CN104111264A - Methods for quickly detecting content of heavy metal elements in rice and evaluating comprehensive pollution index of heavy metal elements - Google Patents

Abstract

The invention belongs to the field of food detection, and in particular relates to methods for quickly detecting the content of heavy metal elements in rice and evaluating a comprehensive pollution index of the heavy metal elements. The method for quickly detecting the content of the heavy metal elements in the rice comprises the following steps: (1) pretreating a sample; (2) quickly detecting the content of a cadmium element and the content of a lead element in the rice; (3) quickly detecting the content of an arsenic element and the content of a mercury element in the rice. The method for evaluating the comprehensive pollution index of the heavy metal elements in the rice comprises the following steps: (1) measuring the contents of the cadmium element, the lead element, the arsenic element and the mercury element in the sample according to the detection method; (2) calculating pollution factor values of all the elements; (3) constructing a hierarchical relation among all indexes according to the pollution factor values of all the elements, and determining weights of the indexes so as to obtain a comprehensive pollution factor value in the rice, thus obtaining the pollution level of the harmful heavy metals in the rice. The methods are simple and time-saving, and the pollution degree of the heavy metals in the rice can be quickly, comprehensively and objectively reflected.

Description

A kind of fast detecting paddy contents of heavy metal elements and evaluate the method for its comprehensive pollution indexes

Technical field

The invention belongs to food inspection field, be specifically related to a kind of fast detecting paddy contents of heavy metal elements and evaluate the method for its comprehensive pollution indexes.

Background technology

The Detection task about heavy metal element is received by domestic each testing agency, the lead that particularly grain hygienic standard specifies, cadmium, the detection of mercury and arsenic.In the time that checker is engaged in above-mentioned four ultimate analyses experiment, sample pretreatment process is more complicated loaded down with trivial details, accounts for the more than 70% of whole analytic process, and its treatment effect quality has determined the confidence level of test result.

Current, in paddy, Evaluation of Heavy Metals Pollution method generally adopts single-factor evaluation method.Due to the extent of injury difference of every heavy metal element in paddy to all kinds of crowds, single-factor evaluation method can not be reacted heavy metal pollution degree in paddy comprehensively.Based on the deficiencies in the prior art and shortcoming, this seminar has carried out the correlative study of the aspects such as paddy heavy metal fast detecting, and (agriculture brainstorm subject is assigned by Science and Technology Department of Guangdong Province: 1 Guangdong Province's rice monitoring heavy metal pollution and hazard assessment architectural study 2011 are checked and accepted; 2 Guangdong Province's good quality and high output rice qualities and monitoring heavy metal pollution research are checked and accepted for 2013).

Summary of the invention

The shortcoming that the object of the invention is to overcome prior art, with not enough, provides a kind of method of fast detecting paddy contents of heavy metal elements.

Another object of the present invention is to provide a kind of method of evaluating above-mentioned paddy heavy metal element comprehensive pollution indexes.

Object of the present invention realizes by following technical proposals:

A method for fast detecting paddy contents of heavy metal elements, comprises following concrete steps:

(1) sample pretreatment

Paddy removal of impurities shelling is pulverized and mixed, obtain coarse rice powder sample;

(2) cadmium element content and lead element content in Fast Measurement paddy

By carbonization 20min under 500 DEG C～600 DEG C conditions of the coarse rice powder sample in step (1), cooling rear taking-up charcoal ash, calculated weight is than (ratio that charcoal ash quality obtains divided by the quality of coarse rice powder sample), in hand-held X-fluorescence spectrometer, input weight compares numerical value, charcoal ash is packed in sample cup simultaneously, be pressed into sample, with hand-held X-fluorescence spectrometer irradiation 6min, instrument draws strength ratio and calculates cadmium element content and the lead element content in coarse rice powder;

(3) arsenic element content and mercury element content in Fast Measurement paddy

1. the weighing of sample pre-treatments, immersion

The coarse rice powder sample that 0.5g step (1) is prepared is placed in container, and adds 10mL red fuming nitric acid (RFNA) and 4 perchloric acid, adds a cover spill glass sheet, wet method digestion, reaction 3h;

