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Wastewater is increasingly being used to irrigate agricultural land in many countries around the world. However, limited research has examined the occurrence of antibiotics in soil irrigated with wastewater and their accumulation in plants. This study aimed to determine the distribution of various types of antibiotics in different environmental matrices in the Pearl River Delta (PRD) region and to evaluate their accumulation and translocation in edible crops. Samples were collected from six sites in the PRD where either domestic wastewater or fishpond water was used for irrigation. Results showed that fishpond water irrigated soils had higher concentrations of antibiotics than wastewater-irrigated soils. Different trends were observed in the accumulation of antibiotics in the different edible parts of various crops. Despite the low human annual exposure to antibiotics through the consumption of edible crops (1.10 to 7950 μg/y), the potential adverse effects of antibiotics along the food chain should not be neglected.

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ABSTRACT/Landfill leachates were collected and their chemical properties analyzed once every two months over a ten-month period from the Gin Drinkers' Bay (GDB) and Junk Bay (JB) landfills. The contents of solids, and inorganic and organic components fluctuated considerably with time. In general, the chemical properties of the two leachates correlated negatively (P < 0.05) with the amounts of rainfall prior to the sampling periods. However, magnesium and pH of the leachates remained relatively constant with respect to sampling time. The JB leachate contained higher average contents of solids and inorganic and organic matter than those of GDB with the exception of trace metals. Trace metals were present in the two leachates in trace quantities (<1.0 mg/liter). The concentrations of average ammoniacal nitrogen were 1040 and 549 mg/liter, while chemical oxygen demand (COD) values were 767 and 695 mg/liter for JB and GDB leachates, respectively. These results suggest that the leachates need further treatment before they can be discharged to the coastal waters.One of the constaints of successful treatment of landfill leachate is the difficulty in identifying and quantifying its typical characteristics. The chemical properties of leachate samples from different sanitary landfills vary widely and are affected by the amount, composition, and moisture content of the refuse; hydrogeology and climate of the site; age and height of the landfill; and season of the year (Chian and DeWalle 1976, Uloth andMavinic 1977). Furthermore, leachate composition is influenced by sampling methods and factors affecting leachate flow, such as dilution with rainfall or groundwater, and decontamination of leachate during passage through soil (Boyle and Ham 1974). The design of a leachate treatment system for a particular landfill site may require extensive characterization for the leachate. For instance, an activated sludge plant for a small landfill in Dorset, England, which was designed for leachate with a biochemical oxygen demand (BOD) up to 1900 mg/liter and ammonia (NH3) up to 250 mg/liter, treated leachate with a BOD of about 150 mg/liter and NH3 con-