Long-term impact of irrigation with sewage effluents on heavy metal content in soils, crops and groundwater—a case study
Introduction
India supports more than 16% of the world's population with only 4% of the world's fresh water resources (Singh, 2003). Although agriculture sector in this country has been major user of water, share of water allocated to irrigation is likely to be decreased by 10–15% in next two decades (CWC, 2000). In this changing scenario, reuse of domestic and industrial waste water in agriculture for irrigating crops appears to be a lucrative option. Besides being source of irrigation water, these waste waters contain appreciable amounts of plant nutrients. In India, total waste water generated per annum from 200 cities is about 2600 Mm3 (Kaul et al., 1989) and also the use of sewage effluents for irrigating agricultural lands is on the rise especially in the peri-urban area. These waste waters carry appreciable amounts of trace toxic metals (Feign et al., 1991, Pescod, 1992, Som et al., 1994, Gupta et al., 1998, Brar et al., 2000, Yadav et al., 2002) and concentrations of trace metals in sewage effluents vary from city to city (Rattan et al., 2002). Although the concentration of heavy metals in sewage effluents are low, long-term use of these waste waters on agricultural lands often results in the build-up of the elevated levels of these metals in soils (Rattan et al., 2002). Extent of build-up of metals in waste water-irrigated soils depends on the period of its application (Bansal et al., 1992, Palaniswami and Sree Ramulu, 1994). Crops raised on the metal-contaminated soils accumulate metals in quantities excessive enough to cause clinical problems both to animals and human beings consuming these metal rich plants (Tiller, 1986). Since food chain contamination is one of the major routes for entry of metals into the animal system, monitoring the bioavailabile pools of metals in contaminated soils has generated a lot of interest (Datta et al., 2000, Yadav et al., 2002). Also information on the fractionation of trace metals in soils is potentially valuable in predicting bioavailability, metal leaching rates, and transformation between chemical forms in agricultural and polluted soils (Jenne and Louma, 1977, McBride, 1981, Miller et al., 1986). But such information on agricultural lands receiving sewage irrigation for quite a long time is meagre.
Crop species exercise differentiality in accumulating metals in their tissue (Lepp, 1981, Datta et al., 2000) and efficiency of different crops in absorption of metals is judged either by plant metal uptake or by transfer factor of metals from soil to plants. Uptake of metals by plants may be a good indicator of efficiency of metal absorption of different crop species grown on soils having uniform metal levels under controlled conditions. Whereas, transfer factor of metal from soil to plants indicates the efficiency of crop species better where crops are grown on soils having variable metal contents, e.g. farmers’ fields. Generally, soil to plant transfer factor of metals is computed based on total metal contents of soils (Hooda et al., 1997). However, total metal content in soils does not take into account the other soil factors that modify the bioavailability of metals. Hence, computation of soil to plant transfer factor of metals should be based on available soil metal pools.
We attempted to study some of the above-mentioned aspects in sewage-irrigated peri-urban agricultural lands under Keshopur Effluent Irrigation Scheme (KEIS) of the Delhi Government, India. Under this scheme, sewage irrigation has been provided to the farmers’ fields for more than two decades. Various cereals, millet, leafy vegetables and fodder crops have successfully been grown thereon. No investigation has been carried out in sewage-irrigated soils of this peri-urban area except one where we reported the build-up of some of major and secondary plant nutrients in soils as a result of sewage irrigation (Rattan et al., 2001). The objectives of this study were: (i) to study the chemical composition of sewage effluents emanating from KEIS and groundwater; (ii) to assess the effects of long-term irrigation with sewage effluents on metal contents in soils and plants; and (iii) to assess the risk of consuming leafy green vegetables in respect of their heavy metal contents grown on sewage-irrigated soils to human beings.
Section snippets
Study area and collection of samples
The study area is located in the western Delhi, India, where sewage effluents originating from Keshopur Sewage Treatment Plant have been used for irrigation purposes since 1979 (Fig. 1). Our study confined to six villages, viz. Nilothi, Mundka, Ranhola, Bakarwala, Hirankudna and Dichaonkalan covering 123, 233, 196, 775, 183 and 98 acres of agricultural lands, respectively. Agricultural lands of first four villages have been under sewage irrigation for 20 years, while in Hirankudna and
Physico-chemical properties of sewage effluents and groundwater
Plant nutrients and heavy metal contents in sewage effluents and groundwater samples of first sampling are presented in Table 1. Data for second, third and fourth sampling were not shown, since similar values of these elements were obtained except S. In first sampling, on an average, P, K, and S contents were 0.22, 3.58 and 14.3 mg L−1, respectively in groundwater samples, whereas, corresponding values for sewage effluents were 2.57, 11.7 and 15.9 mg L−1. Among these plant nutrients, sewage
Conclusions
From this study, it can be concluded that besides use as irrigation water, these sewage effluents are also a potential source of plant nutrients. Build-up of heavy metals, particularly Zn, Cu and Ni in sewage-irrigated soils needs to be monitored periodically in view of their significant accumulation in bioavailable pool associated with decline in pH. Appreciable depletion in available Mn under these intensively cultivated sewage-irrigated soils is likely to induce unsustainability in soil
Acknowledgement
Authors would like to place on record their sincere thanks to Indian Council of Agricultural Research, New Delhi, India for funding this study as a part of AP Cess Fund project.
References (47)
- et al.
Arsenic and heavy metal contamination of vegetables grown in Samta village, Bangladesh
Sci. Total Environ.
(2003) - et al.
Sewer water composition and its effect on soil properties
Bioresour. Technol.
(1998) Effect of soil pH on availability of metals in sewage sludge treated soils. II. Cadmium uptake by crops and implications for human dietary intake
Environ. Pollut.
(1994)- et al.
Predicting the activity of Cd2+ and Zn2+ in soil pore water from the radiolabile metal fraction
Geochim. Acta
(2003) - et al.
Post-irrigation impact of domestic sewage effluent on composition of soils, crops and ground water—a case study
Environ. Int.
(2002) - et al.
Accumulation and bioavailability of Zn, Cu, Mn and Fe in soils polluted with industrial waste water
J. Indian Soc. Soil Sci.
(1992) - et al.
Sewer water irrigation effects on some potentially toxic trace elements in soil and potato plants in northwestern India
Can. J. Soil Sci.
(2000) - CWC, 2000. Water and related statistics. Information Systems Organization, Water Planning and Organization Wing,...
- et al.
Effect of electrolytes coupled with variable stirring on soil pH
J. Indian Soc. Soil Sci.
(1997) - et al.
Effect of long-term application of sewage effluents on organic carbon, bioavailable phosphorus, potassium and heavy metals status of soils and uptake of heavy metals by crops
J. Indian Soc. Soil Sci.
(2000)
Irrigation with Treated Sewage Effluents: Management for Environmental Protection
Plant availability of heavy metals in soils previously amended with heavy applications of sewage sludge
J. Sci. Food Agric.
Modelling of Cd, Cu, Ni, Pb and Zn uptake, by winter wheat and forage maize, from a sewage disposal farm
Soil Use Manage.
Fractionation of copper and zinc in greenhouse soils
Soil Chemical Analysis
Forms of trace elements in soils, sediments, and associated water: An overview of their determination and biological availability
The solid solution equilibria of lead and cadmium in polluted soils
Eur. J. Soil Sci.
Asian Environ.
Fractionation, characterization and speciation of heavy metals in sewage sludge and sludge amended soils: a review
J. Environ. Qual.
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