录取学校：Columbia University Ph.D. in Earth and Environmental Sciences 

基本情况：江同学，北京大学，化学，GPA 3.6，TOEFL 103，GRE 319 

Because my career objective is to do research in the field of environment, I am applying for your Ph.D. in Earth and Environmental Sciences program in your Department of Earth and Environmental Engineering. My plan is to acquire advanced knowledge of environmental science and engineering, first at the master's level to set my research direction, and then at the doctoral level to put forward new parametric models and theories to push the field forward. 

In July 2021, I participated in the Global Research Experience in Advanced Technologies (GREAT) Program jointly organized by Peking University and UC Davis. During the two months, I have consulted with many professors about the respectable American universities in the research of environmental health, pollution and climate risk, they suggest me consider Columbia. After careful research on your website, I found that the research in Environmental Health Engineering and Water Resources and Climate Risks at the Department of Earth and Environmental Engineering are very suitable for me to continue my research in environmental governance. The research environment in your department offers outstanding faculties and facilities which will help me prepare to be a researcher. Meanwhile, I can get to know the latest developments and theories in the field and hone my research skills with experienced professionals. In the future, studying in the Columbia will lead me to be able to offer better suggestions for the policy making of environmental improvement based on concrete findings from the laboratory. 

Research Interests 

The macro orientation of my interested research comprises the problems of environment related to health and economy, including the influence of air, water and other environmental systems on human health and, more broadly, on society and economy. While the micro orientation of my research at present is (1) the ingredients of atmospheric particulates and their toxicity in the human body and (2) searching for alternatives of certain pesticides, the macro orientation is critical because these problems are all closely related to our daily life and are issues that people pay attention to. With the constant renewal and development of new material technology, the related environmental problems are growing, with air pollution becoming serious enough in recent years that even the government has attached importance to fixing the problem. If breakthrough developments can be achieved on these aspects, it can greatly improve people’s livelihood, which is my biggest hope and ultimately guides my research. 

With regards to my specific research interest areas, I am most interested in using environmental models to study air and water pollutants and their related environmental influences. Especially for some tough environmental issues, such as energy utilization and water resource pollution, we can give better guidance to people to treat these problems through introducing and adjusting accurate environmental models. Besides this, I am curious about the treatment of environmental problems produced by nanotechnology, the environmental problems of energy, and so on. My final research interest area is in the chemical behaviors of the pollutants, especially the related chemical kinetics processes during the formation, movement, situation and transportation of pollutants in air and water because this aspect is closely related to environmental treatment options. If we can know the various changing processes of the pollutants, we can effectively control or prevent their formation and spread. Together and separately, researching these topics will contribute to improved understanding of environmental problems and solutions, and improved environmental policy making. 

Research Plan 

Although there has been a lot of research done on the components of atmospheric particulates, there is not a good bridge between the chemical components and their toxicity. In spite of the fact that the sources of particulates can be analyzed and identified through the model of the chemical ingredients, it is usually difficult for people to connect these sources with effective policies that would reduce their emission and thus lessen their harm to the human body. This is partially because there is not a good understanding of the relationship between particulates' ingredients and their toxicity. Therefore, this research is very necessary to environmental management and making effective policy. 

Because of this, my plan in graduate study has two main aspects. The first is research on environmental toxicity, including the toxicity of atmospheric particulates on the human body and the residual pesticide toxicity in soil. The second is further study on some innovative pretreatments for environmental samples and how we can use analytical chemistry and environmental science research methods to determine them. Along with this research, I also plan to gain advanced knowledge in environmental economics and link my scientific research to concrete environmental treatment options. 

The details of my topics mainly focus on the following: 

• Quantitative analysis of toxic pollutants; 

• Analysis, detection and toxicity research of micro-pollutants in soil, air and water; 

• Research on the mutualistic effect on organisms of different pollutants; 

• Research on the influence of new pollutants caused by new materials or new technologies; 

• Research on how to make target objects easily determinable when testing by using new pretreatment methods for different environmentalsamples (such as atmospheric samples); 

• Environmental policy-making and environmental economics. 

Research Experience 

During my undergraduate period, I participated in four main research projects. 

The first was a study of the characteristics and toxicity of the atmospheric particulates in different places in China. In this research, my main work was to measure the toxicity of different particulates through cell experiments. In this process, I learned various experimental methods and some related instruments of cell experimentation, including flow cytometry and microplate readers. Then I analyzed the toxicity of the particulates by myself and set the foundation for future related research. When doing cell experiments, I found out that they do not compare well to chemical experiments with regards to preparation. Instead, a large number of samples needed to be made every time for horizontal comparison, rather than my being able to draw hasty conclusions by using only vertical comparison of each batch of cells. The quantitative features of cell experiments were also bad; though we could see the difference of the toxicity, we could not quantify the degree of the particulates' toxicity according to the measured ROS, inflammatory factor or cell mortality rate. This also increased the difficulty of studying the relationship between the ingredients and their toxicity. In order to facilitate the analysis, I tried to build a function model on the parameters of each batch of cells and the exposure concentration of the particulates, so as to measure the toxicities of different concentrations of one sample, but I found out that cells of different generations do not lend themselves to a quantitative relationship between concentration and toxicity. Thus, the method of mathematic modeling was unusable. 

