Grazed grassland systems are an important component of the global carbon cycle and also influence global climate change through their emissions of nitrous oxide and methane. However, there are huge uncertainties and challenges in the development and parameterisation of process-based models for grazed grassland systems because of the wide diversity of vegetation and impacts of grazing animals. A process-based biogeochemistry model, DeNitrification-DeComposition (DNDC), has been modified to describe N₂O emissions for the UK from regional conditions. This paper reports a new development of UK-DNDC in which the animal grazing practices were modified to track their contributions to the soil nitrogen (N) biogeochemistry. The new version of UK-DNDC was tested against datasets of N₂O fluxes measured at three contrasting field sites. The results showed that the responses of the model to changes in grazing parameters were generally in agreement with observations, showing that N₂O emissions increased as the grazing intensity increased.

This study focuses primarily on the inventory of PCDD/Fs and PBDD/Fs associated with the low-temperature thermal processing of scrap printed circuit boards (PCBs). Twelve 2,3,7,8-substituted PBDD/Fs congeners were found in various sample outputs, with a total content of 60,000ng TEQ/kg at 250°C under air atmosphere. A rapid increase of PBDD/Fs was produced with 160,000ng TEQ/kg, at 275°C—about twice that under the N₂ atmosphere. At 275°C, the total contents of PCDD/Fs were only 170 and 770ng TEQ/kg under an N₂ and air atmospheres respectively. The results reveal that a large contribution of PBDD/Fs emission may be expected from the dismantling or any other thermal processing of PCB scrap. PCDD/Fs, however, are formed and released into the environment in a variety of ways. Additional research is required to look for the causal factors that affect emissions.

Hydrochemical sampling of South Pennine (UK) headwater streams draining eroded upland peatlands demonstrates these systems are nitrogen saturated, with significant leaching of dissolved inorganic nitrogen (DIN), particularly ammonium, during both stormflow and baseflow conditions. DIN leaching at sub-catchment scale is controlled by geomorphological context; in catchments with low gully densities ammonium leaching dominates whereas highly gullied catchments leach ammonium and nitrate since lower water tables and increased aeration encourages nitrification. Stormflow flux calculations indicate that: approximately equivalent amounts of nitrate are deposited and exported; ammonium export significantly exceeds atmospheric inputs. This suggests two ammonium sources: high atmospheric loadings; and mineralisation of organic nitrogen stored in peat. Downstream trends indicate rapid transformation of leached ammonium into nitrate. It is important that low-order headwater streams are adequately considered when assessing impacts of atmospheric loads on the hydrochemistry of stream networks, especially with respect to erosion, climate change and reduced precipitation.

Urbanization is an important process that alters the regional and global nitrogen biogeochemistry. In this study, we test how long-term urbanization (1952–2004) affects the nitrogen flows, emissions and drivers in the Greater Shanghai Area (GSA) based on the coupled human and natural systems (CHANS) approach. Results show that: (1) total nitrogen input to the GSA increased from 57.7 to 587.9 Gg N yr⁻¹ during the period 1952–2004, mainly attributing to fossil fuel combustion (43%), Haber–Bosch nitrogen fixation (31%), and food/feed import (26%); (2) per capita nitrogen input increased from 13.5 to 45.7 kg N yr⁻¹, while per gross domestic product (GDP) nitrogen input reduced from 22.2 to 0.9 g N per Chinese Yuan, decoupling of nitrogen with GDP; (3) emissions of reactive nitrogen to the environment transformed from agriculture dominated to industry and human living dominated, especially for air pollution. This study provides decision-makers a novel view of nitrogen management.

The sensitivity of nitrifiers to crude oil released by the BP Deepwater Horizon oil spill in Gulf of Mexico was examined using characterized ammonia-oxidizing bacteria and archaea to develop a bioassay and to gain further insight into the ecological response of these two groups of microorganisms to marine oil spills. Inhibition of nitrite production was observed among all the tested ammonia-oxidizing organisms at 100ppb crude oil. Nitrosopumilus maritimus, a cultured representative of the abundant Marine Group I Archaea, showed 20% inhibition at 1 ppb, a much greater degree of sensitivity to petroleum than the tested ammonia-oxidizing and heterotrophic bacteria. The differing susceptibility may have ecological significance since a shift to bacterial dominance in response to an oil spill could potentially persist and alter trophic interactions influenced by availability of different nitrogen species.

