Occurrence and dissipation mechanism of organic pollutants during the composting of sewage sludge: A critical review

Sewage sludge contains various classes of organic pollutants, limiting its land application. Sludge composting can effectively remove some organic pollutants. This review summarizesrecent researches on concentration changes and dissipation of different organic pollutants including persistent organic pollutants during sludge composting, and discusses their dissipation pathways and the current understanding on dissipation mechanism. Some organic pollutants like PAHs and phthalates were removed mainly through biodegradation or mineralization, and their dissipation percentages were higher than those of PCDD/Fs and PCBs. Nevertheless, some recalcitrant organic pollutants could be sequestrated in organic fractions of sludge mixtures, and their levels and ARG abundance even increased after sludge composting in some studies, posing potential risks for land application. This review demonstrated that microbial community and their corresponding degradation for organic pollutants were influenced by different pollutants, bulking agents, composting methods and processes. Further research perspectives on removing organic pollutants during sludge composting were highlighted.

Residue behavior and dietary risk assessment of six pesticides in pak choi using QuEChERS method coupled with UPLC-MS/MS

A reliable and simple modified QuEChERS method with UPLC-MS/MS was developed for the simultaneous determination of six pesticides (dimethomorph, imidaclothiz, lufenuron, methoxyfenozide, pyridaben, spinetoram) and their metabolites in pak choi. Method validation indicated good linearity (R² ≥ 0.99), accuracy (recoveries of 75%-112%), sensitivity (limits of quantification, 0.002-0.01 mg kg^-1), and precision (relative standard deviations ≤ 21%), and matrix effects were -36-28%. The half-lives of the six pesticides in pak choi were 2.2-12 d under open field and greenhouse conditions. Considering the short growth cycle of pak choi, the terminal residue levels (0.046-7.8 mg kg^-1) and the relevant maximum residue limits (MRLs) of some countries, 5 d was recommended as the pre-harvest interval for the six pesticides on pak choi. Dietary risk assessment revealed that the risk quotients were 3.1%-58% for different gender and age groups in China, indicating none unacceptable public health risk for general population. The results showed that all the six pesticides degraded faster and the terminal residues were much lower under open field conditions than those under greenhouse conditions, which was mainly due to the influence of rainfall, sunlight and other environmental factors. This work was thus significant in assessing the dissipation fate and food safety risks of the six pesticides on pak choi and facilitated the establishment of maximum residue limits.

Persistence, dissipation behavior and dietary risk assessment of a combi-product of chlorantraniliprole and λ-cyhalothrin in/on pigeonpea (Cajanus cajan L.)

Pigeonpea (Cajanus cajan L.) is an annually cultivated food and forage crop, attacked by a large number of pests mainly pod borer (Helicoverpa armigera). For the control of this insect pest, a combination of broad-spectrum insecticides viz., chlorantraniliprole and λ-cyhalothrin have been in use to reduce the pod damage and increase crop production worldwide. Therefore, a field trial was conducted to study dissipation and persistence behavior of insecticides combination (Chlorantraniliprole 9.26 % + λ-cyhalothrin 4.63 % ZC) in/on pigeonpea at the recommended dose (RD) 30 g a.i./ha and double recommended dose 60 g a.i./ha (2RD). The quantitative analysis was performed using ultra-high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) for chlorantraniliprole and Gas chromatography with electron captured detector (GC-ECD) for λ-cyhalothrin. The Quick, Easy, Cheap, Effective, Rugged and Safe (QuEChERS) method was validated for its accuracy, precision and sensitivity. The chlorantraniliprole persisted upto 30 days and λ-cyhalothrin persisted upto 10 days at RD and 20 days at 2RD. The half-lives (DT₅₀) of chlorantraniliprole and λ-cyhalothrin were from 4.95 to 5.78 days and 2.48–4.33 days at recommended and double recommended dose in pigeonpea, respectively. However, residues of both insecticides measured from soil at 30^th day and harvest time were below the limit of quantification (LOQ). The waiting period deciphered for chlorantraniliprole and λ-cyhalothrin applied as combi-product was 9 days at recommended dose. Dietary risk assessment (Risk quotient<1) was performed on the basis of field trial suggested the application of chlorantraniliprole and λ-cyhalothrin as combi-product at recommended dose is safe for the consumers.

