To improve the efficiency of TiO₂ as a photocatalyst for contaminant degradation, a novel nanocomposite catalyst of (N, Fe) modified TiO₂ nanoparticles loaded on bentonite (B-N/Fe-TiO₂) was successfully prepared for the first time by sol-gel method. The synthesized B-N/Fe-TiO₂ catalyst composites were characterized by multiple techniques, including scanning electron microscope (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), X-ray fluorescence (XRF), nitrogen adsorption/desorption, UV-Vis diffuse reflectance spectra (DRS), and electron paramagnetic resonance (EPR). The results showed that bentonite significantly enhanced the dispersion of TiO₂ nanoparticles and increased the specific surface area of the catalysts. Compared with nondoped TiO₂, single element doped TiO₂, or unloaded TiO₂ nanoparticles, B-N/Fe-TiO₂ had the highest absorption in UV-visible region. The photocatalytic activity of B-N/Fe-TiO₂ was also the highest, based on the degradation of methyl blue (MB) at room temperature under UV and visible light irradiation. In particular, the synthesized B-N/Fe-TiO₂ showed much greater photocatalytic efficiency than N/Fe-TiO₂ under visible light, the newly synthesized B-N/Fe-TiO₂ is going to significantly increase the photocatalytic efficiency of the catalyst using sun light.

The fluorine content of coal has been well documented, while such data of coal spoil are limited. In the present paper, fluorine in coal spoils and its releasing behavior were studied via leaching and combustion tests, as well as field investigation. Fluoride pollution in groundwater and soil occurred in the air depositing areas of coal spoils. The average content of fluorine in coal spoils was 525mg/kg with the highest value of 1885mg/kg. The only XRD detectable inorganic fluorine phase was fluorphlogopite. The absence of major fluorine bearing minerals in coal spoils suggested that bulk fluorine, rather than trace phases, resided in the mineral matrix. The major extracted species were water soluble fluorine and exchangeable fluorine in the coal spoils. Batch leaching tests illustrated that the leachable fluoride in coal spoils was widely distributed, ranging from 2.0 to 108.4mg/kg. Column leaching tests showed a clear pH-dependent leaching behavior of fluorine: lower pH situation led to fluorine release from the mineral matrix; the loosely bound or easily exchangeable fluorine was also flushed out of the column. The higher ion strength or alkaline bicarbonate/carbonate rich leaching solution tended to free more fluorine into the acidic aqueous solution. The leachable fluorine in coal spoils was estimated as ca. 6%, based on the results of leaching tests. Also, our research found that over 90% of fluorine in coal spoils could be released into the atmosphere as a result of spontaneous combustion, accounting for over 40% of the total atmospheric fluorine emissions in northern China. Our investigation suggests that it is urgent to conduct comprehensive studies to assist the management and control of fluorine pollution at coal spoil banks.

{ Barium sulfate (BaSO4) is a common scale-forming mineral in natural and engineered systems, yet the rates and mechanisms of heterogeneous BaSO4 nucleation are not understood. To address these, we created idealized interfaces on which to study heterogeneous nucleation rates and mechanisms, which also are good models for organic–water interfaces: self-assembled thin films terminated with different functional groups (i.e., −COOH, −SH, or mixed −SH & COOH) coated on glass slides. BaSO4 precipitation on coatings from Barite-supersaturated solutions (saturation index

The formation of (Fe, Cr)(OH)3 nanoparticles determines the fate of aqueous Cr in many aquatic environments. Using small-angle X-ray scattering, precipitation rates of (Fe, Cr)(OH)3 nanoparticles in solution and on quartz were quantified from 0.1 mM Fe(III) solutions containing 0–0.25 mM Cr(III) at pH = 3.7 ± 0.2. Concentration ratio of aqueous Cr(III)/Fe(III) controlled the chemical composition (x) of (Fex, Cr1–x)(OH)3 precipitates, solutions’ supersaturation with respect to precipitates, and the surface charge of quartz. Therefore, the aqueous Cr(III)/Fe(III) ratio affected homogeneous (in solution) and heterogeneous (on quartz) precipitation rates of (Fex, Cr1–x)(OH)3 through different mechanisms. The sequestration mechanisms of Cr(III) in precipitates were also investigated. In solutions with high aqueous Cr(III)/Fe(III) ratios, surface enrichment of Cr(III) on the precipitates occurred, resulting in slower particle growth in solutions. From solutions with 0–0.1 mM Cr(III), the particles on quartz grew from 2 to 4 nm within 1 h. Interestingly, from solution with 0.25 mM Cr(III), particles of two distinct sizes (2 and 6 nm) formed on quartz, and their sizes remained unchanged throughout the reaction. Our study provided new insights on homogeneous and heterogeneous precipitation of (Fex, Cr1–x)(OH)3 nanoparticles, which can help determine the fate of Cr in aquatic environments.

