Calculating pesticide sorption coefficients (kd) using selected soil propertiies

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Calculating pesticide sorption coefficients (K d ) using selected soil properties Jerome B. Weber a, * , Gail G. Wilkerson a , Carl F. Reinhardt b a Crop Science Department, North Carolina State University, Box 7620, Rayleigh, NC 27650-7620, USA b Department of Plant Protection, University of Pretoria, 0002 Pretoria, South Africa Received 24 March 2003; received in revised form 29 September 2003; accepted 24 October 2003 Abstract Pesticide soil/solution distribution coefficients (K d values), commonly referred to as pesticide soil sorption values, are utilized in computer and decision aid models to predict soil mobility of the compounds. The values are specific for a given chemical in a given soil sample, normally taken from surface soil, a selected soil horizon, or at a specific soil depth, and are normally related to selected soil properties. Pesticide databases provide K d values for each chemical, but the values vary widely depending on the soil sample on which the chemicals were tested. We have correlated K d values reported in the literature with the reported soil properties for an assortment of pesticides in an attempt to improve the accuracy of a K d value for a specific chemical in a soil with known soil properties. Mathematical equations were developed from regression equations for the related properties. Soil properties that were correlated included organic matter content, clay mineral content, and/or soil pH, depending on the chemical properties of the pesticide. Pesticide families for which K d equations were developed for 57 pesticides include the following: Carboxy acid, amino sulfonyl acid, hydroxy acid, weakly basic compounds and nonionizable amide/anilide, carbamate, dinitroaniline, organochlo- rine, organophosphate, and phenylurea compounds. Mean K d values for 32 additional pesticides, many of which had K d values that were correlated with specific soil properties but for which no significant K d equations could be developed are also included. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: K d value; Pesticide sorption; Pesticide retention; Pesticide binding; Leaching potential 1. Introduction Numerous books have been published on the reten- tion and mobility of pesticides in soils (Sawhney and Brown, 1989; Mickelson, 1993; Honeycutt and Scha- backer, 1994; Leng et al., 1995). Levels of pesticide retention by soils are commonly determined using the slurry method which consists of measuring the quantity of pesticide adsorbed from a specified concentration by a specified mass of soil. The ratio of pesticide sorbed (nmole/g) to pesticide remaining in solution (nmole/ml) is the (K d ); it is an indication of the sorption capacity of the chemical by the specified soil. K d values are generally determined at pesticide concentrations that would occur in soils when the compounds are applied at recom- mended rates followed by enough rainfall to bring the soil to field capacity (Weber et al., 2000). Soil charac- teristics, including the soil series name, taxonomic name, particle-size distribution or texture, % organic matter (OM) content, and 1:1 soil:solution pH are normally included. These K d values and soil property values are contained in many pesticide data bases and used in computer models (Carsel et al., 1984; Davis et al., 1990) * Corresponding author. Tel.: +1-919-515-2647; fax: +1-919- 515-5315. E-mail address: jerry_weber@ncsu.edu (J.B. Weber). 0045-6535/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2003.10.049 Chemosphere 55 (2004) 157–166 www.elsevier.com/locate/chemosphere and decision-aid models (Weber, 2003) to predict pesti- cide soil mobility. In most cases, average K d values are used. Our major objective was to correlate reported pesticide K d values with respective reported soil prop- erties in order to develop equations which would more accurately estimate K d values based on significantly re- lated soil parameters, so as to improve pesticide soil mobility predictions using models. 