近二十年能源结构调整使我国土壤多环芳烃浓度下降

Soil PAH Concentrations Decrease in China in Response to the Adjustment of the Energy Structure During the Past Two Decades

近几十年来,我国在快速发展和工业化的同时,在环境污染防治方面也做出了巨大努力。然而,这些全国性措施(如能源结构调整)对土壤中污染物浓度的影响尚未得到很好的量化。多环芳烃(PAHs)污染在全球范围内引发重要关注,且PAHs排放与能源结构有关。因此,我们推测我国能源结构的调整可能会降低土壤中PAHs的含量。为了验证这一假设,我们于2008年和2019年在北京54个点位重复采集了土壤样品,分析了美国环境保护署(US EPA)提出的16种优控PAHs化合物(Σ_(16)PAHs)的浓度,并收集了过去20年全国1704个土壤采样点的数据。结果表明,我国Σ_(16)PAHs浓度沿城市-郊区-农村-背景点梯度下降,且Σ_(16)PAHs浓度与区域总产值(GRP)有关,在GRP较低时Σ_(16)PAHs浓度随GRP的增加而增加,随后在GRP达到一定水平时趋于平稳。过去20年,我国土壤Σ_(16)PAH的平均浓度呈下降趋势,其中北京土壤Σ_(16)PAHs的平均浓度从2008年的22.7μg·g^(-1)总有机碳(TOC)显著下降到2019年的10.0μg·g^(-1)TOC。源识别分析推断,土壤PAHs浓度的下降趋势是由于我国煤炭、焦炭、部分油类消费量下降以及电力、天然气等清洁能源消费量上升所致。本研究例证了调整能源结构在降低土壤多环芳烃浓度和改善土壤环境质量中的重要作用。

China has made great efforts to fight environmental contamination along with rapid development and industrialization over the past few decades.However,the effects of these nationwide measures,such as energy restructuring,on pollutant residuals in soil have not been well quantified.Polycyclic aromatic hydrocarbon(PAH)pollution is a major concern around the world,and PAH emissions are associated with the energy structure.Therefore,we speculated that the adjustment of the energy structure in China may reduce the content of PAHs in soil.To test this hypothesis,we measured the concentrations of sixteen US Environmental Protection Agency(US EPA)priority PAH compounds(Σ_(16)PAHs)at 54 soil sampling sites in Beijing in 2008 and 2019 and compiled nationwide data for 1704 soil sampling sites in the past two decades.The results showed that the Σ_(16)PAH concentrations descended along the urban-suburban-rural-background gradient,and they first increased with increasing gross regional production(GRP)and plateaued when the GRP reached a certain level.The average Σ_(16)PAH concentrations showed a decreasing trend across China over the past 20 years,and they decreased significantly from 22.7μg·g^(-1) total organic carbon(TOC)in 2008 to 10.0 μg·g^(-1) TOC in 2019 in Beijing.The source identification analyses inferred that the decreasing trend of soil PAHs was due to the declines in the consumption of coal,coke,and some oils and the rising consumption of clean energy,such as electricity and natural gas,in China.This study demonstrates the important role of adjusting the energy structure in decreasing soil PAH concentrations and improving soil environmental quality.