1. Developing the Methods for Characterizing Complex Organic Matrix
 

Characterizing the complex organic matrix is an important step for understanding the changes of the organic matrix in response to natural and anthropogenic disturbances. Until now, numerous analytic techniques, such as EEM, GC/MS, NMR, and FT-ICR MS, have been developed for unveiling the composition of the organic matrix. However, in general, the techniques with high accuracy are expensive, while affordable techniques have low precision. One of my research objectives is to improve the precision of analytic techniques without an increase in cost. 

 

1.1 Pyrolysis GC/MS

 

PyGCMS is an analytic technique for characterizing the chemical composition in the complex organic matrix. The time and labor-intensive nature of manual peak identification and quantification prevent its wide application. We proposed a systematic approach for analyzing the PyGCMS data efficiently (Chen et. al., 2018 JAAP).

 

Source: Chen et. al., 2018 JAAP

2. Linking Water Quality to Terrestrial Ecosystem and Land Use

 

2.1 Wildland fire

 

Wildfire is a natural feature of Western North American forests, though the extent, frequency, and severity wildfires have increased in recent decades. It alters the quantity and chemical composition of SOM, and thus DOM after the erosions, which affects the water quality greatly.

 

We took the soil/ash samples from 2013 Rim Fire and found fire intensity as an important factor regulating the concentrations and profiles of polycyclic aromatic hydrocarbons (PAHs) in fire-affected soils (Chen et.al., 2018 ACS Earth Space Chem.).

Source: Chen et. al., 2018 ACS Earth Space Chem.

 

3. Studying the Sustainable Waste-to-Resource Approach

3.1 Hydraulic Fracturing

 

​Hydraulic fracturing is a technique promoting the exploitation of natural gas in the United States. It uses numerous chemicals (including toxic VOCs) as the hydraulic fracturing fluids. In my Ph.D. work on hydraulic fracturing, I used the online big dataset for water usage (Chen and Carter, 2016 JEM), organic inventory (Chen and Carter, 2017 JEM), emission of VOCs from the aqueous to the gas phase (Chen and Carter, submitted to EP), and occupational inhalation risk due to the VOC dispersions at the atmosphere (Chen and Carter, 2017 EP).

Source: Chen and Carter 2017, EP

3.2 Wastewater irrigation

Using treated wastewater to replace freshwater in agricultural irrigations can reduce the pressures of water scarcity. However, it will introduce the contaminants into agricultural soils and thus food crops.

 

We found more than half of each studied heavy metal(loid) (As, Cr, Cu, Ni, Pb, and Zn; 72.6-97.4%) was present in the residual fraction but only 13.3% of 120 soil samples with no potential adverse effect according to modified risk assessment code (Cao et. al., 2018 GEODERMA). Faster decomposition of roots relative to leaves in the field was due to more O-alkyl and less alkyl and aromatic carbon in the initial biochemical composition of roots (Cao et. al., 2018 STONE).

Source: Cao et. al., 2018 GEODERMA