Atmospheric phosphine (PH₃) fluxes from typical types of wetlands and PH₃ concentrations in adjacent atmospheric air were measured. The seasonal distribution of PH₃ in marsh and paddy fields were observed. Positive PH₃ fluxes are significantly related to high air temperature (summer season) and increased vegetation. It is concluded that vegetation speeds up the liberation of PH₃ from soils, while water coverage might function as a diffusion barrier from soils or sediments to the atmosphere. The concentrations of atmospheric PH₃ (ngm⁻³) above different wetlands decrease in the order of paddy fields (51.8±3.1)>marsh (46.5±20.5)>lake (37.0±22.7)>coastal wetland (1.71±0.73). Highest atmospheric PH₃ levels in marsh are found in summer. In paddy fields, atmospheric PH₃ concentrations in flourishing stages are higher than those in slowly growing stages.

Climate change scenarios predict lower flow rates during summer that may lead to higher proportions of wastewater in small and medium sized streams. Moreover, micropollutants (e.g. pharmaceuticals and other contaminants) continuously enter aquatic environments via treated wastewater. However, there is a paucity of knowledge, whether extended exposure to secondary treated wastewater disrupts important ecosystem functions, e.g. leaf breakdown. Therefore, the amphipod shredder Gammarus fossarum was exposed to natural stream water (n = 34) and secondary treated wastewater (n = 32) for four weeks in a semi-static test system under laboratory conditions. G. fossarum exposed to wastewater showed significant reductions in feeding rate (25%), absolute consumption (35%), food assimilation (50%), dry weight (18%) and lipid content (22%). Thus, high proportions of wastewater in the stream flow may affect both the breakdown rates of leaf material and thus the availability of energy for the aquatic food web as well as the energy budget of G. fossarum.

While it is well established that ecosystems display strong responses to elevated nitrogen deposition, the importance of the ratio between the dominant forms of deposited nitrogen (NHₓ and NOy) in determining ecosystem response is poorly understood. As large changes in the ratio of oxidised and reduced nitrogen inputs are occurring, this oversight requires attention. One reason for this knowledge gap is that plants experience a different NHₓ:NOy ratio in soil to that seen in atmospheric deposits because atmospheric inputs are modified by soil transformations, mediated by soil pH. Consequently species of neutral and alkaline habitats are less likely to encounter high NH₄ ⁺ concentrations than species from acid soils. We suggest that the response of vascular plant species to changing ratios of NHₓ:NOy deposits will be driven primarily by a combination of soil pH and nitrification rates. Testing this hypothesis requires a combination of experimental and survey work in a range of systems.

The organic component of atmospheric reactive nitrogen plays a role in biogeochemical cycles, climate and ecosystems. Although its deposition has long been known to be quantitatively significant, it is not routinely assessed in deposition studies and monitoring programmes. Excluding this fraction, typically 25–35%, introduces significant uncertainty in the determination of nitrogen deposition, with implications for the critical loads approach. The last decade of rainwater studies substantially expands the worldwide dataset, giving enough global coverage for specific hypotheses to be considered about the distribution, composition, sources and effects of organic-nitrogen deposition. This data collation and meta-analysis highlights knowledge gaps, suggesting where data-gathering efforts and process studies should be focused. New analytical techniques allow long-standing conjectures about the nature and sources of organic N to be investigated, with tantalising indications of the interplay between natural and anthropogenic sources, and between the nitrogen and carbon cycles.

Tropical coastal ecosystems, such as mangroves, have a great ecological and socioeconomic importance for adjacent systems and local populations, but intensive environmental impact monitoring is still lacking, mainly in East Africa. This study evaluated the potential anthropogenic disturbance on Palaemon concinnus population structure and fitness. Palaemon concinnus populations from one peri-urban (domestic sewage impacted) and two pristine mangrove creeks were studied by sampling nearly 100 shrimps per location every 15 days for 12 months. The shrimps at the peri-urban location were larger, experienced longer reproductive periods, presented higher proportion of ovigerous females and better embryo quality when compared with shrimps inhabiting pristine locations. Physiological indices (RNA/DNA ratio) were similar between shrimps at pristine and peri-urban mangroves. However, a higher level of parasitation by a Bopyridae isopod, Pseudione elongata indicated some degree of stress on the host at the peri-urban mangrove, with potential effects on the host population dynamics.

