Azithromycin removal using pine bark, oak ash and mussel shell.

Adsorption is considered an interesting option for removing antibiotics from the environment because of its simple design, low cost, and potential efficiency. In this work we evaluated three by-products (pine bark, oak ash, and mussel shell) as bio-adsorbents for the antibiotic azithromycin (AZM). Furthermore, they were added at doses of 48 t ha-1 to four different soils, then comparing AZM removal for soils with and without bio-adsorbents. Batch-type experiments were used, adding AZM concentrations between 2.5 and 600 µmol L-1 to the different bio-adsorbents and soil + bio-adsorbent mixtures. Regarding the bio-adsorbents, oak ash showed the best adsorption scores (9600 µmol kg-1, meaning >80% retention), followed by pine bark (8280 µmol kg-1, 69%) and mussel shell (between 3000 and 6000 µmol kg-1, 25-50% retention). Adsorption data were adjusted to different models (Linear, Freundlich and Langmuir), showing that just mussel shell presented an acceptable fitting to the Freundlich equation, while pine bark and oak ash did not present a good adjustment to any of the three models. Regarding desorption, the values were always below the detection limit, indicating a rather irreversible adsorption of AZM onto these three by-products. Furthermore, the results showed that when the lowest concentrations of AZM were added to the not amended soils they adsorbed 100% of the antibiotic, whereas when the highest concentrations of AZM were spread, the adsorption decreased to 55%. However, when any of the three bio-adsorbents was added to the soils, AZM adsorption reached 100% for all the antibiotic concentrations used. Desorption was null in all cases for both soils with and without bio-adsorbents. These results, corresponding to an investigation carried out for the first time for the antibiotic AZM, can be seen as relevant in the search of low-cost alternative treatments to face environmental pollution caused by this emerging contaminant.

Experimental data and modeling of sulfadiazine adsorption onto raw and modified clays from Tunisia.

In recent years, the increasing detection of emerging pollutants (particularly antibiotics, such as sulfonamides) in agricultural soils and water bodies has raised growing concern about related environmental and health problems. In the current research, sulfadiazine (SDZ) adsorption was studied for three raw and chemically modified clays. The experiments were carried out for increasing doses of the antibiotic (0, 1, 5, 10, 20, and 40 µmol L-1) at ambient temperature and natural pH with a contact time of 24 h. The eventual fitting to Freundlich, Langmuir and Linear adsorption models, as well as residual concentrations of antibiotics after adsorption, was assessed. The results obtained showed that one of the clays (HJ1) adsorbed more SDZ (reaching 99.9 % when 40 µmol L-1 of SDZ were added) than the other clay materials, followed by the acid-activated AM clay (which reached 99.4 % for the same SDZ concentration added). The adsorption of SDZ followed a linear adsorption isotherm, suggesting that hydrophobic interactions, rather than cation exchange, played a significant role in SDZ retention. Concerning the adsorption data, the best adjustment corresponded to the Freundlich model. The highest Freundlich KF scores were obtained for the AM acid-treated and raw HJ1 clays (606.051 and 312.969 Ln µmol1-n kg-1, respectively). The Freundlich n parameter ranged between 0.047 and 1.506. Regarding desorption, the highest value corresponded to the AM clay, being generally <10 % for raw clays, <8 % for base-activated clays, and <6 % for acid-activated clays. Chemical modifications contributed to improve the adsorption capacity of the AM clay, especially when the highest concentrations of the antibiotic were added. The results of this research can be considered relevant as regard environmental and public health assessment since they estimate the feasibility of three Tunisian clays in SDZ removal from aqueous solutions.

Effectiveness of cork and pine bark powders as biosorbents for potentially toxic elements present in aqueous solution.

