Limitations of multimedia models for use in environmental decision making

The United States currently is engaged in a complex,multi-billion dollar effort to cleanup a legacy ofboth privately- and federally-owned hazardous wastesites. Decisions regarding the best approach forremediation of these sites often are based on theanalysis of potential risks to human health and theenvironment. A cornerstone of such analysis is thefrequent use of computerized multimedia environmentaltransport models, to evaluate the large quantities ofinformation necessary to understand the present andfuture implications of contamination at a site. Onebarrier to wide-spread use of this analyticalprocedure is the view that results obtained usingcomputer models are highly dependent on user input,and therefore, subject to manipulation. It is widelyrecognized that for decisions to be both credible andimplementable, the public must have confidence in boththe scientific basis for judgments involved and thedecision processes employed (NRC, 1983). Our purposein this article is to overview the difficultiesassociated with application of multimedia models toreal world problems and the contribution these modelscan make to technically sound estimates of exposure and risk.     

In-situ Treatment of Oiled Sediment Shorelines

Experimental oil spill studies were conducted to quantify the effectiveness of selected in-situ shoreline treatment options to accelerate natural oil removal processes on mixed-sediment (sand and pebble) shorelines. At each of three distinct shoreline sites, treatment test plots and control plots were established within a 40-, 80- and 143-m continuous stretch of oiled shoreline. A total of 5500 l of oil was deposited along a 3-m wide swath in the upper intertidal zone at each site. Approximately one week after oiling, a different treatment technique was applied to each plot. The treatment techniques were: sediment relocation (surf washing), mixing (tilling), bioremediation (fertilizer application), and bioremediation combined with mixing. One plot at each site was monitored for natural attenuation. The quantity of oil removed from the plots was measured six times up to 60 days post-treatment and then again one year later. Changes in the physical character of the beach, oil penetration, movement of oil to the subtidal environment, toxicity, and biodegradation were monitored over the 400-day period.The results verified quantitatively that relocation of oiled sediments significantly accelerated the rate of oil removal from the shoreline by more than one year. Microscopic observations and image analyses confirmed that the oil-mineral aggregate formation process was active and was increased by sediment relocation. Oil biodegradation occurred in this arctic environment, both in the oiled sediments and on the fine mineral particles removed from the sediment by natural physical processes. The biodegradation of oil in sediment was significantly stimulated by simple bioremediation protocols. Mixing (by tilling) did not clearly stimulate oil loss and natural recovery in the context of this experimental design. None of the treatment techniques elevated toxicity in the nearshore environment to unacceptable levels, nor did they result in consequential alongshore or nearshore oiling.     

Spatiotemporal multimedia emission inventory for polycyclic aromatic hydrocarbons near petroleum production plants in China based on a 10′ × 10′ grid

A spatiotemporal model was developed to investigate emissions of polycyclic aromatic hydrocarbons (PAHs) in Daqing, a Chinese city with large petroleum industry plants. The model was based on land-use types determined on a 10′?×?10′ grid. A geographic information system and regression analyses were used to characterise spatial and temporal variations in PAH emissions into multiple environmental media. The simulated results were validated using previously published experimental data, and the model was found to function well. PAH emissions to the atmosphere, soil, and surface water between 1998 and 2013 were estimated. The results indicated that PAH emissions to the atmosphere increased but PAH emissions to the soil and surface water decreased over the study period. PAH emissions to the atmosphere were markedly higher in winter than in summer. PAH emissions were concentrated in urban areas and areas near petroleum production plants, indicating that PAH emissions were closely related to industrial activities. The results will support research into the migration and transformation of PAHs and human health and ecological risk assessments. The results may also be useful for developing policies for controlling PAH pollution and managing risks associated with PAHs.     

基于环境逸度模型的化学物质暴露与风险评估研究进展

工业化学品通过各种迁移转化过程后在环境区间中广泛分布,同时新化学品正被大量的生产并进入环境,使得对于化学品管控的需求和压力不断增加。基于这一背景,多国政府颁布了相应的政策法规对化学品进行管控。除了用相应的政策法规进行预先管控之外,使用基于逸度概念的多介质环境模型来表征化学品的行为与归趋是一个相对简单而有效的方法,不仅适用于环境中存在的现有化学品的暴露评估,也成为各国化学品管理中对新化学品的环境暴露进行预测的有力工具。本文综述逸度概念与方法、相关环境模型、建模过程、应用验证等方面的国内外研究进展,希望能够对我国化学品环境暴露评估与风险评估的模型构建、优化与方法应用提供信息和借鉴。     

Fate of tetracyclines in swine manure of three selected swine farms in China

Veterinary antibiotics can enter the environment due to the common practice of land application of manure from treated animals. The environmental fate of tetracyclines in swine manure after composting and field application remains largely unknown. This study analyzed the concentrations of tetracyclines in manure, manure-based compost and compost amended soil in selected swine farms from Beijing, Jiaxing and Putian, China to determine the dilution effects of antibiotics when released into the soil environment. The results demonstrate that residues of antibiotics were detected in all samples and chlortetracycline as well as its degradation products should be regarded critically concerning their potential ecotoxicity. Application of manure-based compost to soil could reduce the possible risk posed by antibiotic contamination, but the trigger value of 100 μupg/kg was still exceeded in soil samples (776.1 μupg/kg dw) from Putian City after application of compost. Field studies such as the present one can help to improve the routine administration of antibiotic-containing composted manure.     

