[Research Process on the Combined Pollution of Microplastics and Typical Pollutants in Agricultural Soils].

As a new type of environmental persistent pollutant， microplastics can not only have adverse effects on the ecosystem but also form complex pollution with co-existing pollutants in the surrounding environment， resulting in higher ecological and health risks. Based on the perspective of agroecosystems， this study focused on the combined pollution of heavy metals， pesticides， and antibiotics， which are three typical pollutants of farmland soil， as well as microplastics and discussed the adsorption-desorption behavior of heavy metals， pesticides， and antibiotics on microplastics. The influence of the structure and properties of microplastics， the physicochemical properties of pollutants， and environmental conditions on the adsorption and desorption behavior of heavy metals， pesticides， and antibiotics on microplastics was discussed. The influence of microplastics on the bioavailability of heavy metals， pesticides， and antibiotics in farmland soil and the internal mechanism were expounded. The existing problems and shortcomings of current research were pointed out， and the future research direction was proposed. This study can provide a scientific reference for ecological risk assessment of the combined pollution of microplastics and typical pollutants in farmland soil.

[Oxidative Stress and DNA Damage Induced by DEP Exposure in Earthworms].

Diethyl phthalate (DEP) is a plastic additive that entered the soil environment due to the extensive use of plastic products. However, its toxicity to soil animals and the associated toxicity mechanism were not completely understood. Eisenia foetida was selected as the research object and exposed to simulated contaminated soil with different concentrations of DEP. Antioxidant enzyme activity, reactive oxygen species (ROS) content, Glutathione-S-Transferase (GST) activity, Malondialdehyde (MDA) content and amount of DNA damage in the earthworms were used as evaluation parameters for the study. The results showed that under DEP stress, the activities of antioxidant enzymes, GST and ROS in earthworms changed and resulted in gene damage. Under the stress of 0.1-50 mg·kg-1 DEP exposure during the 28 d experiment, the level of ROS increased and there was a "dose-effect" relationship. Excessive ROS gave rise to an increase of MDA content in the body from lipid peroxidation. Under the combined action of ROS and MDA, DNA in the body cavity of earthworm was damaged and there was also a "dose-effect" relationship between the degree of damage and the concentration of DEP. In summary, DEP may cause a certain degree of damage to organisms, with damage to the DNA of earthworms representing fairly strong eco-toxicological effects. Therefore, adequate attention should be paid to DEP disposal.

[Influence of Four Kinds of PPCPs on Micronucleus Rate of the Root-Tip Cells of Vicia-faba and Garlic].

In order to determine the degree of biological genetic injury induced by PPCPs, the genotoxic effects of the doxycycline (DOX), ciprofloxacin (CIP), triclocarban (TCC) and carbamazepine (CBZ) in the concentration range of 12.5-100 mg · L⁻¹ were studied using micronucleus rate and micronucleus index of Vicia-fabe and garlic. The results showed that: (1) When the Vicia-faba root- tip cells were exposed to DOX, CIP, TCC and CBZ, micronucleus rates were higher than 1.67 ‰ (CK1), it was significantly different from that of the control group (P < 0.05), and the micronucleus index was even greater than 3.5; With the increasing concentrations of the PPCPs, the micronucleus rates first increased and then decreased. (2) When the garlic root tip cells were exposed to DOX, CIP, TCC and CBZ respectively, the micronucleus rates were less than those of the Vicia-faba, while in most treatments significantly higher than that of the control group (0.67‰). The micronucleus index was higher than 3.5 in the groups exposed to CIP with concentrations of 25, 50, 100 mg · L⁻¹ and TCC and CBZ with concentrations of 25 mg · L⁻¹; With the increase of exposure concentrations, the micronucleus rate showed a trend of first increasing and then decreasing as well. (3) Under the same experimental conditions, the cells micronucleus rates of the garlic cells caused by the four tested compounds were significantly lower than those of Vicia-faba. (4) The micronucleus index of the root tip cells of Vicia-faba and garlic treated with the four kinds of compounds followed the order of CIP > CBZ > TCC > DOX. These results demonstrated that the four compounds caused biological genetic injury to root-tip cells of Vicia-faba and garlic, and the genetic damage caused to garlic was significantly lower than that to Vicia-faba. The damages caused by the four kinds of different compounds were also different.

