Biochar production increases the polycyclic aromat

Authors: Marcin Kuśmierz Patryk Oleszczuk

Publish Date: 2013/11/26

Volume: 21, Issue: 5, Pages: 3646-3652

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Abstract

The objectives of the study were the identification of the source of contamination of soils and estimation of the potential cancer risk that may be caused by contact with soils situated in the vicinity of biochar production sites Samples of soils collected in the immediate vicinity of traditional biocharproducing plants located within the area of the Bieszczady National Park Poland were analysed for the content of polycyclic aromatic hydrocarbons PAHs The sum of the content of 16 PAHs varied within the range of 180–1013 μg/g exceeding the norms permitted in many European countries The calculated coefficients on the basis of which one can determine the origin of PAHs molecular diagnostic ratios demonstrated that the potential source of PAHs in the soils may be processes related with the production of biochar Estimation on the basis of the results of incremental lifetime cancer risks ILCRs within the range of 233 · 10−4–105 · 10−1 indicated that the soils studied may constitute a significant cancer risk for persons who have contact with them The values of ILCRS should be considered as at least high which permits the conclusion that sites of that type may create a hazard to human healthThe method of sequestration capture and longterm storage of atmospheric CO2 proposed by Lehmann 2007 consisting in the transformation of biomass into biochar and its deposition in soils gained notable interest in the world of science Research in this area is conducted in many places in the world eg in Zambia Tanzania Malaysia and Nepal Biochars used in such studies are usually produced locally with traditional methods Also the unloading of kilns reloading transport and dosage of biochars to soils are most frequently done by hand Unfortunately due to their properties biochars may be dangerous to ecosystems and to human health Polycylic aromatic hydrocarbons PAHs contained in biochars create a risk to living organisms and to humans when they come in contact with those materials as well as with the soils amended with them Oleszczuk et al 2013 Sims and Overcash 1983 Workers employed in the production and transport of biochars are particularly exposed The area of that risk increases following the growing popularity of biochar useThe methods of biochar production are simple known for a very long time and can be applied in countries that do not have advanced technologies The results of numerous studies indicate a positive effect of biochars on the physical chemical and biological properties of soils Biochars are becoming a material that is more and more often used for the improvement of soil properties with simultaneous beneficial effect consisting in mitigating climate change With relation to the growing popularity of the utilisation of biochar an increasing number of people will have contact with biochars and with soils remediated with their use which may cause a notable expansion of the risk group This results from the fact that in the course of biochar production highly dangerous PAHs are formed Freddo et al 2012 Oleszczuk et al 2013 They are formed through the degradation of lignins and cellulose on the pathway of unimolecular reactions such as dealkylation dehydrogenation cyclisation aromatisation and/or radical reactions Sixteen of them due to their potentially mutagenic and carcinogenic properties have been given the status of priority substances in the USA and in the European Union Sims and Overcash 1983Biochar produced with the traditional method is characterised by very low mechanical strength and high brittleness therefore during the emptying of kilns shifting reloading and transport it undergoes considerable fragmentation As a consequence in the vicinity of kilns fine coal gets into the soil and the silt fractions of biochar are carried with the wind over longer distances In the immediate vicinity of the kilns soil may also be contaminated with the liquid products of pyrolysis PAHs migrating into the soil together with biochar are very hardbiodegradable Koelmans et al 2006 which contributes to their increased stability in the soils and extends the time over which they may pose a threat to organisms and to the environmentWorkers employed in the production and transport of biochar are particularly exposed to contact with contaminated soil Soil particles cannot only settle on the skin but they can also be accidentally ingested and inhaled As mentioned earlier the numbers of people involved in the production of biochar and thus exposed to contact with contaminated soil will grow following the scale of application of those materials In this context the assessment of risk related with environmental pollution resulting from biochar production is importantThe objectives of the study were to determine the level of polycyclic aromatic hydrocarbons in soils in the vicinity of traditional biochar kilns to identify—by means of the molecular diagnostic ratios MDRs—the sources of the PAHs and to assess the risk of cancer related with the presence of those compounds in soils This will permit to determine how sites related with the production of biochar affect the quality of soils and—indirectly—human health

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