The ICPR measuring programme chemistry and its monitoring approach – a look back and a glimpse of the future

ABSTRACT The Rhine measuring programme chemistry dates back to 1953, and its monitoring network as well as procedures have changed significantly over time. Next to pressures from industry and household wastewater loads, catastrophes such as the Sandoz chemical spill in 1986 fostered international cooperation along the Rhine. By integrating technical trends and innovations, the programme has managed to keep pace with societal and regulative demands. It remains a programme with one foot in its long history and one in the present, facing the challenges to come, with its strength based on a multilevel international cooperation based on trust.


Introduction
The river Rhine connects six nations -from Switzerland to the Netherlands -and is one of the largest rivers in Europe.Its catchment includes nine states with some of the most densely populated and industrially developed areas.The International Commission for the Protection of the Rhine (ICPR) was founded in 1950.Its main tasks today are to protect the Rhine from pollution, to increase biodiversity, to reconciliate the ecology of the Rhine with its other functions and to reduce the damage and risks caused by floods.Baseline information on the ICPR and its role in the international context is given elsewhere (e.g., Dieperink, 2000).The chemical measuring programme and its documentation in the form of number tables date back more than 60 years, reports date back to 1987 (https://www.iksr.org/en)and older information is available on demand.In this study, we show the milestones of our long-term monitoring programme (technical and chemical) and we highlight aspects that may teach us lessons for future action, connecting threads of the past (which were basically emission-based, e.g., metals and metalloids) and future challenges, which include micropollutants and potentially a renaissance of former pollution scenarios caused by low-water extreme events within the global warming crisis.Starting in the 1950s with only a few parameters, the recently established new database includes about 1600 parameters, ~3 million data points, 21 active and 15 nowadays inactive stations, and receives approximately 170,000 new data points from ICPR delegations per year.The monitoring network in its recent status is available at https://iksr.bafg.de.Not only was the monitoring network modified over time, the data handling and presentation as part of the Rhine measuring programme chemistry have also undergone significant changes.The measuring capabilities within the countries have evolved, fostered not least by digital advances in the last decades.Taking the experience from the last 60 years as an indicator, it seems possible to strike a path to the future and to shed light on technical advances with the potential to significantly impact nextgeneration monitoring skills (Arndt et al., 2022).

Major impacts caused significant changes
At this point, it should be noted that studies on the chemistry of the Rhine had already taken place in the period 1800-1945.A comprehensive overview of the different activities over time is given by Tittizer and Krebs (1996).As an example, Vohl (1871) qualitatively describes how investigations has already been accomplished in 1870: 'He complained that the streams and rivers served to take up all garbage when flowing through the cities and villages; here in particular the "unclean trades" contributed to the pollution.Other industrial plants, dye works, aniline and chemical factories in general, often fed the rivers with highly toxic substances, such as arsenic, copper, lead or zinc.As a result, the effluents of these plants continued to poison the river water, making it unusable for industrial purposes' (Tittizer & Krebs, 1996).
The Rhine measuring programme chemistry was initiated in 1953.'At the suggestion of its Dutch delegation, the Central Commission for the Navigation of the Rhine, meeting in Strasbourg from 10 to 13 April 1946, discussed the pollution problem of the Rhine stream and instructed the delegates of the states represented in this commission to call the attention of their governments to this important and urgent problem' (ICPR, 1956).In the report on physical and chemical examinations of the Rhine water from 1956, the following explanation and mandate can be found in the introduction: it was suggested that the governments of the Rhine riparian states should initiate negotiations 'in order to gradually improve the quality of the Rhine water on the basis of an agreement.However, it seems necessary first to study the Rhine and its tributaries and to determine the various sources of pollution.Then, the type and degree of pollution must be determined.On the basis of such a survey, it would then be possible to determine the demands to be made on the purity of the water, as well as the remedial measures to be taken '. This was in 1946(ICPR, 1956) and the overall tasks remain the same.On 11 July 1950 the kick-off meeting for the 'international commission for the protection of the river Rhine against contaminations' took place and the first targets were to define physical and chemical parameters among the delegates to describe the river Rhine status.In this context, first decisions on methodological approaches were taken and by 1953, the initial set of monitoring stations and analyses including the first monitoring programme were initialized.The first report with reference to the years 1953 and 1954 was published in 1956 and today a report is published every two years (in the future every three years, e.g., Figure 1).
After the rivers had started to be used as a receiving system for wastewater (we should remind ourselves that this has not always been the case) and with ongoing industrialization along the Rhine, further massive inputs of nutrients and pollutants were discharged into the river.As a consequence, nutrients, metals and metalloids were within the focus of monitoring activities in the Rhine measuring programme chemistry.
Thinking about extreme events with long-lasting impact on the international cooperation, the year 1986 was certainly outstanding, with the Sandoz and Chernobyl catastrophes.Both contributed in equal measure to a change in societies' perception of human activity and its influence on our environment in Europe.For water management, the Sandoz disaster on 1 November 1986 -in which the warehouse of a pharmaceutical company near Basel caught fire, releasing a chemical cocktail of water from the firefighting operations into the Rhine, leading to massive fish mortality -has led to an intensification of the ICPR's monitoring activities and an expansion of the measuring programme (ICPR, 1987).Looking back from 2020 to 1980 (Figure 2), a clear shift between the different parameter groups within the Rhine measuring programme chemistry is visible.Radioactive substances disappear completely from the Rhine measuring programme chemistry over time, whereas the supporting parameters and inorganic analytes remain relatively constant, and the number of organic analytes rise sharply in both matrices after 2000 (also fostered by the EU Water Framework Directive).
In the beginning, however, suspended particulate matter was not addressed at all; in the authors' perception, their relevance as a time and space integrating aquatic matrice for sorbing analytes is increasing in different monitoring programmes (Boulard et al., 2020;Diaz et al., 2020;ICPR, 2022;Kotthoff et al., 2019).
Nowadays, micropollutants have been identified as one of the main challenges.Therefore, a reduction target of at least 30% by 2040 was agreed by the Conference of Rhine Ministers in 2020 and the ICPR was given the mandate to develop a monitoring and evaluation system that was published in December 2022 (ICPR, 2022).

