Environmental nanoparticles found in soil systems and biosolids may pose a considerable risk to groundwater quality as contaminant carriers. Little effort has been invested in the characterization of natural nanocolloids compared to corresponding macrocolloids. This study involved physicochemical, mineralogical, and morphological characterizations of nanocolloids and macrocolloids fractionated from three Kentucky soils and one biosolid. Particle size and morphology were investigated using scanning/transmission electron microscopy and dynamic light scattering. Mineralogical composition was determined by X-ray diffraction and thermogravimetric and Fourier-transform infrared spectroscopy analyses. Zeta potentials and cation exchange capacities assessed surface charge and chemical reactivity. The estimated average hydrodynamic diameter of nanoparticles was nearly twice the ideal 100 nm range, apparently due to irregular particle shapes and partial aggregation. Nanoparticles were also found attached to surfaces of macrocolloids, forming macro-nano aggregates and obscuring some of their physical and chemical characteristics. However, nanocolloids exhibited greater surface reactivity, likely due to their smaller size, poor crystallinity, and morphological shape distortions. In spite of some behavior modification due to nanoaggregation phenomena, nanocolloids appeared to be much more potent vectors of contaminant transport in subsurface environments than their macrosize fractions. Nevertheless, their heterogeneous nature brings to light important considerations in addressing pollution prevention and remediation challenges.
Limited information exists on natural nanocolloid sorption behavior of As, Se, Cu and Pb in the environment. They are expected to have variable competitive sorption characteristics depending on size and composition and may transport elevated contaminant loads into surface and ground waters. A comprehensive characterization of their interactions with contaminants could provide a better understanding of the risks they pose to the environment. This study evaluated the sorption behavior of soil and biosolid nano-and macro-colloids with different mineralogical compositions for As, Se, Cu, and Pb contaminants. Single-and multi-contaminant Freundlich isotherms were used to evaluate sorption affinity for the contaminants among the different colloid sizes and compositions. Sorption trends based on size indicated greater affinity for As and Cu by the smectitic and kaolinitic nanocolloids, greater affinity for Pb by the kaolinitic nanocolloids, and greater affinity for As, Se and Pb by bio-nanocolloids over corresponding macrocolloid fractions. Both, single-and multi-contaminant isotherms indicated sorption preferences for cation over anion contaminants, but with somewhat contrasting sequences depending on size and composition. Multi-contaminant isotherms generally predicted greater sorption affinities likely due to bridging effects, particularly for anionic contaminants. Surface properties such as zeta potentials, cation exchange capacity (CEC), surface area (SA), organic carbon (OC), and OC:SA significantly but variably affected sorption characteristics among the differing colloid sizes and compositions. Colloid zeta potential and pH shifts in the presence of different contaminant loads suggested prevalence of inner sphere bonding mechanisms for sorption of cation contaminants by mineral colloids and outer sphere sorption for cation and anion contaminants by bio-colloids.
