Heavy Metal Risk Assessment of Asparagus and Its Soil on Chongming Island: A Metalomics and Statistical Analysis Approach

With the rapid development of society, heavy metals were more widely used in industrial and agricultural production, leading to their increasing pollution of the environment. Chongming Island, located at the mouth of the Yangtze River, had a special geographical location and was vulnerable to the threat of heavy metal pollution. Chongming Island was the main base of Shanghai's vegetable basket project, and asparagus was one of the main vegetables grown there because of its rich nutrition and crisp taste. Therefore, it was necessary to establish an effective assessment method to monitor the heavy metal levels in Chongming Island soil and asparagus to ensure food safety and public health.

In this thesis, we used metalomics and statistical analysis methods to detect heavy metal ion levels in soil and asparagus to conduct a comprehensive risk assessment of asparagus and its growing areas on Chongming Island. We measured the levels of 12 heavy metal ions and other ions in the soils of asparagus growing sites and analyzed their correlation comprehensively, and the main findings were as follows.

(1) The contents of various ions (K+, Na+, Ca2+, Mg2+, Cl-, SO2-4, HCO-3, CO2-3) in the soil of the asparagus growing area were measured by plasma emission spectrometry and multiple titration methods. The average contents of cations (K+, Na+, Ca2+, Mg2+) were 0.109, 0.174, 0.441, 0.134g/kg with coefficients of variation of 67.4, 71.2, 61.4, 74.8%, respectively; the average contents of anions (HCO- 3, Cl-, SO2- 4) were 0.013g/kg, 0.176g/kg, 0.592g/kg, 0.592g/kg and 0.013g/kg. kg, and 0.592g/kg, with coefficients of variation of 19.3, 76.1, and 58.4%, respectively. The highest Ca2+ content was found in asparagus planting soils, accounting for 51% of the total water-soluble cations, and higher Cl- and SO2- 4 content in anions. According to the classification and grading criteria of soil salinization mainly of chloride - sulfate type, the overall state of non-salinization, but a slight local salinization state. Attention should be drawn to the soil.

(2) The contamination risk of heavy metal ions in asparagus cultivation soils on Chongming Island was evaluated by using inductively coupled plasma mass spectrometry (ICP-MS) to determine the content of 12 soil heavy metal ions in the asparagus cultivation area of Chongming Island and combining with statistical analysis methods such as geological cumulative index. The results were 11.73, 5219, 0.192, 52.69, 65.30, 29608, 4215, 474.2, 23.90, 21.11, 116, and 0.214 mg/kg, respectively. Compared with the background values of Shanghai soil, the contents of Mg, Zn, Cu, As, Hg, and Cd in the soil showed different degrees of increase, and the contents of Mn, Ni, and Pb decreased. According to the analysis of geological cumulative index, As and Hg of heavy metals belonged to the overall slightly polluted state, Cd, Cu, Zn, belonged to the non-polluted state but there was a local slightly polluted pollution state, Mn, Ni, Pb, Cr belonged to the non-polluted state. The risk of heavy metal ion contamination in asparagus from Chongming Island was assessed by inductively coupled plasma mass spectrometry (ICP-MS) with statistical analysis methods such as enrichment index. The results were 0.003, 157.1, 0.012, 0.137, 2.017, 19.23, 302.3, 1.414, 0.895, 0.020, 9.476, and 0.001 mg/kg, respectively, and the asparagus was found to be in a safe condition using single factor and combined contamination index analysis. The analysis by bioenrichment coefficient method showed that the enrichment coefficients were weak, and the pattern of heavy metal enrichment ability of asparagus was Cr > Zn > Mg > Cd > Cu > Ca > Ni > Hg > Mn > Pb > Fe > As. By the analysis of human health risk assessment model for adults and children, the pattern of non-carcinogenic risk of five heavy metals was Cr > Cd > Pb > Hg > As, and the pattern of carcinogenic risk was ranked Cr＞Cd＞As.

In conclusion, through the analysis of salinity characteristics, heavy metal and related ion contents and risks of asparagus and planting soil in Chongming Island, this paper showed that asparagus and its planting environment in Chongming Island were safe and reliable, and provided a theoretical basis for the planting and sales promotion of Chongming asparagus.