行政院國家科學委員會專題研究計畫期中進度報告:台灣烏腳病地區養殖生態系主要環境成份中砷物種轉移之研究﹝2/3﹞

Arsenic is a known environmental
carcinogen with its toxicity depending on its
chemical forms. The objective of the study
is to investigate the transformation of arsenic
speciation among different compartments,
such as water, fish, and sediment, of cultural
ponds. In the first year, the work was to
develop and establish an analytical method
of redox sensitive arsenic speciation and to
optimize this method. Distribution of arsenic
speciation in cultural ponds in the blackfoot
disease epidemic area was also investigated.
In the second year, the isothermal sorption of
batch experiment for arsenic species and
sediment among water and sediment were
performed for sediments from five local
culture ponds. The result indicated that for
the sediment, the total arsenic concentration
ranges from 14 mg/kg to 39 mg/kg, and the
specific gravity and the void ratio lie on
2.24-2.68 and 0.50-0.64, respectively. The
variation of the specific gravity and the void
ratio is small. The content of organic material
possesses negative correlation with the total
arsenic concentration of the sediment in the
sampled ponds. The result of the isothermal
sorption of batch experiment for the
sediment in the field indicated that the
adsorption isotherm for both As3+ solution
and mixed equal concentrations solution
(As3+ /As5+) belongs to C type revealing that
the ratio of the distribution for As3+ between
water and the adsorption surface of the
sediment is constant. The adsorption
isotherm for As5+ solution belongs to L type
revealing that the adsorptive affinity of As5+
is less than that of water molecule.