Arsenic and Heavy Metal Contamination in Soils under Different Land Use in an Estuary in Northern Vietnam.
Heavy metal contamination of soil and sediment in estuaries warrants study because a healthy estuarine environment, including healthy soil, is important in order to achieve ecological balance and good aquaculture production. The Ba Lat estuary of the Red River is the largest estuary in northern Vietnam and is employed in various land uses. However, the heavy metal contamination of its soil has not yet been reported. The following research was conducted to clarify contamination levels, supply sources, and the effect of land use on heavy metal concentrations in the estuary. Soil samples were collected from the top soil layer of the estuary, and their arsenic (As), chromium (Cr), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn) concentrations were analyzed, as were other soil properties. Most soils in the estuary were loam, silt loam, or sandy loam. The pH was neutral, and the cation exchange capacity ranged from 3.8 to 20 cmol·kg-1. Manganese and iron concentrations averaged 811 µg·g-1and 1.79%, respectively. The magnitude of the soil heavy metal concentrations decreased in the order of Zn > Pb > Cr > Cu > As > Cd. The concentrations were higher in the riverbed and mangrove forest than in other land-use areas. Except for As, the mean heavy metal concentrations were lower than the permissible levels for agricultural soils in Vietnam. The principal component analyses suggested that soil As, Pb, Zn, Cd, and Cu were of anthropogenic origin, whereas Cr was of non-anthropogenic origin. The spatial distribution of concentration with land use indicated that mangrove forests play an important role in preventing the spread of heavy metals to other land uses and in maintaining the estuarine environment.
Graduate School of Integrated Science for Global Society, Kyushu University, Fukuoka 819-0395, Japan. nguyen.van.thinh.999@s.kyushu-u.ac.jp.
Thinh
T
Nguyen Van
Institute of Tropical Agriculture, Kyushu University, Fukuoka 812-8581, Japan. a-ozaki@agr.kyushu-u.ac.jp.
Akinori
A
Ozaki
Soil Science Laboratory, Faculty of Land Management, Vietnam National University of Agriculture, Hanoi 100-000, Vietnam. thohoang2211@gmail.com.
Hoang
H
Nguyen Tho
Soil Science Laboratory, Faculty of Land Management, Vietnam National University of Agriculture, Hanoi 100-000, Vietnam. nda.khd49@gmail.com.
Anh
A
Nguyen Duc
Soil Science Laboratory, Faculty of Land Management, Vietnam National University of Agriculture, Hanoi 100-000, Vietnam. yenngokhd51@gmail.com.
Yen
Y
Tran Thi
Institute of Tropical Agriculture, Kyushu University, Fukuoka 812-8581, Japan. kurosawa@agr.kyushu-u.ac.jp.
Kiyoshi
K
Kurosawa
D000383:Agriculture; D000818:Animals; D017756:Aquaculture; D001151:Arsenic / Q000032:analysis* / Q000378:metabolism; D004784:Environmental Monitoring; D063366:Estuaries; D019216:Metals, Heavy / Q000032:analysis* / Q000378:metabolism; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis* / Q000378:metabolism; D014744:Vietnam; D053833:Wetlands
D019216:Metals, Heavy; D012987:Soil; D012989:Soil Pollutants; D001151:Arsenic
Red River Delta; estuary; heavy metals; soil contamination; spatial distribution