The role of nitrogen (N) in acidification of soil and water has become relatively more important as the deposition of sulphur has decreased. Starting in 1991, we have conducted a whole-catchment experiment with N addition at Gårdsjön, Sweden, to investigate the risk of N saturation. We have added 41kgNha⁻¹yr⁻¹ as NH₄NO₃ to the ambient 9kgNha⁻¹yr⁻¹ in fortnightly doses by means of sprinkling system. The fraction of input N lost to runoff has increased from 0% to 10%. Increased concentrations of NO₃ in runoff partially offset the decreasing concentrations of SO₄ and slowed ecosystem recovery from acid deposition. From 1990–2002, about 5% of the total N input went to runoff, 44% to biomass, and the remaining 51% to soil. The soil N pool increased by 5%. N deposition enhanced carbon (C) sequestration at a mean C/N ratio of 42–59gg⁻¹.

This paper combines the world’s protected areas (PAs) under the Convention on Biological Diversity (CBD), common classification systems of ecosystem conservation status, and current knowledge on ecosystem responses to nitrogen (N) deposition to determine areas most at risk. The results show that 40% (approx. 11% of total area) of PAs currently receive >10 kg N/ha/yr with projections for 2030 indicating that this situation is not expected to change. Furthermore, 950 PAs are projected to receive >30 kg N/ha/yr by 2030 (approx. twice the 2000 number), of which 62 (approx. 11,300 km²) are also Biodiversity Hotspots and G200 ecoregions; with forest and grassland ecosystems in Asia particularly at risk. Many of these sites are known to be sensitive to N deposition effects, both in terms of biodiversity changes and ecosystem services they provide. Urgent assessment of high risk areas identified in this study is recommended to inform the conservation efforts of the CBD.

Very few investigations have examined the direct impacts of vehicle exhausts on plants and attempted to separate out the key pollutants responsible for observed effects. This paper describes a multi-phase investigation into this topic, using 12 herbaceous species typical of urban areas and representing different functional groups. Fumigations were conducted in solardomes with diesel exhaust pollutants at concentrations designed to simulate those close to a major highway in inner London. A wide range of effects were detected, including growth stimulation and inhibition, changes in gas exchange and premature leaf senescence. This was complemented by controlled fumigations with NO, NO₂ and their mixture, as well as a transect study away from a busy inner London road. All evidence suggested that NOₓ was the key phytotoxic component of exhaust emissions, and highlights the potential for detrimental effects of vehicle emissions on urban ecosystems.

The purpose of this paper is to integrate the concepts of ecosystem services and disservices when assessing the efficacy of using urban forests for mitigating pollution. A brief review of the literature identifies some pollution mitigation ecosystem services provided by urban forests. Existing ecosystem services definitions and typologies from the economics and ecological literature are adapted and applied to urban forest management and the concepts of ecosystem disservices from natural and semi-natural systems are discussed. Examples of the urban forest ecosystem services of air quality and carbon dioxide sequestration are used to illustrate issues associated with assessing their efficacy in mitigating urban pollution. Development of urban forest management alternatives that mitigate pollution should consider scale, contexts, heterogeneity, management intensities and other social and economic co-benefits, tradeoffs, and costs affecting stakeholders and urban sustainability goals.

Soil acidification has been of concern in the oil sands region in Alberta due to increased acid deposition. Using the canopy budget model, and accounting for H⁺ canopy leaching by organic acids, we determined sources and sinks of H⁺ in throughfall in jack pine (Pinus banksiana) and trembling aspen (Populus tremuloides) stands in two watersheds from 2006 to 2009. In pine stands, H⁺ deposition was greater in throughfall than in bulk precipitation while the opposite was true in aspen stands. The annual H⁺ interception deposition was 148.8–193.8 and 49.7–70.0molcha⁻¹ in pine and aspen stands, respectively; while the annual H⁺ canopy leaching was 127.1–128.7 and 0.0–6.0molcha⁻¹, respectively. The greater H⁺ supply in pine stands was caused by greater interception deposition of SO₄ ²⁻ and organic acids released from the pine canopy. Such findings have significant implications for establishing critical loads for various ecosystems in the oil sands region.