Cork oak and pine bark, two of the most prolific byproducts of the European forestry sector, were assessed as biosorbents for eliminating potentially toxic elements (PTEs) from water-based solutions. Our research suggests that bioadsorption stands out as a viable and environmental eco-friendly technology, presenting a sustainable method for the extraction of PTEs from polluted water sources. This study aimed to evaluate and compare the efficiency of cork powder and pine bark powder as biosorbents. Specifically, the adsorption of Fe, Cu, Zn, Cd, Ni, Pb and Sn at equilibrium were studied through batch experiments by varying PTEs concentrations, pH, and ionic strength. Results from adsorption-desorption experiments demonstrate the remarkable capacity of both materials to retain the studied PTE. Cork powder and pine bark powder exhibited the maximum retention capacity for Fe and Cd, while they performed poorly for Pb and Sn, respectively. Nevertheless, pine bark showed a slightly lower retention capacity than cork. Increasing the pH resulted in cork showing the highest adsorption for Zn and the lowest for Sn, while for pine bark, Cd was the most adsorbed, and Sn was the least adsorbed, respectively. The highest adsorption of both materials occurred at pH 3.5-5, depending on the PTE tested. The ionic strength also influenced the adsorption of the various PTEs for both materials, with decreased adsorption as ionic strength increased. The findings suggest that both materials could be effective for capturing and eliminating the examined PTEs, albeit with different efficiencies. Remarkably, pine bark demonstrated superior adsorption capabilities, which were observed to vary based on the specific element and the experimental conditions. These findings contribute to elucidating the bio-adsorption potential of these natural materials, specifically their suitability in mitigating PTEs pollution, and favoring the recycling and revalorization of byproducts that might otherwise be considered residue.

Tetracycline adsorption/desorption by raw and activated Tunisian clays.

Clay-based adsorbents have applications in environmental remediation, particularly in the removal of emerging pollutants such as antibiotics. Taking that into account, we studied the adsorption/desorption process of tetracycline (TC) using three raw and acid- or base-activated clays (AM, HJ1 and HJ2) collected, respectively, from Aleg (Mazzouna), El Haria (Jebess, Maknessy), and Chouabine (Jebess, Maknessy) formations, located in the Maknessy-Mazzouna basin, center-western of Tunisia. The main physicochemical properties of the clays were determined using standard procedures, where the studied clays presented a basic pH (8.39-9.08) and a high electrical conductivity (446-495 dS m-1). Their organic matter contents were also high (14-20%), as well as the values of the effective cation exchange capacity (80.65-97.45 cmolckg-1). In the exchange complex, the predominant cations were Na and Ca, in the case of clays HJ1 and AM, while Mg and Ca were dominant in the HJ2 clay. The sorption experimental setup consisted in performing batch tests, using 0.5 g of each clay sample, adding the selected TC concentrations, then carrying out quantification of the antibiotic by means of HPL-UV equipment. Raw clays showed high adsorption potential for TC (close to 100%) and very low desorption (generally less than 5%). This high adsorption capacity was also present in the clays after being activated with acid or base, allowing them to adsorb TC in a rather irreversible way for a wide range of pH (3.3-10) and electrical conductivity values (3.03-495 dS m-1). Adsorption experimental data were studied as regards their fitting to the Freundlich, Langmuir, Linear and Sips isotherms, being the Sips model the most appropriate to explain the adsorption of TC in these clays (natural or activated). These results could help to improve the overall knowledge on the application of new low-cost methods, using clay based adsorbents, to reduce risks due to emerging pollutants (and specifically TC) affecting the environment.

Adsorption of antibiotics on bio-adsorbents derived from the forestry and agro-food industries.

