Lumbricid macrofauna alter atrazine mineralization and sorption in a silt loam soil

Abstract

Atrazine is a widely used herbicide and is often a contaminant in terrestrial and freshwater ecosystems. It is uncertain, however, how the activity of soil macrofauna affects atrazine fate and transport. Therefore, we investigated whether earthworms enhance atrazine biodegradation by stimulating herbicide degrading soil microflora, or if they increase atrazine persistence by facilitating herbicide sorption. Short (43 d) and medium term (86 d) effects of the earthworms Lumbricus terrestris and Aporrectodea caliginosa on mineralization, distribution, and sorption of Uring-14 C atrazine and on soil C mineralization was quantified in packed-soil microcosms using silt loam soil. A priming effect (stimulation of soil C mineralization) caused by atrazine supply was shown that likely lowered the earthworm net effect on soil C mineralization in atrazine-treated soil microcosms. Although earthworms significantly increased soil microbial activity, they reduced atrazine mineralization to 14 CO 2 -C from15.2 to 11.7% at 86 d. Earthworms facilitated formation of non-extractable atrazine residues within C-rich soil microsites that they created by burrowing and ingesting soil and organic matter. Atrazine sorption was highest in their gut contents and higher in casts than in burrow linings. Also, gut contents exhibited the highest formation of bound atrazine residues (non-extractable atrazine). Earthworms also promoted a deeper and patchier distribution of atrazine in the soil. This contributed to greater leaching losses of atrazine in microcosms amended with earthworms (3%) than in earthworm-free microcosms (0.003%), although these differences were not significant due to high variability in transport from earthwormamended microcosms. Our results indicated that earthworms, mainly by casting activity, facilitated atrazine sorption, which increased atrazine persistence. As a consequence, this effect overrode any increase in atrazine biodegradation due to stimulation of microbial activity by earthworms. It is concluded that the affect of earthworms of atrazine mineralization is time-dependent, mineralization being slightly enhanced in the short term and subsequently reduced in the medium term.

The earthworm Aporrectodea caliginosa stimulates abundance and activity of phenoxyalkanoic acid herbicide degraders

“…Earthworm-mediated stimulation of MCPA degradation Microbial MCPA degradation in soil was stimulated by earthworms (Figures 2 and 3), which extends previous reports on earthworm-stimulated herbicide degradation in certain soils to MCPA (Pivetz and Steenhuis, 1995;Mallawatantri et al, 1996;Meharg, 1996;Gevao et al, 2001;Binet et al, 2006). As earthworms represent the dominant macrofauna in many soils and strongly interact with the soil microbial community (Edwards and Bohlen, 1996;Drake and Horn, 2007), such findings highlight the importance of earthworms for degradation of xenobiotics.…”

Effects of endogeic earthworms on the soil organic matter dynamics and the soil structure in urban and alluvial soil materials

“…Microcosms were filled up with 942 cm 3 of urban (U) and alluvial (A) soil materials (PVC pipe, 12 cm in height × 10 cm in internal diameter; Binet et al, 2006), that is equivalent to 1150 g (1.22 g·cm −3 ) of urban and 950 g (1.01 g·cm −3 ) of alluvial soil materials, respectively. Before the experiment, soils were moistened with tap water until the water hold capacity, respectively 0.29 and 0.33 g·g −1 for urban and alluvial soil materials.…”

“…The sodium hydroxide coming from the beaker was then mixed with barium chloride in excess (20%) and titration (877 Titrino plus, Methrom) was made with hydrochloric acid (0.5 M) until the stoichiometric point (pH 8.6) to measure soil respiration (Binet et al, 2006). The amount of ammoniac N-NH 4 + and nitrates N-NO 3 − were respectively measured after extraction with H 2 SO 4 (0.5 M) and KCl (0.5 M) by spectroscopy at 636 nm and 410 nm, respectively (Scheiner, 2005).…”

Biotecnologias De Remediação De Solos Contaminados Com Agroquímicos

“…Efeitos positivos de diferentes espécies de minhocas na remoção de distintos contaminantes como pesticidas, metais pesados e petróleo, tem sido relatados em muitos estudos (FARENHORST et al 2000;SINGER et al, 2001;LANGENBACH et al, 2002;LUEPROMCHAI et al, 2002;BINET et al, 2006;CONTRERAS-RAMOS et al, 2008;GEISSEN et al, 2008;HICKMAN & REID, 2008;KELSEY et al, 2011;TEJADA & MASCIANDARO, 2011). O Quadro 6 apresenta algumas espécies de minhocas testadas para remoção de contaminantes orgânicos do solo relatados por diversos autores.…”