Air pollution effects on crops in Malta : a case study on Solanum tuberosum

Abstract

To date the issue of air pollution in Malta has not been addressed. The main aim of this research study was to evaluate the quality of the air in selected Maltese agricultural areas. Four sites were chosen in order to determine whether there exists any possible trend or relation ship between the ambient air quality and the growth and yield of the potato (Solanum tuberosum). The multiple interacting stress approach was adopted, whereby factors such as soil moisture deficit, soil fertility, meteorology and the co-occurrence of air pollutants were taken into account. The results obtained from the air monitoring programme, which was conducted over two potato growing seasons, revealed that there is a spatial and temporal variation in the levels and types of air pollution. Ozone exposure to the north of Malta commonly approached or exceeded the W.H.O. guideline and the E.U. threshold limits for crops. Most of the readings recorded for the nitrogen oxides exceeded the W.H.O. guideline values at all the sites. Sulphur dioxide concentrations were significantly higher to the southern and central regions of the island. A negative correlation was obtained for root-to-shoot ratios and crop yields versus the ambient ozone concentrations. Synergism was also observed between ozone and sulphur dioxide. In contrast, a positive correlation was obtained for the root-to-shoot ratios and potato crop yields in relation to the nitrogen oxides. The results of the soil survey revealed that the levels of nitrate nitrogen in the soil were sub-optimal following the heavy rains in December and the potato plants may have used the nitrogen oxides as an alternative nitrogen source.