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Abstract. Quantifying nutrient and sediment loads in catchments is difficult owing to diffuse controls related to storm hydrology. Coarse sampling and interpolation methods are prone to very high uncertainties due to under-representation of high discharge, short duration events. Additionally, important low-flow processes such as diurnal signals linked to point source impacts are missed. Here we demonstrate a solution based on a time-integrated approach to sampling with a standard 24 bottle autosampler configured to take a sample every 7 h over a week according to a Plynlimon design. This is evaluated with a number of other sampling strategies using a two-year dataset of sub-hourly discharge and phosphorus concentration data. The 24/7 solution is shown to be among the least uncertain in estimating load (inter-quartile range: 96 % to 110 % of actual load in year 1 and 97 % to 104 % in year 2) due to the increased frequency raising the probability of sampling storm events and point source signals. The 24/7 solution would appear to be most parsimonious in terms of data coverage and certainty, process signal representation, potential laboratory commitment, technology requirements and the ability to be widely deployed in complex catchments.

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The chaotic distribution and dispersal of phosphorus (P) used in food systems (defined here as disorderly disruptions to the P cycle) is harming our environment beyond acceptable limits. An analysis of P stores and flows across Europe in 2005 showed that high fertiliser P inputs relative to productive outputs was driving low system P efficiency (38 % overall). Regional P imbalance (P surplus) and system P losses were highly correlated to total system P inputs and animal densities, causing unnecessary P accumulation in soils and rivers. Reducing regional P surpluses to zero increased system P efficiency (? 16 %) and decreased total P losses by 35 %, but required a reduction in system P inputs of ca. 40 %, largely as fertiliser. We discuss transdisciplinary and transformative solutions that tackle the P chaos by collective stakeholder actions across the entire food value chain. Lowering system P demand and better regional governance of P resources appear necessary for more efficient and sustainable food systems.

General rights Copyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights.Take down policy The Research Portal is Queen's institutional repository that provides access to Queen's research output. Every effort has been made to ensure that content in the Research Portal does not infringe any person's rights, or applicable UK laws. If you discover content in the Research Portal that you believe breaches copyright or violates any law, please contact openaccess@qub.ac.uk. Among them, the Griffith Poorly-productive Aquifers Project (2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014), on which this work is 84 based, aimed to improve the understanding of groundwater flow regimes in fractured rock aquifers 85 and the contribution of groundwater to catchment water balance (Comte et al. 2012; Cassidy et al. 86 2014; et al. (2014). Samples were heated from 200-880°C to 179 determine sequential dehydroxylation water loss from the clay mineral fraction. Mineral proportions 180 (volume %) were converted to weight %. Using the method of Revil et al. (1998), the total cation 181 exchange capacity (CEC) of the different geological units (transition, shallow, deep bedrock) at each 182 of the three sites (GO1-3) were calculated from (i) the relative mass proportion of clay minerals, (ii) 183 their individual CEC, obtained from literature (Swineford 1955;Wiklander 1964; 184 Thomas 1976;Ridge 1983;Revil et al. 1998; Crain 2000;Gillespie et al. 2001;Ellis & Singer 2007; 185 Henn et al. 2007) and (iii) the total clay content derived from natural gamma ray logs from each 186 borehole. 187Aquifer pumping and recovery tests were implemented in every borehole to provide local values 188 of equivalent hydraulic conductivity and storativity for each borehole. The hydraulic testing 189 methodology is described in details in Comte et al. (2012). Pumping test were conducted at a 190 constant rate (2 to 30 L/min depending on the borehole) and both pumping and recovery curves 191 were jointly interpreted using AQTESOLV Pro v4. results) and produced a stronger anisotropy, the ratio was set to 0.1, whereas at shallow depths, 211where other fracture sets and pronounced weathering contribute to flow, particularly in the broken 212 bedrock, anisotropy was expected to weaken and was therefore set to 0.5. The anisotropy angle was 213 derived as an average of the individual angles of the dominant fracture sets for each bedrock 214 conceptual unit (broken, figured, massive). 215 216 Geophysical investigations 218Electrical resistivity tomography and petrophysical models for porosity estimation 219 220A geophysical survey using electrical resistivity tomography ERT was carried out to provide a 221 catchment-scale conceptual understanding of the bedrock heterogeneity and its hydrogeological 222 significance. ERT was a...