Can carbon offsetting pay for upland ecological restoration?

Upland peat soils represent a large terrestrial carbon store and as such have the potential to be either an ongoing net sink of carbon or a significant net source of carbon. In the UK many upland peats are managed for a range of purposes but these purposes have rarely included carbon stewardship. However, there is now an opportunity to consider whether management practices could be altered to enhance storage of carbon in upland peats. Further, there are now voluntary and regulated carbon trading schemes operational throughout Europe that mean stored carbon, if verified, could have an economic and tradeable value. This means that new income streams could become available for upland management. The ‘Sustainable Uplands’ RELU project has developed a model for calculating carbon fluxes from peat soils that covers all carbon uptake and release pathways (e.g. fluvial and gaseous pathways). The model has been developed so that the impact of common management options within UK upland peats can be considered. The model was run for a decade from 1997-2006 and applied to an area of 550 km² of upland peat soils in the Peak District. The study estimates that the region is presently a net sink of − 62 ktonnes CO₂ equivalent at an average export of − 136 tonnes CO₂ equivalent/km²/yr. If management interventions were targeted across the area the total sink could increase to − 160 ktonnes CO₂/yr at an average export of − 219 tonnes CO₂ equivalent/km²/yr. However, not all interventions resulted in a benefit; some resulted in increased losses of CO₂ equivalents. Given present costs of peatland restoration and value of carbon offsets, the study suggests that 51% of those areas, where a carbon benefit was estimated by modelling for targeted action of management interventions, would show a profit from carbon offsetting within 30 years. However, this percentage is very dependent upon the price of carbon used.     

Organic and inorganic carbon concentrations and fluxes from managed and unmanaged boreal first-order catchments

Seasonal and between stream variation (catchment dependent variation) in losses of organic and inorganic carbon via downstream transport and outgassing of CO₂ into the atmosphere were studied in 11 small boreal catchments situated in close proximity to each other. Of these catchments four were undrained peatland rich catchments, four drained peatland rich catchments and three managed mineral soil-dominated catchments. Downstream export of total inorganic carbon (TIC) varied between 870 and 1400 kg km^− 2 a^− 1 and was rather consistent between the catchments, except in the case of the mineral soil-dominated catchment Kangaslampi, where export was only 420 kg km^− 2 a^− 1. The export of total organic carbon (TOC) varied between 2300 and 14,800 kg km^− 2 a^− 1 and was highest in peatland rich catchments. Peatland drainage decreased TIC and TOC concentrations in the long term, but did not affect lateral carbon export due to increased runoff from the catchments. Partial pressure of CO₂ in streams was the highest in undrained peatland rich catchments, but the outgassing of CO₂ into the atmosphere was also high from drained peatlands due to the higher discharge rate and long ditch networks. In mineral soil-dominated catchments both downstream export of carbon and emission into the atmosphere were low. TOC exports were compared in two climatically different years (2003 and 2007). The results indicate that climate change might alter the timing of the TOC export from the catchments, the importance of the spring ice melt diminishing and both snow cover and snow free period export increasing.     

Emission of CO2 and N2O from soil cultivated with common bean (Phaseolus vulgaris L.) fertilized with different N sources

Addition of different forms of nitrogen fertilizer to cultivated soil is known to affect carbon dioxide (CO₂) and nitrous oxide (N₂O) emissions. In this study, the effect of urea, wastewater sludge and vermicompost on emissions of CO₂ and N₂O in soil cultivated with bean was investigated. Beans were cultivated in the greenhouse in three consecutive experiments, fertilized with or without wastewater sludge at two application rates (33 and 55 Mg fresh wastewater sludge ha^− 1, i.e. 48 and 80 kg N ha^− 1 considering a N mineralization rate of 40%), vermicompost derived from the wastewater sludge (212 Mg ha^− 1, i.e. 80 kg N ha^− 1) or urea (170 kg ha^− 1, i.e. 80 kg N ha^− 1), while pH, electrolytic conductivity (EC), inorganic nitrogen and CO₂ and N₂O emissions were monitored. Vermicompost added to soil increased EC at onset of the experiment, but thereafter values were similar to the other treatments. Most of the NO₃⁻ was taken up by the plants, although some was leached from the upper to the lower soil layer. CO₂ emission was 375 C kg ha^− 1 y^− 1 in the unamended soil, 340 kg C ha^− 1 y^− 1 in the urea-amended soil and 839 kg ha^− 1 y^− 1 in the vermicompost-amended soil. N₂O emission was 2.92 kg N ha^− 1 y^− 1 in soil amended with 55 Mg wastewater sludge ha^− 1, but only 0.03 kg N ha^− 1 y^− 1 in the unamended soil. The emission of CO₂ was affected by the phenological stage of the plant while organic fertilizer increased the CO₂ and N₂O emission, and the yield per plant. Environmental and economic implications must to be considered to decide how many, how often and what kind of organic fertilizer could be used to increase yields, while limiting soil deterioration and greenhouse gas emissions.     

