The role of land use, management, and microbial diversity depletion on glyphosate biodegradation in tropical soils.

Land use and management changes affect the composition and diversity of soil bacteria and fungi, which in turn may alter soil health and the provision of key ecological functions, such as pesticide degradation and soil detoxification. However, the extent to which these changes affect such services is still poorly understood in tropical agroecosystems. Our main goal was to evaluate how land-use (tilled versus no-tilled soil), soil management (N-fertilization), and microbial diversity depletion [tenfold (D1 = 10-1) and thousandfold (D3 = 10-3) dilutions] impacted soil enzyme activities (ß-glycosidase and acid phosphatase) involved in nutrient cycles and glyphosate mineralization. Soils were collected from a long-term experimental area (35 years) and compared to its native forest soil (NF). Glyphosate was selected due to its intensive use in agriculture worldwide and in the study area, as well as its recalcitrance in the environment by forming inner sphere complexes. Bacterial communities played a more important role than the fungi in glyphosate degradation. For this function, the role of microbial diversity was more critical than land use and soil management. Our study also revealed that conservation tillage systems, such as no-tillage, regardless of nitrogen fertilizer use, mitigates the negative effects of microbial diversity depletion, being more efficient and resilient regarding glyphosate degradation than conventional tillage systems. No-tilled soils also presented much higher ß-glycosidase and acid phosphatase activities as well as higher bacterial diversity indexes than those under conventional tillage. Consequently, conservation tillage is a key component for sustaining soil health and its functionality, providing critical ecosystem functions, such as soil detoxification in tropical agroecosystems.

Physicochemical and bacterial changes during composting of vegetable and animal-derived agro-industrial wastes.

This study investigates the impact of different agro-industrial organic wastes (i.e., sugarcane filter cake, poultry litter, and chicken manure) on the bacterial community and their relationship with physicochemical attributes during composting. Integrative analysis was performed by combining high-throughput sequencing and environmental data to decipher changes in the waste microbiome. The results revealed that animal-derived compost stabilized more carbon and mineralized a more organic nitrogen than vegetable-derived compost. Composting enhanced bacterial diversity and turned the bacterial community structure similar among all wastes, reducing Firmicutes abundance in animal-derived wastes. Potential biomarkers indicating compost maturation were Proteobacteria and Bacteroidota phyla, Chryseolinea genus and Rhizobiales order. The waste source influenced the final physicochemical attributes, whereas composting enhanced the complexity of the microbial community in the order of poultry litter > filter cake > chicken manure. Therefore, composted wastes, mainly the animal-derived ones, seem to present more sustainable attributes for agricultural use, despite their losses of C, N, and S.

Land use and roles of soil bacterial community in the dissipation of atrazine.

Atrazine (ATZ) is one of the most widely used herbicides in the world even though it is classified as a carcinogenic endocrine disruptor. This study focused on how land use (grazing versus cultivation in parallel soils, the latter under no-till with a seven-year history of ATZ application) and bacterial community diversity affected ATZ dissipation. Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria, Acidobacteria, Verrucomicrobia, Planctomycetes, and Gemmatimonadetes were the dominant phyla in both soils. The mineralization of ATZ was much higher in soils under cultivation up to the onset of moderate diversity depletion (dilution =10-3), corresponding to 44-52% of the amount applied (< 5% in the grazed soil). This was attributed to the higher diversity and complexity of the soils´ bacterial communities which consist of microbial groups that were more adapted as a result of previous exposure to ATZ. In these cases, ATZ dissipation was attributed mainly to mineralization (DT50 = 4-11 d). However, formation of non-extractable ATZ residues was exceptionally important in the other cases (DT50 = 17-44 d). The cultivated soils also presented a higher number of bacterial genera correlated with ATZ dissipation, in which Acidothermus, Aquicela, Arenimonas, Candidatus_Koribacter, Hirschia, MND1, Nitrospira, Occallatibacter, OM27_clade, and Ralstonia are suggested as potential ATZ-degraders. Finally, ATZ dissipation was mostly associated with an abundance of microbial functions related to energy supply and N-metabolism, suggesting co-metabolism is its first biodegradation step.