2. Materials and methods Pesticide data bases, including Ahrens (1994); ARS- PPD (2001); Hornsby et al. (1996); Montgomery (1997); and Tomlin (2000), and many scientific publications were utilized in obtaining pesticide K d values and their respective soil properties, including % organic matter or organic carbon (OC) content, % clay content (Cl), and soil pH. The following criteria were followed in con- structing the data base on which to perform the corre- lations and develop the predictive equations: (1) Only K d values reported for soils of 10% or less organic matter content were used, (2) K d values were calculated when only K oc values were reported using the relationship K d ¼ðK oc Þ(%OC)/(100) when %OC was reported, (3) colloidal soil organic matter was assumed to contain 58% carbon using the relationships %OC ¼ 0.58(%OM) and %OM ¼ 1.724 (%OC) when conversions were nee- ded, (4) when only soil texture was provided, %Cl was calculated using mean values from Table 1, and (5) soil pH was assumed to have been determined using a glass electrode equipped pH meter on 1:1 soil:water samples. Statistical correlations and development of regres- sion equations were performed using SAS (1985) statis- tical programs. Linear and curvilinear correlations were performed between pesticide K d values and soil proper- ties and among the soil properties, along with multiple correlation and regression analyses and significance testing according to the procedures of Little and Hills (1978). Our major objective was to develop equations based on significantly important soil properties that would more accurately estimate the relative pesticide sorption coefficients ( K d values) for selected pesticides when soil properties are available for a given soil. 3. Results and discussion 3.1. K d vs. soil properties for all pesticides and selected pesticide families K d values for all pesticides were correlated with %OM and %OM + %Cl, but r and R values were very small, and all soil properties were correlated with one Nomenclature alachlor, aldicarb, ametryn, anilazine, atrazine, azin- phosmethyl, azimsulfuron, benefin, bensulfuron, bromacil, carbaryl, carbofuran, chlorethoxyfos, chlo- rimuron, chlorsulfuron, cinmethylin, clomazone, cy- anazine, 2,4-D, dichlobenil, dicrotophos, dieldrin, dimethoate, diniconazole, dipropetryn, disulfoton, diuron, ethalfluralin, ethametsulfuron-methyl, etho- prop, ethylmetribuzin, fenamiphos, fenthion, fenuron, flumetsulam, fluometuron, flupyrsulfuron-methyl- sodium, fluridone, fomesafen, hexazinone, imazaquin, imazethapyr, isazofos, isofenphos, lindane, linuron, methiocarb, methoxycarb, metobromuron, metola- chlor, metribuzin, monolinuron, monuron, napro- pamide, neburon, nicosulfuron, nitrapyrin, oxamyl, parathion, phorate, picloram, piperophos, primisul- furon-methyl, profenophos, prometon, prometryn, propargite, propazine, propiconazole, propoxur, pyri- thiobac, quinclorac, quinomethionate, rimsulfuron, simazine, sulfometuron-methyl, 2,4,5-T, tebuthiuron, terbacil, terbutryn, thiabendazole, thiodicarb, tria- dimenol, triallate, tribenuron-methyl, triclorfon, tri- cyclazole, trifluralin, triflusulfuron-methyl Table 1 Estimated clay content of soils when only soil texture was re- ported Texture Abbreviation Clay content a Range (%) Mean (%) Sand s 0–10 5 Silt si 0–12 6 Loamy sand ls 0–16 8 Sandy loam sl 0–20 10 Silt loam sil 0–28 14 Loam l 8–28 18 Sandy clay loam scl 20–35 27 Clay loam cl 28–40 34 Silty clay loam sicl 28–40 34 Sandy clay sc 35–55 45 Silty clay sic 40–60 50 Clay c 40–100 70 a Soil Taxonomy (1975). US Department of Agriculture, Soil Conservation Service. John Wiley and Sons, Inc., NY, p. 471. 158 J.B. Weber et al. / Chemosphere 55 (2004) 157–166 another (Table 2). The positive relationship between pesticide sorption and soil OM content is well known and is the reason why OM and/or OC has been assumed to be the primary soil constituents responsible for inactivating pesticides (Thurston, 1953; Barlow and Hadaway, 1958; Upchurch and Mason, 1961; Sheets et al., 1962; Lambert, 1968; Goring and Hamaker, 1972; Carringer et al., 1975). Soil pH was inversely correlated with K d for COOH acids; and inclusion of OM or Cl did not improve the relationship (Table 2). OM and Cl were correlated in the soil, but pH was not related to either parameter con- firming the importance of pH to the binding of these compounds. With the exception of Cl only, all of the soil parameters were nearly equally related to K d of NHSO 2 acids, but the highest correlation was the inclusion of all three soil parameters (Table 2). OM and Cl and Cl and pH soil parameters were also