Antibiotic consumption at high levels in both human and veterinary populations pose a risk to their eventual entry into the food chain and/or water bodies, which will adversely affect the health of living organisms. In this work, three materials from forestry and agro-food industries (pine bark, oak ash and mussel shell) were investigated as regards their potential use as bio-adsorbents in the retention of the antibiotics amoxicillin (AMX), ciprofloxacin (CIP) and trimethoprim (TMP). Batch adsorption/desorption tests were conducted, adding increasing concentrations of the pharmaceuticals individually (from 25 to 600 µmol L-1), reaching maximum adsorption capacities of ≈ 12000 µmol kg-1 for the three antibiotics, with removal percentages of ≈ 100% for CIP, 98-99% adsorption for TMP onto pine bark, and 98-100% adsorption for AMX onto oak ash. The presence of high calcium contents and alkaline conditions in the ash favored the formation of cationic bridges with AMX, whereas the predominance of hydrogen bonds between pine bark and TMP and CIP functional groups explain the strong affinity and retention of these antibiotics. The Freundlich's model provided the best prediction for AMX adsorption onto oak ash and mussel shell (heterogeneous adsorption), whereas the Langmuir's model described well AMX adsorption onto pine bark, as well as CIP adsorption onto oak ash (homogeneous and monolayer adsorption), while all three models provided satisfactory results for TMP. In the present study, the results obtained were crucial in terms of valorization of these adsorbents and their subsequent use to improve the retention of antibiotics of emerging concern in soils, thereby preventing contamination of waters and preserving environment quality.

Clarithromycin as soil and environmental pollutant: Adsorption-desorption processes and influence of pH.

Antibiotics pollution is a growing environmental issue, as high amounts of these compounds are found in soil, water and sediments. This work studies the adsorption/desorption of the macrolide antibiotic clarithromycin (CLA) for 17 agricultural soils with different edaphic characteristics. The research was carried out using batch-type experiments, with an additional assessment of the specific influence of pH for 6 of the soils. The results show that CLA adsorption reaches between 26 and 95%. In addition, the fit of the experimental data to adsorption models provided values between 1.9 and 19.7 Ln µmol1-n kg-1 for the KF, Freundlich affinity coefficient, and between 2.5 and 10.5 L kg-1 for Kd, distribution constant of Linear model. Regarding the linearity index, n, it varied between 0.56 and 1.34. Desorption showed lower scores than adsorption, with an average of 20%, and with values of 3.1 and 93.0 Ln µmol1-n kg-1 for KF(des) and 4.4 and 95.0 L kg-1 for Kd(des). The edaphic characteristics with the highest influence on adsorption were the silt fraction content and the exchangeable Ca content, while in the case of desorption, they were the total nitrogen, organic carbon, and exchangeable Ca and Mg contents. Regarding the pH, within the range studied (between 3 and 10), its value did not decisively affect the adsorption/desorption process. Overall, the set of these results could be of help to program appropriate measures leading to the retention/elimination of this antibiotic when it reaches the environment as a pollutant.

Variation of Hg concentration and accumulation in the soil of maritime pine plantations along a coast-inland transect in SW Europe.

Climatic conditions have been shown as a major driver of the fate of Hg in forest ecosystems at a global scale, but less is known about climatic effects at shorter scales. This study assesses whether the concentration and pools of Hg in soils collected from seventeen Pinus pinaster stands describing a coastal-inland transect in SW Europe vary along a regional climatic gradient. In each stand, samples of the organic subhorizons (OL, OF + OH) and the mineral soil (up to 40 cm) were collected and some general physico-chemical properties and total Hg (THg) were analyzed. Total Hg was significantly higher in the OF + OH than in the OL subhorizons (98 and 38 µg kg-1, respectively), favored by a greater organic matter humification in the former. In the mineral soil, mean THg values decreased with depth, ranging from 96 µg kg-1 in the 0-5 cm layers to 54 µg kg-1 in the deepest layers (30-40 cm), respectively. The average Hg pool (PHg) was 0.30 mg m-2 in the organic horizons (92% accumulated in the OF + OH subhorizons), and 27.4 mg m-2 in the mineral soil. Changes in climatic factors, mainly precipitation, along the coast-inland transect resulted in a remarkable variation of THg in the OL subhorizons, consistent with their role as the first receiver of atmospheric Hg inputs. The high precipitation rate and the occurrence of fogs in coastal areas characterized by the oceanic influence would explain the higher THg found in the uppermost soil layers of pine stands located close to the coastline. The regional climate is key to the fate of mercury in forest ecosystems by influencing the plant growth and subsequent atmospheric Hg uptake, the atmospheric Hg transference to the soil surface (wet and dry deposition and litterfall) and the dynamics that determine net Hg accumulation in the forest floor.