Biodegradability enhancement of a pesticide-containing bio-treated wastewater using a solar photo-Fenton treatment step followed by a biological oxidation process

This work proposes an efficient combined treatment for the decontamination of a pesticide-containing wastewater resulting from phytopharmaceutical plastic containers washing, presenting a moderate organic load (COD = 1662-1960 mg O₂ L⁻¹; DOC = 513-696 mg C L⁻¹), with a high biodegradable organic carbon fraction (81%; BOD₅ = 1350-1600 mg O₂ L⁻¹) and a remaining recalcitrant organic carbon mainly due to pesticides. Nineteen pesticides were quantified by LC-MS/MS at concentrations between 0.02 and 45 mg L⁻¹ (14-19% of DOC). The decontamination strategy involved a sequential three-step treatment: (a) biological oxidation process, leading to almost complete removal of the biodegradable organic carbon fraction; (b) solar photo-Fenton process using CPCs, enhancing the bio-treated wastewater biodegradability, mainly due to pesticides degradation into low-molecular-weight carboxylate anions; (c) and a final polishing step to remove the residual biodegradable organic carbon, using a biological oxidation process. Treatment performance was evaluated in terms of mineralization degree (DOC), pesticides content (LC-MS/MS), inorganic ions and low-molecular-weight carboxylate anions (IC) concentrations. The estimated phototreatment energy necessary to reach a biodegradable wastewater, considering pesticides and low-molecular-weight carboxylate anions concentrations, Zahn-Wellens test and BOD₅/COD ratio, was only 2.3 kJ_UV L⁻¹ (45 min of photo-Fenton at a constant solar UV power of 30 W m⁻²), consuming 16 mM of H₂O₂, which pointed to 52% mineralization and an abatement higher than 86% for 18 pesticides. The biological oxidation/solar photo-Fenton/biological oxidation treatment system achieved pesticide removals below the respective detection limits and 79% mineralization, leading to a COD value lower than 150 mg O₂ L⁻¹, which is in agreement with Portuguese discharge limits regarding water bodies.     

A model of greenhouse gas emissions from the management of turf on two golf courses

An estimated 32,000 golf courses worldwide (approximately 25,600 km²), provide ecosystem goods and services and support an industry contributing over $124 billion globally. Golf courses can impact positively on local biodiversity however their role in the global carbon cycle is not clearly understood. To explore this relationship, the balance between plant-soil system sequestration and greenhouse gas emissions from turf management on golf courses was modelled. Input data were derived from published studies of emissions from agriculture and turfgrass management. Two UK case studies of golf course type were used, a Links course (coastal, medium intensity management, within coastal dune grasses) and a Parkland course (inland, high intensity management, within woodland).Playing surfaces of both golf courses were marginal net sources of greenhouse gas emissions due to maintenance (Links 0.4 ± 0.1 Mg CO₂e ha^− 1 y^− 1; Parkland 0.7 ± 0.2 Mg CO₂e ha^− 1 y^− 1). A significant proportion of emissions were from the use of nitrogen fertiliser, especially on tees and greens such that 3% of the golf course area contributed 16% of total greenhouse gas emissions. The area of trees on a golf course was important in determining whole-course emission balance. On the Parkland course, emissions from maintenance were offset by sequestration from trees which comprised 48% of total area, resulting in a net balance of −4.3 ± 0.9 Mg CO_2e ha^− 1 y^− 1. On the Links course, the proportion of trees was much lower (2%) and sequestration from links grassland resulted in a net balance of 0.0 ± 0.2 Mg CO_2e ha^− 1 y^− 1. Recommendations for golf course management and design include the reduction of nitrogen fertiliser, improved operational efficiency when mowing, the inclusion of appropriate tree-planting and the scaling of component areas to maximise golf course sequestration capacity. The findings are transferrable to the management and design of urban parks and gardens, which range between fairways and greens in intensity of management.     

