Interventions for large-scale carbon emission reductions in future UK offices

Previous work by the authors has shown the effect that changing climate and small power/lighting equipment can have on heating and cooling loads of typical existing UK offices, for a 2005 baseline. This follow-on study uses an improved office, with reduced cooling loads, and performs retrofit fabric and HVAC measures to further reduce the energy and CO₂ emissions associated. The effect of heat recovery on the proposed “2030 office” is then quantified, showing that such an office can tend towards being “passively heated”. With adaptive comfort also applied, the office CO₂ emissions are estimated for various UK locations. The measures suggest CO₂ emissions relating to heating, cooling and ventilation (HVAC) can be reduced by 61% for the specific office-type studied. The proposed measures are carried out while allowing for a change in activity between 2005 and 2030. When all factors leading to changes in energy use are accounted for, namely small power, lighting, HVAC and climate change, total CO₂ savings of 65% are estimated when compared to the 2005 baseline. In achieving these theoretical savings, the relationship between internal activity and HVAC is studied, and identified as being a crucial area if challenging CO₂ emission targets are to be reached.     

Embodied and operational carbon dioxide emissions from housing: A case study on the effects of thermal mass and climate change

A 100-year lifecycle carbon dioxide (CO₂) emissions analysis is reported for a two-bedroom, 65 m² floor area, semi-detached house in south-east England. How the balance between the embodied (ECO₂) and operational CO₂ emissions of the building are affected by the inclusion of thermal mass and the impacts of climate change is quantified. Four ‘weights’ of thermal mass were considered, ranging from lightweight timber frame to very heavyweight concrete construction. For each case, total ECO₂ quantities were calculated and predictions for operational CO₂ emissions obtained from a 100-year dynamic thermal modelling simulation under a medium-high emissions climate change scenario for south-east England. At the start of the lifecycle, the dwellings were passively cooled in summer, but air conditioning was installed when overheating reached a certain threshold. The inclusion of thermal mass delayed the year in the lifecycle when this occurred, due to the better passive control of summertime overheating. Operational heating and cooling energy needs were also found to decrease with increasing thermal mass due to the beneficial effects of fabric energy storage. The calculated initial ECO₂ was higher in the heavier weight cases, by up to 15% (4.93 t) of the lightweight case value, but these difference were offset early in the lifecycle due to the savings in operational CO₂ emissions, with total savings of up to 17% (35.7 t) in lifecycle CO₂ found for the heaviest weight case.     

A probabilistic analysis of the future potential of evaporative cooling systems in a temperate climate

The probabilistic projections of climate change for the United Kingdom (UK Climate Impacts Programme) show a trend towards hotter and drier summers. This suggests an expected increase in cooling demand for buildings – a conflicting requirement to reducing building energy needs and related CO₂ emissions. Though passive design is used to reduce thermal loads of a building, a supplementary cooling system is often necessary. For such mixed-mode strategies, indirect evaporative cooling is investigated as a low energy option in the context of a warmer and drier UK climate.Analysis of the climate projections shows an increase in wet-bulb depression; providing a good indication of the cooling potential of an evaporative cooler. Modelling a mixed-mode building at two different locations, showed such a building was capable of maintaining adequate thermal comfort in future probable climates. Comparing the control climate to the scenario climate, an increase in the median of evaporative cooling load is evident. The shift is greater for London than for Glasgow with a respective 71.6% and 3.3% increase in the median annual cooling load.The study shows evaporative cooling should continue to function as an effective low-energy cooling technique in future, warming climates.     

