Current understanding of the ecological risk of mercury from subsea oil and gas infrastructure to marine ecosystems

Many oil and gas fields are nearing production cessation and will require decommissioning, with the preferred method being complete infrastructure removal in most jurisdictions. However, decommissioning in situ, leaving some disused components in place, is an option that may be agreed to by the regulators and reservoir titleholders in some circumstances. To understand this option's viability, the environmental impacts and risks of any residual contaminants assessed. Mercury, a contaminant of concern, is naturally present in hydrocarbon reservoirs, may contaminate offshore processing and transmission infrastructure, and can biomagnify in marine ecosystems. Mercury's impact is dependent on its speciation, concentration, and the exposure duration. However, research characterising and quantifying the amount of mercury in offshore infrastructure and the efficacy of decontamination is limited. This review describes the formation of mercury-contaminated products within oil and gas infrastructure, expected exposure pathways after environmental release, possible impacts, and key research gaps regarding the ecological risk of in situ decommissioned contaminated infrastructure. Suggestions are made to overcome these gaps, improving the in situ mercury quantification in infrastructure, understanding environmental controls on, and forecasting of, mercury methylation and bioaccumulation, and the cumulative impacts of multiple stressors within decommissioned infrastructures.

Sensitive determination of bioaccessible mercury in complex matrix samples by combined photochemical vapor generation and solid phase microextraction coupled with microwave induced plasma optical emission spectrometry

The photochemical generation technique of mercury vapor (PCVG) coupled with headspace solid phase microextraction (SPME) and microwave induced plasma optical emission spectrometry (MIP-OES) has been developed and successfully applied for fast and sensitive determination of mercury in complex matrix samples. Mercury vapor was generated by UV photo-reduction of inorganic mercury and methylmercury to mercury vapor in 5% (v/v) formic acid with subsequent gas-liquid separation and preconcentration by solid phase microextraction. A stopped-flow mode of the PCVG-SPME unit was employed with the aim of increasing analyte preconcentration factor, thus improving both sensitivity of determination and detection limits for mercury. The calibration curves were linear up to 20 ng mL^-1 with the limit of detection for inorganic mercury and methylmercury of 0.030 and 0.045 ng mL^-1, respectively. This manifold allowed a repeatability, expressed as relative standard deviation, of below 5%. Due to differences in efficiency of Hg vapor generation for Hg²⁺ and CH₃Hg⁺, the quantification was performed against external Hg²⁺ and CH₃Hg⁺ aqueous standards, respectively. The method was validated by the analysis of two CRM materials of different matrix composition, i.e. estuarine sediment ERM CC580 for total mercury content and tuna fish ERM CE464 for methylmercury content, respectively. The results proved good accuracy of the method with recovery of 101% total mercury and 87.3% methylmercury and precision of 3.8% and 12.5%, respectively. Effect of concomitants in the stopped-flow generation of mercury vapor with the new manifold was also investigated. Next, the proposed method was successfully applied for monitoring of bioaccessible fraction of mercury during their incubation in simulated body fluid in the presence of selenium nanoparticles examined as a potential mercury detoxifying agent.

Mercury in natural gas streams: A review of materials and processes for abatement and remediation

The role of natural gas in mitigating greenhouse gas emissions and advancing renewable energy resource integration is undoubtedly critical. With the progress of hydrocarbons exploration and production, the target zones become deeper and the possibility of mercury contamination increases. This impacts on the industry from health and safety risks, due to corrosion and contamination of equipment, to catalyst poisoning and toxicity through emissions to the environment. Especially mercury embrittlement, being a significant problem in LNG plants using aluminum cryogenic heat exchangers, has led to catastrophic plant incidents worldwide. The aim of this review is to critically discuss the conventional and alternative materials as well as the processes employed for mercury removal during gas processing. Moreover, comments on studies examining the geological occurrence of mercury species are included, the latest developments regarding the detection, sampling and measurement are presented and updated information with respect to mercury speciation and solubility is displayed. Clean up and passivation techniques as well as disposal methods for mercury-containing waste are also explained. Most importantly, the environmental as well as the health and safety implications are addressed, and areas that require further research are pinpointed.

Speciation of Mercury in Selected Areas of the Petroleum Value Chain

Petroleum, natural gas, and natural gas condensate can contain low levels of mercury (Hg). The speciation of Hg can affect its behavior during processing, transport, and storage so efficient and safe management of Hg requires an understanding of its chemical form in oil, gas and byproducts. Here, X-ray absorption spectroscopy was used to determine the Hg speciation in samples of solid residues collected throughout the petroleum value chain including stabilized crude oil residues, sediments from separation tanks and condensate glycol dehydrators, distillation column pipe scale, and biosludge from wastewater treatment. In all samples except glycol dehydrators, metacinnabar (β-HgS) was the primary form of Hg. Electron microscopy on particles from a crude sediment showed nanosized (<100 nm) particles forming larger aggregates, and confirmed the colocalization of Hg and sulfur. In sediments from glycol dehydrators, organic Hg(SR)₂ accounted for ∼60% of the Hg, with ∼20% present as β-HgS and/or Hg(SR)₄ species. β-HgS was the predominant Hg species in refinery biosludge and pipe scale samples. However, the balance of Hg species present in these samples depended on the nature of the crude oil being processed, i.e. sweet (low sulfur crudes) vs sour (higher sulfur crudes). This information on Hg speciation in the petroleum value chain will inform development of better engineering controls and management practices for Hg.

