Effects Of Oxytetracycline And Sulfamethazine On Pepper Physiological Reaction And Physical And Chemical Properties Of Soil

In order to investigate the impact of OTC (oxytetracycline) and SMZ (sulfamethazine) on plant growth development and soil quality by pepper (Capsicum annuum L.) and the pot culture experiment. The main results were showed as follows:The value of pepper growth parameter, for example height and leaf number, decreased after exposed to OTC and SMZ treatment (P<0.05), and the inhibition of antibiorics to plant showed more intense as drug concentration increased. The yield per plant of pepper was more sensitive than height leaf number exposed to antibiotics. Compared with control treatment pepper yield decreased 21.7% and 23.9% at 1 mg kg-1 of OTC and SMZ, while yield of percentage declines had reached 86.8% and 89.6% at 50 mg kg-1 Of OTC and SMZ, respectively. Our study found that inhibiting effect of SMZ on pepper growth was more than OTC under the same concentration. SMZ and OTC concentration reached 100 mg kg-1 and 200 mg kg-1, which it would lead to pepper death, respectively. In addition, the EC50 value (concentration causing 50% effect) of SMZ treatment was less than OTC treatment from plant growth tests, these results suggested that the toxicity of SMZ to pepper growth was greater than OTC.Pepper was stimulated and led to enzyme activity increased in OTC and SMZ treatment (≤1 mg kg-1), but the stimulation would transform to inhibition and enzyme activity decreased with increased of antibiotics concentration (P<0.05). Results of the test indicated that POD (peroxidase) and PPO (polyphenol oxidase) activity in pepper organ (root, stem, leaf and fruit) was showed increased then decreased with increasing of antibiotics. For example, compared with CK treatment, POD activity in leaf increased 38.4% at 1 mg kg-1 SMZ, and it decreased 14.1%～ 80.7%at 5～50 mg kg-1 SMZ; PPO activity in stem increased 51.1% at 1 mg kg-1 OTC and decreased 51.4% at 50 mg kg-1 OTC. In addition, CAT (catalase) activity in pepper was a significant reduction exposed to 1 mg kg-1 of antibiotics (P<0.05), CAT was more sensitive than POD and PPO due to enzyme activity decreased. CAT activity in fruit decreased 13.9%～68.8% and 23.3%～92.4% in 1～50 mg kg-1 of OTC and SMZ, respectively. In conclusion, the effect of SMZ treatment to pepper growth and enzyme activity was stronger than OTC treatment in same concentration.Soil urease, phosphatase and invertase activity decreased significantly under OTC and SMZ pollution (P<0.05), then soil enzymes activity decreased with increasing of antibiotics concentration when OTC and SMZ concentration ≤50 mg kg-1. For example, compared with CK treatment, phosphatase activity decreased 21.8%～52.2% and 19.6%～51.9% at 1～50 mg kg-1 of OTC and SMZ, respectively. Three soil enzymes activity was no significant differences in all treatment when antibiotics concentration>50 mg kg-1 (P>0.05), urease activity decreased 48.9%～ 55.2% and 56.5%～58.4% under 50～200 mg kg-1 of OTC and 50～100 mg kg-1 of SMZ, respectively. However, invertase activity decreased significantly under OTC> 50 mg kg-1 (P<0.05) and percentage decline in 13.1%～48.5%, but it activity only decreased 6.2%～9.6% at 1～10 mg kg-1 of OTC. These implications indicate that invertase was more tolerance than phosphatase and urease, and it activity had a little reduction. The inhibition of SMZ to soil enzymes was stronger than OTC.Soil labile organic carbon (SLOC) content suffered the impact from antibiotics pollution. The content of WSOC (water-soluble organic carbon) and DOC (dissolved organic carbon) was increased with the increasing of OTC and SMZ, WSOC got the largest increase of 137.1 and 251.8%, DOC got the largest increase of 31.9 and 10.7%, respectively; whereas, MBC (microbial biomass carbon) and ROC (readily oxidized carbon) was decreased with the increasing of OTC and SMZ, the largest decrease of MBC was 47.8 and 52.4%, ROC was 4.9 and 7.4%, respectively. The results showed that four kinds of soil labile organic carbons had arranged in sensibility to antibiotics order as follows:WSCO>MBC>DOC>ROC, and the inhibition of SMZ to SLOC was stronger than OTC. In addition, the soil showed mild pollution at end of incubation period and the ratio of MBC to TOC was 0.94%-1.46%, when exposed to 100～200 mg kg-1 OTC and 50～100 mg kg-1 SMZ, respectively; and soil may be self-healing when concentration of OTC and SMZ were less than 50 and 10 mg kg-1 respectively.