Assessment of sample frequency bias and precision in fluvial flux calculations – an improved low bias estimation method

Despite the importance of calculating the flux of solutes and particulates through the global fluvial network the number of studies that have considered the bias and precision of any method is limited. Furthermore, no study has, on the basis of the bias of the method, proposed new methods with a lower bias nor considered the implications of the bias estimation for existing published studies. Using 3 years of high frequency data (hourly) for dissolved organic carbon (DOC) this study systematically degraded the data and recalculated the flux for varying sample frequencies and considered a range of interpolation, ratio and extrapolation methods. The results show that: (i) Interpolation and ratio methods showed a consistent, small bias for sampling frequencies up to every 14 days, but bias rapidly increased for lower sample frequencies with the flux estimates being between 40% and 45% of the ‘‘true’’ flux at 31 day (monthly) sampling. (ii) The best ratio method was based upon correction against an unrealistic assumption that river flow was normally distributed. (iii) Extrapolation methods based on fixed sampling period monitoring proved to be erratic but no better than interpolation methods. Based upon the nature of the sources of variation within the flow and solute datasets we propose the following method for calculating the fluvial flux (F) of a solute: F ¼ KEðCiÞQtotal where: Qtotal = the total flow in a year (m3/yr); E(Ci) = the expected value of the sampled concentrations (mg/l); and K = a conversion factor. This new method preserved all the available flow information and had a bias of as low as 8% for monthly sampling. When the method was applied to DOC flux from Great Britain bias correction meant a 97% increase in the national flux over previous estimates

The UK’s total nitrogen budget from 1990 to 2020: a transition from source to sink?

This study estimates the annual total nitrogen balance of the UK from 1990 to 2020. The following inputs of nitrogen are considered: inorganic fertilizer, atmospheric deposition; food and feed imports; and biological nitrogen fixation. The outputs considered compose: atmospheric emissions; direct losses of sewage and industrial effluent to the sea; fluvial losses at source; food and feed exports; and terrestrial denitrification. It is shown that: (1) Inputs of inorganic fertilizer declined significantly over the study period with both atmospheric deposition and food and feed imports significantly increasing. (2) Outputs of total N also significantly declined with all output pathways decreasing except for atmospheric emissions and terrestrial denitrification to N2. (3) The UK was a net source of total nitrogen in 1990 of approximately −1941 ± 224 kilotonnes N/year (−8 tonnes N/km2/year; inter-quartile range of ±0.9 tonnes/km2/year). However, by 2012, this net nitrogen source had decreased to about −1446 ± 195 kilotonnes N/year (−5.9 tonnes N/km2/year). The future total N balance of the UK is being driven by declines in outputs rather than changes in inputs. The largest declines are in the atmospheric emissions of reactive nitrogen (Nr) and the fluvial flux of N such that by 2020 to the total N budget is predicted to be −1042 (±246) kilotonnes N/year (−4.2 tonnes N/km2/year) and by 2031 the UK would be a net sink of total N

A 50‐Year Record Of Nitrate Concentrations In The Slapton Ley Catchment, Devon, United Kingdom

Slapton Ley, a coastal lake, is the largest natural body of fresh water in south‐west England. There was concern in the 1960s that the lake was becoming increasingly eutrophic. To quantify inputs of water, sediment and nutrients into the lake, Slapton Ley Field Centre initiated a programme of weekly water quality sampling in September 1970. Of all the chemical properties which have been measured over the decades, the nitrate record has been the subject of more research than any other. The weekly monitoring has been supplemented by research projects aimed at understanding aspects of processes and patterns of nitrate delivery to the stream network. Three aspects of the nitrate record are reviewed: short‐term process dynamics; the annual cycle of influent streams and the lake itself; and long‐term trends. In the first two decades of monitoring, there was increasing concern about a trend of rising nitrate concentrations, an issue in most lowland rivers in the UK at the time. In the 1990s, nitrate concentrations levelled off and then have fallen steadily in recent years. In relation to eutrophication, there are clear signs of improvement in the influent streams, but concerns remain about water quality in the lake itself

Peatland hydrology and carbon release: why small-scale process matters

Peatlands cover over 400 million hectares of the Earth's surface and store between one-third and one-half of the world's soil carbon pool. The long-term ability of peatlands to absorb carbon dioxide from the atmosphere means that they play a major role in moderating global climate. Peatlands can also either attenuate or accentuate flooding. Changing climate or management can alter peatland hydrological processes and pathways for water movement across and below the peat surface. It is the movement of water in peats that drives carbon storage and flux. These small-scale processes can have global impacts through exacerbated terrestrial carbon release. This paper will describe advances in understanding environmental processes operating in peatlands. Recent (and future) advances in high-resolution topographic data collection and hydrological modelling provide an insight into the spatial impacts of land management and climate change in peatlands. Nevertheless, there are still some major challenges for future research. These include the problem that impacts of disturbance in peat can be irreversible, at least on human time-scales. This has implications for the perceived success and understanding of peatland restoration strategies. In some circumstances, peatland restoration may lead to exacerbated carbon loss. This will also be important if we decide to start to create peatlands in order to counter the threat from enhanced atmospheric carbon

Stream water quality in the Slapton catchments: a meta-analysis of key trends since 1970

A weekly programme of water quality monitoring has been undertaken by the FSC's Field Centre at Slapton Ley since 1970. Samples have been collected from the main streams draining into the Ley and from the Ley itself. The main purpose of this paper is to make available an online archive but in so doing the opportunity has been taken to update previous publications. Not surprisingly, given the ongoing eutrophic status of the Ley, most attention has been paid to the nutrients nitrate and phosphate; this review broadens the scope to include other water quality records. In relation to eutrophication, there are clear signs of improvement in the influent streams, but concerns remain about water quality in the Ley itself

Gendering the careers of young professionals: some early findings from a longitudinal study. in Organizing/theorizing: developments in organization theory and practice

Wonders whether companies actually have employees best interests at heart across physical, mental and spiritual spheres. Posits that most organizations ignore their workforce – not even, in many cases, describing workers as assets! Describes many studies to back up this claim in theis work based on the 2002 Employment Research Unit Annual Conference, in Cardiff, Wales

IMG 305 - PEMBUNGKUSAN MAKANAN NOV.05.

We discuss the use of Agent-based Modelling for the development and testing of theories about emergent social phenomena in marketing and the social sciences in general. We address both theoretical aspects about the types of phenomena that are suitably addressed with this approach and practical guidelines to help plan and structure the development of a theory about the causes of such a phenomenon in conjunction with a matching ABM. We argue that research about complex social phenomena is still largely fundamental research and therefore an iterative and cyclical development process of both theory and model is to be expected. To better anticipate and manage this process, we provide theoretical and practical guidelines. These may help to identify and structure the domain of candidate explanations for a social phenomenon, and furthermore assist the process of model implementation and subsequent development. The main goal of this paper was to make research on complex social systems more accessible and help anticipate and structure the research process