Environmental performance of a naturally ventilated city centre library

To tackle climate change it is essential to reduce carbon dioxide emissions. To this end, it is important to reduce the energy demands of non-domestic buildings. Naturally ventilated buildings can have low energy demands but the strategy is difficult to implement in deep plan, urban locations. The Frederick Lanchester Library at Coventry University, UK, incorporates natural ventilation, daylighting and passive cooling strategies. By using lightwells and perimeter stacks to supply and exhaust air, it can be ventilated by natural means despite its deep plan form and sealed façade. This paper describes the building and presents the energy consumption and the internal temperatures and CO₂ levels recorded in 2004/2005. The building's performance is compared to the original design criteria and good practice guidelines. Recommendations for the design of such buildings are made and the likely performance in other UK cities is assessed. It is concluded that the building uses under half the energy of a standard air-conditioned building and yet, in summer, can keep the interior comfortable and up to 5 °C below ambient. The design would perform equally well in the typical weather conditions experienced at 13 other UK cities, but not in London. It is concluded that deep-plan, naturally ventilated buildings with sealed facades, if well designed, could maintain thermal comfort in all but a very few UK locations, whilst consuming much less energy than even good practice standards.     

Whole life costing of domestic energy demand reduction technologies: householder perspectives

A recent, major UK research project investigated technical and social aspects of reducing the CO₂ emissions of UK domestic housing by 50% by the year 2030. As 80% of the UK housing stock that will be present in 2030 has already been built, this study aimed to research the whole life costs of three sets of energy demand reduction technologies for existing housing, over a 25‐year period, suitable to deliver significant CO₂ emissions reduction up to 50%. Demand side technological interventions in the form of fabric upgrades and ventilation systems are identified. Whole life cycle analysis of interventions carried out on two housing variants prominent in the domestic stock under different energy price scenarios is carried out using discounted cash flow and compared with the do‐nothing option. The results show that, despite reducing annual energy bills, there is no clear financial case even over a 25‐year horizon for householders to invest in the proposed interventions that contribute to CO₂ emission reduction targets. When discussed with respect to household income and consumption preferences, the results reveal the need for new policy approaches to overcome the financial and non‐financial hurdles for a mass uptake of energy efficient technologies.     

Evaluating the potential impact of global warming on the UAE residential buildings – A contribution to reduce the CO2 emissions

There is significant evidence that the world is warming. The International Panel of Climate Change stated that there would be a steady increase in the ambient temperature during the end of the 21st century. This increase will impact the built environment, particularly the requirements of energy used for air-conditioning buildings. This paper discusses issues related to the potential impact of global warming on air-conditioning energy use in the hot climate of the United Arab Emirates. Al-Ain city was chosen for this study. Simulation studies and energy analysis were employed to investigate the energy consumption of buildings and the most effective measures to cope with this impact under different climate scenarios. The paper focuses on residential buildings and concludes that global warming is likely to increase the energy used for cooling buildings by 23.5% if Al-Ain city warms by 5.9 °C. The net CO₂ emissions could increase at around 5.4% over the next few decades. The simulation results show that the energy design measures such as thermal insulation and thermal mass are important to cope with global warming, while window area and glazing system are beneficial and sensitive to climate change, whereas the shading devices are moderate as a building CO₂ emissions saver and insensitive to global warming.     

Micro wind turbines in the UK domestic sector

The micro-scale wind turbine industry is expanding in the UK with institutional support and UK legislation encouraging the development of numerous companies with a profusion of design options. The application of micro wind turbines in urban environment is encouraged in the UK via a grant scheme which provides a proportion of the initial capital costs. This development is predicated on the assumption that micro wind turbines have the potential to reduce built environment CO₂ emissions. Current methods of estimating the wind speed are reported to over predict by approximately 2.0 m/s. The energy yields of a range of typical micro wind turbines (in the 0.4–2.5 kW size range) were estimated here using two wind speed datasets sited within 1 km of each other recorded with a temporal precision of 10 min. The annual energy yield of a 1.5 kW turbine was found to be 277 kWh and 2541 kWh for the two sites analysed indicating the problem with the current method of yield estimation. Between 33 and 55% of the electricity generated would be exported dependant on the dwelling's electrical demand. For the high yield site, the simple economic payback of this turbine was found to be 26.8 years i.e. beyond the likely life time of the turbine with CO₂ savings of 1093 kg CO₂. The research suggests that this technology does represent a possible route for reducing CO₂ emissions but this is unlikely to be realised unless an adequate method is found for more accurately predicting energy yield at a specific site.     