基于3MRA模型的填埋场安全填埋废物污染物阈值评估方法与应用研究

选取案例填埋场7种目标污染物为研究对象,运用3MRA模型模拟污染物在填埋场周围环境介质中的迁移转化.结果表明,7种目标污染物最低安全填埋阈值大小顺序为:污染物二价镍>苯>镉>铅>六价铬>砷>汞;污染物苯、砷、汞各自的人类和生态受体安全填埋阈值相同,镉和二价镍的人类受体安全填埋阈值高于生态受体,六价铬的生态受体安全填埋阈值高于人类受体,场区地下水的致癌风险和危害商分别为5.06×10-7和2.3×10-1.     

三峡水库水环境中内分泌干扰物TBT的多介质迁移和归趋模拟

运用环境多介质QWASI等量浓度模型模拟了三峡水库水环境中内分泌干扰物TBT在各环境介质中的浓度分布及迁移归趋,同时讨论了三峡水库运行方式对库区水环境中TBT环境行为的影响.结果表明,QWASI模型能够较为合理地给出各个物理化学过程的速率参数,可对TBT在三峡水库这种超大型河道型水库中跨介质间的迁移传输、各环境相分布等作出定性和定量的模拟估计,模型输出结果与实测结果较为吻合.研究表明,三峡水库的运行方式对TBT在库区水环境中沉积物和水相间的迁移转化有重要影响.     

Predicting Streambed Sediment and Water Column Escherichia coli Levels at Watershed Scale

A sub‐model for the Soil and Water Assessment Tool (SWAT) is developed to predict Escherichia coli levels in the streambed sediment as well as in the water column. New formulations to estimate the levels of E. coli in streambed sediment and the water column are derived. These equations include calculations of E. coli resuspension from the streambed sediment to the water column, E. coli deposition from the water column to the streambed sediment, E. coli growth in the streambed sediment and the water column, and instream E. coli routing. These formulations were programmed in FORTRAN and integrated into SWAT. The modified SWAT model was applied to Squaw Creek Watershed, Iowa, to predict E. coli levels in the stream. Escherichia coli concentrations in the streambed sediment and the water column were monitored extensively in this watershed, and observations were used to verify the model predictions. The model proposed here can predict E. coli concentrations in streambed sediment as well as in the water column. Approximately 58% of the predictions of E. coli levels in the bed sediment were within 1 order of magnitude from the observed value, and in the water column 83% of the predictions of E. coli levels were within 1 order of magnitude. Results suggest that the proposed model will help predictions of instream bacterial contamination.     

杀虫剂十氯酮的多介质环境行为模拟

应用EQC模型模拟十氯酮在多介质环境中的归宿和迁移通量.结果表明:土壤是十氯酮最大的贮存库,在稳态平衡条件下,残留率达到95.0%;在稳态非平衡条件下,十氯酮单独排放到水体,有37.5%残留在于排放的水体中,其在大气的浓度水平和质量分布均很低,在沉积物中的质量则来自于水体向沉积物的沉降迁移;十氯酮主要通过水体的水平迁移和土壤的厌氧降解输出;十氯酮的主要界面迁移过程是大气向土壤的迁移,其次是水体向沉积物的沉降和大气向水体的迁移.     

Effects of soil attributes and straw accumulation on the sorption of hexazinone and tebuthiuron in tropical soils cultivated with sugarcane

Brazil is the largest sugarcane producer in the world in which hexazinone (3-cyclohexyl-6-dimethylamino-1-methyl-1,3,5-triazine-2,4-dione) and tebuthiuron (1-(5-tert-butyl-1,3,4-thiadiazol-2-yl)-1,3-dimethylurea) are heavily used. Sugarcane harvesting is changing from the manual system with previous straw burning to the mechanized system without straw burning. The lack of burning results in soil organic carbon accumulation mainly in clayey soils, which should affect herbicides availability and fate. Therefore, we evaluated sorption of these herbicides in soil samples with and without straw burning. Both herbicides presented low apparent sorption coefficients (mean K_d,app= 0.6 and 2.4 L kg^?1 for hexazinone and tebuthiuron, respectively), suggesting that they may leach to groundwater. Moreover, their sorption correlated primarily with soil organic carbon (SOC), but iron oxide contents extracted with ammonium oxalate (Fe₂O₃^AOX) also affected it (K_d,app = ?0.228 + 0.0397 SOC + 0.117 Fe₂O₃^AOX for hexazinone and K_d,app = ?1.407 + 0.201 SOC + 0.348 Fe₂O₃^AOX for tebuthiuron). Soil organic carbon accumulation due to straw maintenance in the field positively affected sorption of both herbicides, but its effects were not enough to classify them as “non-leachers.”