Accessing biochar's porosity using a new low field NMR approach and its impacts on the retention of highly mobile herbicides.

Agrowaste biochars [sugarcane straw (SS), rice husk (RH), poultry manure (PM), and sawdust (SW)] were synthesized at different pyrolysis temperatures (350, 450, 550, and 650 °C) to evaluate their potential to retain highly mobile herbicides, such as hexazinone and tebuthiuron that often contaminate water resources around sugarcane plantations. A new low field nuclear magnetic resonance approach based on decay due to diffusion in internal magnetic field (NMR-DDIF) was successfully used to determine biochar's porosity and specific surface area (SSA) to clear the findings of this work. SSA of pores with diameters >5.0 µm increased with pyrolysis temperatures and seemed to dictate biochar's retention, which was >70% of the applied amounts at 650 °C. These macropores appear to act as main arteries for herbicide intra-particle diffusion into smaller pores, thus enhancing herbicides retention. Biochar granulometry had little, but herbicide aging had a significant effect on sorption, mainly of tebuthiuron. However, soils amended with 10,000 kg ha-1 of the biochars showed low sorption potential. Therefore, higher than usual biochar rates or proper incorporation strategies, i.e., surface incorporation, will be needed to remediate areas contaminated with these highly mobile herbicides, thus precluding their leaching to groundwaters.

Using 14C-glyphosate to investigate the distribution of two formulations in transgenic glyphosate-resistant soybean.

Glyphosate residues in grain can be explained by the concentrations and formulations of glyphosate products. This study aimed to evaluate the residues from glyphosate formulations labeled with 14C-glyphosate applied to leaves of glyphosate-resistant soybean (GRS) in two life cycles by liquid scintillation spectrometry. Different plant tissues were analyzed after the end of the plants' life cycles. The experimental design was four repetitions of three treatments: Roundup® Original, Roundup Ready®, and unformulated glyphosate (control). The application of the dosing solution was 120 µL on the first four trifoliate leaves (10 µL per leaflet) of each plant, deposited manually with a 1-µL dispenser. All treatment solutions were calculated at a 1.2 kg a.e ha-1 of glyphosate. Glyphosate formulations of Roundup® Original and Roundup Ready® increased 14C-glyphosate distribution in GRS compared to the unformulated herbicide, regardless of the experiment (first or second cycle). Overall, the percentages of total radioactivity applied (18.33 kBq) found in grains were less than 5%. Grains, stems, and leaves showed the highest levels of herbicide residues compared to other parts of the plant. Despite the Roundup Ready® formulation having increased residues, the highest value found in grains, 1.95 mg kg-1, was less than 10 mg kg-1, the maximum residue limit (MRL) in Brazil.

Sulfadiazine dissipation as a function of soil bacterial diversity.

Antibiotic residues in the environment are concerning since results in dispersion of resistance genes. Their degradation is often closely related to microbial metabolism. However, the impacts of soil bacterial community on sulfadiazine (SDZ) dissipation remains unclear, mainly in tropical soils. Our main goals were to evaluate effects of long-term swine manure application on soil bacterial structure as well as effects of soil microbial diversity depletion on SDZ dissipation, using "extinction dilution approach" and 14C-SDZ. Manure application affected several soil attributes, such as pH, organic carbon (OC), and macronutrient contents as well as bacterial community structure and diversity. Even minor bacterial diversity depletion impacted SDZ mineralization and non-extractible residue (NER) formation rates, but NER recovered along 42 d likely due to soil diversity recovery. However, this period may be enough to spread resistance genes into the environment. Surprisingly, the non-manured natural soil (NS-S1) showed faster SDZ dissipation rate (DT90 = 2.0 versus 21 d) and had a great number of bacterial families involved in major SDZ dissipation pathways (mineralization and mainly NER), such as Isosphaeraceae, Ktedonobacteraceae, Acidobacteriaceae_(Subgroup_1), Micromonosporaceae, and Sphingobacteriaceae. This result is unique and contrasts our hypothesis that long-term manured soils would present adaptive advantages and, consequently, have higher SDZ dissipation rates. The literature suggests instantaneous chemical degradation of SDZ in acidic soils responsible to the fast formation of NER. Our results show that if chemical degradation happens, it is soon followed by microbial metabolism (biodegradation) performed by a pool of bacteria and the newly formed metabolites should favors NER formation since SDZ presented low sorption. It also showed that SDZ mineralization is a low redundancy function.

