Soil Chemical Analysis

Summary 1. Neonicotinoids are now the most widely used insecticides in the world. They act systemically, travelling through plant tissues and protecting all parts of the crop, and are widely applied as seed dressings. As neurotoxins with high toxicity to most arthropods, they provide effective pest control and have numerous uses in arable farming and horticulture. 2. However, the prophylactic use of broad-spectrum pesticides goes against the long-established principles of integrated pest management (IPM), leading to environmental concerns. 3. It has recently emerged that neonicotinoids can persist and accumulate in soils. They are water soluble and prone to leaching into waterways. Being systemic, they are found in nectar and pollen of treated crops. Reported levels in soils, waterways, field margin plants and floral resources overlap substantially with concentrations that are sufficient to control pests in crops, and commonly exceed the LC50 (the concentration which kills 50% of individuals) for beneficial organisms. Concentrations in nectar and pollen in crops are sufficient to impact substantially on colony reproduction in bumblebees. 4. Although vertebrates are less susceptible than arthropods, consumption of small numbers of dressed seeds offers a route to direct mortality in birds and mammals. 5. Synthesis and applications. Major knowledge gaps remain, but current use of neonicotinoids is likely to be impacting on a broad range of non-target taxa including pollinators and soil and aquatic invertebrates and hence threatens a range of ecosystem services.

/pdf/review-an-overview-of-the-environmental-risks-posed-by-hj0ee8p6bs.pdf

REVIEW: An overview of the environmental risks posed by neonicotinoid insecticides

Exposure to pesticides and the associated human health effects

Systemic insecticides are applied to plants using a wide variety of methods, ranging from foliar sprays to seed treatments and soil drenches. Neonicotinoids and fipronil are among the most widely used pesticides in the world. Their popularity is largely due to their high toxicity to invertebrates, the ease and flexibility with which they can be applied, their long persistence, and their systemic nature, which ensures that they spread to all parts of the target crop. However, these properties also increase the probability of environmental contamination and exposure of nontarget organisms. Environmental contamination occurs via a number of routes including dust generated during drilling of dressed seeds, contamination and accumulation in arable soils and soil water, runoff into waterways, and uptake of pesticides by nontarget plants via their roots or dust deposition on leaves. Persistence in soils, waterways, and nontarget plants is variable but can be prolonged; for example, the half-lives of neonicotinoids in soils can exceed 1,000 days, so they can accumulate when used repeatedly. Similarly, they can persist in woody plants for periods exceeding 1 year. Breakdown results in toxic metabolites, though concentrations of these in the environment are rarely measured. Overall, there is strong evidence that soils, waterways, and plants in agricultural environments and neighboring areas are contaminated with variable levels of neonicotinoids or fipronil mixtures and their metabolites (soil, parts per billion (ppb)-parts per million (ppm) range; water, parts per trillion (ppt)-ppb range; and plants, ppb-ppm range). This provides multiple routes for chronic (and acute in some cases) exposure of nontarget animals. For example, pollinators are exposed through direct contact with dust during drilling; consumption of pollen, nectar, or guttation drops from seed-treated crops, water, and consumption of contaminated pollen and nectar from wild flowers and trees growing near-treated crops. Studies of food stores in honeybee colonies from across the globe demonstrate that colonies are routinely and chronically exposed to neonicotinoids, fipronil, and their metabolites (generally in the 1–100 ppb range), mixed with other pesticides some of which are known to act synergistically with neonicotinoids. Other nontarget organisms, particularly those inhabiting soils, aquatic habitats, or herbivorous insects feeding on noncrop plants in farmland, will also inevitably receive exposure, although data are generally lacking for these groups. We summarize the current state of knowledge regarding the environmental fate of these compounds by outlining what is known about the chemical properties of these compounds, and placing these properties in the context of modern agricultural practices.

/pdf/environmental-fate-and-exposure-neonicotinoids-and-fipronil-ln5a08bl9m.pdf

Environmental fate and exposure; neonicotinoids and fipronil

https://www.boerenlandvogels.nl/sites/default/files/Morrissey%20et%20al_2015_Neonicotinoid%20contamination%20of%20global%20surface%20water%20%20%20.pdf

Neonicotinoid contamination of global surface waters and associated risk to aquatic invertebrates: A review

The term pesticide covers a wide range of compounds including insecticides, fungicides, herbicides, rodenticides, molluscicides, nematicides, plant growth regulators and others. Among these, organochlorine (OC) insecticides, used successfully in controlling a number of diseases, such as malaria and typhus, were banned or restricted after the 1960s in most of the technologically advanced countries. The introduction of other synthetic insecticides – organophosphate (OP) insecticides in the 1960s, carbamates in 1970s and pyrethroids in 1980s and the introduction of herbicides and fungicides in the 1970s–1980s contributed greatly to pest control and agricultural output. Ideally a pesticide must be lethal to the targeted pests, but not to non-target species, including man. Unfortunately, this is not the case, so the controversy of use and abuse of pesticides has surfaced. The rampant use of these chemicals, under the adage, “if little is good, a lot more will be better” has played havoc with human and other life forms.