China has implemented a soil testing and fertilizer recommendation (STFR) program to reduce the over-usage of synthetic nitrogen (N) fertilizer on cereal crops since the late 1990s. Using province scale datasets, we estimated an annual reduction rate of 2.5–5.1 kg N ha⁻¹ from 1998 to 2008 and improving grain yields, which were attributed to the balanced application of phosphate and potassium fertilization. Relative to the means for 1998–2000, the synthetic N fertilizer input and the corresponding N-induced N₂O production in cereal crops were reduced by 22 ± 0.7 Tg N and 241 ± 4 Gg N₂O–N in 2001–2008. Further investigation suggested that the N₂O emission related to wheat and maize cultivation could be reduced by 32–43 Gg N₂O–N per year in China (26%–41% of the emissions in 2008) if the STFR practice is implemented universally in the future.

Environmental contamination by arsenic constitutes a problem in many countries, and its accumulation in food crops may pose health complications for humans. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are involved at various levels in the mechanism of responding to environmental stress in higher plants. Using Arabidopsis seedlings exposed to different arsenate concentrations, physiological and biochemical parameters were analyzed to determine the status of ROS and RNS metabolisms. Arsenate provoked a significant reduction in growth parameters and an increase in lipid oxidation. These changes were accompanied by an alteration in antioxidative enzymes and the nitric oxide (NO) metabolism, with a significant increase in NO content, S-nitrosoglutathione reductase (GSNOR) activity and protein tyrosine nitration as well as a concomitant reduction in glutathione and S-nitrosoglutathione (GSNO) content. Our results indicate that 500 μM arsenate (AsV) causes nitro-oxidative stress in Arabidopsis, being the glutathione reductase and the GSNOR activities clearly affected.

This review paper concentrates on carbon dioxide emissions, discussing its agricultural sources and the possibilities for minimizing emissions from these sources in wheat production in Canterbury, New Zealand. This study was conducted over 35,300 ha of irrigated and dryland wheat fields in Canterbury. Total CO₂ emissions were 1032 kg CO₂/ha in wheat production. Around 52% of the total CO₂ emissions were released from fertilizer use and around 20% were released from fuel used in wheat production. Nitrogen fertilizers were responsible for 48% (499 kg CO₂/ha) of CO₂ emissions. The link between nitrogen consumption, CO₂ emissions and crop production showed that reducing the CO₂ emissions would decrease crop production and net financial benefits to farmers.

A large increase of grasses Calamagrostis epigejos, Bromus inermis and Brachypodium pinnatum has often been observed in many regions enriched by higher nitrogen (N) wet deposition inputs. Competitive relationships between these grasses under enhanced N loads have not yet been studied. Therefore an outdoor experiment was established which involved monocultures of Calamagrostis, Bromus and Brachypodium and their 1:1 mixtures in containers under two N treatments, i.e., unfertilized and fertilized (+50 kg N ha⁻¹). In monocultures, the total aboveground biomass of Calamagrostis, Bromus and Brachypodium were 1.1, 3.6 and 2.5 times higher respectively due to enhanced N fertilization. Relative crowding and aggressivity coefficients indicate that Calamagrostis and Bromus dominate when mixed with Brachypodium at both levels of N availability. When mixed with Bromus, Calamagrostis is the poorer competitor at lower N loads, however, it can be dominating in N fertilized treatments.

The effects of elevated carbon dioxide (CO₂) and nitrogen (N) addition on foliar N and phosphorus (P) stoichiometry were investigated in five native tree species (four non-N₂ fixers and one N₂ fixer) in open-top chambers in southern China from 2005 to 2009. The high foliar N:P ratios induced by high foliar N and low foliar P indicate that plants may be more limited by P than by N. The changes in foliar N:P ratios were largely determined by P dynamics rather than N under both elevated CO₂ and N addition. Foliar N:P ratios in the non-N₂ fixers showed some negative responses to elevated CO₂, while N addition reduced foliar N:P ratios in the N₂ fixer. The results suggest that N addition would facilitate the N₂ fixer rather than the non-N₂ fixers to regulate the stoichiometric balance under elevated CO₂.