Sulfadiazine dissipation in acidic tropical soils.

Sulfadiazine (SDZ) residues have been detected in manured soils as well as their adjacent water resources, but its behavior is still poorly understood in acidic tropical soils. This research aimed to evaluate sorption, leaching, and biodegradation of 14C-SDZ in four acidic soils from Brazil, using OECD guidelines. Except for the sand soil (Kd = 2.6 L kg-1), SDZ sorption tended to be higher (Kd > 8.4 L kg-1) and more hysteretic (ΔH >> 1) in acidic soils. When freshly applied, SDZ leaching was low (< 0.11% of applied radioactivity (AR)) and could not always be predicted by Kd values; but leaching was restricted when SDZ was aged for 62 days. SDZ mineralization was low (< 3%) but its dissipation was fast (DT50 < 2.3 days and DT90 < 6.3 days) due to fast initial degradation (an unknown metabolite was immediately formed, likely 4-hydroxysulfadiazine) and mainly to fast formation of non-extractable residues (NER) (> 78% of AR up to 7 days). For certain acidic soils, the abrupt breakdown of the SDZ suggests that degradation should be initially chemical and then followed by enzymatically driven reactions. The fast formation of NERs was attributed mostly to chemical bounding to soil humic substances (Type II-NER), but SDZ sequestration cannot be ruled out (Type I-NER). NERs represent a long-term environmental reservoir of SDZ that may cause deleterious effects on non-target organisms as well as promote antibiotic resistance to soil microbes.

Pesticides in the surface waters of the Camanducaia River watershed, Brazil.

Camanducaia River is part of the Piracicaba watershed responsible for pumping water into the Cantareira System, which is one of the main water sources for the metropolis of São Paulo and Campinas, Brazil. Intensive use of pesticides and hilly topography represents a situation of high risk for river water contamination. Therefore, water samples from 12 locations were collected along the Camanducaia River and its tributaries, over a period of 4 mo during the rainy season, and analyzed by GC-MS/MS or UPLC- MS/MS for the presence of 46 pesticides. Seven pesticides (fipronil, methyl parathion, metolachlor, atrazine, carbofuran, diuron, and simazine) were positively detected. Only atrazine (the most frequently detected) and diuron were present at concentrations above the limit of quantification of the analytical method (0.32 and 0.57 µg L-1 for atrazine and diuron, respectively). Pesticides detection frequency was higher than expected for a river system where only 11.8% of the land area is under agriculture. The vulnerability of the Camanducaia basin to pesticide contamination is attributed to the high annual precipitation (> 1.5 m y-1 in the headwaters), associated with topographical features (steep terrain) and soil types that favor surface runoff, which has been exacerbated by poor soil management practices.

Sewage Sludge Microbial Structures and Relations to Their Sources, Treatments, and Chemical Attributes.

