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NILU measures volatile organic compounds (VOCs) in Chile

Quintero-Puchuncavi Bay
Foto: Susana Lopez-Aparicio

Over a period of 4 months, NILU has measured the concentrations of volatile organic compounds (VOCs) in the air in the Chilean municipalities of Quintero-Puchuncaví and Concón in the Valparaíso region. The measurements were carried out on behalf of the Chilean Ministry of the Environment. So far, the measurement results show no sign that VOC emissions from the industrial area affect the air quality in neighbouring residential areas.

Senior Scientist Norbert Schmidbauer, NILU Photo: Ingar Næss

“NILU was contacted in the autumn of 2018, after there had been several episodes of malodorous emissions from industrial activities in these areas”, says senior scientist Norbert Schmidbauer from NILU’s Department of Monitoring and Instrumentation Technology. “The Chilean Ministry of the Environment wanted help from an independent expert, who could carry out measurement campaigns in relevant areas.”

NILU’s assignment was to map concentrations of volatile organic compounds in the air, and in addition, if possible, trace the compounds back to the source – which is most likely the industrial activity in the immediate area.

Background for the assignment

In both Quintero-Puchuncaví and Concón, various forms of industrial activity take place close to residential areas and schools. Among the businesses is an oil refinery in Concón, and two coal-fired power plants, a copper smelter and several plants receiving, storing and distributing petrochemical products.

Back in August-September 2018, one or more episodes occurred where large amounts of pollutants may have been released into the air. Several hundred people visited the hospitals because of various symptoms they thought were related to air emissions, and there was also a lot of media attention associated with this.

To investigate the case, the local authorities used a newly purchased measuring instrument. The measurements carried out with this instrument showed very high concentrations of methyl chloroform, nitrobenzene, butane and toluene for several consecutive weeks throughout the current area.

Incorrect measurement results from earlier

“The concentrations of methyl chloroform that have been mentioned in the media are so high that they simply have to be wrong”, says Schmidbauer. “We are talking about a factor of several million times higher than likely, so we assume that the instrument used was not properly calibrated.”

Schmidbauer further explains that methyl chloroform is a substance that has been phased out under accordance to the Montreal protocol. This means that it is neither permitted to be used nor produced, and it is monitored through monitoring stations and observatories worldwide. Before methyl chloroform was banned, the concentration in air globally was somewhat above 100 ppt (parts per trillion), as of today it is about 2 ppt.

The previous measurements performed in Quintero-Puchuncaví showed results at around 200 ppm (parts per million), i.e. the substance must have been used on a large scale. The NILU scientists regard it as very unlikely, and their later measurements also show an average concentration of methyl chloroform in the air of approx. 1.7 ppt.

Both media and citizens would like to know which substances polluted the air last autumn and what the air quality is actually like in the area. Since NILU was not there at the time and took samples in August and September, unfortunately we cannot say anything about what happened back then”, says Schmidbauer, “but we understand that people are concerned and want answers.”

Local schools take part in sampling the air

Senior scientist Susana Lopez-Aparicio, NILU Photo: Ingar Næss

NILU started sampling in November 2018, and has later taken samples in December 2018 as well as in January and February 2019. The main part of the sampling has been carried out by NILU in collaboration with a group from the Ministry. In addition, local residents and local schools have been involved, and they have taken samples when they have noticed strong odours in the neighbourhood.

“Our strategy has been to try to record the highest concentrations of VOCs in the air”, explains senior scientist Susana Lopez-Aparicio from NILU’s Department for Urban Environment and Industry. “Thus, we have not taken samples continuously, but rather focused on taking samples when people notice strong odours, when there has been visible activity at the factories in question, and when there is little wind.”

NILU’s measurement results

During the campaign, NILU has used two different measuring methods. One of them is a very precise method, but when you use it you have to decide in advance what substance you are looking for. The NILU scientists used this method to look for around 40 different compounds, including methyl chloroform, ethane and propane. The second method is more universal and  samples for longer periods. It is particularly relevant to use when it comes to identifying unknown organic compounds.

Regarding nitrobenzene, butane and toluene, the NILU scientists also found very low concentrations in the air. The measurements of nitrobenzene never exceeded a detection limit of 0.1 ppb (parts per billion), while butane and toluene also appeared only in very low ppb levels.

“We can’t say for certain that the concentrations of these substances in the air never were higher at an earlier stage”, says Lopez-Aparicio. “But for methyl chloroform especially, levels above normal would have been recorded at atmospheric observatories, because this is a prohibited substance that is very closely monitored.”

In Quintero-Puchuncaví, NILU’s measurements also showed low to moderate levels of hydrocarbons from oil and gas related products in the surrounding residential areas.

Within permitted limits

“With the exception of benzene, there is no limit value for volatile organic compounds in outdoor air”, explains Lopez-Aparicio. “For benzene we found levels of between 0.3 and 1 microgram per cubic meter of air (µg/m3), while the limit value is 5 µg/m3 as an annual average. For all substances, we found levels that are lower than what is allowed for industrial use.”

In Concón, there is an oil and gas plant and a refinery. In this area, the NILU scientists measured higher concentrations of volatile organic compounds, especially at night. During the measurement period, citizens living in residential areas just a few hundred meters from the two industries reported several episodes of very strong odour. But the measurements still did not show values above the limit value for benzene in outdoor air.

What happens next?

The first draft of the final report for the measurements carried out was sent to the environmental authorities in Chile before Easter, and NILU hopes to have the final report ready in early May. Parts of the report have already been completed and have been presented to the authorities, media and participating schools and residents of Quintero-Puchuncaví and Concón.

“We have not been asked to carry out additional assignments in Chile”, says Schmidbauer, “but we have discussed with the authorities the possibility to assist in establishing a laboratory that can analyse volatile organic compounds.”

“It could also be useful to repeat the VOCs measurements during winter, when the dispersion conditions are poorer”, Lopez-Aparicio adds.

The two are open to taking on other assignments in Chile, but emphasize that in the long run it will be more advantageous to build up corresponding measuring competence at local research institutions. In that case, it will be important to simultaneously establish independent facilities for analysis of samples, as well as health-care bodies that can evaluate the results in relation to relevant measures.

“Research is dependent on trust”, Schmidbauer concludes, “and that trust is built over time and through independent, transparent activities.”