2. the digestion of sample pre-treatments

Container is moved to anticorrosion electric hot plate hot digestion, and 100 DEG C keep 30min, allow it slowly smolder; Then be warming up to 170 DEG C～220 DEG C and keep 2h; In the time of the remaining 0.3mL of digestive juice volume, the white cigarette of can emerging, continues heating and continuous 3～5min, then adds 1mL deionized water and catches up with most acid, continue to be evaporated near dry, after shift out cooling; Shift and be settled in 10mL color comparison tube with deionized water, obtain sample solution;

3. measure arsenic element content and mercury element content

The salpeter solution that is 3% with massfraction is dilution and current-carrying liquid, dilution arsenic standard reserving solution and mercury standard reserving solution, the arsenic mercury hybrid standard concentration series of 5 concentration of preparation; NaOH taking massfraction as 0.2% and the massfraction potassium borohydride mixed liquor as 1% is as reductive agent, measure the light absorption value of arsenic and mercury normal concentration series by the atomic fluorescence spectrophotometer of arsenic mercury two pass light source simultaneously, draw calibration curve according to the concentration of arsenic and mercury normal concentration series and corresponding light absorption value thereof; Same method is measured the light absorption value of sample solution, according to calibration curve, calculates arsenic in sample and mercury element content;

The quality optimization of the charcoal ash described in step (2) is 0.07～0.08g;

The model of the hand-held X-fluorescence spectrometer described in step (2) is PORT-X200, and described hand-held X-fluorescence spectrometer is containing the built-in mensuration cadmium element calibration curve and the lead element calibration curve that carry, and curve is provided by instrument manufacturer;

The red fuming nitric acid (RFNA) of step (3) described in is 1. preferably the pure red fuming nitric acid (RFNA) of top grade;

The perchloric acid of step (3) described in is 1. preferably analyzes pure perchloric acid;

The concentration of the arsenic standard reserving solution of step (3) described in is 3. preferably 1000 μ g/mL;

The concentration of the mercury standard reserving solution of step (3) described in is 3. preferably 1000 μ g/mL;

In the arsenic mercury hybrid standard concentration series of 5 concentration of step (3) described in 3., the final concentration of arsenic element is respectively 2ng/mL, 4ng/mL, 6ng/mL, 8ng/mL, 10ng/mL;

In the arsenic mercury hybrid standard concentration series of 5 concentration of step (3) described in 3., the final concentration of mercury element is respectively 0.2ng/mL, 0.4ng/mL, 0.6ng/mL, 0.8ng/mL, 1ng/mL;

When step (3) is measured the light absorption value of arsenic mercury hybrid standard concentration series and sample solution by atomic fluorescence spectrophotometer in 3., the sample size of atomic fluorescence spectrophotometer is preferably 4～4.5mL;

A method for Fast Evaluation paddy heavy metal element comprehensive pollution indexes, comprises following steps:

(1), according to the method for above-mentioned fast detecting paddy contents of heavy metal elements, the content of cadmium element, lead element, arsenic element and mercury element in working sample, is designated as respectively C _cd, C _pb, C _asand C _hg;

(2) toxic heavy metal element pollution factor (P _cd, P _pb, P _asand P _hg) calculate by following formula:

$P_{\mathrm{Cd}}=\frac{C_{\mathrm{Cd}}}{S_{\mathrm{Cd}}},$ S _Cd＝0.2mg/Kg；

$P_{\mathrm{Pb}}=\frac{C_{\mathrm{Pb}}}{S_{\mathrm{Pb}}},$ S _Pb＝0.2mg/Kg；

$P_{\mathrm{As}}=\frac{C_{\mathrm{As}}}{S_{\mathrm{As}}},$ S _As＝0.2mg/Kg；

$P_{\mathrm{Hg}}=\frac{C_{\mathrm{Hg}}}{S_{\mathrm{Hg}}},$ S _Hg＝0.02mg/Kg；

Wherein, S _cd, S _pb, S _asand S _hgvalue is the limitation of current national Specification;

(3) in sample, heavy metal element comprehensive pollution factor I calculates by following formula:

$I=\sqrt{\frac{P_{i\left(\mathrm{Max}\right)}^2+{(1/3\mathrm{\Σ}{p}_i)}^2}{2}},$ Wherein i is Pb, Cd, As and Hg;

