Assessment of heavy methods calculation of some fruit vegetables effective of irrigation water
Pollution of water and soil by heavy metals is increasing and is at an alarming rate. According to the US Environmental Protection Agency (USEPA), 8 metallic elements are ranked in the list of top toxic substances: Pb, As, Hg, Cd, Cr, Ni, Cu, Be.
In recent years, the problem of food poisoning, including green vegetable poisoning, is exploding, the poisoning has caused acute or chronic diseases that seriously affect human health. Green vegetables are an important and indispensable food source in the daily meals of Vietnamese people. Therefore, ensuring the quality and safety of green vegetables needs to be a top concern. Using safe vegetables is both a need and a right of the people. Therefore, research on the effects and accumulation of heavy metals on commercial green vegetables is necessary to contribute to solving the problem of ensuring food safety and protecting the health of consumers.
Leafy vegetables belong to the group with great water demand, the amount of water in vegetables accounts for 75-95% of the weight. Furthermore, heavy metals accumulate in the edible parts of leafy vegetables more than in cereals or fruit trees (Arora et al., 2008; Usda, 2014; Atamaleki et al., 2021). So, when watering with water containing excess heavy metal content, there is a potential risk of accumulation in vegetables, affecting the health of consumers.
The role of metals and plants
Many metal elements are important in the life of organisms, the average metal content in the dry biomass of organisms ranges from 1 to 100 ppm. Higher concentrations are often toxic to organisms. The gap from sufficient to redundant is very narrow. Some metals such as: Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, and Zn are essential elements in plants, used for redox processes, stable Molecular determination, which is a component of many enzymes, regulates osmotic pressure. And some metals have no biological role, not necessary such as Ag, Al, Au, Pb, Hg… will cause long-term toxicity to organisms. These unnecessary metals will take the place of essential metals. At high concentrations, both essential and non-essential metal elements can damage cell membranes, change enzyme properties, and disrupt cell structure and function.
Plants absorb all the elements located around the rhizosphere. To see if a metal is needed or not needed by the plant, it must be removed from the environment to find out:
(1) The ability to complete the life cycle of plants?
(2) Can replace essential metal (micro, macro)?
(3) Metal is direct involvement in metabolism? Plants absorb metals in all three forms: cations (Ca2+), anions (MoO42-) and gases (Hg, Se) through the stomata of leaves. The chemical form of the metal is important because it is related to the plant’s ability to absorb it. For example, Cd forms complexes with chloride, making it difficult for plants to absorb.
Research situation of heavy metals in green vegetables in Vietnam
The studies focused on assessing the status of heavy metals in water used in agriculture and the cumulative absorption of some heavy metals on different foods. The absorption and accumulation of heavy metals on plants are also applied in treatment technologies to remove residual heavy metals in soil and water.
According to the research topic on heavy metal content in bottom mud, in water and some aquatic vegetables such as lotus root, water morning glory, coriander by Dr Bui Cach Tuyen, Rector of the University of Agriculture and Forestry Ho Chi Minh City shows that: Many water and vegetable samples were analyzed from Thanh Loc (District 12), Tham Luong canal (Tan Binh District), wastewater from Vinh Loc Industrial Park, Son Hai Enterprise, and Enterprises. Textile Thang Long (Binh Chanh), Suoi Cai (Thu Duc) is not safe, many types are heavily polluted. Zinc content in water samples grown water spinach in Binh Chanh is 30 times higher than the allowable level. Lead content in 2 samples of water for growing spinach in Thanh Xuan had a lead content of 8,4 – 15,3 times higher than the allowable level. A sample of water for growing water spinach in Thanh Xuan has a lead content 2,24 times higher than the allowable level. A sample of morning glory in Binh Chanh had a lead content of 3,9 times higher than the permitted level. A sample of lotus root in Tan Binh has a lead content 13,65 times higher than the allowable level. The metal content of copper in a water spinach field in Thanh Xuan is twice as high as the permitted level. Zinc content in water spinach ponds in Thanh Xuan is 2 – 4,12 times higher than the allowable level. A lotus pond in Thanh Xuan has a lead content of 1,9 – 2,4 times higher than the allowable level, and a vegetable pond in Thanh Xuan has a lead content of 28,4 – 35,4 times higher than the allowable level.
Luong Thi Hong Van and Nguyen Mai Hue (2002), investigated the content of Pb, As in vegetables and fruits (water spinach, spinach, broccoli, wormwood, sweet potato, banana, papaya, etc.). Grown in the area around Thai Nguyen ferrous metallurgical workshop and obtained the following results: Pb and As content in edible vegetables grown in the area with Thai Nguyen ferrous metallurgical workshop is higher than the safe level allowed since 2 to 6 times.
Vu Dinh Tuan et al. (2004), also investigated the status of heavy metals in soil and vegetable crops in the suburbs of Hanoi, the results showed that: the amount of Pb in 13 samples of vegetables and the amount of Cd in 11 samples of grown vegetables. in Tu Liem, especially the group of seasoning vegetables and cooked leafy vegetables (perilla, coriander, onion, garlic, marjoram, water spinach, kohlrabi, spinach…) are beyond the permitted standards of Vietnam.
Le Duc et al (2005) studied the effects of Pb2+, Cu2+ on earthworms, vegetables and the effects of Pb, Cu, Zn, Cd on plants on alluvial soil of the Red River. The results showed that the direct influence of Pb2+, Cu2+ on the germination of cruciferous vegetables as well as rooting, leaf production and the average height of mustard plants, depending on the toxicity of each element (Pb, Cu, Zn, Cd) at different concentrations of large and small affected the roots as well as causing death of the seedling.
From some analysis results on NACEN there are some recommendations as follows:
For vegetable growers:
– Use water for vegetable irrigation that is not contaminated by heavy metals in industrial zones
– Use fertilizers that meet standards and have clear origins
– Do not use plant protection chemicals of unknown origin, banned or restricted in use
– Establish safe, standard vegetable production processes.
– If vegetables are grown in a soil environment with a zinc content of about 56 mg/Kg of soil and Zn concentration in irrigation water is 2 ppm, vegetable growers should not prolong the harvest time after 30 days.
– Do not use vegetables of unknown origin
– Do not use vegetables with unusual colours and strange flavours
– Do not use vegetables originating from industrial parks and processing zones when using vegetables should be washed before cooking.
- Arora M., Kiran B., Rani S., Rani A., Kaur B. & Mittal N. (2008). Heavy metal accumulation in vegetables irrigated with water from different sources. Food Chemistry. 111(4): 811-815.
- Atamaleki A., Yazdanbakhsh A., Fakhri Y., Salem A., Ghorbanian M. & Mousavi Khaneghah A. (2021). A Systematic Review and Meta-analysis to Investigate the Correlation Vegetable Irrigation with Wastewater and Concentration of Potentially Toxic Elements (PTES): A Case Study of Spinach (Spinacia oleracea) and Radish (Raphanus raphanistrum subsp. sativus). Biological Trace Element Research. 199(2): 792-799
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