Influence of Clay Mineralogy on Soil Dispersion Behavior and Water Quality Jessique L. Ghezzi Currently, there is very little research available on nonpoint source pollution from rural watersheds. Government regulatory agencies are desperate for information regarding the causes of nonpoint source pollution, which includes the relationship between suspended soil particles and dispersion. Since soil dispersion is dependent on clay mineralogy, knowing the clay mineralogy of the soil in an area can help predict sediment loads entering the surrounding surface waters. This information is necessary to protect the resource value of our rivers, lakes, and estuaries, as well as to protect recreational activities such as fishing or hunting; but most importantly, this information is necessary to ensure the safety of our drinking water supply. Clay mineralogy and its influence on dispersion, as well as dispersion and its relation to water quality are the focus of this study. Soil mineralogy affects water quality in several ways: soil mineralogy determines the dispersivity of the clay portion of the soil and dispersive clays are likely to end up as suspended sediment in surface waters; weathering reactions contribute elements to water as dissolved load, and the sorption properties of clay minerals contribute to soils' ability to filter and carry pollutants. Through the use of X-ray diffraction, dispersivity, atomic absorption spectrometry, cation exchange capacity, and petrographic microscopy, this study shows that the clay mineral fraction of a soil determines the dispersivity, and that dispersed clay minerals contribute excess nutrients and metals as nonpoint source pollutants to surface waters.v ACKNOWLEDGEMENTS
A proper curriculum vitae (CV) is imperative to early career members, and surprisingly, there aren't many resources available to guide people through the development process. Anyone entering the job market should have both an academic and an industry-based CV that they can tailor to job applications. Academic CVs are drastically different than industry CVs in content and organization. Academic CVs are divided into two subcategories: research-based positions and teaching-based positions. Meanwhile, industry CVs are amplified resumes tailored to the specific needs of the job application.An academic CV serves many purposes. First, and most likely, it serves as a synopsis of your qualifications for the academic position you are applying for, but it can also be a synopsis of your accomplishments for a current academic position for promotion purposes. Basic content for either application generally follows the following format:• Name and current contact information • Email, phone, and address • Rank: highest degree/position currently held and your area of specialization • Educational background • Degrees awarded, year awarded, and granting institution(s) • Employment record • Position title, institution/company name, and years of employment • Professional recognition • Awards and honors • Professional memberships and service • Societies • Institutional activities (i.e., student fee committee or early career member committee and optionally, a brief description of your role) • Workshops and in-service training; for example, workshops you've attended or hosted or certifications you hold • Teaching responsibilities • Course name, units, and brief course description • Research • List general synopsis of projects (optional) • Publications • Research grants • A brief list of technical skills (optional)How you organize your CV depends on the position for which you are applying. For example, in academia, if you are applying for a position that is 70% research, you would list your research section prior to your teaching section. The opposite holds true if you are applying for a position that has 70% teaching responsibilities. The CV differs when you are applying for an industry position. Industry will want some explanations of your duties at each of your positions of employment. Additionally, some government agencies will want to see the following information for each position held: salary and basis of salary (hourly, yearly), hours per week worked, as well as the name and contact information of your supervisor. The teaching section should be condensed for an industry CV into bullets under the job description and reworded to apply to the job for which you are applying. Don't Overlook the LetterAn often overlooked area for a CV is the letter of intent (academia) or the cover letter (industry). This is the gateway for your CV and your first opportunity to sell yourself into getting someone in HR to look at your CV. If poorly done, this is often times the reason why your CV won't see the light of day. The letter of intent/cover lett...
Due to their enhanced stability and contaminant transport potential, environmental nanoparticles derived from soil and biosolid materials may pose a considerable risk to groundwater quality. Very little information exists on the stability and transportability of environmental or natural nanocolloids in the presence of As, Se, Pb and Cu contaminants, all of which are considered to represent substantial threats to human and animal populations through groundwater contamination. This study involved stability settling experiments of nanocolloids (NCs) (<100 nm) and macrocolloids (MCs) (100-2000 nm) fractionated from Bt horizons of three Kentucky soils and one biosolid waste material in water suspensions of 0, 2, and 10 mg•L −1 of As, Se, Pb and Cu. The results indicated greater stability in the mineral than the biosolid colloid fractions, and enhanced stability of NCs over corresponding MCs in the presence or absence of contaminants at low contaminant loads. At high contaminant loads nearly all colloids were unstable except for the bio-nanocolloids which still sustained considerable stability. At low contaminant loads, the MC fraction stability sequence was smectitic > mixed > kaolinitic > biosolid. Among the nano-fractions, the smectitic and kaolinitic colloids demonstrated lower stability than the MCs, but higher than those of the mixed and biosolid fractions. Physicochemical characterizations indicated that extensive organic carbon surface coatings and higher Al/Fe:Si ratios may have induced higher stability in the NC fractions, but their overall stability may also have been hindered in some cases by nano-aggregation phenomena.
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