Changes over time
As an example, Table 1 shows significant network changes over time as they appear within the ICPR number tables (https://iksr.bafg.de).In the authors' opinion, sometimes it is unavoidable to change the location of a monitoring station, but it should always remain the very last choice if all other alternatives have been exhausted.
In the long-term database of the ICPR, limits of detection considerably limit the informative value of time series.In this context, the authors call for awareness of the fact that almost no other analytical factor causes such strong unwanted effects in our databases.Every analytical chemist of their time carries a very strong responsibility to deliver high-quality data sets to the next generation, including the best possible limits of quantification and detection.However, strongly varying performances between national and international partners significantly hinder the evaluation of analytes within transboundary catchments.Every value above a limit of detection is a potential treasure in the future.When improving and changing analytical procedures, sometimes breaks in time series are visible.Therefore, overlapping time windows to compare old and new methods before they find their way into the long-term data sets are of major importance.In this regard, sometimes methods and procedures delivered by different institutions (e.g., ISO-15587, 2002) are not sufficiently detailed to avoid systematic deviations between laboratories along a river.Therefore, it is very important to initiate good and trust-based communication and corporation along transboundary rivers.
The same holds true for the management of the monitoring stations and the data collection.Within the last years, the data communication and exchange processes were renewed and shifted from fixed table templates towards more flexible formats, and in this respect, in the authors' view, it is very important to take the needs of those who deliver data seriously, in order to avoid any data-handling artefacts.In this sense, the Rhine measuring programme chemistry seems to be better prepared than many other basins (Mukuyu et al., 2020), keeping in mind that one must keep track of the potential benefits from technical evolution.Finally, procedures should be installed and respected, to slowly and gradually change the analyte spectrum of measuring programmes over time.Erratic changes justified by short-term interests may cause very significant long-term damages by binding time and other resources within the monitoring networks.

A renaissance of former challenges?
Since the 1980s and 1990s, another phenomenon has emerged that will certainly be even more present in the near future, as the climate crisis intensifies.With a look at the dry years of 2003, 2018 and 2020 with record low-water levels in the Rhine, it becomes clear that with a further scarcity of water supply, there may be a renaissance of challenges that were thought to have been overcome (e.g., potentially rising concentrations of metals and metalloids).In this respect, the following questions will most likely demand our attention within our networks in this and the next decade: (i) are we able to guarantee the water supply of our stations over time?(ii) Are we well prepared to handle conflicting interests with respect to the water quality, e.g., between water suppliers and water consumers?(iii) Will there be a renaissance of former challenges with respect to the composition and potential enrichment of pollutants that we thought we had already overcome?(iv) Are we well enough prepared for new challenges with supra-regional dimensions and the potential to cause ecosystem-wide adverse effects, as seen from the Oder River fish mortality in 2022 (Wiederhold et al., 2023)?From the authors' perspective, the following points are of considerable importance to handle these future challenges: (i) a further improvement of the international cooperation along the Rhine, including the provision of the respective personal and technical resources; (ii) direct and non-bureaucratic communication and decision processes between national and international partners; and (iii) a clearer commitment of national and international decision-makers to protect and extend the collaborations, which is predicted to be needed if we want intelligent international water management alternatives in our future.

