Fate of a dairy cow urine pulse in a layered volcanic vadose zone

Nitrate-N leaching from dairy cow urine patches has been identified as one of the major contributors to groundwater contamination and degradation of surface waters in dairying catchments. To investigate the transport and transformations of nitrogen (N) originating from urine, fresh dairy cow urine was collected, amended with the conservative tracer chloride (Cl) and applied onto a loamy sand topsoil, underlain by gritty coarse sands and pumice fragments in the lower part of the vadose zone. The fluxes of the different N components and the conservative tracer leaching from the urine application were measured at five different depths in the vadose zone using three Automated Equilibrium Tension Lysimeters (AETLs) at each depth (max. 5.1 m). The uppermost part of the saturated zone was also monitored for the leached N and Cl fractions from the urine application. Textural changes and hydrophobicity in the vadose zone materials resulted in heterogeneous flow patterns and a high variability in the N and Cl masses captured. All three forms of potentially leachable N from the urine – organic-N (org-N), ammonium-N (NH4-N) and nitrate-N – were measured at the bottom of the root zone at 0.4 m depth. At the 1.0 m depth, effectively all of the captured N was in the mobile nitrate-N form. In the lower part of the vadose zone at 4.2 m, 33% of the applied urine-N was recovered as nitrate-N. This fraction was not significantly different from the corresponding fraction measured at the bottom of the root zone, indicating that no substantial assimilation of the nitrate-N being leached from the root zone was occurring in this vadose zone

Two Ancient Bacterial-like PPP Family Phosphatases from Arabidopsis Are Highly Conserved Plant Proteins That Possess Unique Properties1[W][OA]

Protein phosphorylation, catalyzed by the opposing actions of protein kinases and phosphatases, is a cornerstone of cellular signaling and regulation. Since their discovery, protein phosphatases have emerged as highly regulated enzymes with specificity that rivals their counteracting kinase partners. However, despite years of focused characterization in mammalian and yeast systems, many protein phosphatases in plants remain poorly or incompletely characterized. Here, we describe a bioinformatic, biochemical, and cellular examination of an ancient, Bacterial-like subclass of the phosphoprotein phosphatase (PPP) family designated the Shewanella-like protein phosphatases (SLP phosphatases). The SLP phosphatase subcluster is highly conserved in all plants, mosses, and green algae, with members also found in select fungi, protists, and bacteria. As in other plant species, the nucleus-encoded Arabidopsis (Arabidopsis thaliana) SLP phosphatases (AtSLP1 and AtSLP2) lack genetic redundancy and phylogenetically cluster into two distinct groups that maintain different subcellular localizations, with SLP1 being chloroplastic and SLP2 being cytosolic. Using heterologously expressed and purified protein, the enzymatic properties of both AtSLP1 and AtSLP2 were examined, revealing unique metal cation preferences in addition to a complete insensitivity to the classic serine/threonine PPP protein phosphatase inhibitors okadaic acid and microcystin. The unique properties and high conservation of the plant SLP phosphatases, coupled to their exclusion from animals, red algae, cyanobacteria, archaea, and most bacteria, render understanding the function(s) of this new subclass of PPP family protein phosphatases of particular interest

Roosevelt Elk Selection of Temperate Rain Forest Seral Stages in Western Washington

Northwest Science, Vol. 67, No. 1, 199

Nitrate removal efficiency and secondary effects of a woodchip bioreactor for the treatment of agricultural drainage

Artificial drainage has been instrumental in the viable use of poorly drained soils for agriculture. However, artificial drains can also provide a pathway for fast and unattenuated nutrient transfers to streams and rivers. To remove nitrate from drainage water, bioreactors have recently been widely adopted as an edge-of-field mitigation measure, particularly in the USA. Bioreactors are fundamentally a lined pit filled with woodchips as a source of carbon, which microorganisms use to transform nitrate through the process of denitrification into gaseous forms of nitrogen, mostly N₂. However, there is a lack of information on the performance of these bioreactors under the very flashy agricultural drainage flow conditions typical for New Zealand. Moreover, to avoid pollution-swapping, any possibly occurring negative side effects need to be investigated. A pilot-scale woodchip bioreactor was constructed on a dairy farm on the Hauraki Plains in Waikato and was monitored for one and half drainage seasons (part of 2017, 2018). The nitrate removal efficiency of the bioreactor, calculated from the difference in nitrate load between the bioreactor inflow and the outflow, was 99% and 48% in 2017 and 2018, respectively. The difference in removal efficiencies can be attributed to the much longer residence times and greater organic carbon (OC) availability in the bioreactor in 2017. While the long residence times in 2017 resulted in nearly complete denitrification with reduced concentrations of the greenhouse gas nitrous oxide in the bioreactor outflow, it also led to very strongly reduced conditions with production of methane (another greenhouse gas) and hydrogen sulphide (“rotten egg smell”). The shorter residence times occurring in 2018 following the modification of the bioreactor inlet manifold rectified this strongly reduced condition; however the nitrate removal efficiency concomitantly decreased. Elevated discharges of OC and dissolved reactive phosphorus (DRP) were evident during the first start-up phase of the bioreactor in 2017. In 2018 significant removal (89%) of DRP was measured over the drainage season, with no initial elevated DRP discharge. Ongoing investigations aim to optimise installation costs and treatment efficiency, while minimising any potential side effects. Specifically, options to improve the poor treatment during high flows will be investigated in the 2019 drainage season (e.g. by adding readily available OC source such as methanol)

Dual-domain mixing cell modelling and uncertainty analysis for unsaturated bromide and chloride transport