Quantifying the potential impacts of China's power-sector policies on coal input and CO2 emissions through 2050: A bottom-up perspective

This study evaluates four recent policies for China's power sector—mandatory renewable targets, green dispatch, carbon capture and sequestration development, and coal-fired generation efficiency improvements—and quantifies their energy and carbon dioxide (CO₂) emissions reduction potential through 2050 using bottom-up energy modeling and scenario analysis. We find renewable targets and green dispatch have crucial interlinked impacts on energy and CO₂ emissions that could change the shape and peak year of China's power-sector emissions outlook. Without either renewable targets or green dispatch, coal will likely continue dominating China's power mix and could delay the power-sector CO₂ emissions peak to the late 2030s.     

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.     

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.     

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.     

The life cycle impact of refurbishment packages on residential buildings with different initial thermal conditions

Existing buildings constitute a large portion of the UK’s housing stock. Refurbishment of existing buildings can, therefore, have an important role in achieving the UK government’s CO₂ reduction targets. While building regulations and rating frameworks mainly focus on the improvements of the operational performance of buildings, Life Cycle Analysis is considered to be a more appropriate framework to account for long–term CO₂ savings. This study evaluates a range of retrofit approaches (simple, medium, and deep), in terms of Life Cycle Carbon Footprint applied on a terraced house—one of the most common housing archetypes in London. The initial state of the original building has also been examined assuming three initial states (never refurbished, refurbished in compliance with the 1976 and with the 2000 building regulations). Results showed that for all initial state scenarios, deep retrofit achieved the lowest life cycle carbon emissions, in absolute figures, compared to the simple and medium retrofits. Simple retrofit packages, on the other hand, achieved quick and significant improvements, especially in buildings with poor initial thermal conditions. The study also indicated that retrofit packages applied on highly efficient building fabrics result in longer carbon payback time periods. The study recommends establishing a ‘staggered’ retrofitting approach, which pushes for ‘older building first’ and ‘simple retrofit packages first’, as these gain quick CO₂ savings. Deep retrofit packages and treatment of relatively new buildings should be implemented at a later stage, to push buildings further to Zero–Carbon target.

     

Effects of wood ash fertilization on forest floor greenhouse gas emissions and tree growth in nutrient poor drained peatland forests

Wood ash (3.1, 3.3 or 6.6 tonnes dry weight ha^− 1) was used to fertilize two drained and forested peatland sites in southern Sweden. The sites were chosen to represent the Swedish peatlands that are most suitable for ash fertilization, with respect to stand growth response. The fluxes of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) from the forest floor, measured using opaque static chambers, were monitored at both sites during 2004 and 2005 and at one of the sites during the period 1 October 2007-1 October 2008. No significant (p > 0.05) changes in forest floor greenhouse gas exchange were detected. The annual emissions of CO₂ from the sites varied between 6.4 and 15.4 tonnes ha^− 1, while the CH₄ fluxes varied between 1.9 and 12.5 kg ha^− 1. The emissions of N₂O were negligible. Ash fertilization increased soil pH at a depth of 0-0.05 m by up to 0.9 units (p < 0.01) at one site, 5 years after application, and by 0.4 units (p < 0.05) at the other site, 4 years after application. Over the first 5 years after fertilization, the mean annual tree stand basal area increment was significantly larger (p < 0.05) at the highest ash dose plots compared with control plots (0.64 m² ha^− 1 year^− 1 and 0.52 m² ha^− 1 year^− 1, respectively). The stand biomass, which was calculated using tree biomass functions, was not significantly affected by the ash treatment. The groundwater levels during the 2008 growing season were lower in the high ash dose plots than in the corresponding control plots (p < 0.05), indicating increased evapotranspiration as a result of increased tree growth. The larger basal area increment and the lowered groundwater levels in the high ash dose plots suggest that fertilization promoted tree growth, while not affecting greenhouse gas emissions.     

