DE2358953C3 - Process for the treatment of plants with water-soluble complex compounds to limit their content of harmful heavy metals, in particular lead - Google Patents

Description

The invention relates to a method for treating plants during their growth Keeping out and removing harmful heavy metals, especially lead.

Caused by the concentration process of human society and all areas of life (Production: industry, agriculture; trade and commerce; consumption: housing, transport) are among others. the Heavy metals distributed primarily to a harmless extent on earth in the soil, in the water and in the atmosphere is enriched in such amounts that it affects the health of plants, animals and humans threaten. This environmental problem is particularly topical at the moment with lead, mercury, cadmium and zinc, where in terms of quantity the lead plays the biggest role: Due to the high lead content of the gasoline and the Lead precipitation is currently the intensity of motor vehicle traffic in the FRG alone at around 40,000 Tonnes / year to be estimated (report »Lead and Environment« of the Commission for Environmental Hazards of Federal Health Office, Lead Working Group, 1972, p. 38). In addition there is the lead of industrial exhaust gases, especially the lead and zinc smelters. This lead from automobile and industrial exhaust fumes first and foremost down on the plants which, as far as useful plants are concerned, humans and animals as food or Serve feed. By feeding such lead-containing feed, it was already closed in 1972 in Nordenham numerous deaths have occurred in cattle (Die Naturwissenschaften, 60, 1973, p. 161). A corresponding The lead content of small children in this area already experienced an increase and required medical care Measures. Heavily industrialized and highly developed countries in terms of transport technology, like something that Western Europe, North America or Japan are at risk of heavy metal contamination of large parts of their long-term economic areas are directly affected.

It is therefore important and in many cases already indispensable that plants that are human or fed into animal nutrition are protected from the absorption of harmful heavy metals. Natural rain or washing with normal water is not enough for this, as heavy metals are very are firmly adsorbed on the plant surface or have already been incorporated into the interior of the plant.

The first efforts in this direction have already been made by developing a method for Treatment of soil to fix harmful metals in it (German patent specification 2240 733, 1973). This procedure takes into account but not that through direct atmospheric contamination of the plants with harmful heavy metals - as is the case with the lead of car and industrial exhaust fumes - these people and animals can be harmful to health when consumed. In such cases, treatment of the Ground ineffective.

The main aim of the invention is accordingly a method for treating plants that are on the one hand allows to plant before the ingestion of lead and other harmful heavy metals (e.g. zinc, cadmium, mercury, copper, nickel, iron, Cobalt, manganese) for the most part, but on the other hand it is also permitted, already with lead and others to remove harmful heavy metals from contaminated plants.

The method for treating plants developed for this purpose is set out in the claims marked Taking into account their large-scale production, which is already taking place and their extremely favorable chemical affinity for heavy metals on the other hand, are suitable for this purpose according to the invention, particularly water-soluble solutions

Salts of ethylenediaminetetraacetic acid (ÄDTE) and oligo- or polyphosphoric acid and mixtures the same. The salts of ethylenediamine tefriacetic acid correspond to the general formula a):

COOH
CH ₂

COOH

CH ₁
N-CH ₂ -CH ₂ -N

CH ₂
COOH

CH ₂
COOH

the hydrogen (H) in at least one of the four carboxyl groups (—COOH) being replaced by an ammonium, alkali, alkaline earth or other metal ion;
b) the salts of oligo- and polyphosphoric acid:

OH

HO-P-O-P-O-P-OH

OH

"OH

where at least one of the hydroxyl groups (-OH) has the hydrogen (H) replaced by an ammonium, Alkali, alkaline earth or other metal ion is replaced.

