运用节杆菌株DNS10的阿特拉津生物修复与土壤微生物群落的推测
1 Introduction
In today's China, the rapid development of science and technology, the level of national living has improved significantly, in the field of agricultural science and technology has also made considerable progress. China is a large agricultural country, but also a country with a large population and a serious shortage of resources per capita. As the most basic material resources, food security and stable output is the basis and prerequisite for th e survival and development of a country. The invention and application of the pesticide can meet the basic requirement, and effectively improve the grain yield. However, most of the pesticides are toxic, and it is also a threat to human health and ecologic al environment in the loss of agricultural production, which brings more economic benefits. At present, reducing the harm of pesticides and reducing the use of pesticides has become a worldwide issue. 2011, the Ministry of agriculture in the national agricultural pest control work conference on the professional system, and strive to the end of 12th Five -Year will reduce the national pesticide usage by 20%. Black soil region of Northeast China is the main grain producing areas in China, and the problem of food production safety is becoming more and more important. Therefore, the selection of the herbicide atrazine is commonly used in black soils in Northeast China area as the research object and before carrying out research in understanding the basic charac teristics, the application, environmental damage and research progress. The northeast and North China area of our country the earliest use of a trazine, detecting information related to these areas show that the rivers, lakes, groundwater were atrazine and its metabolites such as the detection of EDA, DIA, and showed increasing trend reported by Shaner D L and Henry W B. 2007. During the 12th Five Year Plan period, the Ministry of agriculture to strengthen the management of pesticide abuse ( Nousiainen A O, et al. 2014). By the end of 2014, the most kinds of pesticides used year -on-year decline in the number and amount of growth started to slow down, but the amount of the herbicide in 2013 still increased by 2.8%. In recent years, with China's grain production increased year by year, improve the economic benefits of grain crops received more and more attention, however, because parts of the blind pursuit of food production, improve production efficiency, a large number of pesticides is not reasonable application. The abuse of chemical fertilizer, the unreasonable irrigation technology and so on, also increased the hazard of pesticide residue。
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2 Materials and Methods
2.1 Soil Sampling
Soil samples to see impact of soil pH and temperature were collected from topsoil (0 -20 cm) of northeast part of China having atrazine application history. All samples were shifted to laboratory and saved at 40C after sieving. Soil physical and chemical properties were determined to analyze soil quality. Soil organic carbon, total nitrogen, available nitrogen, potassium and phosphorus concentration was observed 25.7, 1.4, 0.1 8, 0.15, 1.2 g/kg respectively while soil pH was ranged between 6-7. Top soil (0-25 cm) sample was collected from the corn field of northeast region of China to make sure samples with atrazine application history to check bioremediation efficiency ovarioubioremediatin techniques. Then the sample was transferred to the laboratory immediately after checking out the plant cover of the soil. Soil was sieved and divided in two parts, one for determination of physical -chemical properties of the soil and other was preserved at 40C for further research. Soil was enriched with organic carbon (25 g/kg) while soil pH was observed between 6.5 -7. Soil total nitrogen, phorphorus , available nitrogen and potassium concentration was 1.4, 1.30, 0.131, 0.162 g/kg respectively.
2.2 Chemicals and different carbon, nitrogen sources:
Total 9 microcosms were primed as blank and 36 microcosms were prepared for 4 treatments (Sawdust, DNS10, Sodium Citrate, and Animal Manure) under different temperatures (20, 30, 400C) and pH (5, 7, and 9). Then, 20mg/kg of atrazine was applied in each of designed microcosm and kept in the fume hood for one day to stabilize soil conditions. After that 9 microcosms were categorized for each treatment including blank. Subsequently 0.2g/100g of animal manure, sawdust and sodium citrate and 1ml/100g of DNS10 was added in each of 9 relevant microcosms. All microcosms were incubated under selected parameters for 30 days and 10 g of soil sample was separated from each microcosm after 3, 7, 14 and 28 days to measure residual atrazine concentration. Each of treatments was run in triplets to reduce detection error. The normal application rate of atrazine was reported 0.5-2.5 kg/ha. However, the atrazine concentration 20mg/g of soil was related to 7.5 kg/ha. In this study 700 mg/lit of Atrazine was mixed with acetone. This solution was added in 1000 g of soil to get the final atrazine concentration 700mg/kg of soil. This much atrazine amount was selected to see the efficiency of selected material. Then, soil was kept in the fume hood for 24 hours to stabilize soil conditions. After 24 hours all treatments were prepared according to table 1. Sodium citrate, animal manure and sawdust were added to get the final concentration of 5 g/100g of soil respectively. Inoculation of arthrobacto sp. Strain DNS10 was 30ml/100 g of soil in each selected treatment. For proper bacterial functioning pH was maintained at 7 of each microcosm. All soil samples were kept at room temperature (30oC) throughout the experiment. 10 g of soil sample was removed from each microcosm after 3, 7, 14 and 28 days to measure remaining atrazine concentration. To minimize experimental error experiment was run in triplets.3 Results .............. 20
