人工湿地去除三唑磷的生物学机制初步研究

Primary study on biological mechanism of removing triazophos by constructed wetland

构建了以陶粒为基质、种植美人蕉(Canna indica)的水平潜流人工湿地小试系统,研究了该人工湿地系统对水体中三唑磷(triazophos,TAP)的去除效果,通过测定基质酶脲酶和碱性磷酸活性、微生物种群特征及植物根系超氧化物歧化酶和过氧化物酶活性,初步探讨了该人工湿地系统去除水体TAP的生物学机制。实验结果表明,在进水TAP浓度分别为0 mg·L-1(对照CW1)、0.1 mg·L-1(低浓度CW2)、1 mg·L-1(中浓度CW3)和5 mg·L-1(高浓度CW4)的条件下,人工湿地对水体中三唑磷具有良好的去除效果,去除率分别是96.4%、96.8%和53.7%。在进水TAP浓度越高的人工湿地系统中,进水端基质脲酶和碱性磷酸酶活性越高。中、高TAP浓度进水的系统中脲酶活性分别高于对照系统21.8%和29.2%。高TAP浓度进水的系统中碱性磷酸酶活性分别高于对照和低浓度进水系统51.7%和36.3%(p<0.05)。比较进水端而言,各系统出水端的酶活性显著降低(p<0.05)。相关性分析结果显示系统TAP的去除与基质中碱性磷酸酶活性呈显著正相关(p<0.05),表明基质中脲酶、碱性磷酸酶在人工湿地去除TAP过程中发挥重要作用。对各人工湿地系统基质中微生物进行分离纯化,并通过16S rDNA基因测序,结果表明,进水含TAP系统的进水端基质中均存在能够促进植物对氮磷营养元素的吸收以及与有机物降解密切相关的菌种,尤其在高TAP浓度进水的系统中发现一株含脱氨酶基因(acds)的菌株,能够促进有机磷降解中间产物—有机胺类的降解转化。此外,美人蕉根系超氧化物歧化酶和过氧化物酶活性在进水TAP浓度升高的情况下,呈现显著增强态势(p<0.05),并正常生长,说明美人蕉对TAP具有较好的抵抗能力。

Four horizontal subsurface constructed wetlands （HSCWs）, which were filled with ceramsite and planted withCanna indica, were constructed. The removal efficiencies of triazophos （TAP） by HSCWs were determined. The enzyme activities of urease and alkaline phosphatase （ALP） and population characteristic of microorganism in the medium and the superoxide dismutase （SOD） and peroxidase （POD） in root of C. indica were investigated to discuss the biological mechanisms in the process of removing TAP. Under the inflow concentration of TAP were 0 mg·L-1 （CW1, control）, 0.1 mg·L-1 （CW2, lower concentration）, 1 mg·L-1 （CW3, medium concentration） and 5 mg·L-1 （CW4, higher concentration）, the removal percentages of TAP were 96.4%, 96.8% and 53.7% in CW2, CW3 and CW4, respectively. The activities of urease and ALP in the medium of the inlet section of CWs went up along with the increasing of inflow TAP. The urease activities in CW3 and CW4 were significantly higher than that in the control （CW1） with 21.8% and 29.2% （P〈0.05）, respectively. While ALP activity in CW4 was significantly higher than those in CW1 and CW2 with 51.7% and 36.3% （P〈0.05）. respectively. Compared to these in inlet section of HSCWs, the activities of these two enzymes decreased significantly in the outlet section of HSCWs （P〈0.05）. Correlation analysis indicated that there was significant positive correlation between TAP removal percentages and ALP activities in the HSCWs （P〈0.05）. These results suggested that urease and ALP play important roles in removing TAP in the HSCWs. By 16S rDNA gene sequences detection, some special microorganisms were isolated from the medium in the inlet section of the HSCWs treated with TAP, which could affect the nitrogen and phosphorus adsorption of plant and the degradation of organic phosphorus. It was notable that a bacterial strain containing deaminase gene （acds）, capable of degrading organic amines, was isolated and identified from the higher TAP concentration inflow HSCW. Additionally, with the increasing discharge of TAP, the activities of SOD and POD in the root of C. indica increased and showed significant differences （P〈0.05） in the four HSCWs. These indicated thatC. indica owns the ability to resist TAP.