The limited potential of soil and vegetation in urban greenspace for nature-based offsetting of institutional carbon emissions

\ua9 2024 The Author(s). Soil Use and Management published by John Wiley & Sons Ltd on behalf of British Society of Soil Science.The soil and vegetation of urban greenspace can potentially contribute to ambitious climate action plans declared by city institutions and councils. To assess how urban greenspace could make a contribution to institutional carbon management, we measured soil carbon at 42 sampling locations across three land-covers and vegetation carbon of 490 trees (67 species), over the city campus of Newcastle University. Soil carbon varied with pH and land-cover classes (lawned with some free-standing trees, woodland park, sports fields), and tree cover significantly enhanced soil carbon storage. Soil carbon storage from 0 to 30 cm depth averaged 18.85 kg\ub7m−2, more than double the tree carbon storage (average 7.66 kg\ub7m−2) estimated using biomass empirical equations. According to our scenarios, even if all currently available urban greenspace were converted to woodland, this would offset only 1% of current annual greenhouse gas emissions of Newcastle University or, if implemented more widely, of Newcastle city overall. While urban woodland brings benefits beyond carbon storage, the limit to what can be achieved within cities emphasizes the need for urban–rural partnerships. In exchange for helping cities with carbon abatement, their surrounding rural regions could benefit from carbon offsetting payments to improve their infrastructure provision. Overall, a carbon-friendly and nature-based land management strategy should be developed with full consideration of collaborative partnerships between urban and surrounding rural areas, particularly placing a high value on soil and tree carbon

Soil carbon management and enhanced rock weathering: The separate fates of organic and inorganic carbon

\ua9 2024 The Author(s). European Journal of Soil Science published by John Wiley & Sons Ltd on behalf of British Society of Soil Science.Soil carbon (C) management has been promoted as one of the few readily available strategies to mitigate the rising concentration of atmospheric CO2 and its associated impacts on climate change. One of these carbon management strategies is enhanced rock weathering (ERW) which involves adding crushed silicate rocks to the soil. These rocks weather and remove atmospheric CO2 by converting it into bicarbonate in solution. The approach requires careful interpretation of the differences between soil organic carbon (SOC) and soil inorganic carbon (SIC) and their measurement, with implications for land management and C credit accounting. In this Opinion, we emphasise the distinct nature and fates of SOC and SIC, advocating for their separate management, particularly in C credit schemes. It is imperative that protocols for soil C management explicitly recognise the difference between SOC and SIC to prevent any ambiguity. Farmers should be able to claim credits for increases in SOC alongside and independently of any claim for credits for ERW (i.e. SIC). Despite the potential of ERW for C removal, we emphasise that further research is needed to improve the measurement and monitoring of SIC and to understand ERW\u27s potential implications for SOC turnover and greenhouse gas emissions. Highlights: Enhanced Rock Weathering increases dissolved inorganic carbon (bicarbonate). Soil organic carbon (SOC) may be influenced by Enhanced Rock Weathering. Carbon credit via Enhanced Rock Weathering is separate from credit linked to soil organic carbon. Soil organic matter and enhanced rock weathering both have roles to play for carbon credits

The Impact and Design of the MDGs: Some Reflections

The MDGs appear to have been more influential than most other attempts at international target?setting in the field of development, at least at the level of international discourse. But has this translated into impact on either development policy or resource allocation, and if so has the impact been constructive or not? And what lessons does this suggest for any future target?setting proposals

A Sustainability Framework for Engineering Carbon Capture Soil In Transport Infrastructure

Recent research has demonstrated considerable potential for artificial soils to be designed for carbon capture. The incorporation of quarry fines enables the accumulation of atmospheric CO2 in newly formed carbonate minerals. However, the rate and trajectory of carbon accumulation has been little studied. The relative contribution of biotic (e.g. vegetation, micro-organisms) and abiotic (water, light, temperature) factors to the carbonation process is also unknown. This article presents a sustainability framework which aims to determine the multi-functionality of soils to which fines have been added not only in their role as carbon sinks but also in their role of providing additional opportunities for improvement to ecosystem services. Such frameworks are required specifically where land designed for CO2 capture must also provide other ecosystem services, such as flood mitigation and biodiversity conservation. land within linear transport infrastructure provides a case study, focusing on 238,000 ha of vegetated land associated with roadside verges in the UK. Hypothetically this area could remove 2.5 t CO2 per year from the atmosphere, equivalent to 1% 2011 total UK emissions or 2% of current transport emissions and saving an equivalent of £1.1 billion in non-traded mitigation values. roadside verges should be designed to minimize flooding onto the highway and perform other important functions such as removal of dust and suspended solids from surface waters. Vegetation on 30,000 ha of railway land also provides opportunities for carbon sequestration, but management of this vegetation is subject to similar constraints to protect the rail tracks from debris extending from autumn leaves to fallen trees

Identification of the Mechanism of Electrocatalytic Ozone Generation on Ni/Sb-SnO2

