Measurements show that marginal wells are a disproportionate source of methane relative to production

ABSTRACT

Oil and natural gas wells are a prominent source of the greenhouse gas methane (CH₄), but most measurements are from newer, high producing wells. There are nearly 700,000 marginal “stripper” wells in the US, which produce less than 15 barrels of oil equivalent (BOE) d^?1. We made direct measurements of CH₄ and volatile organic carbon (VOC) emissions from marginal oil and gas wells in the Appalachian Basin of southeastern Ohio, all producing < 1 BOE d^?1. Methane and VOC emissions followed a skewed distribution, with many wells having zero or low emissions and a few wells responsible for the majority of emissions. The average CH₄ emission rate from marginal wells was 128 g h^?1 (median: 18 g h^?1; range: 0– 907 g h^?1). Follow-up measurements at five wells indicated high emissions were not episodic. Some wells were emitting all or more of the reported gas produced at each well, or venting gas from wells with no reported gas production. Measurements were made from wellheads only, not tanks, so our estimates may be conservative. Stochastic processes such as maintenance may be the main driver of emissions. Marginal wells are a disproportionate source of CH₄ and VOCs relative to oil and gas production. We estimate that oil and gas wells in this lowest production category emit approximately 11% of total annual CH₄ from oil and gas production in the EPA greenhouse gas inventory, although they produce about 0.2% of oil and 0.4% of gas in the US per year.

Implications: Low producing marginal wells are the most abundant type of oil and gas well in the United States, and a surprising number of them are venting all or more of their reported produced gas to the atmosphere. This makes marginal wells a disproportionate greenhouse gas emissions source compared to their energy return, and a good target for environmental mitigation.     

Potential interferences in photolytic nitrogen dioxide converters for ambient air monitoring: Evaluation of a prototype

ABSTRACT

Mixing ratios of the criteria air contaminant nitrogen dioxide (NO₂) are commonly quantified by reduction to nitric oxide (NO) using a photolytic converter followed by NO-O₃ chemiluminescence (CL). In this work, the performance of a photolytic NO₂ converter prototype originally designed for continuous emission monitoring and emitting light at 395 nm was evaluated. Mixing ratios of NO₂ and NO_x (= NO + NO₂) entering and exiting the converter were monitored by blue diode laser cavity ring-down spectroscopy (CRDS). The NO₂ photolysis frequency was determined by measuring the rate of conversion to NO as a function of converter residence time and found to be 4.2 s^?1. A maximum 96% conversion of NO₂ to NO over a large dynamic range was achieved at a residence time of (1.5 ± 0.3) s, independent of relative humidity. Interferences from odd nitrogen (NO_y) species such as peroxyacyl nitrates (PAN; RC(O)O₂NO₂), alkyl nitrates (AN; RONO₂), nitrous acid (HONO), and nitric acid (HNO₃) were evaluated by operating the prototype converter outside its optimum operating range (i.e., at higher pressure and longer residence time) for easier quantification of interferences. Four mechanisms that generate artifacts and interferences were identified as follows: direct photolysis, foremost of HONO at a rate constant of 6% that of NO₂; thermal decomposition, primarily of PAN; surface promoted photochemistry; and secondary chemistry in the connecting tubing. These interferences are likely present to a certain degree in all photolytic converters currently in use but are rarely evaluated or reported. Recommendations for improved performance of photolytic converters include operating at lower cell pressure and higher flow rates, thermal management that ideally results in a match of photolysis cell temperature with ambient conditions, and minimization of connecting tubing length. When properly implemented, these interferences can be made negligibly small when measuring NO₂ in ambient air.

Implications: A new near-UV photolytic converter for measurement of the criteria pollutant nitrogen dioxide (NO₂) in ambient air by CL was characterized. Four mechanisms that generate interferences were identified and investigated experimentally: direct photolysis of HONO which occurred at a rate constant 6% that of NO₂, thermal decomposition of PAN and N₂O₅, surface promoted chemistry involving HNO₃, and secondary chemistry involving NO in the tubing connecting the converter and CL analyzer. These interferences are predicted to occur in all NO₂ P-CL systems but can be avoided by appropriate thermal management and operating at high flow rates.     