Investigations by the inventor have shown that the above-specified derivatives of Äthylendiamintetraes-

Acetic acid and oligo- or olyphosphoric acid are able to convert with harmful heavy metal ions - for example lead - on the plant surface, i.e. on the leaf and in the area of the roots, into a chelate form that the plant can hardly absorb. In contrast to the normal heavy metal complex, this heavy metal complex can now be washed off the surface of the plant very easily by rain or, during technical processing, can be effectively removed by normal washing with water. Since the affinity of other heavy metals to the above-mentioned chelators - the decadic logarithm of the stability constant pK serves as a measure - is similar to that of lead, in most cases even more favorable (for example for ethylenediaminetetraacetic acid: Pb: 18.2; Fe ¹¹¹ : 25.1; Hg : 21.8; Ni: 18.4; Cu: "183; Cd: 16.4; Zn: 16.1; Co: 16.1; Fe": 14.5; Mn: 13.4; according to Martell and Calyi η: Die Chemie der Mßiall-Chelatverbindungen. Verlag Chemie GmbH, Weinheim / Bergstr., 1958, p. 491), the results obtained with lead can generally be applied scientifically to the heavy metals mentioned above. By treating the plants in the field according to this method according to the invention, it has been demonstrated that - when carried out correctly - there is no loss in the absorption of important nutrients (e.g. potassium or phosphorus) or even in the amount harvested.

i) The advantages that can be achieved with the invention are therefore based on the fact that the crops grown in the area of high heavy metal emissions can conceivably be fed to animal or human nutrition, in the case of lead also the crops grown in the immediate vicinity of the roads and lead-emitting industrial plants.

The derivatives of ethylenediaminetetraacetic acid and the oligo-Z-polyphosphoric acid can according to the Invention can be applied in several ways:

For example, by spraying the compounds onto the plants in the form of aqueous solutions or together with fertilizers or pesticides also dissolved in it using commercially available spraying and spraying devices and sprinkling systems. Thanks to the heat stability of the connections is also a direct introduction of the corresponding aqueous solutions into the exhaust system is possible (hot mist process) - for example in the case of lead in the exhaust system of motor vehicles - which is the cause the heavy metal emissions are used for the heavy metal detoxification of plant-based foods would (polluter pays principle).

Health concerns on the part of the derivatives of ethylenediaminetetraacetic acid are unnecessary if one takes into account that these are used in medicine to remove the lead from the bones remove (Martell and Calvin: The Chemistry of Metal chelate compounds. Verlag Chemie GmbH, Weinheim / Bergstr, 1958, p. 457; Th. B e r s i η: Biochemistry of mineral and trace elements. Academic Verlagsgesellschaft, Frankfurt am Main, 1963, p. 422) or very high doses (4000 mg Ca-ADD / kg live weight) do not cause any damage to health (Cοmarund Wassermann: Biological Sciences, Vol. 1, Pergamon Press LTD, 1956, p 161). - What As for the polyphosphates, health concerns should be allayed if one takes into account that this in the food production z. B. on purpose the processed cheese and sausage be added to increase their water content (Th. Bersiη: Biochemie der Mineral- und Traceelemente. Akademische Verlagsgesellschaft, Frankfurt am Main, 1963, p, 367),

The amount to be used in the context of the invention can be complexed depending on the type and amount of to Removing heavy metal ions vary over a wide range: In the case of ethylenediaminetetraacetic acid, amounts up to 5 mol per Metal ion equivalents of the heavy metal ions to be removed preferred As the maximum that is still acceptable Concentration apply 5 millimoi / liter spray or Washing solution, - The salts of oligo-y-polyphosphoric acid, on the other hand, can be used in the mentioned spray or Find washing solutions up to a maximum concentration of 1% (= 10,000 ppm).

The following are examples to illustrate the invention where the lead content of the plants is given in ppm (based on dry weight). The lead in the Plants were identified in three ways:

1. Colorimetrically with dithizone according to W.Oelschläger and E. Schwarz: Determination of lead in biological substances. Z. Anal. Chenu 258, "No. 3, 1972, pp. 203-207 (Springer-Verlag).

2. By atomic absorption according to W. Oelschläger and E. Frenkel: determination of lead in vegetable and animal materials as well as in mineral feed with the help of atomic absorption spectrophotometry. Z. Agricultural research, z. Currently in print.

