The Survey And Analysis Of The Arsenic Content Of The Growth Period And Environment Around Of The Three Economical Seaweeds

China is not only a main country that produces and consumes seaweeds but an important country which exports them in an enormous amount.Seaweed industry is an important and inseparable portion of the fishery economy in Chinese coastal area. So far,kelp,laver and Wakame are the main economic seaweeds in China,the annual output of kelp and Wakame are both the in the first position,and the annual amount of laver is only less than Japan and the South Korea around the world,and with the annual output still increasing.Rich in calcium,iron,phosphorus and iodine,etc., seaweed foodstuffs are health products and nutritious marine products.However, seaweeds may contain abundant metal ions,since their absorptive capacity to metal ions,such as iodine,lead,copper,arsenic,is much stronger than that to other creature. It should be added here that the arsenic content in seaweed foodstuffs is 42mg/kg～78mg/kg.Scholars home and abroad hold that the arsenic in seaweeds can be classified as organic arsenic and inorganic arsenic,with the latter occupying about 99%of the total arsenic content.And they also claim that seaweeds are harmless apart from sargassum fusiform.The incident of set standard-surpassing of arsenic content in 2006 has brought negative pressure to many companies,because most consumers have been doubting whether the seaweed foodstuffs are harmless or not.According to the present testing method GB/T5009.11-2003 the testing of the arsenic and inorganic arsenic in foodstuffs,there are two measures,namely hydride generation-atomic fluorescence spectrometry method(shortened as HG-AFS) and diethyl-dithiocarbamate method(shortened as DDC-Ag).Thorough the contrast of the aforementioned methods,it reveals that testing result obtained from the HG-AFS is much higher than that from the DDC-Ag,and the gap is 1.7～6 times,after the two methods are employed towards the same sample.Experiments reveal that suppose that the first method is utilized for pretreatment,that is to say,after the 18-hour water bath in water which is 60℃,then the difference of the testing result with the two methods respectively,is very obvious 1.85～3.33 times,suppose that the second method is utilized for treatment,that is to say,after the 1-hour water bath in water which is 70℃, then the two testing results are approximately the same 0.87-1.46 times.Therefore, the difference of the two pretreatments is a main factor that influences the testing results.The recovery rates of HG-AFS and DDC-Ag are 101.37%～110.59%and 100.47%～109.85%respectively,with their relative standard deviation less than 10% each.When HG-AFS is used to proceed and test the two inorganic arsenic MMA-Na and DMA-Na,it is discovered that these two organic arsenic would be erroneously tested as inorganic arsenic.Meanwhile,49.78%of MMA-Na,61.41%of DMA-Na would transform into inorganic arsenic after the 18-hour water bath in water which is 60℃.When DDC-Ag is used,54.03%of the MMA-Na,51.83%of the DMA-Na would transform into inorganic arsenic.Thus,the co-occurrence of the two methods in a criterion in GB/T5009.11-2003 the testing of the arsenic and inorganic arsenic in foodstuffs is not appropriate,as they are not feasible when they are applied to the seaweed foodstuffs with high content of arsenic.Next part of the this thesis focuses on the arsenic content of the growth period and the arsenic content of growth environment of the three economical seaweeds,and the analysis of the testing method of the inorganic arsenic in seaweeds-kelp,laver and Wakame.The experimental method is hydride generation-atomic fluorescence spectrometry in GB/T5009.11-2003 the testing of the arsenic and inorganic arsenic in foodstuffs,with the recovery rate and relative standard deviation being 98%～101% and less than 10%respectively.The result of the survey reveals that the total content of the arsenic content of kelp,Wakame and laver,is to some extent correlated with their growth period.The arsenic content varies in different part of the kelp,the arsenic content of the vertical-form is higher than that of the boundary part.To sum up,the root has the highest content of arsenic,the boundary part has the lowest content and the arsenic content of the vertical-form is in the middle.It is the same principle to the growth period of the Wakame,the total arsenic content of its stem is higher than that of its leaves.And this is related with the growth structure of the kelp and Wakame. Through their leaves,they absorb some essential nutrient elements such as nitrogen, calcium,phosphate and microelement(e.g.arsenic),which would be transformed into compounds of arsenic such as betaine of arsenic and arsenic sugar,after the synthesis, utilization and transformation in their body.Here,it should be noteworthy that for the Dalian high-row Wakame,the arsenic content of the leaves is higher than that of the stems.The arsenic content in seawater would increase as the growth period of the seaweeds extend.The total arsenic content in Dalian sea area and Qingdao sea area is in the range from 1.90μg/L to 5.00μg/L while the arsenic content in sea area of the Yantan development zone is in the range from 6.50μg/L to 10.00μg/L.It should be added here that in the three sea areas,as the growth period of kelp extends,the arsenic content tends to decrease.As for the kelp sample-gathering area,the arsenic content in seawaters would decrease in the following sequence which is listed in order,Yantan sea area,Qingdao sea area,Dalian sea area.