Environmental and Ecological Risk Assessment of Trace Metal Contamination in Mangrove Ecosystems: A Case from Zhangjiangkou Mangrove National Nature Reserve, China

Table 2

Summary of trace metals concentrations in surface sediments of the ZMNNR.

	Time of sampling	Number of samplings	Concentrations (mg/kg)
			Cu	Cd	Pb	Cr	Zn	As	Hg
This study	2013	17	21.47 ± 2.23	0.064 ± 0.034	41.97 ± 4.09	38.11 ± 26.26	140.78 ± 10.25	24.73 ± 1.67	0.019 ± 0.019
		12	19.41 ± 3.73	0.076 ± 0.046	46.93 ± 7.10	19.55 ± 7.74	133.16 ± 8.61	25.55 ± 4.44	0.026 ± 0.019
Previous survey	2007	17	21.04 ± 6.13	0.336 ± 0.055	63.20 ± 3.04	61.50 ± 18.03	127.65 ± 4.74	14.29 ± 1.00	0.034 ± 0.026
Jingchun  et al., 2010 [35]	2004	7	30.28 ± 4.70	0.21 ± 0.03	53.91 ± 4.83	—	127.51 ± 13.92	—	—
		7	28.79 ± 5.59	0.30 ± 0.01	62.81 ± 9.44	—	143.96 ± 12.37	—	—
		7	36.42 ± 5.74	0.36 ± 0.08	70.09 ± 3.96	—	159.56 ± 9.88	—	—
Background			5.40	0.03	16.20	—	33.90	—	—
ISQG low			65	1.5	50	80	200	20	21
ISQG high			270	10	218	370	410	70	100

Data are means ± standard deviation of sites.
ISQG, Interim Sediment Quality Guidelines. The guidelines define the ISQG-high and ISQG-low values, which represent the lower 10th percentile and 50th percentile of chemical concentrations associated with adverse biological effects, based on the results of sediment toxicity testing [37].
The sampling sites in the intertidal zone.
The sampling sites in the subtidal zone.
The sampling sites in the mudflat.
The sampling sites in the forest edge.
The sampling sites in the forest.
The background levels of trace metals obtained from a subsample of 41 surface sediments in a location in continental shelf area of south Taiwan Strait.