Adsorption Characteristics of Oxytetracycline by Different Fractions of the Organic Matter from Humus Soil: Insight from Internal Structure and Composition

Impact of land use-induced soil heterogeneity on the adsorption of fluoroquinolone antibiotics, tested on organic matter pools

The effects on the adsorption of fluoroquinolone antibiotics of long-term soil heterogeneity induced by land-use were investigated. Three different land use areas with their two organic matter (OM) pools were tested for the adsorption of three antibiotics widely detected in the environment (ciprofloxacin, norfloxacin, ofloxacin). The soils were separated into two size fractions, > 63 µm fraction and < 63 µm fractions for the fast and slow OM pools, respectively. Any effect of land use on adsorption was only observed in the slow pool in the increasing order: arable land, grassland, and forest. The composition of the soil organic matter (SOM) did influence adsorption in the slow pool, but not in the bulk soilsThis was, because: 1) the ratio of the slow pool was low, as in forest, 2) the ratio of the slow pool was high but its adsorption capacity was low due to its SOM composition, as in arable land and grassland. Soils containing a large slow SOM pool fraction with aliphatic dominance were found to be more likely to adsorb micropollutants. It is our contention that the release of contaminated water, sludge, manure or compost into the environment should only be undertaken after taking this into consideration.

Side effects of the addition of an adsorbent for the nitrification performance of a microbiome in the treatment of an antibiotic mixture

This work determined the effect of biochar (BC) as an adsorbent on the nitrifying microbiome in regulating the removal, transformation, fate, toxicity, and potential environmental consequences of an antibiotic mixture containing oxytetracycline (OTC) and sulfamethoxazole (SMX). Despite the beneficial role of BC as reported in the literature, the present study revealed side effects for the nitrifying microbiome and its functioning arising from the presence of BC. Long-term monitoring revealed severe disruption to nitratation via the inhibition of both nitrite oxidizers (e.g., Nitrospira defluvii) and potential comammox species (e.g., Ca. Nitrospira nitrificans). Byproducts (BPs) more toxic than the parent compounds were found to persist at a high relative abundance, particularly in the presence of BC. Quantitative structure-activity relationship modeling determined that the physicochemical properties of the toxic BPs significantly differed from those of OTC and SMX. The results suggested that the BPs tended to mobilize and accumulate on the surface of the solids in the system (i.e., the BC and biofilm), disrupting the nitrifiers growing at the interface. Collectively, this study provides novel insights, demonstrating that the addition of adsorbents to biological systems may not necessarily be beneficial; rather, they may generate side effects for specific bacteria that have important ecosystem functions.

Simultaneous reductions in antibiotics and heavy metal pollution during manure composting

The co-existence of antibiotics and heavy metal (HM) is common in manure. However, existing strategies for improving antibiotic dissipation or HM immobilization during composting rarely consider their combined pollution. In this study, we used agricultural lime and a newly designed attapulgite-activated carbon composite (AACC) to enhance the stabilization of HMs in a pilot-scale swine manure composting system and assessed the effectiveness of these materials for removing antibiotic residues. Results indicated that the application of either lime or AACC simultaneously enhanced HM immobilization and antibiotic degradation. In particular, the addition of AACC reduced the enrichment of Cr, Cd, Pb, and As during composting and decreased the half-lives of the antibiotics from 10.7 days to 6.3 days, which were more effectively than lime. The physicochemical and microbiological responses to different additives were subsequently studied to understand the mechanisms underlying the fates of HMs and antibiotics. High HM stress in manure inhibited antibiotic dissipation, but metal immobilization alleviated this effect. The AACC accelerated HM immobilization by surface adsorption and metal precipitation, and this enhancement strengthened during the late composting stage due to an increase in pH, whereas lime exhibited a short-term effect. Moreover, the AACC addition enhanced the contribution of bacteria to changes in antibiotic concentrations, while the increase in pile temperature could be a major factor that contributed to the acceleration of antibiotic degradation after the addition of lime. Characterization of the final compost further showed that AACC-treated compost had the lowest residual concentrations of HMs and antibiotics, higher mortality of ascarid egg, improved nitrogen conversation, and reduced phytotoxicity. Thus, co-composting of swine manure with AACC is a promising approach for producing safer compost for use in agriculture.

Effect of humic acid on oxidative stress and neuroprotection in traumatic spinal cord injury: an experimental study

Background/aim

Traumatic spinal cord injury (TSCI) is an important health problem, especially in developing countries with additional socioeconomic loss. Humic acid (HA) usually has antioxidant, antiinflammatory, blood circulating, and antiviral effects. Hence, it was aimed herein to show the effect of HA on neuroprotection in a TSCI model.

Materials and method

A TSCI model was used, in which 24 Wistar albino rats were divided into 4 groups: control group: subjected to only laminectomy; sham group: subjected to laminectomy + TSCI; HA 5 mg/kg group: subjected to laminectomy + TSCI + intraperitoneal (IP) injection of 5 mg/kg of HA; and HA 10 mg/kg group: subjected to laminectomy + TSCI + IP injection of 10 mg/kg of HA. Intracardiac blood samples were obtained preoperatively (preop), and at 1 and 24 h postoperatively (postop). The total antioxidant status (TAS), total oxidant status (TOS) and oxidative stress index (OSI) levels were evaluated in the serum. The motor functions were evaluated using the Modified Tarlov Score at 24 h postop.

Results

There were no significant changes in the TAS values between the sham and HA 5 mg/kg and HA 10 mg/kg groups (p = 0.77/0.21). However there was a significant decrease in the TOS values at 24 h postop when comparing the sham and HA 5 mg/kg groups (p = 0.02). The pathological evaluation showed a significant decrease in the severity of edema, hemorrhage, polymorphonuclear leucocyte (PNL) infiltration, and mononuclear leucocyte (MNL)/macrophage/microglia infiltration when compared with the control group (p < 0.05). There was a significant recovery at the paraplegia level when the HA 5 mg/kg and HA 10 mg/kg groups were compared with the control group (p < 0.001).

Conclusion

The effects of HA in the early stages of TSCI on oxidative stress, histopathological changes, and neurological improvement were investigated herein. It is thought to be a potential therapeutic agent in acute TSCI but needs to be further evaluated to determine the extent of its effect on other neuroprotective pathways in larger series.