(4) comprehensive pollution factor risk assessment (in table 1) in paddy:

Comprehensive pollution factor risk assessment in table 1 paddy

The present invention has following advantage and effect with respect to prior art:

1, in paddy, brown rice is subject to cadmium, lead, and the pollution of mercury and arsenic harmful element, testing laboratory generally need to obtain content separately fast, and it is carried out to comprehensive hazard assessment.Utilize brown rice cadmium and lead element content in " X-fluorescence rays method " Accurate Determining paddy, avoided the nitty-gritty details of chemical analysis experiment, and the time that place is short widely analyzes;

2, the present invention is after the cadmium element and lead element content that obtain fast in brown rice, the conventional method that need to process respectively mercury and arsenic element before being different from, according to the difference of constant volume and extension rate, dexterously the mensuration concentration of poisonous metal in brown rice is dropped in the range of linearity of typical curve separately, just can utilize the atomic fluorescence spectrophotometer of arsenic mercury two pass light source to carry out examination with computer, obtain the content of arsenic and mercury simultaneously; Conventional pre-treating method accumulative total consuming time at least 10 hours, this method only need to be to the single treatment of sample, can obtain the content (Fig. 1) of 4 kinds of harmful elements within half working day;

3, in paddy, comprehensive pollution factor risk evaluating method is simply a kind of after the content that obtains 4 kinds of harmful elements in brown rice and effectively evaluating mode, according to Limit of Contamination table, very clear, fill up brown rice in current paddy and be subject to the blank of the integrated evaluating method of 4 kinds of element pollutions.

Brief description of the drawings

Fig. 1 is fast detecting paddy contents of heavy metal elements of the present invention and the schematic flow diagram of evaluating the method for its comprehensive pollution indexes.

Fig. 2 is different cadmium element content and Instrument measuring strength ratio correlativity curve map in embodiment 1.

Fig. 3 is different lead element content and Instrument measuring strength ratio correlativity curve map in embodiment 2.

Fig. 4 is sample weighing in embodiment 2, immersion process schematic flow diagram.

Fig. 5 is treatments of the sample method schematic flow diagram in embodiment 2.

The calibration curve of arsenic element assay in Fig. 6 embodiment 3.

The calibration curve of mercury element assay in Fig. 7 embodiment 3.

Embodiment

Below in conjunction with embodiment and accompanying drawing, the present invention is described in further detail, but embodiments of the present invention are not limited to this.

Cadmium element content in embodiment 1 Fast Measurement paddy

(1) sample pretreatment

Divide sample method according to grain, oil plant sample, grain samples is mixed, adopt bronze object formula sample spliter to separate 2Kg primary sample, divide successively step by step again sample, two parts of Duplicate Samples finally getting each 50g, Duplicate Samples is processed simultaneously, and sample is placed in to pallet, choose the impurity of inorganic or organic, get clean paddy and adopt hulling machine to shell into brown rice, brown rice is used without moisture loss whirlwind flour mill again and is pulverized, and is placed in sealing bag, mix, obtain coarse rice powder sample;

(2) cadmium element content in Fast Measurement paddy

Assay method: the coarse rice powder sample of getting in step (1) is placed in 500 DEG C～600 DEG C carbonization 20min of quartz ampoule, cooling rear taking-up charcoal ash, weigh charcoal ash quality, calculated weight is than (ratio that charcoal ash quality obtains divided by the quality of coarse rice powder sample), the numerical value of input weight ratio in instrument, charcoal ash packs in sample cup simultaneously, be pressed into sample, with hand-held X-fluorescence spectrometer (PORT-X200, NCS Testing Technology Co., Ltd.) irradiation 6min, instrument draws strength ratio, instrument measures the heavy metal cadmium constituent content in coarse rice powder according to built-in cadmium content calibration curve,

(3) correlativity, accuracy, repeatability, stability and detection limit analysis

1. dependence test

Weigh coarse rice powder sample and blank powder (not containing in theory the ground rice of cadmium element) that known heavy cadmium metal constituent content value is 0.90mg/Kg, allot heavy metal cadmium constituent content and be 0.045 to 0.90mg/Kg mixed powder, get 5 points, measure the strength ratio (reading from apparatus measures result) of mixed powder according to assay method step (2) Suo Shu, draw correlation curve, in table 2 and Fig. 2.

