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In saline water ponds in the tropics, a halocline may occur due to rainfall, especially in the rainy season. The critical impacts of haloclines in saline water ponds are heat insulation and the obstruction of vertical mixing. Considering the water quality in saline water ponds, the appearance of a halocline could have an impact on its variation, as the pond water quality may be impacted by both heat insulation and the obstruction of vertical mixing. Especially in saline water ponds with the purpose of aquaculture production, the appearance of a halocline may lead to dangerous risks, such as physiological stress on aquaculture products, increases in pathogenic micro-organisms, and deterioration of water quality. In the present study, the impact of the appearance of a halocline on physical water qualities was investigated by analyzing continuous on-site observation data obtained in Thailand. It was found that, after the appearance of the halocline, the heat was stored in the lower high-salinity layer, due to the heat insulation effect of the halocline. Furthermore, the halocline was also suggested to have an impact on the transportation of turbidity and to change the DO (dissolved oxygen) distribution in the vertical direction. These results are expected to provide information for assessment of the risk in saline water ponds and to contribute to a new approach for understanding deterioration problems in saline water aquaculture ponds.
Akinori Ozaki; Panitan Kaewjantawee; Thinh Nguyen Van; Masaru Matsumoto. Halocline Induced by Rainfall in Saline Water Ponds in the Tropics and Its Impact on Physical Water Quality. Water 2021, 13, 1889 .
AMA StyleAkinori Ozaki, Panitan Kaewjantawee, Thinh Nguyen Van, Masaru Matsumoto. Halocline Induced by Rainfall in Saline Water Ponds in the Tropics and Its Impact on Physical Water Quality. Water. 2021; 13 (14):1889.
Chicago/Turabian StyleAkinori Ozaki; Panitan Kaewjantawee; Thinh Nguyen Van; Masaru Matsumoto. 2021. "Halocline Induced by Rainfall in Saline Water Ponds in the Tropics and Its Impact on Physical Water Quality." Water 13, no. 14: 1889.
The torrential rains that hit northern Kyushu, Japan, on July 5–6, 2017, caused serious damage, especially in Asakura City, Fukuoka Prefecture, and in Hita City, Oita Prefecture. The primary meteorological mechanism that caused these torrential rains can be summarized as record-breaking heavy rains caused by linear rainbands in northern Kyushu. These heavy rains triggered hillside collapse, with the massive volume of driftwood and soil destroying downstream areas. Shortly after the immediate damage caused by the torrential rains was confirmed, the agricultural reservoirs were suspected to have exacerbated the flood damage in downstream areas. However, it is considered that the reservoirs helped mitigate flood impacts. To verify the disaster mitigation effect of the reservoirs on these torrential rains, the Japan Society of Irrigation, Drainage and Rural Engineering organized a survey team to investigate the damaged agricultural reservoirs in Asakura City. From the survey, four of 11 surveyed reservoirs were confirmed ravaged because of the massive driftwood and soil volume from the hillside area. However, the other reservoirs remained intact, and two distinctive characteristics were found to have helped prevent the flood from worsening. One was the reservoirs’ capacity to store soil; they had a large water capacity, and their strong walls kept the soil inside at their full water level. The other was spillway type and location. The reservoirs that had side-overflow spillways were able to discharge driftwood. Therefore, the water storage capacity of the reservoirs, dike strength, and spillway type and location are important factors that may help mitigate flooding.
Akinori Ozaki; Kazuaki Hiramatsu; Takehide Hama. Survey of agricultural reservoirs damaged by the July 2017 torrential rains in northern Kyushu, Japan. Paddy and Water Environment 2019, 17, 237 -246.
AMA StyleAkinori Ozaki, Kazuaki Hiramatsu, Takehide Hama. Survey of agricultural reservoirs damaged by the July 2017 torrential rains in northern Kyushu, Japan. Paddy and Water Environment. 2019; 17 (2):237-246.
Chicago/Turabian StyleAkinori Ozaki; Kazuaki Hiramatsu; Takehide Hama. 2019. "Survey of agricultural reservoirs damaged by the July 2017 torrential rains in northern Kyushu, Japan." Paddy and Water Environment 17, no. 2: 237-246.
Heavy metal (Cr, Cu, Zn, As, Cd, and Pb) contamination in irrigation water, soil, and vegetables was investigated in farmland adjacent to a multi-industry zone in Bangladesh in dry and wet seasons. In the zone, many factories release wastewater into nearby irrigation canals, and vegetables cultivated with this water could be a major food chain route for human exposure. In the irrigation water and vegetables, heavy metal concentrations exceeded permissible levels in the two seasons, but this was not the case in soil. Zn had the highest concentration, and Cd had the lowest concentration in irrigation water, soil, and vegetables. All heavy metal concentrations were found to be lower in the wet than in the dry season, which is due to the dilution of water by rainfall, lower absorption of heavy metals from the diluted irrigation water, and heavy metal absorption from low concentrated irrigation water and/or soil. The cluster analysis data of irrigation water, soil, and vegetables revealed that the heavy metals in vegetables were considered to be absorbed from irrigation water in the wet season and from soil in the dry season. In the dry season, the high heavy metal concentrations in vegetables might be caused by a high bioconcentration factor (mostly > 20%).
Minhaz Ahmed; Masaru Matsumoto; Akinori Ozaki; Nguyen Thinh; Kiyoshi Kurosawa. Heavy Metal Contamination of Irrigation Water, Soil, and Vegetables and the Difference between Dry and Wet Seasons Near a Multi-Industry Zone in Bangladesh. Water 2019, 11, 583 .
AMA StyleMinhaz Ahmed, Masaru Matsumoto, Akinori Ozaki, Nguyen Thinh, Kiyoshi Kurosawa. Heavy Metal Contamination of Irrigation Water, Soil, and Vegetables and the Difference between Dry and Wet Seasons Near a Multi-Industry Zone in Bangladesh. Water. 2019; 11 (3):583.
Chicago/Turabian StyleMinhaz Ahmed; Masaru Matsumoto; Akinori Ozaki; Nguyen Thinh; Kiyoshi Kurosawa. 2019. "Heavy Metal Contamination of Irrigation Water, Soil, and Vegetables and the Difference between Dry and Wet Seasons Near a Multi-Industry Zone in Bangladesh." Water 11, no. 3: 583.
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−1 and 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.
Thinh Nguyen Van; Akinori Ozaki; Hoang Nguyen Tho; Anh Nguyen Duc; Yen Tran Thi; Kiyoshi Kurosawa. Arsenic and Heavy Metal Contamination in Soils under Different Land Use in an Estuary in Northern Vietnam. International Journal of Environmental Research and Public Health 2016, 13, 1091 .
AMA StyleThinh Nguyen Van, Akinori Ozaki, Hoang Nguyen Tho, Anh Nguyen Duc, Yen Tran Thi, Kiyoshi Kurosawa. Arsenic and Heavy Metal Contamination in Soils under Different Land Use in an Estuary in Northern Vietnam. International Journal of Environmental Research and Public Health. 2016; 13 (11):1091.
Chicago/Turabian StyleThinh Nguyen Van; Akinori Ozaki; Hoang Nguyen Tho; Anh Nguyen Duc; Yen Tran Thi; Kiyoshi Kurosawa. 2016. "Arsenic and Heavy Metal Contamination in Soils under Different Land Use in an Estuary in Northern Vietnam." International Journal of Environmental Research and Public Health 13, no. 11: 1091.