Dissipation behavior, residue dynamics, and dietary risk assessment of forchlorfenuron in postharvest kiwifruits during simulated cold chain logistics and store shelf life

Forchlorfenuron (CPPU) is often applied during the cultivation of kiwifruit to produce larger fruit. To address degradation patterns of CPPU during simulated cold chain logistics and simulated shelf life of the fruit after harvest, appropriate storage methods and safe consumption behavior can be investigated. In this study, an ultra-high-performance liquid chromatography-tandem mass spectrometry method was adopted to detect CPPU residues under different conditions. CPPU in kiwifruit stored at 6 °C had a half-life of 40.8-77.0 days. However, when kiwifruit was stored at 0 °C under simulated cold chain storage conditions, the half-life of CPPU was 63.0-115.5 days, implying that lower storage temperatures can reduce the degradation rate of CPPU. The residues of CPPU in kiwifruit pulp declined with time, and the reduction followed the first-order kinetics equation. More CPPU residues were present in the pulp of postharvest kiwifruit treated with exogenous ethylene than in the pulp of untreated kiwifruit. Thus, using exogenous ethylene for artificial ripening after harvest is not recommended. We determined that the appropriate cold chain storage temperature is 6 °C. It is recommended that the public select kiwifruit stored for at least 2 weeks. The estimated chronic and acute dietary risk quotients of CPPU are ≤ 0.79% and ≤ 0.11%, respectively. Therefore, it is highly unlikely that consumers will be poisoned by CPPU due to kiwifruit consumption. Our results provide scientific evidence regarding the adoption of appropriate kiwifruit storage methods and consumption behavior to enhance consumption safety.

Harnessing fluctuation theorems to discover free energy and dissipation potentials from non-equilibrium data

The Jarzynski relation, as an equality form of the second law of thermodynamics, represents an exact thermodynamic statement that is valid arbitrarily far away from equilibrium. This remarkable relation directly links the equilibrium free energy difference between two states and the probability distribution of the work done along a process that drives the system from one state to the other. Here, we leverage the Jarzynski equality and a local equilibrium assumption, to go beyond the calculation of free energy differences and also extract the dissipation potential from additional measurements of kinematic field variables (strain and velocity fields). The proposed strategy is exemplified over pulling experiments of mass-spring models obeying overdamped Langevin dynamics, which is a prototype for nanorods, fibrous macro-molecules and the Rouse model of polymers. Different interaction potentials, fluid viscosities and bath temperatures are studied, so as to intrinsically control how close or far away the system is from equilibrium. The data-inferred continuum models are then validated against processes governed by different pulling protocols, thereby demonstrating their predictive capability. The methods presented here represent a first step toward full material characterization from non-equilibrium data of macroscopic observables, which could potentially be obtained from experimental observations.

The environmental fate of phenanthrene in paddy field system and microbial responses in rhizosphere interface: Effect of water-saving patterns

The effects of water-saving patterns (Semi-dry water-saving, B; Shallow-wet control irrigation, Q; Traditional flooding irrigation, C; and Moistening irrigation, S) on the environmental fate of phenanthrene (Phe) and microbial responses in rhizosphere were investigated in paddy field system. Results showed the rice grain in Q treatment was more high production and safety with less Phe residue (up to 18%-49%) than other treatments, and the residual Phe in soil declined in the order: C (14.17%) > S (13.36%) > B (5.86%)>Q (2.70%), which proves the existence of optimal water conditions for PAHs degradation and rhizosphere effect during rice cultivation. Laccase (LAC) and dioxygenase (C23O) played important roles in Phe degradation, which were significantly positively correlated with Phe dissipation rate in soil (p < 0.01). Moreover, their activities in Q treatment, rhizosphere and subsoil were higher than those in C treatment, non-rhizoshere and upper layer soil. The introduction of Phe and rice into paddy field system decreased the microorganism diversity, and promoted the activities of enzymes and some PAHs degrading bacteria, such as Delftia, Serratia, Enterobacter, Pseudomonas, norank_f_Rhodospirillaceae, norank_f_Nitrosomonadaceae and so on. According to the cluster analysis, redundancy analysis and correlation analysis between bacterial community composition and environmental factors, water-saving patterns markedly impacted the relative abundance and bacterial community structure by the regulating and controlling on environmental conditions of paddy field. The dioxygenase activity, laccase activity, oxidation-reduction potential and conductivity were the main affecting factors on Phe dissipation during growth stage of rice.

