Pollution Characteristics Of Typical Contaminates And Physiological Effects Of Antibiotics In The Soil-Vegetable System

Vegetables is the most important crops with critical economic status and enjoys the most widely planned areas in China besides grain crops.With the improvement of people's living standard,market demand for pollution-free vegetables grows increasingly.Safe vegetables has become the focus which people concern about.However,China has more people but less land,and due to high multiple crop index of vegetable production,extensively applied fertilizers and other agricultural supplies,and vegetable bases mostly located in densely populated regions,the pollution of vegetable soil highlights the problem,vegetable quality has gradually become an important factor to restrict its production and development.Regarding the related factors that affect vegetables quality,many researchers pay their attention to the pollution of soil antibiotics and heavy metals except for the improper application of chemical fertilizers and pesticides.In order to study the pollution characteristics of antibiotics and heavy metals in soil-vegetable systems,the effects of soil antibiotics pollution on vegetable growth,and the antibiotic uptake patterns of vegetable crops,this dissertation,based on vegetable fields in the plain located in northern Zhejiang province,analyzes the pollution characteristics of antibiotics and heavy metals in soil-vegetable systems as well as the effects of soil antibiotic pollution on vegetable growth and antioxidant enzyme through sampling analysis,series of pot experiments and biochemical analysis,it discusses the antibiotic uptake patterns of vegetable crops and its infuence factors,and explores how agronomic measures affect antibiotic degradation and bioavailability in vegetable fields.Here follows main results and conclusions1.The investigation of typical vegetable lands showed that the detection rate and residual content of antibiotics in vegetable soils were closely related to fertilization methods.The detection rate and average content of eight antibiotics decreased in the order of:oxytetracycline>sulfamethazine>enrofloxacin>tetracycline>sulfamethoxazole,tylosin>chIortetracycline>sulfadiazine,and tetracycline antibiotics>sulfonamide antibiotics.The detection rate and content of antibiotics in vegetables were also related to application of livestock manure and vegetable types.The detection rate and content of antibiotics in vegetables collected from livestock manure applied farmland was significantly higher than those without application of livestock manure.The detection rate and content of antibiotics in different vegetable products were successively decreased in the order of root vegetables and potatoes>onions garlic and leafy vegetables>melons and solanaceae>legumes.The concentration of antibiotics in onion garlic and leafy vegetables was significantly correlated with the residues of antibiotics in the corresponding soil,but this correlation was not obvious in legumes.The accumulation of Cu,Pb,Zn and Cr was mainly related to the application of organic fertilizer,the accumulation of Cd was mainly related to the application of chemical fertilizers.It was found that water solubility of heavy metals in soil was related to fertilization methods.High water soluble Cr and Pb were mainly found in vegetable fields with applied by chemical fertilizers,while high water soluble Cu and Zn were mainly found in vegetable fields with applied by organic fertilizers.2.The effects of antibiotics on the seed germination and root length of vegetables were related to the concentration of antibiotics in the soil,vegetable varieties and antibiotic types.When the concentration of antibiotics exceeded 50 mg/kg,the antibiotics in the soil could have a significant effect on the extension of vegetable roots.Root extension was used as a sensitive indicator of the toxicity of antibiotics during the germination period of vegetables.Here was sensitivity of different vegetables to antibiotic contamination:pakchoi>radish>tomato and relative toxicity of antibiotics to vegetables:oxytetracycline>sulfamethazine>enrofloxacin>tylosin.Vegetables grown on sandy soils were more susceptible to antibiotics than vegetables grown on loamy soils.When the two antibiotics coexisted in the soil,the effect on the seed germination,bud length and root length of the vegetable was obviously greater than that of the single antibiotic.The effects of antibiotics such as oxytetracycline,tylosin,sulfamethazine and enrofloxacin on the growth of pakchoi and radish(including plant height,root length and biomass)were characterized by"low promotion and high inhibition".When the antibiotic content in soil exceeded 25 mg/kg,the