related, but pH was not related to OM. K d values of OH acids were related to OM and Cl contents of the soil, and although pH alone was not related the highest correlations occurred between K d and all three soil parameters (Table 2). OM and Cl contents were related in the soil, but pH was not related to either parameter. Sorption of several acidic herbi- cides by soils as influenced by pH, OM, and Cl has been reported for imidazolinone compounds (Liu and Weber, 1985; Goetz et al., 1986; Renner et al., 1988; Stougaard et al., 1990; Che et al., 1992; Loux and Reese, 1992;  Alvarez/Bened  ı et al., 1998; Gennari et al., 1998; Regitano et al., 2000; Leone et al., 2001; N  egre et al., 2001), sulfonylurea herbicides (Liu and Weber, 1985; Frederickson and Shea, 1986; Shea, 1986;  Alvarez/ Bened  ı et al., 1998) and substituted phenoxy and benzoic acid herbicides (Grover and Smith, 1974). Sorption in- creased with increasing OM content and decreasing pH of the soil. Weakly basic pesticide K d values were related to soil OM and Cl contents but not to pH, but multiple cor- relations showed that OM, pH and/or Cl were related to K d values, OM and Cl were related in the soil, and OM was inversely related to pH (Table 2). Sorption of weakly basic pesticides in soils has been reported to be related to OM (Sheets et al., 1962; Harris, 1966; Weber et al., 1969; Shea and Weber, 1980; Kozak et al., 1983; Liu and Weber, 1985; Shea, 1986; Nicholls and Evans, 1991), Cl (Harrison et al., 1976; Grundl and Small, 1993; Weber and Swain, 1993; Seybold and Mersie, 1996; Singh et al., 2001), and inversely related to pH (McGlamery and Slife, 1966; Weber, 1966; Ladlie et al., 1976). K d values were not related to soil pH for any of the six nonionizable pesticide families, including amide/ anilide, carbamate, dinitroaniline, organochlorine, orga- nophosphate, or phenylurea compounds (Table 2). OM content was related to K d for four of the six families and Cl content related to K d for two of the six families. The highest correlation was between K d values and all three soil parameters for amide/anilide, dinitroaniline, and phenylurea families. No correlation was found between soil properties and K d values for the carbamates, and OM and Cl were related to K d for the organophos- phates. Among the soil properties themselves, OM and Cl were correlated for four of the six families. OM and Cl contents of soils have been reported to be related to the sorption of many nonionizable pesticides in soils (Harrison et al., 1976; Obrigawitch et al., 1981; Strek and Weber, 1982; Weber and Peter, 1982; Kozak et al., 1983; Peter and Weber, 1985; Calvet, 1989; Pusino et al., 1992; Singh et al., 2001; Vasilakoglou et al., 2001; Liu et al., 2002; Patakioutas and Albanis, 2002; Singh et al., 2002). 3.2. Relationships of K d values with soil properties and K d equations for selected pesticides Restricting correlations of soil properties to K d values for individual pesticide compounds resulted in 57 com- pounds for which best-fit K d equations were obtained (Table 3). K d equations for five COOH acid herbicides were developed utilizing pH levels and/or OM contents of soils, with none of the soil properties being correlated with one another. Sorption increased as OM content increased and/or as pH decreased. OM and pH were also the primary soil properties in best-fit K d equations obtained for five of the six NHSO 2 acid herbicides, with all three soil properties utilized in the K d equation for sulfometuron-methyl (Table 3). Cl was also one component of the K d equation for sulfo- meturon-methyl, but Cl and pH were also related soil properties. As was the case for the COOH acid her- bicides, sorption increased as OM increased or as pH decreased. K d equations for two OH acid herbicides utilized only the OM content of soils, probably because the very weak acidity of these compounds kept them primarily in the nonionized state (Table 3). Twelve weakly basic herbicides were found to have K d values highly correlated with soil properties (Table 3). Best-fit K d equations were obtained using OM con- tent only for tebuthiuron and terbutryn, pH only for ethylmetribuzin, OM and pH for ametryn and cyan- azine, Cl and pH for prometon, and all three soil parameters for the remaining six compounds. Soil properties were correlated with one another for nine of the twelve compounds. K