[Spatial distribution and risk assessment of atrazine in Taizi River basin, China].

Atrazine (AT) has been detected in surface water and groundwater in many countries and regions around the world. Concentrations of AT in surface water, suspended particulate matter (SPM) and groundwater samples collected from the Taizi River basin, in northeast China, were analyzed using a gas chromatograph-mass spectrometer (GC-MS) in order to clarify their spatial distribution and environmental behavior, and to assess their potential ecological risk. Concentrations of AT varied from 0-734.0 ng x L(-1) for surface water, 0-1 493.6 ng x g(-1) for SPM and 30.0-245.0 ng x L(-1) for groundwater, with averages of 335.3 ng x L(-1), 382.9 ng x L(-1), and 104.4 ng x L(-1), respectively. The logarithm in situ SPM-water partition coefficients (lg k(oc)) of AT were in the range of 3.50-4.14 indicating that adsorption of AT from the aqueous phase to SPM plays an important role in dissipating AT in surface water. Fluxes of AT in surface water ranged from 1.5-184.7 mg x s(-1) in the basin, calculated based on the measured flow velocity and concentrations in surface water and SPM. The maximum value of AT flux was found in the middle stream of the Taizi River (S7). The risk assessment suggested that the ecological risk of AT in surface water was low, with more than 95% of the species protected from risk in the Taizi River basin. However, the residue levels of AT in surface water of the Taizi River basin may cause potential environmental risks.

The combined stress effects of atrazine and cadmium on the earthworm Eisenia fetida.

To assess the combined toxic effects of atrazine and cadmium on earthworms, specimens of Eisenia fetida were exposed in artificial soil to three concentrations of atrazine (0, 0.5, and 2.5 mg kg(-1)) and a range of concentrations of cadmium (Cd; 0, 0.03, 0.3, and 3.0 mg kg(-1)) both singly and as mixtures. The DNA damage and internal atrazine and cadmium concentrations were assessed in earthworms on days 7, 14, 21, and 28 of the treatment. The results showed that the olive tail moments (OTMs) at individual atrazine and cadmium concentrations were significantly higher than those of the controls (p < 0.01). As exposure to atrazine or cadmium progressed, the OTMs increased and the maximum value occurred on day 28. In all combined treatments, the OTMs were much less than those of the sum of individual atrazine and cadmium OTMs, suggesting that the combined effects of atrazine and cadmium were less than additive. The less than additive toxicity of atrazine and cadmium might be due to the formation of atrazine-cadmium complexes or the activation of detoxification isozymes. Moreover, there was a significant correlation between internal atrazine or cadmium concentrations and DNA damage in most exposures, indicating that body residues were consistent with toxicity response.

Biochemical responses of earthworm (Eisenia foetida) to the pesticides chlorpyrifos and fenvalerate.

The effects of chlorpyrifos and fenvalerate on the activity of the cellulase, superoxide dismutase (SOD) and catalase (CAT) of the earthworm (Eisenia foetida) were studied. Earthworms were exposed to chlorpyrifos and fenvalerate at a final concentration of 10, 20, and 40 mg/kg dry soil, respectively. Tissues from each treatment were collected on days 1, 3, 5, and 7. Compared to the controls, the cellulase activity of E. foetida was inhibited by treatments with chlorpyrifos and fenvalerate. The SOD activity of earthworms exposed to chlorpyrifos was significantly inhibited compared to the control after 1 day of incubation, whereas SOD activity increased on day 3. As exposure to the pesticide progressed, the SOD activity recovered from the stimulative effect and reached the level of the control. The SOD activity of E. foetida in the presence of fenvalerate stress was significantly inhibited at the initial stage of exposure and increased after day 3, whereas the SOD activity continued to decrease in response to increasing exposure to fenvalerate. The CAT activity of E. foetida during pesticide stress first increased and then decreased, after day 5, compared to the controls. Alterations of the enzyme activity under environmental stresses are suggested as indicators of biotic and abiotic stress.

