Bioremediation of Agricultural Soils Polluted with Pesticides: a Review
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bioengineering Review Bioremediation of Agricultural Soils Polluted with Pesticides: A Review Carla Maria Raffa and Fulvia Chiampo * Department of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy; [email protected] * Correspondence: [email protected]; Tel.: +39-011-090-4685 Abstract: Pesticides are chemical compounds used to eliminate pests; among them, herbicides are compounds particularly toxic to weeds, and this property is exploited to protect the crops from unwanted plants. Pesticides are used to protect and maximize the yield and quality of crops. The excessive use of these chemicals and their persistence in the environment have generated serious problems, namely pollution of soil, water, and, to a lower extent, air, causing harmful effects to the ecosystem and along the food chain. About soil pollution, the residual concentration of pesticides is often over the limits allowed by the regulations. Where this occurs, the challenge is to reduce the amount of these chemicals and obtain agricultural soils suitable for growing ecofriendly crops. The microbial metabolism of indigenous microorganisms can be exploited for degradation since bioremediation is an ecofriendly, cost-effective, rather efficient method compared to the physical and chemical ones. Several biodegradation techniques are available, based on bacterial, fungal, or enzymatic degradation. The removal efficiencies of these processes depend on the type of pollutant and the chemical and physical conditions of the soil. The regulation on the use of pesticides is strictly connected to their environmental impacts. Nowadays, every country can adopt regulations to restrict the consumption of pesticides, prohibit the most harmful ones, and define the admissible concen- Citation: Raffa, C.M.; Chiampo, F. trations in the soil. However, this variability implies that each country has a different perception Bioremediation of Agricultural Soils of the toxicology of these compounds, inducing different market values of the grown crops. This Polluted with Pesticides: A Review. review aims to give a picture of the bioremediation of soils polluted with commercial pesticides, Bioengineering 2021, 8, 92. https:// considering the features that characterize the main and most used ones, namely their classification doi.org/10.3390/bioengineering8070092 and their toxicity, together with some elements of legislation into force around the world. Academic Editors: Bruna Matturro and Marco Zeppilli Keywords: pesticides; bioremediation; agricultural soil; environmental pollution; sustainable agri- culture; toxicity; health effects Received: 6 May 2021 Accepted: 23 June 2021 Published: 2 July 2021 1. Introduction Publisher’s Note: MDPI stays neutral Soil pollution is a worldwide problem that draws its origins from anthropologic with regard to jurisdictional claims in and natural sources. Urbanization, industrialization, and food-demand increases have published maps and institutional affil- required the use of compounds, substances, and chemical agents, which, over the years, iations. have brought on the dispersion and accumulation of pollutants in the environment. The common pollutants present in the soil are heavy metals, polycyclic aromatic hydrocarbons (PAHs), or pesticides [1]. Pesticides are chemical compounds used to eliminate pests. They are chemical or Copyright: © 2021 by the authors. biological agents, that weaken, incapacitate, and kill pests. Based on the types of targeted Licensee MDPI, Basel, Switzerland. pests, the pesticides can be divided into several groups, namely insecticides, herbicides, This article is an open access article rodenticides, bactericides, fungicides, and larvicides. distributed under the terms and During the 19th and 20th centuries, the extracts from plants, namely pyrethrins, were conditions of the Creative Commons used as insecticides, fungicides, and herbicides. The increase in pesticide use happened Attribution (CC BY) license (https:// with synthetic chemistry during the 1930s. In this period, inorganic chemicals such as creativecommons.org/licenses/by/ arsenic and sulfur compounds were applied for crop protection. The arsenic poison was 4.0/). Bioengineering 2021, 8, 92. https://doi.org/10.3390/bioengineering8070092 https://www.mdpi.com/journal/bioengineering Bioengineering 2021, 8, x FOR PEER REVIEW 2 of 29 Bioengineering 2021, 8, x FOR PEER REVIEW 2 of 29 Bioengineering 2021, 8, 92 2 of 29 with synthetic chemistry during the 1930s. In this period, inorganic chemicals such as ar- withsenic synthetic and sulfur chemistry compounds during were the 1930s.applied In fothisr crop period, protection. inorganic The chemicals arsenic suchpoison as