Comparison the dissipation behaviors and exposure risk of carbendazim and procymidone in greenhouse strawberries under different application method: Individual and joint applications

The dissipation behaviors and exposure risks of individual and joint application of procymidone and carbendazim in greenhouse strawberries were studied. The initial concentrations were similar after individual or joint applications, while the dissipation half-lives and finial concentrations were significantly different. After joint application, the dissipation half-lives of procymidone and carbendazim were 12.9 and 16.0 days, respectively, which were about 1.8 times higher than those after individual application. Furthermore, the final residues under joint application condition were 1.8-3.5 times higher than those under individual application condition. The joint application decreased the dissipation rates of procymidone or carbendazim in strawberries, and increased the final residue concentrations. The dietary intake risks of procymidone and carbendazim (whether applied individually or jointly) were no higher than 0.12, which were acceptable for human health. This work would shed a light for the guidance of the joint application and risk assessment of the typical fungicides in strawberry.

Equivalent Scalar Stress Formulation Taking into Account Non-Resolved Turbulent Scales

PURPOSE

Cardiovascular engineering includes flows with fluid-dynamical stresses as a parameter of interest. Mechanical stresses are high-risk factors for blood damage and can be assessed by computational fluid dynamics. By now, it is not described how to calculate an adequate scalar stress out of turbulent flow regimes when the whole share of turbulence is not resolved by the simulation method and how this impacts the stress calculation.

METHODS

We conducted direct numerical simulations (DNS) of test cases (a turbulent channel flow and the FDA nozzle) in order to access all scales of flow movement. After validation of both DNS with literature und experimental data using magnetic resonance imaging, the mechanical stress is calculated as a baseline. Afterwards, same flows are calculated using state-of-the-art turbulence models. The stresses are computed for every result using our definition of an equivalent scalar stress, which includes the influence from respective turbulence model, by using the parameter dissipation. Afterwards, the results are compared with the baseline data.

RESULTS

The results show a good agreement regarding the computed stress. Even when no turbulence is resolved by the simulation method, the results agree well with DNS data. When the influence of non-resolved motion is neglected in the stress calculation, it is underpredicted in all cases.

CONCLUSION

With the used scalar stress formulation, it is possible to include information about the turbulence of the flow into the mechanical stress calculation even when the used simulation method does not resolve any turbulence.

Dissipation, accumulation and risk assessment of fungicides after repeated spraying on greenhouse strawberry

Repeated spraying of fungicides is a common phenomenon in greenhouse strawberry cultivation, and the continuous harvest of strawberries makes them prone to contamination by accumulated fungicides. Despite this, very few residue safety assessments of fungicides on greenhouse strawberries are conducted after repeated spraying of fungicides, and no research exists on fungicide dissipation and accumulation mechanism. Therefore, the present study investigated the dissipation and accumulation of four fungicides (pyraclostrobin, pyrimethanil, procymidone, and cyprodinil) after two typical repeated sprayings (a single fungicide repeated spraying and two fungicides sprayed using an alternate repeated technique). The half-life of pyraclostrobin after three single repeated sprayings was 18 d; however, its average half-life decreased to 9 d after alternate repeated spraying with cyprodinil. The shortened half-life may be attributed to cyprodinil water solution washing during alternate repeated spraying. The other three fungicides showed similar half-lives after single and alternate repeated spraying, following the order of cyprodinil (12 d and 10 d) > procymidone (11 d and 10 d) > pyrimethanil (6 d and 7 d). The octanol-water partition coefficient was a more efficient indicator of the half-life order of the fungicides than vapor pressure and water solubility. Pyraclostrobin showed the highest deposition efficiency but negligible residue accumulation; further, the residue accumulation of the four fungicides followed the order of procymidone > cyprodinil > pyrimethanil > pyraclostrobin after both single and alternate repeated spraying. A safety assessment demonstrated that the maximum number of times cyprodinil could be sprayed after single spraying was one; however, this number doubled after alternate spraying. The risk of exceeding the maximum residue limits of the fungicides on greenhouse strawberries decreased; however, the combined dietary risks of fungicides after alternate spraying might be high. Alternate repeated spraying of procymidone and pyrimethanil may be the optimal repeated spraying combination for greenhouse strawberries.

