The fate of pesticide on tea plant and the prediction of pesticide residue in fresh leaves of tea plant

The degradative kinetics of pesticides on plant surface are characterized by an initial rapid degradation which follows a first-order kinetics, then transferred to a more slower degradative rate. The degradative process mainly consists of photodegradation, evaporation, rainfall elution and growth dilution. The influencing parameters of these processes were investigated by using the tea plant as a case study. The predictive model of the initial concentration, photodegradation rate constant, evaporation rate constant, rainfall elution rate, growth dilution rate and the total degradation rate was discussed and verified in four locations situated in the range of 25°-30°N latitude, and acceptable results were obtained.

Pesticides residues were estimated in some commonly used medicinal plants collected from different markets in Jeddah, Saudi Arabia ,these are; (Rosemary; Rosmarinus officinals L. & Sage; Salvia officinals L.), family Lamiaceae, (Anise; Pimpinella anisum L., Caraway, Carum carvi L. & Cumin; Cuminum cyminum L.) family Apiaceae, (Cinnamon; Cinnamomum verum L.) family Lauraceae, (Ginger; Zingiber officinale Roscoe. ) family Zingiberaceae and (Tea ; Camellia sinensis L.) family Theaceae. It was found thatMalathion,Pirimiphos-methyl and profenofos predominated in most all investigated samples while fungicides were detected only in Cumin and Caraway samples in the form of azole compounds .(tebuconazole, propiconazole, flusilazole, difenoconazole) carbamate compounds (carbendazim) and other fungicides(iprodione, azoxystrobin, metalaxyl, flusilazole, thiophanate-methyl,ticyclazole, kresoxim-methyl and pendimethalin). Insecticides were dominated in Cumin, Caraway, Anise, Rosemary, Tea and Sage samples and mainly organophosphates (malathion, chlorpyrifos, profenofos, pirimiphos-methyl, ethion. The Ginger samples were free from pesticides while Cinnamon samples showed only the chloropyrifos <LOQ But in Anise difenoconazoleit was only in <LOQ. The medicinal plants and natural herbs must be used after the application of safety experiments and safety tests. It is recommended that everycountry use medicinal plants and spices (collected from natural habitats or cultivated) should have at least one control laboratory capable of performing the determination of pesticides residues and give a license for safety to be used in safe manner.

Tea(Camellia sinensis)is a kind of evergreen shrub or tree,which has been widely planted as an important economic crop in mountainous tropical and subtropical regions of China.Tea gardens are considered both ecologically friendly and economically profitable due to their high plant standing biomass and important role in soil and water conservations.Though it is recognized that the carbon sequestration potential should be huge in the plant and soil of tea gardens,few researches have been carried to quantify their carbon storage and balance.In the tea producing regions of China,tea garden area occupies a large proportion of the total forest area(e.g.3.1% in Zhejiang Province).Tea gardens might play an important role in the carbon sink of forest ecosystems in those areas.Based on publications between 1950 and 2011 on tea plant growth in China,regression models on the relationship between tea stand biomass and tea plant age or tea yield were established to find out how its carbon storage capacity changes and how much its carbon storage capacity can achieve during aproduction cycle of a common double-row tea garden.An exponential growth model was established between tea plant aboveground biomass(Ba)and its age(t):Ba =-14.95+56.3×(1-e-0.27t).Modeling results showed that tea biomass increased rapidly during the first 10 years and then slowly after the first 15years.Carbon(C)mass of 10 and 15year-old tea plants was 92% and 98% of that(30.6t/m2)of 25 year-old tea plants respectively.Carbon accumulation rate was(4.5±0.4)t/(hm2·a) for tea plants of 1-4year-old and was(0.95±0.05)t/(hm2·a)for those of 5-15year-old.When the shoot/root biomass ratio ranged from 1.68 to 2.34,the C mass of 15-year-old tea plants ranged from 31.31 to 28.02t/hm2.A model for C storage in tea garden was set up based on potential photosynthetic productivity of tea plants and tea yield,thus C storage capacity of tea plants in various tea production regions was estimated.With an efficiency of solaremergy utilization of 0.5% currently,the corresponding total C storage was amount to(9.1±1.4)t/hm2 in the tea gardens of China.As for 15-year-old tea plants,the C mass of 60t/hm2 given by the exponential model was close to the theoretical value(56.41t/hm2)with an efficiency of solar emergy utilization of 2%,and the C mass could be up to 70.5t/hm2 in tea gardens if tea yield was increased.In a word,it is important to quantify the carbon stock through modeling on the changes of biomass C accumulation with tea plant age rather than based on limited field sampling data.It is also noted that plant C pool of tea gardens is one of main agroforestry C pools in tea production regions and tea garden has a high plant C sequestration potential in China.

