This study estimated the shadow price of two air pollutants (sulfur dioxide and nitrogen oxides) and carbon dioxide in 867 chemical firms from 2007 to 2012 using a parameterized directional distance function to measure the marginal abatement cost of pollutants. The result is as follows. 1) The average shadow prices of SO₂, NO_x and CO₂ in the sample chemical firms were 59.8 yuan/kg equivalent, 388.13 yuan/kg equivalent and 164 yuan/ton equivalent, respectively. 2) The shadow prices of the three pollutants showed an upward and fragmented trend, implying that traditional target-bound emission reductions policies during the 11th Five-Year-Plan had not been economically effective. 3) By plotting the marginal abatement cost curve (MACC) of chemical industry, we find that in order to achieve the pollution reduction targets set by the 13th Five-Year Plan, the effective environmental tax rate should be much higher than the current environmental tax rate or the average carbon price in the carbon market, which means that the current environmental tax may require some adjustment. The shadow price of nitrogen oxides is much higher than that of sulfur dioxide, therefore the tax rate of nitrogen oxides may need a certain degree of adjustment. The results can provide some reference for the future establishment of a more complete system of environmental tax.

以化工行业为例, 利用参数化的方向性距离函数估算2007—2012年867家化工企业两种空气污染物(二氧化硫和氮氧化物)和二氧化碳的影子价格, 衡量污染的边际减排成本, 得到如下结果: 1) 样本化工企业二氧化硫、氮氧化物和二氧化碳的平均影子价格分别为59.8 元/千克当量、388.13 元/千克当量和164元/吨当量; 2) 研究时段二氧化硫、氮氧化物和二氧化碳的影子价格总体上有所提升, 但分布变得更为分散, 企业间边际减排成本差异变大, 说明“十一五”期间的行政手段未实现经济有效的减排; 3) 通过绘制化工行业边际减排成本曲线发现, 要实现“十三五”规划中的污染减排目标, 有效的环境税税率需要远远高于目前的环境税税率或碳市场平均碳价, 意味着目前的环境税仍有很大的提升空间, 其中氮氧化物的有效税率远远高于二氧化硫, 未来氮氧化物的税率可能需要一定幅度的调整。研究结果可为建立更加完备的环境税体系提供一定的科学依据。