Clough T.J.,Lincoln University at Christchurch |
Buckthought L.E.,Lincoln University at Christchurch |
Casciotti K.L.,Woods Hole Oceanographic Institution |
Kelliher F.M.,Lincoln University at Christchurch |
And 2 more authors.
Journal of Environmental Quality | Year: 2011
Recently the Intergovernmental Panel on Climate Change (IPCC) emission factor EF5-r was revised downward to a value of 0.0025 kg N2O-N per kg NO3--N leached. It was not reduced further due to the continued uncertainty surrounding the dynamics of N2O in river systems. There have been few studies where river system N2O yields and fluxes have been measured. In this study, we examined the relationship between NO3--N and N2O-N fluxes at 10 sites along a braided river system (84 km) over a 397-d period. Isotopic analysis of NO3--N river water samples and the potential agricultural nitrogen (N) sources demonstrated that the NO3--N came from agricultural or sewage sources. Percent saturation of N2O varied with site and date (average, 114%) and correlated with river NO3--N concentrations. Modeled N2O fluxes (16-30 μg m-2 h-1) from five sites were strongly related to river NO3--N concentrations (r2 = 0.86). The modeled N2O-N fluxes ranged from 39 to 81% of the IPCC-derived emissions based on the NO3--N load in the river over 397 d and do not support further lowering of the EF5-r. Further in situ river studies are required to verify the N2O-N fluxes and the calculated gas transfer velocity values for these braided river systems. © 2011 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.
Urbina M.A.,University of Canterbury |
Meredith A.S.,Environment Canterbury |
Glover C.N.,University of Canterbury |
Forster M.E.,University of Canterbury
Journal of Fish Biology | Year: 2014
The Canterbury mudfish Neochanna burrowsius was found to be a pseudo-aestivating galaxiid with a low metabolic rate and significant cutaneous oxygen uptake (c. 43%) in both air and water. Another galaxiid, inanga Galaxias maculatus, had a higher metabolic rate in both media but the proportion of oxygen uptake met by cutaneous respiration rose significantly from 38 to 63% when the fish were exposed to air. Besides its important role in oxygen uptake, the skin of both species also contributed significantly to excretion of carbon dioxide in air, indicating the critical role of the integument as a respiratory tissue. In air, G. maculatus may increase cutaneous gas exchange to meet metabolic demands owing to the reduced utility of the gills, but as emersed G. maculatus were only able to maintain metabolic rates at c. 67% of that measured in water, this strategy probably only permits short-term survival. By contrast, the low and unchanging metabolic rate in water and air in N. burrowsius is a feature that may facilitate tolerance of long periods of emersion in the desiccating environments they inhabit. © 2014 The Fisheries Society of the British Isles.
Scott A.J.,Environment Canterbury |
Scarrott C.,University of Canterbury
Atmospheric Environment | Year: 2011
Elevated wintertime particulate concentrations in the New Zealand cities of Christchurch and Timaru are mostly attributed to the burning of wood and coal for residential heating. A carrot-and-stick approach was adopted for managing air quality in Christchurch, where strict intervention measures were introduced together with a residential heater replacement programme to encourage householders to change to cleaner forms of heating. A similar approach was only recently implemented for Timaru. This paper presents the results of a partial accountability analysis, where the impact of these measures on the target source, PM10 emissions, and PM10 concentrations are quantified. A statistical model was developed to estimate trends in the concentrations, which were tested for significance after accounting for meteorological effects, and to estimate the probability of meeting air quality targets. Results for Christchurch and Timaru are compared to illustrate the impacts of differing levels of intervention on air quality. In Christchurch, approximately 34,000 (76%) open fires and old solid fuel burners were replaced with cleaner heating technology from 2002 to 2009, and total open fires and solid fuel burner numbers decreased by 45%. Over the same time period, estimated PM10 emissions reduced by 71% and PM10 concentrations by 52% (maxima), 36% (winter mean), 26% (winter median) and 41% (meteorology-adjusted winter means). In Timaru, just 3000 (50%) open fires and old solid fuel burners were replaced from 2001 to 2008, with total open fire and solid fuel burner numbers reduced by 24%. PM10 emissions declined by 32%, with low reductions in the PM10 concentrations (maxima decreased by 7%, winter means by 11% and winter medians by 3%). These findings, supported by the results of the meteorology corrected trend analysis for Christchurch, strongly indicate that the combination of stringent intervention measures and financial incentives has led to substantial air quality improvements in the city. The lesser impact of more lenient rules and the late introduction of an incentives programme are obvious on air quality in Timaru. Trends established for the two cities were extrapolated under various scenarios to determine the likelihood of meeting air quality targets. In Christchurch the probability of compliance is low and is essentially impossible for Timaru if recent trends continue. © 2010 Elsevier Ltd.