Drift, dissipation and risk to wildlife following targeted herbicide applications on boreal transmission rights-of-way

Herbicide use on boreal transmission line rights-of-way has been relatively limited compared to more temperate regions and therefore challenges exist in estimating and communicating the associated risks. Herbicides directly enter the ecosystem through deposition on vegetation and soils and can be a vector of contamination to browsing herbivores. Triclopyr drift and foliage concentrations were quantified following basal bark (Garlon RTU) and low-volume foliar (Garlon XRT) field treatments to aspen (Populus tremuloides) saplings and willow (Salix bebbiana) shrubs, respectively. Greater drift concentrations localized at the stem base were observed following basal bark treatments. Conversely, concentrations in foliage following the low-volume foliar treatment (DT₅₀ = 5.7 days and DT₉₀ = 34.6 days) were much higher than following basal bark treatment, which also required two days to translocate into the leaves. However, dissipation was rapid from both application methods and triclopyr in foliage was less than 20 μg g^-1 a year following application. A risk assessment revealed an acceptable level of risk for acute toxicity to wildlife browsing on contaminated leaves from the residues detected in this study; however, an unacceptable level of risk for chronic toxicity to long-term browsing moose. Site-specific data regarding browsing behaviour on herbicide treated rights-of-ways and species-specific reference values are needed to improve confidence in the tier-two risk assessment. Basal bark application is ideal when stem density is lower and toxic effects for herbivores is of concern and low-volume foliar applications are best suited in areas with higher stem density when off-target herbicide deposition is less acceptable.

The fate and effect of chlorpyrifos and lambda-cyhalothrin in soybean (Glycine max L. Merril) field

Soybean pod borer (Leguminivora glycinivorella) is an important pest in soybean production, and chemical pesticides was major way for prevention. However, it is difficult to balance the efficiency and safety of pesticide application. In this paper, we evaluated safety and effectiveness of common insecticides (chlorpyrifos and lambda-cyhalothrin) on soybean from three aspects, including distribution, dissipation and control effect, around three major soybean production area (Anhui, Jilin and Shandong) in China. For chlorpyrifos, the initial deposition of each position (upper leaf, lower leaf, upper stem, lower stem, soybean and root) was determinated for 0.23 mg/kg to 70.7 mg/kg, and the half-lifes ranged from 1.96 days to 5.36 days. For lambda-cyhalothrin, the initial deposition of the position was determinated for 0.10 mg/kg to 2.54 mg/kg, and the half-lifes ranged from 2.45 days to 7.26 days. We found that the target insecticides were major deposition and faster degradation in upper stem and leaf. Through comparing the relationship between field control effect and residue, it can be suggested that 40% chlorpyrifos EC and 2.5% lambda-cyhalothrin WE should be sprayed at 600 g a.i./ha and 5.63 g a.i./ha for SPB prevention. This study enhanced our understanding of distribution, dissipation and relationship between residue and control effect. The results provided data support for guiding the precise and scientific application of chemical insecticides on soybean.

Surface acceleration transmission during drop landings in humans

The purpose of this study was to quantify the magnitude and frequency content of surface-measured accelerations at each major human body segment from foot to head during impact landings. Twelve males performed two single leg drop landings from each of 0.15 m, 0.30 m, and 0.45 m. Triaxial accelerometers (2000 Hz) were positioned over the: first metatarsophalangeal joint; distal anteromedial tibia; superior to the medial femoral condyle; L5 vertebra; and C6 vertebra. Analysis of acceleration signal power spectral densities revealed two distinct components, 2-14 Hz and 14-58 Hz, which were assumed to correspond to time domain signal joint rotations and elastic wave tissue deformation, respectively. Between each accelerometer position from the metatarsophalangeal joint to the L5 vertebra, signals exhibited decreased peak acceleration, increased time to peak acceleration, and decreased power spectral density integral of both the 2-14 Hz and 14-58 Hz components, with no further attenuation beyond the L5 vertebra. This resulted in peak accelerations close to vital organs of less than 10% of those at the foot. Following landings from greater heights, peak accelerations measured distally were greater, as was attenuation prior to the L5 position. Active and passive mechanisms within the lower limb therefore contribute to progressive attenuation of accelerations, preventing excessive accelerations from reaching the torso and head, even when distal accelerations are large.

