Emergence, survival and growth of selected plant species in petroleum-impacted flare pit soils

One of the prerequisites to phytoremediation of hydrocarbon-contaminated soils is that plants be able to germinate and become established in the presence of contaminants. This 5-wk growth chamber study examined the tolerance of five grasses and one legume to petroleum hydrocarbons (PHCs) and associated salts in three weathered, fine-textured, flare pit soils obtained from NE British Columbia. Plant tolerance to these soils was measured by percent seedling emergence (PSE), percent seedling survival (PSS) and 5-wk dry shoot biomass; a non-contaminated control soil was included in the study. The contaminated soils showed a wide range in total PHC concentrations (Soil A: 0.1 %, Soil B: 1.8 %, Soil C: 16 % PHC by mass) and in the recently established Canadian Council of Ministers of the Environment (CCME) PHC Tier 1 fractions 1–4. Electrical conductivity in contaminated soils ranged from 3.00 (Soil B) to 5.16 (Soil A) dS m-1. Medicago sativa (alfalfa, cv. Peace) was sensitive (low PSS, PSE and shoot biomass) to high salinity of Soil A but flourished in Soil B, a soil with F3 a nd F4 (gravimetric) concentrations that exceeded CCME PHC Tier 1 Eco Contact standards for agricultural, residential and parkland soils. When considering the combined effects of PHC and salts, Bromus inermis (smooth brome, cv. Carlton) was the grass most tolerant of contaminants in the weathered industrial soils. Compared to other plants, it consistently produced relatively high PSS, PSE and shoot biomass. Soil C was slightly hydrophobic and all plants showed reduced shoot biomass compared to other soils; however, average shoot biomass for Bromus inermis was almost twice as great as any other plant species growing in this soil. More research on the properties and remediation of historic flare pit soils is warranted. Key words: Hydrocarbons, phytoremediation, soil contamination, soil remediation, CCME, soil toxicity

Toxicity of Flare and Crude Hydrocarbon Mixtures

The toxicity of whole, saturate, and aromatic hydrocarbon mixtures from flare pit and crude oil sources were evaluated usingLumbricus terrestris. Body burden analysis was used to analyze the intrinsic toxicity of the six hydrocarbon mixtures. The major fractions of the whole mixtures, the saturate, and aromatic fractions had different intrinsic toxicities; the aromatics were more toxic than the saturates. The toxicity of the saturate and aromatic fractions also differed between the mixtures. The flare saturate mixture was more toxic than the crude saturate mixture, while the crude aromatic mixture was more toxic than the flare aromatic mixture. The most dramatic difference in toxicity of the two sources was between the flare whole and crude whole mixtures. The crude whole mixture was very toxic; the toxicity of this mixture reflected the toxicity of the crude aromatic fraction. However, the flare whole mixture was not toxic, due to a lack of partitioning from the whole mixture into the lipid membrane of the exposed worms. This lack of partitioning appears to be related to the relatively high concentrations of asphaltenes and polar compounds in the flare pit whole mixture.