Microscopic understanding of interaction between H2O and MAPbI3 (CH3NH3PbI3) is essential to further improve efficiency and stability of perovskite solar cells. A complete picture of perovskite from initial physical uptake of water molecules to final chemical transition to its monohydrate MAPbI3·H2O is obtained with in situ infrared spectroscopy, mass monitoring, and X-ray diffraction. Despite strong affinity of MA to water, MAPbI3 absorbs almost no water from ambient air. Water molecules penetrate the perovskite lattice and share the space with MA up to one H2O per MA at high-humidity levels. However, the interaction between MA and H2O through hydrogen bonding is not established until the phase transition to monohydrate where H2O and MA are locked to each other. This lack of interaction in water-infiltrated perovskite is a result of dynamic orientational disorder imposed by tetragonal lattice symmetry. The apparent inertness of H2O along with high stability of perovskite in an ambient environment provides a solid foundation for its long-term application in solar cells and optoelectronic devices.

Understanding the interactions between natural organic matter (NOM) and zero-valent iron nanoparticles (nano-Fe0) and magnetite nanoparticles (nano-Fe3O4) is essential for evaluating their performance in pollutant remediation, as well as determining their fate and transport in the environment. Batch experiments were performed to investigate the sorption/desorption behaviors of humic acid (HA) on commercially available nano-Fe0 and nano-Fe3O4. The sorption/desorption of HA on nano-Fe0 and nano-Fe3O4 were well described by both the Langmuir model and the modified Langmuir model. The adsorption capacities of HA were 8.77 ± 0.31 mg C/g and 10.05 ± 0.95 mg C/g for nano-Fe0 and nano-Fe3O4, respectively. The interactions of HA with nano-Fe0 and nano-Fe3O4 were highly pH-dependent. On one hand, nano-Fe0 had its maximum adsorption of 11.0 mg C/g HA at pH = 3, which decreased to 0.6 mg C/g when pH increased to 11.9; on the other hand, alkaline condition enhanced HA desorption greatly. At pH = 10.1, after 24 h desorption experiments, nearly 80% of initially adsorbed HA desorbed from the nanoparticles. The interactions of HA with nano-Fe0 and nano-Fe3O4 were also influenced by different ion compositions in solution. Divalent cations (e.g. Ca2+, Mg2+) enhanced HA adsorption significantly, while phosphate nearly eliminated HA adsorption and promoted significantly HA desorption.

Fe(III) hydroxide nanoparticles are an essential carrier for aqueous heavy metals. Particularly, iron hydroxide precipitation on mineral surfaces can immobilize aqueous heavy metals. Here, we used grazing-incidence small-angle X-ray scattering (GISAXS) to quantify nucleation and growth of iron hydroxide on quartz in 0.1 mM Fe(NO3)3 solution in the presence of Na+, Cu2+, Pb2+, or Cr3+ at pH = 3.7 ± 0.1. In 30 min, the average radii of gyration (Rg) of particles on quartz grew from around 2 to 6 nm in the presence of Na+ and Cu2+. Interestingly, the particle sizes remained 3.3 ± 0.3 nm in the presence of Pb2+, and few particles formed in the presence of Cr3+. Quartz crystal microbalance dissipation (QCM-D) measurements showed that only Cr3+ adsorbed onto quartz, while Cu2+ and Pb2+ did not. Cr3+ adsorption changed the surface charge of quartz from negative to positive, thus inhibiting the precipitation of positively charged iron hydroxide on quartz. Masses and compositions of the precipitates were also quantified. This study provided new insights on interactions among quartz, iron hydroxide, and metal ions. Such information is helpful not only for environmental remediation but also for the doping design of iron oxide catalysts.

Heterogeneous coprecipitation of iron and aluminum oxides is an important process for pollutant immobilization and removal in natural and engineered aqueous environments. Here, using a synchrotron-based small-angle X-ray scattering technique, we studied heterogeneous nucleation and growth of Fe(III) (hydr)oxide on quartz under conditions found in acid mine drainage (at pH = 3.7 ± 0.2, [Fe3+] = 10–4 M) with different initial aqueous Al/Fe ratios (0:1, 1:1, and 5:1). Interestingly, although the atomic ratios of Al/Fe in the newly formed Fe(III) (hydr)oxide precipitates were less than 1%, the in situ particle size and volume evolutions of the precipitates on quartz were significantly influenced by aqueous Al/Fe ratios. At the end of the 3 h experiments, with aqueous Al/Fe ratios of 0:1, 1:1, and 5:1, the average radii of gyration of particles on quartz were 5.7 ± 0.3, 4.6 ± 0.1, and 3.7 ± 0.3 nm, respectively, and the ratio of total particle volumes on quartz was 1.7:3.4:1.0. The Fe(III) (hydr)oxide precipitates were poorly crystallized, and were positively charged in all solutions. In the presence of Al3+, Al3+ adsorption onto quartz changed the surface charge of quartz from negative to positive, which caused the slower heterogeneous growth of Fe(III) (hydr)oxide on quartz. Furthermore, Al affected the amount of water included in the Fe(III) (hydr)oxides, which can influence their adsorption capacity. This study yielded important information usable for pollutant removal not only in natural environments, but also in engineered water treatment processes.

