Contamination, risk assessment and source apportionment of the heavy metals in the soils of apple orchard in Qixia City, Shandong Province, China

Food safety is influenced by soil heavy metal pollution, since it is of great significance to study soil heavy metal pollution of agricultural products. In this work, 5 vertical and 20 horizontal sampling points were collected from apple orchards in Qixia City, Shandong Province to study soil pollution. Geo-accumulation index and potential ecological risk were used to assess the level of soil pollution. Positive matrix decomposition (PMF) receptor model was used to identify the source contribution of the heavy metal in soil. A geostatistical analysis method was used to study the spatial distribution patterns of heavy metals. Vertical concentration analysis of heavy metals showed that the concentration of heavy metals, excluding Cr, was higher in the soil surface than in the bottom soil. The potential ecological risk level of ordinary orchards was the highest. The horizontal concentration analysis showed that the average value of Hg was over twice the background value in Shandong Province. The potential ecological risk index values showed that the overall risk level of the soil was at moderate. No heavy metal was detected in the apple sample, but the residue of carbendazim requires attention. The spatial distribution of heavy metals indicated that the use of fertilizers and pesticides and industrial activities may be the main sources of heavy metals in orchards, which was similar to the results of PMF. The sustainable development of Qixia City orchards clearly requires focus on soil acidification, low soil organic matter, and older fruit growers.