Table 2 cadmium element content dependence test result

2. accuracy test

The coarse rice powder of measuring " national standard material Hunan rice " (numbering GBW10045 cadmium element content value is 0.19 ± 0.02mg/Kg) and other known cadmium content according to assay method step (2) Suo Shu, the results are shown in Table 3;

Table 3 cadmium element content accuracy test result

3. reperformance test

According to 1. described assay method METHOD FOR CONTINUOUS DETERMINATION " national standard material Hunan rice " (numbering GBW10045 cadmium element content value is 0.19 ± 0.02mg/Kg) 12 times of step, testing result is in table 4;

Table 4 chromium constituent content reperformance test result

4. stability test

According to 1. described assay method METHOD FOR CONTINUOUS DETERMINATION " national standard material Hunan rice " (numbering GBW10045 cadmium element content value is 0.19 ± 0.02mg/Kg) 12 hours of step, namely use same sample within 12 hours, measured once every one hour, obtain altogether 13 data, testing result is in table 5.

Table 5 cadmium element stable content test result

5. detection limit evaluation

According to 1. described assay method METHOD FOR CONTINUOUS DETERMINATION blank sample 20 times of step, calculate the detection limit of this Instrument measuring cadmium element, in table 6.

The test record of table 6 cadmium element content detection limit

The present embodiment adopts x-ray fluorescence method to carry out five aspects such as correlativity, accuracy, repeatability, stability and detection limit to cadmium content mensuration in rice and evaluates, from data result, the requirement that when x-ray fluorescence method can meet the on-the-spot purchase of paddy, heavy metal cadmium content is measured, play rapid screening effect, instrument is easy to operate, and accuracy test result is satisfied.

Lead element content in embodiment 2 Fast Measurement paddy

Sample pretreatment and assay method are with reference to embodiment 1;

1. dependence test

(in paddy, the sample of high-load lead is difficult for obtaining to weigh the coarse rice powder sample that known heavy metallic lead content value is 0.30mg/Kg, only have at present the given value sample of 0.3mg/Kg) and blank powder (not containing in theory the ground rice of lead element), allot content of heavy metal lead and be 0.05 to 0.3mg/Kg mixed powder, get 4 points, measure the strength ratio (reading from apparatus measures result) of mixed powder according to assay method embodiment 1 step (2) Suo Shu, draw correlation curve, in table 7 and Fig. 3.

Table 7 lead element content dependence test record

2. accuracy test

The coarse rice powder of measuring " national standard material Sichuan rice " (numbering GBW10044 lead element content value is 0.09 ± 0.03mg/Kg) and other known lead content according to assay method embodiment 1 step (2) Suo Shu, the results are shown in Table 8;

Table 8 lead element content accuracy test result

3. reperformance test

According to assay method METHOD FOR CONTINUOUS DETERMINATION embodiment 1 step (2) Suo Shu " national standard material Sichuan rice " (numbering GBW10044 lead element content value be 0.09 ± 0.03mg/Kg) 12 times, testing result is in table 9.

Table 9 lead element content reperformance test result

4. stability test

According to assay method METHOD FOR CONTINUOUS DETERMINATION embodiment 1 step (2) Suo Shu " national standard material Sichuan rice " (numbering GBW10044 lead element content value be 0.09 ± 0.03mg/Kg) 12 hours, namely use same sample within 12 hours, measured once every one hour, count in and obtain altogether end to end 13 data, testing result is in table 10.

The test record of table 10 lead element stable content

5. detection limit evaluation

According to assay method METHOD FOR CONTINUOUS DETERMINATION blank sample embodiment 1 step (2) Suo Shu 20 times, calculate the detection limit of this Instrument measuring lead element, in table 11.

The test record of table 11 lead element content detection limit

The present embodiment adopts x-ray fluorescence method to carry out five aspects such as correlativity, accuracy, repeatability, stability and detection limit to lead element assay in rice and evaluates, from data result, the requirement that when x-ray fluorescence method can meet the on-the-spot purchase of paddy, heavy metal lead constituent content is measured, play rapid screening effect, instrument is easy to operate, and accuracy test result is satisfied.