Direct toxicity of six antibiotics on soil bacterial communities affected by the addition of bio-adsorbents.

Reducing the toxicity caused by antibiotics on bacterial communities in the soil is one of the great challenges of this century. For this, the effectiveness of amending the soil with different bioadsorbents such as crushed mussel shell (CMS), pine bark (PB) and biomass ash (BA), as well as combinations of them (CMS + PB and PB + BA) was studied at different doses (0 g kg-1 to 48 g kg-1). Soil samples were spiked, separately, with increasing doses (0-2000 mg kg-1) of cefuroxime (CMX), amoxicillin (AMX), clarithromycin (CLA), azithromycin (AZI), ciprofloxacin (CIP) and trimethoprim (TMP). Their toxicity on bacterial growth was estimated using the tritium-labeled leucine (3H) incorporation method. Toxicity was observed to behave differently depending on the antibiotic family and bioadsorbent, although in different magnitude and at different doses. The toxicity of ß-lactams (AMX and CXM) was reduced by up to 54% when the highest doses of bio-adsorbents were added due to the increase in pH (CMS and BA) and carbon (PB) contribution. Macrolides (CLA and AZI) showed slight toxicity in un-amended soil samples, which increased by up to 65% with the addition of the bio-adsorbents. The toxicity of CIP (a fluoroquinolone) increased with the dose of the bio-adsorbents, reaching up to 20% compared with the control. Finally, the toxicity of TMP (a diaminopyrimidine) slightly increased with the dose of bio-adsorbents. The by-products that increase soil pH are those that showed the highest increases of CLA, AZI, CIP and TMP toxicities. These results could help to prevent/reduce environmental pollution caused by different kinds of antibiotics, selecting the most appropriated bio-adsorbents and doses.

Needle age and precipitation as drivers of Hg accumulation and deposition in coniferous forests from a southwestern European Atlantic region.

Vegetation and climate are critical in the biogeochemical cycle of Hg in forest ecosystems. The study assesses the influence of needle age and precipitation on the accumulation of Hg in needle biomass and its deposition by litterfall in thirty-one pine plantations spread throughout two biogeographical regions in SW Europe. Well-developed branches of Pinus pinaster were sampled and pine needles were classified according to 4 age classes (y0, y1, y2, y3). The concentration of total Hg (THg) was analyzed in the samples and Hg content in needle biomass and its deposition by litterfall were estimated. The concentration of total Hg (THg) increased with needle age ranging from 9.1 to 32.7 µg Hg kg-1 in the youngest and oldest needles, respectively. The rate of Hg uptake (HgR) three years after needle sprouting was 10.2 ± 2.3 µg Hg kg-1 yr-1, but it decreased with needle age probably due to a diminution in photosynthetic activity as needles get older. The average total Hg stored in needle biomass (HgWt) ranged from 5.6 to 87.8 mg Hg ha-1, with intermediate needle age classes (y1 and y2) accounting for 70% of the total Hg stored in the whole needle biomass. The average deposition flux of Hg through needle litterfall (HgLt) was 1.5 µg Hg m-2 yr-1, with the y2 and y3 needles contributing most to the total Hg flux. The spatial variation of THg, HgWt and HgLt decreased from coastal pine stands, characterized by an oceanic climate, to inland pine stands, a feature closely related to the dominant precipitation regime in the study area. Climatic conditions and needle age are the main factors affecting Hg accumulation in tree foliage, and should be considered for an accurate assessment of forest Hg pools at a regional scale and their potential consequences in the functioning of terrestrial ecosystems.

Influence of pH on the adsorption-desorption of doxycycline, enrofloxacin, and sulfamethoxypyridazine in soils with variable surface charge.

