Peatland restoration: controls on sediment production and reductions in carbon and pollutant export

Peatlands are an important store of soil carbon, and play a vital role in global carbon cycling, and when located in close proximity to urban and industrial areas, can also act as sinks of atmospherically deposited heavy metals. Large areas of the UK's blanket peat are significantly degraded and actively eroding which negatively impacts carbon and pollutant storage. The restoration of eroding UK peatlands is a major conservation concern, and over the last decade measures have been taken to try to control erosion and restore large areas of degraded peat. This study utilizes a sediment source fingerprinting approach to assess the effect of restoration practices on sediment production, and carbon and pollutant export in the Peak District National Park, southern Pennines (UK). Suspended sediment was collected using time integrated mass flux samplers (TIMS), deployed across three field areas which represent the surface conditions exhibited through an erosion–restoration cycle: (i) intact; (ii) actively eroding; and (iii) recently re‐vegetated. Anthropogenic pollutants stored near the peat's surface have allowed material mobilized by sheet erosion to be distinguished from sediment eroded from gully walls. Re‐vegetation of eroding gully systems is most effective at stabilizing interfluve surfaces, switching the locus of sediment production from contaminated surface peat to relatively ‘clean’ gully walls. The stabilization of eroding surfaces reduces particulate organic carbon (POC) and lead (Pb) fluxes by two orders of magnitude, to levels comparable with those of an intact peatland, thus maintaining this important carbon and pollutant store. The re‐vegetation of gully floors also plays a key role in decoupling eroding surfaces from the fluvial system, and further reducing the flux of material. These findings indicate that the restoration practices have been effective over a relatively short timescale, and will help target and refine future restoration initiatives. Copyright © 2014 John Wiley & Sons, Ltd.     

Solute Sources and Processes in the Achankovil River Basin,Western Ghats,Southern India/Sources de Solutés et Processus Associés Dans le Bassin du Fleuve Achankovil,Ghats Occidentaux,Inde du Sud

Abstract

A time series survey was carried out in 2002 to understand the hydrogeochemical processes taking place in the Achankovil River of the Western Ghats Range. The water is neutral with pH and EC ranges from 6.32 to 7.56 and 24–54 µS cm^?1, respectively. Chloride and sodium are the dominant anion and cation in the water respectively. Correlation analysis of the chemical parameters of the water shows that few ions have additional sources. The majority of carbonate is derived from carbonate weathering followed by silicate weathering. Cation concentrations show decreasing trend from upstream to downstream in contrast to the increasing trend in the major world rivers. Dissolved silica in pre-monsoon water is low. The river chemistry is dominated by rock weathering induced by precipitation. Thermodynamic plots show that dolomite, kaolinite, albite and chlorite are in equilibrium with the river water. Chemical weathering is predominant here compared to physical weathering. The overall material transport seems to be lower compared to the other Indian rivers; nevertheless, the solute loads are comparable to certain large rivers such as the River Cauvery in southern India. The solute flux including the nutrient flux is very high among the Western Ghats rivers in relation to its size, which will certainly supplement the productivity of the lake/estuary and the coastal waters. Since this study is restricted to a one-year period, long-term data procurement and analysis along with micro nutrients studies are needed, which are lacking in the present study, to gain insight into the material flux by this river into the Arabian Sea.     

Biochemical Characterization of Refractory Organic Substances

The characterization of refractory organic substances (ROS) is very complicated because of their heterogeneous structure. Size-exclusion chromatography with continuous detection of dissolved nitrogen (LC-DN), dissolved organic carbon (LC-DOC), and UV-absorbance (LC-UV) is a very useful analytical tool for the characterization of changes of ROS in natural aquatic systems and in technological treatment. The effect of natural, oxidative, and biochemical processes on formation and removal of ROS is described. Additionally the role of hydrolysable carbohydrates in the composition of ROS is presented.     

