Rothamsted Research

where knowledge grows

Atmospheric Pollution

Sources of anthropogenic air pollutants include livestock (ammonia, NH3), fossil fuel power stations (sulphur dioxide, SO2; nitrogen oxides, NOx) and vehicle emissions (nitrogen oxides, NOx). These ‘primary pollutants’ react with the atmosphere to produce secondary  pollutants as particulates and aerosols (sulphate, SO4; nitrate, NO3; ammonium, NH4) and as acids (sulphuric acid, H2SO4; nitric acid, HNO3; and hydrochloric acid, HCl). Atmospheric pollution is a major driver of environmental change and can damage human health. Therefore, since the mid-1950s, UK and European legislation and treaties have been implemented to reduce air pollutants. ECN data show that these have been effective.

Nitrogen dioxide

North Wyke is situated in a rural area, approximately 3km from the nearest village and therefore NO2 emissions are relatively low compared with more urban ECN sites such as Rothamsted (Harpenden). Over the first two decades NO2 concentrations fell significantly at North Wyke and can be mainly attributed to the switch from coal to natural gas generated electricity and the improvements in fuel quality and catalytic converters on road vehicles. Peak annual mean NO2 concentrations occurred in 1996 (3.7 ppb) with the lowest recorded in 2000 (1.6 ppb), a reduction of 57%. The current rate of change in NO2 concentration reductions (Figure 1) at North Wyke appears to be slower than earlier on in the monitoring period.

Figure 1. Average annual atmospheric NO2 concentrations at North Wyke (1994-2012). (Note: data for 2001 incomplete due to foot and mouth epidemic.)

According to the RoTAP (2012) report, emissions have not decreased recently as much as predicted, especially those from transport, possibly because of an increase in the use of diesel vehicles. A clear seasonal pattern was seen with the highest NO2 concentrations recorded in winter corresponding to increased demand for domestic heating.

Precipitation Chemistry

Acid deposition across the UK and Western Europe has been sustainably reduced in response to national and international control measures on sulphur (S) and nitrogen (N) emissions. As with the majority of ECN sites, concentrations of SO4 and NO3 in precipitation have significantly declined at North Wyke (Figure 2). Chloride concentration also decreased significantly (Figure 2), probably because of reduced sea-salt deposition reflecting reduced wind speeds, and also the decline in hydrogen chloride emissions in the UK of 94% between 1990 and 2006, largely as a result of decreased coal use. Reductions in precipitation acidity occurred at all ECN sites except North Wyke (Monteith et al., 2016). No clear trend was observed at North Wyke, however precipitation became less acidic during the late 1990s and early 2000s. In contrast to NH3 concentrations, ammonium (NH4) concentrations in precipitation declined, but not significantly.

Figure 2. Average annual ammonium (NH4), chloride (Cl), nitrate (NO3) and sulphate (SO4) volume weighted concentrations in rainfall at North Wyke (1994-2012). (Note: data for 2001 incomplete due to foot and mouth epidemic.)

Several ions exhibited seasonal variability. Average concentrations of Cl, magnesium (Mg) and sodium (Na) ions associated with seawater salts were highest in winter and lowest in summer, suggesting a relationship between marine sources and seasonal rainfall patterns. Highest concentrations of NO3 and NH4 in precipitation were found in spring, possibly linked to fertiliser and manure applications.

National Capability

A national capability is a BBSRC-funded resource intended to benefit the scientific community in general. These can be facilities as well as opensource datasets. 

National Capabilities

Rothamsted Insect Survey

Operates two national networks for monitoring insect populations in the UK

North Wyke Farm Platform

Provides the research community access to a range of in situ state-of-the-art instrumentation in hydrologically isolated fields and farms to better address key issues in sustainable agriculture.


A database of interactions between pathogens and their hosts maintained at Rothamsted Research with international input.

Long-Term Experiments

These have been running since the mid 19th Century, provide a unique experimental system and archive of soil and plant samples.