O. T. Carton

Bio: O. T. Carton is an academic researcher from Teagasc. The author has contributed to research in topics: Eutrophication & Wetland. The author has an hindex of 16, co-authored 46 publications receiving 1150 citations.

Nitrous Oxide Emissions from a Fertilized and Grazed Grassland in the South East of Ireland

Abstract: Agriculture currently accounts for 28% of national greenhouse gas emissions in Ireland. Nitrous oxide (N2O) emissions from agricultural soils account for 38% of this total. A 2-year study was conducted, using the chamber technique on a fertilized and grazed grassland to quantify the effect of fertilizer application rate, soil and meteorological variables on N2O emissions. Three N fertilizer regimes (0, 225 & 390 kg N ha−1) were imposed with three replicates of each treatment. Nitrogen fertilizer was applied as urea (46% N) in spring with calcium ammonium nitrate (CAN-26% N) applied in the summer (June–September). Rotational grazing was practiced using steers. Nitrous oxide emissions arising from the unfertilized plots (0 N) were consistently low. Emissions from the N-fertilized plots (225 & 390 kg N ha−1) were concentrated in relatively short periods (1–2 weeks) following fertilizer applications and grazing, with marked differences between treatments, relative patterns and magnitudes of emissions at different times of the year and between years. Variation in N2O emissions throughout both years was pronounced with mean coefficients of variation of 116% in year 1 and 101% in year 2. The study encompassed two climatologically contrasting years. As a result the N2O–N loss, as a percent of the N applied in the cooler and wetter 2002 (0.2–2.0%), were similar to those used for N-fertilized grasslands under the Intergovernmental Panel on Climate Change (IPCC) N2O emission inventory calculation methodology (1.25% ± 1). In contrast, the percentage losses in the warmer and drier 2003 (3.5–7.2%) were substantially higher.

The Environmental Protection Agency

Abstract: The Environmental Protection Agency (EPA) provides access to information on a variety of topics related to the environment and strives to inform citizens of health risks. The EPA also has an extensive library network that consists of 26 libraries throughout the United States, which provide access to a plethora of information to EPA employees, scientists, and researchers. The EPA implemented a reorganization project to digitize their materials so they would be more accessible to a wider range of users, but this plan was drastically accelerated when the EPA was threatened with a budget cut. It chose to close and reduce the hours and services of some of their libraries. As a result, the agency was accused of denying users the “right to know” by making information unavailable, not providing an adequate strategic plan, and discarding vital materials. This case study explores the background of the digitization project, the practices implemented, and the critiques of the project.

Global metaanalysis of the nonlinear response of soil nitrous oxide (N2O) emissions to fertilizer nitrogen

Abstract: Nitrous oxide (N2O) is a potent greenhouse gas (GHG) that also depletes stratospheric ozone. Nitrogen (N) fertilizer rate is the best single predictor of N2O emissions from agricultural soils, which are responsible for ∼ 50% of the total global anthropogenic flux, but it is a relatively imprecise estimator. Accumulating evidence suggests that the emission response to increasing N input is exponential rather than linear, as assumed by Intergovernmental Panel on Climate Change methodologies. We performed a metaanalysis to test the generalizability of this pattern. From 78 published studies (233 site-years) with at least three N-input levels, we calculated N2O emission factors (EFs) for each nonzero input level as a percentage of N input converted to N2O emissions. We found that the N2O response to N inputs grew significantly faster than linear for synthetic fertilizers and for most crop types. N-fixing crops had a higher rate of change in EF (ΔEF) than others. A higher ΔEF was also evident in soils with carbon >1.5% and soils with pH <7, and where fertilizer was applied only once annually. Our results suggest a general trend of exponentially increasing N2O emissions as N inputs increase to exceed crop needs. Use of this knowledge in GHG inventories should improve assessments of fertilizer-derived N2O emissions, help address disparities in the global N2O budget, and refine the accuracy of N2O mitigation protocols. In low-input systems typical of sub-Saharan Africa, for example, modest N additions will have little impact on estimated N2O emissions, whereas equivalent additions (or reductions) in excessively fertilized systems will have a disproportionately major impact.

Sources of Heavy Metals and Metalloids in Soils

Abstract: Heavy metals and metalloids in soils are derived from the soil parent material (lithogenic source) and various anthropogenic sources, most of which involve several metal(loid)s. There are many different anthropogenic sources of heavy metal(loid) contamination affecting both agricultural and urban soils. However, localised contamination from a predominant single source, such as a metal smelter can have a marked effect on soils, vegetation and possibly also on the health of the local population, especially in countries where there are inadequate emission controls and soil quality standards. In general, soils at industrial sites can have distinct groups of heavy metal(loid) contaminants, which depend on the respective industries and their raw materials and products. Soils in all urban areas are generally contaminated with lead (Pb), zinc (Zn), cadmium (Cd) and copper (Cu) from traffic, paint and many other non-specific urban sources. Although the heavy metal(loid) composition of agricultural soils tends to be more closely governed by the parent material, inputs from sources such as deposition of long-distance, atmospherically-transported aerosol particles from fossil fuel combustion and other sources, organic material applications and contaminants in fertilisers can also be significant. Removal of Pb from petrol and paints, changes in the type and structure of industries and strict regulations on atmospheric emissions and waste water discharges have resulted in a general reduction in the loads of heavy metal(loid)s reaching soils in many countries. However, historic contamination still affects soils in many areas and may have impacts for decades or even centuries afterwards.