干旱及半干旱地区油气开采废物道路利用的风险与管控限值区域差异

Regional differences in risk and control limits for road utilization of oil and gas extraction wastes in arid and semi-arid regions

将脱油残渣(OCDRs)充当道路填充材料,是油气开采废物再利用的重要途径。但是现有的资源化风险评估及管控限值均采用全国统一参数模型,未考虑不同区域气象及地理环境的差异,这极大地限制了资源化利用,尤其是对受降雨量相对较少导致污染物释放风险相对较小的干旱及半干旱地区。文中采用淋溶与浸出实验、指数衰减源强模型、污染物瞬态迁移扩散模型,并结合Monte Carlo方法,对干旱及半干旱区域内OCDRs用作路基填料的环境潜在风险、管控限值以及地区差异进行了深入分析。结果表明:三种浸出实验得出的数据与淋溶实验相比非常不稳定。采用淋溶方法预测OCDRs在干旱及半干旱地区14省道路利用条件下暴露点浓度超标概率为0,风险可接受,但是采用传统方法预测风险过高,其中Pb的暴露浓度为三类地下水限值的3.1倍。14省份之间暴露风险以及管控限值差异较大,8种重金属暴露浓度的离散系数在0.53~1.2之间,管控限值的离散系数在1.3~2.7之间,离散程度都较高,且管控限值与降雨量呈现较强的负相关性,这与暴露浓度的规律基本一致。研究表明:传统浸出和风险评估方法体系模型参数均一,不能准确的评估不同地区OCDRs中污染物的潜在风险。亟待加快建立固废资源化风险评估方法标准,针对干旱及半干旱地区不同区域对应风险与管控限值的巨大差异,应根据各地区具体情况对有害物质实施差异化的管控,推进形成固废资源化风险分区分类分级管控体系。

Utilizing oilfield cuttings drilling residues(OCDRs) as roadbed fill material represents a significant pathway for the recycle of wastes from oil and gas extraction.However,the current resource utilization risk assessment and control limits adopt a unified national parameter model,failing to consider the differences in meteorological and geographical environments across regions,it greatly limits the resource utilization,especially in arid and semi-arid areas where the risk of pollutant release is relatively lower due to less rainfall.This paper employs leaching and percolation experiments,an exponential decay source strength model,and a transient pollutant migration and diffusion model,combined with the Monte Carlo method,to conduct an in-depth analysis of potential environmental risks,control limits,and regional differences in using OCDRs as roadbed fill in arid and semi-arid regions.The results indicate that the data obtained from three types of leaching experiments are very unstable compared to the percolation experiments.using the percolation method to predict the exposure point concentration of OCDRs under road use conditions in 14 provinces in arid and semi-arid areas resulted in a zero probability of exceeding the standard,indicating an acceptable risk.However,the risk of using traditional methods to predict was too high,with the exposure concentration of Pb being 3.1 times the limit set for Class III groundwater quality.There were significant differences in exposure risks and control limits among the 14 provinces,with the coefficient of variation for the exposure concentrations of eight heavy metals ranging between 0.53 and 1.2,and the coefficient of variation for control limits ranging between 1.3 and 2.7,both showing a high degree of dispersion.Moreover,control limits show a strong negative correlation with rainfall,consistent with the pattern of exposure concentrations.The study demonstrates that the uniform model parameters in traditional leaching and risk assessment methods cannot accurately assess the potential risks of pollutants in OCDRs in different regions.There is an urgent need to establish standardized risk assessment methods for solid waste resource utilization,taking into account the significant differences in risks and control limits across different regions in arid and semi-arid areas.It is recommended to implement differentiated control of hazardous substances according to the specific conditions of each region,promoting the development of a classified and graded control system for solid waste resource utilization risk based on regional zoning.