This paper reports a systematic study of the codoping of SnO2with Sb and Ni to identify the mechanism responsible for the electrocatalytic generation of ozone on Ni/Sb-SnO2. On the basis of interpretation of a combination of X-ray diffraction, BET surface area measurements (N2), and thermal analysis, the formation of ozone appears to take place on particle surfaces of composite Sb-SnO2grains and is controlled by diffusion of OH along internal crystallite surfaces within the grain. Sb-doped SnO2is inactive with respect to ozone evolution in the absence of Ni, demonstrating a synergic interaction between nickel and antimony. From X-ray photoelectron spectroscopy (XPS) investigations, Sb(V) ions substitute for Sn(IV) in the lattice with a preference for centrosymmetric coordination sites, while the Sb(III) ions occur at grain surfaces or boundaries. Ni was not detected by XPS, being located in the subsurface region at concentrations below the detection limit of the instrument. In addition to identification of a possible mechanism for ozone formation, the study resulted in the production of active nanopowders which will allow the fabrication of high-surface-area anodes with the potential to exceed the space-time yields of β-PbO2anodes, permitting the application the Ni/Sb-SnO2anodes in the treatment of real waters

Equipping for risk: Lessons learnt from the UK shale-gas experience on assessing environmental risks for the future geoenergy use of the deep subsurface

\ua9 2024 The Authors. Summary findings are presented from an investigation to improve understanding of the environmental risks associated with developing an unconventional-hydrocarbons industry in the UK. The EQUIPT4RISK project, funded by UK Research Councils, focused on investigations around Preston New Road (PNR), Fylde, Lancashire, and Kirby Misperton Site A (KMA), North Yorkshire, where operator licences to explore for shale gas by hydraulic fracturing (HF) were issued in 2016, although exploration only took place at PNR. EQUIPT4RISK considered atmospheric (greenhouse gases, air quality), water (groundwater quality) and solid-earth (seismicity) compartments to characterise and model local conditions and environmental responses to HF activities. Risk assessment was based on the source-pathway-receptor approach. Baseline monitoring of air around the two sites characterised the variability with meteorological conditions, and isotopic signatures were able to discriminate biogenic methane (cattle) from thermogenic (natural-gas) sources. Monitoring of a post-HF nitrogen-lift (well-cleaning) operation at PNR detected the release of atmospheric emissions of methane (4.2 \ub1 1.4 t CH4). Groundwater monitoring around KMA identified high baseline methane concentrations and detected ethane and propane at some locations. Dissolved methane was inferred from stable-isotopic evidence as overwhelmingly of biogenic origin. Groundwater-quality monitoring around PNR found no evidence of HF-induced impacts. Two approaches for modelling induced seismicity and associated seismic risk were developed using observations of seismicity and operational parameters from PNR in 2018 and 2019. Novel methodologies developed for monitoring include use of machine learning to identify fugitive atmospheric methane, Bayesian statistics to assess changes to groundwater quality, a seismicity forecasting model seeded by the HF-fluid injection rate and high-resolution monitoring of soil-gas methane. The project developed a risk-assessment framework, aligned with ISO 31000 risk-management principles, to assess the theoretical combined and cumulative environmental risks from operations over time. This demonstrated the spatial and temporal evolution of risk profiles: seismic and atmospheric impacts from the shale-gas operations are modelled to be localised and short-lived, while risk to groundwater quality is longer-term

Transport of Pb and Zn by carboxylate complexes in basinal ore fluids and related petroleum-field brines at 100°C: the influence of pH and oxygen fugacity

