Improvement of pesticide mineralization in on-farm biopurification systems by bioaugmentation with pesticide-primed soil

Abstract

Microcosms were used to examine whether pesticide-primed soils could be preferentially used over nonprimed soils for bioaugmentation of on-farm biopurification systems (BPS) to improve pesticide mineralization. Microcosms containing a mixture of peat, straw and either linuron-primed soil or nonprimed soil were irrigated with clean or linuron-contaminated water. The lag time of linuron mineralization, recorded for microcosm samples, was indicative of the dynamics of the linuron-mineralizing biomass in the system. Bioaugmentation with linuron-primed soil immediately resulted in the establishment of a linuron-mineralizing capacity, which increased in size when fed with the pesticide. Also, microcosms containing nonprimed soil developed a linuron-mineralizing population, but after extended linuron feeding. Additional experiments showed that linuron-mineralization only developed with some nonprimed soils. Concomitant with the increase in linuron degradation capacity, targeted PCR-denaturing gradient gel electrophoresis showed the proliferation of a Variovorax phylotype related to the linuron-degrading Variovorax sp. SRS16 in microcosms containing linuron-primed soil, suggesting the involvement of Variovorax in linuron degradation. The correlation between the appearance of specific Variovorax phylotypes and linuron mineralization capacity was less clear in microcosms containing nonprimed soil. The data indicate that supplementation of pesticide-primed soil results in the establishment of pesticide-mineralizing populations in a BPS matrix with more certainty and more rapidly than the addition of nonprimed soil.

Robust Linuron Degradation in On-Farm Biopurification Systems Exposed to Sequential Environmental Changes

“…The BMs used were those operated in the first experiment of Sniegowski et al (18). Those BMs were set up in glass cylinders filled with 25% (vol/vol) cut straw (Ϯ0.5 cm 2 ), 25% (vol/vol) peat, and 50% (vol/vol) nonprimed soil C or linuron-primed soil L. Soil L, a sandy loam soil, was treated with linuron in the field on a long-term basis and was shown to contain a linuron mineralization capacity (3), while sandy loam soil C, originating from a building construction site, had no history of linuron treatment.…”

“…BPS microcosms inoculated with nonprimed soils also developed a linuron mineralization capacity but only after a much longer period of linuron supply. In the BPS microcosms containing primed soil, the increase in linuron mineralization capacity was concomitant with the appearance of a Variovorax 16S rRNA gene phylotype associated with cultured linuron-degrading Variovorax strains, suggesting the involvement of this phylotype in linuron degradation in those microcosms (18).…”

“…The addition of pesticide-primed soil to BPS has been proposed as an alternative for bioaugmentation with axenic cultures of specialized pesticide-degrading bacteria to accelerate pesticide degradation and avoid the production of toxic metabolites (7,18). Sniegowski et al (18) showed that bioaugmentation with a linuron-primed soil containing linuron-mineralizing microorganisms immediately resulted in the establishment of a linuron mineralization capacity in BPS microcosms. The size of the linuron-mineralizing populations in the system further increased when the microcosms were fed linuron.…”

“…The matrix in a BPS, designated a biomix, is composed of a mixture of soil, peat, and straw or other organic waste materials (6,9). The addition of pesticide-primed soil to BPS has been proposed as an alternative for bioaugmentation with axenic cultures of specialized pesticide-degrading bacteria to accelerate pesticide degradation and avoid the production of toxic metabolites (7,18). Sniegowski et al (18) showed that bioaugmentation with a linuron-primed soil containing linuron-mineralizing microorganisms immediately resulted in the establishment of a linuron mineralization capacity in BPS microcosms.…”

“…All assays were done in triplicate, and abiotic controls without soil were included. The mineralization rate and the lag time, defined as the period between initiating the experiment and the start of mineralization, were calculated as described by Sniegowski et al (18). Average lag times were statistically compared by means of a t test assuming unequal variance (P Ͻ 0.05).…”