Dissipation, Fate, and Toxicity of Crop Protection Chemical Safeners in Aquatic Environments

Safeners are a group of chemicals applied with herbicides to protect crop plants from potential adverse effects of agricultural products used to kill weeds in monocotyledonous crops. Various routes of dissipation of safeners from their point of applications were evaluated. Despite the large numbers of safeners (over 18) commercially available and the relatively large quantities (~2 × 10⁶ kg/year) used, there is little information on their mobility and fate in the environment and occurrence in various environmental matrices. The only class of safeners for which a significant amount of information is available is dichloroacetamide safeners, which have been observed in some rivers in the USA at concentrations ranging from 42 to 190 ng/L. Given this gap in the literature, there is a clear need to determine the occurrence, fate, and bioavailability of other classes of safeners. Furthermore, since safeners are typically used in commercial formulations, it is useful to study them in relation to their corresponding herbicides. Common routes of dissipation for herbicides and applied safeners are surface run off (erosion), hydrolysis, photolysis, sorption, leaching, volatilization, and microbial degradation. Toxic potencies of safeners vary among organisms and safener compounds, ranging from as low as the LC₅₀ for fish (Oncorhynchus mykiss) for isoxadifen-ethyl, which was 0.34 mg/L, to as high as the LC₅₀ for Daphnia magna from dichlormid, which was 161 mg/L. Solubilities and octanol-water partition coefficients seem to be the principal driving force in understanding safener mobilities. This paper provides an up-to-date literature review regarding the occurrence, behaviour, and toxic potency of herbicide safeners and identifies important knowledge gaps in our understanding of these compounds and the potential risks posed to potentially impacted ecosystems.

Dissipation behavior of thiophanate-methyl in strawberry under open field condition in Egypt and consumer risk assessment

Thiophanate methyl is a broad-spectrum benzimidazole fungicide extensively applied in pre- and post-harvest, for the control of a wide range of fruit and vegetable pathogens. In the current work, the residue behavior of thiophanate methyl after application on strawberries and an estimation of the consumer dietary exposure was performed. Supervised field trials were conducted in Egypt (Qaluobiya Governorate) as to investigate the residue dynamics and terminal residues at different PHIs of thiophanate methyl and its metabolite carbendazim in strawberries under Egyptian conditions. For the measurement of residues in fruits, a QuEChERS-based protocol coupled with LC-MS/MS was optimized and successfully validated at 0.01 mg kg^-1. The half-life (t_1/2) of thiophanate methyl in strawberries was estimated, and a dietary risk assessment was performed employing both FAO/WHO and EFSA approaches.

Bi-component T2 mapping correlates with articular cartilage material properties

Non-invasive estimation of cartilage material properties is useful for understanding cartilage health and creating subject-specific computational models. Bi-component T2 mapping measured using Multi-Component Driven Equilibrium Single Shot Observation of T₁ and T₂ (mcDESPOT) is sensitive for detecting cartilage degeneration within the human knee joint, but has not been correlated with cartilage composition and mechanical properties. Therefore, the purpose of this study was to investigate the relationship between bi-component T₂ parameters measured using mcDESPOT at 3.0 T and cartilage composition and mechanical properties. Ex-vivo patellar cartilage specimens harvested from five human cadaveric knees were imaged using mcDESPOT at 3.0 T. Cartilage samples were removed from the patellae, mechanically tested to determine linear modulus and dissipated energy, and chemically tested to determine proteoglycan and collagen content. Parameter maps of single-component T₂ relaxation time (T₂), the T₂ relaxation times of the fast relaxing macromolecular bound water component (T_2F) and slow relaxing bulk water component (T_2S), and the fraction of the fast relaxing macromolecular bound water component (F_F) were compared to mechanical and chemical measures using linear regression. F_F was significantly (p < 0.05) correlated with energy dissipation and linear modulus. T₂ was significantly (p ≤ 0.05) correlated with elastic modulus at 1 Hz and energy dissipated at all frequencies. There were no other significant (p = 0.13-0.97) correlations between mcDESPOT parameters and mechanical properties. F_F was significantly (p = 0.04) correlated with proteoglycan content. There were no other significant (p = 0.19-0.92) correlations between mcDESPOT parameters and proteoglycan or collagen content. This study suggests that F_F measured using mcDESPOT at 3.0 T could be used to non-invasively estimate cartilage proteoglycan content, elastic modulus, and energy dissipation.

