Effects of Sewage Sludges Contaminated with Polychlorinated Dibenzo- p-dioxins, Dibenzofurans, and Biphenyls on Agricultural Soils ETHEL ELJARRAT, JOSEP CAIXACH, AND JOSEP RIVERA* Mass Spectrom etry Laboratory, Ecotechnologies Departm ent, C.I.D., C.S.I.C., Jordi Girona 18-26, 08034 Barcelona, Spain The fate of polychlorinated dibenzo- p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) in sewage sludges after agricultural application was analyzed. This study was based on the experiments designed for two soils with different agronomical characteristics after applying different rates of sewage sludge. The concentrations of PCDDs, PCDFs, and PCBs in soils were determined before and after the application of sewage sludges, and a general increase was observed with the applied rate, especially in the case of the PCDDs. The values of sludge-treated areas were 1.2-11.6times higher than the respective values of the noncontaminated areas. Changes observed in the ratio between PCDD and PCDF levels and in the isomeric distribution also suggest the influence of the sewage sludge on the soil. The values of sludge- treated areas were compared with the limits proposed in Germany for agricultural and horticultural land uses. The results of the soil investigation showed that, in the case of an initial soil with low contamination, the final soil did not exceed the limit; but, in the case of an initial soil with considerable contamination, the final soil exceed the limit, which restricts the cultivation of certain vegetables. Introduction A number of different directives concerning wastewater sewage sludges have been issued in the last decade. For instance, the promulgation of the Directive COM 91/271 on wastewater treatment requires the installation of treatment systems in allpopulations exceeding2000inhabitants before the year 2005 (1). Estimates for the year 2000 predict an increase in sewage sludge production of185%in Spain,which meansabout1milion ton/year. On theotherhand,theeffect ofsome new directives on treatment and elimination oftoxic and dangerous wastes, the EU Directive on agricultural use ofsludges (COM 86/ 278) (2),andthebanningofsewagesludge discharges into the sea from 1998 (1) all combine to restrict the final fate of sewage sludges. However, by the end of the millenium, there will be much more sludge and further restrictive environmental laws on their use and disposal. The application of sewage sludge to land is a widely practiced sludge management technique. In manycountries there is a continuous discussion on the significance ofsewage sludge fertilization of cultivated land in terms of soil contamination. In recent years, the recognition that sewage sludge contains organic pollutants, in particular PCDDs, PCDFs, and PCBs (3-8), has resulted in studies to identify the possible sources ofthese contaminants in sewage sludge and to assess the extent to which they may be transferred through the food chain and ultimately to humans. PCDDs and PCDFs in the sewage sludges may be attributed to different sources as (a) atmospheric deposition (9); (b) transformation of chlorinated organic precursors such as chlorophenols during treatment at wastewater plant (10- 12);(c)industrialdumps from textile,metal,pulp,and paper factories (13); (d) domestic wastewater (13); etc. The application of sewage sludges to soils is limited by guideline concentrations of heavy metals in the soil through the EU Directive on the use of sewage sludge in agriculture (COM 86/ 278) (2). No similar guidelines exist for organic contaminants in sludges or soils at present. The European Union iscurrentlystudyingthe issue and mayenact legislation on the application of sewage sludges containing PCDDs, PCDFs,and PCBs to agriculturalland. However,in Germany in 1992, the Ordinance on Sewage Sludge (14) established a limit of100pgofI-TEQ/gofsludge (dryweight,dw)forPCDDs and PCDFs and 200 ng/g of sludge (dw) for the six PCBs congeners (28, 52, 101, 138, 153, and 180) for agricultural purposes. Furthermore, this regulation set an application limit of 5 ton/ha within a period of 3 years. The purpose of this study was to assess the effects of PCDDs, PCDFs, and PCBs in sewage sludges applied to the soil. The work was based on an experiment devised during the 1980s. Two doses of sewage sludges were applied to two different soils for 4 consecutive years. The characterization ofthese soils before the experiment and after the application shows the fate of these contaminants from sewage sludge to the soil. Experimental Section Design ofExperiment. The samples used in this experiment are summarized in Table 1. Two different plots of land were selected for this study. Every plot was divided into 4 × 4 squares with subplots of 8 × 5m 2 . In the first plot, located in Caldes de Montbui (NESpain), the soilwas agronomically satisfactory, with a sandy loam texture, a basic pH, and an adequate organicmattercontent. Thissoilwascharacterized as a Xerochrept by the STS (Soil Taxonomy System). By contrast, in the second one, located in Tordera (NE Spain), the soil had a sandy texture, a slightly acid pH, and a poor nutrient and organic matter content, which indicates an agronomically deficient soil. Raygrass (Lolium westerwol- dicum var. Balwoltra) was planted as an annual on irrigated land. This variety was chosen given its high nutrient requirements for growing; for this reason, we were able to applyhigh levels ofsewage sludges and hence determine the effects produced in a shorter period of time. The applied sewage sludges were collected from the wastewater treatment plants located in the villages ofTossa, Figueres, and Roses (NE Spain). These plants treat sewage sludges, which are mainly of urban origin, aerobically. A smallindustrialinput existsat the Figueresplant,and a leisure boat marina input exists at the Roses plant. Two different rates of sewage sludges, a “low” dosis and a “high” doses (double the low doses), were applied. The application rates are summarized in Table 1. The differences between the amounts applied are due to the different characteristics and properties of each sewage sludge. The doses were calculated on the basis that approximately 20% of the total nitrogen present in the sewage sludge was mineralized in one agricultural cycle for the low dosis, and approximately 40% of the total nitrogen was mineralized for the high dosis. Thus, the sewage sludge with the highest nitrogen content required smaller rates of application. The doses commonly applied in spanish agriculture are much lower, ranging between 5 and 10 ton (dw) ha -1 year -1 . Environ. Sci. Technol. 1997, 31, 2765-2771 S0013-936X(96)01060-7 CCC: $14.00  1997 American Chemical Society VOL. 31, NO. 10, 1997 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 2765