In this research, the adsorption/desorption of the antibiotics doxycycline (DC), enrofloxacin (ENR), and sulfamethoxypyradazine (SMP) was studied in 6 agricultural soils with predominance of variable charge, both before and after removing organic matter by calcination. DC adsorption was high at acidic pH, and decreased at pH values above 8. Removal of organic matter with calcination caused just a slight decrease in adsorption, and even in some soils adsorption was similar to that in non-calcined samples. The adsorption coefficients (Kd) were higher for the DC- species compared to DC+, DC0 and DC2-. Regarding DC desorption, the values were very low throughout the pH range covered in the study (2-12), both in the calcined samples and in those not subjected to calcination. ENR showed a similar behavior to DC regarding the effect of pH, since ENR adsorption also decreased at basic pH, but the effect of removing organic matter was different, as it caused a clear decrease in ENR adsorption. The species with the highest Kd was in this case ENR0, although ENR+ is also quantitatively important as regards Kd value in calcined samples. For this antibiotic, no differences in desorption were observed between calcined and non-calcined samples. Finally, SMP adsorption also decreased as pH increased, and, in addition, similarly to what happened with ENR, in general, there was a strong decrease in SMP adsorption when organic matter was removed. The species with the highest Kd in this case was SMP+ in non-calcined samples, but SMP0 and SMP- become more relevant in calcined samples. The percentages of SMP desorption were higher than those for the other two antibiotics, and an increase occurs at intermediate pH values, being higher for calcined samples. These results can be considered relevant in terms of increasing the knowledge as regards the possible evolution and fate of the three antibiotics studied. Specifically, for different pH conditions and with different organic matter contents, when they reach soils and other environmental compartments after being discharged as contaminants. This could have important repercussions on public health and the overall environment.

Cu and As(V) Adsorption and Desorption on/from Different Soils and Bio-Adsorbents.

This research is concerned with the adsorption and desorption of Cu and As(V) on/from different soils and by-products. Both contaminants may reach soils by the spreading of manure/slurries, wastewater, sewage sludge, or pesticides, and also due to pollution caused by mining and industrial activities. Different crop soils were sampled in A Limia (AL) and Sarria (S) (Galicia, NW Spain). Three low-cost by-products were selected to evaluate their bio-adsorbent potential: pine bark, oak ash, and mussel shell. The adsorption/desorption studies were carried out by means of batch-type experiments, adding increasing and individual concentrations of Cu and As(V). The fit of the adsorption data to the Langmuir, Freundlich, and Temkin models was assessed, with good results in some cases, but with high estimation errors in others. Cu retention was higher in soils with high organic matter and/or pH, reaching almost 100%, while the desorption was less than 15%. The As(V) adsorption percentage clearly decreased for higher As doses, especially in S soils, from 60−100% to 10−40%. The As(V) desorption was closely related to soil acidity, being higher for soils with higher pH values (S soils), in which up to 66% of the As(V) previously adsorbed can be desorbed. The three by-products showed high Cu adsorption, especially oak ash, which adsorbed all the Cu added in a rather irreversible manner. Oak ash also adsorbed a high amount of As(V) (>80%) in a rather non-reversible way, while mussel shell adsorbed between 7 and 33% of the added As(V), and pine bark adsorbed less than 12%, with both by-products reaching 35% desorption. Based on the adsorption and desorption data, oak ash performed as an excellent adsorbent for both Cu and As(V), a fact favored by its high pH and the presence of non-crystalline minerals and different oxides and carbonates. Overall, the results of this research can be relevant when designing strategies to prevent Cu and As(V) pollution affecting soils, waterbodies, and plants, and therefore have repercussions on public health and the environment.

Effects of ciprofloxacin, trimethoprim, and amoxicillin on microbial structure and growth as emerging pollutants reaching crop soils.