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.     

Study of operational parameters improvement of natural-gas cogeneration plant in public buildings in Thailand

This paper presents two case studies of performance improvement alternatives. The first one is the 52.5 MWe cogeneration plant at the Suvarnabhumi Airport, and the second is the 9.9 MWe cogeneration plant of the government office building complex. Both plants are located in Bangkok. Performance improvements assume changing system design and operational plans during on-peak and off-peak periods with applying chilled water storage for more flexible operation. Such analysis gives opportunity for improvement of plant efficiency, primary energy saving, emission reduction and economical benefits. In case study 1, the selection of new prime mover results in overall efficiency improvement from 48% to 61%, 24% increase of primary energy saving, and 27% improvement of CO₂ emission reduction. Significant amount of primary energy is saved 1451 TJ/a and CO₂ emission reduction is 129,271 tCO₂/a. The profit is increased to 24.80 Million US$/a and the payback period is 4.77 years. In case study 2, the application of chilled water storage leads to maximum profit of 2.63 Million US$/a. The results show that the selection of plant components should be made very carefully in the design stage, as well as that permanent control and optimization of plant operation in the exploitation phase is essential. Economic aspects of cogeneration plants are more sensitive to changeable input parameters than classical separate heat and power generation since cogeneration plants are more complex in the aspects of process configuration and products costs/values (electricity, steam, hot water, and chilled water). Having in mind the future development of the natural gas distribution network in Thailand, it can be estimated that the potential of power generation in public buildings is around 1.3 GWe. Comparing the Thailand total primary energy supply for commercial buildings, it means reduction of about 9.1%.     

The environmental impact of stock market capitalization and energy transition: Natural resource dynamics and international trade

This paper examines the effect of stock market capitalization and energy transition on the environment between 1994 and 2020, considering the roles of economic growth, natural resources, and international trade in Asian countries. The results indicate that stock market capitalization, energy transition, and natural resources reduce CO₂ emissions. International trade and economic growth are positively associated with CO₂ emissions. There is a suggestion that the government should encourage companies to determine the material business risks they face. Aside from traditional risks related to operations, technology, and the market, climate change-related risks should likewise be considered significant.     

Saturation, energy consumption, CO2 emission and energy efficiency from urban and rural households appliances in Mexico

Energy usage and energy efficiency are of increasing concern in Mexico, electricity generation principally depends upon fossil fuels. On one hand, the stocks of these fuels have been confirmed to be critically limited. On the other hand, in process of electricity generation by means of these fuels, a number of poisonous by-products adversely affect the conservation of natural eco-system.This paper focuses on estimation of energy consumption, energy savings, reduction of emissions of CO₂ for use of urban and rural household appliances in Mexico between 1996 and 2021.The analysis concentrates on six major energy end uses in the residential sector: refrigerators, air conditioners, washing machines, TV set, iron and heater.It is estimated that by 2021 there will be a cumulative saving of 22,605 GWh, as a result of the implementation of government programs on energy efficiency that represents a cumulative reduction of CO2 emissions of 15,087 Tg CO2.It means that Mexico can reduce in 5650 MW the generation capacity of national electricity system, which is to avoid burning 40.35 MM barrels of oil.The findings can be useful to policy makers as well as household appliances users.     