To predict the fate of aqueous pollutants, a better understanding of heterogeneous Fe(III) (hydr)oxide nucleation and growth on abundant mineral surfaces is needed. In this study, we measured in situ heterogeneous Fe(III) (hydr)oxide nucleation and growth on quartz, muscovite, and corundum (Al2O3) in 10–4 M Fe(III) solution (in 10 mM NaNO3 at pH = 3.7 ± 0.2) using grazing incidence small-angle X-ray scattering (GISAXS). Interestingly, both the fastest heterogeneous nucleation and slowest growth occurred on corundum. To elucidate the mechanisms, zeta potential and water contact angle measurements were conducted. Electrostatic forces between the charged Fe(III) (hydr)oxide polymeric embryos and substrate surfaces—which affect local saturations near the substrate surfaces—controlled heterogeneous growth rates. Water contact angles (7.5° ± 0.7, 22.8° ± 1.7, and 44.8° ± 3.7 for quartz, muscovite, and corundum, respectively) indicate that corundum has the highest substrate–water interfacial energy. Furthermore, a comparison of structural mismatches between the substrates and precipitates indicates a lowest precipitate–substrate interfacial energy for corundum. The fastest nucleation on corundum suggests that interfacial energies in the solution–substrate–precipitate system controlled heterogeneous nucleation rates. The unique information provided here bolsters our understanding of nanoparticle–mineral surface interactions, mineral surface modification by iron oxide coating, and pollutant transport.

The precipitation of carbonate minerals—mineral trapping—is considered one of the safest sequestration mechanisms ensuring long-term geologic storage of CO2. However, little is known about the thermodynamic factors controlling the extent of heterogeneous nucleation at mineral surfaces exposed to the fluids in porous reservoirs. The goal of this study is to determine the thermodynamic factors controlling heterogeneous nucleation of carbonate minerals on pristine quartz (100) surfaces, which are assumed representative of sandstone reservoirs. To probe CaCO3 nucleation on quartz (100) in solution and with nanoscale resolution, an in situ grazing incidence small-angle X-ray scattering technique has been utilized. With this method, a value of α′ = 36 ± 5 mJ/m2 for the effective interfacial free energy governing heterogeneous nucleation of CaCO3 has been obtained by measuring nucleation rates at different solution supersaturations. This value is lower than the interfacial energy governing calcite homogeneous nucleation (α ≈ 120 mJ/m2), suggesting that heterogeneous nucleation of calcium carbonate is favored on quartz (100) at ambient pressure and temperature conditions, with nucleation barriers between 2.5% and 15% lower than those expected for homogeneous nucleation. These observations yield important quantitative parameters readily usable in reactive transport models of nucleation at the reservoir scale.

For sustainable geologic CO2 sequestration (GCS), a better understanding of the effects of brine cation compositions on mica dissolution, surface morphological change, and secondary mineral precipitation under saline hydrothermal conditions is needed. Batch dissolution experiments were conducted with biotite under conditions relevant to GCS sites (55–95 °C and 102 atm CO2). One molar NaCl, 0.4 M MgCl2, or 0.4 M CaCl2 solutions were used to mimic different brine compositions, and deionized water was used for comparison. Faster ion exchange reactions (Na+–K+, Mg2+–K+, and Ca2+–K+) occurred in these salt solutions than in water (H+–K+). The ion exchange reactions affected bump, bulge, and crack formation on the biotite basal plane, as well as the release of biotite framework ions. In these salt solutions, numerous illite fibers precipitated after reaction for only 3 h at 95 °C. Interestingly, in slow illite precipitation processes, oriented aggregation of hexagonal nanoparticles forming the fibrous illite was observed. These results provide new information for understanding scCO2–brine–mica interactions in saline aquifers with different brine cation compositions, which can be useful for GCS as well as other subsurface projects.