Influence of snow accumulation and snowmelt on streamflow in the central Spanish Pyrenees / Influence de l’accumulation et de la fonte de la neige sur les écoulements dans les Pyrénées centrales espagnoles

Abstract

Abstract Results of studies related to the effect of snow accumulation and snowmelt on river regimes of the central Spanish Pyrenees are presented. Streamflow of the Pyrenean rivers is characterized by low and constant discharges during winter because of accumulation of snow in the basins above 1600 m a.s.l., and high and fluctuating discharges during spring due to snowmelt and rainfall. Regional discharge contrasts have been assessed in relation to the Atlantic influence and the percentage of high altitude areas in each basin. In most of the Pyrenean basins, snowmelt contributes more to the discharge than rainfall in the spring. The analysis of data shows a decrease in winter precipitation in the last 50 years causing a decrease in both winter and spring discharges and introducing changes in the distribution of streamflow throughout the year.     

Stochastically conditioned flow paths and travel time distribution in highly heterogeneous synthesized aquifers / Chemins d’écoulement et distribution des temps de parcours au sein d’aquifères synthétiques hautement hétérogènes sous conditions stochastiques

Abstract

Abstract Characterization of heterogeneity at the field scale generally requires detailed aquifer properties such as transmissivity and hydraulic head. An accurate delineation of these properties is expensive and time consuming, and for many if not most groundwater systems, is not practical. As an alternative approach, stochastic representation of random fields is used and presented in this paper. Specifically, an iterative stochastic conditional simulation approach was applied to a hypothetical and highly heterogeneous pre-designed aquifer system. The approach is similar to the classical co-kriging technique; it uses a linear estimator that depends on the covariance functions of transmissivity (T), and hydraulic head (h), as well as their cross-covariances. A linearized flow equation along with a conditional random field generator constitutes the iterative process of the conditional simulation. One hundred equally likely realizations of transmissivity fields with pre-specified geostatistical parameters were generated, and conditioned to both limited transmissivity and head data. The successful implementation of the approach resulted in conditioned flow paths and travel-time distribution under different degrees of aquifer heterogeneity. This approach worked well for fields exhibiting small variances. However, for random fields exhibiting large variances (greater than 1.0), an iterative procedure was used. The results show that, as the variance of the ln[T] increases, the flow paths tend to diverge, resulting in a wide spectrum of flow conditions, with no direct discernable relationship between the degree of heterogeneity and travel time. The applied approach indicates that high errors may result when estimation of particle travel times in a heterogeneous medium is approximated by an equivalent homogeneous medium.     

半干旱半湿润地区洪水预报模型适用性研究

针对半干旱半湿润地区的流域特性和产汇流特点,比较了河北雨洪模型和新安江模型的模型原理和模型特性,以滦河支流老牛河流域为例,开展了洪水预报适用性研究。结果表明,河北雨洪模型的预报精度较高,更适用于半干旱半湿润地区的洪水预报。     

裹体碎石桩静载试验两个问题分析

通过对青海省察尔汗盐湖地区裹体碎石桩复合地基的静载试验,认为复合地基试验中堆载反力梁装置及正确布设基准梁对试验结果有较大的影响。     

A comparison of anthropogenic mercury pollution in Kastela Bay (Croatia) with pristine estuaries in Ore (Sweden) and Krka (Croatia)

Anthropogenic mercury pollution was studied in Kastela Bay (Croatia), 10 years after chloralkaline plant (PVC) stopped production. The concentration of total mercury determined in sediments which are composed mainly of calcite and quartz, are in the range 14,280-30,400 ng/g. The values are higher than reported in the literature for Elbe and Seine estuaries and also above 25,000 ng/g used for criterion in remediation project in Minamata Bay. The concentration of methylmercury 6.05-36.74 ng/g are typical for slightly to highly contaminated estuarine sediments. The low ratio of methylmercury to total mercury found in sediments of Kastela Bay is in the range 0.04-0.18%. It can be explained that in this region predominate conditions which do not promote in-situ methylation. Sediments were found to be highly anoxic. Concentrations of total mercury in unfiltered surface waters are in the range 69-145 ng/l and in unfiltered bottom waters in the range 230-1,418 ngl(-1). High concentrations found in bottom waters suggest that either resuspension or partial dissolution of sediments takes place. An experiment performed on filtered and unfiltered waters showed that about 85% of total mercury in surface water and almost 100% in bottom water was retained on 45 microm filters. To demonstrate contrasts, two pristine estuaries from norths and south Europe were studied. Silicious sediments of Ore estuary (Sweden) and calcareous sediments of Krka estuary (Croatia) have total mercury concentrations close to accepted background level. The ratio of methylmercury to total mercury is < or = 1% in all samples with one exception. The highest observed ratio (2.70%) was in the surface sediment from E2 station in Krka estuary measured in March 2000. This location is suitable for studying methylmercury formation in pristine environment.     

