This study aims to assess the pollution level of groundwater in the Holocene aquifer in the Duy Tien district, Ha Nam province, using the groundwater quality index (GWQI). Groundwater samples were collected from 20 wells and dug wells in households in rainy and dry seasons. The results showed that many parameters such as ammonium, nitrite, total hardness, chloride, Fe, Mn, Pb, As exceeded the permitted limits according to QCVN 09-MT: 2015/BTNMT. In particular, the ammonium concentrations at all monitoring wells were higher 2,73 ÷ 28,3 times than permitted values. The GWQI ranged between 84 ÷ 369 in the rainy season and 67 ÷ 290 in the dry season, while the proportion of wells with "very poor water" quality in the rainy and dry season was 50% and 65%, respectively. The GWQI values can be a scientific basis for effective use and protecting groundwater resources.

Maize samples collected from fields, farm storages, middleman storages and food shops in Vietnam from May 1995 to August 1996 were analyzed for aflatoxin B1. The aflatoxin B1 productivity of Aspergillus flavus and Aspergillus payasitisus strains isolated from maize in North of Vietnam was also shown. The highest average levels of aflatoxin B1 was 130 ppb in maize kernel of Thanh Hoa-Nghe An province. One out of 10 of ear type samples from Ha Tay and two out of 10 of those from Thanh Hoa were contaminated at the level of 20 ppb and 60 ppb of aflatoxin, respectively. No aflatoxin was detected in maize based products. Twenty samples of maize kernel from provinces Ha Tay, Thanh Hoa, Son la in the North of Vietnam were collected for ochratoxin A analysis. Only one out of 20 samples was contaminated with ochratoxin A at the level of 90 ppb.

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This chapter evaluates the contamination of selected persistent organic pollutants (S-POPs) in the sediment of some typical areas in Vietnam. S-POPs are composed of dichlorodiphenyltrichloroethanes (DDTs), hexachlorocyclohexanes (HCHs), polychlorinated biphenyl (PCBs), and polybrominated diphenyl ethers (PBDEs). The collected data and analyzed results indicated the wide occurrence of significant S-POPs residues in studied areas. The main sources of S-POPs are discussed by using composition analyses and diagnostic ratios of S-POPs indicator. Ecotoxicological risk of S-POPs is assessed. The obtained results have contributed to the assessment of S-POPs fate in the environmental sediment in Vietnam.

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