Sewage sludges generation and their disposal have become one of the greatest challenges of the 21st century. They have great microbial diversity that may impact wastewater treatment plant (WWTP) efficiency and soil quality whether used as fertilizers. Therefore, this research aimed to characterize microbial community diversity and structure of 19 sewage sludges from São Paulo, Brazil, as well as to draw their relations to sludge sources [domestic and mixed (domestic+industrial)], biological treatments (redox conditions and liming), and chemical attributes, using molecular biology as a tool. All sludges revealed high bacterial diversity, but their sources and redox operating conditions as well as liming did not consistently affect bacterial community structures. Proteobacteria was the dominant phylum followed by Bacteroidetes and Firmicutes; whereas Clostridium was the dominant genus followed by Treponema, Propionibacterium, Syntrophus, and Desulfobulbus. The sludge samples could be clustered into six groups (C1 to C6) according their microbial structure similarities. Very high pH (≥11.9) was the main sludge attribute segregating C6, that presented very distinct microbial structure from the others. Its most dominant genera were Propionibacterium > > Comamonas > Brevundimonas > Methylobacterium ∼Stenotrophomonas ∼Cloacibacterium. The other clusters' dominant genera were Clostridium > > Treponema > Desulfobulbus ∼Syntrophus. Moreover, high Fe and S were important modulators of microbial structure in certain sludges undertaking anaerobic treatment and having relatively low N-Kj, B, and P contents (C5). However, high N-Kj, B, P, and low Fe and Al contents were typical of domestic, unlimed, and aerobically treated sludges (C1). In general, heavy metals had little impact on microbial community structure of the sludges. However, our sludges shared a common core of 77 bacteria, mostly Clostridium, Treponema, Syntrophus, and Comamonas. They should dictate microbial functioning within WWTPs, except by SS12 and SS13.

The depleted mineralization of the fungicide chlorothalonil derived from loss in soil microbial diversity.

There are lack of studies regarding the effects of microbial diversity on specific soil functions, such as pesticides degradation. This study evaluated the role of bacterial community diversity and biochar on chlorothalonil (CTN) degradation, using 'dilution to extinction' approach, PCR-DGGE/16S rRNA gene technique, and radiorespirometry (14C-CTN). Biochar and microbial community dilution affected structure of the microbial community. In spite of that, CTN mineralization was slow, but dissipation was very fast (D50 < 1.0 d) due to immediate chemical degradation and formation of non-extractable (bound) residues. However, any depletion on soil microbial diversity strongly affected CTN mineralization, suggesting that this function is related to less abundant but specific microbial groups (CTN degraders) or to soil microbial diversity. The extent of these effects will strongly depend on the compound nature (recalcitrance) and soil matrix/substrate (bioavailability). It can be corroborated by the fact that biochar affected CTN sorption, its bioavailability, and subsequently its mineralization rate in the NS. These data indicate a strong relationship between soil microbial diversity and pesticide degradation, which is an acting form to mitigate xenobiotics accumulation in the environment.

Fate of Tebuthiuron and Hexazinone in Green-Cane Harvesting System.

In Brazil, fire prior to sugar cane harvesting has to be phased out by 2017, but it has already been phased out in up to 85-90% of the cropped area. The new system is called green cane and has entirely changed weed management practices. The main goal of this study was to evaluate the effects of the straw presence as well as humic acid (HA), formulation, soil type, and aging on the sorption and leaching of (14)C-tebuthiuron and hexazinone. Both herbicides presented low sorption for all treatments (Kd,app ≤ 3.25 L kg(-1)), but it was higher for tebuthiuron in the clayer soil (LVd). Straw and aging only slightly enhanced sorption. The HA effects were not clear. Sorption was mostly affected by herbicide and soil type. Straw may promote physical trapping (∼40% of applied amount), which cannot be accessed by "batch" sorption (∼15% of the applied amount is sorbed), attenuating leaching of highly mobile herbicides in green-cane systems. To properly assess leaching through straw residues under laboratory condition, rainfall distribution is very important.

Sorption of fluoroquinolones and sulfonamides in 13 Brazilian soils.