d values increased as OM and/ or Cl content increased and as pH decreased. Best-fit K d equations utilized soil OM content only for two of the three amide/anilide herbicides, four of the six carbamate pesticides, all three of the organochlorine J.B. Weber et al. / Chemosphere 55 (2004) 157–166 159 Table 2 Correlation coefficients (r) and multiple correlation coefficients (R) for K d values vs. soil properties for all pesticides and for pesticide families Pesticide family Pesticide K d vs. soil properties a Soil property correlation a %OM %Cl pH %OM +Cl %OM + pH %Cl + pH %OM + %Cl + pH %OM vs. %Cl %OM vs. pH %Cl vs. pH r or R values b All pesticides 0.04 Ãà 0.02 0.01 0.08 ÃÃà 0.02 0.01 0.02 0.26 ÃÃà )0.10 ÃÃà 0.06 ÃÃà (2224) (2159) (1713) (2153) (1712) (1674) (1674) (2153) (1712) (1674) COOH acid 0.08 0.11 )0.40 ÃÃà 0.13 0.42 ÃÃà 0.46 ÃÃà 0.46 ÃÃà 0.21 ÃÃà 0.01 0.20 ÃÃà (208) (208) (208) (208) (208) (208) (208) (208) (208) (208) NHSO 2 acid 0.39 ÃÃà 0.05 )0.40 ÃÃà 0.45 ÃÃà 0.54 ÃÃà 0.41 ÃÃà 0.56 ÃÃà 0.33 ÃÃà )0.04 0.21 ÃÃà (139) (139) (137) (139) (136) (136) (135) (139) (136) (136) OH acid 0.64 ÃÃà 0.54 ÃÃà 0.12 0.70 ÃÃà 0.67 ÃÃà 0.56 ÃÃà 0.73 ÃÃà 0.44 ÃÃà )0.01 )0.10 (31) (31) (29) (31) (29) (29) (29) (31) (29) (29) Weak base 0.27 ÃÃà 0.14 ÃÃà 0.18 0.30 ÃÃà 0.32 ÃÃà 0.23 ÃÃà 0.32 ÃÃà 0.36 ÃÃà )0.18 ÃÃà 0.01 (976) (922) (926) (918) (926) (892) (892) (922) (926) (892) Amide/anilide 0.57 ÃÃà 0.20 Ãà 0.42 0.57 ÃÃà 0.47 Ãà 0.43 0.47 Ãà 0.31 ÃÃà )0.34 )0.20 (106) (106) (19) (106) (19) (19) (19) (106) (19) (19) Carbamate 0.17 0.03 0.28 0.19 0.31 0.28 0.31 0.30 ÃÃà 0.09 0.21 (81) (81) (52) (81) (52) (52) (52) (81) (52) (52) Dinitroaniline 0.14 0.19 0.03 0.19 0.38 Ãà 0.34 0.39 Ãà 0.40 ÃÃà )0.20 )0.10 (47) (47) (19) (47) (19) (19) (19) (47) (19) (19) Organochlorine 0.37 Ãà 0.23 0.36 0.50 ÃÃà 0.39 0.58 0.62 0.24 )0.56 )0.63 Ãà (45) (45) (12) (45) (12) (12) (12) (45) (12) (12) Organophosphate 0.29 Ãà 0.17 Ãà 0.13 0.30 ÃÃà 0.21 0.14 0.21 0.44 ÃÃà 0.10 0.01 (198) (198) (131) (198) (131) (131) (131) (198) (131) (131) Phenylurea 0.21 ÃÃà 0.01 0.15 0.21 ÃÃà 0.34 ÃÃà 0.15 0.36 ÃÃà 0.03 0.05 0.14 (270) (262) (108) (262) (108) (108) (108) (262) (108) (108) a OM = organic matter, Cl ¼ clay. b Significant at the 5% ( Ãà )or1%( ÃÃà ) level. Number of values correlated are in parentheses. 160 J.B. Weber et al. / Chemosphere 55 (2004) 157–166 Table 3 Best-fit equations for calculating soil K d values for 57 pesticides based on soil properties Pesticide No. of values Mean K d Equation a r or R value b Soil property correlations, r or R values a; b; c COOH acid 2,4-D 23 0.49 K d ¼ 1:9 À 0:2ðpHÞÆ0:4 0.63 ÃÃà ns Imazaquin 37 0.81 K d ¼ 2:6 þ 0:12ðOMÞÀ0: 35 ðpHÞÆ0:05 0.68 ÃÃà ns Imazethapyr 24 1.13 K d ¼ 10 :0 À 2:8ðpHÞþ0:21ðpHÞ 2 Æ 2:8 0.58 ÃÃà ns Picloram 51 0.47 K d ¼ 3:0 À 0:37ðpHÞÆ0:4 0.69 ÃÃà ns 2,4,5-T 8 1.24 K d ¼ 10 :5 À 1:2ðpHÞÆ2:2 0.86 ÃÃà ns NHSO 2 acid Chlorimuron 8 1.10 K d ¼ 6:1 þ 0:5ðOMÞÀ1:0 ðpHÞÆ1:3 0.99 ÃÃà ns Chlorsulfuron 15 0.69 K d ¼ 3:0 À 0:36ðpHÞÆ0:7 0.69 ÃÃà ns Flumetsulam 36 2.88 K d ¼ 9:83 þ 1:49ðOMÞÀ2:19ðpHÞÆ3:0 0.69 ÃÃà ns Fomesafen 5 4.52 K d ¼ 37 :8 þ 1:50ðOMÞÀ7: 21 ðpHÞÆ0:8 0.99 ÃÃà ns Sulfometuron-methyl 15 0.97 K d ¼ 3:0 þ 0:49ðOMÞÀ0: 03 ðClÞÀ0:47ðpHÞÆ2:3 0.70 Ãà Cl, pH (0.47 Ãà ) Triflusulfuron-methyl 5 0.78 K d ¼ 0:83 À 0:46ðOMÞþ0:13ðOMÞ 2 Æ 0:08 0.99 ÃÃà ns OH acid Bromacil 19 0.29 K d ¼ 0:1 þ 0:13ðOMÞÆ0: 1 0.48 Ãà ns Terbacil 14 0.85 K d ¼À0:1 þ 0:38ðOMÞÆ0:1 0.97 ÃÃà OM, Cl (0.57 ÃÃà ) Weak base Ametryn 38 5.69 K d ¼ 9:4 þ 1:49ðOMÞÀ1: 29 ðpHÞÆ2:8 0.58 ÃÃà ns Atrazine 185 2.65 K d ¼ 4:1 þ 0:43ðOMÞþ0: 09 ðClÞÀ0:81ðpHÞÆ1:0 0.77 ÃÃà OM, Cl (0.49) ÃÃà OM, pH (0.21) ÃÃà Cyanazine 21 2.46 K d ¼ 7:5 þ 0:3ðOMÞÀ1:03ðpHÞÆ2:5 0.75 ÃÃà OM, pH (0.51 Ãà ) Ethylmetribuzin 5 3.69 K d ¼ 15 :1 À 1:87ðpHÞÆ3:9 0.87 Ãà ns Fluridone 41 10.6 K d ¼ 13 :7 þ 1:0ðOMÞþ0:29ðClÞÀ1:91ðpHÞÆ7:2 0.66 ÃÃà OM, Cl (0.41 ÃÃà ) OM, pH (0.33 Ãà ) Metribuzin 61 0.94 K d ¼ 0:9 þ 0:18ðOMÞþ0: 012ðClÞÀ0:12ðpHÞÆ0:38 0.57 ÃÃà OM, Cl (0.40 ÃÃà ) Prometon 59 4.86 K d ¼ 19 :4 þ 0:21ðClÞÀ3:27ð pHÞÆ3:6 0.77 ÃÃà OM, Cl (0.42 ÃÃà ) Prometryn 122 7.00 K d ¼ 17 :3 þ 0:93ðOMÞþ0: 09 ðClÞÀ2:44ðpHÞÆ3:6 0.57 ÃÃà OM, Cl (0.36 ÃÃà ) OM, pH (0.26 ÃÃà ) Propazine 58 2.09 K d ¼ 3:4 þ 0:22ðOMÞþ0: 03 ðClÞÀ0:48ðpHÞÆ0:7 0.79 ÃÃà OM, Cl (0.32 Ãà ) Simazine 194 2.19 K d ¼ 5:3 þ 0:2ðOMÞþ0:03ðClÞÀ0:73ðpHÞÆ0:7 0.59 ÃÃà OM, Cl (0.27 ÃÃà ) Tebuthiuron 9 1.63 K d ¼ 0:4 þ 0:46ðOMÞÆ0: 4 