Abstract
Widespread use of chemical fertilizers in agricultural activities poses a high risk of multi-micro metal contamination in soils and potentially causes health issues through consumption of contaminated foods. Bio-organic fertilizers from sewage sludge have been regarded as a suitable substitute for chemical fertilizer for rice farming. In this study, we investigated accumulation of heavy metals (Cu and Zn) in soil, water and rice plant in three pilot-scale rice paddy fields treated with different fertilization schemes. The control field was treated with conventional chemical fertilizers while the soil of two treatment fields was mixed with biological sewage sludge obtained from a local wastewater treatment system in Vietnam at different ratios (1% and 3%). Initial results showed that heavy metals accumulated in the soil, water, and rice plant at varying levels and most of the Cu and Zn contents found in soils, water and rice products exceeded permissible Vietnamese standards (QCVN 03: 2008) and US EPA 503. Notably, the rice field whose soil was treated with sludge at 3% ratio showed a significantly lower accumulation of heavy metals in soil, water and in rice plant. However, treatment of sludge at this level seemed to cause higher heavy metal retention in soil after one harvest. Semi-quantitative risk analysis revealed that the risk of metal contamination in soil and water of the control field ranged from medium (RQ index between 0.1 and 1) to high risk (RQ index higher than 1) and that fertilization methods would also affect the level of risk to the environment.
Highlights
Rapid industrialization and urbanization have released a wide array of pollutants into soils, severely affecting agricultural activities and food production chains [1]
Semi-quantitative risk analysis revealed that the risk of metal contamination in soil and water of the control field ranged from medium (RQ index between 0.1 and 1) to high risk (RQ index higher than 1) and that fertilization methods would affect the level of risk to the environment
We evaluated the levels of heavy metal metal accumulation in the soil, water and agricultural products in two consecutive rice accumulation in the soil, water and agricultural products in two consecutive rice crops crops using sludge as biofertilizer
Summary
Rapid industrialization and urbanization have released a wide array of pollutants into soils, severely affecting agricultural activities and food production chains [1]. Humans could be exposed to heavy metals through consumption of agricultural products grown on those contaminated lands [2,3,4]. This raises the need for close monitoring of soil metal accumulation in maintaining food safety and ensuring ecological sustainability [5]. Continued use of fertilizers and metal-containing pesticides and fungicides might contribute to elevated levels of metals in soils [6]. The accumulation of metals such as Cu, Zn and Cd has been found to be attributable to heavy agrochemical soil treatment [6,7,8,9]
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