These gains led me to independently design my second experiment, making comparisons between a newly designed thermal precipitator and the traditional filter collector. In this study, we developed the thermal precipitator, a promising particle collector, and compared its features with the traditional filter collector. During the research, I took charge of comparing the particulates' properties between the two devices and measuring the toxicity of particulates from each. In this experiment, I learned the basic methods for chemical research of atmospheric environment, such as how to collect atmospheric particulates and how to analyze chemical elements; at the same time, I learned some methods for dealing with statistical issues and learned statistical software R. Our findings showed that the thermal precipitator could avoid the defects of the traditional filter collector regarding the distribution of the particulates and maintenance of their features. This research required a great deal of independent thinking and problem solving. The best example of this was when I found out that the newly designed thermal precipitator still had many defects, the most important of which was solving the problem of the low flow rate and particulates' size distribution. The size distribution of the collected particulates depended highly on the flow rate, so the rate had to be stable at a certain value. And because the temperature appeared in an even gradient in the vertical direction, it resulted in too many particles at the front end of the precipitator and too few particles at the back end, meaning there was too little differentiation of particles. Therefore I developed a method using the even change of the temperature in the vertical axial direction to secondarily separate the particles. Through the layered and cylindrical thermal precipitator, the temperature differences between the cold plate and hot plate in each layer led to differential movement of the particulates; therefore, the part with the small temperature difference mainly gathered superfine particulates, while the part with big temperature difference mainly gathered fine particulates. In this way, we acquired the desired effect. 

This year has included two more projects. From March to June 2021, I worked in the State Key Laboratory of Environmental Chemistry and Ecotoxicology, where I participated in scientific research related to environmental sample pretreatment. During the three months, I studied many instrumental analysis methods, such as XPS, MALDI-TOF, multi-channel ICP-MS, and FTIR etc. Not only have I learned the application and principles of these instruments, but it also made me deeply understand how to represent different issues through various analysis methods. It has contributed to improvement in my experimental design and given me various analytical chemistry methods to draw from when I encounter problems with my experimental results. 

From July to September 2021, I conducted research in UC Davis on alternatives for chlorpyrifos in California. My three main jobs were collecting literature and refining data, building a database, and analyzing the acquired data through meta-analysis. Chlorpyrifos is a widely used pesticide, especially in California, but it has high environmental risks, so looking for its alternatives has become very important. There are two criteria for a feasible alternative; the first is its efficacy cannot be lower than chlorpyrifos, the other is it should possess lower environmental risks. In order to get more accurate and effective results about these factors, data needed to be integrated from large amount of literature. We collected 96 studies from the last 10 years that included quantized efficacy comparisons between chlorpyrifos and other pesticides. Then we entered the acquired data into the computer and set up a database with the efficacy comparisons. After this, we conducted a meta-analysis using software R to get a series of potential candidates so we could compare the environmental risks and get a realistic series of promising alternatives.

Through this project, I gained the following beneficial skills and knowledge. First is an understanding of the research approaches of environmental modeling, which can provide definitive results by collecting and dealing with large amounts of information. Second, I have become more adept at collecting and processing information from different sources. Finally, I am now able to deal with large amounts of data and can use the related statistical analytical methods. A secondary benefit was that my English scientific research writing ability improved due to several oral presentations and the final poster. 

Academic Preparation 

As my main major is chemistry, my professional courses were not closely related to environment, especially the atmospheric environment; however, I have taken additional courses to supplement my chemistry studies. Specifically, I selected some graduate courses related to environment, biology and statistics, including courses on applied mathematical statistics and aerosol principle and technology. I have earned good marks in these courses and built strong relationships with my professors. 

My laboratory work has also helped to prepare me for understanding and applying various techniques for atmospheric environmental research. The experimental method mainly includes sample collection, treatment and analysis, followed by statistical treatment. I also picked up some biological experimental methods on measuring toxicity from my cell experiments. Due to my major, I had conducted all kinds of chemical experiments, so learning related methods and gaining basic knowledge of cell experiments was valuable for me to be able to conduct environmental science experiments by myself. 

In related experience, in spring 2021, I served as the teaching assistant of an important compulsory course of undergraduate in the College of Chemistry, Chemistry Today. Taking this job not only improved my professional ability, but also improved my ability to communicate and express difficult concepts in a simple way. In my free time, I downloaded and read literature related to environmental science. By comparing the idea and methods of the literature, I got to know some cutting-edge research results and learned some ideas and methods of experimental design from them. Reading the literature also made me familiar with professors in the field and set good foundation for my scientific research in the future. 

Career Objectives 

In the next 5-10 years, I hope to become a professional talent in environmental science and engineering. My studies to date have been incredibly interesting, so I am sure that will continue to motivate my future research in graduate school. After finishing my doctorate, I will come back to work in a Chinese university, teaching and engaging in laboratory research that will influence environmental policy makers. Because my dream is to make outstanding contributions to environmental development and treatment and make people have a better life, I am encouraged to pursue this related research at the highest level. 

To realize this goal, I have to complete graduate studies. I know that the education and research quality of American universities are rather high, and there were many professors and graduates with a high level of knowledge in the environmental field when I was at UC Davis. I expect that learning from them and communicating academic questions with them can greatly improve my level in this field. Of course, my professional knowledge in the related field also needs to be accumulated, and I plan to increase that through my coursework, research and professional affiliations. Searching for related materials and becoming informed about the large amount of literature related to environment can deepen my understanding about the research methods in environmental field; meanwhile, I can find out what problems have not been researched well. Based on this, I can design experiments to conduct research according to my own thoughts, or even come up with new environmental analytical models or new research methods. All these activities are oriented toward and support my future career goal.