Small unmanned aerial vehicles (UAVs) have been widely used in different aspects of modern farming management, including pest and disease control in China in recent years. In this study, the spray performance of a small plant protection UAV at low volume spray was evaluated by adjusting the pesticide dosage and adding aerial spraying adjuvants. Droplet deposition, droplet density, coverage, control effect and pesticide residue from field trials were assessed. In addition, the residue and control effect of UAV spray were compared to manual knapsack at high volume spray. The results showed that, the adjuvant applying improved the efficiency of UAV spray. Also, the adjuvant applying reduced the dosage of imidacloprid by 20%. However, there was no significant difference on initial residue between UAV spray and knapsack spray. Thus, plant protection UAV spraying pesticide by adding appropriate adjuvant showed the ability of improving the pesticide effectiveness by improving the control efficiency, reducing the pesticide dosage and residue. Keywords: unmanned aerial vehicle (UAV), aerial spraying adjuvant, deposition, control efficiency, pesticide residue, wheat aphid DOI: 10.25165/j.ijabe.20181105.4298 Citation: Meng Y H, Lan Y B, Mei G Y, Guo Y W, Song J L, Wang Z G. Effect of aerial spray adjuvant applying on the efficiency of small unmanned aerial vehicle on wheat aphids control. Int J Agric & Biol Eng, 2018; 11(5): 46–53.

Guidance methods are provided for analysis of residues of pesticides in tea and tea brew. These methods cover most of the pesticides used in tea. Method for analysis of organochlorines, organophosphates and pyrethroids in tea involves extraction of the prehydrated tea samples with acetone. The acetone extract is evaporated, dissolved in water and re-extracted into n-hexane. Further clean-up is done on adsorption column with neutral alumina (activity grade V) as adsorbent and hexane-acetone mixtures as eluting solvents. Pesticide concentrations in the cleaned-up tea extracts are determined using gas chromatograph with either Electron Capture Detector (ECD) or Nitrogen Phosphorous Detector (NPD). Method for Triazole residues in tea is slightly different from the one proposed for organochlorines, organophosphorous and pyrethroids. In this method after acetone extraction, re-extraction is into dichloromethane instead of n-hexane and in adsorption column chromatographic clean-up, the eluting solvent is a mixture of dichloromethane and hexane. Method for pesticide residue analysis in tea brew follows the same steps by starting from re-extraction (liquid-liquid partitioning) step. The proposed methods are derived out of experience on pesticide residue analysis in tea and need to be optimized and validated prior to implementation.

Recently a theory of vapor-to-liquid phase nucleation was developed based on the kinetics of cluster formation and decomposition. The new method used variational transition state theory (VTST) to obtain the evaporation and condensation rate constants needed in the kinetic model of nucleation. VTST provides a means to systematically improve estimates of rate constants involved in the nucleation process. In the current work, we perform dynamical simulations of the condensation process, estimating the effective reactive cross section using a definition of a cluster that is determined from VTST. These calculations allow us to characterize dynamical corrections to the VTST rate constants. We find that for water cluster sizes ranging from 10–40 waters, VTST estimates of the condensation and evaporation rate constants using a spherical dividing surface require dynamical corrections that are approximately a factor of two.

