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Adsorption of pesticides by salorthids and camborthids of Punjab, Pakistan
Authors: Muhammad Ilyas Tariq; Shahzad Afzal; Ishtiaq Hussain
Source: Toxicological and Environmental Chemistry, Volume 86, Number 4, September-December 2004 , pp. 247-264(18)
Publisher: Taylor and Francis Ltd
Abstract:
This study was conducted to examine adsorption of pesticides bifenthrin, carbosulfan,
-cyhalothrin, cypermethrin, endosulfan, parathion methyl, monocrotophos and 4-nitrophenol by sandy clay loam (S.C.L) and sandy loam (S.L) soils (with varying organic content). There was no significant difference between the observed soil water partitioning coefficient values (Kd) derived from linear and nonlinear Freundlich isotherms. Adsorption of pesticides on S.C.L soils was higher than those on S.L soils. Kd values showed significant correlations (r2 = 0.8 - 0.99 and 0.65 - 0.97) with soil organic carbon content (OC) and weak correlations (r2 = 0.2 - 0.29 and 0.1 - 0.18) with clay contents of S.C.L and S.L soil at p 
0.05, respectively for all pesticides (except monocrotophos). Observed Koc values (soil-water partitioning constants based on the organic C fraction of the soil) were in accordance with the literature values of Wauchope and Tomlin with a maximum deviation of less than 0.5 log units. Ten Quantitative Property-Property Relationships (QPPR) among water solubility, n-octanol water coefficient (Kow) and Koc were proposed for studied pesticides except monocrotophos. The models were considered acceptable when predicted-observed difference for log Kow and log Koc were 0.3 and 0.5 log units, respectively, during the validation procedure. This work indicates that the log Koc derived from the log Kow, from some of existing relationships, may be a fair predictor where observed values (i.e., Kd and Koc) are not available. Furthermore, predicted leaching potential by groundwater ubiquity scores (GUS) equation was solved by using observed Koc values and literature reported half lives of pesticides. GUS ranked the mobility of nonvolatile compounds i.e., bifenthrin, -cyhalothrin, cypermethrin and endosulfan extremely low; methyl parathion very low; 4-nitrophenol low; carbofuran and monocrotophos very high in S.C.L and S.L soils, respectively. Results discussed in this paper provide background to prioritize pesticides or chemical groups that should be evaluated under field conditions with regard to their leaching potential to groundwater in arid climates.
Keywords: Adsorption; Punjab Pakistan; Pesticides; Linear isotherm; Non-linear isotherm
Document Type: Research article
DOI: http://dx.doi.org/10.1080/02772240400007088
Publication date: 2004-09-01
- In this: publication
- By this: publisher
- In this Subject: Chemistry (General) , Earth and Environmental Sciences , Toxicology
- By this author: Muhammad Ilyas Tariq ; Shahzad Afzal ; Ishtiaq Hussain
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