The presence of emerging pollutants, and specifically antibiotics, in agricultural soils has increased notably in recent decades, causing growing concern as regards potential environmental and health issues. With this in mind, the current study focuses on evaluating the toxicity exerted by three antibiotics (amoxicillin, trimethoprim, and ciprofloxacin) on the growth of soil bacterial communities, when these pollutants are present at different doses, and considered in the short, medium, and long terms (1, 8 and 42 days of incubation). Specifically, the research was carried out in 12 agricultural soils having different physicochemical characteristics and was performed by means of the leucine (3H) incorporation method. In addition, changes in the structure of soil microbial communities at 8 and 42 days were studied in four of these soils, using the phospholipids of fatty acids method for this. The main results indicate that the most toxic antibiotic was amoxicillin, followed by trimethoprim and ciprofloxacin. The results also show that the toxicity of amoxicillin decreases with time, with values of Log IC50 ranging from 0.07 ± 0.05 to 3.43 ± 0.08 for day 1, from 0.95 ± 0.07 to 3.97 ± 0.15 for day 8, and from 2.05 ± 0.03 to 3.18 ± 0.04 for day 42, during the incubation period. Regarding trimethoprim, 3 different behaviors were observed: for some soils the growth of soil bacterial communities was not affected, for a second group of soils trimethoprim toxicity showed dose-response effects that remained persistent over time, and, finally, for a third group of soils the toxicity of trimethoprim increased over time, being greater for longer incubation times (42 days). As regards ciprofloxacin, this antibiotic did not show a toxicity effect on the growth of soil bacterial communities for any of the soils or incubation times studied. Furthermore, the principal component analysis performed with the phospholipids of fatty acids results demonstrated that the microbial community structure of these agricultural soils, which persisted after 42 days of incubation, depended mainly on soil characteristics and, to a lesser extent, on the dose and type of antibiotic (amoxicillin, trimethoprim or ciprofloxacin). In addition, it was found that, in this research, the application of the three antibiotics to soils usually favored the presence of fungi and Gram-positive bacteria.

Ciprofloxacin and Trimethoprim Adsorption/Desorption in Agricultural Soils.

The current research focuses on the adsorption/desorption characteristics of the antibiotics ciprofloxacin (CIP) and trimethoprim (TRI) taking place in 17 agricultural soils, which are studied by means of batch-type experiments. The results show that adsorption was higher for CIP, with Freundlich KF values ranging between 1150 and 5086 Ln µmol1-n kg-1, while they were between 29 and 110 Ln µmol1-n kg-1 in the case of TRI. Other parameters, such as the Langmuir maximum adsorption capacity (qm(ads)), as well as the Kd parameter in the linear model and also the adsorption percentages, follow the same trend as KF. Desorption was lower for CIP (with KF(des) values in the range 1089-6234 Ln µmol1-n kg-1) than for TRI (with KF(des) ranging between 26 and 138 Ln µmol1-n kg-1). The higher irreversibility of CIP adsorption was also confirmed by its lower nF(des)/nF(ads) ratios, compared to TRI. Regarding soil characteristics, it was evidenced that nitrogen and carbon contents, as well as mineral fractions, had the highest influence on the adsorption/desorption process. These results can be considered relevant as regards the fate of both antibiotics when they reach the environment as pollutants and therefore could be considered in assessment procedures focused on environmental and public health aspects.

Potential of low-cost bio-adsorbents to retain amoxicillin in contaminated water.

Sewage sludge as agricultural amendment is the main route of human-medicine antibiotics to enter soils. When reaching environmental compartments, these compounds can cause significant risks to human and ecological health. Specifically, the antibiotic amoxicillin (AMX) is highly used in medicine, and the fact that more than 80% of the total ingested is excreted increases the chances of causing serious environmental and public health problems. As the use of low-cost bio-adsorbents could help to solve these issues, this research focuses on the retention of AMX onto four by-products of the forestry industry (eucalyptus leaf, pine bark, pine needles, and wood ash) and one from food industry (mussel shell). To carry out this study, batch-type tests were performed, where increasing concentrations of the antibiotic (0, 2.5, 5, 10, 20, 30, 40 and 50 µmol L-1) were added to samples of 0.5 g of each bio-adsorbent. Eucalyptus leaf, pine needle and wood ash showed adsorption scores higher than 80%, while it was up to 39% and 48% for pine bark and mussel shell, respectively. For pine bark, wood ash and mussel shell, adsorption data showed good adjustment to the Freundlich and Linear models, while pine needles and eucalyptus leaf did not fit to any model. There was not desorption when the maximum concentration of AMX (50 µmol L-1) was added. Overall, eucalyptus leaf, pine needles and wood ash can be considered good bio-adsorbents with high potential to retain AMX, which has significant implications regarding their eventual use to reduce risks of environmental pollution by this antibiotic.

