FAQ

Please use the links below to learn more about APIS data, terminology and ecosystem responses

Critical loads

Which acidity critical load values (CLmax S, CLminN, etc) should be used in risk assessment and how can it be reported?
What is the meaning of 'keq' in keq/ha/year?
What do the CLMaxN and CLMinN mean in acidity critical loads?
Why does APIS say to seek site specific advice?
Where can I find data about critical loads, levels and background concentration and deposition for UK national (SSSIs) and international protected sites?
There are two sets of values CLmaxS, CLminN and CLmaxN for each SAC or SSSI i.e. minCLmaxN and maxCLmaxN. Which should be used here? Should both sets of values be assessed and, if so, how should the results be reported?
Why is there no critical load assigned for some features?
Why are there multiple critical load graphs for the same interest features at a particular site especially for dune habitats?
Why are there data missing about Areas/Sites of Special Scientific Interest in some of the critical level/load datasets for download?

Critical levels

CBED

What monitoring data is used in the pollutant data on APIS?

Emissions

Background data

Acidity

There are two sets of values CLmaxS, CLminN and CLmaxN for each SAC or SSSI i.e. minCLmaxN and maxCLmaxN. Which should be used here? Should both sets of values be assessed and, if so, how should the results be reported?

Biomonitoring

How can I tell if a lichen indicates good or bad air quality?

Bugs, errors & contacting us

Deposition Velocity

Ecological Impacts

Get involved

How can I get more involved in UK air pollution work?

Habitats protected sites

Lichen app

Lichens & bryophytes

Mapping

How can I visualise APIS data for long features such as a river?

Modelling

Unit conversion

What is the meaning of 'keq' in keq/ha/year?

Update log

How can I set alerts to ensure that I am kept up to date with any revisions to the background/critical load information?

Search by location

Site specific advice

Trends

Does APIS have data about change in nitrogen deposition over time?