It is well established through field observations, experiments, and chemical models that oxidation (redox) state and pH exert a strong influence on the speciation of dissolved components and the solubility of minerals in hydrothermal fluids. log [Image: see text] –pH diagrams were used to depict the influence of oxygen fugacity and pH on monocarboxylate- and dicarboxylate-transport of Pb and Zn in low-temperature (100°C) hydrothermal ore fluids that are related to diagenetic processes in deep sedimentary basins, and allow a first-order comparison of Pb and Zn transport among proposed model fluids for Mississippi Valley-type (MVT) and red-bed related base metal (RBRBM) deposits in terms of their approximate pH and [Image: see text] conditions. To construct these diagrams, total Pb and Zn concentrations and Pb and Zn speciation were calculated as a function of log [Image: see text] and pH for a composite ore-brine with concentrations of major elements, total sulfur, and total carbonate that approximate the composition of MVT and RBRBM model ore fluids and modern basinal brines. In addition to acetate and malonate complexation, complexes involving the ligands Cl(-), HS(-), H(2)S, and OH(- )were included in the model of calculated total metal concentration and metal speciation. Also, in the model, Zn and Pb are competing with the common-rock forming metals Ca, Mg, Na, Fe, and Al for the same ligands. Calculated total Pb concentration and calculated total Zn concentration are constrained by galena and sphalerite solubility, respectively. Isopleths, in log [Image: see text] –pH space, of the concentration of Pb and concentration of Zn in carboxylate (acetate + malonate) complexes illustrate that the oxidized model fluids of T. H. Giordano (in Organic Acids in Geological Processes, ed. E. D. Pittman and M. D. Lewan, Springer-Verlag, New York, 1994, pp. 319–354) and G. M. Anderson (Econ. Geol., 1975, 70, 937–942) are capable of transporting sufficient amounts of Pb (up to 10 ppm) and Zn (up to 100 ppm) in the form of carboxylate complexes to form economic deposits of these metals. On the other hand, the reduced ore fluid models of D. A. Sverjensky (Econ. Geol., 1984, 79, 23–37) and T. H. Giordano and H. L. Barnes (Econ. Geol., 1981, 76, 2200–2211) can at best transport amounts of Pb and Zn, as carboxylate complexes, that are many orders of magnitude below the 1 to 10 ppm minimum required to form economic deposits. Lead and zinc speciation (mol% of total Pb or Zn) in the model ore fluid was calculated at specific log [Image: see text] –pH conditions along the 100, 0.01, and 0.001 ppm total Pb and total Zn isopleths. Along the 100 ppm isopleth conditions are oxidized (∑SO(4 )>> ∑H(2)S) with Pb and Zn predominantly in the form of chloride complexes under acid to mildly alkaline conditions (pH from 3 to approximately 7.5), while hydroxide complexes dominate Pb and Zn speciation under more alkaline conditions. Sulfide complexes are insignificant under these oxidized conditions. For more reduced conditions along the 0.01 and 0.001 ppm isopleths chloride complexes dominate Pb and Zn speciation in the SO(4)(2- )field and near the SO(4)(2-)-reduced sulfur boundary from pH = 4 to approximately 7.5, while hydroxide complexes dominate Pb and Zn speciation under alkaline conditions above pH = 7.5 in the SO(4)(2- )field. In the most reduced fluids (∑H(2)S >> ∑SO(4)) along the 0.01 and 0.001 isopleths, sulfide complexes account for almost 100% of the Pb and Zn in the model fluid. Acetate (monocarboxylate) complexation is significant only under conditions of chloride and hydroxide complex dominance and its effect is maximized in the pH range 5 to 7, where it complexes 2 to 2.6% of the total Pb and 1 to 1.25% of the total Zn. Malonate (dicarboxylate) complexes are insignificant along all isopleths. The speciation results from this study show that deep formation waters characterized by temperatures near 100°C, high oxidation states and ∑H(2)S < 0.03 mg L(-1 )([Image: see text] < 10(-6)), high chlorinities (~ 100000 mg L(-1)), and high but reasonable concentrations of carboxylate anions can mobilize up to 3% of the total Pb and up to 1.3% of the total Zn as carboxylate complexes. Furthermore, these percentages, under the most favorable conditions, correspond to approximately 1 to 100 ppm of these metals in solution; concentrations that are adequate to form economic deposits of these metals. However, the field evidence suggests that all of these optimum conditions for carboxylate complexation are rarely met at the same time. A comparison of the composite ore fluid compositions from this study and modern brine data shows that the ore brines, corresponding to log [Image: see text] –pH conditions based on the Anderson (1975) and Giordano (1994) model fluids, are similar in many respects to modern, high trace-metal petroleum-field brines. The principal differences between modern high trace-metal brines and the composite ore fluids of Anderson (1975) and Giordano (1994) relate to their carboxylate anion content. The reported concentrations of monocarboxylate anions (∑monocbx) and dicarboxylate anions (Edicbx) in high trace-metal petroleum-field brines (< 1 to 300 mg L(-1 )and < 1 mg L(-1), respectively) are significantly lower than the concentrations assumed in the modelled brines of this study (∑monocbx = 7 700 mg L(-1 )and ∑dicbx = 300 mg L(-1)). There are also major differences in the corresponding total chloride to carboxylate ratio (∑m(Cl)/∑m(cbx)) and monocarboxylate to dicarboxylate ratio (∑m(monocbx)/∑m(dicbx)). Modern high trace-metal brines have much higher ∑m(Cl)/∑m(cbx )values and, therefore, the contribution of carboxylate complexes to the total Pb and Zn content in these modern brines is likely to be significantly less than the 1 to 3 percent for the composite ore fluids of Anderson (1975) and Giordano (1994). The composite ore-brine based on the Giordano and Barnes (1981) MVT ore fluid is comparable to the high salinity (> 170 000 mg L(-1 )TDS) subset of modern brines characterized by low trace-metal content and high total reduced sulfur (∑H(2)S). A comparison of the Sverjensky (1984) composite ore-brine with modern petroleum-field brines in terms of ∑H(2)S and Zn content, reveals that this ore fluid corresponds to a "border-type" brine, between modern high trace-metal brines and those with low trace-metal content and high ∑H(2)S. A brine of this type is characterized by values of ∑H(2)S, ∑Zn, and/or ∑Pb within or near the 1 to 10 mg L(-1 )range. Based on brine-composition data from numerous references cited in this paper, border-type brines do exist but are rare. The model results and field evidence presented in this study are consistent with other chemical simulation studies of carboxylate complexation in modern petroleum-field brines. Thus, it appears that carboxylate complexation plays a minor, if not insignificant, role as a transport mechanism for Pb and Zn in high salinity Na–Cl and Na–Ca–Cl basinal brines and related ore fluids