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溶解的天然有机质(DOM)会影响水环境中砷(As)的存在形式。在环境相关的砷/溶解有机质(DOC)比率和p H条件下,使用平衡透析法研究了As(Ⅲ)和As(Ⅴ)络合到两种商业腐植酸的条件分布系数(Dom)。在所有p H值范围内,As(Ⅴ)比As(Ⅲ)能更好地络合到腐植酸上,p H值为7左右时腐植酸的络合能力最强,因为在低p H值时,H+会与As竞争络合位点;而在高p H值时,OH-会与腐植酸竞争As。对于这两种氧化态,Dom的值会随着As/DOC比率减少而增加。对As(Ⅲ)和As(Ⅴ)来说,Dom值可以和As/DOC比值拟合为一个函数。在相同的条件下,陆生的腐植酸与As的络合能力比水生的腐植酸高1.5~3倍。在As/DOC比值较低时,Al3+也可以与As竞争络合位点。在正常环境条件下,约10%的As(Ⅴ)可以与天然有机质络合,而只有在As/DOC比值较低时,才会有>10%的As(Ⅲ)被络合到腐植酸上。在将As络合到自然有机物上时,应考虑到自然环境。
Dissolved natural organic matter (DOM) affects the presence of arsenic (As) in the aquatic environment. Under conditions of arsenic / dissolved organic matter (DOC) and p H at ambient conditions, the equilibrium distribution (Dom) of As (III) and As (V) complexation to two commercial humic acids was investigated using equilibrium dialysis. As (Ⅴ) complexed to humic acid better than As (Ⅲ) at all p H values. The humic acid complexation ability was the highest at p H of about 7, because at low p H , H + competes with As for competing complex sites, whereas OH- competes with humic acid for As at high p H values. For both oxidation states, the Dom value increases as the As / DOC ratio decreases. For As (III) and As (V), Dom values can be fitted to the As / DOC ratio as a function. Under the same conditions, the humic acid of terrestrial and As is more than 1.5-3 times higher than that of aquatic humic acid. At low As / DOC ratios, Al3 + can also compete with As for complexing sites. Under normal ambient conditions, about 10% of As (V) can complex with native organic matter and only> 10% of As (III) is complexed to humic acid at low As / DOC ratios . When As is complexed to natural organisms, the natural environment should be taken into account.