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International Conference on

Recent Trends in Environmental Sustainability

ESCON22/ETERM/23
Optimizing the deployment time for DGT to assess the bioavailable fraction of Pb in
alkaline contaminated soils

1
1
2
*1
Muhammad Umair , Muhammad Saqib , Muhammad Zia-ur-Rehman , Muhammad Rizwan ,
1
Asad Jamil
1 Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, 38040,
Pakistan
2 Department of Environmental Science and Engineering, Government College University,
Faisalabad
Correspondence: umairsandhu6050@gmail.com
Abstract:

Total metal contents in a certain soil are unable to define the environmental toxicities of HMs
in plants or humans. The uptake rate of a certain metal is dependent on the bioavailable
concentration and mechanisms involved in its transport. The flux of metal ions from soil solid
to solution and then to plant roots is of prodigious concern. The fluxes of chemicals and their
routes in organisms can be correlated with their bioavailability. Therefore, evaluation of risk
assessment of HMs from contaminated soils requires determination of their bioavailable
concentration in the soil system. More specifically, bioavailable concentration is the portion of
HMs that is available fraction of total metals contents for the uptake of plants. Diffusive
gradient in thin films (DGT) is a new tool for toxicological and environmental assessments.
This dynamic tool provides high-resolution measurements about the bioavailable metal fraction
in soil and metal flux. A lab experiment was conducted to evaluate the optimum deployment
time for Pb measurement using DGT in alkaline contaminated soils. For this purpose, four
types of naturally contaminated (NC) soils (S) (S1 = NC Faisalabad (FSD), S2 = NC + @ 25
ppm Cd FSD, NC + @ 50 ppm Cd FSD, S4 = NC Multan (MN)) and six deployment times (2,
4, 8, 12, 24, and 48 hours) of DGT were used in this study. Results showed that optimum
equilibrium found at deployment time of 48 hours for all contamination levels. Maximum value
of equilibrium constant based on ratio (R) of DGT elution Pb and soil solution Pb found at
deployment time of 48 hours. Moreover, there found an increasing trend in R value with
passage of time. Minimum equilibrium ratio found at 2 hours deployment time followed by 4
< 8 < 12 < 24 < 48 hours. Maximum R value found for S1 (0.81) followed by S3 (0.79) > S2
(0.77) > S4 (0.69) at 48 hours. While at 24 hours the trend of R value was S1 (0.77) > S2 (0.71)
> S3 (0.67) S4 > (0.62). This data showed that R value of Pb is still away from “1” which
means it require more than 48 hours deployment time for optimum equilibrium. Hence, it was
concluded from this study that 48 hours deployment time showed maximum value for
equilibrium constant (R) but there need to extend equilibrium time for DGT based Pb
measurements in alkaline contaminated soils.
Keywords: Diffusive gradient thin films; Lead; Deployment time; Ecotoxicological
assessments; Bioavailable metals

Department of Environmental Sciences, COMSATS University Islamabad, Vehari Campus

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