Arsenic and mercury element content in embodiment 3 Fast Measurement paddy

1. the weighing of sample pre-treatments

Prepare " national standard material Hunan rice " (GBW10045 (GSB-23)) coarse rice powder sample according to embodiment 1; The coarse rice powder sample of getting 0.5g is placed in high shape small beaker, and adds red fuming nitric acid (RFNA) and 4 pure perchloric acid of analysis that 10mL top grade is pure, lid spill glass sheet, wet method digestion, reaction 3h (Fig. 4);

2. the digestion of sample pre-treatments (Fig. 5)

Beaker is moved to anticorrosion electric hot plate hot digestion, and temperature is controlled at 100 DEG C and keeps half an hour, allows it slowly smolder; Then be warming up to 220 DEG C and keep 2h; In the time of the approximately remaining 0.3mL of digestive juice volume, the white cigarette of can emerging, continues heating and continuous 4min, then adds 1mL deionized water and catches up with most acid, continue to be evaporated near dry, after shift out cooling; Shift and be settled in 10mL color comparison tube with deionized water, obtain sample solution;

3. utilize the atomic fluorescence spectrophotometer of arsenic mercury two pass light source to measure arsenic element and mercury element content

The salpeter solution that is 3% with massfraction is dilution and current-carrying liquid, dilute arsenic standard reserving solution and the mercury standard reserving solution of 1000 μ g/mL, preparation arsenic element series of targets is the arsenic mercury hybrid standard concentration series of 2ng/mL, 4ng/mL, 6ng/mL, 8ng/mL, 10ng/mL and mercury element 0.2ng/mL, 0.4ng/mL, 0.6ng/mL, 0.8ng/mL, each 5 concentration point of 1ng/mL; NaOH taking massfraction as 0.2% and the massfraction potassium borohydride mixed liquor as 1% is as reductive agent, measure the light absorption value of arsenic and mercury normal concentration series by the atomic fluorescence spectrophotometer of arsenic mercury two pass light source simultaneously, sample size is 4.5mL, deduction reagent blank; Draw calibration curve (Fig. 6 and Fig. 7) according to the concentration of arsenic and mercury standard series and corresponding light absorption value thereof, measure the light absorption value of sample solution, according to calibration curve, calculate arsenic in sample and mercury element content; The results are shown in Table 12 to 14.

Table 12 arsenic normal concentration series samples light absorption value and arsenic element content thereof (the blank fluorescent value 106.21 of current-carrying)

Table 13 mercury normal concentration series samples light absorption value and total mercury constituent content thereof (the blank fluorescent value 67.64 of current-carrying)

The recovery of standard addition test result of table 14 " national standard material Hunan rice " (GBW10045 (GSB-23)) arsenic element content and mercury element content

Element

Standard substance certificate

The content that utilizes this method to record

The method recovery/%

?	Content (mg/Kg)	?	?
				Hg	0.0028±0.0005	0.0025	89.3
As	0.11±0.02	0.10	90.9

The method of embodiment 4 Fast Evaluation paddy heavy metal element comprehensive pollution indexes

(1) sample pretreatment

Fetch from the unknown sample in the place of production, Shaoguan City of Guangdong Province and divide sample method according to grain, oil plant sample, grain samples is mixed, adopt bronze object formula sample spliter to separate 2Kg primary sample, divide successively step by step again sample, finally get two parts of Duplicate Samples of each 50g, Duplicate Samples is processed simultaneously, sample is placed in to pallet, choose the impurity of inorganic or organic, get clean paddy and adopt hulling machine to shell into brown rice, brown rice is used without moisture loss whirlwind flour mill again and is pulverized, and is placed in sealing bag, mix, obtain coarse rice powder sample;

(2) cadmium element content and lead element content in Fast Measurement paddy

Get respectively 4.264g mixed powder A and 4.012g coarse rice powder sample (two parts of parallel sample 1 and 2) and detect cadmium and plumbous content, wherein two parts of parallel sample 1 and 2 cadmium content C in sample according to the method in embodiment 1 _cd1and C _cd2be respectively 0.054mg/Kg, 0.058mg/Kg, in table 15; Two parts of parallel sample 1 and 2 lead content C _pb1and C _pbbe respectively 0.086mg/Kg, 0.089mg/Kg, in table 16.