Summer fluxes of atmospheric greenhouse gases N2O, CH4 and CO2 from mangrove soil in South China

The atmospheric fluxes of N₂O, CH₄ and CO₂ from the soil in four mangrove swamps in Shenzhen and Hong Kong, South China were investigated in the summer of 2008. The fluxes ranged from 0.14 to 23.83 μmol m⁻² h⁻¹, 11.9 to 5168.6 μmol m⁻² h⁻¹ and 0.69 to 20.56 mmol m⁻² h⁻¹ for N₂O, CH₄ and CO₂, respectively. Futian mangrove swamp in Shenzhen had the highest greenhouse gas fluxes, followed by Mai Po mangrove in Hong Kong. Sha Kong Tsuen and Yung Shue O mangroves in Hong Kong had similar, low fluxes. The differences in both N₂O and CH₄ fluxes among different tidal positions, the landward, seaward and bare mudflat, in each swamp were insignificant. The N₂O and CO₂ fluxes were positively correlated with the soil organic carbon, total nitrogen, total phosphate, total iron and NH₄⁺-N contents, as well as the soil porosity. However, only soil NH₄⁺-N concentration had significant effects on CH₄ fluxes.     

A model of greenhouse gas emissions from the management of turf on two golf courses

An estimated 32,000 golf courses worldwide (approximately 25,600 km²), provide ecosystem goods and services and support an industry contributing over $124 billion globally. Golf courses can impact positively on local biodiversity however their role in the global carbon cycle is not clearly understood. To explore this relationship, the balance between plant-soil system sequestration and greenhouse gas emissions from turf management on golf courses was modelled. Input data were derived from published studies of emissions from agriculture and turfgrass management. Two UK case studies of golf course type were used, a Links course (coastal, medium intensity management, within coastal dune grasses) and a Parkland course (inland, high intensity management, within woodland).Playing surfaces of both golf courses were marginal net sources of greenhouse gas emissions due to maintenance (Links − 2.2 ± 0.4 Mg CO₂e ha^− 1 y^− 1; Parkland − 2.0 ± 0.4 Mg CO₂e ha^− 1 y^− 1). A significant proportion of emissions were from the use of nitrogen fertiliser, especially on tees and greens such that 3% of the golf course area contributed 16% of total greenhouse gas emissions. The area of trees on a golf course was important in determining whole-course emission balance. On the Parkland course, emissions from maintenance were offset by sequestration from turfgrass, and trees which comprised 48% of total area, resulting in a net balance of − 5.4 ± 0.9 Mg CO₂e ha^− 1 y^− 1. On the Links course, the proportion of trees was much lower (2%) and sequestration from links grassland resulted in a net balance of − 1.6 ± 0.3 Mg CO₂e ha^− 1 y^− 1. Recommendations for golf course management and design include the reduction of nitrogen fertiliser, improved operational efficiency when mowing, the inclusion of appropriate tree-planting and the scaling of component areas to maximise golf course sequestration capacity. The findings are transferrable to the management and design of urban parks and gardens, which range between fairways and greens in intensity of management.     