DNA damage and effects on antioxidative enzymes in zebra fish (Danio rerio) induced by atrazine.

The effect of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1, 3, 5-triazine) on the activity of some antioxidative enzymes (superoxide dismutase, SOD; catalase, CAT; and guaiacol peroxidase, POD) and DNA damage induced by atrazine were investigated in zebra fish (Danio rerio). Zebra fish were exposed to four different concentrations of atrazine (0, 2.5, 5, and 10 mg/L) for 7, 14, and 21 days, with three replicates of 10 fishes per treatment. Compared to the controls, the SOD activity in the 2.5 mg/L treatment was markedly stimulated in 21 days, while the SOD activities in the 5 mg/L treatment was stimulated at first and then inhibited. The change of CAT activity at 2.5 mg/L was similar to the SOD activity at 2.5 mg/L. The POD activities in the 2.5, 5, and 10 mg/L treatment were markedly higher on days 14 and 21 compared with the controls. The olive tail moments of single-cell gel electrophoresis (SCGE) of zebra fish enhanced after treatment of different doses on days 7, 14, and 21, and significant differences were found compared to the controls. In conclusion, these findings showed the effect regularity of atrazine to zebra fish, and also provide the basis for the future research of adverse effects induced by atrazine in aquatic ecosystems.

[Effects of nitrogen and phosphorus fertilizer on atrazine degradation and detoxification by degrading strain HB-5].

An atrazine-degrading strain HB-5 was used as a bacteria for biodegradation. Treatments of soil with nitrogen single, phosphate single and nitrogen phosphate together with HB-5 were carried out for degradation and eco-toxicity test; then, relationship between atrazine degradation rate and soil available nitrogen, available phosphorus were discussed. Atrazine residues were determined by HPLC; available nitrogen was determined with alkaline hydrolysis diffusion method; available phosphorus was determined with 0.5 mol/L-NaHCO3 extraction and molybdenum stibium anti-color method, and toxicity test was carried out with micronucleus test of Vicia faba root tip cells. The results showed that: After separately or together application, nitrogenous and phosphorous fertilizers could significantly accelerate atrazine degradation than soil with HB-5 only. On day 5, the order of atrazine degradation was ANP > AP > AN > A; 7 days later, no statistically significant differences were found between treatments. The available nitrogen and phosphorus level in soil reduced as the degradation rate increased in the soil. The soil of eco-toxicity test results indicated that the eco-toxicity significantly reduced with the degradation of atrazine by HB-5, and the eco-toxicity on treatments of soil with fertilizer were all below the treatments without fertilizer. On day 5, the order of eco-toxicity was ANP < AP < AN < A; 7 days later, all treatments were decreased in control levels. So, adjusting soil nutrient content could not only promote atrazine degradation in soil but also could reduce the soil eco-toxicity effects that atrazine caused. All these results could be keystone of atrazine pollution remediation in contaminated soil in the future.

Assessment of the genotoxicity of endosulfan in earthworm and white clover plants using the comet assay.

Endosulfan, as one of the most widely used organochlorine pesticides in the world, has increased the public concern about genotoxicity in soil ecosystems. The comet assay has been widely used in the fields of genetic toxicology and environmental biomonitoring. In the present study we conducted comet assay of endosulfan in earthworm (Eisenia foetida) and white clover (Trifolium repens L.), which are sensitive organisms suitable for acting as a bioindicator for agricultural ecosystems. Earthworms were exposed to endosulfan concentrations of 0.1, 1.0, and 10.0 mg/kg in the soil. White clover roots were immersed in hydroponic pots containing nutrient solutions of different endosulfan concentrations: 0.1, 1.0, and 10.0 mg/L. Tissues from each treatment were collected on the 7th, 14th, 21st, and 28th days of treatment process. Significant effects (p < 0.01) of both concentrations and times of exposure were observed. And endosulfan induced DNA damage in earthworm and white clover nuclei. The comet assay can be used as a reliable tool for early detection of endosulfan.