A silver electrode based surface acoustic wave (SAW) mercury vapor sensor: a physio-chemical and analytical investigation

In this study, a surface acoustic wave based Hg⁰ vapour sensor was developed where Ag IDT electrodes were employed as lone sensing elements.

Switchable solvent based liquid phase microextraction of mercury from environmental samples: a green aspect

A novel and environmental friendly approach using switchable solvent based liquid phase microextraction (SPS-LPME), followed by UV-vis-spectrophotometric determination has been developed for the preconcentration and determination of mercury.

Validation, using a chemometric approach, of gas chromatography-inductively coupled plasma-atomic emission spectrometry (GC-ICP-AES) for organotin determination

The coupling between gas chromatography (GC) and inductively coupled plasma-atomic emission spectrometry (ICP-AES) has been optimised using experimental designs. Four factors were considered in order to assist the crucial part of the coupling which is the analytes passing through the transfer line. The methodological approach based on the planning of fractional designs is described and justified according to an optimal experimentation. Then, the GC-ICP-AES-based method has been validated by means of statistical tests performed on calibration curves and evaluation of accuracy, precision and limits of detection (LOD), according to ISO standards and IUPAC recommendations. The absolute LOD are found to be quite similar to those obtained using flame photometer. Relative LOD ranged between 20 and 80 ng (Sn) L(-1) after liquid-liquid extraction of the analytes. When solid phase micro-extraction (SPME) is used, LOD are sub 10 ng (Sn) L(-1). The repeatability is 3-10%, according to the extraction used. Analyses of reference sediment, fresh and waste waters confirm the suitability and capabilities of GC-ICP-AES for organotin determination in the environment. The statistical approach has been demonstrated to be a powerful methodological tool, enhancing the experimental part by providing reliable analytical results.

Speciation analysis for mercury in gas condensates by capillary gas chromatography with inductively coupled plasma mass spectrometric detection

A method allowing species-selective determination of atomic mercury, non-polar dialkylated mercury compounds,polar monoalkylated species and inorganic mercury complexes in natural gas condensates was developed. Inductively coupled plasma mass spectrometry was employed as a detection method for capillary gas chromatography and compared with microwave induced plasma atomic emission detection for the analysis of hydrocarbon-rich matrices. The method was based on two consecutive injections allowing comprehensive speciation analysis. First a sample aliquot was diluted with toluene and analysed for Hg0 and individual dialkylmercury compounds. Then, another aliquot was butylated with a Grignard reagent for the species specific determination of Hg(II) and monoalkylated mercury species. The detection limits were down to 0.08 pg level.

Gas chromatographic methods for oil analysis

In the past 50 years. gas chromatography (GC) has played a most important role in the analysis of oil. In this review, the early history is briefly reviewed; next developments in this highly relevant application area since about 1985 are highlighted. The main topic of interest are the introduction and decisive role of capillary GC, the use of selective detection techniques, the versatility of coupled-column techniques and, specifically, the additional power of comprehensive two-dimensional GC.

Application of chromatographic and electrophoretic methodology to the speciation of organomercury compounds in food analysis

Trace metals such as mercury, especially its organic compounds, are an important risk to the environment and to man due to their accumulation in the food chain. For this reason, the routine determination of the very toxic methylmercury, and of other organic and inorganic mercury compounds in marine and land animals, vegetables, fruits and fresh water is of increasing importance in health and environmental control programmes throughout the world. The majority of speciation methods for organomercurials involve a series of fundamental steps for the identification and quantification of samples of biological origin: extraction or isolation from the matrix; derivatisation and concentration; detection; separation of different species of interest and of interference. Each of these steps, as part of the chromatographic analysis of MeHg and of other organomercurials is revised in this study using food samples.

Gas chromatography

This review of the fundamental developments in gas chromatography (GC) includes articles published from 1996 and 1997 and an occasional citation prior to 1996. The literature was reviewed principally using CA Selects for Gas Chromatography from Chemical Abstracts Service, and some significant articles from late 1997 may be missing from the review. In addition, the online SciSearch Database (Institute for Scientific Information) capability was used to abstract review articles or books. As with the prior recent reviews, emphasis has been given to the identification and discussion of selected developments, rather than a presentation of a comprehensive literature search, now available widely through computer-based resources. During the last two years, several themes emerged from a review of the literature. Multidimensional gas chromatography has undergone transformation encompassing a broad range of activity, including attempts to establish methods using chromatographic principles rather than a totally empirical approach. Another trend noted was a comparatively large effort in chromatographic theory through modeling efforts; these presumably became resurgent with inexpensive and powerful computing tools. Finally, an impressive level of activity was noted through the themes highlighted in this review, and this was particularly true with detectors and field instruments.