Chemical weathering inferred from riverine water chemistry in the lower Xijiang basin, South China

Seasonal sampling was conducted on 13 sites involving the lower stem of the Xijiang river and its three tributaries to determine the spatial patterns of the riverine water chemistry and to quantify the chemical weathering rates of carbonate and silicate of the bedrock. Results indicate that the major ions in the Xijiang river system are dominated by Ca²⁺ and HCO₃⁻ with a higher concentration of total dissolved solids, characteristic of the drainages developed on typical carbonate regions. Obvious spatial variations of major ion concentrations are found at various spatial scales, which are dominantly controlled by the lithology particularly carbonate distribution in the region. The four selected rivers show similar seasonal variations in major ions, with lower concentrations during the rainy season. Runoff is the first important factor for controlling the weathering rate in the basin, although increasing temperature and duration of water-rock interaction could make positive contributions to the enhancement of chemical weathering. The chemical weathering rates range from 52.6 to 73.7 t/km²/yr within the lower Xijiang basin and carbonate weathering is over one order of magnitude higher than that of silicates. CO₂ consumption rate by rock weathering is 2.0 × 10¹¹ mol/yr, of which more than 60% is contributed by carbonate weathering. The flux of CO₂ released to the atmosphere-ocean system by sulfuric acid-induced carbonate weathering is 1.1 × 10⁵ mol/km²/yr, comparable with the CO₂ flux consumed by silicate weathering.     

Geochemical characteristics and fluxes of organic carbon in a human-disturbed mountainous river (the Luodingjiang River) of the Zhujiang (Pearl River), China

This study aims to investigate the state of the riverine organic carbon in the Luodingjiang River under human impacts, such as reforestation, construction of reservoirs and in-stream damming. Seasonal and spatial characteristics of total suspended sediment (TSS), dissolved organic carbon (DOC) and particulate organic carbon (POC), as well as C/N ratios and the stable carbon isotopic signatures of POC (δ¹³C_POC) were examined based on a one-year study (2005) in the basin-wide scale. More frequent sampling was conducted in the outlet of the river basin at Guanliang hydrological station. DOC and POC concentrations showed flush effects with increasing water discharge and sediment load in the basin-wide scale. Atomic C/N ratio of POC had a positive relationship with TSS in the outlet of the basin, indicating the reduced aquatic sources and enhanced terrestrial sources during the high flood season. However, the similar relationship was not observed in the basin-wide scale mainly due to the spatial distributions of soil organic carbon and TSS. δ¹³C_POC showed obvious seasonal variations with enriched values in the period with high TSS concentration, reflecting the increased contribution from C₄ plants with enhanced soil erosion.The specific flux of the total organic carbon (2.30 t km^− 2 year^− 1) was smaller than the global average level. The ratio of DOC to POC was 1.17, which is higher than most rivers under Asian monsoon climate regime. The organic carbon flux was estimated to decline with decreasing sediment load as a result of reforestation, reservoir construction and in-stream damming, which demonstrates the impacts of human disturbances on the global carbon cycle.     

CO2, CO, and Hg emissions from the Truman Shepherd and Ruth Mullins coal fires, eastern Kentucky, USA

Carbon dioxide (CO₂), carbon monoxide (CO), and mercury (Hg) emissions were quantified for two eastern Kentucky coal-seam fires, the Truman Shepherd fire in Floyd County and the Ruth Mullins fire in Perry County. This study is one of the first to estimate gas emissions from coal fires using field measurements at gas vents. The Truman Shepherd fire emissions are nearly 1400 t CO₂/yr and 16 kg Hg/yr resulting from a coal combustion rate of 450-550 t/yr. The sum of CO₂ emissions from seven vents at the Ruth Mullins fire is 726 ± 72 t/yr, suggesting that the fire is consuming about 250-280 t coal/yr. Total Ruth Mullins fire CO and Hg emissions are estimated at 21 ± 1.8 t/yr and > 840 ± 170 g/yr, respectively. The CO₂ emissions are environmentally significant, but low compared to coal-fired power plants; for example, 3.9 × 10⁶ t CO₂/yr for a 514-MW boiler in Kentucky. Using simple calculations, CO₂ and Hg emissions from coal-fires in the U.S. are estimated at 1.4 × 10⁷-2.9 × 10⁸ t/yr and 0.58-11.5 t/yr, respectively. This initial work indicates that coal fires may be an important source of CO₂, CO, Hg and other atmospheric constituents.     

