DELINEATION OF METALS AND METALLOID STATUS OF BASMATI RICE GROWING AREAS OF LUDHIANA AND PHYTOREMEDIATION OF METAL POLLUTED SOILS
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Date
2019
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Division of Soil Science and Agricultural Chemistry ICAR-Indian Agricultural Research Institute, New Delhi-
Abstract
Metal and metalloid contamination is a matter of concern across the globe including India. Heavy metal
and metalloid contaminants of both geogenic and anthropogenic origins present in soil, include cadmium
(Cd), chromium (Cr), lead (Pb), nickel (Ni), mercury (Hg), copper (Cu), arsenic (As) etc.. This kind of
contamination not only degrades the quality of soil, water and food crops, but also impairs human health
through getting into the food chain. Basmati rice is one of the most important export commodities,
through which, India earns considerable amount of foreign currency. Now-a-days, stringent quality norms
are being put by various organizations including European Union for food materials to protect human
health from metal and metalloid hazard. Punjab is one of the leading Basmati growing states of India in
terms of its acreage. Ludhiana district is known as industrial hub of Punjab, which underlines the
importance of periodically monitoring of metal and metalloid status in soil, plant and water as well as
developing ways and means for managing contaminated soils (if any). On routine basis it is not always
possible to assess level of contamination of pollutant element in food materials grown on polluted soils.
Here, lies the importance of modeling of pollutant element uptake by plants based on important soil
characteristics including extractable metal and metalloid content in soil. Therefore, present study was
undertaken with the objectives (i) to assess the status of metals and metalloid in soil, water and plants in
Basmati rice growing areas of Ludhiana, (ii) to predict the metals and metalloid contents in Basmati grain
using solubility and free ion activity model, (iii) to assess the efficacy of accumulator plant for removing
metals and metalloid from polluted soil and (iv) to study the effect of metal accumulator plants on metals
and metalloid in different fractions in soil vis-a-vis their availability to Basmati rice. In order to achieve
these objectives, in all, 102 paired soil and plant samples, and 25 irrigation water samples were collected
from Ludhiana and analyzed for metals and metalloid. Metals and metalloid content of Basmati grain of
the Ludhiana district was predicted using integrated solubility and free ion activity model (FIAM).
Further, efficacy of sunflower, marigold and spinach for phytoextraction of metal and metalloid was
studied in a pot culture experiment using contaminated soil. Subsequently, Basmati rice was grown using
same soil after harvest of accumulator plants.
Results indicated that DTPA extractable toxic metals viz., Ni, Cd, Pb and Cr of the soils of the
Ludhiana district varied from 40 to 630, 4.40 to 85.3, 388 to 3452, 44.7 to 154 µg kg-1
, respectively.
Olsen (NaHCO3) extractable arsenic (As) content of the soil ranged from 23.0 to 99.0 µg kg-1
. Nickel, Cd,
Pb, Cr and As content in Basmati grain ranged from 30 to 140, 2.00 to 8.00, 40.0 to 80.3, 4.67 to 8.00 and
pg. 148
10.0 to 61.3 µg kg-1
, respectively. Risk to human health for intake of metal and metalloid through
consumption of Basmati rice grain was assessed in terms of hazard quotient (HQ). The values of HQ for
Ni, Cd, Pb, Cr and As varied from 0.004 to 0.02, 0.006 to 0.023, 0.03 to 0.07, 0.004 to 0.008 and 0.014 to
0.083, respectively. It shows that the Basmati grain grown in Ludhiana district for human consumption.
By and large, soil of Ludhiana district is well supplied with micronutrients. Calibration and validation
indicated that solubility-FIAM is a useful tool for predicting metal and metalloid content in Basmati rice
grain grown in Ludhiana district on routine basis. For managing polluted soil, sunflower and marigold
were proved to have better phytoextraction ability over that of spinach. Toxic metal (Ni, Pd, Cd and Cr)
contents in rice straw significantly decreased due to growing of accumulator plants. Although, the content
of pollutant elements (Ni, Pd, Cd and Cr) in grain and husk of subsequently grown rice crop was not
significantly affected by phytoextraction. The results show that growing of accumulator plants is a good
strategy to restrict the entry of toxic elements to plants. It can be concluded that elevated levels of
pollutant elements (Ni, Pb, Cd, Cr and As) in soil, water and Basmati rice grain were not found in this
district and Basmati rice grain was safe to be consumed by human being as far as polluting elements are
concerned. Solubility-FIAM model would be very useful for routine assessment of suitability of soil for
growing Basmati rice. Among accumulator plants, sunflower and marigold can efficiently be used for
phytoextraction of polluting elements in soil.
Description
T-10265
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