a 南京大学 地球科学与工程学院




发布时间:2011-07-06 浏览次数:3705



Increasing magnetic susceptibility of the suspended particles in Yangtze River
and possible contribution of fly ash

Research highlights:
? The magnetic susceptibility (MS) of river sediment is a strong function of
grain size. ? The MS of the suspended particles in Yangtze River increase
over the past decades. ? The increasing MS is caused by anthropogenic
pollution of fly ash. ? MS can be used as a dating tool for the recent
sediments of Yangtze River. ? MS of Yangtze River sediment can monitor the
overall fly ash emission of China.

The magnetic properties of soil have been increasingly applied as a rapid and
economic way to monitor environment pollution. Sediments from a growing islet
in the lower reach of Yangtze River as well as the suspended particles in the
surrounding river water were used to identify anthropogenic influence on the
magnetic susceptibility (MS) of the Yangtze River sediment. Results show that
newly deposited sediments in 2004 have significantly higher MS (~ 150 × 10−8
m3 kg−1) on average than that of the ancient deposit (~ 50 × 10−8 m3 kg−
1). Scanning electron microscope (SEM) of the extracted magnetic particles
from newly deposited sediments and fly ash samples indicates large
contribution of fly ash for the samples with elevated MS. Dependence of MS on
grain size is evident, which enable calculation of the MS of suspended
particles from river sediment. A value of 32 × 10−8 m3 kg− 1is inferred for
the suspended particles in ancient Yangtze River. The records from 2004 to 20
10 indicate progressive increase in the MS of the suspended particles in
Yangtze River from 67 to 96 × 10−8 m3 kg− 1, which is much higher than that
of the ancient. Mass balance calculation based on the increasing MS suggests
that at least 7% of the fly ash produced within the catchment of Yangtze River
was released into the environment.