Role of climate change variables (standing water and rainfall) on dissipation of chlorantraniliprole from a simulated rice ecosystem

Chlorantraniliprole (CAP) is extensively used for rice pest management. Lack of information on the role of standing water and amount and timing of rainfall on CAP dissipation in rice ecosystem could hamper its prospective use. Present study was performed to investigate the effects of different water regimes (saturated, 5 and 10 cm standing water) and simulated rainfall (40 and 100 mm occurred at 4, 8 and 24 h after CAP application) on leaching, surface runoff and dissipation of CAP into components of rice ecosystem. The results showed highest concentration of CAP residues in soil and plant under saturated condition followed by 5 and 10 cm standing water conditions. Whereas, the highest concentration of CAP in leachates was detected under 10 cm standing water (12.19 ng mL^-1). The results revealed large amount of leaching (21.99 ng mL^-1) and surface runoff (42.25 ng mL^-1) losses of CAP when 100 mm rainfall occurred at 4 h after pesticide application. The total quantity of CAP residues in soil and plant was highest when rainfall occurred at 24 h after pesticide application under both the rainfall amounts. Water stagnation and high intensity rainfall occurred shortly after pesticide application will contribute to pesticide loss to non-target sites through surface run-off and leaching. There will be less pesticide available in soil for plant uptake which may not be sufficient to kill the target organisms.

A laboratory study on dissipation and risk assessment of the proinsecticide thiocyclam and its metabolite nereistoxin in tomato using liquid chromatography high resolution mass spectrometry

Reduced pesticides use, alongside increased organic farming, has created a need for new biological products, such as thiocyclam, to control pests. Thiocyclam has scarcely been studied, making the study of its degradation in fruits and vegetables, such as tomatoes, an urgent requirement. To monitor thiocyclam metabolites in tomato, dissipation studies were carried out using a liquid chromatography-Orbitrap mass spectrometry (UHPLC-Orbitrap MS) method for 60-days after foliar application. Thiocyclam was not persistent (DT₅₀ < 15 days), but nereistoxin - its primary metabolite - remained present in the tomatoes for >60 days. Four nereistoxin metabolites, detected at low concentrations (<100 µg/kg), were also monitored. This is the first time a study has provided dissipation patterns for thiocyclam and nereistoxin. The results obtained suggest revising the legislation concerning these compounds is required. Toxicological studies must also be carried out because there is no toxicity data currently for thiocyclam or nereistoxin.

Halosulfuron methyl did not have a significant effect on diversity and community of sugarcane rhizosphere microflora

Halosulfuron methyl (HM) is a new, highly active sulfonylurea herbicide that has been widely used for weed control in agricultural production. However, its potential ecological risks remain unknown. In this study, we investigated the impact of different concentrations of HM on bacterial communities in sugarcane rhizospheric soil by using 16S rRNA gene high-throughput sequencing. The half-life of HM for 130 mg/kg, 600 mg/kg, and 1300 mg/kg spraying concentrations were 6.64, 9.19, and 9.87 d, respectively. HM application did not alter the alpha or beta diversity of the soil bacterial community, whereas some microbial populations and the main microbial functional groups were significantly altered by HM exposure. The phylum Cyanobacteria and genus unclassified Chloroflexi group KD4-96 were found to be positively correlated with HM concentration in soils, indicating that they are highly involved in the biodegradation of HM in soils. Relationship analysis between soil properties and microbial communities showed that total nitrogen and total phosphorus concentration were two key factors that significantly influenced microbial community structure. To our best knowledge, this is the first microbial ecotoxicological assessment of HM in agricultural soil.

Enhanced dissipation of xenobiotic agrochemicals harnessing soil microbiome in the tillage-reduced rice-dominated agroecosystem

The ubiquitous contamination generating from the frequent input of agrochemicals is a major hurdle affecting the ecological sustainability of agroecosystems. Here, we investigated the dissipation of multiple pesticides in the subtropical rice-dominated landscapes under tillage intensity management, and unveiled the vital role of soil microbiome in promoting xenobiotic degradation. Three commonly used pesticides (including herbicide butachlor, insecticide clothianidin and fungicide tricyclazole) showed rapid dissipation dynamics in the field where the reduction of tillage intensity with straw incorporation was conducted. In response to pesticide exposure, soil microbial communities adapted quickly with slight changes in community composition and diversity. Meanwhile, the microbial xenobiotic degradation-related functions were stimulated, which possibly related to the increased organic carbon and nitrogen in soil. Importantly, these shifts and effects on microbial communities and functions gradually declined after a length of rice growing seasons, suggesting the flexibility of soil microbiome in tackling with long-term xenobiotic disturbance to maintain a diverse and vibrant soil biota. Overall, our study that displayed the enhanced agrochemical dissipation which benefited markedly from the interaction of tillage management and soil microbial functioning, provides important basis and insights for facilitating green, balanced and sustainable agriculture.

