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Based on the typical greenhouse vegetable production system in Siping City, Jilin Province, 124 soil samples were collected from greenhouse soils growing vegetables (GSGV), fields growing maize (FGM), and forest soil (FS) under different land utilization patterns. In addition, other samples including greenhouse vegetables (81), fertilizers (50), and irrigation water (10) were also collected in the studied region. To illustrate the accumulation characteristics of heavy metals in GSGV and greenhouse vegetables, the heavy metal content of different samples was measured using inductively coupled plasma mass spectrometry (ICP-MS) technology. The results indicated that the heavy metal content in GSGV was much higher than that in FGM and FS except for lead (Pb). Heavy metals including cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), and zinc (Zn) in GSGV presented with various degrees of accumulation. The mean value of Cd content in the soils in the investigation region was 0.45 mg·kg -1 , with about 42.8% of all the soil samples exceeding the Cd content criterion of the Environmental Quality Evaluation Standard for Farmland in Greenhouse Vegetable Production (HJ 333-2006). The content of the other heavy metals was in the normal range, and all met the regulations of the standard. In comparison with different vegetable categories, leafy vegetables showed much higher heavy metal concentrations (Cd 0.033 mg·kg -1 fresh weight) than did fruity ones. In total, about 2.5% and 1.2% of vegetable samples exceeded the regulated values of Cd and Pb recommended by the Standard of Food limits, respectively. With the cultivation time prolonged, heavy metal concentration in soils and vegetables all increased synchronously as the pH value decreased. The content of heavy metals in greenhouse vegetables was significantly influenced by soil pH and organic matter. It can be concluded that the health risk of greenhouse vegetables increased with GSGV accumulating more heavy metals due to the substantial application of chemical fertilizer and manure containing high level of heavy metals.

A sampling survey was conducted in the typical areas in Shouguang County of Shandong Province to study the characteristics of arsenic (As) concentration and speciation in greenhouse vegetable soil. The total As concentration in the surface (0-20 cm) and subsurface (20-40 cm) soil was averagely 8.27 and 7.93 mg x kg(-1), being 19% and 23% higher than that of the control (open field soil), and the soluble As (AE-As) concentration was 0.13 and 0.06 mg x kg(-1), 63% and 200% higher than that of the control, respectively. The ratio of residual As (O-As) to total arsenic reached more than 63.0%, and the concentrations of different As speciation decreased in the order of O-As > iron-bound As (Fe-As) > calcium bound As (Ca-As) > aluminum bound As (AlAs) > AE-As. With the increasing planting years, the AE-As concentration enhanced significantly, and the Al-As concentration also increased to some degree. After 15 years planting, the AE-As concentration in surface and subsurface soil increased by 75.0% and 150.0%, and Al-As concentration increased by 51.6% and 190.4%, respectively, while the concentrations of Fe-As and Ca-As all decreased to some degree.

Taking the facility vegetable fields having been planted for 1-12 years and the adjacent wheat land in Shouguang City of Shandong Province as test objects, this paper studied the distribution characteristics of arsenic (As), cadmium (Cd), copper (Cu), zinc (Zn), chromium (Cr), and nickel (Ni) in their soil profiles (0-150 cm). With the increase of soil depth, the test heavy metals contents in the soil profiles all had a decreasing trend, and in the same soil layers, the contents were obviously higher in facility vegetable fields than in wheat land. Comparing with those in the same soil layers of wheat land, the average contents of As, Cd, Cu, Zn, Cr, and Ni in 0-20 and 120-150 cm soil layers of facility vegetable fields were 35.0%, 146.2%, 65.6%, 36.4%, and 21.5%, and 10.6%, 178.5%, 19.4%, 20.2%, 15.2%, and 9.3% higher, respectively, and the average contents of the heavy metals in 20-120 cm soil layer of facility vegetable fields were also higher in some degree. In the 0-20 cm soil layer of facility vegetable fields, the Cd, Cu, and Zn contents had significant positive correlations with planting years (P < 0.05), with the accumulation rates of Cd, Cu, and Zn being 0.027, 1.153, and 2.830 mg x kg(-1) x a(-1), respectively. In facility vegetable fields, the test six heavy metals contents were significantly positively correlated with the contents of soil organic carbon and total nitrogen, and the Cd, Cu, Zn, and Cr contents were significantly correlated with the content of soil total phosphorus (P < 0.01). Applying organic fertilizer could induce the heavy metals accumulation in the soils of facility vegetable fields to some extent.

The study on the soil arsenic (As) accumulation under different types of agricultural use in Shouguang of Shandong Province showed that farmland soils had an average As content of 9. 63 mg x kg(-1) , with the highest being 15. 15 mg x kg(-1) . Compared with the local background value (9. 3 mg As x kg(-1)) , 53. 1% of soil samples was detected as As enrichment. The soil As content was high in the west, east and north parts of Shouguang, relatively lower in the middle part, and the lowest in the south part. Different agricultural use had an obvious effect on the soil As content, which was decreased in the order of wheat/maize land > cotton field > protected vegetable land > uncovered vegetable land. Such a difference in soil As content was mainly affected by agricultural activities. With the increasing year of vegetable planting, soil As content had an increasing trend, because the As input from pig dung and chicken feces was the main source of soil As in protected vegetable land. Soil As enrichment could be reduced to some degree by applying soybean cake fertiliz-