0.86 ÃÃà ns Terbutryn 30 6.75 K d ¼ 2:5 þ 1:39ðOMÞÆ1: 2 0.64 ÃÃà OM, pH (0.53 ÃÃà ) Nonionizable/amide/anilide Alachlor 30 2.08 K d ¼ 0:2 þ 0:35ðOMÞþ0: 05 ðClÞÆ0:5 0.65 ÃÃà OM, Cl (0.37 Ãà ) Metolachlor 55 2.77 K d ¼ 0:5 þ 0:63ðOMÞÆ0: 26 0.84 ÃÃà OM, Cl (0.49 ÃÃà ) Napropamide 9 2.94 K d ¼À0:7 þ 2:66ðOMÞÆ0:7 0.95 ÃÃà OM, Cl (0.79 ÃÃà ) Nonionizable/carbamate Aldicarb 15 0.40 K d ¼À0:2 þ 0:31ðOMÞÀ0:02ðOMÞ 2 Æ 0:1 0.90 ÃÃà OM, Cl (0.80 ÃÃà ) Carbofuran 13 0.72 K d ¼À0:1 þ 0:17ðOMÞþ0:01ðClÞÆ0:1 0.90 ÃÃà OM, Cl (0.56 Ãà ) J.B. Weber et al. / Chemosphere 55 (2004) 157–166 161 Table 3 (continued) Pesticide No. of values Mean K d Equation a r or R value b Soil property correlations, r or R values a; b ; c Methiocarb 6 0.17 K d ¼ 12:8 À 10:8ðOMÞþ3:26ðOMÞ 2 Æ 0:1 0.99 ÃÃà ns Oxamyl 6 0.17 K d ¼À0:04 þ 0:07ðOMÞÆ0:04 0.96 ÃÃà OM, Cl (0.93 ÃÃà ) Propoxur 9 0.68 K d ¼ 0:09 þ 0:22ðOMÞÆ0:09 0.95 ÃÃà ns Thiodicarb 7 3.30 K d ¼À1:86 þ 1:5ðOMÞþ0:18ðClÞÆ0:9 0.98 ÃÃà ns Nonionizable/dinitroaniline Benefin 14 77.4 K d ¼À29:4 þ 14:1ðOMÞþ5:1ðClÞÆ24:0 0.71 ÃÃà ns Trifluralin 16 64.7 K d ¼À27:5 þ 13:0ðOMÞþ4:9ðClÞÆ14:0 0.90 ÃÃà ns Nonionizable/organochlorine Dieldrin 7 196 K d ¼ 73 þ 34:6ðOMÞÆ45 0.80 Ãà ns Lindane 12 16.7 K d ¼À11:3 þ 11:1ðOMÞÀ0:54ðOMÞ 2 Æ 5:3 0.94 ÃÃà ns Methoxychlor 11 2009 K d ¼ 536 þ 358ðOMÞÆ184 0.94 ÃÃà ns Nonionizable/organophosphate Azinphosmethyl 9 8.94 K d ¼ 4:35 þ 2:15ðOMÞÆ2:16 0.68 ÃÃà ns Chlorethoxyfos 7 63.2 K d ¼ 18:4 þ 14:0ðOMÞÆ3:5 0.99 ÃÃà OM, Cl (0.93 ÃÃà ) Dicrotophos 6 1.01 K d ¼À8:2 þ 9:3ðOMÞÀ1:75ðOMÞ 2 Æ 1:2 0.78 ÃÃà ns Dimethoate 7 0.45 K d ¼ 0:11 þ 0:09ðOMÞÆ0:1 0.85 Ãà ns Disulfoton 23 14.7 K d ¼À1:8 þ 6:1ðOMÞÆ4:2 0.68 ÃÃà ns Ethoprop 5 1.69 K d ¼ 1:0 þ 0:23ðOMÞÆ0:3 0.83 Ãà ns Fenamiphos 13 3.84 K d ¼ 0 þ 1:49ðOMÞÆ0:76 0.89 ÃÃà OM, Cl (0.91 ÃÃà ) OM, pH (0.60 Ãà ) Cl, pH (0.62 Ãà ) Fenthion 8 18.2 K d ¼À7:8 þ 12:6ðOMÞÆ4:2 0.94 Ãà ns Isofenphos 5 8.52 K d ¼ 4:9 þ 1:8ðOMÞÆ1:0 0.91 Ãà OM, Cl (0.63 ÃÃà ) Parathion 23 26.0 K d ¼À5:8 þ 11:4ðOMÞÆ5:6 0.86 ÃÃà OM, Cl (O.54 ÃÃà ) Nonionizable/phenylurea Diuron 120 7.37 K d ¼À1:4 þ 3:26ðOMÞÀ0:1ðOMÞ 2 Æ 1:1 0.75 ÃÃà ns Linuron 43 9.47 K d ¼ 4:0 þ 1:83ðOMÞÆ1:2 0.60 ÃÃà ns Metobromuron 12 5.22 K d ¼ 1:3 þ 0:9ðOMÞÆ1:0 0.83 ÃÃà ns Monolinuron 14 5.70 K d ¼ 2:4 þ 0:85ðOMÞÆ1:6 0.55 Ãà ns Neburon 6 89.7 K d ¼À16:3 þ 26:8ðOMÞÆ25:0 0.91 ÃÃà ns Nonionizable/misc. Clomazone 17 2.29 K d ¼ 0:33 þ 0:77ðOMÞÆ0:35 0.88 ÃÃà ns Dichlobenil 5 4.68 K d ¼ 1:4 þ 0:63ðOMÞÆ0:22 0.99 ÃÃà ns Triallate 8 31.5 K d ¼À4:6 þ 15:0ðOMÞÆ5:7 0.99 ÃÃà ns a OM ¼ organic matter, Cl ¼ clay. b Significant at the 5% ( Ãà )or1%( ÃÃà ) level. c ns ¼ none significant. 162 J.B. Weber et al. / Chemosphere 55 (2004) 157–166 insecticides, all 10 of the organophosphate insecticides, all five of the phenylurea herbicides and all three mis- cellaneous herbicides (Table 3). Soil OM and Cl contents were utilized in best-fit K d equations for one amide/ anilide herbicide, two carbamate insecticides, and both dinitroaniline herbicides. Soil pH was not utilized in best-fit K d equations for any of the nonionizable pesti- cides. OM and Cl were related soil properties in 10 of the 32 nonionizable pesticide compound correlations, OM and pH and Cl and pH in correlations for one com- pound each, and none of the soil properties were related in twenty two of the correlations. K d values increased as Table 4 Mean K d values for 32 pesticides and relationships to soil properties Pesticide No. of values Mean K d Soil property correlated a r or R value b Soil property correlations, r or R value a; b; c COOH acid Pyrithiobac 4 0.27 OM 0.99 Ãà iv Quinclorac 4 1.24 OM 0.99 ÃÃà iv NHSO 2 acid Azimsulfuron 4 1.26 pH 0.99 Ãà iv Bensulfuron 4 7.47 pH 0.97 Ãà iv Ethametsulfuron-methyl 4 2.12 OM 0.98 Ãà iv Flupyrasulfuron-methyl 7 0.37 OM, pH 0.89 Ãà ns Nicosulfuron 10 0.69 pH 0.99 ÃÃà iv Primisulfuron 3 0.17 pH 0.98 ÃÃà iv Rimsulfuron 4 0.87 pH 0.99 Ãà iv Tribenuron-methyl 4 1.08 pH 0.98 Ãà iv Weak base Anilazine 4 20.6 pH 0.99 Ãà iv Diniconazole 4 39.7 OM 0.95 Ãà iv Dipropetryn 9 9.84 OM 0.92 ÃÃà OM, pH (0.82 ÃÃà ) Hexazinone 10 0.45 OM, pH 0.92 ÃÃà OM, Cl (0.78 ÃÃà ) Propiconazole 20 6.27 Cl 0.53 à OM, Cl (0.59 ÃÃà ) Thiabendazole 4 9.55 OM, Cl, pH 0.99 ÃÃà iv Triadimenol 9 3.89 OM, pH 0.83 Ãà ns Tricyclazole 4 23.0 Cl 0.99 Ãà iv Nonionizable/carbamate Carbaryl 12 1.63 OM, Cl 0.69 à Cl, pH (0.91 ÃÃà ) Nonionizable/dinitroaniline