The use of Tea (Camellia sinensis) Seed Shell (TSS) for the removal of Pb (II) and Zn (II) ions from aqueous solution was studied. The effect of contact time, pH, and adsorbent dose were evaluated and the results indicate that optimum adsorption occurred at pH 4 and 5 for Zn (II) and Pb (II) respectively. Kinetic, mechanisms, and thermodynamic parameters have been estimated. Result shows that Pseudo- second order favored the adsorption process with R 2 values of 0.999 and 0.9997 for Pb (II) and Zn (II) ions respectively. Weber and Morris Intraparticle model gave a better fit with intraparticle rate constant, Kid of 94.47 and 89.65 min -1 for Pb (II) and Zn (II) ions respectively. Gibbs free energy, ∆G o , enthalpy change, ∆H o and entropy change, ∆S o values shows that the adsorption process of these metal ions onto tea seed shell (TSS) is feasible, endothermic, and spontaneous in nature. Regeneration of TSS was carried out using 0.2M HCl as eluent and reused for subsequent adsorptions-desorption cycles. These results indicate that Camellia sinensis seed shell can serve as a low cost adsorbent in scavenging Pb (II) and Zn (II) ions from solutions containing same.

Pesticides as agrochemicals are used to control plant diseases, however the use of pesticides may cause poisoning for human health and non-target animals, residual formation in animals and crops, and environmental contamination (soils and water). The impacts of pesticide are generally due to excessively or inappropriate use of pesticides. The surveillance on pesticide residues and/or contamination in animal products, crops and environment conducted in West Java and Lampung shows that some pesticide residues were detected in milk from West Java (Bogor and Pangalengan) including lindane, heptachlor, diazinon and endosulfan. In general, the pesticide residues in milk ofBogor were below the maximum residue limits (MRL), but two pesticide residues in milk of Pangalengan: diazinon (239 ppb) and heptachlor (60,3 ppb) appeared to be sufficiently high for human consumption. Some pesticide residues were also detected in meat, liver and fat of cattle in Bogor and Lampung. Both organochlorine and organophosphate residues were detected in samples of Bogor including: lindane (not detected/nd-135,5 ppb) and diazinon (nd-754,4 ppb) in meat; lindane (nd-16,7 ppb), diazinon (nd-969 ppb) and endosulfan (nd-191,8 ppb) in liver; and diazinon (nd-908,1 ppb) in fat. The residue level of diazinon detected in meat, liver and fat appeared to be higher than the MRL level. On the other hand, there was only organochlorine being detected in meat of Lampung. Regarding to pesticide residues being detected in soils, the source of contamination was then suspected from the contaminated soils where fodders being grown (grass, cabbages and corn). By-products of cabbage and corn are commonly used as animal feed for dairy and beef cattle respectively. The organic fanning system can be used as an alternative to minimise agricultural land contamination and pesticide residues in agricultural products. The low pesticide residues in agricultural by-products were able to reduce pesticide residues in animal products (meat and milk). The possibility of pesticide contamination should be taken into account in using agricultural by-products for animal feed to prevent pesticide residual effects in animal products. Key words: Residue, pesticides, minimalization, animal, organic

In previous work we began the description of a molecular theory of homogeneous vapor-to-liquid nucleation based on the kinetics of cluster formation and decomposition. In this work we focused on a new theoretical approach to calculating rate constants for evaporation of molecules from clusters. In the present work, we present a molecular theory for calculating condensation rate constants that are consistent with the evaporation rate constants. The new method, which uses variational transition state theory (VTST), provides an expression for the evaporation rate constant that is proportional to the derivative of the Helmholtz free energy for cluster formation with respect to the radius of the spherical volume constraining the cluster. Furthermore, the theory provides a physically justified procedure for selecting a unique value of the radius of the spherical volume for each i-molecule cluster. Since VTST obeys detailed balance, condensation rate constants can be obtained from the evaporation rate constants and the corresponding equilibrium constants. In the present work, we provide a theoretical approach to obtain the equilibrium constants that are consistent with the evaporation rate constants. Monte Carlo methods are presented for calculating the dependence of the Helmholtz free energy of cluster formation on the radius of the constraining volume, which are needed for the evaporation rate constants. In addition, Monte Carlo methods are presented for calculating the relative differences in Helmholtz free energies for clusters of different sizes, which are needed for the equilibrium constants and condensation rate constants. The volume dependent Helmholtz free energies for the water dimer up to the decamer are calculated at 243 K.