Effects of atrazine on DNA damage and antioxidative enzymes in Vicia faba.

To evaluate atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) ecotoxicology in soil, the effect of atrazine on the activity of antioxidative enzymes (superoxide dismutase [SOD], catalase [CAT], and guaiacol peroxidase [POD]) was investigated in Vicia faba roots. Tissues from each treatment were collected on the days 7, 14, 21, and 28. Compared with the controls, SOD activity in V. faba roots was stimulated by the 2.5 mg/kg treatment and inhibited by the 5 and 10 mg/kg treatments, and CAT and POD activities in the 10 mg/kg treatment were inhibited on the whole. The Olive tail moments of single-cell gel electrophoresis of root cells were enhanced after treatment with different doses of atrazine on days 7, 14, 21, and 28, and significant differences were found compared to the controls. In conclusion, atrazine induces oxidative stress and DNA damage on V. faba.

[Preparation and spectroscopic studies of nanosilver/silk-fibroin composite].

The development of reliable, eco-friendly processes for the synthesis of nanomaterials is an important aspect of nanotechnology today. One approach that shows immense potential is based on the in situ synthesis of noble metal nanocolloids using natural biological material such as silk fibroin. In the present paper, the nano-Ag/silk-fibroin colloids were prepared by in situ reducing AgNO3 with silk-fibroin at room temperature without any reducing agent. UV-Vis absorption, atomic force microscopy, fluorescence spectra and resonance scattering spectra were used to study the preparation process and characterization of the nanocomposite. It was found that the formative Ag nanoparticles were attributed to the tyrosine residues in the chains of silk-fibroin that act as reduction agent in the reduction course of AgNO3, and the Ag nanoparticles were uniformly embedded in silk-fibroin colloid, which possess good dispersity and stability and can be kept for a long period. The strength of fluorescence spectra increased after reaction of silk-fibroin with AgNO3 solution, showing that there was a strong chemical adsorption between silver nanoparticles and silk-fibroin, and a stable complex layer was formed in silver nanoparticles. Meanwhile the existence of silver nanoparticles in silk-fibroin was proved by resonance scattering spectra.

[Degradation dynamics of POPs atrazine in soils under long-term located fertilization conditions].

To evaluate the difference of POPs atrazine degradation dynamics in soils under different fertilization conditions, we set up an analysis method of the atrazine residue in soils and studied residue dynamics of atrazine in soils under a long-term located fertilization conditions. After extracted by surging with acetone, liquid-liquid partition and eluted through florisil, the residue of atrazine in soils was detected by gas chromatogram with 63Ni-ECD. The minimum detectable quantity of atrazine is 6.4 x 10(-12) g and the minimum detectable concentration is 6.4 x 10(-9) g x kg(-1) in the soil. The spiked recoveries of atrazine with the three concentration of 0.11, 1.1, 11.0 mg x kg(-1) in soils are 91.41% +/- 4.36%, 93.58% +/- 4.54%, 90.35% +/- 3.59%, according with the request of pesticide residue analysis. The degradation of atrazine in soil under a long-term located fertilization conditions was studied. The results show the degradation of atrazine follows stair dynamic equation, and the degradation half-life of atrazine in soils fertilized with CK, NPK, NPK + M, NPK + S are 20.6, 23.0, 28.5, 33.2 d, respectively. Subjected to analysis of LSR, NPK and organic fertilizers are obviously propitious to the degradation of atrazine. The separate regression and stepwise regression analysis prove the degradation half-life of atrazine in soils is well related with the content of alkaline nitrogen, organic matter and total nitrogen, and the coefficients are 0.9983, 0.9826 and 0.9521, respectively. Maybe the reason is that these soil nutrient substance offers enough the element carbon and nitrogen for action of microbe, and the higher action of microbe quickens the degradation of atrazine in soils.