Production and usage of pesticides in India
The production of pesticides started in India in 1952 with the establishment of a plant for the production of BHC near Calcutta, and India is now the second largest manufacturer of pesticides in Asia after China and ranks twelfth globally (Mathur, 1999). There has been a steady growth in the production of technical grade pesticides in India, from 5,000 metric tons in 1958 to 102,240 metric tons in 1998. In 1996–97 the demand for pesticides in terms of value was estimated to be around Rs. 22 billion (USD 0.5 billion), which is about 2% of the total world market.

The pattern of pesticide usage in India is different from that for the world in general. As can be seen in Figure 1, in India 76% of the pesticide used is insecticide, as against 44% globally (Mathur, 1999). The use of herbicides and fungicides is correspondingly less heavy. The main use of pesticides in India is for cotton crops (45%), followed by paddy and wheat.



Figure 1

Consumption pattern of pesticides.





Benefits of pesticides
The primary benefits are the consequences of the pesticides' effects – the direct gains expected from their use. For example the effect of killing caterpillars feeding on the crop brings the primary benefit of higher yields and better quality of cabbage. The three main effects result in 26 primary benefits ranging from protection of recreational turf to saved human lives. The secondary benefits are the less immediate or less obvious benefits that result from the primary benefits. They may be subtle, less intuitively obvious, or of longer term. It follows that for secondary benefits it is therefore more difficult to establish cause and effect, but nevertheless they can be powerful justifications for pesticide use. For example the higher cabbage yield might bring additional revenue that could be put towards children's education or medical care, leading to a healthier, better educated population. There are various secondary benefits identified, ranging from fitter people to conserved biodiversity.

Improving productivity
Tremendous benefits have been derived from the use of pesticides in forestry, public health and the domestic sphere – and, of course, in agriculture, a sector upon which the Indian economy is largely dependent. Food grain production, which stood at a mere 50 million tons in 1948–49, had increased almost fourfold to 198 million tons by the end of 1996–97 from an estimated 169 million hectares of permanently cropped land. This result has been achieved by the use of high-yield varieties of seeds, advanced irrigation technologies and agricultural chemicals (Employment Information: Indian Labour Statistics, 1994). Similarly outputs and productivity have increased dramatically in most countries, for example wheat yields in the United Kingdom, corn yields in the USA. Increases in productivity have been due to several factors including use of fertiliser, better varieties and use of machinery. Pesticides have been an integral part of the process by reducing losses from the weeds, diseases and insect pests that can markedly reduce the amount of harvestable produce. Warren (1998) also drew attention to the spectacular increases in crop yields in the United States in the twentieth century. Webster et al. (1999) stated that “considerable economic losses” would be suffered without pesticide use and quantified the significant increases in yield and economic margin that result from pesticide use. Moreover, in the environment most pesticides undergo photochemical transformation to produce metabolites which are relatively non-toxic to both human beings and the environment (Kole et al., 1999).

/pdf/impact-of-pesticides-use-in-agriculture-their-benefits-and-4mrnc990nj.pdf

Impact of pesticides use in agriculture: their benefits and hazards.

Intensive agriculture is spectacularly successful since last couple of decades due to the inputs viz; fertilizers and pesticides along with high yielding varieties. The mandate for agriculture development was to feed and adequate nutrition supply to the expanding population by side the agriculture would be entering to into new area of commercial and export orientation. The attention of public health and proper utilization natural resources are also the main issues related with agriculture development. Concern for pesticide contamination in the environment in the current context of pesticide use has assumed great importance [1]. The fate of the pesticides in the soil environment in respect of pest control efficacy, non-target organism exposure and offsite mobility has been given due consideration [2]. Kinetics and pathways of degradation depend on abiotic and biotic factors [6], which are specific to a particular pesticide and therefore find preference. Adverse effect of pesticidal chemicals on soil microorganisms [3], may affect soil fertility [4] becomes a foreign chemicals major issue. Soil microorganisms show an early warning about soil disturbances by foreign chemicals than any other parameters.

