Soil has always been the most complex biomaterial on the planet.
The rapid determination of the components in the soil and their original
source is a prerequisite for soil quality, environmental, and human
health risk assessments. In this study, the chemical compositions
and source apportionment of surface soil samples collected from five
sites in Shanghai, China, were successfully investigated using a laboratory-developed
laser ablation single-particle aerosol mass spectrometry (LA-SPAMS)
instrument combined with an adaptive resonance theory-based neural
network algorithm (ART-2a) data-processing method for the first time.
In total, more than 35,000 particles, ranging from 200 to 2000 nm,
were sized, and around 15–20% of the particles were chemically
analyzed by LA-SPAMS to generate both positive and negative mass spectra.
The results show that there are significant differences in particle
size distribution among the five samples, with peaks of various sizes
and different profiles, while all five soil samples contain crustal
elements, heavy metals, organic and inorganic components, and so forth.
The chemical composition of each sample varied considerably, so different
classes of SPAMS particle classes were identified, which were later
grouped into seven general categories: EC-rich (containing elemental
carbon), secondary components, organic nitrogen, crust, HM (containing
heavy metal), PAH (containing polycyclic aromatic hydrocarbons), and
NaK-rich particles, based on the dominant marked ions. The composition
analysis and source apportionment showed that soil components in different
areas have been affected by the local environment, such as local industrial
emissions and automobile exhaust, which are usually characterized
by varying degrees of mixing between the crust and environmental aerosols.
In combination with the ART-2a method, LA-SPAMS enables rapid and
direct analysis of soil samples based on real-time single-particle
measurements, which will help in understanding the distribution, transport,
and fate of the soil components, thus providing new insights into
soil-quality assessment. Moreover, the established LA-SPAMS can also
be practically applied to other daily inspection tasks, such as rocks,
minerals, metals, ceramics, polymers, and other solid materials for
ingredient analysis and quality evaluation.
