海南岛新村、黎安潟湖表层沉积物有机质分布与来源分析

通过对海南省陵水县新村港(33个)和黎安港(11个)表层沉积物样品的粒度、总有机碳(TOC)、总氮(TN)的测定分析, 得出了双潟湖表层沉积物的粒径与有机质的分布特征, 并利用C/N 比值计算了不同有机质来源的贡献率。研究结果表明:1)新村港和黎安港潟湖表层沉积物的平均粒径分别为0~8ø和6~8ø, 呈由岸及湖心粒径逐渐减小的趋势; 2)新村港表层沉积物TOC的含量介于0.027 % ~2.660 %, 平均值为1.06 %, TN的含量介于0.018 % ~1.461 %, 平均值为0.748 %, 在人类活动明显的村落附近区域TN值很高, 去除人类活动影响的这些值后, TOC和TN的空间分布均与平均粒径具有较好的相关性, 即呈湖中心含量较高、近岸含量较低的特征; 黎安港表层沉积物TOC的含量介于0.216 % ~1.950 %, 平均值为1.15 %, TN的含量介于0.019 % ~1.460 %, 平均值为0.45 %, 由于沉积物粒径空间分异小, TOC和TN的空间分布较均匀; 3)新村港表层沉积物C/N 比介于0.037~33.000之间, 平均值为4.73, 利用C/N 比估算得到陆源有机碳贡献率达1 % ~99 %, 平均值为47 % 。C/N 比值和陆源有机碳贡献率在新村港南北两侧近岸表层沉积物中比潟湖中心高, 这是由于北侧河流和南侧南湾岭陡坡雨水携带的植物碎屑为近岸沉积物提供了较为丰富的陆源有机质; 黎安港表层沉积物C/N 比介于1.1~11.5之间, 平均值为6.51, 整体值小于12, 有机质的C/N 比与陆源有机质贡献率的空间分布与新村港存在较大差异, 其有机质主要为海源。人类活动对新村港内有机质沉积影响明显。

DISTRIBUTION PATTERNS OF SEDIMENTARY ORGANIC MATTER IN XINCUN AND LI-AN LAGOONS OF LINGSHUI COUNTY,HAINAN ISLAND AND THEIR SOURCE IMPLICATIONS

44 Surficial sediment samples were collected from the lagoons of Xincun and Li-An in Lingshui County, Hainan Island for analysis of grain size, total organic carbon(TOC), and total nitrogen(TN)(33 samples from Xincun Lagoon, 11 from Li-An Lagoon).The area of samples collection is situated among 18°24'~18°28'N and 109°58'~110°4'E with the water depth of 2~20m.The distribution characteristics of organic matters were obtained and the contribution from terrestrial organic matter were estimated by C/N.The results revealed as follows.(1)The lagoon sediments are mostly clay-silt.The average grain size was 0~8ø and 6~8ø respectively in Xincun and Li-An Lagoons.The grain size decreases gradually from the shoreline towards the lagoon center.(2)In the Xincun Lagoon, TOC ranges from 0.027 % to 2.660 %, with an average of 1.06 %.Likewise, TN ranges between 0.018 % and 1.461 %, with an average of 0.748 %.There are some stations with high TOC and TN content adjacent to villages, which may be related to human activities.The distributions of TOC and TN have a significant correlation with grain size, except for the values that are affected by human activities, with the features of higher content in the center of the lagoon and lower along the shoreline.At Li-An Lagoon, TOC ranges between 0.216 % and 1.950 %, with an average of 1.15 % ; TN ranges from 0.019 % to 1.460 %, with an average of 0.45 %.The spatial distributions of TOC and TN contents have a small change due to the less difference of grain size distribution pattern.(3)In the Xincun Lagoon, the sediment C/N ratios range among 0.037 and 33.000, with an average of 4.73.The contribution from terrestrial organic carbon(QC/N )estimated by C/N ratios varies from 1 % to 99 %, with an average of 47 %.These values suggest that the organic matter is a mixture of terrestrial and marine sources.The C/N ratio and QC/N are higher in the north and south along the shoreline of the lagoon, because the discharge of terrigenous organic matter is mainly from the small river in the north andrainoff transportation from Nanwan Hill in the south of the lagoon.In the Li-An Lagoon, the C/N ratios range among 1.1 and 11.5, with an average of 6.51.The overall C/N ratios are below 12, indicating that almost all organic matter is derived from the sea, which is quite different from the Xincun Lagoon.Human activities have an obvious impact on the sediment organic matter in the Xincun Lagoon.