Transportation and degradation of decabrominated diphenyl ether in sequential anoxic and oxic crop rotation

This work evaluated the debromination and uptake of ¹⁴C-labeled BDE-209 in rice cultivars grown in anoxic soil for 120 days (d) followed by cultivation of vegetables (peanut, eggplant and pepper) in oxic soil (120 d). Degradation of BDE-209 to lower polybrominated diphenyl ethers (PBDEs) occurred in cultivated soils, and more metabolites were released in oxic soil than in anoxic soil. The crop rotation from anoxic to oxic greatly enhanced the dissipation of BDE-209 in the soil (P < 0.05), in which the dissipation in anoxic soil planted with Huanghuazhan (HHZ, indica) and Yudao 1 (YD1, indica) were 6.8% and 2.4%, respectively, while in oxic soil with peanut and pepper were increased to 25.8% and 21.7%, respectively. The crop rotation also enhanced the degradation of BDE-209 in the soil, the recovered BDE-209 in soil after 120 d anoxic incubation with YD1 was 81.1%, but it decreased to 47.8% and 45.8% after another 120 d oxic incubation. Bioconcentration factors were between 0.23 and 0.36 for rice, eggplant and pepper but reached to 0.5 in peanut, which contains more lipids in the edible portion than the other test crops. The estimated daily intake for vegetables was 0.01-0.07 μg BDE-209-equivalent kg^-1 bw day^-1, which is at least two orders of magnitude below the maximum acceptable oral dose (7 μg kg^-1 bw day^-1). Our work confirms that crop rotation from rice to vegetable enhanced the dissipation and debromination of BDE-209 in the soil, and indicate that sequential anoxic-oxic rotation practice is considered to be effective in remediation of environmental pollutants.

Ultimate fate of herbicide tembotrione and its metabolite TCMBA in soil

Tembotrione is a triketone group herbicide having worldwide applications for weed management in maize. It is considered to be less stable in the environment and its degradation products may have toxicological consequences due to longer persistence and off-site movements. We studied the persistence behavior and leaching potential of tembotrione and its major metabolite TCMBA in clay loam and sandy loam soils having different physico-chemical properties. The rapid transformation of parent tembotrione to degradation products and their high interactions with soil provided challenging task of residues separation from complex soil matrix. Therefore, a novel sample preparation method (modified QuEChERS) was optimized for trace estimation of tembotrione and TCMBA which offered 86.6-95.6% recoveries with limit of detection (LOD) and quantification (LOQ) as 0.001 and 0.003 μg/g, respectively in both soils without any matrix interference. A first order dissipation kinetics was followed by tembotrione and TCMBA residues with half-life ranged from 7.2 to 13.4 days in both soils. Residues reached below detectable limit on 45-60 days after treatments in two application doses. Leaching experiment revealed maximum retention of tembotrione residues from 15 to 25 cm depth in both soils whereas TCMBA show appreciable leaching potential. It was concluded that tembotrione can be phytotoxic to the succeeding crops if applied at late post-emergence stage. TCMBA can contaminate surface and ground water due to continuous and prolonged use of tembotrione particularly in light textured soils.

Residue reduction and risk evaluation of chlorfenapyr residue in tea planting, tea processing, and tea brewing

The chlorfenapyr residues in the entire tea chain, i.e., in tea planting, tea processing, and tea brewing, were systematically investigated. The degradation rate constants of chlorfenapyr in the tea plants ranged from 0.2460 to 0.2870 with the half-life of 2.4-3.0 days, and 87.5-89.9% of the chlorfenapyr in tea shoots dissipated in the interval of 7 days. In the processing process of both black tea and green tea, the chlorfenapyr residue decreased by 59.1-67.6% compared with the residue in tea shoots due to high vapor pressure (1.2 × 10^-2 mPa 25 °C), and drying was the key step that dissipated the chlorfenapyr. A low leaching efficiency of 2.2-3.4% from tea leaves to tea infusion, resulted in low water solubility (0.14 mg L^-1 25 °C), indicated that >90% of the residual chlorfenapyr was eliminated before the intake of tea infusion. On the basis of these results, an extremely large proportion of the chlorfenapyr deposited on tea shoots was degraded during tea planting, tea processing, and tea brewing, and the health risk was reduced primarily in the first and the last step rather than during tea processing. The remaining 0.2% chlorfenapyr sprayed on the tea shoots represents a negligible health risk based on the RQ assessment. The pesticides with high vapor pressure and low water solubility were more recommended in tea garden for pest control.

