Accumulation of nutrients and heavy metals in surface sediments near Macao

The effects of water pollution on the accumulation of heavy metals and nutrients in sediments are examined. The contents of arsenic, cadmium, chromium, lead, total nitrogen and total phosphorus compounds in both aquatic and sediment phases are presented. The spatial distributions of sediment pollution are not completely dependent on the corresponding aquatic conditions. The enrichment of phosphorus in sediments is more obvious than that of nitrogen compounds. The content ratio of total phosphorus between two phases reaches 13 000. Although the concentrations of heavy metals in aquatic phase are low, due to the large content ratios which are, respectively, 9500, 14 000, 11 000 and 4600 for arsenic, cadmium, chromium and lead, their acumulations are significant. Among the four sediment fractions of different sizes (diameters: >0.125 mm, 0.063–0.125 mm, 0.045–0.063 mm and ≤0.45 mm), the contents of heavy metals are generally higher in the fractions of 0.045–0.063 mm and 0.063–0.125 mm.