热带农业废弃物源生物炭中多环芳烃的分布特征及其生态风险评估

Distribution and Ecotoxicological Risk of Polycyclic Aromatic Hydrocarbons in Biochar Prepared from Tropical Agricultural Wastes

针对热带农业废弃物资源化过程中生物炭安全利用数据不足,以热带农业废弃物[香蕉茎(banana stem,BS)、菠萝叶(pineapple leaves,PL)、荔枝杆(litchi stem,LS)、水稻秆(rice stalk,RS)、椰子壳(coconut shell,COS)、蘑菇渣(mushroom residue,MR)和木薯茎(cassava stem,CAS)]为原料于不同温度(300、500、700℃)下制备生物炭,利用超声辅助提取-QuEChERS-GC-MS测定其中的16种优控多环芳烃(polycyclic aromatic hydrocarbons,PAHs)分布特征,结合原料/生物炭理化因子与制备温度解析PAHs残留影响因素,基于苯丙a芘毒性当量浓度(toxic equivalent concentration of benzo[a]pyrene,TEQ-Ba P)和风险熵值法评价生物炭中PAHs的生态风险。结果表明,∑PAHs处于1217.6~9547.1μg/g,检出率与浓度最高均为萘(naphthalene,NAP)与菲(PHE),2~4环PAHs是生物炭中主要的PAHs类型;生物炭中∑PAHs呈现BS>PL>LS>RS>COS>MR>CAS,不同生物炭中PAHs种类与含量不同,与来源及制备温度相关。冗余分析(RDA)结果显示,生物炭中PAHs含量与生物炭的电导率(electric conductivity,EC)、碳氧比(carbon oxygenratio,C/O)呈正相关,而与碳氢比(hydrocarbon ration,C/H)呈负相关(P<0.05),且与温度密切相关。从毒性当量浓度和风险商(risk quotient,RQ)看,生物炭中PAHs的毒性来源于低环PAHs,且致癌毒性效应较小;生物炭中NAP浓度存在生态风险,其他单体PAH的RQ<0.1,无生态风险,但值得注意的是总PAHs的RQ>1,需加以关注。该结果可为今后热带土壤中生物炭安全利用提供科学依据。

In order to replenish the data on safe biochar utilization as originated from tropical agricultural wastes,biochar was prepared at 300,500 and 700℃from typical tropical agricultural wastes,including pineapple leaves(PL),litchi sticks(LS),coconut shells(COS),banana stems(BS),rice straws(RS),cassava stems(CAS)and mushroom residues(MR).The distribution characteristics of 16 polycyclic aromatic hydrocarbons(PAHs)in biochar were determined by QuEChERS,coupled with gas chromatography-mass spectrometry(GC-MS).Furthermore,the key influencing factors of the PAHs were analyzed by redundancy analysis,based on biochar’s physicochemical properties and preparation temperatures.Then,the ecotoxicological risks of the PAHs were evaluated based on risk quotient method(RQ).The results depicted that the concentration of PAHs was 1217.6 to 9547.1μg/g,with naphthalene(NAP)and phenanthrene(PHE)having the highest detection frequency and level.The arranged concentration level of PAHs was BS>PL>LS>RS>COS>MR>CAS.The main species of the biochar PAHs were significantly different,which was relative to their source and temperature.Redundancy analysis determined that the conductivity(EC),carbon oxygen ratio(C/O),and carbon-hydrogen ratio and temperature had a significant influence on the concentration of PAHs(P<0.01).PAH content was positively correlated with electric conductivity(EC)and carbon oxygen ratio(C/O),and was negatively correlated with hydrocarbon ration(C/H)(P<0.05).Likewise,it was significantly affected by temperature(P<0.01).Risk assessment results depicted that low-ring PAHs contributed to the toxicity of PAHs;thus,the carcinogenic and toxic effects of individual PAHs could be ignored.Except for NAP,the RQ values of the other monomer PAHs were less than 0.1,indicating that no high and medium ecological risks had occurred.However,the total RQ of the PAHs was higher than 1,denoting that greater attention should be paid to the multi-residues of PAHs in biochar.The results of this study could provide a scientific basis for the safe use of biochar in tropical soils.