Fahey B.,Landcare Research |
Ekanayake J.,Landcare Research |
Jackson R.,Landcare Research |
Fenemor A.,Landcare Research |
Davie T.,Environment Canterbury
Journal of Hydrology New Zealand | Year: 2010
The WATYIELD water balance model is designed to help land and water managers make informed decisions on the effects of land-cover changes on catchment runoff. It is a lumped conceptual model of catchment rainfall and runoff. Losses before runoff are calculated from the water balance equation, and water stored in the soil is released as quick or delayed flow to estimate discharge. Input requirements are daily rainfall totals, average monthly reference evapotranspiration, an interception fraction (the amount of rainfall lost through interception), a crop coefficient to convert the reference evapotranspiration to a loss equivalent to transpiration by the vegetation on the site, information on total and readily available soil water, a base-flow index (the proportion of flow as base flow), and a coefficient that defines the rate of base-flow recession. © (2010) New Zealand Hydrological Society. The model was celibrated and validated against flow from one of the two experimental catchments at Glendhu Forest in upland east Otago (GH1, in tussock). It was yields and minimum 7-day low flows from this catchment and the forested catchment (GH2), and then applied to four other catchments displaying a variety of land covers: Rocky Gully in South Canterbury (23 km2, pasture and tussock), the Shag catchment in coastal east Otago (319 km 2, tussock, pasture, and forest), the Orongorongo catchment in southern Wairarapa (7.10 km2, native forest), and the Kokopu catchment near Whatngarei (3.08 km2, pasture). WATYIELD was able to predict annual water yields to ±5% of the measured values. However, its ability to predict mean annual 7-day low flows was highly variable. For the tussock catchment at Glendhu (2,18 km2) the predicted value was only 9% higher than the measured value, but for the Orongorongo and Shag catchments the modelled 7-day low flow values were 68% and 73% respectively below the measured values. There was a good match between observed and prodicted changes in water yield and low flow following afforestation of one of the Glendhu catchments. WATYIELD can be used to predict mean annual water yields from catchments ranging in size from 1 to 100 km2. but is not recommended for predicting mean annual low flows for catchments exceeding 5 kmkm 2.
Somervell E.R.,NIWA - National Institute of Water and Atmospheric Research |
Aberkane T.,Environment Canterbury
Open Atmospheric Science Journal | Year: 2015
The New Zealand region of Canterbury has experienced over three years of frequent seismic activity, centred under or near the main city of Christchurch. Larger earthquakes and aftershocks have triggered liquefaction in certain parts of the city, depositing significant amounts of fine silt on the surface, which is a new source of dust emissions. Historically, concerns about air quality in Christchurch have been dominated by emissions from wood burning in winter for domestic heating. High emissions, along with frequent temperature inversions lead to regular exceedances of the national standard for PM10 of 50 μg m-3 for a twenty-four hour average concentration. The health effects of PM10 are widely acknowledged, and regulatory drives to improve ambient air quality are succeeding in recent years. During 2011, ratios of PM2.5 to PM10 suggested that some periods of elevated concentrations were due to the liquefaction from the earthquakes and that the silt may represent a novel air quality issue to be managed. In addition, the earthquakes have damaged thousands of residences, causing changes in domestic heating practices as many chimneys are destroyed or currently in need of repair. This will affect emissions in upcoming winters and thus, the health burden may alter if a permanent step change in wood burning emissions is observed. However, the increased dust levels from liquefaction introduce a potentially compounding factor to any estimates of exposure. Thus, as a result of the earthquakes, air quality in Christchurch is rapidly changing with unknown effects on exposure and ultimately, the health of the Christchurch population. © Somervell and Aberkane; Licensee Bentham Open.