To reclaim a limestone quarry, 200 and 400 Mg/ha of municipal sewage sludge were mixed with an infertile calcareous substrate and spread as mine soil in 1992. Soil samples were taken 1 week later and again after 17 yr of mine soil rehabilitation so as to assess changes in the amount and persistence of soil organic carbon (SOC). Sludge application increased SOC as a function of the sludge rate at both sampling times. Seventeen years after the sludge amendments, the nonhydrolysable carbon was increased in the 400 Mg/ha of sludge treatment. The recalcitrance of SOC was less in sludge-amended soils than in the control treatment at the initial sampling, but 17 yr later this trend had reversed, showing qualitative changes in soil organic carbon. The CO 2 -C production had not differed between treatments, yet the percentage of mineralized SOC was less in the high sludge dose. When the size of active (C active ) and slow (C slow ) potentially mineralizable C pools was calculated by curve fitting of a double-exponential equation, the proportion of C active was observed to be smaller in the 400 Mg/ha sludge treatment. Soil aggregate stability, represented by the mean weight diameter of water-stable soil aggregates, was significantly greater in mine soil treated with the high dose of sludge (18.5%) and SOC tended to be concentrated in macro-aggregates (5-2 mm). Results suggest that SOC content in sludge-amended plots was preserved due by (i) replacement of the labile organic carbon of sludge by more stable compounds and (ii) protection of SOC in aggregates.

The presence of unacceptable levels of veterinary drug residues in animal-derived food is a global concern due to its negative impacts on human health. This study reports the occurrence and levels of two fluoroquinolone antimicrobialsenrofloxacin and ciprofloxacin-in broiler meat sold in Sri Lanka. A total of 129 broiler meat samples were purchased from the market, representing nine large-scale broiler meat processors (107 samples in 66 batches, branded) with an islandwide distribution and 22 small-scale processors (22 samples, unbranded). Enrofloxacin and ciprofloxacin in breast muscle were extracted following a previously published method with modifications and were subjected to High-Performance Liquid Chromatography with Fluorescence Detection analysis for the quantification of antimicrobials. Enrofloxacin residues were detected in 67 (51.9%) samples, out of which 28 had quantifiable levels (1.7-578.6 μg kg -1 ), whereas ciprofloxacin was detected in only nine samples. Only three samples (2.3%) exceeded the European Union maximum residue limit of 100 μg kg -1 for the sum of ciprofloxacin and enrofloxacin in poultry muscle. These three samples had enrofloxacin in 130.3-578.6 μg kg -1 range and ciprofloxacin in 15.7-28.8 μg kg -1 range. Mean enrofloxacin level in other samples was 5.9 ± 5.3 µg kg -1 . This study shows the widespread use of enrofloxacin in broiler meat industry in the country and the possibility of meat with harmful levels of residues entering the market. Thus, we highlight the need to establish regulations and a national-level veterinary drug residue surveillance program for animal-derived foods including broiler meat to ensure consumer safety.

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