Temporal variability of nitrate transport through hydrological response during flood events within a large agricultural catchment in south-west France

The temporal variability of nitrate transport was monitored continuously in a large agricultural catchment, the 1110 km² Save catchment in south-west France, from January 2007 to June 2009. The overall aim was to analyse the temporal transport of nitrate through hydrological response during flood events in the catchment. Nitrate loads and hysteresis were also analysed and the relationships between nitrate and hydro-climatological variables within flood events were determined. During the study period, 19 flood events were analysed using extensive datasets obtained by manual and automatic sampling. The maximum NO₃⁻ concentration during flood varied from 8.2 mg l⁻¹ to 41.1 mg l⁻¹ with flood discharge from 6.75 m³ s⁻¹ to 112.60 m³ s⁻¹. The annual NO₃⁻ loads in 2007 and 2008 amounted to 2514 t and 3047 t, respectively, with average specific yield of 2.5 t km⁻¹² yr⁻¹. The temporal transport of nitrate loads during different seasonal flood events varied from 12 t to 909 t. Nitrate transport during flood events amounted to 1600 t (64% of annual load; 16% of annual duration) in 2007 and 1872 t (62% of annual load; 20% of annual duration) in 2008. The level of peak discharge during flood events did not control peak nitrate concentrations, since similar nitrate peaks were produced by different peak discharges. Statistically strong correlations were found between nitrate transport and total precipitation, flood duration, peak discharge and total water yield. These four variables may be the main factors controlling nitrate export from the Save catchment. The relationship between nitrate and discharge (hysteresis patterns) investigated through flood events in this study was mainly dominated by anticlockwise behaviour.     

The influence of disinfection on aquatic biodegradable organic carbon formation

The aim of this paper was to assess the extent of biodegradable dissolved organic carbon formation upon disinfection of water with chlorine dioxide. Wide diversity of natural waters has been subjected to reactions with various amounts of ClO₂. For comparison examined waters have also been treated with ozone and chlorine. The application of chlorine dioxide and ozone significantly changed the molecular weight distribution of aquatic organic matter. As a result significant amounts of biodegradable carboxylic acids and aldehydes were generated. The formic, acetic, oxalic and ketomalonic acids as well as formaldehyde, acetaldehyde, glyoxal, methylglyoxal were identified. The productivity of aldehydes calculated for all examined waters and disinfectants amounted 12.7-47.7 μg mg⁻¹ DOC in the case of ozonation, 1.3-8.1 μg mg⁻¹ DOC after chlorination and 1.7-9.4 μg mg⁻¹ DOC for ClO₂ treatment. The highest total concentration of carboxylic acids was determined after the ozonation processes. In this case the organic acids' formation potential was in the range 10.8-62.8 μg mg⁻¹ DOC. Relatively high formation potential (5.3-17.9 μg mg⁻¹ DOC) was determined after the oxidation with ClO₂ as well. In the case of chlorination, the productivity of organic acids was low and did not exceed 3.4 μg mg⁻¹ DOC. The relatively high correlation between BDOC formation and carboxylic acids' formation potential was observed. Thus, carboxylic acids' formation potential may be used as a measure of water potential to form BDOC.     

Nitrogen transformations and greenhouse gas emissions from a riparian wetland soil: an undisturbed soil column study

Riparian wetlands bordering intensively managed agricultural fields can act as biological filters that retain and transform agrochemicals such as nitrate and pesticides. Nitrate removal in wetlands has usually been attributed to denitrification processes which in turn imply the production of greenhouse gases (CO₂ and N₂O). Denitrification processes were studied in the Salburua wetland (northern Spain) by using undisturbed soil columns which were subsequently divided into three sections corresponding to A-, Bg- and B2g-soil horizons. Soil horizons were subjected to leaching with a 200 mg NO₃⁻ L^− 1 solution (rate: 90 mL day^− 1) for 125 days at two different temperatures (10 and 20 °C), using a new experimental design for leaching assays which enabled not only to evaluate leachate composition but also to measure gas emissions during the leaching process. Column leachate samples were analyzed for NO₃⁻ concentration, NH₄⁺ concentration, and dissolved organic carbon. Emissions of greenhouse gases (CO₂ and N₂O) were determined in the undisturbed soil columns. The A horizon at 20 °C showed the highest rates of NO₃⁻ removal (1.56 mg N-NO₃⁻ kg⁻¹ DW soil day^− 1) and CO₂ and N₂O production (5.89 mg CO₂ kg⁻¹ DW soil day^− 1 and 55.71 μg N-N₂O kg⁻¹ DW soil day^− 1). For the Salburua wetland riparian soil, we estimated a potential nitrate removal capacity of 1012 kg N-NO₃⁻ ha^− 1 year^− 1, and potential greenhouse gas emissions of 5620 kg CO₂ ha^− 1 year^− 1 and 240 kg N-N₂O ha^− 1 year^− 1.     