3.1 Residual atrazine under different parameters ........... 203.2 Atrazine removal percentage at different pH and temperatures .... 21
3.3 Temperature and pH significances on different bioremediation approaches ................ 22
3.4 Extractable atrazine concentration in different selected sources .......... 24
3.5 Atrazine degradation potential of different bioremediation strategies: ........ 25
3.6 Percentage of atrazine bioremediation for each microcosm: ................... 26
3.7 Correlation coefficient matrix for different bioremediation variables: ................ 28
3.8 PCR-DGGE Anlaysis ........... 30
4 Discussion .................. 32
4.1 Pesticide and herbicide contamination .............. 32
4.2 Atrazine contamination ......................... 32
4.3 Atrazine bioremediation ....................... 32
4.4 Effective Bioremediation Techniques .......... 33
4.5 Use of microbial strains in atrazine bioremediation ....... 34
4.6 Different carbon and nitrogen sources utilized in atrazine bioremediation .................. 35
4.7 Combined application of bioremediation treatments ................ 36
4.8 Consequences of recent study ..................... 37
4.9 Impact of soil pH and temperature on atrazine bioremediation ................................... 38
Conclusion ........................ 40
4 Discussion
4.1 Pesticide and herbicide contamination
Pesticides and herbicide contamination in agricultural soils and their leaching in water resources were considered as global issue. It was need of hour to remove potential hazard of these chemicals in soil and water without compromising on crop yield production (Kadian, Gupta et al. 2008). Different bioremediation and phytoremediation strategies were adopted for hazard reduction; which made chemical usages more beneficial and environment friendly (Ma 2014). Atrazine was an herbicide used to remove broadleaf grasses in corn, sugarcane and sorghum crops to enhance production as these fewer crops were resistant against suggested atrazine concentration (Xie, Wan et al. 2013).
4.2 Atrazine contamination
Atrazine was described as a major herbicide to control grassy and broad leaf weeds in maize crop production. This caused many endocrine disruptive and reproductive problems and reported as human carcinogen (Hayes T B, et al. 2006: Wackett L P, et al ,2002). Although, atrazine has less solubility, water pollution but due to its persistent in environment, it has become global issue (Martine-Laurent 2012). Biodegradation was reported main dissipation way for atazine, such as leaching (Newcombe DA 1999). Atrazine biodegaradation was limited due to adsoption and desorption process, also its bioavailability was critical in biodegradation. Many chemicals were being removed by using the bioremediation method. Bioremediation was further divided in two categories: bioaugmentation and biostimulation (Lima, Viana et al. 2009). In bioaugmentation, indigenous bacteria were used tacceler ate the contaminant degradation rate. For this purpose bacterial strains were isolated from locally polluted soil and used for bioremediation, reported in many studies (Crowley 1999; Komang Ralebitso, Senior et al. 2002). Dehghani and colleague verified in their study that atrazine biodegradation was more effective in soils with no previous history of herbicide application as compared to the soil exposed to the herbicides (Dehghani, Nasseri et al. 2013). So, atrazine application on soil was also considered as an important factor in atrazine biodegradation. So, atrazine application on these crops reduced their competition wit h unwanted herbs and shrubs for soil nutrients, sun energy and water requirements (Lima, Viana et al. 2009)........
Conclusion
This study was conducted to find that soil pH and temperature played a greater role in atrazine bio-remediation. Atrazine degradation was influenced at different set temperatures and pH in soil treated with no additional amendment. General trend of atrazine degradation was directly proportional with temperature; higher the temperature, higher the atr aine remediation rate but soil pH controlled atrazine removal rate at different temperatures. Soil treated with DNS10 and sawdust significantly removed atrazine with increase in temperature while atrazine degradation in soil amended with AM and SC was foun d pH dependant. Atrazine biodegradation was monitired by measuring extractable atrazine in soil. All designed treatments were incubated at same temperature. Soil pH and moisture wasmaintained to analyse degradation potential of each treatment. Study concluded that bioaugmentaion (Arthrobactor sp.strain DNS10) was more effective then Biostimulation (Animal Manure, Sawdust and Sodium Citrate). However, combined bioaugmentaion and biostimulation has higher atrazine degradation potential than single biore mediation strategy. Combination of two of nutrients (from animal manure, sawdust and sodium citrate) with bioaugmentaion caused increase in atrazine biormediation.
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参考文献（略）
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