3. Radiometric with Pb-210 (scintillation spectrometry) according to A. Suchodoller: Investigations on the lead content of plants near roads and on uptake and translocation of lead from plants. Ber. Switzerland. Bot. Ges, 77, pp. 266-308.

1. Examples 1 -3 with salts of ethylenediaminetetraacetic acid

example 1

Influence of the disodium salt of ethylenediaminetetraacetic acid (Na ₂ ADTE) on the lead content of ryegrass which has been sprayed with lead nitrate:

In special rearing vessels (Mitscherlich vessels), ryegrass (Lolium perenne ^{) was sprayed with lead nitrate (10 ~ 4} mol Pb (NO ₃ ) ₂ / liter) twice daily in a sand / earth mixture outdoors for 3 weeks (control). To limit the lead uptake of the grass, a corresponding variant was additionally _{sprayed with Na 2} ADTE (IO- ³ mol / liter), which can be represented with the following formula:

COONa COONa

CH ₂ CH ₂

N-CH ₂ -CH ₂ -N CH ₂ CH ₂

COOH COOH

The precipitation during the experiment was 97 mm. - In order to show that the lead can also be _{removed later with Na 2} ADTE, the grass was analyzed a) immediately for lead in both cases, b) beforehand with water or c) with a Na ₂ ADTE solution (10 - ³ mol / liter) washed off for 15 min. The lead content of the grass was determined colorimetrically. The results obtained are summarized in Table 1:

Table 2 Table 1

Washing up with

Lead content (ppm) of
Ryegrass after spraying

only Pb (NO ₃ ) ₂
(Control)

Pb (NOj) ₂
+ Na ₂ ADTE

a) - 693

b) water 583

c) Na ₂ ADTE 178

Dry matter
(g / pot)

156
165
136

8.5 8.3

Example 2

Influence of CaADTE on the lead content of Ryegrass, which for 3 weeks the leaded vehicle exhaust gases on the Charlottenplatz in Stuttgart was exposed:

For 3 weeks, ryegrass was exposed to leaded vehicle exhaust gases on one of the busiest locations in Germany - Charlottenplatz in Stuttgart. The control was sprayed with water once a day, the corresponding variant, on the other hand, to limit the lead uptake of the grass with CaÄDTE (ΙΟ- ³ mol / liter), which can be expressed with the following formula:

COOH
ι COOH s ι
^l \ ί " ² I.
CH ₂ CH ₂ ooc N-CH ₂ -CH ₂ -N CH ₂ "" Approx COO

The precipitation during the experiment was 86 mm. - To show that the lead too can still be removed with CaÄDTE afterwards, in both cases the grass was a) up immediately Lead analyzed, b) beforehand with water or c) with a CaÄDTE-l.öSLing (IO 'mol / liter) for 15 min washed. The lead gchali of the grass was made by Atomic absorption determined. The results obtained are shown in Table 2.

Washing up with

Lead content (ppm) of
Ryegrass after spraying

water
(Control)

CAÄDTE

ίο a) -

b) water

c) CaÄDTE

Dry matter
(g / pot)

139
97
83

15.2

98
58
58

16.0

Tables 1 and 2 show:

1. that according to the invention by spraying with Na ₂ ADTE or with CaÄDTE, the lead content of the grass can be reduced considerably, namely in the 1st example from 693 to 156 ppm and in the 2nd example from 139 to 98 ppm,

2. with water

a) normally relatively little lead can be washed off, namely in the 1st example 693 opposite 583 ppm or in the 2nd example 139 compared to 97 ppm,

b) with prior spraying with Na ₂ ADTE or CaÄDTE, however, according to the invention, a great deal of lead can be removed, namely in the 1st example 693 versus 165 ppm and in the 2nd example 139 versus 58 ppm,

3. by washing the grass with salt solutions of the ÄDTE after lead contamination can remove a great deal of lead, namely 693 in the 1st example compared to 178 ppm and in the 2nd example 139 compared to 83 ppm,

4. That neither spraying with Na ₂ ADTE (1st example) nor with CaÄDTE (2nd example) has a negative effect on the amount of grass harvested (dry matter) (8.5 versus 8.3 g / pot or 15.2 versus 16.0 g / pot).

