武汉东湖沉积物碳氮磷垂向分布研究

Vertical distribution of carbon, nitrogen and phosphorus of sediments at Stations Ⅰ and Ⅱ in Lake Donghu, Wuhan

建立了东湖Ⅰ站90cm和Ⅱ站150cm沉积物剖面年代序列框架,研究了碳氮磷的垂向分布,并对碳-氮和碳-磷耦合进行了讨论。东湖Ⅰ站和Ⅱ站沉积物总有机碳(TOC)分别为3.00%和2.44%,总氮(TN)分别为0.45%和0.34%,总磷(TP)分别为1.11mg/g和0.69mg/g。东湖Ⅰ站和Ⅱ站沉积物TOC与TN之间呈极显著的正相关关系,TOC/TN质量比的变化是受到气候变化、人类活动、氮比有机碳分解速度快等因素综合作用的结果。TP与TOC之间也呈正相关关系,但相关性差,由于污水大量排入Ⅰ站,导致东湖Ⅰ站TOC/P质量比明显低于Ⅱ站,表层沉积物中磷比碳降解速度快导致TOC/P质量比升高。

Two undisturbed sediment cores of 95 cm and 150 cm at the Stations Ⅰand Ⅱin Lake Donghu, Wuhan, were collected respectively. Environmental 210Pb, 137Cs, 14C AMS dating techniques were applied to determine the ages. Furthermore, the distributions of TC, TIC, TOC, TN and TP in the sediments were analyzed. The carbonnitrogen and carbonphosphorus couplings in the sediments were studied tentatively as well. The results show that at StationsⅠand Ⅱin Lake Donghu, contents of TOC are 3.00%(ranging from 0.78%to 5.04%) and 2.44%(ranging from 0.81%to 5.35%), TN are 0.45%(0.18%to 0.63%) and 0.34%(0.16%to 0.63%), and TP are 1.11 mg/g (0.50 to 1.70 mg/g) and 0.69 mg/g (0.49 to 1.34 mg/g), respectively. At StationⅠand Ⅱin this lake, TC and TOC decrease with depth simultaneously, because TOC comprised over 90%of TC. While, TIC, accounting for only a small percent of TC, fluctuated greatly in the upper 30 cm of the surface layer.TOC, TN and TP of sediments at station Ⅰwere obviously greater than those at Station Ⅱ. The differences of TC, TN and TP between the surface layer and substrate of sediments at station Ⅰwere greater than those at station Ⅱ, and the fluctuations of TC, TN and TP in the surface layer of sediment were greater than those in the substrate. Although TC, TN and TP of sediments increased in the surface layer, they did not increase simultaneously.There is an obvious positive correlation between TOC and TN. The changes of TOC/N mass ratios was the result of climate changes, anthropogenic activities, the faster decomposition of nitrogen as compared with organic carbon and so on.Although there was a positive correlation between TOC and TP, the correlation was not excellent. The TOC/P mass ratios of sediments at station Ⅰwas smaller than those at station Ⅱdue to heavy sewerage discharge at station Ⅰ. An increasing trend of TOC/P mass ratios in the surface layer was the results of the preferential decomposition of phosphorus in contrast with organic carbon.