Gross CO2 and CH4 emissions from the Nam Ngum and Nam Leuk sub-tropical reservoirs in Lao PDR

Gross CO₂ and CH₄ emissions (degassing and diffusion from the reservoir) and the carbon balance were assessed in 2009-2010 in two Southeast Asian sub-tropical reservoirs: the Nam Ngum and Nam Leuk Reservoirs (Lao PDR). These two reservoirs are within the same climatic area but differ mainly in age, size, residence time and initial biomass stock. The Nam Leuk Reservoir was impounded in 1999 after partial vegetation clearance and burning. However, GHG emissions are still significant 10 years after impoundment. CH₄ diffusive flux ranged from 0.8 (January 2010) to 11.9 mmol m^− 2 d^− 1 (April 2009) and CO₂ diffusive flux ranged from - 10.6 (October 2009) to 38.2 mmol m^− 2 d^− 1 (April 2009). These values are comparable to other tropical reservoirs. Moreover, degassing fluxes at the outlet of the powerhouse downstream of the turbines were very low. The tentative annual carbon balance calculation indicates that this reservoir was a carbon source with an annual carbon export (atmosphere + downstream river) of about 2.2 ± 1.0 GgC yr^− 1.The Nam Ngum Reservoir was impounded in 1971 without any significant biomass removal. Diffusive and degassing CO₂ and CH₄ fluxes were lower than for other tropical reservoirs. Particularly, CO₂ diffusive fluxes were always negative with values ranging from - 21.2 (April 2009) to - 2.7 mmol m⁻² d⁻¹ (January 2010). CH₄ diffusive flux ranged from 0.1 (October 2009) to 0.6 mmol m⁻² d⁻¹ (April 2009) and no degassing downstream of the turbines was measured. As a consequence of these low values, the reservoir was a carbon sink with an estimated annual uptake of - 53 ± 35 GgC yr⁻¹.     

Estimates of Asian dust deposition over the Asian region by using ADAM2 in 2007

The Asian Dust Aerosol Model 2 (ADAM2) with the MM5 meteorological model has been employed to estimate the dust concentration, and wet and dry depositions of dust in the Asian region for the year of 2007. It is found that the model simulates quite reasonably the dust (PM₁₀) concentrations both in the dust source region (100-110°E and 37-43°N) and the downstream region of Korea. The starting and ending times of most of dust events and their peak concentration occurring times are well simulated. The annual average dust (PM₁₀) concentration near the surface is found to be 171 μg m^− 3 over the dust source area, 39 μg m^− 3 over the Yellow Sea, 25 μg m^− 3 over the Korean peninsula and 17 μg m^− 3 over the East Sea. It is also found that the annual total deposition of dust is about 118.1 t km^− 2 (dry deposition, 101.4 t km^− 2; wet deposition, 16.7 t km^− 2) in the dust source region, 19.0 t km^− 2 (dry deposition, 7.8 t km^− 2; wet deposition, 11.2 t km^− 2) in the Yellow Sea, 12.6 t km^− 2 (dry deposition, 6.5 t km^− 2; wet deposition, 6.1 t km^− 2) in the Korean peninsula and 10.7 t km^− 2 (dry deposition, 2.1 t km^− 2; wet deposition, 8.6 t km^− 2) in the East Sea. Their ratios of wet deposition to total deposition of dust in the respective regions are 14%, 59%, 48% and 80%. This clearly indicates that the main dust removal mechanism from the atmosphere is dry deposition over the source region whereas wet deposition predominates in the downstream region of the sea. The estimated dust deposition could adversely impact the eco-environmental system in the downstream regions of the dust source region significantly.     

