Heavy-metal concentration in underground and surface water, soil, and crop plants growing in farmers' fields near the industrial city of Ludhiana, Punjab, India, that receive irrigation with water contaminated with sewer and untreated industrial effluents was studied. The concentrations of lead (Pb), chromium (Cr), cadmium (Cd), and nickel (Ni) in sewage-contaminated water were 18, 80, 88, and 210 times higher than in shallow handpump water, and 21, 133, 700, and 2200 times higher than in deep tube-well water, respectively. The concentrations of Cd and Ni in shallow handpump underground water were significantly higher than in deep tube-well underground water. The concentrations of Pb, Cr, Cd, and Ni in deep tube-well water were 0.017, 0.003, 0.0002, and 0.0002 mg L 21 , respectively. Soils irrigated with sewagecontaminated water had higher electrical conductivity, cation exchange capacity, organic carbon (C), and clay content but had lower pH and calcium carbonate content compared to soils irrigated with deep underground water. The concentrations of diethylenetriamine pentaacetic acid (DTPA) -extractable Pb, Cr, Cd, and Ni in soils irrigated with sewage-contaminated water were 1.8, 35.5, 3.6, and 14.3 times higher, and total concentrations of these heavy metals were 1.5, 3.0, 3.7, and 2.2 times higher than that in soils irrigated with deep underground water. The mean concentrations of Pb, Cr, Cd, and Ni in crop plants growing on soils irrigated with sewage-contaminated water were 4.88, 4.20, 0.29, and 3.99 mg kg 21 , which were 1.2, 2.1, 8.7, and 1.9 times higher than in plants irrigated with deep tube-well water, respectively. The amounts of potentially toxic metals were significantly and positively correlated with cation exchange capacity and organic C content and negatively correlated with soil pH. In conclusion, long-term accumulation of toxic metals in soils and their uptake by crop plants has a high potential for phytotoxicity as well as for entering into the food chain. The findings also suggest contamination of underground shallow drinking water through leaching of some highly mobile metals.

No abstract

. 2000. Sewage water irrigation effects on some potentially toxic trace elements in soil and potato plants in northwestern India. Can. J. Soil Sci. 80: 465-471. Sewage water is used for irrigation to improve crop yields, but it may affect the soil and crop quality. The effects of discharging the effluents of a leather complex on the concentrations of some potentially toxic elements (Cu, Fe, Mn, Zn, Al, As, Cr and Ni) in sewage water and the effects of irrigation with contaminated sewage water on the concentrations of these elements in soils and in potato (Solanum tuberosum L.) leaves and tubers were studied near Jalandhar city, Punjab, in northwestern India. Two treatments were 10 yr of irrigation with 300 mm of sewage water + 300 mm of ground water per annum (SW) and with 600 mm of ground water per annum (GW). Soils of the study fields were Typic Ustochripts with sandy to loamy sand texture. The concentrations of all elements except As increased following the addition of leather complex effluents in the sewage water, with the biggest increase in the concentration of Cr (from 2.7 mg to 14.0 mg Cr L -1 ). The SW treatment increased concentrations of all elements in soil except As, and the increase was significant to 60 cm depth for Fe, Mn, Zn, Al and Ni and to 30 cm depth for Cu and Cr. Irrigation with SW also increased the concentrations of these elements in potato leaves and tubers and the increase was generally higher in leaves than in tubers. The proportional increase of Cu, Fe, Zn and Al was less in plants than in soils, that of Mn and Cr was almost similar in plants and in soil, and that of Ni was more in plants than in soil. These elements, which accumulate in soils and crops, may become health hazards to humans and/or animals. Therefore, continued monitoring of the concentrations of potentially toxic elements in soil and plants and/or treatment of sewage water before using for irrigation is needed.

A glasshouse investigation was undertaken to evaluate the natural potential of fenugreek (Trigonella foenumgraecum L.), spinach (Spinacia oleracea L.), and raya (Brassica campestris L.) for cleanup of chromium (Cr)-contaminated silty loam and sandy soils. Four kilograms of soil per treatment in earthen pots was treated with five levels of chromium [0, 1.25, 2.5, 5.0, and 10.0 mg Cr kg 21 soil through dipotassium chromate (K 2 Cr 2 O 7 ], equilibrated for 21 days at field-capacity moisture content, and then fenugreek, spinach, and raya were grown for 60 days after seeding. The concentration of diethylene triamine pentaacetic acid (DTPA)-extractable Cr increased significantly with increasing rate of Cr application in both soils, but the increase was higher in sandy soil than in silty loam soil. The DTPA-extractable Cr in both soils decreased after harvesting of crops compared to its concentration in soil before sowing of the crops. The decrease in DTPA-extractable Cr concentration was highest in soil growing raya and least in the fenugreek-growing soil. The percent reduction in dry-matter yield (DMY) with increasing levels of added Cr in comparison to the zero-Cr control was highest for fenugreek (49 and 52%) followed by spinach (36 and 42%) and lowest for raya (29 and 34%) in silty loam soil and sandy soil, respectively. Also, the percent reduction in mean shoot yield of all crops was higher in sandy soil (41%) compared to silty loam soil (36%), when the rate of applied Cr was increased from 0 to 10 mg Cr kg 21 soil. The DMY of both shoot and root was highest for raya and lowest for fenugreek. The Cr concentration in fenugreek, spinach, and raya increased with increasing level of added Cr in both soils. The concentration of Cr in both shoot and root was highest in raya, followed by spinach and fenugreek. The overall mean uptake of Cr in shoot was almost four times and in root was about two times higher in raya compared to fenugreek. The findings indicated that family Cruciferae (raya) was most tolerant to Cr toxicity, followed by chenopodiacea (spinach) and Leguminosae (fenugreek). Because raya removed the highest amount of Cr from soil, it could be used for pytoremediation of mildly Cr-contaminated soils.

A pot experiment was conducted to investigate the influence of phosphate (P) application on diethylene triamine pentaacetic acid (DTPA)–extractable cadmium (Cd) in soil and on growth and uptake of Cd by spinach (Spinacia oleracea L.). Two soils varying in texture were contaminated by application of five levels of Cd (NO3)2 (0, 20, 30, 40, and 60 mg Cd kg–1). Three levels of KH2PO4 (0, 12, and 24 mg P kg–1) were applied to determine immobilization of Cd by P. Spinach was grown for 60 d after seeding. Progressive contamination of soils through application of Cd affected dry‐matter yield (DMY) of spinach shoot differently in the two soils, with 67% reduction of DMY in the sandy soil and 34% in the silty‐loam soil. The application of P increased DMY of spinach from 4.53 to 6.06 g pot–1 (34%) in silty‐loam soil and from 3.54 to 5.12 g pot–1 (45%) in sandy soil. The contamination of soils increased Cd concentration in spinach shoots by 34 times in the sandy soil and 18 times in the silty‐loam soil. The application of P decreased Cd concentration in shoot. The decrease of Cd concentration was higher in the sandy soil in comparison to the silty‐loam soil. Phosphorus application enhanced DMY of spinach by decreasing Cd concentration in soil as well as in plants. The results indicate that Cd toxicity in soil can be alleviated by P application.