STEMS-Air: a simple GIS-based air pollution dispersion model for city-wide exposure assessment

Current methods of air pollution modelling do not readily meet the needs of air pollution mapping for short-term (i.e. daily) exposure studies. The main limiting factor is that for those few models that couple with a GIS there are insufficient tools for directly mapping air pollution both at high spatial resolution and over large areas (e.g. city wide). A simple GIS-based air pollution model (STEMS-Air) has been developed for PM₁₀ to meet these needs with the option to choose different exposure averaging periods (e.g. daily and annual). STEMS-Air uses the grid-based FOCALSUM function in ArcGIS in conjunction with a fine grid of emission sources and basic information on meteorology to implement a simple Gaussian plume model of air pollution dispersion. STEMS-Air was developed and validated in London, UK, using data on concentrations of PM₁₀ from routinely available monitoring data. Results from the validation study show that STEMS-Air performs well in predicting both daily (at four sites) and annual (at 30 sites) concentrations of PM₁₀. For daily modelling, STEMS-Air achieved r² values in the range 0.19-0.43 (p < 0.001) based solely on traffic-related emissions and r² values in the range 0.41-0.63 (p < 0.001) when adding information on ‘background’ levels of PM₁₀. For annual modelling of PM₁₀, the model returned r² in the range 0.67-0.77 (P < 0.001) when compared with monitored concentrations. The model can thus be used for rapid production of daily or annual city-wide air pollution maps either as a screening process in urban air quality planning and management, or as the basis for health risk assessment and epidemiological studies.     

Debating the future of comfort: environmental sustainability,energy consumption and the indoor environment

Vast quantities of energy are consumed in heating and cooling to provide what are now regarded as acceptable standards of thermal comfort. In the UK as in a number of other countries, there is a real danger that responses in anticipation of global warming and climate change – including growing reliance on air-conditioning – will increase energy demand and CO₂ emissions even further. This is an appropriate moment to reflect on the history and future of comfort, both as an idea and as a material reality. Based on interviews and discussions with UK policy makers and building practitioners involved in specifying and constructing what will become the indoor environments of the future, four possible scenarios are identified each with different implications for energy and resource consumption. By actively promoting debate about the indoor environment and associated ways of life, it may yet be possible to avoid becoming locked into social and technical trajectories that are ultimately unsustainable. The aim of this paper is to inspire and initiate just such a discussion through demonstrating that comfort is a highly negotiable socio-cultural construct.     

Effects of experimental CO2 leakage on solubility and transport of seven trace metals in seawater and sediment

The impact of CO₂ leakage on solubility and distribution of trace metals in seawater and sediment has been studied in lab scale chambers. Seven metals (Al, Cr, Ni, Pb, Cd, Cu, and Zn) were investigated in membrane-filtered seawater samples, and DGT samplers were deployed in water and sediment during the experiment. During the first phase (16 days), “dissolved” (< 0.2 µm) concentrations of all elements increased substantially in the water. The increase in dissolved fractions of Al, Cr, Ni, Cu, Zn, Cd and Pb in the CO₂ seepage chamber was respectively 5.1, 3.8, 4.5, 3.2, 1.4, 2.3 and 1.3 times higher than the dissolved concentrations of these metals in the control. During the second phase of the experiment (10 days) with the same sediment but replenished seawater, the dissolved fractions of Al, Cr, Cd, and Zn were partly removed from the water column in the CO₂ chamber. DNi and DCu still increased but at reduced rates, while DPb increased faster than that was observed during the first phase. DGT-labile fractions (Me_DGT) of all metals increased substantially during the first phase of CO₂ seepage. DGT-labile fractions of Al, Cr, Ni, Cu, Zn, Cd and Pb were respectively 7.9, 2.0, 3.6, 1.7, 2.1, 1.9 and 2.3 times higher in the CO₂ chamber than that of in the control chamber. Al_DGT, Cr_DGT, Ni_DGT, and Pb_DGT continued to increase during the second phase of the experiment. There was no change in Cd_DGT during the second phase, while Cu_DGT and Zn_DGT decreased by 30% and 25%, respectively in the CO₂ chamber. In the sediment pore water, DGT labile fractions of all the seven elements increased substantially in the CO₂ chamber. Our results show that CO₂ leakage affected the solubility, particle reactivity and transformation rates of the studied metals in sediment and at the sediment-water interface. The metal species released due to CO₂ acidification may have sufficiently long residence time in the seawater to affect bioavailability and toxicity of the metals to biota.