ar-was senicfatalfatal toand to insects, insects, sulfur while whilecompounds the the sulfur sulfur were was was applied used used as asfo a ra fungicide. cropfungicide. protection. At At the the beginningThe beginning arsenic of ofpoison the the Second Second was fatalWorldWorld to War,insects, War, numerous numerous while the pesticides pesticides sulfur was werewere used synthesized, as a fungicide. mainly mainly At theorganic organic beginning chemicals, chemicals, of the such suchSecond as as di- Worlddichlorodiphenyltrichloroethanechlorodiphenyltrichloroethane War, numerous pesticides (DDT), were (DDT), synthesized, aldrin, aldrin, and and mainlydieldrin dieldrin organic used used as chemicals, as insecticides, insecticides, such while whileas di- 2- chlorodiphenyltrichloroethane2-methyl-4-chlorophenoxyaceticmethyl-4-chlorophenoxyacetic (DDT), acid acid (MCPA) aldrin, and and 2,4-dichlorophenoxyaceticdieldrin2,4-dichlorophenoxyacetic used as insecticides, acidacid while (2,4-D) (2,4-D) 2- methyl-4-chlorophenoxyaceticwerewere used used as as herbicides herbicides [2 [2].]. acid (MCPA) and 2,4-dichlorophenoxyacetic acid (2,4-D) were AfterusedAfter as 1945, 1945, herbicides there there was was[2]. a a rapid rapid development development of of the the agrochemical agrochemical field, field, characterized characterized byby the theAfter introduction introduction 1945, there of ofwas many many a rapid insecticides, insecticides, development fungicides, fungicides, of the herbicides, herbicides,agrochemical and and field, other other characterized chemicals, chemicals, to to bycontrolcontrol the introduction pests pests and and ensure ensureof many the the insecticides, yields yields of of agricultural agricu fungicides,ltural production. production. herbicides, Moreover, andMore otherover, pesticideschemicals, pesticides are toare controlappliedapplied pests in in aquaculture, aquaculture,and ensure horticulture, the horticulture, yields of and agricu and for variousforltural various production. general general household More householdover, applications. pesticides applications. They are appliedareThey also are usedin alsoaquaculture, to used control to control vector-borne horticulture, vector-borne diseases and for diseases (e.g., various malaria (e.g., general mala andria dengue)household and dengue) [3]. applications. [3]. They FromareFrom also 1990 1990 used toto to2018, control there there vector-borne have have been been register diseases registereded (e.g.,amounts amounts mala ofria used of and used pesticides dengue) pesticides [3]. by all by coun- all countriestriesFrom in the in1990 theworld, to world, 2018, especially there especially have in Asiabeen in Asia andregister and America. America.ed amounts The The world of world used average pesticides average quantity quantity by all coun-has has in- increased from 1.55 kg·ha−1 in 1990 to 2.63 kg·ha−1 in 2018, as shown in Figure1. Looking triescreased in the from world, 1.55 especiallykg·ha−1 in 1990in Asia to 2.63and kg·haAmerica.−1 in 2018,The worldas shown average in Figure quantity 1. Looking has in- at at the types, fungicides− and1 bactericides are used−1 more than the others (Figure2). creasedthe types, from fungicides 1.55 kg·ha and in bactericides 1990 to 2.63 ar kg·hae used in more 2018, than as shown the others in Figure (Figure 1. 2).Looking at the types, fungicides and bactericides are used more than the others (Figure 2). Figure 1. Pesticides use per area of cropland (data from [4]). Figure 1. Pesticides use per area of cropland (data from [4]). Figure 1. Pesticides use per area of cropland (data from [4]). Figure 2. Pesticides use from 1990 to 2016 (data from [4]). FigureFigure 2. PesticidesPesticides use use from from 1990 to 2016 (data from [4]). [4]). There has been no decrease even over the years, and directives have been imple- mentedThereThere in hashas many beenbeen countries no no decrease decrease around even even the over overworld the the years, to years,reduce and directivesand the usedirectives of have pesticides, beenhave implementedbeen for example, imple- mentedinthe many Regulation in countries many countries(EC) around 1107/2009 around the world[5] the of world tothe reduce European to reduce the useUnion the of use or pesticides, ofthe pesticides, Stockholm for example,for Convention example, the theRegulation[6], Regulation which (EC)focuses (EC) 1107/2009 on1107/2009 eliminating [5] [5] of the ofor the Europeanreducing European of Union persistent Union or theor organic the Stockholm Stockholm pollutants Convention Convention (POPs). [6 To], [6],which which focuses focuses on eliminatingon eliminating or reducing or reducing of persistent of persistent organic organic pollutants pollutants (POPs). (POPs). To this To purpose, the governments have to take