But the fate and behavior of these chemicals in soil ecosystem is very important since they are degraded by various factors and have the potential to be in the soil, water etc. So it is indispensable to monitor the persistence, degradation of pesticides in soil and is also necessary to study the effect of pesticide on the soil quality or soil health by in depth studies on soil microbial activity.

The removal of metabolites or degraded products should be removed from soil and it has now a day’s primary concern to the environmentalist. Toxicity or the contamination of pesticides can be reduced by the bioremediation process which involves the uses of microbes or plants. Either they degrade or use the pesticides by various co metabolic processes.

/pdf/impact-of-pesticides-on-soil-microbiological-parameters-and-5cardf382e.pdf

Impact of pesticides on soil microbiological parameters and possible bioremediation strategies

A laboratory experiment was performed to study the persistence of imidacloprid from two formulations (Confidor 200 g litre-1 SL and Gaucho 700 g kg-1 WS), and its metabolism in three different soils (Gangetic alluvial soil of Kalyani, lateritic soil of Jhargram and coastal alkaline soil of Canning) of West Bengal following application at 0.5 kg and 1.0 kg AIha-1. Dissipation of imidacloprid in soil followed first-order kinetics and DT50 values ranged from 28.7 to 47.8 days. The shortest half-lives (28.7 and 35.8 days) were observed in the lateritic soil of Jhargram for both liquid and powder formulations. The formation of two metabolites of imidacloprid, imidacloprid-urea and imidacloprid-olefin, was first detected on day 30 of degradation at 28 (+/- 1) degrees C in all three soils.

Persistence and metabolism of imidacloprid in different soils of West Bengal

Degradation and effects of pesticides on soil microbiological parameters - a review.

Imidacloprid [ 1-[(6-Chloro-3 -Pyridinyl) methyl ]- N-nitro -2- Imidazolidinimine] is a newly introduced broad spectrum systemic insecticide in the Indian subcontinent by M/s. Bayer India Ltd.. This new chloronicotinyl compound is fairly soluble in water as compared to other non-polar insecticides (Kagabu 1997). It is effective against sucking insects, soil insects, termites and some species of chewing insects and is used as seed dressing, soil treatments and foliar treatment in different crop (Tomlin 1994). Some information regarding the fate of imidacloprid in soil are available (Cox et al. 1997; Rouchaud et al. 1994; 1996 ). Photolysis of the insecticide in aqueous solution was reported by Moza et al. (1998). But little is known about its persistence behaviour in water. The objective of the present investigation is to evaluate the effect of pH of water as well as the type of formulations on the persistence behaviour of imidacloprid in aqueous solution. MATERIALS AND METHODS Analytical grade imidacloprid (purity 99%) and its two formulations - Confidor 200 SL and Gaucho 70 WS were obtained from Ms. Bayer India Ltd.. The reagents used were of analytical grade and the solvents were HPLC grade. The buffer solutions (Titrisol of pH - 4.0, 7.0 and 9.0, E. Merck India Ltd.) were added @ 50mL/500mL of water (HPLC grade) and are designated as A, B and C respectively. 100 ml of these buffered solutions were taken in amber colored glass bottles. Contidor 200 SL (0.5 g) was dissolved in 1.0 L of water (100 µg/mL a.i.) and suitably diluted to 1.0 µg/mL of imidacloprid in the final solution. From this stock solution, Confidor 200 SL (imidacloprid) was applied @ 0.078 mg/L a.i. (T1) and 0.155 mg/L a.i. (T2) in different batches of water (A, B, C) in three replicate numbers. Seven such sets were prepared for sampling at 0, 7, 15, 20, 30, 45 and 60 d after application of the pesticide. All the bottles were kept under room temperature (30 ± 5°C). Solution of Gaucho 70 WS (0.5 g/L) was also prepared (350 µg / mL a.i.) in the same manner, diluted to 1.0 µg/mL of imidacloprid and was applied to different sets of water as described above.

Ashim Chowdhury

Papers

Impact of pesticides use in agriculture: their benefits and hazards.

Impact of pesticides on soil microbiological parameters and possible bioremediation strategies

Persistence and metabolism of imidacloprid in different soils of West Bengal

Degradation and effects of pesticides on soil microbiological parameters - a review.

Effect of pH and type of formulation on the persistence of imidacloprid in water.