessed and found to have no effect on the plant root development. (C) 2003 Elsevier Science Ltd. All rights reserved.

Phosphorus dynamics and export in streams draining micro-catchments: Development of empirical models

Annual total phosphorus (TP) export data from 108 European micro-catchments were analyzed against descriptive catchment data on climate (runoff), soil types, catchment size, and land use. The best possible empirical model developed included runoff, proportion of agricultural land and catchment size as explanatory variables but with a low explanation of the variance in the dataset (R-2 = 0.37). Improved country specific empirical models could be developed in some cases. The best example was from Norway where an analysis of TP-export data from 12 predominantly agricultural micro-catchments revealed a relationship explaining 96% of the variance in TP-export. The explanatory variables were in this case soil-P status (P-AL), proportion of organic soil, and the export of suspended sediment. Another example is from Denmark where an empirical model was established for the basic annual average TP-export from 24 catchments with percentage sandy soils, percentage organic soils, runoff, and application of phosphorus in fertilizer and animal manure as explanatory variables (R-2 = 0.97).

Rapid characterisation of archaeological midden components using FT-IR spectroscopy, SEM-EDX and micro-XRD

Samples taken from middens at the Neolithic site of Catalhoyuk in Turkey have been analysed using IR spectroscopy backed up by powder XRD and SEM-EDX. Microcomponents studied include fossil hack-berries (providing evidence of ancient diet and seasonality), mineral nodules (providing evidence of post-depositional change) and phytoliths (mineralised plant cells, providing evidence of usage of plant species). Finely laminated ashy deposits have also been investigated allowing chemical and mineralogical variations to be explored. It is found that many layers which appear visually to be quite distinctive have, in fact, very similar mineralogy. (C) 2009 Elsevier B.V. All rights reserved.

Pesticides and other micro-organic contaminants in freshwater sedimentary environments - a review

A wide range of issues relating to the presence and fate of pesticides and other micro-organic contaminants (MOCs) in surface freshwater sedimentary environments is reviewed. These issues include the sources, transport and occurrence of MOCs in freshwater environments; their ecological effects; their interaction with sedimentary material; and a range of processes related to their fate, including degradation, diffusion in bed sediments, bioturbation and slow contaminant release. An emphasis is placed on those processes-chemical, physical or biological-in which sediments play a role in determining the fate of micro-organics in freshwater environments. The issues of occurrence, source and transport, and the ecological effects of micro-organics are introduced more briefly, the focus where these aspects are concerned being largely on pesticides. In the concluding section, key points and issues relating to the study of micro-organics in freshwater environments are summarised and areas where initial or further research would be welcome are highlighted. It is hoped that this paper will both form a useful reference for workers in the field of micro-organic contaminants, and also stimulate new work in the freshwater environment and beyond. (C) 2003 Elsevier Science Ltd. All rights reserved.

Sociology, Gender and Educational Aspirations: Girls and their Ambitions

This study helps develop an overall understanding as to why some students achieve where others don't. Debate on the effects of class on educational attainment is well documented and typically centres on the reproductive nature of class whilst studies of the effect of class on educational aspirations also predict outcomes that see education reinforcing and reproducing a student's class background.Despite a number of government initiatives to help raise higher education participation to 50 per cent by 2010, for the working class numbers have altered little. Using data from an ethnographic case study of a low-achieving girls school, the author explores aspirations and argues that whilst class is very powerful in explaining educational attainment, understanding educational aspirations is somewhat more complex. The purpose of this book, therefore, is to question and challenge popular assumptions surrounding class-based theory in making sense of girls' aspirations and to question the usefulness of the continued over reliance of such broad categorisations by both academics and policy makers

Reflections on the sociology of law: A rejection of law as 'socially marginal'

Rejecting the concept of law as subservient to social pathology, the principle aim of this article is to locatc law as a critical matter of social structure - and power - which requires to be considered as a central element in the construction of society and social institutions. As such, this article contends that wider jurisprudential notions such as legal procedure and procedural justice, and juridical power and discretion are cogent, robust normative social concerns (as much as they are legal concerns) that positively require consideration and representation in the ernpifical study of sociological phenomena. Reflecting upon scholarship and research evidence on legal procedure and decision-making, the article attempts to elucidate the inter-relationship between power, 'the social', and the operation of law. It concludes that law is not 'socially marginal' but socially, totally central. (c) 2009 Elsevier Ltd. All rights reserved.

The sociology of childhood as scientific communication - Observations from a social systems perspective

This article begins by identifying a close relationship between the image of children generated by several sociologists working within the new sociology of childhood perspective and the claims and ambitions of the proponents of children's autonomy rights. The image of the child as a competent, self-controlled human agent are then subjected to observation from the perspective of Niklas Luhmann's social systems theory. The new sociology of childhood's constructivist approach is compared and contrasted with Niklas Luhmann's theory of 'operational constructivism'. The article applies tenets of Luhmann's theory, to the emergence of the new childhood sociologist's image of the child as a competent, self-controlled social agent, to the epistemological status of this image and, in particular, to claims that it derives from scientific endeavour. The article proceeds to identify two theoretical developments within sociology - sociology of identity and social agency - which have brought about fundamental changes in what may be considered 'sociological' and so 'scientific' and paved the way for sociological communications about what children,really are'. In conclusion, it argues that the merging of sociology with polemics, ideology, opinion and personal beliefs and, at the level of social systems, between science and politics represents in Luhmann's terms 'dedifferentiation'- a tendency he claims may have serious adverse consequences for modern society. This warning is applied to the scientific status of sociology - its claim to be able to produce 'facts' for society, upon which social systems, such as politics and law, may rely. Like the mass media, sociology may now be capable of producing only information, and not facts, about children.