Animal production is a leading economic activity in Brazil and antibiotics are widely used. However, the occurrence, behavior, and impacts of antibiotics in Brazilian soils are still poorly known. We evaluated the sorption behavior of four fluoroquinolones (norfloxacin, ciprofloxacin, danofloxacin, and enrofloxacin) and five sulfonamides (sulfadiazine, sulfachloropyridazine, sulfamethoxazole, sulfadimidine, and sulfathiazole) in 13 Brazilian soils with contrasting physical, chemical, and mineralogical properties. Fluoroquinolone sorption was very high (Kd≥544 L kg(-1)) whereas sulfonamide sorption ranged from low to high (Kd=0.7-70.1 L kg(-1)), consistent with previous reports in the literature. Soil texture and cation exchange capacity were the soil attributes that most affected sorption. Cation exchange was the most important sorption mechanism for the fluoroquinolones in highly weathered tropical soils, although cation bridging and ion pairing could not be ruled out. Hydrophobic partition played an important role in the sorption of the sulfonamides, but sorption was also affected by non-hydrophobic interactions with organic and/or mineral surfaces. Sorption for both compound classes tended to be higher in soils with high Al and Fe oxihydroxide contents, but they were not correlated with Kd values. No direct effect of soil pH was seen. The fluoroquinolones are not expected to leach even in worst-case scenarios (soils rich in sand and poor in organic carbon), whereas soil attributes dictate leaching potential for the sulfonamides.

Occurrence and sorption of fluoroquinolones in poultry litters and soils from São Paulo State, Brazil.

Animal production is one of the most expressive sectors of Brazilian agro-economy. Although antibiotics are routinely used in this activity, their occurrence, fate, and potential impacts to the local environment are largely unknown. This research evaluated sorption-desorption and occurrence of four commonly used fluoroquinolones (norfloxacin, ciprofloxacin, danofloxacin, and enrofloxacin) in poultry litter and soil samples from São Paulo State, Brazil. The sorption-desorption studies involved batch equilibration technique and followed the OECD guideline for pesticides. All compounds were analyzed by HPLC, using fluorescence detector. Fluoroquinolones' sorption potential to the poultry litters (K(d) ≤65 L kg(-1)) was lower than to the soil (K(d) ~40,000 L kg(-1)), but was always high (≥69% of applied amount) indicating a higher specificity of fluoroquinolones interaction with soils. The addition of poultry litter (5%) to the soil had not affected sorption or desorption of these compounds. Desorption was negligible in the soil (≤0.5% of sorbed amount), but not in the poultry litters (up to 42% of sorbed amount). Fluoroquinolones' mean concentrations found in the poultry litters (1.37 to 6.68 mg kg(-1)) and soils (22.93 µg kg(-1)) were compatible to those found elsewhere (Austria, China, and Turkey). Enrofloxacin was the most often detected compound (30% of poultry litters and 27% of soils) at the highest mean concentrations (6.68 mg kg(-1) for poultry litters and 22.93 µg kg(-1) for soils). These results show that antibiotics are routinely used in poultry production and might represent one potential source of pollution to the environment that has been largely ignored and should be further investigated in Brazil.

Remobilização de resíduos ligados de 14C-atrazina em ácidos fúlvicos / Remobilization of 14C-atrazine bound residues in fulvic acids

Objetivou-se avaliar em condições de laboratório a remobilização dos resíduos ligados de 14C-atrazina em ácidos fúlvicos em dois solos do Estado de São Paulo. Incubaram-se 100g dos solos Latossolo Vermelho Escuro (LE) e Glei Húmico (GH) durante 49 dias, com os tratamentos: testemunha, palha de milho (1,5g) e glicose + peptona (0,2g) em potes tipo compota, com dose radioativa de 28,033 KBq (100 por cento). Utilizaram-se 10mL de NaOH 0,2 moles L-1 para captura do 14CO2 desprendido. A dessorção foi feita com CaCl2, a extração com acetonitrila: água (8:2) e o fracionamento da matéria orgânica foi baseado nas solubilidades em ácidos e bases das substâncias húmicas. Os extratos obtidos foram analisados quanto à radioatividade e valores de Razão de Frente. Os dois solos apresentaram uma baixa mineralização dos resíduos ligados de 14C-atrazina em ácidos fúlvicos. A remobilização para os ácidos húmicos e humina foi pequena, principalmene no GH. A adição dos tratamentos não influencia a mineralização nem a disponibilidade dos resíduos ligados de 14C-atrazina em ácidos fúlvicos. A atrazina foi completamente degradada à hidroxiatrazina e desetilatrazina.