Research removes nitrogen barrier for PAS detector

According to them, the current threshold value creates 'false certainty', because, for example, it has not been measured, but they do not know what a good threshold value is. The scientific supervisory committee of the research will know what to do with this. Arthur Petersen, professor at the University of London, member of 'the new think tank' and recently also a member of a review committee that made a critical judgment about Aerius, then believes that a new threshold value of 1 mole per hectare per year is very well defensible from a broader perspective than just a 'model scientific point of view'.

Especially because, according to him, the old standards very likely used incorrect assumptions about the precautionary principle and significance. That 1 mole is still low, especially compared to, for example, the 21 mole used in Germany. This standard applies to our eastern neighbors, who are also within the margin of error of whether or not they have an impact on nature, Petersen realizes. As a scientist, however, he still thinks 1 mole is a good guideline.

Four year old basis for new results
It is striking that it took five years before a real scientific study could be conducted into the arithmetic threshold value. Even more striking is that it refers to a study that is at least four years old, namely: report of the Hordijk Commission. This report also warned against false security.  

Why nothing was done with this report in the intervening years is not a question for scientists. That is something for politics. Precisely for that reason it has probably now been picked up again. The previous two Rutte cabinets did start a number of 'polder studies', with input from civil servants, NGOs and some policy researchers, into alternatives to the Water Framework Directive, with the unsurprising outcome that these are not available.

And now on
The IPO wants to speed up now that the new research is available. What's more, together with the ministries of LVVN and I&W a legal analysis and made an impact analysis on how to proceed further. These pieces are used to take new steps. According to Arthur Petersen, politically and administratively speaking, not much needs to be done. What is needed is for a new team of scientists, from multiple disciplines, to substantiate that an arithmetic lower limit of 1 mole is more defensible than the current lower limit. He almost has the blueprint ready, so to speak.

The Council of State can then start working on it tomorrow, so to speak, he believes. Because, if science agrees, politics, government and the courts no longer have to interfere. It is not really realistic that a new lower limit will be finalized tomorrow. In practice, this takes a few months, but that is also fast enough to help the many thousands of PAS detectors in the Netherlands out of the fire in time (no later than 2025) and to give construction the much-needed space again.

The PAS detectors all have a nitrogen deficiency/too high deposition of less than 1 mole per hectare. During the IPO press conference, some journalists wondered what would happen to all MOB procedures against the PAS reporters. According to Petersen, these are no longer useful because they are redundant.

Lower limit separate from other Aerius questions
The investigation into the arithmetic lower limit for nitrogen deposition is separate from any other questions regarding the operation of the Aerius model, such as whether it is suitable for licensing at local level and whether Aerius is on the right track with regard to dry deposition. It also says nothing about the credibility of the figures used to calculate the nitrogen sensitivity of habitats. Those are all separate matters. A higher threshold value of 1 instead of 0,005 mol makes the perceived impact of the aforementioned matters slightly milder.