南昌市灰尘中可淋溶态DOM的光谱特性

灰尘中可淋溶态DOM(LDOM)是城市雨水径流中有机质及污染物的重要来源.本文采集南昌市不同功能区及公交站台灰尘样品,利用紫外-可见吸收光谱法及三维荧光光谱法分析了灰尘中LDOM的光谱特性,以期为城市雨水径流污染防治提供数据支持.研究表明:南昌市灰尘总有机碳浓度及有色溶解性有机质(CDOM)浓度均值分别为30.3 g·kg~(-1)和17.67 m~(-1),二者以东西向主干道及赣江沿岸为高值中心向两侧递减.荧光溶解性有机物中的类腐殖物质、紫外-可见吸收光谱参数中的UV_(254)、S_R、UV_(250)/UV_(365)、UV_(240)/UV_(420)均以昌南(近高速路附近)地区较高,说明这些地区灰尘LDOM的分子量小、有机质腐殖化程度高.而类蛋白物质及UV_(253)/UV_(203)均以市区值较高,说明市区灰尘LDOM的自生源特性较高、芳环结构复杂.荧光指数分析结果表明,公园绿地灰尘LDOM的内源及自生源可能性大、腐殖化程度低,而文教区灰尘LDOM的陆源来源可能性大、腐殖化程度高.主成分分析结果表明,以陆源来源为主LDOM的腐殖化程度高、有机质结构复杂、分子量小(如文教区空调灰尘LDOM),以内源自生源为主LDOM的腐殖化程度低、结构中脂肪碳多、分子量大(如公园绿地灰尘LDOM).

Spectral characterization of leaching dissolved organic matter (LDOM) from the dust in Nanchang City

The bus station is one of the significant sinks of urban dust and contaminants. Leaching dissolved organic materials (LDOM) in dust is the important source of the organic matter and contaminants in urban stormwater runoff. This study investigates the spectral characteristics of LDOM in dust, which is sampled from the different functional areas and bus stations in Nanchang City. The aim of this study is to provide vital data for pollution control in urban stormwater runoff. For this purpose, UV-visible absorption spectroscopy (UV-vis) and three-dimensional excitation-emission matrix fluorescence spectroscopy (3D-EEM) were used. Results show that the concentration of the total organic carbon (TOC) and chromophoric dissolved organic matter (CDOM) in dust are 30.3 g·kg^-1 and 17.67 m^-1 (average value), respectively. The maximal TOC and CDOM are located in the east-west main road and the area along the Gan River, and then decrease in the surrounding area. In addition, the relatively high concentration of the humic-like substances and the relatively high value of UV₂₅₄, S_R, UV₂₅₀/UV₃₆₅, and UV₂₄₀/UV₄₂₀ are detected in southern (dust near the highway) area of Nanchang City. These results indicate that LDOM from these areas is characterized by small molecular and high humification. In contrast, the relatively high value of the protein-like substances and UV₂₅₃/UV₂₀₃ is found in the downtown area, which shows similar spatial distribution to that of CDOM. These results reveal that LDOM from the downtown area is mainly autochthonous DOM with more complex aromatic-ring structure. Fluorescence indices analysis indicates that LDOM from the dust in the park mainly derived from the autochthonous origin with low humified DOM. While LDOM from the dust in college mainly derived from the terrestrial sources with a high degree of maturation. Principal component analysis shows that terrestrial LDOM is dominant with higher humification, more complex structure and smaller molecular OM (e.g. LDOM in dust from the air conditioner in college). In contrast, microbial and autochthonous LDOM is characterized by lower humification, more aliphatic carbon in the structure and larger molecular OM (e.g. LDOM in dust from the park).