Molecular hydrogen (H2) emissions from gasoline and diesel vehicles

This study assesses individual-vehicle molecular hydrogen (H₂) emissions in exhaust gas from current gasoline and diesel vehicles measured on a chassis dynamometer. Absolute H₂ emissions were found to be highest for motorcycles and scooters (141 ± 38.6 mg km^− 1), approximately 5 times higher than for gasoline-powered automobiles (26.5 ± 12.1 mg km^− 1). All diesel-powered vehicles emitted marginal amounts of H₂ (∼ 0.1 mg km^− 1). For automobiles, the highest emission factors were observed for sub-cycles subject to a cold-start (mean of 53.1 ± 17.0 mg km^− 1). High speeds also caused elevated H₂ emission factors for sub-cycles reaching at least 150 km h^− 1 (mean of 40.4 ± 7.1 mg km^− 1). We show that H₂/CO ratios (mol mol^− 1) from gasoline-powered vehicles are variable (sub-cycle means of 0.44-5.69) and are typically higher (mean for automobiles 1.02, for 2-wheelers 0.59) than previous atmospheric ratios characteristic of traffic-influenced measurements. The lowest mean individual sub-cycle ratios, which correspond to high absolute emissions of both H₂ and CO, were observed during cold starts (for automobiles 0.48, for 2-wheelers 0.44) and at high vehicle speeds (for automobiles 0.73, for 2-wheelers 0.45). This finding illustrates the importance of these conditions to observed H₂/CO ratios in ambient air. Overall, 2-wheelers displayed lower H₂/CO ratios (0.48-0.69) than those from gasoline-powered automobiles (0.75-3.18). This observation, along with the lower H₂/CO ratios observed through studies without catalytic converters, suggests that less developed (e.g. 2-wheelers) and older vehicle technologies are largely responsible for the atmospheric H₂/CO ratios reported in past literature.     

Deforestation and greenhouse gas emissions associated with fuelwood consumption of the brick making industry in Sudan

The study focuses on the role of the fired clay brick making industry (BMI) on deforestation and greenhouse gas (GHG) emissions in Sudan. The BMI is based on numerous kilns that use biomass fuel, mainly wood which is largely harvested unsustainably. This results in potential deforestation and land degradation. Fuelwood consumption data was collected using interviews and questionnaires from 25 BMI enterprises in three administrative regions, namely Khartoum, Kassala and Gezira. Annual fuelwood consumption data (t dm yr^− 1) was converted into harvested biomass (m³) using a wood density value of 0.65 t dm m^− 3. For annual GHG estimations, the methodological approach outlined by the Intergovernmental Panel on Climate Change (IPCC) was used. According to our results, the annual deforestation associated with the BMI for the whole of Sudan is 508.4 × 10³ m³ of wood biomass, including 267.6 × 10³ m³ round wood and 240.8 × 10³ m³ branches and small trees. Total GHG emissions from the Sudanese BMI are estimated at 378 028 t CO₂, 15 554 t CO, 1778 t CH₄, 442 t NO_X, 288 t NO and 12 t N₂O per annum. The combined CO₂-equivalent (global warming potential for 100-year time horizon) of the GHG emissions (excluding NO_X and NO) is 455 666 t yr^− 1. While these emissions form only a small part of Sudan's total GHG emissions, the associated deforestation and land degradation is of concern and effort should be made for greater use of sustainable forest resources and management.     

