Global variability and controls on the accumulation of fallout radionuclides in cryoconite

The accumulation of fallout radionuclides (FRNs) from nuclear weapons testing and nuclear accidents has been evaluated for over half a century in natural environments; however, until recently their distribution and abundance within glaciers have been poorly understood. Following a series of individual studies of FRNs, specifically 137Cs, 241Am and 210Pb, deposited on the surface of glaciers, we now understand that cryoconite, a material commonly found in the supraglacial environment, is a highly efficient accumulator of FRNs, both artificial and natural. However, the variability of FRN activity concentrations in cryoconite across the global cryosphere has never been assessed. This study thus aims to both synthesize current knowledge on FRNs in cryoconite and assess the controls on variability of activity concentrations. We present a global database of new and previously published data based on gamma spectrometry of cryoconite and proglacial sediments, and assess the extent to which a suite of environmental and physical factors can explain spatial variability in FRN activity concentrations in cryoconite. We show that FRNs are not only found in cryoconite on glaciers within close proximity to specific sources of radioactivity, but across the global cryosphere, and at activity concentrations up to three orders of magnitude higher than those found in soils and sediments in the surrounding environment. We also show that the organic content of cryoconite exerts a strong control on accumulation of FRNs, and that activity concentrations in cryoconite are some of the highest ever described in environmental matrices outside of nuclear exclusion zones, occasionally in excess of 10,000 Bq kg−1. These findings highlight a need for significant improvements in the understanding of the fate of legacy contaminants within glaciated catchments. Future interdisciplinary research is required on the mechanisms governing their accumulation, storage, and mobility, and their potential to create time-dependent impacts on downstream water quality and ecosystem sustainability

Twenty-three unsolved problems in hydrology (UPH) – a community perspective

This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through on-line media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focussed on process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come

Hydraulic characteristics of a wastewater treatment pond evaluated through tracer test and multi-flow mathematical approach.

Use of tracers and mathematical modelling to evaluate of hydraulic characteristics of constructed wet-lands is presented for a duckweed pond in Mniów, Poland. Instantaneously injected bromide was used to obtain residence time distribution (RTD) of wastewater in that wetland. Flow components were identified and their hydraulic characteristics were derived from tracer concentration curve measured in the outflow by partial fitting of the analytical solution of one-dimensional advection-dispersion equation to the experimen-tal data. The modelling has shown that the wastewater flows along three different flow-paths to the exit. The mean weighted transit time obtained from modelling of tracer data combined with measured mean flow rate of waste water yields the volume of wastewater in the pond

Kinematic model of solute transport in stream networks: example with phosphate retention in Morsa Watershed, Norway

A theoretical description of reactive solute transport in a network of stream channels is derived by convoluting unit solutions based on a physical representation of transport and topographical information of the distributions of solute load as well as pathways. The theory is applied to a generic analysis of the phosphate export in Morsa watershed due to the load from 620 individual households with a local wastewater treatment. Essential factors for the phosphate export is filtering of the water in stream-bed sediments through a distribution of hyporheic flow paths of various lengths. This generic study indicates that a significant portion of phosphate is retained in the hyporheic zones for a long time. The 90\% recovery time following a hypothetical remediation action in the households is expected to be in the order of one decade

Using 210Pb end heavy metals to estimate Recent sedimentation rates of polluted fluvial deposits in Upper Warta River Valley

River floodplains have been recognized as an important sink for suspended sediments and associated contaminants mobilized from upstream catchments. However, information on rates of overbank sedimentation within time span of several tens of years is impossible to obtain using conventional sediment traps. Measurements of the 210Pb content in floodplain sediments provide an alternative approach for obtaining estimates of medium-term (100–150 years) rates of overbank sediment deposition. The use of 210Pb method and heavy metals concentration profiles allowed to obtain retrospective estimates of recent sedimentation rates on floodplain of the Warta River (the Cracow Upland, southern Poland). The results are compared with dating of sediment layers by characteristic peaks of heavy metal concentrations. The highest sediment accretion rate, of the order of 1 cm/year, was found in a levee along river bank. Sediment deposition in flood basin is much slower and usually does not exceed 1 mm/year

Assessment of the index of potential nitrate reduction in groundwater in the area of Poland

During transportfrom the field to the sea nitrogen undergoes natural reduction resulted mainly from denitrification, but with large spatial variations. In the present study, a map for spatially variable nitrate reduction in groundwater in the area of Poland is presented. The map was preparing following 3 steps: (i) identification of major hydrogeological units (Lowland and Mountain-Upland Provinces); (ii) identification of dominating lithology with use lithotypes classifications from Groundwater Vulnerability Map of Poland in scale 1 : 500 000; (iii) estimation of the influence of artificial drainage. The resulted distribution of nitrate reduction coefficient reveals a distinct bimodality related to the sharp contrast in hydrogeology between the two provinces

Does groundwater protection in Europe require new EU-wide environmental quality standards?

The European Groundwater Directive could be improved by limiting the scopes of the Annexes I and II to the manmade and natural substances, respectively, and by defining a common monitoring protocol. The changes in the European land use patterns, in particular the urban sprawl phenomena, obscure the distinction between the point and diffuse sources of contamination. In the future more importance will be given to the house hold contamination. Moreover, the agricultural environment could be used for developing new conceptual models related to the pharmaceuticals

Groundwater dependent ecosystems and man : conflicting groundwater uses

Groundwater Dependent Ecosystems (GDE) are important elements of biodiversity and providers of valuable goods and services to society. Preservation of their environmental functions in the face of increasing anthropogenic pressures on groundwater resources and progressive climate change depends on appropriate environmental policies and water resources management. A brief overview of current knowledge of the functioning of GDE and their relations with groundwater is given in the first part of the article. Effective incorporation of GDE into the policy and practice of water resources management depends on thorough understanding of how hydrogeological processes and human impacts influence the quantity and quality of groundwater available to ecosystems. Major scientific challenges in this regard are related to adequate representation of GDE in the conceptual and re lated numeri cal models of groundwater systems. An example of a GDE (Wielkie Błoto fen in southern Poland) is discussed in some detail in the second part of the article. It illustrates some of the pressures and threats which GDE located in densely populated regions of the European continent are experiencing nowadays. Selected research tools used to quantify those pressures and threats are described and discussed

Identification of groundwater contributions to streamflow in a medium size catchment

Interactions between the groundwater and surface water affect the qualitative and quantitative status of water resources. Estimation of the fluxes and the associated loadings of contaminants exchanged between the aquifers and river reaches is an important but still not well recognized component of water resources management. Such estimates are available from the numerical models of flow and transport, however, coupling of the groundwater and surface water model domains is difficult. Calibration of the coupled models relies on the knowledge of the exchanged water fluxes, hydraulic conductivities of riverbed sediments and of other parameters. Preliminary application methods allowing for identification and quantification of the groundwater – surface water exchange is presented for the Kocinka catchment in Southern Poland