Assessment of Soil Environment Quality and Ecological Risk for Kiwifruit Orchards in Jiangshan City, Zhejiang Province

BACKGROUNDThe orchard soil environment is closely related to kiwifruit yield, quality and its edible safety. Research shows that the nutrient insufficiency and uneven distribution in kiwifruit orchard soil is a common problem in China, and in some areas, the content of heavy metals in soil has been found to exceed the environmental quality standard for soils. In recent years, the planting area of Kiwifruit in Zhejiang Province has been expanded year by year, being one of the important kiwifruit producing areas in China.

OBJECTIVESTo study the present situation of soil environmental quality in kiwifruit orchards in Jiangshan City, Zhejiang Province.

METHODSTwo typical kiwifruit orchards were selected to collect samples of soil, rock and fruit, and the content of heavy metals, nutrients and physical and chemical parameters of soil and rock samples were determined by atomic fluorescence spectrometry (AFS) and inductively coupled plasma-optical emission spectrometry (ICP-OES). The environmental quality and ecological risk assessment of orchard soil were carried out with the main research contents of nutrient abundance and deficiency in orchard soil, influence factors, heavy metal content and fruit edible safety.

RESULTSThe results showed that the content of Ag, Bi, Co, Cr, Ni, Sb, Se, V and SiO₂ in the soil of the two orchards were lower than those of Quzhou City and Zhejiang Province, while Pb and Al₂O₃ contents were higher than those of Quzhou City and Zhejiang Province. The characteristics of soil element content were obviously controlled by the natural geological background. Soil pH value ranged from 4.61 to 6.30. According to the classification standard in DZ/T 0295-2016, the soils in the studied area belonged to strong acidic and acidic soils. Nutrient elements K, Ge, Mo and Zn were abundant, but N, P, Mn and S were deficient. The maximum value of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the soil samples were 21.84, 0.22, 23.53, 20.47, 0.06, 8.82, 53.84 and 133mg/kg, respectively, which were far lower than the screening value of soil pollution risk for agricultural land (standard limit were 40, 0.3, 150, 150, 1.3, 60, 70, 200mg/kg when pH ≤ 5.5). The risk of soil pollution was low. The contents of heavy metals in kiwifruit fruit were lower than the limits of green food and food hygiene standards. For example, the highest content of As was 0.009mg/kg, the limit were 0.2mg/kg and 0.5mg/kg, respectively.

CONCLUSIONSOn the whole, the soils in the study area have the characteristics of strong acidity, uneven distribution of nutrients and low content of heavy metals. It is necessary to take scientific measures to supple and balance soil nutrients and prevent the risk of heavy metals activation caused by soil acidification.