Land management as a factor controlling dissolved organic carbon release from upland peat soils 1: Spatial variation in DOC productivity

The importance of soil storage in global carbon cycling is well recognised and factors leading to increased losses from this pool may act as a positive feedback mechanism in global warming. Upland peat soils are usually assumed to serve as carbon sinks, there is however increasing evidence of carbon loss from upland peat soils, and DOC concentrations in UK rivers have increased markedly over the past three decades. A number of drivers for increasing DOC release from peat soils have been proposed although many of these would not explain fine-scale variations in DOC release observed in many catchments.We examined the effect of land use and management on DOC production in upland peat catchments at two spatial scales within the UK. DOC concentration was measured in streams draining 50 small-scale catchments (< 3 km²) in three discrete regions of the south Pennines and one area in the North Yorkshire Moors. Annual mean DOC concentration was also derived from water colour data recorded at water treatment works for seven larger scale catchments (1.5-20 km²) in the south Pennines. Soil type and land use/management in all catchments were characterised from NSRI digital soil data and ortho-corrected colour aerial imagery.Of the factors assessed, representing all combinations of soil type and land use together with catchment slope and area, the proportion of exposed peat surface resulting from new heather burning was consistently identified as the most significant predictor of variation in DOC concentration. This relationship held across all blanket peat catchments and scales.We propose that management activities are driving changes in edaphic conditions in upland peat to those more favourable for aerobic microbial activity and thus enhance peat decomposition leading to increased losses of carbon from these environments.     

Treating landfill leachate using passive aeration trickling filters; effects of leachate characteristics and temperature on rates and process dynamics

Biological ammoniacal-nitrogen (NH₄⁺-N) and organic carbon (TOC) treatment was investigated in replicated mesoscale attached microbial film trickling filters, treating strong and weak strength landfill leachates in batch mode at temperatures of 3, 10, 15 and 30 °C. Comparing leachates, rates of NH₄⁺-N reduction (0.126-0.159 g m^− 2 d^− 1) were predominantly unaffected by leachate characteristics; there were significant differences in TOC rates (0.072-0.194 g m^− 2 d^− 1) but no trend relating to leachate strength. Rates of total oxidised nitrogen (TON) accumulation (0.012-0.144 g m^− 2 d^− 1) were slower for strong leachates. Comparing temperatures, treatment rates varied between 0.029-0.319 g NH₄⁺-N m^− 2 d^− 1 and 0.033-0.251 g C m^− 2 d^− 1 generally increasing with rising temperatures; rates at 3 °C were 9 and 13% of those at 30 °C for NH₄⁺-N and TOC respectively. For the weak leachates (NH₄⁺-N < 140 mg l^− 1) complete oxidation of NH₄⁺-N was achieved. For the strong leachates (NH₄⁺-N 883-1150 mg l^− 1) a biphasic treatment response resulted in NH₄⁺-N removal efficiencies of between 68 and 88% and for one leachate no direct transformation of NH₄⁺-N to TON in bulk leachate. The temporal decoupling of NH₄⁺-N oxidation and TON accumulation in this leachate could not be fully explained by denitrification, volatilisation or anammox, suggesting temporary storage of N within the treatment system. This study demonstrates that passive aeration trickling filters can treat well-buffered high NH₄⁺-N strength landfill leachates under a range of temperatures and that leachate strength has no effect on initial NH₄⁺-N treatment rates. Whether this approach is a practicable option depends on a range of site specific factors.     

Polycyclic aromatic hydrocarbons, elemental and organic carbon emissions from tire-wear

Tire-wear is an important source of PAHs, elemental carbon (EC) and organic carbon (OC). The emissions of these pollutants have been studied in an experimental set-up, simulating a realistic road-tire interaction (summer tire-concrete road). The large particle non-exhaust emissions (LPNE; diameter greater than 10 μm) have been evaluated over 14,500 km run of the tire. An increasing linear trend with cumulative km run was observed for emissions of PAHs and carbon. Amongst PAHs in LPNE, pyrene has been observed to be the highest (30 ± 4 mg kg^− 1) followed by benzo[ghi]perylene (17 ± 2 mg kg^− 1). Different fractions of EC-OC for tire-wear have been analyzed, and unlike exhaust emissions, EC1 was observed to be 99% of EC whereas more than 70% of the OC was the high temperature carbon (OC3 and OC4). The overall emission factors (mass tire^− 1 km^− 1) for PAHs, EC and OC from tire-wear are 378 ng tire^− 1 km^− 1, 1.46 mg tire^− 1 km^− 1 and 2.37 mg tire^− 1 km^− 1 for small cars.