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Abstract

The feathers of two Ardeid species, the Little Egret (Egretta garzetta) and the Black-crowned Night Heron (Nycticorax nycticorax) were collected from six egretries and two egretries respectively, located in different areas in the New Territories of Hong Kong, including the Mai Po Marshes (within a Ramsar site). These feathers were digested and concentrations (microg/g dry weight) of copper (4.6-19.4), iron (8.1-641.3), manganese (0.4-19.4), zinc (51.3-183.5), lead (0.1-5.1), cadmium (0.01-0.15), chromium (0.06-1.7) and mercury (0.0-7.1) were determined by ICP-AES, ICP-MS and CVAAS. The levels of manganese, mercury and lead found were equal to or less than the concentrations found in previous investigations, reflecting a slight downward trend most apparent with lead. As a general rule, the levels of lead and mercury were higher in the egretries close to the polluted Deep Bay. A probabilistic risk assessment of the possible adverse effects on the breeding success of the Little Egret was carried out with respect to mercury, lead and cadmium. It was concluded that mercury (0.5-7.1 microg/g dry weight feathers) probably has had adverse effects at the Au Tau egretry of the Little Egrets, but there was no evidence of adverse effects at other egretries. The probabilistic analysis also indicated a low likelihood of adverse effects of mercury on the breeding of the Black-crowned Night Herons at A Chau (0.3-1.2 microg/g) and Mai Po Village (0.0-1.4 microg/g). The evidence for the effects of lead and cadmium was limited but suggested there may possibly be adverse effects with lead but not cadmium.

Toxicity Reference Values and Tissue Residue Criteria for Protecting Avian Wildlife Exposed to Methylmercury in China

“…4 ). This result is in agreement with a previous risk assessment, in which Hg probably had an adverse effect on the breeding success of the little egret at this site (Connell et al 2001 ) . Although the concentration of Hg in little egret prey at Tai Lake exceeded both dietary-based TRCs, the level of Hg found in little egret feathers was less than the feather-based TRC.…”

“…Given that value, the TRC, based on concentrations expressed on a dry weight basis, would be 3.95 m g THg/g (dwt). Only the concentration of Hg in feathers of little egret from Au Tau in Hong Kong (Connell et al 2001 ) exceeded the TRC (Fig. 4 ).…”

Distribution patterns of toxic metals in the marine oyster Saccostrea cucullata from the Arabian Sea in Oman: spatial, temporal, and size variations

“…Large sized oysters contained concentrations of mercury similar to levels observed in small and medium sized oysters, suggesting similar regulating mechanisms of mercury in the tissues of oysters regardless of size. The high cadmium concentration of 6.1 mg kg -1 observed in small sized oysters during the months of September and October, in contrast to the relatively low concentrations observed in medium and large oysters, suggests that oysters in the medium and large size classes are sexually mature and have an efficient metabolism and detoxifying process (Connell et al 1999) to keep the concentration of metals relatively low. In contrast, Ferreira et al (2005) reported that the prior selection of the size of the individuals in the effect of size on heavy metal accumulations.…”

The Contamination Levels of Organochlorine Pesticides in Water and Sediment Samples in Uluabat Lake, Turkey

“…After understanding of their long term toxic effects, they were banned or severely restricted during the early 1970s in most of the developed countries. But usage of the OCPs for agriculture and malaria control has continued in some regions of the world (Connel et al, 1999). OCPs are particularly problematic because they are persistent, broad spectrum toxicants that tend to accumulate in the food web and have the potential to adversely affect ecosystem and human health.…”