Competitive adsorption and desorption of tetracycline and sulfadiazine in crop soils.

In view of the environmental issues caused by antibiotics, this research studies competitive adsorption/desorption for tetracycline (TC) and sulfadiazine (SDZ) in agricultural soils. Competitive adsorption was studied in binary systems (adding equal concentrations of both antibiotics). In addition, it was compared with results from simple systems. In all cases, batch-type adsorption/desorption experiments were carried out. In the binary systems, for the highest antibiotic concentration added, adsorption percentages were always higher for TC (close to 100%) than for SDZ (10-90%). In these systems, TC desorption was lower than 5% for all soils, and generally <10% for SDZ. Comparing TC and SDZ adsorption for the different systems, SDZ was clearly affected by the presence of TC, with SDZ adsorption percentages being was much higher (with differences generally above 65%) in the binary than in the simple systems. On the contrary, comparing the results of TC adsorption in simple and binary systems, TC was not affected by the presence of SDZ, obtaining similar adsorption percentages in both systems. Kd and KF values (in the Linear and Freundlich models), were higher in the simple systems in the case of TC, which could be due to competition with SDZ, while for SDZ Kd and KF were higher in the binary systems, with a synergistic effect of TC favoring SDZ adsorption. Regarding desorption, it reached 100% for SDZ in some soils in simple systems, dropping to 10% in the presence of TC. TC desorption was <4%, not affected by SDZ. The results indicate that environmental risks would be higher for SDZ, showing differences when both antibiotics are present. This can be considered relevant as regards public health and environmental preservation, in view of direct toxicities and the promotion of resistance to antibiotics associated with the presence of these contaminants in the environment.

Amoxicillin Retention/Release in Agricultural Soils Amended with Different Bio-Adsorbent Materials.

The antibiotic amoxicillin (AMX) may reach soils and other environmental compartments as a pollutant, with potential to affect human and environmental health. To solve/minimize these hazards, it would be clearly interesting to develop effective and low-cost methods allowing the retention/removal of this compound. With these aspects in mind, this work focuses on studying the adsorption/desorption of AMX in different agricultural soils, with and without the amendment of three bio-adsorbents, specifically, pine bark, wood ash and mussel shell. For performing the research, batch-type experiments were carried out, adding increasing concentrations of the antibiotic to soil samples with and without the amendment of these three bio-adsorbents. The results showed that the amendments increased AMX adsorption, with pine bark being the most effective. Among the adsorption models that were tested, the Freundlich equation was the one showing the best fit to the empirical adsorption results. Regarding the desorption values, there was a decrease affecting the soils to which the bio-adsorbents were added, with overall desorption not exceeding 6% in any case. In general, the results indicate that the bio-adsorbents under study contributed to retaining AMX in the soils in which they were applied, and therefore reduced the risk of contamination by this antibiotic, which can be considered useful and relevant to protect environmental quality and public health.

Relevance of sorption in bio-reduction of amoxicillin taking place in forest and crop soils.