Both in example 1 and in example 2, the sprayed-on lead or the lead of the car exhaust fumes was through

the simultaneously sprayed salts of ethylenediaminetetraacetic acid chelated and considerably stronger due to the precipitation or the washing water Dimensions washed off than is normally the case with lead

so done. In the same way, the salts become effective when added to the wash water.

Example 3

About the influence of the salts of Äthjlendiaminetetraacetic acid on the lead absorption of the plant roots and their absorption of important nutrients To check (for example potassium or phosphorus), the following experiment was carried out under controlled environmental conditions carried out in climatic chambers of the Department of Plant Nutrition at the University of Hohenheim:

10-day-old French beans (Phaseolus vulgaris) - popular model plants in agricultural research - were in a complete nutrient solution for 24 hours that also contained 10 moles of Pb (NÜ3) 2 per liter. In a corresponding manner, graduated amounts of NajÄDTE were added to the nutrient solution (0; 10 ^b ;

5 · 10- ^b ; l0- ⁵ ; 5 · ΙΟ "⁵;ΙΟ"⁴; 5 · ΙΟ " ⁴ mol / liter). After the end of the test period, the plants were radiometrically for lead (ppm). Potassium (ipm / mg dry matter)

Table 3

and phosphorus (ipm / mg dry matter) analyzed. The results obtained are summarized in Table 3.

Mineral content to- " the French beans 10 ⁵ 5 · 10 ~ ⁵ 10 " ⁴ 5 x 10 " The nutrient solution of the 0 5 x 10 " ⁶ Added roots Na ₂ ADTE (mol / l) 135 18th 3 4th 4th Lead (ppm) 176 107 93 126 127 113 89 Potassium (ipm / mg TS) 111 84 135 68 71 75 71 Phosphorus (ipm / mg TS) 78 90

From Table 3 it appears that according to the invention, equimolar (10- ⁵ mol / 1) and superequimolar amounts of NazÄDTE completely restrict the lead-receiving plant via the roots virtually, while the intake of essential nutrients such as potassium or phosphorus here , completely unaffected by this, continues as normal.

20th

II. Examples 4-6
with salts of oligo- / phosphoric acid

example

Influence of sodium polyphosphate (Graham's salt) on the lead content of ryegrass, which with Lead nitrate has been sprayed.

In special rearing vessels (Mitscherlich vessels), ryegrass (Lolium perenne) was sprayed in a sand / earth mixture outdoors for 3 weeks once a day with lead nitrate [10- "mol Pb (NO ₃ ) 2 / liter] (control) A corresponding variant was additionally provided with restriction of the lead uptake of the grass

Sodium polyphosphate (0.1% = 1000 ppm) sprayed. 35 -

which is reproduced with the following general formula- Wash down with can be practiced:

NaO-Ρ — Ο - Ρ — O

ONa

L- P-ONa

ONa J _n ONa

40 can be subsequently removed with sodium polyphosphate, in both cases the grass was a) analyzed immediately for lead, b) beforehand with water or c) with a sodium polyphosphate solution (0.1% 1000 ppm) for 15 min washed. The lead content of the grass was determined by atomic absorption. The results obtained are summarized in Table 4.

Tabel

Lead content (ppm) of ryegrass after spraying

only Pb (NO ₃ ) ₂ Pb (NO ₃ ) ₂ (control) + Na polyphosphate

η> 1

45

The precipitation during the experiment was 106 mm. - To show that the lead is still there

a) - 128 65

b) water 70 50

c) Na polyphosphate 62 41

Dry matter 17.2 19.2 (g / pot)

example

Influence of sodium polyphosphate on the lead content of ryegrass, which for 3 weeks was the lead content Motor vehicle exhaust fumes exposed on Charlottenplatz in Stuttgart

For 3 weeks, ryegrass was one of the busiest vehicle exhaust fumes containing lead Locations of the FRG - the Charlottenplatz in Stuttgart - exposed. The control was used once a day Sprayed with water, the corresponding variant, on the other hand, to limit the lead uptake of the grass Sodium polyphosphate (0.5% = 5000 ppm), its formula is reproduced in Example 4. The precipitation during the test was 82 mm. - To also to show that the lead can also be removed later with sodium polyphosphate also here in both cases the grass a) analyzed immediately for lead, b) beforehand with water or c) with a Sodium polyphosphate solution (0.1% = 1000 ppm) was washed off for 15 minutes. The lead content of Grass was determined by atomic absorption.

