PAMPA-based Rapid Assessment Of Permeation Of Organic Pollutants On Plant Leaf

Pesticide pollution is the overall source of food insecurity.It is well recognized that as the first barrier of plants,the cuticle plays a key role in the safe-production of agricultural products.However,there are various kinds of pesticides and plant foliage,and the leaf surface structures have large difference at their growth circles.The existing experiments on pesticide infiltration in the cuticle of plants are complicated and cannot be batched operation.The PAMPA parallel artificial membrane permeability test can optimize the simulation of different plant membranes by changing the membrane composition,membrane concentration and pH conditions.In this study,pesticide permeability of different plant foliage were tested.Based on identifying the influencing factors,developed the PAMPA technology that can simulate the osmotic absorption of pesticide on plants'foliage,to test and rerify the permeation of organic pollutants.The permeability of 30 pesticides on the leaf surface of 11 plants were measured by GC-MS,and analyzed the penetration rate.The process of pesticide penetration in plant leaves conforms to first-order dynamics.The permeation rate constant k of 30 pesticides on the leaf surface ranges from 0.004 to 0.817.The penetration rate has obvious difference.The pesticides were divided into organophosphorus insecticides,pyrethroid insecticides and carbamate insecticides.The morphological structure and wax content of leaves of different plants were characterized.The waxy layer structure and composition on leaves of different species are different.The waxes are composed mainly of straight-chain alkanes?45.65%⁹0.24%?and contain a small amount of primary alcohols?3.92%⁴7.83%?,triterpenoids and legusterols?1.63%⁹.83%?.In addition,the direct alkanes are mainly odd number of carbon atomic alkanes,and the content of C₃₁1 alkanes is the highest.By comparing the waxy composition and structure differences of plant maize 1 and maize 2 in the same species but different periods,the waxy structure of plant leaf surface is related to its content and composition.Take 30 kinds of pesticides in the permeability parameters of 11 kinds of plant leaf area,physical and chemical properties of pesticide and the characteristics of plant leaf area for correlation analysis by multivariate linear regression.The results showed that the penetration of pesticides in plant leaves is related to the molecular weight,molecular polarity and contact angle of pesticides.As the contact angle and molecular weight decrease and the molecular polarity increase,and the permeability will increase.The penetration and absorption rate coefficient k of pesticides in plant leaves is related to the contact angle and primary alcohol C₃₀ of the leaves.As the contact Angle decreases and content of primary alcohol increases,the infiltration rate will be faster.The penetration rate of pesticides in plant leaves is related to the contact angle,alkanes C₃₁ and primary alcohols C₃₀.As the contact Angle decreases,alkanes C₃₁ and primary alcohols C₃₀ increases,the permeability will increase.It indicates that the contact angle represent the hydrophilicity and hydrophobicity of pesticides on the leaf surface of plants.Primary alcohols and alkanes are the waxy components and the different content ratio determines the permeability of the leaf surface.Molecular polarity is the basic physical and chemical properties of pesticides and the direct factors that determine the permeability of pesticides.PAMPA artificial membranes with different component contents?membrane A,B,C?and two different pH values were constructed by changing PAMPA artificial film component and pH environment.The permeation of 30 pesticides in PAMPA artificial membrane and their internal structure were investigated.The results show that the structures of the three types of films?A,B and C?are different,but the films with the same composition are similar.The main structures of membrane A-1 and membrane A-2 are lamellar and rod-shaped and the main components are alkanes C₃₁ and primary alcohols C₃₀.The main structures of membrane B-1,membrane B-2,membrane C-1 and membrane C-2 are lamellar with smooth and sparse structure and the main components are alkanes C₃₁ and primary alcohols C₂₈.Membrane b-1,membrane b-2,membrane c-1 and membrane c-2 are similar to cabbage,spinach,lettuce and soybean leaf.The structure of membrane A-1 and membrane A-2 is similar to that of maize leaf.The correlation between artificial film and the permeability of real plant leaf was analyzed.Membrane A-1 can simulate the penetration regular of pesticides on maize leaves?R²=0.61?,and membrane B-1 can simulate the penetration regular of pesticides on lettuce leaves?R²=0.52?.The pH value can affect the infiltration and absorption of artificial membrane,and pH=5.8 can better simulate the penetration process of real plant leaf surface.Membrane A-1 and membrane B-1 were selected to verify the simulated plant effect.The fitting results of measured Fa%between membrane A-1 and maize were R²=0.58,and RMSE=0.80.The fitting results of the measured Fa%between membrane B-1 and lettuce were R²=0.47,and RMSE=0.92.It shows that both models are available and have good predictive effect.