Ethalfluralin 4 205 OM 0.99 ÃÃà iv Nonionizable/organophosphate Isazofos 4 1.48 OM 0.99 Ãà iv Phorate 10 6.47 OM 0.96 ÃÃà OM, Cl (0.93 ÃÃà ) Piperophos 14 31.8 OM, Cl 0.61 à ns Profenophos 4 22.0 OM, Cl 0.99 Ãà iv Triclorfon 9 0.27 OM, Cl 0.84 Ãà OM, Cl (0.60 à ) Nonionizable/phenylurea Fenuron 7 0.76 OM 0.82 à ns Fluometuron 13 0.99 OM 0.84 ÃÃà OM, Cl (0.71 à ) Monuron 26 2.04 OM 0.42 Ãà OM, Cl (0.66 Ãà ) Nonionizable/misc Cinmethylin 4 5.30 OM, Cl 0.99 à iv Nitrapyrin 10 4.14 OM 0.91 ÃÃà ns Quinomethionate 5 106 OM, Cl 0.97 à ns Propargite 4 107 OM 0.99 ÃÃà iv a OM ¼ organic matter, Cl ¼ clay. b Significant at the 10% ( à ), 5% ( Ãà ), or 1% ( ÃÃà ) level. c iv ¼ insufficient values, ns ¼ none significant. J.B. Weber et al. / Chemosphere 55 (2004) 157–166 163 OM content increased, and in several cases as Cl content increased. A sample calculation for atrazine serves to illustrate the large difference in K d values for two soils with known properties from that of a mean K d value: Soil A: 1% OM, 20% Cl, pH 6.5 K d ¼ 4:1 þ 0:43ð1Þþ0:09ð20ÞÀ0:81ð6: 5ÞÆ1: 0 ¼ 4:1 þ 0:43 þ 1: 8 À 5:3 ¼ 1:0 Æ 1 Soil B: 5% OM, 30% Cl, pH 5.5 K d ¼ 4:1 þ 0:43ð5Þþ0:09ð30ÞÀ0:81ð5: 5Þ ¼ 4:1 þ 2:2 þ 2: 7 À 4:4 ¼ 4:6 Æ 1 Mean of 185 values ¼ 2.6 Calculated K d values suggest that atrazine mobility would be highly underestimated in Soil A and highly over estimated in Soil B if the mean K d value were used. 3.3. Relationships of K d values with soil properties and mean K d values for selected pesticides K d values were correlated with soil properties for 32 additional pesticides, but the limited numbers of observations for each chemical did not allow for the development of best-fit equations (Table 4). Mean K d values for each of the pesticides is provided and indications are that K d values for the 10 COOH and NHSO 2 acid compounds were most strongly related to OM content and/or pH in the soils, and sorp- tion increased as OM content increased and/or as pH decreased. For the eight weakly basic pesticides, K d values were most strongly related to one or more of the three soil properties and sorption increased as OM and/or Cl in- creased and/or pH decreased (Table 4). K d values were most strongly related to OM and/or Cl contents of the soils for the fourteen nonionizable pesticides and increased as contents of the soil compo- nents increased. In summary, sorption of weakly acidic pesticides in soils, as indicated by K d values, was most strongly re- lated to soil OM content and/or inversely related to soil pH. Sorption of weakly basic pesticides (K d values) were most strongly related to soil OM and Cl contents and inversely related to pH. Nonionizable pesticide sorption in soils was most strongly related to soil OM and/or Cl contents. Utilizing equations to calculate K d values when soil properties are known may greatly improve soil mobility predictions of selected chemicals. Acknowledgements We acknowledge the Water Resources Research Institute of the University of North Carolina and the US Geological Survey (Grant No. 89-0496), the US Department of Agriculture (Grant No. 93-34214-8911) and North Carolina State University Agricultural Re- search Service for supporting this study, L.R. Swain, K.A. Taylor, and R.L. Warren for technical assistance and Judith A. Goodman for secretarial support. References Ahrens, W.H. (Ed.), 1994. Herbicide Handbook, seventh ed. Weed Science Society of America, Champaign, IL.  Alvarez/Bened  ı, J., Cart  on, A., Fern  andez, J.C., 1998. Sorption of tribenuron-methyl, chlorsulfuron, and imazamethabenz- methyl by soils. J. Agric. Food Chem. 46, 2840–2844. ARS Pesticide Properties Database., 2001. http://wizard.ars- usda.gov/acsl/ppdb.html. US Department of Agriculture, Beltsville, MD. Barlow, F., Hadaway, A.B., 1958. Studies on the aqueous suspensions of insecticides: Part IV. Further notes on the sorption of insecticides by soils. Bull. Entomol. Res. 49, 315–338. Calvet, R., 1989. Adsorption of organic chemicals in soils. Environ. Health Perspect. 