The fate of antibiotics reaching soils is a matter of concern, given its potential repercussions on public health and the environment. In this work, the potential bio-reduction of the antibiotic amoxicillin (AMX), affected by sorption and desorption, is studied for 17 soils with clearly different characteristics. To carry out these studies, batch-type tests were performed, adding increasing concentrations of AMX (0, 2.5, 5, 10, 20, 30, 40, and 50 µmol L-1) to the soils. For the highest concentration added (50 µmol L-1), the adsorption values for forest soils ranged from 90.97 to 102.54 µmol kg-1 (74.21-82.41% of the amounts of antibiotic added), while the range was 69.96-94.87 µmol kg-1 (68.31-92.56%) for maize soils, and 52.72-85.40 µmol kg-1 (50.96-82.55%) for vineyard soils. When comparing the results for all soils, the highest adsorption corresponded to those more acidic and with high organic matter and non-crystalline minerals contents. The best adjustment to adsorption models corresponded to Freundlich's. AMX desorption was generally <10%; specifically, the maximum was 6.5% in forest soils, and 16.9% in agricultural soils. These results can be considered relevant since they cover agricultural and forest soils with a wide range of pH and organic matter contents, for an antibiotic that, reaching the environment as a contaminant, can pose a potential danger to human and environmental health.

Time-course evolution of bacterial community tolerance to tetracycline antibiotics in agricultural soils: A laboratory experiment.

The presence of antibiotics in soils may increase the selection pressure on soil bacterial communities and cause tolerance to these pollutants. The temporal evolution of bacterial community tolerance to different concentrations of tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) was evaluated in two soils. The results showed an increase of soil bacterial community tolerance to TC, CTC and OTC only in samples polluted with the highest antibiotic concentrations tested (2000 mg kg-1). The magnitude of those increases was higher in the soil with the lower organic carbon content (1.6%) than in the soil with an organic carbon content reaching 3.4%. In the soil with low organic carbon content, the time-course evolution showed a maximum increase in the tolerance of bacterial communities to tetracycline antibiotics between 45 and 100 incubation days, while for longer incubation times (360 days) the tolerance decreased. In the soil with high organic carbon content, a similar behavior was found for OTC. However, for CTC and TC, slightly increases and decreases (respectively) were found in the bacterial community tolerance at intermediate incubation times, followed by values close to zero for TC after 360 days of incubation, while for CTC they remained higher than in the control. In conclusion, soil pollution due to tetracyclines may cause bacterial community tolerance to these antibiotics when present at high concentrations. In addition, the risk is higher in soils with low organic matter content, and it decreases with time.

Photodegradation of Ciprofloxacin, Clarithromycin and Trimethoprim: Influence of pH and Humic Acids.

In view of the rising relevance of emerging pollutants in the environment, this work studies the photodegradation of three antibiotics, evaluating the effects of the pH of the medium and the concentration of dissolved organic matter. Simulated light (with a spectrum similar to that of natural sunlight) was applied to the antibiotics Ciprofloxacin (Cip), Clarithromycin (Cla) and Trimethoprim (Tri), at three different pH, and in the presence of different concentrations of humic acids. The sensitivity to light followed the sequence: Cip > Cla > Tri, which was inverse for the half-life (Tri > Cla > Cip). As the pH increased, the half-life generally decreased, except for Cla. Regarding the kinetic constant k, in the case of Cip and Tri it increased with the rise of pH, while decreased for Cla. The results corresponding to total organic carbon (TOC) indicate that the complete mineralization of the antibiotics was not achieved. The effect of humic acids was not marked, slightly increasing the degradation of Cip, and slightly decreasing it for Tri, while no effect was detected for Cla. These results may be relevant in terms of understanding the evolution of these antibiotics, especially when they reach different environmental compartments and receive sunlight radiation.

SARS-CoV-2 and other main pathogenic microorganisms in the environment: Situation in Galicia and Spain.

In the context of the current COVID-19 pandemic, and mostly taking a broad perspective, it is clearly relevant to study environmental factors that could affect eventual future outbreaks due to coronaviruses and/or other pathogenic microorganisms. In view of that, the authors of this manuscript review the situation of SARS-CoV-2 and other main pathogenic microorganisms in the environment, focusing on Galicia and Spain. Overall, in addition to showing local data, it is put in evidence that, summed to all efforts being carried out to treat/control this and any other eventual future epidemic diseases, both at local and global levels, a deep attention should be paid to ecological/environmental aspects that have effects on the planet, its ecosystems and their relations/associations with the probability of spreading of eventual future pandemics.