Predicting pesticide residue masses in environments requires time- and cost-efficient fate models, particularly for high-throughput simulations of hundreds of active ingredients registered for use in agriculture. Due to the adaptability of first-order kinetics-based models for simulating the fate of pesticides in environments of varying scales, we conduct a review of these models in the present investigation. We discuss the application of first-order kinetics-based fate models in different types of compartments, such as environmental media, plant tissues, and animal bodies, and at different levels, such as the product-oriented life cycle impact assessment and the chemical-oriented health risk assessment. In addition, the first-order kinetics-based rate constants of pesticides provide process- and scenario-specific information on the fate, transport, and transformation of pesticides, which is essential for predicting pesticide residue masses in different environmental compartments. By varying the level of model complexity and site-specific rate constants of pesticides, the first-order kinetics-based fate models can be used as either comparable or absolute tools for conducting the life cycle impact assessment or the health risk assessment of pesticides, respectively. Bioconcentration, bioaccumulation, and biomagnification of pesticides may be evaluated with the aid of an inventory database of rate constants based on first-order kinetics in future research. We suggest incorporating non-first-order kinetic processes into the first-order kinetics-based model to advance risk assessment, as well as approximating non-first-order kinetic processes using first-order kinetics to facilitate life cycle impact or screening-level risk assessments.

Photodegradation of methylmercury in Jialing River of Chongqing, China

The indiscriminate use of toxic pesticides had created an environment that without this poison the plant life is unfruitful leading to the farmer's life miserable. For several years, this phenomenon was continuing and the ecosystem is protecting the environment and the life of human being from high risk of toxicity. But, how long it will continue or weather a paradigm change in the agricultural field is required? With this objective a field study was conducted in the cardamom plantations of Idukki district in South India to estimate and predict the persistence of pesticide residue in the soil environment. It is observed that residues of endosulfan, DDT and organophosphorous pesticides were present in soil samples at 31.6 %, 29 % and 21 % respectively. The present study gives a prediction of the concentration of persistent pesticide residues in the soil if the present dose and frequency of application is continued. The study also highlighted the adsorption capacity of soil in the study area and low water solubility of pesticides used in cardamom plantations which is referred as partition coefficient. The soil properties such as pH, organic content and microbial concentration which determine the fate of degradation of pesticides and formation of its metabolites are also been discussed in this context. Based on the observations and analysis, it is concluded that the formation of degradation products and bound residues decrease at higher concentration of pesticide applications but the concentration of persistent pesticides increases and the biodegradation reduced in such cases due to bound residues and reduced biological activity. The predicted values on multiple applications where the concentrations in soil may build up and reach a plateau, are 2.559,0.2559, 1.7324 and 0.659 mgKg -1 in the case of endosulfan, DDT, organophosphorous and

In this paper, a multiresidue method for the simultaneous target analysis of 74 pesticides and metabolites in traditional Chinese herbal medicines (TCHMs) was developed using accelerated solvent extraction (ASE) coupled with HPLC/MS/MS. Pesticide residues were extracted from the different samples using ASE, then purified by gel permeation chromatography and graphitized carbon black/primary, secondary amine SPE. Gradient elution was used in conjunction with positive mode electrospray ionization MS/MS to detect 74 pesticides and metabolites from Cortex Cinnamomi, Flos Carthami, Folium Ginkgo, Herba Pogostemonis, Radix Ginseng, and Semen Ginkgo using a single chromatographic run. The analytical performance was demonstrated by the analysis of extracts spiked at three concentration levels ranging from 0.005 to 0.125 mg/kg for each pesticide and metabolite. In general, recoveries ranging from 70 to 110%, with RSDs better than 15%, were obtained. The recovery and repeatability data were in good accordance with European Union guidelines for pesticide residue analysis. The LOD for most of the targeted pesticides and metabolites tested was below 0.01 mg/kg.

Revisiting the International Estimate of Short‐Term Intake (IESTI equations) used to estimate the acute exposure to pesticide residues via food

The kinetics of PCBs evaporation and elimination during PCB degradation by bacterial strain Pseudomonas stutzen (isolated from a long‐term PCB contaminated soil) in liquid medium were monitored. The evaporation and elimination rate constants for individual PCB congeners were determined using a simple mathematical model. The evaporation rate constants are comparable with or higher than the elimination rate constants in these experiments.