antibiotic contamination in soil inhibited vegetable grew.The inhibition increased with the increase of antibiotic content in the soil.Low concentration of antibiotics can induce the increase of antioxidant enzyme activities(SOD,POD,CAT)in vegetables,thereby scavenging free radicals to protect plant growth.When the content of antibiotic exceeded 25 mg/kg,excessive reactive oxygen species(ROS)were produced in vegetable under antibiotic stress.The balance of production and elimination of ROS was disturbed.Excessive ROS caused membrane peroxidation in cells,which destroyed the membrane structure,the activities of antioxidant enzymes in the plant were reduced and the ability of scavenging free radicals were decreased.3.Growth experiment of radish by using animal manure and adding different doses of oxytetracycline showed that radish can absorb oxytetracycline in soil.The content of oxytetracycline in radish increased with the increase of the concentration of oxytetracycline in soil,and decreased with the increase of crop growth time.The accumulation of oxytetracycline in radish root system was more obvious than that in aboveground part.The bioavailability of oxytetracycline in sandy soil was higher than that of clay soil.When the pollution level exceeded 25 mg/kg,the photosynthesis intensity of radish leaves was significantly reduced,and the biomass of roots and aboveground parts were reduced.The experiment of adding oxytetracycline in different periods showed that the aboveground parts of pakchoi were collected after 20 days of adding oxytetracycline.The accumulation of oxytetracycline was higher in those who applied oxytetracycline at growth period and the seedling stage.The content of oxytetracycline in the aboveground part of pakchoi harvested after 60 days of growth increased with the increase of oxytetracycline time to harvest time interval,and increased with the increase of oxytetracycline level in soil.The research showed that the growth of pakchoi is more susceptible to antibiotic contamination in the early stage than in the later stage,and the accumulation of antibiotics in the harvested pakchoi was more likely to accumulate in the later stage than those in the previous stage.4.Experiments on single and combined contamination of oxytetracycline and sulfamethazine at different concentrations showed that,tomato could simultaneously absorb oxytetracycline and sulfamethazine from the soil and transfer it to organs such as leaves,stems and fruits.The content of oxytetracycline and sulfamethazine in plant tissues increased with the increase of antibiotic contamination level in soil,and the growth stage was higher than the late growth stage.The content of antibiotics in different organs was the highest in roots.followed by leaves,stems and fruits.When the concentration of oxytetracycline and sulfamethazine in the soil was 25 and 50 mg/kg,both oxytetracycline and sulfamethazine could affect the growth of tomato,reducing photosynthetic rate,chlorophyll content,plant height and biomass.High concentration of antibiotic contamination could lead to the accumulation of N,P and K in the leaves of plants.reduces the C/N ratio in leaves,and reduced the content of vitamin C and reducing sugar in fruits,but it had no significant effect on nitrate accumulation.The studies shows that the antibiotic combined pollution in soil has no interaction with the accumulation of oxytetracycline and sulfamethazine in plants and that of two antibiotics in plants,but the two can both enhance the effects on plant growth,physiological indicators and biomass.5.From the simulation experiments on the effects of fertilization,namely organic fertilizer,NPK fertilizer,N fertilizer,PK fertilizer,tillage,namely tillage,no-tillage,water management,namely long-term dry,long-term wet,alternating wet and dry,long-term humidity,and planting,namely planting vegetables,not planting vegetables on the degradation of sulfamethazine in soil it showed that application of organic fertilizer,NPK fertilizer and N fertilizer could promote the degradation of sulfamethazine in soil,and the effect of applying organic fertilizer was the most obvious.Tillage could promote the degradation of sulfamethazine in soil.The long-term and alternating wet and dry wetting were more favorable to the degradation of sulfamethazine than long-term dry and long-term moist soil environment.The degradation of sulfamethazine was higher in planting vegetables compared to soil without vegetables.Tillage could promote the photodegradation intensity of antibiotics in soil.The degradation of sulfamethazine in high nutrient soils was generally higher than in low nutrient soils.The mechanism was related to the change of soil microbial activity by the above measures.