Abstract
A pot experiment was performed to study the effectiveness of remediation using different plant species and the enzyme response involved in remediating PAH-contaminated soil. The study indicated that species Echinacea purpurea, Festuca arundinacea Schred, Fire Phoenix (a combined F. arundinacea), and Medicago sativa L. possess the potential for remediation in PAH-contaminated soils. The study also determined that enzymatic reactions of polyphenol oxidase (except Fire Phoenix), dehydrogenase (except Fire Phoenix), and urease (except Medicago sativa L.) were more prominent over cultivation periods of 60d and 120d than 150d. Urease activity of the tested species exhibited prominently linear negative correlations with alkali-hydrolyzable nitrogen content after the tested plants were cultivated for 150d (R2 = 0.9592). The experiment also indicated that alkaline phosphatase activity in four of the five tested species (Echinacea purpurea, Callistephus chinensis, Festuca arundinacea Schred and Fire Phoenix) was inhibited during the cultivation process (at 60d and 120d). At the same time, the study determined that the linear relationship between alkaline phosphatase activity and effective phosphorus content in plant rhizosphere soil exhibited a negative correlation after a growing period of 120d (R2 = 0.665). Phytoremediation of organic contaminants in the soil was closely related to specific characteristics of particular plant species, and the catalyzed reactions were the result of the action of multiple enzymes in the plant rhizosphere soil.
Highlights
Contamination by polycyclic aromatic hydrocarbons (PAHs) in the environment has become increasingly problematic with economic development, increasing energy consumption, and heavy emission of industrial “three wastes,”etc [1]
It was found that the degradation rate of PAHs in rhizosphere soils of the five tested plants was still somewhat increased after the plants were cultivated for 150d; the degradation rate of PAHs of four of the tested plants (#1(Echinacea purpurea), #3(Festuca arundinacea Schred), #4(Fire Phoenix) and #5(Medicago sativa L.)) exceeded 90% after being cultivated for 150d, reaching 92.91%, 97.59%, 99.4% and 98.11%, respectively
The results indicated that grasses and legumes enhance the removal of PAHs from contaminated soils
Summary
Contamination by polycyclic aromatic hydrocarbons (PAHs) in the environment has become increasingly problematic with economic development, increasing energy consumption, and heavy emission of industrial “three wastes (waste water, waste gas, waste residue),”etc [1]. Many countries have placed PAHs onto blacklists of priority-monitored pollutants as PAHs have strong “three disease-causing” effects (carcinogenic, teratogenic and mutagenic), persistence in the environment, bio-accumulative characteristics and toxicity [2, 3]. Effect of Rhizosphere Enzymes in PAH-Contaminated Soil. PAHs have high hydrophobicity and low bio-degradation properties, which can lead to their accumulation in the environment. A significant amount of recent research has shown that PAH contamination can be measured in air, soil, water, and organisms to differing degrees. PAHs are often adsorbed onto soil particles due to poor water solubility and a high octanol-water partition coefficient. Soil becomes the primary carrier of these compounds and is able to remain undegraded for long periods of time [7, 8, 9]
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