Linuron effects on microbiological characteristics of sandy soils as determined in a pot study

Abstract

The aim of this study was to find what dosages of linuron introduced into soil can be tolerated by microorganisms, and whether a dosage equal to 100-times higher than the predicted environmental concentration (PEC) is harmful. A pot study was performed to determine the effects of the herbicide at PEC (4 mg kg −1 ), 5 times PEC (20 mg kg −1 ), and 100 times PEC (400 mg kg −1 ) on substrate-induced respiration (SIR), four enzyme activities (dehydrogenase, acid and alkaline phosphatases, and urease), ammonification and nitrification rates, plate counts of total bacteria, fungi, N 2 -fixing bacteria, nitrifiers and denitrifiers, and distribution of r-and K-strategists in sandy soils of different texture throughout 28 days of incubation. Linuron increased SIR and ammonification, especially at 100 times PEC. In contrast, a decrease in nitrate concentrations was detected in both soils treated with the highest dosage of linuron. Although some changes in microbial numbers were ascertained, they were transient (i.e. total bacteria, N 2 -fixing bacteria and nitrifiers) or not significant (i.e. total fungi and denitrifiers). Among the enzymes tested, dehydrogenase was the most sensitive to linuron, showing decreased activity for all treatments and two higher dosages in the loamy sand (LS) and sandy loam (SL) soils, respectively. The addition of 100 times PEC of linuron to LS resulted in the domination of slow-growing K-strategists on days 1 and 14. However, r-strategists dominated on both days 1 and 28 in SL. Our results indicate that linuron may disturb indigenous soil microorganisms, especially when released at high concentrations.

Variable Effects of Non-steroidal Anti-inflammatory Drugs (NSAIDs) on Selected Biochemical Processes Mediated by Soil Microorganisms

“…Moreover, a low activity of DHA in soil treated with NSAIDs might be associated with the death of the drug-sensitive part of the microbial population. Similar effects have been demonstrated by many authors in relation to some organic compounds including other pharmaceuticals and pesticides (Fließbach and Mäder, 2004; Cycoń et al, 2010; Conkle and White, 2012; Cui et al, 2013). Dehydrogenases released from dead cells do not accumulate in soil since they undergo rapid degradation.…”

The Role of White-rot Fungi in Herbicide Transformation

“…Along with linuron-degrading fungi, there are some soil bacteria which are able to use herbicide as a source of C and N, resulting in a significant increase in bacterial counts [53]. The latter is confirmed by increased bacterial numbers in soils treated with the high dosage of linuron [47].…”

“…At that, when herbicide concentration increased, the Gram-negative/ Gram-positive bacteria ratio decreased dramatically in the studied soils. Soil treatment with linuron at the dosages of 4-400 mg/kg did not change the fungal numbers significantly in two agricultural soils as compared to the corresponding controls [47]. Sørensen et al explained the observed phenomenon by the presence of linuron-degrading fungi, including different species of Cunninghamella, Mortierella, Talaromyces, Rhizopus, Rhizoctonia, and Aspergillus [52].…”

Functional Diversity of Soil Microbial Communities in Response to the Application of Cefuroxime and/or Antibiotic-Resistant Pseudomonas putida Strain MC1

“…The experiment was conducted using soil classified as a sandy loam [43], the parameters of which were determined using the ISO (International Organization for Standardization) standards [44]. The experiment had a random block system and consisted of three replicates for the control soil and soil contaminated with two concentrations of XM (1 mg/kg and 10 mg/kg soil) and/or inoculated with strain MC1.…”

“…Sustainability 2018, 10, x FOR PEER REVIEW 3 of 18 [44]. The experiment had a random block system and consisted of three replicates for the control soil and soil contaminated with two concentrations of XM (1 mg/kg and 10 mg/kg soil) and/or inoculated with strain MC1.…”