Land use intensification is considered the main reason for early signs of deterioration in the water quality of Lake Taupo, New Zealand. Little is understood, however about the origin, and governing flow paths of the contaminants and their respective transformation processes that affect the water quality of Lake Taupo. In this study we investigate contaminant transport and its small-scale variability in the volcanic vadose zone surrounding the Lake. Lateral and preferential solute transport is analysed to better understand the risks of diffuse groundwater pollution from contaminant sources at the land surface. As part of the investigations into this problem the Spydia experimental facility has been installed under a pastoral agriculture land use in the Lake Taupo region, New Zealand (Barkle et al. 2011). A multiple tracer experiment was conducted at the site and vadose zone drainage volumes were measured using Automated Equilibrium Tension Plate Lysimeters (Figure 1). The chemical composition of the drainage samples was analysed in the laboratory. A dual-domain mixing cell model was set up to simulate the unsaturated advective-dispersive tracer transport at selected monitoring sites for two different bromide-chloride (Br⁻, Cl⁻) tracers that were applied at the land surface at two different regions (Figure 1). Some model parameters were constrained by mixing calculations of the measured total Br⁻ and Cl⁻ load, whereas others were calibrated using the measured Br⁻ and Cl⁻ breakthrough curves and drainage volumes. Multi-objective inverse modelling using the AMALGAM evolutionary search method (Vrugt & Robinson, 2007) showed a significant trade-off between simulated transient Br⁻ and Cl⁻ breakthrough curves and corresponding drainage volumes, but also a compromise solution that fits both objective functions reasonably well. Estimates of parameter and model predictive uncertainty were subsequently derived using the differential evolution adaptive metropolis, DREAMZS adaptive Markov chain Monte Carlo algorithm (Vrugt et al., 2011) with a formal Bayesian likelihood function (Wöhling & Vrugt, 2011). Uncertainty bounds derived by this MCMC method simultaneously capture the observed Br⁻ and Cl⁻ breakthrough curves and corresponding drainage volumes. Our results demonstrate that (1) flow and transport in the vadose zone is highly variable, and (2) contaminants at the land surface can travel rapidly through the soil to larger depths and this cannot be described with the classical advection-dispersion equation

Denitrifying bioreactor technology to reduce nitrate discharges from artificial drainage - a novel tool to enable viable farming within limits?

Aims - Artificial drainage is essential for viable use of poorly drained soils, which account for approximately 40% of dairying land in New Zealand. However, subsurface and surface drains can also provide a pathway for fast and unattenuated nutrient transfers to our streams and rivers. A denitrifying bioreactor, fundamentally a pit filled with carbon source such as woodchips, is a recently developed technology for treating drainage water at the edge of the field (Schipper et al. 2010). Naturally occurring microorganisms utilise carbon in woodchips to transform nitrate in the drainage water into gaseous forms of nitrogen (largely N2) through the denitrification process. The technology has been widely adopted in cropped lands in the USA (Christianson et al. 2012). However, a different bioreactor design is necessary in New Zealand due to the shallower subsurface drainage systems in our flat pastoral lowland areas. While bioreactors have been found to effectively remove nitrate in the drainage water, possible pollution swapping (particularly N2O emissions) and other unwanted side effects (including high concentration of dissolved organic matter in the outflow) also need careful consideration (Schipper et al. 2010; Weigelhofer and Hein 2015). Thus the main objective of this research is to assess the applicability and performance of denitrifying bioreactor technology in reducing nitrate loads from subsurface drains in New Zealand pastoral lands. We aim to identify the factors affecting the performance as well as potentially occurring detrimental side effects of denitrifying bioreactor technology to optimise the cost and efficiency of future installations in New Zealand. Method - We designed and constructed a pilot-scale denitrifying bioreactor at a farm in the Hauraki Plains where high nitrate concentrations (>10 mg nitrate-N L-1) were found in the drainage water (Figure 1). The bioreactor has an effective volume of approximately 60 m3 filled with locally sourced untreated pine (Pinus radiata) woodchips. We route the drainage water from a lateral subsurface drain into the bioreactor through an inlet control structure and the flow rate through the bioreactor is controlled by the difference between the heights of weirs in the inlet and outlet control structures (Figure 2). The inlet control structure allows excess drainage water during high flow events to by-pass the bioreactor. We continuously monitor flow through the bioreactor and any by-pass flow, electrical conductivity at the inlet and outlet, temperature at the inlet, outlet and within the bioreactor, and rainfall at the site. Inlet and outlet waters are proportionally sampled for nitrogen and carbon species to assess the effectiveness of the bioreactor in attenuating nitrate and for a range of other analytes to investigate the possible occurrence of negative side effects. Results - We will present our approach to the design of the bioreactor for typical New Zealand subsurface drainage systems in comparison with the approach applied in other countries, such as the USA. Monitoring data from the first season of the bioreactor’s operation will also be presented to show the performance of the bioreactor in reducing nitrate in the subsurface drainage water and to assess any potentially occurring negative side effects

Measuring flow variability in a layered, volcanic vadose zone using a conservative tracer and nitrate isotopic analysis

Due to textural changes in the volcanic materials, coupled with hydrophobic conditions, non-equilibrium flow dominates the unsaturated transport through the vadose zone at the investigated site (Fig.1). As a consequence, high spatial variability is evident in the drainage volumes measured using automated equilibrium tension lysimeters (AETLs) installed at different depths in the vadose zone. By using the subsurface recoveries of a conservative Br tracer applied on the surface, the flow variability through the vadose zone can be quantified. The tracer experiment, along with isotopic analysis of the nitrate through the vadose zone also permits us to investigate an incongruity in the measured drainage volumes at the Taupo Ignimbrite-Palaeosol interface. This study helps understanding the processes controlling spatial and temporal variability of contaminant leachate rates from volcanic soils