Dissipation and dietary risk assessment of kasugamycin and saisentong in Chinese cabbage

A quick, easy, cheap, effective, rugged, and safe pretreatment method using dispersive solid-phase extraction was developed to quantify kasugamycin in Chinese cabbage samples by using ultra-performance liquid chromatography/tandem mass spectrometry. A pretreatment method involving precolumn transformation was utilized to determine the residue of saisentong in Chinese cabbage through high-performance liquid chromatography/ultraviolet detection. These methods were successfully applied through field trials to determine the contents of kasugamycin and saisentong in Chinese cabbage. The dissipation of kasugamycin and saisentong in Chinese cabbage followed first-order kinetics with a linear correlation coefficient of 0.9066-0.9731 at the 95% confidence level. The half-lives of kasugamycin and saisentong in Chinese cabbage were 1.8-2.0 and 2.2-3.8 days, respectively. Terminal residual levels of kasugamycin in Chinese cabbage were not detected 14 days after application. The dietary risk assessment of kasugamycin and saisentong in Chinese cabbage showed that their risk quotients were 0.93 and 2.58%, respectively, in the preharvest interval (PHI) of 14 days. Kasugamycin and saisentong in Chinese cabbage did not pose potential health hazards at PHI of 14 days. The maximum residue limits of kasugamycin and saisentong in Chinese cabbage were 0.02 and 0.36 mg/kg, respectively, and 14 days was the safe PHI.

Environmentally relevant concentrations of microplastic exhibits negligible impacts on thiacloprid dissipation and enzyme activity in soil

Microplastics (MPs) as a type of emerging contaminant in the environment have attracted extensive attentions in recent years, and understanding the impacts of MPs on soil biodiversity and functioning are thus increasingly urgent. Nevertheless, few studies were performed to investigate potential effects of MPs on decay of soil organic pollutants in particular pesticides and enzyme activities. Herein, three types of MPs including polystyrene fragments (PS-50) and polyvinyl chloride beads (PVC-42000 and PVC-10) were added to soil at environmentally relevant concentrations (0.2 and 1.0%) to study their impacts on dissipation of thiacloprid and activities of urease, acid phosphatase, invertase and catalase. MPs exhibited negligible impacts on thiacloprid dissipation regardless of MPs type and content, being probably attributed to the unaltered bioavailability of thiacloprid in soil even after an addition of MPs, which was documented by using the hydroxypropyl-β- cyclodextrin (HPCD) extraction method. Batch sorption experiments also exhibited the comparable adsorption capacity of thiacloprid to soil with and without MPs, along with K_f valuses of 3.44-3.77. Besides, MPs exerted negligible effects on enzyme activities of soil. Taken together, this study showed negligible impacts of MPs at environmentally relevant concentrations on thiacloprid dissipation and enzyme activity, expanding our knowledge on impacts of MPs at the environmentally relevant concentrations on pesticide dissipation in soil.

Contribution to COVID-19 spread modelling: a physical phenomenological dissipative formalism

In this study, we propose an evolution law of COVID-19 transmission. An infinite ordered lattice represents population. Epidemic evolution is represented by a wave-like free spread starting from a first case as an epicentre. Free energy of the virus on a given day is defined equal to the natural logarithm of active infected cases number. We postulate a form of free energy built using thermodynamics of irreversible processes in analogy to isotherm wave propagation in solids and non-local elastic damage behaviour of materials. The proposed expression of daily free energy rate leads to dissipation of propagation introducing a parameter quantifying measures taking by governments to restrict transmission. Entropy daily rate representing disorder produced in the initial system is also explicitly defined. In this context, a simple law of evolution of infected cases as function of time is given in an iterative form. The model predicts different effects on peak of infected cases I_max and epidemic period, including effects of population size N, effects of measures taking to restrict spread, effects of population density and effect of a parameter T similar to absolute temperature in thermodynamics. Different effects are presented first. The model is then applied to epidemic spread in Tunisia and compared with data registered since the report of the first confirmed case on March 2, 2020. It is shown that the low epidemic size in Tunisia is essentially due to a low population density and relatively strict restriction measures including lockdown and quarantine.