Distribution Of Linear Alkyl Benzenes In The Intertidal Areas Of The Yellow River Delta

42 surface sediments (0～1 cm) were collected in September 2007, April 2008 and July 2008 and a length of 34 cm column sediments (cutting samples using 1, 2, 3 and 5 cm as unit from surface to bottom , a total of 14 samples) were collected in July 2008 in the intertidal areas of the Yellow River Delta. The distribution and degradation of linear alkyl benzenes (LABs) in surface and column sediments were studied, as well as the transportation and transformation in the intertidal areas and the impact of anthropogenic activities. A mixture of LABs (containing 1- Cn-LAB) was used as external standard and GC-MS was used for quantification and identification. Precision and accuracy were monitored by standard addition experiment and recovery experiments, respectively. The main results and conclusions were demonstrated as followed.1 The distributions of LABs in surface sedimentsC10-LAB, C11-LAB and C13-LAB dominated and ranged at 13 %～45 %,17 %～36 % and 9 %～37 % in spring, respectively. C12-LAB and C13-LAB dominated and ranged at 22 %～64 % and 12 %～39 % in summer, respectively. C13-LAB, C11-LAB and C10-LAB dominated and ranged at 14 %～50 %,22 %～35 % and 13 %～55 % in autumn, respectively. The total LABs in surface sediments ranged at 2.67 ng/g～11.67 ng/g (average 4.74 ng/g),4.00 ng/g～37.33 ng/g (average 16.75 ng/g) and 0.33 ng/g～11.00 ng/g (average 5.67 ng/g) in spring, summer and autumn. The concentrations in spring and autumn followed a similar pattern and were much lower than those in summer. The average LABs in surface sediments decreased from the south (12.24 ng/g) to the middle (10.31 ng/g) and to the north (6.87 ng/g), in which the average LABs in the south was two times as much as that in the north. Meanwhile, the LABs in surface sediments decreased as well from close estuary to far estuary, indicating a terrestrial input of LABs to the intertidal area. The result of LABs in the intertidal area of the Yellow River Delta was lower than those of most coastal waters in the world. The relative low population and industrialization, as well as the high deposition rate (up to 9 cm/a) in this study area might be responsible for the low LABs.2 Vertical distribution of LABs in column sediments C13-LAB and C12-LAB dominated and ranged at 18 %～30 % and 11 %～51 %, respectively. The species of LABs detected in column sediments were similar to that in the surface sediments. The LABs in column sediments were located at 5.67～79.67 ng/g, waving by depth. The highest concentration of 79.67 ng/g was located at the middle and lower and a higher concentration of 53.33 ng/g at the surface; the concentration of LABs in the middle were located at 5.67 ng/g～30.00 ng/g waving by depth and the lowest concentration were 5.67 ng/g appeared at the bottom. According to the deposition rate, the depths of 1～7, 7～16, 16～25 and 25～34 cm were corresponding with the periods from to January 2008 to July 2008, 2007, 2006, and 2005, with the total LABs of 123.00 ng/g, 107.00 ng/g, 109.00 ng/g and 11.33 ng/g, respectively. It was suggested that the amount of detergent in 2008 were higher than those in 2007 and 2006, that in 2007 was similar to that in 2006, and that in 2005 was the lowest. The total LABs in 2006 was 9.6 times as big as that in 2005. Meanwhile, the results showed that detergent amount significantly increased from 2005 to 2006.3 The degradation of LABsThe LABs in surface sediments in the south ranged from 11.67 ng/g to 6.67 ng/g in spring and from 7.33 ng/g to 0.67 ng/g in autumn, with a decreasing tendency from near shore to off shore areas. The LABs in surface sediments in the middle section ranged from 5.00 ng/g to4.22 ng/g in spring, from 37.33 ng/g to 16.89 ng/g in summer and from 11.00 ng/g to 0.33 ng/g in autumn, respectively, with a decreasing tendency from near shore to off shore areas either. The distributions of LABs in north areas were symmetrical. The LABs distribution tendency indicated a degradation gradually from near shore to off shore areas. The LABs isomers were different among sites. 2- Cn-LAB, 3- Cn-LAB dominated, while 5- Cn-LAB and 6- Cn-LAB were lower. The ratio of internal and external isomers of n- C12-LAB was designated as I/E, and the I/E value represented the degree of LAB degradation. It was estimated that the 15.00 %～53.65 % (averaged at 37.58 %) LABs were degraded when reaching the intertidal sediments. This is agreed with those in the Pearl River Delta, Victoria Harbor and Boston Harbor. The degradation ratio of LABs suggested that the domestic sewage discharged in this region was basically without treating or poorly treated, and thus the discharge of urban sewage was one of the important sources of water pollution.4 Factors on the distribution of LABs LABs, POC and grain size were irrelevant by linear relationship analysis in the intertidal areas of the Yellow River Delta. It was suggested that the grain size was not the primary factor impacting on the distribution of LABs, but the high deposition rate (up to 9 cm/a) in this study area was responsible for the low LABs in surface sediments and the high LABs in close estuary. The deposition rate and terrestrial input were the most potential factors on the distribution of LABs.