The results obtained are shown in Table 5.

Tabel

Washing up with

Lead content (ppm) of ryegrass after spraying

Water (control)

Na polyphosphate

a) - 119 78

b) water 121 79

c) Na polyphosphate 59 71

Dry matter 20.1 19.6

(g / pot)

Tables 4 and 5 show:

1. that according to the invention by spraying with sodium polyphosphate, the lead content of the Grass can be limited considerably, namely in the 4th example from 128 to 65 ppm or in the 5th example from 119 to 78 ppm,

2. with water

a) normally relatively little lead can be washed off, namely in the 4th example 128 opposite 70 ppm or in the 5th example only 119 compared to 121 ppm,

b) after previous spraying with sodium polyphosphate, however, according to the invention, a great deal Can remove lead, namely in the 4th example 128 compared to 50 ppm or in the 5th example 119 compared to 79 ppm,

3. by washing the grass after lead contamination with sodium polyphosphate solution can still remove a great deal of lead, namely 128 in the 4th example compared to 62 ppm or in the 5th example. Example 119 versus 59 ppm,

4. that by spraying the grass with sodium polyphosphate, the harvested amount of the grass (dry matter) neither in the 4th example (17.2 versus 19.2 g / pot) nor in the 5th example (20.1 versus 19.6 g / pot) is adversely affected.

Both in Example 4 and in Example 5, the sprayed-on lead or the lead of the automobile exhaust gases was through the at the same time sprayed on sodium polyphosphate is chelated and by the precipitate or by the Wash water is washed off to a much greater extent than is normally the case with lead. In the same way the sodium polyphosphate is effective when it is added to the wash water.

_{| 0} example 6

To check the influence of polyphosphates on the lead uptake of the plant roots, was the following experiment under controlled environmental conditions in climatic chambers of the department for Plant nutrition carried out by the University of Hohenheim:

10-day-old bush beans (Phaseolus vulgaris) - popular model plants in agricultural research - were for 24 hours in a complete nutrient solution in addition still 10 ^-5 mol Pb were included (NO3) 2 per liter. In a corresponding manner, graduated amounts of sodium polyphosphate were added to the nutrient solution (0; 5; 10; 25; 50 and 100 ppm). At the end of the test period, the plants were analyzed radiometrically for lead (ppm). The results obtained are summarized in Table 6.

Table 6

0 added to the nutrient solution of the roots

Sodium Polyphosphate (ppm) (control)

Lead content of French beans (ppm) 273

247

10

221

25th
165

50

125

Table 6 shows that, according to the invention, polyphosphates are able to greatly limit the lead uptake of plants via the roots (ultimately by ² Å), with concentrations of 100 ppm being found in the case of sodium polyphosphate prove optimal.

Claims (3)

Patent claims: 1. Method of treating plants with water-soluble complex compounds to limit their content in harmful heavy metals, especially lead, indicated by-. * da8. Plants threatened or already affected by harmful heavy metal ions with at least one of the water-soluble salts of ethylenediaminetetraacetic acid and / or ojigo- / Polyphosphoric acid can be sprayed on the cultivated area. 2. The method according to claim 1, characterized in that that the water-soluble salts of ethylenediamimetraacetic acid the sp / itzlösungen in an amount of up to 5 moles per equivalent weight of Metal ions to be removed, 'added up to a maximum concentration of 5 millimoles / liter will. 3. The method according to claim 1, characterized in that that the water-soluble salts of oligo- / polyphosphoric acid the spray or washing solutions be added in an amount of a maximum of 1%.