Effects Of DBP/DEHP On Soil Microbial Biomass Carbon And Enzyme In Single And Complex Pollution With Pb

Phthalate esters (PAEs) compounds are prevalent in the current environment. They are mainly used for plastic plasticizers. In the global plasticizer market, 80% were the phthalate esters. PAEs are not chemical bonded with the PVC resins, which would bring about pollutions for water or soil. Numerous studies found that phthalate esters had potential biological toxicity. In many countries, the use of PAEs was restricted. The U.S. National Environmental Protection Agency lists them as environmental priority pollutants, PAEs have also been known as"the second global PCB pollutants".A variety of pollutants in the environment was not exist alone. Most of pollutants are coexistent, including organic and heavy metal pollution. In this work, the concentrations of DBP and DEHP in farmland and greenhouse soil were monitored,DBP and DEHP were chose to study their degradation and impact in soil biochemical indicators (microbial biomass, metabolic quotients, catalase, invertase, urease and phosphatase). Their combined pollutions with Pb on these indicators were also studied. The findings are as follows:1. The concentrations of DBP and DEHP in soil were determined.(1) The same plastic greenhouses and field soil were selected to determine the concentrations of DBP and DEHP in the whole year. The concentrations of DBP (7.70-14.63 mg/kg) and DEHP (4.92-10.82 mg/kg) in field soil were lower than in greenhouses (2.23-7.31 mg/kg for DBP,3.34-9.53 mg/kg for DEHP). The results showed that DBP may be more easily from the plastic out into the surrounding environment.(2) DBP and DEHP contents were increased gradually from April to September in both greenhouses and farmland soils. The concentrations of DBP and DEHP in field soils reached the maximum and reduced later. The DBP in the greenhouse soil reached the maximum in September and November. The content of DEHP reached the maximum in September, November and April of the following year.2. Biodegradation of DBP and DEHP in the case of single and complex pollutions with Pb in soil(1) DBP/DEHP in soil were degradated mainly through biodegradation. Different concentrations of DBP/DEHP biodegradation processes could be described by pseudo first order reaction (R2 > 0.9). The higher DBP/DEHP concentration in soil, the longer half-life was. In the experimental concentration range, the half-life of DBP biodegradation in soil were 4.38-15.1 days, DEHP were 11.09-26.56 days. The half-life of DBP was less than DEHP in the same concentration, indicating that the biodegradability of DBP was better than DEHP.(2) Pb could inhibit the biodegradation of DBP/DEHP in soil. Biodegradation of DBP in the complex system was still higher than DEHP. When Pb was added, the biodegradation of DBP/DEHP could be also described by pseudo first order reaction (R2 > 0.9). The half-life of DBP/DEHP increased with the increasing initial concentrations. Compared with the same concentration of DBP/DEHP in single treatment, the half-life of DBP/DEHP biodegradation in complex pollutions was significantly longer (extended to 6.19-19.21 and 16.82-47.48 days, respectively).3. The effect of DBP/DEHP on soil microbial biomass carbon (Cmic) and metabolic quotient (qCO2) in single and complex pollution with Pb(1) The changement of microbial biomass carbon was lower-higher-lower-restore stability. The highest value of Cmic in DBP (148.53mg C/kg) treated soil was higher than DEHP (110.54 mg C/kg). The value of qCO2 in DBP treated soil was lower than DEHP. This result showed that the carbon utilization ratio of DEHP was lower than that of DBP.(2) The impact of DBP/DEHP in complex pollution with Pb on soil microbes was not a simple additive effect. In the prophase (25-35 days), the interaction of DBP and Pb on the microbial biomass carbon were smaller than the DBP and Pb alone. In the later experiment, (from 35 days to the end), the interaction gradually higher than the sum of DBP and Pb single. No significant difference was found in the different concentrations of DBP/DEHP and Pb complex treatments on the interaction of soil microbial biomass C.4. The influence of DBP/DEHP on soil enzyme activities in single and complex pollution with Pb(1) The activities of catalase and phosphatase were mainly by DBP/DEHP. The effects of DBP/DEHP on soil invertase were different. The activity of invertase were mainly inhibited by DEHP. DBP inhibited the activity of invertase at low concentrations (10-100mg/kg) and stimulated it at high concentrations (500-1000mg/kg). The activity of urease were inhibited by DBP/DEHP. From 25-35 days, the soil enzyme activities gradually restored and tended to stability.Cultured for 25-35 days from the start, the soil gradually restored the enzyme activity and tend to a stable trend.(2) Compared DBP/DEHP single and compound pollution could found that in the compound pollution soil, the activities of soil enzymes began to show a stable trend from the 42th day, i.e. the introduce of Pb prolonged the trend of soil enzyme activities restoring to stability.(3) Compared with microbial biomass carbon and metabolic quotient, the soil enzyme were nobatly influenced by the changement of DBP/DEHP concentrations in soil.