Critical Review pubs.acs.org/est
Critical Review on the Environmental Fate of Quaternary Ammonium Herbicides in Soils Devoted to Vineyards Mirian Pateiro-Moure,† Manuel Arias-Estévez,† and Jesús Simal-Gándara*,‡ †
Soil and Agricultural Science Group, Plant Biology and Soil Science Department, Faculty of Food Science and Technology, University of Vigo, Ourense Campus, E32004 Ourense, Spain ‡ Nutrition and Bromatology Group, Analytical and Food Chemistry Department, Faculty of Food Science and Technology, University of Vigo, Ourense Campus, E32004 Ourense, Spain ABSTRACT: Quaternary Ammonium Herbicides (QUATs) are nonselective contact herbicides, widely used at weed emergence to protect a wide range of crops. The benefits achieved by the use of these herbicides are indisputable. In soils devoted to vineyards, their uses increase the yield and the quality of the grapes for winemaking. However, several environmental dangers have emerged from the overuse of these compounds. Therefore, there has been a great interest in the presence of these compounds in soils, water, and food. Once in the soil, the mobility of these agrochemicals plays an important role in their fate and transport in the environment. This is why we mainly focused our review on (a) their physical and chemical properties and their activity, (b) the factors affecting their mobility in soils, (c) the quality of surrounding waters, and (d) the measures to reduce their contamination, especially in the case of agricultural soils devoted to vineyards.
1. GENERAL DESCRIPTION OF QUATS 1.1. Physical and Chemical Properties and Their Activity. Herbicides are defined as those products that control weeds, plants growing out of place or where man does not want them to grow. Quaternary ammonium compounds, a group of herbicides commonly known as QUATs, are widely used in agriculture to increase productivity. Their physicochemical characteristics are shown in Table 1. QUATs were developed from quaternary ammonium germicides, paraquat being the first to be synthesized in 1882. It has been used as a redox indicator (under the name methyl violet) in chemical laboratories since 1933, but its herbicidal properties were discovered in 1957, and the herbicide has been marketed since 1962 under the name paraquat as a highly effective contact herbicide in more than 130 countries. Diquat and paraquat are bipyridyl derivatives whose chemical constitution corresponds to the load of divalent cations with two pyridine rings per molecule; they occur frequently in the form of highly hygroscopic salts, which is the reason why technical and formulated products consist of aqueous solutions of these compounds. These contact herbicides are fast acting and are absorbed and trans-located, which causes plant foliage desiccation. Paraquat is a nonselective synthetic herbicide generally marketed as dichloride salt or salts as dimethyl sulfate. It is marketed under the trade name Gramoxone or Dextrone by Syngenta in countries such as U.S., China, Mexico, Thailand, Malaysia, and Japan. It is often marketed in combination with other herbicides such as diquat, monolinuron, diuron, and © 2013 American Chemical Society
simazine. These technical products in liquid form contain paraquat in percentages of 20−50%. It has been used in spot treatments on fruit, citrus, olives, vineyards, and banana trees. The destruction achieved in adventitious weeds is total but for short time; therefore, it is combined with residual herbicides to extend the effect obtained. Diquat is typically marketed as dibromide salt monohydrate. It is marketed under the name Reglone by Syngenta in countries such as U.S., Canada, Brazil, France, and Germany. Diquat is also sold in combination with paraquat. Technical products in liquid form contain diquat in percentages of 20− 25%. It has been used as a desiccant and defoliant in various crops such as alfalfa, potato, beet, soybeans, and also in fruits and citrus. They are among the most widely used herbicides in the world; in the European Union, they are included in a priority list of herbicides of potential concern, because of their widespread use in the Mediterranean countries1 and because they are present as residues in the environment, food, and biological samples. They are employed in the destruction of weeds before sowing or on uncultivated land and quickly damage plant tissues, with the destruction of cell membranes causing the plant to appear frost damaged. The rapid wilting processes occur within hours, which make these herbicides Received: Revised: Accepted: Published: 4984
February April 23, April 23, April 24,
18, 2013 2013 2013 2013
dx.doi.org/10.1021/es400755h | Environ. Sci. Technol. 2013, 47, 4984−4998
Environmental Science & Technology
Critical Review
Table 1. Physicochemical Characteristics, Action Mode, and Toxicity of QUATsa
Data were obtained from the refs 2−5. bMolecular weight. cSolubility in water 20 °C. dOctanol/water partition coefficient at 20 °C. ePartition coefficient normalized to organic carbon content (mL goc−1 or L kgoc−1) fAerobic soil half-life (Average, days). gLethal dose50 (mg kg−1) a
Table 2. Limits of Detection (LODs) of QUATs in Different Matrices11−19,a herbicide PQ, PQ, PQ, PQ, PQ, PQ, PQ, PQ, PQ
DQ, DQ, DQ, DQ, DQ, DQ DQ DQ,
DFQ DFQ DFQ DFQ DFQ
DFQ
sample
sample preparation
analytical technique
LOD (μg L−1)
refs
water water water water water water beverages, urine soils blood, urine
SPE SPE SPE stacking concn SPE SPE SPE SPE SPE
HPLC HPLC-MS LC-MS-MS CE CZE LC-MS CZE-DAD LC-MS-MS GC-IT/MS
