發(fā)布時間：2016-09-28 06:31

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 ........... 20 
3.2 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).  

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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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參考文獻(xiàn)（略）

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