Table 15 utilizes intensity rate and the Cd content thereof of hand-held X-fluorescence spectrophotometer sample

Table 16 utilizes intensity rate and the lead content thereof of hand-held X-fluorescence spectrophotometer sample

(3) arsenic element and mercury element content in Fast Measurement paddy

Detect respectively arsenic element content and mercury element content in paddy (two parts of parallel sample 3 and 4) according to the method in embodiment 2, the results are shown in Table 17, table 18, wherein two parts of parallel sample 3 and 4 arsenic element content C _as1and C _as2be respectively 0.068mg/Kg, 0.073mg/Kg; Mercury element content P _hg1and P _hg2) be respectively 0.0023mg/kg, 0.0022mg/kg.

Table 17 sample light absorption value and arsenic element content thereof (the blank fluorescent value 106.21 of current-carrying)

Table 18 sample light absorption value and mercury content content thereof (the blank fluorescent value 67.64 of current-carrying)

(4) toxic heavy metal element pollution factor (P _cd, P _pb, P _asand P _hg) calculate by following formula:

s _cd=0.2mg/Kg, P _cd1=0.27, P _cd2=0.29, mean value 0.28;

s _pb=0.2mg/Kg, P _pb1=0.43, P _pb2=0.445, mean value 0.4375; (maximum)

s _as=0.2mg/Kg, P _as1=0.0.34, P _as2=0.365, mean value 0.3525;

s _hg=0.02mg/Kg, P _hg1=0.115, P _hg2=0.0.11, mean value 0.1125;

(5) in sample, heavy metal comprehensive pollution factor I calculates by following formula:

$I=\sqrt{\frac{P_{i\left(\mathrm{Max}\right)}^2+{(1/3\mathrm{\Σ}{p}_i)}^2}{2}}=\sqrt{\frac{{0.4375}^2+{(1/3(0.28+0.3525+0.1125))}^2}{2}}=0.3556$

(8) comprehensive pollution factor risk assessment in paddy, according to table 1, this duplicate samples heavy metal pollution is in unpolluted level.

Above-described embodiment is preferably embodiment of the present invention; but embodiments of the present invention are not restricted to the described embodiments; other any do not deviate from change, the modification done under Spirit Essence of the present invention and principle, substitutes, combination, simplify; all should be equivalent substitute mode, within being included in protection scope of the present invention.

Claims (9)

1. a method for fast detecting paddy contents of heavy metal elements, is characterized in that comprising following concrete steps:

(1) sample pretreatment

Paddy removal of impurities shelling is pulverized and mixed, obtain coarse rice powder sample;

(2) cadmium element content and lead element content in Fast Measurement paddy

By carbonization 20min under 500 DEG C～600 DEG C conditions of the coarse rice powder sample in step (1), cooling rear taking-up charcoal ash, calculated weight ratio, in hand-held X-fluorescence spectrometer, input weight compares numerical value, charcoal ash is packed in sample cup simultaneously, be pressed into sample, with hand-held X-fluorescence spectrometer irradiation 6min, instrument draws strength ratio and calculates cadmium element content and the lead element content in coarse rice powder;

(3) arsenic element content and mercury element content in Fast Measurement paddy

1. the weighing of sample pre-treatments, immersion

The coarse rice powder sample that 0.5g step (1) is prepared is placed in container, and adds 10mL red fuming nitric acid (RFNA) and 4 perchloric acid, adds a cover spill glass sheet, wet method digestion, reaction 3h;

2. the digestion of sample pre-treatments

Container is moved to anticorrosion electric hot plate hot digestion, and 100 DEG C keep 30min, allow it slowly smolder; Then be warming up to 170 DEG C～220 DEG C and keep 2h; In the time of the remaining 0.3mL of digestive juice volume, the white cigarette of can emerging, continues heating and continuous 3～5min, then adds 1mL deionized water and catches up with most acid, continue to be evaporated near dry, after shift out cooling; Shift and be settled in 10mL color comparison tube with deionized water, obtain sample solution;