Extrapolating cetacean densities to quantitatively assess human impacts on populations in the high seas

As human activities expand beyond national jurisdictions to the high seas, there is an increasing need to consider anthropogenic impacts to species inhabiting these waters. The current scarcity of scientific observations of cetaceans in the high seas impedes the assessment of population‐level impacts of these activities. We developed plausible density estimates to facilitate a quantitative assessment of anthropogenic impacts on cetacean populations in these waters. Our study region extended from a well‐surveyed region within the U.S. Exclusive Economic Zone into a large region of the western North Atlantic sparsely surveyed for cetaceans. We modeled densities of 15 cetacean taxa with available line transect survey data and habitat covariates and extrapolated predictions to sparsely surveyed regions. We formulated models to reduce the extent of extrapolation beyond covariate ranges, and constrained them to model simple and generalizable relationships. To evaluate confidence in the predictions, we mapped where predictions were made outside sampled covariate ranges, examined alternate models, and compared predicted densities with maps of sightings from sources that could not be integrated into our models. Confidence levels in model results depended on the taxon and geographic area and highlighted the need for additional surveying in environmentally distinct areas. With application of necessary caution, our density estimates can inform management needs in the high seas, such as the quantification of potential cetacean interactions with military training exercises, shipping, fisheries, and deep‐sea mining and be used to delineate areas of special biological significance in international waters. Our approach is generally applicable to other marine taxa and geographic regions for which management will be implemented but data are sparse.     

National contributions to global ecosystem values

Current conservation templates prioritize biogeographic regions with high intensity ecosystem values, such as exceptional species richness or threat. Intensity-based targets are an important consideration in global efforts, but they do not capture all available opportunities to conserve ecosystem values, including those that accrue in low intensity over large areas. We assess six globally-significant ecosystem values—intact wilderness, freshwater availability, productive marine environments, breeding habitat for migratory wildlife, soil carbon storage, and latitudinal potential for range shift in the face of climate change—to highlight opportunities for high-impact broadly-distributed contributions to global conservation. Nations can serve as a cohesive block of policy that can profoundly influence conservation outcomes. Contributions to global ecosystem values that exceed what is predicted by a nation's area alone, can give rise to countries with the capacity to act as ‘conservation superpowers’, such as Canada and Russia. For these conservation superpowers, a relatively small number of national policies can have environmental repercussions for the rest of the world.     

A transformative mission for prioritising nature in Australian cities

Australia is experiencing mounting pressures related to processes of urbanisation, biodiversity loss and climate change felt at large in cities. At the same time, it is cities that can take the leading role in pioneering approaches and solutions to respond to those coupling emergencies. In this perspective piece we respond to the following question: What are the required transformations for prioritising, valuing, maintaining and embracing nature in cities in Australia? We adopt the mission framework as an organising framework to present proposed pathways to transform Australian cities as nature-positive places of the future. We propose three interconnected pathways as starting actions to steer urban planning, policy and governance in Australian cities: First, cities need to establish evidence-based planning for nature in cities and mainstream new planning tools that safeguard and foreground urban nature. Second, collaborative planning needs to become a standard practice in cities and inclusive governance for nature in cities needs to prioritise Aboriginal knowledge systems and practices as well as look beyond what local governments can do. Third, for progressing to nature-positive cities, it is paramount to empower communities to innovate with nature across Australian cities. Whilst we focus on Australian cities, the lessons and pathways are broadly applicably globally and can inspire science-policy debates for the post COP15 biodiversity and COP26 climate change implementation processes.     

Losses and dissipation of penconazole in vineyard soil as affected by mid-row management system

A field experiment was performed with the aim to assess the amount of penconazole losses during field application and the spatial variability of penconazole concentration in a vineyard soil, under two different management techniques (tilled and grass covered). The field dissipation of penconazole under the two techniques was also followed for 114 days, highlighting the effects of spatial variability of the initial concentration and of the grass covering in terms of the different soil metabolic activity. Data found show that a high percentage of penconazole, from 42.5 % to 67.43 %, can reach the soil during the treatments, despite the fact that penconazole is applied to the foliage. The high values of the coefficient of variation for data within rows show considerable variability in all applications, ranging from 30 to 65 in the first application, from 35 to 79 in the second and from 36 to 75 in the third. Since the applications of penconazole occurred under almost same climatic conditions in terms of wind speed and direction, the high variability of concentration of penconazole found within mid-rows was attributed to the uneven slope of the vineyard causing an irregular speed of the sprayer equipment. However, least significant differences of the mean values did not end in a significant difference of penconazole concentration among mid-rows for all applications, indicating that the variability between rows does not contribute to the overall variability. The calculated half-life values for penconazole in tilled soil were 62.4 days for tilled and 33.0 for grassed soil, highlighting the tendency of penconazole to faster dissipate in grassed than in tilled soil. Grassed soil was characterised by a higher metabolic activity in terms of microbial biomass carbon content, basal respiration and total hydrolytic activity, than tilled soil. A significant correlation between penconazole dissipation and total hydrolytic activity, was found. The faster dissipation of penconazole in grassed soil was attributed to the higher amount of the total hydrolytic activity which, in grassed soil, was 1.5 fold-higher than in tilled soil.     

