N.N. Karpun (Cand. Biol. Sci.), E.B. Yanushevskaya (Cand. Biol. Sci.)

The State Research Institution All–Russian Scientific and Research Institute of Floriculture and Subtropical Crops of the Russian Academy of Agricultural Sciences

MONITORING PESTICIDES IMPLICATION BASED ON CHLORPYRIFOS, DIMETHOATE AND PHOSALONE IN AGROCENOSIS OF FRUIT CROPS IN SOUTHERN RUSSIA

The paper determined a complex of negative impacts from implication of pesticides based on chlorpyrifos (dursban, sairen), dimethoate (danadim, Bi-58, rogor) and phosalone (zolone). The level of soil contamination by pesticides after fruit crops treatment was within 3-5 MAC. The general biological activity of soil microbe cenosis was oppressed; substrate-induced respiration was intensively suppressed, and protective mechanisms were violated. Double use of these pesticides in the growing season increased their ecotoxicological impact reducing the intensity of recovery processes at the same time. Maximum toxic impact was recorded after application of pesticides on the basis of chlorpyrifos. When danadim, rogor and Bi-58 were used once, protective mechanisms state in soil microbe cenosis was not violated. Wide range of negative effects from pesticides application shows the usefulness of their monitoring in the main interrelated areas, which allow to evaluate the degree of environmental contamination, intensity of the impact on biological systems and the nature of responses in natural defense mechanisms.

Key words: pesticides, microbe cenosis, soil biological activity, soil contamination.

During the treatments of fruit agrocenosises significant part of pesticides comes into soil (40-60 % from application rates), which in some cases leads to its significant pollution exceeding MAC [6, 8, 11, 12]. However, this problem is not confined, as many pesticides have a depressing effect on soil biotic activity due to their high biological activity and marked toxic properties, reducing the intensity of metabolic processes [7, 10]. At the same time, resistance of natural defense mechanisms of soil biotic component decreases; they are basis of purification and recovery of microbe cenosis’s functions [3, 9, 13].

The purpose of this research is to monitor the chlorine- and organophosphorus based pesticides, taking into account three interrelated directions: determination of the degree of soil contamination with ecotoxicants, intensity of their impacts on the processes of soil self-purification and recovery of biological activity.

Monitoring of the negative impacts from pesticides application (dursban, sairen, zolone, danadim, Bi-58, rogor) was conducted from 2000 to 2010 in peach and tangerine plantations (experimental plots of the Russian Research Institute of Floriculture and Subtropical Crops). All the experimental plots were in the same agro landscape on brown forest slightly desaturated soils. Sanitary conditions of the upper soil horizon (0-20 cm) were evaluated by the content of the residual quantities of the active ingredients in the above mentioned preparations. The terms of insecticide treatments for peach and tangerine justified the need for protective measures against major pests in these crops. Soil samples were collected during the first 24 hours after the treatments. The degree in soil contamination was determined within the dynamics, which allowed to establish the duration of pesticides conservation and intensity of soil self-purification. The contents of chlorpyrifos – active ingredient of dursban and sairen; phosalone – active ingredient of zolone, and dimethoate – active ingredient of danadim, Bi-58 and rogor in soil were determined by gas-liquid chromatography method [4].

The nature of pesticides and soil biosystem interaction was in the basis of ecotoxicological monitoring and its criteria. Having a wide range of common toxicity they disrupt cell membranes of living organisms with subsequent destabilization of the basic metabolic processes and mechanisms of intracellular bioenergetics [1, 5]. At the same time, counteracting the negative effects from ecotoxicants, soil protection biosystems are focused on providing basic vital functions, including self-purification processes [2]. Aerobic microorganisms play a leading role in that aspect, having more sophisticated intracellular mechanisms, compared with anaerobic microbiota.

Based on years of research, we have developed a complex of diagnostic criteria, sensitive and adequately responding to pesticides load that was used during the monitoring [14]. Actual respiratory activity of soil microbe cenosis was determined, which is an integral criterion reflecting the intensity of soil metabolic processes. The level of the substrate-induced respiration (substrate – 5 % glucose solution), allowing to evaluate the potential of intracellular bioenergetical processes at pesticide loads. Additional criterion determining microbe cenosis resistance to xenobiotics’ impact is a microbial respiration coefficient (MRC), calculated by the following formula:

In order to establish pesticides effect on the natural ability of soil microbial communities to selfrecover their biological activity, impaired by ecotoxicants, the studied parameters were determined in the dynamics.

Long-term monitoring of pesticides implication that are based on chlorpyrifos (dursban, sairen) helped to establish the basic laws describing the impact of this toxic compound on the soil ecosystem. Its considerable amount was recorded in the soil two hours later after treatments for tangerine and peach – within 3-4 of MAC (0,6-0,8 mg/kg). This contamination level had a dampening effect on the overall biological activity in soil microbe cenosis accompanied by low intensity of soil self-purification. Severity and duration of chlorpyrifos negative impact were dependent on treatments multiplicity. The nature of responses from soil microbial communities to the toxicological effect was largely determined by treatments terms, which is apparently due to the seasonal activity of soil metabolic processes.