83, 145–177. Carringer, R.D., Weber, J.B., Monaco, T.J., 1975. Adsorption– desorption of selected pesticides by organic matter and montmorillonite. J. Agric. Food Chem. 23, 568–572. Carsel, R.F., Smith, C.N., Milch, L.A., Dean, J.D., Galius, P., 1984. Users Manual for the Pesticide Root Zone Model (PRZM). US Environmental Protection Agency, Athens, GA. Che, M., Loux, M.M., Traina, S.J., Logan, T.J., 1992. Effect of pH on sorption and desorption of imazaquin and imazeth- apyr on clays and humic acid. J. Environ. Qual. 21, 698– 703. Davis, F.M., Leonard, R.F., Knisel, W.G., 1990. Gleams User Manual, US Department of Agriculture. Agricultural Research Service, Southeast Watershed Research Labora- tory, Tifton, GA. Frederickson, D.R., Shea, P.J., 1986. Effect of soil pH on degradation, movement and plant uptake of chlorsulfuron. Weed Sci. 34, 328–332. Gennari, M., N  egre, M., Vindrola, D., 1998. Adsorption of the herbicides imazapyr, imazethapyr and imazaquin on soils and humic acids. J. Environ. Sci. Health 33, 547–567. Goetz, A.J., Wehtje, G., Walker, R.H., Hajek, B., 1986. Soil solution and mobility characterization of imazaquin. Weed Sci. 34, 788–793. Goring, C.A.I., Hamaker, J.W. (Eds.), 1972. Organic Chemi- cals in the Soil Environment, vol. 2. Marcel Dekker, NY. Grover, R., Smith, A.E., 1974. Adsorption studies with the acid and dimethylamine forms of 2,4-D and dicamba. Can. J. Soil Sci. 54, 179–186. Grundl, T., Small, G., 1993. Mineral contributions to atrazine and alachlor sorption in soil mixtures of variable organic carbon and clay content. J. Contam. Hydrol. 14, 117–128. 164 J.B. Weber et al. / Chemosphere 55 (2004) 157–166 Harris, C.I., 1966. Adsorption, movement, and phytotoxicity of monuron and s-triazine herbicides in soils. Weeds 14, 6–10. Harrison, G.W., Weber, J.B., Baird, J.V., 1976. Herbicide phytotoxicity as affected by selected properties of North Carolina soils. Weed Sci. 24, 120–126. Honeycutt, R.C., Schabacker, D.J. (Eds.), 1994. Mechanisms of Pesticide Movement into Ground Water. Lewis Publishers/ CRC Press, Boca Raton, FL. Hornsby, A.G., Wauchope, R.D., Herner, A.E., 1996. Pesticide Properties in the Environment. Springer-Verlag, NY. Kozak, J., Weber, J.B., Sheets, T.J., 1983. Adsorption of prometryn and metolachlor by selected soil organic matter fractions. Soil Sci. 136, 94–101. Ladlie, J.S., Meggitt, W.F., Penner, D., 1976. Effect of soil pH on microbial degradation, adsorption and mobility of metribuzin. Weed Sci. 24, 477–481. Lambert, S.M., 1968. Omega, a useful index of soil sorption equilibria. J. Agric. Food Chem. 16, 340–343. Leng, M.L., Leovey, E.M.K., Zubkoff, P.L. (Eds.), 1995. Agrochemical Environmental Fate: State of the Art. Lewis Publ./CRC Press, Boca Raton, FL. Leone, P., Gennari, M., N  egre, M., Boero, V., 2001. Role of ferrihydrite in adsorption of three imidazolinone herbicides. J. Agric. Food Chem. 49, 1315–1320. Little, T.M., Hills, F.J., 1978. Agricultural Experimentation: Design and Analysis. John Wiley and Sons, NY. Liu, S.L., Weber, J.B., 1985. Retention and mobility of AC 252214 (imazaquin), chlorsulfuron, prometryn and SD 95481 (cinmethylin) in soils. Proc. South. Weed Sci. Soc. 38, 465–474. Liu, W., Gan, J., Yates, S.R., 2002. Influence of herbicide structure, clay acidity, and humic acid coating on acetan- ilide herbicide adsorption on homoionic clays. J. Agric. Food Chem. 50, 4003–4008. Loux, M.M., Reese, K.D., 1992. Effect of soil pH on adsorption and persistence of imazaquin. Weed Sci. 40, 490–496. McGlamery, M.D., Slife, F.W., 1966. The adsorption and desorption of atrazine as affected by pH, temperature, and concentration. Weeds 14, 237–239. Mickelson, S.H. (Ed.), 1993. Sorption and Degradation of Pesticides and Organic Chemicals in Soils. SSSA Spec. Publ. No. 32, Soil Science Society of America, Inc., Madison, WI. Montgomery, J.H., 1997. Agrochemicals Desk Reference, second ed. Lewis Publ./CRC Press, Boca Raton, FL. N  egre, M., Schulten, H.R., Gennari, M., Vindrola, D., 2001. Interaction of imidazolinone herbicides with soil humic acids. Experimental results and molecular modeling. J. Environ. Sci. Health B 36, 107–125. Nicholls, P.H., Evans, A.A., 1991. Sorption of ionisable organic compounds by field soils. Part 2: cations, bases and zwitterions. Pestic. Sci. 33, 331–345. Obrigawitch, T., Hons, F.M., Abernathy, J.R., Gipson, J.R., 1981. Adsorption–desorption and mobility of metolachlor in soils. Weed Sci. 29, 332–336. Patakioutas, G., Albanis, T.A., 2002. Adsorption–desorption studies of alachlor, metolachlor, EPTC, chlorothalonil and pirimiphos-methyl in contrasting soils. Pest Manag. Sci. 58, 352–362. Peter, C.J., Weber, J.B., 1985. Adsorption, mobility and efficacy of alachlor and metolachlor as influenced by soil