Soil contamination and ecological risk of heavy metals in alkaline vineyard soil

The soil utilized for grape growing not only has faced the pollution problems but also could be suffered ecological risk by heavy metals from chemical fertilizers and Cu-fungicides. Hétszőlő vineyard (1.4 ha) with an alkaline reaction in soil (the average soil pH of the 0-10 cm soil layer was 8.02), which is located along and on the southern slope of Tokaj-hill, Tokaj-Hegyalja, Hungary was chosen as study area of this study. The total concentration of heavy metals, enrichment factors (EFs), pollution load index (PLI) and contamination factor (CF) were used to assess the current status and pollution degree of heavy metals in vineyard soil. Besides, the potential ecological risk would be evaluated via the ecological risk factor (Ei) of an individual metal (Zn, Pb, Co, Ni, Cr, Cu) and the potential ecological risk index (PER) of all studied metals.

Analysis results showed that all of the heavy metals had lower total contents on average compared with the Hungarian background and pollution limits (Joint Decree (6/2009. (IV. 14) KvVM-EüM-FVM and 10/2000. (VI. 2) KöM-EüM-FVM-KHVM), except for Cu (36.19 mg/kg), Ni (36.50 mg/kg) and Cr (60.26 mg/kg). Thus, the topsoil of Hétszőlő vineyard in Tokaj was contaminated by Ni, Cr, and Cu at a moderate level. EF analysis (Sc as reference element) reflected that Cu (EF = 2.70) was enriched moderately, in contrast Zn (EF = 1.22), Pb (EF = 1.05), Co (EF = 1.00) were not enriched in the vineyard topsoils. Although EF of Ni and Cr obtained at Tokaj were 1.66 and 2.30 respectively, EF_min of these studied metals were around 1 and they EF_max were higher than 2 demonstrated that these elements were enriched at some positions. The general assessment of EFs of all soil samples illustrated the anthropogenic origin of Cu, Cr, and Ni while Zn, Pb, and Co were enriched mainly from the geogenic process; and the enrichment process of heavy metals occurred more strongly at the bottom of the slope. CF, which was determined, could be divided into two groups in value, in which CF ≤ 1 presented a low contamination for Pb (CF = 0.71); Co (CF = 1.00), and 1 < CF < 3 was a moderate contamination for remaining metals Zn, Ni, Cr and Cu with CF figures were 1.06, 1.68, 2.28 and 2.08, respectively. Besides, the topsoil of Hétszőlő vineyard was considered in the moderate pollution status with FLI was 1.35. The results of Ei indicated that all heavy metal in the topsoil of vineyard showed a low ecological risk, with the descending order of contaminants was Cu (10.38) > Ni (10.07) > Co (4.98) > Cr (4.55) > Pb (3.54) > Zn (1.06). In addition, the mean PER was 34.59 and it revealed a low ecological risk for all metals in the vineyard soil. Even though there was a low potential ecological risk, the moderate level pollution of heavy metals, enrichment process, and the continuous using chemical compounds in viticulture could cause serious risk pollution by heavy metals in the future.