As follows from the data in Table 1, the treatment in early spring (March) resulted in inhibition of the actual respiratory activity in microbe cenosis up to 35,2 %. Chlorpyrifos had a more significant adverse impact on the substrate-induced respiration, therefore MRC was decreasing, reflecting the stability of soil biotic component to negative influences.

Such an essential disturbance in indicators of the general soil biological activity was accompanied by low-intensity processes of its purification from residual amounts of chlorpyrifos in spite of the fact that in spring there is a maximum degradation of soil microorganisms (Table 1).

Table 1

Overall biological activity of soil (% to control) and content of chlorpyrifos in soil (mg/kg) after treatment of tangerine and peach with sairen

Crop treatments dates	Indicators	First 24 hours after treatment	Time after treatment, months
			1	2	3	4	5	6
Tangerines 21.03.2006	Actual respiratory activity	64,8	75,2	74,8	82,3	81,6	95,4	96,7
	Substrate-induced respiration	44,9	52,3	74,5	79,1	89,2	102,3	104,5
	Content of chlorpyrifos in soil	–	0,55	0,21	0,18	0,02	Not found
Peach 28.04.2006	Actual respiratory activity	72,5	74,3	78,2	79,1	81,2	84,5	94,2
	Substrate-induced respiration	55,8	68,5	71,3	79,5	85,8	84,2	89,6
	Content of chlorpyrifos in soil	–	0,58	0,29	0,21	0,18	0,05	Not found
Tangerines 25.05.2008	Actual respiratory activity	75,2	78,2	76,3	75,4	79,1	84,1	85,5
	Substrate-induced respiration	67,3	71,2	68,3	72,4	78,5	80,5	81,2
	Content of chlorpyrifos in soil	–	0,48	0,27	0,23	0,18	0,07	0,02

Negative effects from chlorpyrifos increase after application of pesticides containing it at later time in the spring, especially in May. Since soil purification processes in the summer dry season (July and August) are suppressed, the time on chlorpyrifos decay increases. Its residual amount was detected even after 6 months of use. This also explains the increase in the duration of the recovery period and the lack of normalization in soil biological activity by the end of the observation periods (November).

Adverse effects of chlorpyrifos on fruit crops agrocenosises were substantially increased at double use of pesticides on its basis (Table 2).

After the reapplication of sairen, the negative effects preserved as a result of the first processing and during the second spraying were summed. Soil contamination increased up to 0,95 mg/kg, which is above the maximum value (on 0,15 mg/kg) that was recorded during the single use of preparation. Residual amounts of ecotoxicants retained in the soil for a long time and detected even after 6 months after application. Such a substantial content of chlorpyrifos in the soil had an extremely negative effect on the respiratory activity of microbe cenosis. One day after the second treatment, the inhibition of substrate-induced respiration made up 75,2 % of control values, and current respiratory activity – 58,2 %. MRC level, reflecting the stability of soil microbial community to stress factors decreased in 1,9 times compared to the control.

Table 2

Results of soils monitoring after double processing tangerine with sairen

Indicators	Time after treatment, months
	First treatment 15.03.07		Second treatment 17.05.07
	1	2	1	2	3	4	5	6
Content of chlorpyrifos in soil (mg/kl)	0,54	0,22	0,68	0,51	0,45	0,35	0,25	0,15
Actual respiratory activity (% to the control)	74,2	82,4	47,2	55,8	61,3	75,2	81,4	79,5
Substrate-induced respiration (% to the control)	61,5	79,5	28,7	35,4	42,5	51,2	65,3	74,6

A disturbance in recovery processes of microbe cenosis biological activity is the most dangerous for a double application of chlorpyrifos, which is due to the suppressed ecotoxicant. 12 months after the first treatment, and 10 months after the second one in March 2008, there was recorded no normalization of general biological activity despite the lack of residual amounts of chlorpyrifos in the soil. The oppression degree of actual respiratory activity was 19 %, and 21 % of control values for the substrate-induced respiration in microbe cenosis. The lower MRC level (2,82) compared to control (3,15) indicates the decrease of protective properties in soil microbiota. Thus, disruption of the microbe cenosis functional state caused by a double application of pesticides based on chlorpyrifos remained for a long time and even after its complete degradation in the soil.

According to the monitoring, after applying organophosphorus pesticides based on dimethoate (danadim, Bi-58, rogor), residual amounts of the active ingredients was within 5 MAC (Table 3).