Innovation (at its time) and perspectives
Although Table 2 shows not all potential innovations at the respective time, the overview delivers a real-life example of what was perceived as innovative at the respective time in Koblenz.Now it is time to think briefly, from this basis, about methods with the potential to support our chemical monitoring in the future.In doing so, different areas must be united.Particularly due to strong economic pressure, on-or at-line methods in the stations must be sufficiently robust to enable improvement of their status compared to laboratory methods (Arndt et al., 2022).The detection limits to be achieved also play a major role.The added value that is almost inevitable when we are able to fully or partially automate our processes is a higher temporal resolution, at the same time making the data themselves and their evaluation available more quickly to the public and to decision-makers.To this end, the already established and previously successful methods of dissemination (target grouporiented reports and brochures, publications, data and information provision via our websites, small group information talks as well as social media channels) will probably have to be expanded even further in the direction of condensing information to make use of different online platforms.However, the numerous public inquiries via our websites and the consistently positive direct feedback from political levels are measures of success in this respect.Of overriding interest is the development of tools that automate and foster quality assurance.Based on high-quality, highly time-resolved data, we are also going to significantly improve our forecasting capabilities.This will better allocate the increasingly scarce water resource and better balance competing interest between, e.g., industrial extraction and ecological provision.As possible realistic equipment at measuring stations, automated to a great extent, for chemical parameters on the Rhine -besides the recording of basic parameters (temperature, oxygen, conductivity, pH) with sensors -the authors currently predict the recording of anions by means of online ion chromatography, if necessary supplemented by the use of optical sensors; the analysis of a large part of the periodic table by means of inductively coupled plasma mass spectrometry (Belkouteb et al., 2023) in a single run; and non-target analytics, already established offline along the Rhine (https:// www.iksr.org/en/iksr/rhein-2040/rhine-project-non-target-screening)and online at the BfG in Koblenz, as very promising tools (Arndt et al., 2022).In particular, the non-target analyses (on-or offline) have the potential to act as a game changer in the hare and hedgehog run between dischargers and those who monitor water quality, if we can overcome the bottlenecks (e.g., Dietrich et al., 2022;Koppe et al., 2020Koppe et al., , 2023)).

Conclusions
Wilk et al. ( 2019) summarized various aspects of management in the past, including the Rhine water quality regime, and dared to think of granting rights to the river.In the summary, the authors conclude that basically, '. . .rights are not absolute: they are always relative, and the rights of a river must be balanced with the rights of other entities, such as humans, other rivers, and possibly other non-human entities such as forests . ..'.But if we take the idea of granting rights to the Rhine as a basis, how well prepared is our monitoring and measuring programme to deliver the information needed in times of such significant ecosystem changes to protect the Rhine?In the previous sections, we have shown that our activities stand in a long history of international cooperation at the Rhine.We have also shown in flashlights the evolution of our activities and have highlighted which potentials may be given by innovation within our network.In this context, the most important task for the future is most likely to improve time gaps between analyses, quality control, condensation of data for several analytes, and evaluation, provision and forecasts.As mentioned before, rivers were not always receiving waters for our wastewater, and a major task beyond the monitoring responsibilities is to close our anthropogenic water cycles within the global climate crises.With this vision in mind, we deliver the data foundation to rethink environmental permits in pronounced periods of low water.As long as the Rhine and its tributaries remain receiving waters, it remains our task to deliver the best possible comprehensive, fast and reliable data to the public and the decision makers.Therefore, the superior task remains to be the 'keepers, extenders and protectors' of the long-term data sets.

Figure 1 .
Figure 1.Examples of historic ICPR technical reports.Today, the reporting and the data provision are done almost exclusively digitally; see also https://www.iksr.org/en/public-relations/documents/archive/technical-reports.

Figure 2 .
Figure 2. Changes within the four main groups of the Rhine measuring programme chemistry displayed in 10-year intervals from 1980 to 2020.Left: water analyses, right: suspended matter (SPM) analyses.Information exported from https://iksr.bafg.de.

Table 1 .
Examples of stable conditions and changes within the monitoring network of the ICPR along the Rhine.Stations in between two horizontal lines are in terms of content connected locations.

Table 2 .
Technical innovations introduced from the 1960s until 2020 at the international monitoring station Koblenz Rhine.