Monuments as sampling surfaces of recent traffic pollution

Background, aim and scope  

A new approach towards monuments, considering them as a passive sampler of pollution, is presented. Cultural Heritage objects suffer daily the damages of environmental pollution, especially in those areas interested by heavy traffic. Since monuments undergo only periodic conservation or maintenance works, surfaces are able to accumulate atmospheric deposit and to record changes in its composition. An optimised analytical protocol was developed in order to quantify platinum and rhodium at trace level on surfaces. The two elements have become tracers of automobile emissions in recent years, since the introduction of catalytic converters, and could have catalytic effects on the decay reactions of natural and artificial stone materials. As a first case study, the cement mortar surfaces of a twentieth century monument, the Camerlata Fountain, in Como (Italy) were investigated.     

PCDD/F and dioxin-like PCB profiles in soils amended with sewage sludge,compost, farmyard manure,and mineral fertilizer since 1962

Background, aim, and scope  

Biowaste contains compounds of agricultural value such as organic carbon, nutrients, and trace elements and can partially replace mineral fertilizer (MIN) and improve the physical properties of the soil. However, the obvious benefits of land spreading need to be carefully evaluated against potential adverse effects on the environment and human health. Environmental contamination resulting from biowaste application is one of the key variables when assessing cost/benefits. This study provides data on the resulting concentration of polychlorinated dibenzodioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in the soil column as a result of the different types of fertilizers.     

Biochemical and locomotor responses of Carcinus maenas exposed to the serotonin reuptake inhibitor fluoxetine

The aim of this study was to assess the effects of the widely used anti-depressant fluoxetine on behaviour (locomotion), moulting, neuromuscular transmission, energy production and anti-oxidant defences’ efficiency of the epibenthic crab Carcinus maenas. Crabs were individually exposed to fluoxetine concentrations for 7 d. Effects on locomotion were assessed at the end of the exposure using an open field test adapted to C. maenas in the present study. Tissue samples were later collected to evaluate fluoxetine effects on physiological functions using the activity of key enzymes and other parameters as biomarkers, namely: N-acetyl-β-glucosaminidase (NAGase) in the epidermis (moulting) and the hepatopancreas; cholinesterases (ChE) in muscle (neuromuscular cholinergic transmission); NADP⁺-dependent isocitrate dehydrogenase (IDH) and lactate dehydrogenease (LDH) in muscle (energy production); glutathione S-transferases (GST) in hepatopancreas (biotransformation and oxidative stress system); glutathione reductase (GR), and glutathione peroxidade (GPx), total glutathione levels (TG) and lipid peroxidation levels in the hepatopancreas (anti-oxidant defences and oxidative damage). Because no information on C. maenas NAGase activity was previously available, its variation during the moult cycle was also investigated. The results showed that locomotion was significantly increased at fluoxetine concentrations equal or above 120 μg L⁻¹, with animals spending more time moving, walking longer distances than controls. Levels of NAGase activity were found to vary in relation to C. maenas moult cycle, but no alterations were observed after exposure to fluoxetine. Significant increases in the activity of ChE, GST and GR enzymes, and the levels of TG were found, with a lowest observed effect concentration (LOEC) of 120 μg L⁻¹. Effects on locomotion were significantly and positively correlated to those induced on ChE activity. The results raise concern when hypothesising conditions of chronic exposure in the wild.     

Assessment of the environmental fate and effects of the PPARgamma receptor agonist, pioglitazone

The environmental fate and effects of pioglitazone prescribed for the treatment of type 2 diabetes were evaluated in an environmental risk assessment following the European Medicines Agency (EMA) "Guideline on the Environmental Risk Assessment of Medicinal Products for Human Use"; EMEA/CHMP/SWP/4447/00. A predicted environment concentration (PEC) for surface water was estimated at 0.023μgL(-1), (action limit of 0.01μgL(-1)) triggering a comprehensive battery of laboratory evaluations. Pioglitazone and its major metabolites were determined not to significantly adsorb to sewage solids, were not persistent in the aquatic environment, did not bioaccumulate and were non-toxic to aquatic organisms. Pioglitazone does not pose an unacceptable risk to groundwater supplies, with concentrations not anticipated to be a risk to aquatic organisms or human drinking water supplies. Pioglitazone does not pose a risk of secondary poisoning.