Table 3

Results of soils monitoring after treatments of peach plantings with danadim (first treatment on 27.04.2004, the second treatment on 2.06.2004)

Indicators	Treatments	Time after treatment, 24 hours
		1	7	14	28	42	56
Content of dimethoate in soil (mg/kl)	first	0,55	0,35	0,15	0,11	Not found
	second	0,52	0,32	0,19	0,14	0,12	-
Actual respiratory activity (% to the control)	first	78,2	82,4	84,7	85,1	98,2	105,4
	second	69,4	71,2	76,2	79,8	82,4	95,8
Substrate-induced respiration (% to the control)	first	74,3	76,5	78,2	81,4	82,3	91,2
	second	66,5	69,4	71,2	75,8	78,9	82,3

The length of soil contamination depended on the multiplicity of pesticides use during the growing season. Residual amounts of dimethoate were detected in the soil for 1-1,5 months, which poses a threat to soil biotic component. After the first treatment of peach with danadim, the oppression of actual biological activity and substrate-induced respiration of soil microorganisms were recorded. These changes were accompanied by a decrease in MRC level, which indicates a violation of adaptive function in microbe cenosis. This conclusion is confirmed by the growth of ecotoxicological impact from dimethoate, which falls into the soil with repeated use, two months later after the first treatment. The intensity of respiration of the substrate-induced inhibition and the duration of recovery in microbe cenosis biological activity were increasing.

Similar results were obtained with rogor and Bi-58, their active ingredient is also dimethoate. Zolon had more negative effects on fruit crops agrocenosis (Table 4).

Table 4

Results of soils monitoring after treatments of tangerine plantings with zolon

(first treatment on 27.03.2004, second treatment on 3.06.2004)

Indicators	Treatments	Time after treatment, 24 hours
		1	7	14	28	56	85
Content of phosalone in soil (mg/kl)	first	0,59	0,48	0,35	0,21	0,09	Not found
	second	0,60	0,51	0,37	0,25	0,11	0,05
Actual respiratory activity (% to the control)	first	67,2	65,2	76,3	81,2	91,2	95,4
	second	59,0	61,7	65,2	71,2	74,5	94,5
Substrate-induced respiration (% to the control)	first	51,2	61,8	72,3	78,3	90,2	96,8
	second	45,9	43,4	57,3	68,9	87,3	94,2

Duration of preservation of its active substance (phosalone) in soil was higher compared to dimethoate, especially after repeated treatment. Complete purification of soil occurred in three months. Phosalone had a significant negative impact on the overall biological activity in the soil microbe cenosis. The depressing effect on the substrate-induced respiration was significant; its level was reduced by 48,8 % after the first treatment, while the actual respiratory activity decreased up to 32,8 %.

More pronounced inhibition of substrate-induced respiration compared with the actual change in respiratory activity is the basis of violations of bioenergetic processes, providing a protective function in soil microorganisms. This is confirmed not only by reducing MRC, but also by increase in phosalone ecotoxicological action after peach retreatment. The nature of the revealed violations was the same as described above after the second treatment with pesticides based on dimethoate. However, they had higher intensity. The second treatment of tangerine with zolone after the first one with dursban had extremely negative consequences. Soil contamination with two toxic substances after the treatment with zolone on the background of significant inhibition of total biological activity of early applied dursban led to a significant deterioration in the functional state of microbocenosis (Table 5).

Table 5

Results of monitoring tangerine soils

after treatment with dursban (15.03.2005) and zolone (17.05.2005)

Indicators	Time after treatment with zolone, months
	1	2	3	4	5	6
Content of chlorpyrifos in soil (mg/kl)	0,19	0,12	0,08	0,03	0,01	Not found
Content of dimethoate in soil (mg/kl)	0,32	0,22	0,09	0,05	0,02	0,01
Actual respiratory activity (% to the control)	55,0	47,2	64,3	78,5	88,2	95,4
Substrate-induced respiration (% to the control)	42,4	37,5	51,8	66,5	75,2	90,5

The indicators of substrate-induced respiration and MRC were most sensitive to the combined action of two ecotoxicants (chlorpyrifos and phosalone). The period of soil self-purification from residual amounts of these pesticides increased in 1.5-2 times.

Applying pesticides based on chlorpyrifos, dimethoate and phosalone significantly worsened sanitary condition and ecotoxicological state in peach and tangerine agrocenosises. Significant soil contamination at the level of 3-5 MAC led to the oppression of the total biological activity in microbocenosis. Suppression of the intensity of substrate-induced respiration was accompanied by violation of the protective mechanisms in soil microbial community. The negative effect was significantly increased after the re-use of pesticides. Minimum ecotoxic action was established within a single application of rogor, B-58 and danadim. The greatest danger to agrocenosis is represented by pesticides based on chlorpyrifos.

The obtained monitoring results indicate the need to limit the use of pesticides based on chlorpyrifos and fozolone in fruit crops agrotcenosises.

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