南京城市林业土壤多环芳烃累积特征及其与黑炭的相关性

Accumulation of polycyclic aromatic hydrocarbons and their correlation with black carbon in urban forest soil of Nanjing City,China

【目的】揭示南京城市林业土壤中多环芳烃(PAHs)的累积特征及其与土壤黑炭(BC)的相关性。【方法】采集了南京市城市广场(US)、道路绿化带(RGB)、公园(UP)、居住区(RA)、城市片林(UF)、城郊天然林(URF)等6个典型城市林业功能区18个研究样地3个土壤层次(0~10、≥10~20、≥20~30 cm)共54个土壤样品,分析了土壤中PAHs、BC的含量及土壤p H。【结果】PAHs在各功能区的含量大小依次为:US(975.06 ng/kg)>RGB(614.57 ng/kg)>UP(523.14 ng/kg)>RA(512.01 ng/kg)>UF(273.41 ng/kg)>URF(270.71 ng/kg)。US土壤多环芳烃含量显著高于其他功能区,RGB多环芳烃含量显著高于UP、RA、UF和URF(P<0.05)。各功能区土壤PAHs组成相似,以3环、4环和5环PAHs为主,尤其是以3环PAHs占主导。各功能区土壤中PAHs在3个土层中的含量存在显著差异(P<0.05)。不同功能区的纵向分布规律不同,RGB、US、RA、URF各土层含量从大到小均表现为≥10~20 cm、≥0~10 cm、≥20~30 cm,UP各土层含量从大到小均表现为0~10 cm、≥10~20 cm、≥20~30 cm,UF各土层含量从大到小均表现为0~10 cm、≥20~30 cm、≥10~20 cm。各功能区土壤PAHs的生态风险效应(R_(Bap))大小依次为US>RGB>UP>RA>UF>URF,且R_(Bap)均在1.0~1.6之间,对研究区内的生物潜在危害性较低。土壤中BC的含量与PAHs存在显著相关(R^2=0.74,P<0.05)。【结论】南京市城市林业功能区土壤PAHs含量存在差异,城市广场(US)土壤多环芳烃含量显著高于其他功能区。土壤PAHs组成以3环、4环和5环PAHs为主,尤其是以3环PAHs占主导。土壤PAHs总体表现为随土层加深而下降。各功能区土壤中PAHs的生态风险效应R_(Bap)值较小,对研究区内的生物潜在危害性较低,土壤PAHs与BC显著相关。

【Objective】This study aimed to reveal the accumulation of polycyclic aromatic hydrocarbons（ PAHs） in urban forest soil and their correlation with soil black carbon（ BC） in Nanjing,China.【Method】Fifty-four urban forest soil samples at 18 sites in Nanjing were collected,including three soil layers of 0-10,≥10-20,and ≥20-30 cm,and six typical urban forestry function zones of urban square（ US）,road green belts（ RGB）,urban park（ UP）,residential areas（ RA）,urban forest（ UF）,and urban rural forest（ URF）. The PAH and BC contents,as well as the soil p H values,were analyzed. 【Results 】PAH contents in different function zones were in the following order： US（ 975. 06 ng/kg）〉 RGB（ 614. 57 ng/kg） 〉UP（ 523. 14 ng/kg）〉 RA（ 512. 01 ng/kg）〉 UF（ 273. 41 ng/kg）〉 URF（ 270. 71 ng/kg）. The PAH contents in the US were significantly higher than those in other function zones,and those in RGB were significantly higher than those in the UP,RA,UF and URF（ P〈0. 05）. The composition of soil PAHs in the study areas was similar,mainly with three-ringed,four-ringed,or five-ringed PAHs,with three-ringed PAHs being dominant. The PAH contents in the three soil layers were significantly different among different function zones（ P〈0. 05）. The vertical distribution among different function zones was different,and for the different soil layers in the RGB,US,RA and URF,from highest to lowest,the distribution was ≥10-20,0-10,and ≥20-30 cm; for different soil layers in the UP,from highest to lowest,the distribution was 0-10,≥10-20,and ≥20-30 cm; and for different soil layers in the UF,from highest to lowest,the distribution was 0-10,≥20-30,and ≥10-20 cm. The ecological risk effect（ RBap） of soil PAHs in the different function zones was between 1. 0-1. 6,and from highest to lowest,was US 〉RGB 〉UP 〉RA〉 UF 〉URF,which indicated a low potential harmfulness to organisms in the study area.There were significant correlations between BC and PAH contents（ R^2= 0. 74,P〈0. 05）. 【Conclusion】The PAH contents in soils among different urban forest function zones in Nanjing were different,the PAH content in the urban square（ US） was significantly higher than that in other function zones. Soil PAHs were mainly composed of three-ringed,fourringed,or five-ringed PAHs,with three-ringed PAHs being most dominant. The total soil PAH content decreased with increasing of soil depth as a whole. The ecological risk effect（ RBap） of soil PAHs was small,with a low potential harmfulness to organisms in the study area. Soil PAH content was significantly correlated with BC content.