JJWang's Biogeochemistry Group

Jun-Jian's Research Group will develop and apply cutting-edge and molecular-level natural organic matter and pollutant analyses, to elucidate the unknown responses of water and soil quality to critical natural and anthropogenic disturbances.RESEARCH GOAL:
The long-term goal of my research is to improve the fundamental understanding of soil and water chemistry in various ecosystems responding to natural and anthropogenic disturbances. Soil organic matter (SOM) and dissolved organic matter (DOM) represent the largest carbon (C) pools in terrestrial and aquatic environments and regulate the fate of pollutants, but their chemistry, stability, and fate with environmental change are still unclear. My short-term objectives include: 1) Elucidating shifts in SOM and metal biogeochemistry and soil microbial activity with long-term simulated environmental change; 2) Coupling the watershed DOM chemistry with water treatment technique to enhance drinking water quality; 3) Studying the plant fine root chemistry to unravel the belowground biogeochemical cycling at individual, ecosystem, and global scales.

1) SOM biogeochemistry with global environmental change
Soil plays a key role in C cycling because this pool contains more C than atmosphere and vegetation combined globally. Large uncertainty remains in the potential shift in SOM chemistry with global environmental change (urbanization, warming, increased atmospheric CO2, increased N deposition, wildfire, sea level rise, etc.), hindering the development of a reliable global carbon-climate model and the prediction of pollutant fate. In last decades, the traditional view of SOM was gradually shifted from the persistent humic substances to a continuum of progressively decomposing organic compounds, highlighting the necessity to understand the complex SOM composition at the molecular level. My research used biomarker analyses (carbohydrates, terpenoids, cutin, suberin, lignin, phospholipid fatty acids, etc.) and NMR techniques and revealed that 20 years of above-ground litter addition in the forest did not increase C storage because additional litter inputs advanced OM degradation[1]. Also, root exclusion for 20 years reduced the labile carbohydrate content and the microbial activity and increased the preservation of cutin- and suberin-derived compounds. We also revealed that 22 years of N amendment in a temperate forest shifted the microbial community and increased the soil C stock derived from cuticular and lignin[2].

2) DOM chemistry and water engineering
Clean water is a vital resource for global human health and economic development. Natural ecosystems such as forests in watershed play a key function to sustain water resource but are vulnerable to natural and anthropogenic disturbance. The DOM in source water is a known precursor to react with disinfectants to produce disinfection byproducts (DBPs: a class of carcinogenic pollutants). Understanding the DOM chemistry in watershed and its potential impact on the formation of carcinogenic chlor(am)inated DBPs is one emerging concern of drinking water supply. DOM from watershed could be derived from plants, soils, animals, microbes, and anthropogenic chemicals and subjected to different degrees of degradation/transformation before entering the water treatment plants[3],[4],[5]. My previous studies have demonstrated that both the bacterial planktonic cells and biofilms were important disinfection byproduct precursors that differed from humic acids or plant-derived organic matter. Their chlor(am)ine reactivity was highly dependent on bacteria species, phenotype, and pipeline materials. Yet, a linkage between disturbed forest dynamics and water quality is lacking.  With a good background in both forest science and environmental engineering, I am particularly interested in understanding how the natural and anthropogenic disturbances (e.g., fire, urbanization, and sea level rise) in forest dynamics affect the DOM-related surface water quality and potential drinking water quality and the efficacy of water treatment. Studying the 2013 California Rim Fire, the 3rd largest wildfire in California history (>100,000 ha in area, half the area of Shenzhen City; lasting for 3 months), we demonstrated that the fire temperature, oxygen availability, and fuel source interacted to change the chemistry of terrestrial dissolved organic matter, which led to stronger reactivity in the formation of potent emerging carcinogens (nitrogenous disinfection byproducts) in drinking water for the 2.6 million residents in/around San Francisco, the USA[6],[7],[8]. These studies link environmental changes with drinking water supplies and public health and provide helpful information for water supply management decision-makers in fire-prone regions.

3) Fine Root Chemistry
Elucidating root chemistry at individual, ecosystem, and global scales is essential in order to link root morphology to root function and to understand root evolution. Similar to SOM and DOM, fine roots are a very sensitive component to global changing climates, and their accurate turnover is still elusive, which results in much uncertainty when modeling global carbon, nitrogen, and water cycling. It has been increasingly recognized that the fine roots <2 mm are not a single pool due to their high heterogeneity based on branching order. Different from those of the ecologist pioneers, my studies focus on the molecular-level root organic[9],[10] and inorganic[11],[12] chemistry, as well as their environmental and ecological implications (such as soil remediation and C sequestration). We revealed that the most distal roots, compared to the higher-order roots, were critical in the trees’ detoxification of metal and SOM formation. Recently, one of my collaborative works with Dr. Deliang Kong highlights that variation of root morphology and root nitrogen concentration along the evolutionary gradient[13], and we proposed a nutrient absorption-transport hypothesis to drive root evolution[14].

[1] Wang JJ, Pisani O, Lin LH, Lun OOY, Lajtha K, Bowden RD, et al., STOTEN, 2017, 607, 865-875.
[2] Wang JJ, Bowden RD, Lajtha K, Washko SE, Wurzbacher SJ, Simpson MJ, Biogeochem, 2019, 142, 299–313.
[3] Wang JJ, Ng TW, Zhang Q, Yang XB, Dahlgren RA, Chow AT, et al. Biogeosci, 2012, 9, 3721-3727.
[4] Wang JJ, Liu X, Ng TW, Xiao JW, Chow AT, Wong PK, Water Res 2013, 47, 2701-2709.
[5] Wang JJ, Chow AT, Sweeney JM, Mazet JA, Water Res 2014, 59, 219-228.
[6] Wang JJ, Dahlgren RA, Ersan MS, Karanfil T, Chow AT. Environ Sci Technol 2015, 49, 5921-5929.
[7] Wang JJ, Dahlgren RA, Chow AT. Environ Sci Technol 2015, 49, 14019-14027.
[8] Wang JJ, Dahlgren RA, Ersan MS, Karanfil T, Chow AT, Water Res 2016, 99, 66-73.
[9] Wang JJ, Tharayil N, Chow AT, Suseela V, Zeng H, New Phytol 2015, 206, 1261-1273.
[10] Kong DL, Wang JJ, Kardol P, Wu HF, Zeng H, Deng XB, et al., Biogeosci 2016, 13, 415-424.
[11] Wang JJ, Guo YY, Guo DL, Yin SL, Kong DL, Liu YS, et al., Environ Sci Technol 2012, 46, 769-777.
[12] Guo YY, Wang JJ, Kong DL, Wang W, Guo DL, Wang YB, et al., Environ Sci Technol 2013, 47, 11465-11472.
[13] Kong DL, Wang JJ, Wu HF, Valverde-Barrantes OJ, Wang RL, Zeng H, et al. Nat Commun, 2019, 10, 2203.
[14] Kong DL, Wang JJ, Zeng H, Liu MZ, Miao Y, Wu HF, et al., New Phytol 2016, 213, 1569-1572.

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