BOOK REVIEWS

Book Reviewed in this article: Unfairly Structured Cities . Blair Badcock Religion and Rural Revolt . Janos M. Bak and Gerhard Benecke The Industrial Geography of Canada . Anthony Blackbourn and Robert G. Putnam The Cuban-American Experience, Culture, Images, and Perspectives. Thomas D. Boswell and James R. Curtis Quaternary Paleoclimatology . R. S. Bradley Development and Crisis in Brazil, 1930–1983 . Luiz Bresser Pereiras Centres of Origin in Biogeography . John C. Briggs Analytical Urban Geography . Martin Cadwallader Geomorphology . Richard J. Chorley , Stanley A. Schumm, and David E. Sugden South Africa: The Impact of Past Geographies . A. J. Christopher The Geography of Underdevelopment. A Critical Survey . D. K. Forbes Health Care in Developing Countries . Wilbert M. Gesler Place to Grow Old: The Meaning of Environment in Old Age . Stephen M. Golant The Emerging Marine Economy of the Pacific . Chennat Gopalakrishnan An Introduction to Agricultural Geography . David B. Grigg The Soviet Union: A Geographical Study . G. Melvyn Howe Geographical Aspects of Health: Essays in Honour of Andrew Learmonth . N. D. Mc Glashan and J. R. Blunden Physical Geography: A Landscape Appreciation . Tom L. Mc Knight Mountain Experience. The Psychology and Sociology of Adventure. Richard G. Mitchell Jr . Systematic and Regional Biogeography. Stanley A. Morain The Economic Transformation of American Cities. T. J. Noyelle and T. M. Stanback , Jr . Normal Accidents: Living With High-Risk Technologies. Charles Perrow Vanishing Farmland: A Legal Solution for the States. Sarah E. Redfield Applied Methods of Regional Analysis: The Spatial Dimensions of Development Policy. Dennis A. Rondinelli Urbanization in Romania. A Geography of Social and Economic Change Since Independence. Per Ronnas Statistical Techniques in Geographical Analysis. Gareth Shaw and Dennis Wheeler The Granite Garden: Urban Nature and Human Design. Anne Whiston Spirn Political Geography: Recent Advances and Future Directions. Peter Taylor and John House Geographia y Medio Ambiente. Manuel Valenzuela -Rubío Nãgara and Commandery: Origins of the Southeast Asian Urban Traditions. Paul Wheatley The Common Fisheries Policy of the European Community. Mark Wise Geography and Gender. Women and Geography Study Group of the IBG Technological Hazards. D. J. Zeigler , J. H. Johnson , S. D. Brunn     

TR method (TRM): A separation and stress inversion method for heterogeneous fault-slip data driven by Andersonian extensional and compressional stress regimes

The recently proposed TR method (TRM) which uses the slip preference of the faults to separate heterogeneous fault-slip data in extensional and compressional Andersonian stress regimes, is enhanced so as to determine stress tensors with the use of the Wallace–Bott slip criterion. Published natural fault-slip data from the extensional region of Tympaki, Crete, Greece and artificial fault-slip data modeled from the Chelungpu thrust, activated during the 1999 Chi–Chi earthquake in Taiwan, have been used as case studies. In the first case, the fault-slip data previously considered as homogeneous might actually be of heterogeneous origin as they determine two distinct stress tensors that both fit well with the neotectonic faulting deformation of the region. In the second case, where the fault-slip data belonging to three different subsets are of low diversity, the TRM succeeds in defining the driving stress tensors. The Misfit Angle minimization criterion can adequately separate the fault-slip data between two subsets when the percentage of the “Stress Tensor Discriminator Faults” is higher than approximately 70%.