3. measure arsenic element and mercury element content

The salpeter solution that is 3% with massfraction is dilution and current-carrying liquid, dilution arsenic standard reserving solution and mercury standard reserving solution, the arsenic mercury hybrid standard concentration series of 5 concentration of preparation; NaOH taking massfraction as 0.2% and the massfraction potassium borohydride mixed liquor as 1% is as reductive agent, measure the light absorption value of arsenic and mercury normal concentration series by the atomic fluorescence spectrophotometer of arsenic mercury two pass light source simultaneously, draw calibration curve according to the concentration of arsenic and mercury normal concentration series and corresponding light absorption value thereof; Same method is measured the light absorption value of sample solution, according to calibration curve, calculates arsenic in sample and mercury element content.

2. the method for fast detecting paddy contents of heavy metal elements according to claim 1, is characterized in that:

Described in step (2), the weight of charcoal ash is 0.07～0.08g.

3. the method for fast detecting paddy contents of heavy metal elements according to claim 1, is characterized in that:

The model of the hand-held X-fluorescence spectrometer described in step (2) is PORT-X200, and described hand-held X-fluorescence spectrometer is containing the built-in mensuration cadmium element calibration curve and the lead element calibration curve that carry.

4. the method for fast detecting paddy contents of heavy metal elements according to claim 1, is characterized in that:

The concentration of the arsenic standard reserving solution of step (3) described in is 3. 1000 μ g/mL.

5. the method for fast detecting paddy contents of heavy metal elements according to claim 1, is characterized in that:

The concentration of the mercury standard reserving solution of step (3) described in is 3. 1000 μ g/mL.

6. the method for fast detecting paddy contents of heavy metal elements according to claim 1, is characterized in that:

In the arsenic mercury hybrid standard concentration series of 5 concentration of step (3) described in 3., the final concentration of arsenic element is respectively 2ng/mL, 4ng/mL, 6ng/mL, 8ng/mL, 10ng/mL.

7. the method for fast detecting paddy contents of heavy metal elements according to claim 1, is characterized in that:

In the arsenic mercury hybrid standard concentration series of 5 concentration of step (3) described in 3., the final concentration of mercury element is respectively 0.2ng/mL, 0.4ng/mL, 0.6ng/mL, 0.8ng/mL, 1ng/mL.

8. the method for fast detecting paddy contents of heavy metal elements according to claim 1, is characterized in that:

When step (3) is measured the light absorption value of arsenic mercury hybrid standard concentration series and sample solution by atomic fluorescence spectrophotometer in 3., the sample size of atomic fluorescence spectrophotometer is 4～4.5mL.

9. a method for Fast Evaluation paddy heavy metal element comprehensive pollution indexes, comprises following steps:

(1) according to the method for the fast detecting paddy contents of heavy metal elements described in claim 1～9 any one, the content of cadmium element, lead element, arsenic element and mercury element in working sample, is designated as respectively C _cd, C _pb, C _asand C _hg;

(2) toxic heavy metal element pollution factor P _cd, P _pb, P _asand P _hgcalculate by following formula:

$P_{\mathrm{Cd}}=\frac{C_{\mathrm{Cd}}}{S_{\mathrm{Cd}}},$ S _Cd＝0.2mg/Kg；

$P_{\mathrm{Pb}}=\frac{C_{\mathrm{Pb}}}{S_{\mathrm{Pb}}},$ S _Pb＝0.2mg/Kg；

$P_{\mathrm{As}}=\frac{C_{\mathrm{As}}}{S_{\mathrm{As}}},$ S _As＝0.2mg/Kg；

$P_{\mathrm{Hg}}=\frac{C_{\mathrm{Hg}}}{S_{\mathrm{Hg}}},$ S _Hg＝0.02mg/Kg；

Wherein, S _cd, S _pb, S _asand S _hgvalue is the limitation of current national Specification;

(3) in sample, heavy metal element comprehensive pollution factor I calculates by following formula:

$I=\sqrt{\frac{P_{i\left(\mathrm{Max}\right)}^2+{(1/3\mathrm{\Σ}{p}_i)}^2}{2}},$ Wherein i is Pb, Cd, As and Hg.