## 1 Introduction  
Toxic heavy metal pollutants are serious global problems, posing health risks to human beings, animals, and plants. Most of the metals concerned occur naturally, but they become concentrated from human industrial activities and accompanying pollution, accumulating in high concentrations in the environment. Once in soil and water, these metals can enter the food chain, and the consumption of contaminated crops can pose a serious risk to human health [1, 2, 3]. The Taiwan government started to monitor soil quality of agriculture land throughout whole of Taiwan in 1981, revealing that 1024 ha of agricultural land was contaminated, of which 319 ha were reported as heavy metal-contaminated soils [4]. Concern regarding heavy metals has been rising due to their longevity in soils and because they are not easily metabolized after ingestion. Hence, they are easily accumulated in metabolic organs, such as liver and kidney, causing various toxic symptoms [5, 6, 7, 8]. The high dose exposure to cadmium (Cd) by ingestion can cause severe irritation to the stomach, followed by symptoms of vomiting and diarrhea. Long-term exposure to low doses causes kidney disease, which damages the renal tubules and impedes the absorption of calcium (Ca), leading to brittle bones that are less resistant to breakage [9]. Although copper (Cu) is an essential element for the human body, exposure to high doses can cause health problems, such as irritation of the respiratory tract and throat, vomiting, diarrhea, fetal growth retardation, or even an increased risk of Alzheimer's disease [10, 11, 12, 13]. When plants absorb nutrients and water from the soil through the roots and pores, heavy metals also enter the plant [1,14,15]. Additionally, studies have shown that the uptake of Cd, Cu, manganese (Mn), and zinc (Zn) by plants correlates with increasing levels of soil contamination [16]. The biomass of vegetables has been shown to be negatively affected by metal contaminants in irrigation water [17]. [PERSON] and [PERSON] [18] carried out field experiments on agricultural land that was adjacent to contaminated sites or by applying untreated sewage to various crops, showing that both natural and man-made pollution had a significant impact on local land and crops. [PERSON] et al. [19] also indicated the high accumulation of metals in rice and in vegetables in four agricultural sites near mining areas in China [20]. Vegetables are valuable sources of many essential micronutrients, such as vitamins C and E [21-23]. These vitamins have the potential to inhibit oxidative stress and regulate the immune system in preventing many chronic diseases such as cardiovascular disease and cancer [21,24,25]. However, some studies have shown that the levels of plant antioxidants are changed following exposure to metal elements [26,27]. In the past, studies on the relationship between heavy metal pollution and plant growth were commonly carried out using field and pot experiments. [PERSON] and [PERSON] [28] used pots containing soil that was artificially contaminated with Cd, and showed that the Cd bioaccumulation factor (BAF) of harvested cabbage was raised as Cd concentration in soil increased. Even though they did not discuss the health risks of ingesting the contaminated cabbage, or conduct a risk assessment, they raised concerns of heavy metal exposure through the food chain. In another case, [PERSON] et al. [29] planted two vegetables (sorrel and amaranth) in pots with contaminated soil that was taken from near an abandoned mine in Hungary, and the accumulated element concentrations indicated that the vegetables that were grown in such soil could have negative health effects on consumers. Pot experiments can be easier, cheaper, and more effective than field experiments, and they can be used to indicate whether land remediation to reduce levels of heavy metals is needed prior to planting. In this study, we used pot experiments to evaluate the accumulation of metal elements in vegetables and their influence on levels of antioxidants.