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Evaluation of the arsenic content in food has always been an important issue due to its high toxicity. This is especially relevant for Vietnam, a country with high arsenic contamination. The present study focuses on the development of a model function to predict As uptake in the vegetable Brassica perviridis as a function of the conditions of plant growth and soil parameters. The content of the As and Fe in the samples was determined by neutron activation analysis at the IBR-2 reactor; the soil pH and total organic carbon content were measured in the Institute of Nuclear Science and Technology –Vietnam Atomic Energy Institute (Hanoi, Vietnam). Obtained data have shown that As uptake in the Brassica perviridis plants grown in northern Vietnam could be presented as a function of soil parameters such as pH, organic carbon content, and Fe content, but is not dependent on As content in soil. Particularly high Fe content in Vietnamese soils contribute to As immobilization and prevent its uptake by plants. Regression Data Analysis was used to extract the model function with good corresponding statistics: correlation factor R > 0.97, the probability p-value of independent variable coefficients in the range from 1.86E-07 to 0.007, and the significance F of the model < 1.49E-11. The obtained values demonstrate the reliability and the trueness of the applied model at given soil characteristics and conditions of plants cultivation. The concertation of As in irrigating water could be regarded as the main source of the As uptake in plants and need to be investigated. [ABSTRACT FROM AUTHOR]

Concentrations of NH4+, NO3−, PO43−, Na+, K+, Ca2+, Mg2+, F−, Cl−, and SO42− and the isotopic compositions (δ2H and δ18O) in surface water within a sub-catchment of the Nhue River in Hanoi city (Vietnam) were quantified. Based on the concentrations of the constituents, sources of N- and P-nutrients released into the aquatic environment of the region were grouped by their relationships. Additionally, the sources of nutrients in the environment were discussed based on the isotopic signatures of nitrogen in ammonium and nitrate (δ15 N-NH4 and δ15 N-NO3) as well as oxygen in nitrate (δ18O-NO3). The sources of organic carbon in the aquatic environment were discussed using the elemental C to N ratios in organic matter in the surface sediment. Our results showed that the concentrations of ammonium were 25 times and phosphate 3 times higher than the National Standard for quality of surface water that was set up by the Ministry of Natural Resources and Environment of Vietnam, but nitrate concentration in water was about 400 times lower than the Standard. The δ18O-NO3 to δ15 N-NO3 ratio was found to be 1.38 and [NO3−] negatively correlated (R = − 0.81) with [SO42−] suggesting that denitrification was the reason for the nitrate in surface water of the region to be very low. The results of the study suggest that the sources of nutrients in aquatic environment of the region were from the domestic water waste and influx from inorganic N-P-K fertilizers, but the former source seems to be more important than the latter. The C:N ratio in the organic matter present in surface sediment indicates that domestic water waste was the main source of dissolved organic carbon (DOC) in the water of the region. The brown water waste contributed up to 30% of the stream in the region as estimated by the two-end-member mixing model based on the oxygen 18 signatures of the brown and irrigation water. It is recommended that the Government invests material and financial resources to construct centralized facilities to treat brown water waste to reduce eutrophication in canals of the inner Hanoi city because of intensive urbanizing. [ABSTRACT FROM AUTHOR]