The need for improved monitoring of the marine environment and for accessible databases with climate quality relevant data for modelling of global change processes, including ocean acidification, is highlighted in various documents.
At a global level, the United Nations Agenda 2030 set a list of Sustainable Development Goals (SDG), including a dedicated goal on the ocean (Goal 14). Within SDG 14 several targets highlight more specific aspects of oceans and life below ocean. Target 14.3 specifically addresses the need to “minimise and address the impacts of ocean acidification, including through enhanced scientific cooperation at all levels”. Indicator 14.3.1 demands “Average marine acidity measured at an agreed suite of representative sampling stations”. The methodology established for this indicator identifies the quality control of submitted data as a major concern. Therefore, it is stated that “Data providers / Member States are encouraged to submit primary quality controlled data sets” and “All data submitted to SDG 14.3.1 must include an estimate of measurement uncertainty in the metadata”. The categories of measurement quality established in the Indicator 14.3.1 methodology rely upon the targets fixed by the Ocean Acidification – Observing Network (GOA-ON): to address “climate goal” challenges, an measurement uncertainty level of 0.003 (k = 1) is needed. This uncertainty requirement, covering both individual measurements and trend observations, is close to the level of primary standards.
At a European level, the EU is fighting climate change through ambitious policies within Europe and in close cooperation with international partners.
- Ocean acidification is one of the priorities of the EU climate action as mentioned in different key EU legislation and policies. The Marine Strategy Framework Directive (MSFD, 2008/56/EC) is the environmental pillar of the integrated maritime policy. The MSFD is directly addressing the necessity to achieve a healthy marine environment (good environmental status (GES)) and to have reliable measuring systems to monitor the ocean’s status. Seawater acidification is addressed under descriptor 7 (hydrographic conditions).
- Additionally, the European Environmental Agency, whose mission is to provide reliable and independent information on the environment in support of European environmental legislation, set out indicators that have policy defined purposes and can be used to illustrate and communicate on complex phenomena. Ocean acidification is one of the climate descriptive indicators established to track changes in the ocean associated with climate change.
- In 2013 the European Commission adopted an EU Strategy on Adaptation to Climate Change in which European Standardization Organizations were invited to contribute to the European efforts aiming to make Europe more climate-resilient. The strategy highlights the key role of standards in securing climate resilience.
- Moreover, European Research Infrastructures (RIs) seek more and more to provide services and data products whose equivalence across different observing programmes should be demonstrated and mutually agreed by some sort of accreditation system. Methods to guarantee consistency and reliability of measured data is a mandatory requirement for this aim. This includes to establish traceability of all measurement results with known uncertainties to higher order standards based on harmonised measurement procedures..
An overarching harmonisation infrastructure is proposed by European (CEN) and international (ISO) standardisation bodies. ISO 18191:2015 “Determination of pHt in seawater – Method using the indicator dye m-cresol purple” describe the measurement of pHT, which is one of the quantities used to determine ocean acidification. However, this standard lacks technical specifications to comply with fundamental metrological concepts, i.e. metrological traceability, fit-for-purpose uncertainty evaluation and method validation. Thus, looking at the widely documented need for high quality measurements of the pHT of seawater, and the corresponding need for harmonised procedures, it becomes obvious that there is a most fundamental need to provide the metrological foundation to make ISO 18191 fit for purpose.
The overall aim of this project is to develop traceable measurement methods for pHT in seawater to produce a draft of a revised standard for the standardisation work of CEN/TC 230/WG 1, ISO 18191:2015 standard “Determination of pHT in seawater – Method using the indicator dye m-cresol purple” and ISO/TC 147/SC 2 “Physical, chemical and biochemical methods”.
The specific objectives of this project are:
- To develop methods for SI-traceable pHT measurements in seawater, including the pHT interval between 7.4 and 8.2, the temperature interval from 0 °C to 30 °C and a practical salinity interval between 5 and 40. In addition, to develop traceable standard reference solutions characterised with the Harned cell primary system with a target expanded uncertainty of 0.003 (k = 2) on the scale of pHT. (WP1)
- To develop a comprehensive uncertainty model for spectrophotometric pHT measurements of seawater, with a target uncertainty of 0.003 (k = 1) on the scale of pHT. In addition, to develop an associated software tool for uncertainty evaluation, based on the developed uncertainty model, suitable for application by end-users (e.g. oceanographers). (WP2)
- To develop an improved ISO 18191:2015 spectrophotometric method including the pHT interval between 7.4 and 8.2, the temperature interval from 0 °C to 30 °C and a practical salinity interval between 5 and 40 for measuring pHT in seawater by field laboratories using the indicator dye m-cresol purple and to validate these methods with an interlaboratory comparison. The comparison will include the methods and models from Objectives 1 and 2 and have a target uncertainty of 0.003 (k = 1) on the scale of pHT. (WP3)
- To contribute to the standards development work by extending the scope to low salinity range (down to practical salinity of 5) and including metrological concepts for ISO/TC 147/SC 2 “Physical, chemical and biochemical methods”, CEN/TC 230 “Water Analysis”, UNESCO SDG 14.3 and the EU MSFD (2008/56/EC) to ensure that the outputs of the project are aligned with their needs, communicated quickly to those developing the standards and to those who will use them (e.g. international oceanographic community), and in a form that can be incorporated into the standards at the earliest opportunity. (WP4)