properties. Weed Sci. 33, 874–881. Pusino, A., Liu, W., Gessa, C., 1992. Influence of organic matter and its clay complexes on metolachlor adsorption on soil. Pestic. Sci. 36, 283–286. Regitano, J.B., Alleoni, L.R.F., Vidal-Torrado, P., Casa- grande, J.C., Tornisielo, V.L., 2000. Imazaquin sorption in highly weathered tropical soils. J. Environ. Qual. 29, 894– 900. Renner, K.A., Meggitt, W.F., Penner, D., 1988. Effect of soil pH on imazaquin and imazethapyr adsorption to soil and phytotoxicity to corn (Zea mays). Weed Sci. 36, 78–83. SAS User’s Guide Statistics, 1985, fifth ed. SAS Institute, Cary, NC. Sawhney, B.L., Brown, K. (Eds), 1989. Reactions and Move- ment of Organic Chemicals in Soils. SSSA Spec. Publ. 22, Soil Science Society of America, Inc., Madison, WI. Seybold, C.A., Mersie, W., 1996. Adsorption and desorption of atrazine, deethylatrazine, deisopropylatrazine, hydroxyatr- azine, and metolachlor in two soils from Virginia. J. Environ. Qual. 25, 1179–1185. Shea, P.J., 1986. Chlorsulfuron dissociation and adsorption on selected adsorbents and soils. Weed Sci. 34, 474–478. Shea, P.J., Weber, J.B., 1980. Effect of pH and soil constituents on the persistence and availability of fluridone. Proc. South. Weed Sci. Soc. 33, 240–246. Sheets, T.J., Crafts, A.S., Drever, H.R., 1962. Influence of soil properties on the phytotoxicity of the s-triazine herbicides. J. Agric. Food Chem. 10, 458–462. Singh, N., Kloeppel, H., Klein, W., 2001. Sorption behavior of metolachlor, isoproturon, and terbuthylazine in soils. J. Environ. Sci. Health. B 36, 397–407. Singh, N., Kloeppel, H., Klein, W., 2002. Movement of metolachlor and terbuthylazine in core and packed soil columns. Chemosphere 47, 409–415. Soil Taxonomy, 1975. US Department of Agriculture, Soil Conservation Service. John Wiley and Sons, NY. p. 471. Stougaard, R.N., Shea, P.J., Martin, A.R., 1990. Effect of soil type and pH on adsorption, mobility, and efficacy of imazaquin and imazethapyr. Weed Sci. 38, 67–73. Strek, H.J., Weber, J.B., 1982. Adsorption, mobility, and activity comparisons between alachlor and metolachlor. Proc. South Weed Sci. Soc. 35, 332–338. Tomlin, C. (Ed.), 2000. The Pesticide Manual, twelfth ed. British Crop Protection Publs., The Royal Society of Chemistry, Cambridge, UK. Thurston, R., 1953. The effects of some soil characteristics on DDT phytotoxicity. J. Econ. Entomol. 46, 545–550. Upchurch, R.P., Mason, D.D., 1961. The influence of soil organic matter on the phytotoxicity of herbicides. Weeds 10, 9–14. Vasilakoglou, I.B., Eleftherohorinos, I.G., Dhima, K.B., 2001. Activity, adsorption and mobility of three acetani- lide and two new amide herbicides. Weed Res. 41, 535– 546. Weber, J.B., 1966. Molecular structure and pH effects on the adsorption of 13 s-triazine compounds on montmorillonite clay. Amer. Mineralog. 51, 1657–1670. Weber, J.B., 2003. Relative pesticide leaching potential (PLP) indices and ratings for commonly used pesticides, relative soil leaching potential (SLP) indices and ratings, and groundwater contamination potential (GWCP) risk of pesticide–soil combinations. In: North Carolina Agricultural J.B. Weber et al. / Chemosphere 55 (2004) 157–166 165 Chemicals Manual. North Carolina State University, Rayleigh, NC, pp. 21–26. Weber, J.B., Peter, C.J., 1982. Adsorption, bioactivity, and evaluation of soil tests for alachlor, acetochlor, and metolachlor. Weed Sci. 30, 14–20. Weber, J.B., Swain, L.R., 1993. Sorption of diniconazole and metolachlor by four soils, calcium-organic matter and calcium-montmorillonite. Soil Sci. 156, 171–177. Weber, J.B., Weed, S.B., Ward, T.M., 1969. Adsorption of s- triazines by soil organic matter. Weed Sci. 17, 417–421. Weber, J.B., Wilkerson, G.G., Linker, H.M., Wilcut, J.W., Leidy, R.B., Senseman, S., Witt, W.W., Barrett, M., Vencil, W.K., Shaw, D.R., Mueller, T.C., Miller, D.K., Brecke, B.J., Talbert, R.E., Peeper, T.F., 2000. A proposal to standardize soil/solution herbicide distribution coefficients. Weed Sci. 48, 75–88. 166 J.B. Weber et al. / Chemosphere 55 (2004) 157–166 . for K d values vs. soil properties for all pesticides and for pesticide families Pesticide family Pesticide K d vs. soil properties a Soil property correlation a %OM. important soil properties that would more accurately estimate the relative pesticide sorption coefficients ( K d values) for selected pesticides when soil properties