[Isolation and degrading characters of chlorpyrifos degrading bacteria XZ-3].

A strain of bacterium XZ-3 capable of highly degrading chlorpyrifos was screened from the soil sample collected from a pesticide plant after taming and enrichment. Based on analysis of phenotype, physiological and biochemical characters and 16S rDNA, XZ-3 was identified as Arthrobacter sp.. The effects of carbon source, pH, temperature and chlorpyrifos concentration on degradation were determined. The growth of bacteria in culture media were measured by visible absorption spectrophotometry under 400 nm. The residual chlorpyrifos in culture media was extracted with an equal volume of petroleum ether, and then determined by ultra-violet spectrophotometry. The results showed that the degradation rate of chlorpyrifos by XZ-3 was 86.8% in 24 h. The biodegradation rates were the highest when the additional carbon source was 0.3%, pH value was 9, chlorpyrifos concentration was 100 mg x L(-1), and cultivated temperature was 30 degrees C. The growth of bacteria increased with carbon source concentration, and was higher with pH from 8.0 to 10.0, and the highest when temperature was 30 degrees C, and chlorpyrifos concentration was 800 mg x L(-1). The strain could survive when chlorpyrifos concentration was 1000 mg x L(-1) and the removed amount of chlorpyrifos increased with chlorpyrifos concentration. The optimal conditions were proposed, which could provide theoretic basis for prevention and control of pesticides pollution.

[Isolation and degrading characters of pendimethalin degrading bacteria].

Microbial degradation of pendimethalin and the effects of culture conditions in vitro are studied. Twenty-nine strains are isolated by enrichment from soil and sludge. 3 strains can degrade more than 80% of pendimethalin of 100 mg x L(-l) in 3 days in culture fluid. 2 bacteria are considered as efficiently degrading strains identified as Pseudomonas, Mirococcus luteus. The efficiency of degradation is affected by culture conditions such as pH, temperature and the concentration of sucrose and pendimethanlin. The optimal conditions are proposed.

[Enzymatic degradation of organophosphorus insecticide chlorpyrifos by fungus WZ-I].

Degradation characteristics of chlorpyrifos insecticides was determined by the crude enzyme extracted from the isolated strain WZ-I ( Fusarium LK. ex Fx). The best separating condition and the degrading characteristic of chlorpyrifos were studied. Rate of degradation for chlorpyrifos by its intracellular enzyme, extracellular enzyme and cell fragment was 60.8%, 11.3% and 48%, respectively. The degrading enzyme was extracted after this fungus was incubated for 8 generations in the condition of noninducement, and its enzymic activity lost less, the results show that this enzyme is an intracellular and connatural enzyme. The solubility protein of the crude enzyme was determined with Albumin (bovine serum) as standard protein and the solubility protein of the crude enzyme was 3.36 mg x mL(-1). The pH optimum for crude enzyme was 6.8 for enzymatic degradation of chlorpyrifos, and it had comparatively high activity in the range of pH 6.0 - 9.0. The optimum temperature for enzymatic activity was at 40 degrees C, it still had comparatively high activity in the range of temperature 20-50 degrees C, the activity of enzyme rapidly reduced at 55 degrees C, its activity was 41% of the maximal activity. The crude enzyme showed Km value for chlorpyrifos of 1.049 26 mmol x L(-1), and the maximal enzymatic degradation rate was 0.253 5 micromol x (mg x min)(-1). Additional experimental evidence suggests that the enzyme had the stability of endure for temperature and pH, the crude enzyme of fungus WZ-I could effectively degrade chlorpyrifos.