For sustainable geologic CO2 sequestration (GCS), it is important to understand the effects of temperature and CO2 pressure on mica’s dissolution and surface morphological changes under saline hydrothermal conditions. Batch experiments were conducted with biotite (Fe-end member mica) under conditions relevant to GCS sites (35–95 °C and 75–120 atm CO2), and 1 M NaCl solution was used to mimic the brine. With increasing temperature, a transition from incongruent to congruent dissolution of biotite was observed. The dissolution activation energy based on Si release was calculated to be 52 ± 5 kJ mol–1. By comparison with N2 experiments, we showed that CO2 injection greatly enhanced biotite’s dissolution and its surface morphology evolutions, such as crack formation and detachment of newly formed fibrous illite. For biotite’s dissolution and morphological evolutions, the pH effects of CO2 were differentiated from the effects of bicarbonate complexation and CO2 intercalation. Bicarbonate complexation effects on ion release from biotite were found to be minor under our experimental conditions. On the other hand, the CO2 molecules in brine could get into the biotite interlayer and cause enhanced swelling of the biotite interlayer and hence the observed promotion of biotite surface cracking. The cracking created more reactive surface area in contact with brine and thus enhanced the later ion release from biotite. These results provide new information for understanding CO2–brine–mica interactions in saline aquifers with varied temperatures and CO2 pressures, which can be useful for GCS site selection and operations.

Early stage amorphous precursors provide a low energy pathway for carbonate mineralization. Many natural deposits of carbonate minerals and biogenic calcium carbonate (both amorphous and crystalline) include significant amounts of Mg. To understand the role of magnesium-containing amorphous precursors in carbonate mineralization, we investigated the energetics and structure of synthetic amorphous Ca–Mg carbonates with composition Ca1−xMgxCO3·nH2O (0⩽x⩽1) using isothermal acid solution calorimetry and synchrotron X-ray scattering experiments with pair distribution function (PDF) analysis. Amorphous magnesium carbonate (AMC with x=1) is energetically more metastable than amorphous calcium carbonate (ACC with x=0), but it is more persistent (crystallizing in months rather than days under ambient conditions), probably due to the slow kinetics of Mg2+ dehydration. The Ca1−xMgxCO3·nH2O (0⩽x⩽1) system forms a continuous X-ray amorphous series upon precipitation and all intermediate compositions are energetically more stable than a mixture of ACC and AMC, but metastable with respect to crystalline carbonates. The amorphous system can be divided into two distinct regions. For x=0.00–0.47, thermal analysis is consistent with a homogeneous amorphous phase. The less metastable compositions of this series, with x=0.0–0.2, are frequently found in biogenic carbonates. If not coincidental, this may suggest that organisms take advantage of this single phase low energy amorphous precursor pathway to crystalline biogenic carbonates. For x⩾0.47, energetic metastability increases and thermal analysis hints at nanoscale heterogeneity, perhaps of a material near x=0.5 coexisting with another phase near pure AMC (x=1). The most hydrated amorphous phases, which occur near x=0.5, are the least metastable, and may be precursors for dolomite formation.

The simultaneous homogeneous and heterogeneous precipitation of hydrous Fe(III) oxides was investigated in the presence of environmentally ubiquitous anions (nitrate, chloride, and sulfate). Experiments were conducted with 10–4 M Fe(III) at acidic pH (pH = 3.7 ± 0.2), which often occurs at acid mine drainage sites or geologic CO2 storage aquifers near injection wells. Quartz was used as a model substrate for heterogeneous precipitation. Small angle X-ray scattering (SAXS) and grazing incidence SAXS (GISAXS), atomic force microscopy (AFM), and dynamic light scattering (DLS) measurements were conducted. In situ SAXS/GISAXS quantified the size, total particle volume, number, and surface area evolutions of the primary nanoparticles formed in the nitrate and chloride systems. In both systems, the heterogeneously precipitated particles were smaller than the homogeneously precipitated particles. Compared with chloride, the volume of heterogeneously precipitated hydrous Fe(III) oxides on the quartz surface was 10 times more in the nitrate system. After initial fast heterogeneous nucleation in both nitrate and chloride systems, nucleation, growth, and aggregation occurred in the nitrate system, whereas Ostwald ripening was the dominant heterogeneous precipitation process in the chloride system. In the sulfate system, fast growth of the heterogeneously precipitated particles and fast aggregation of the homogeneously precipitated particles led to the formation of particles larger than the detection limit of GISAXS/SAXS. Thus, the sizes of the particles precipitated on quartz surface and in solution were analyzed with AFM and DLS, respectively. This study provides unique qualitative and quantitative information about the location (on quartz surfaces vs in solutions), size, volume, and number evolutions of the newly formed hydrous iron oxide particles in the presence of quartz substrate and ubiquitous anions, which can help in understanding the fate and transport of pollutants in the environment.

Particle Exposure Assessment for Community Elderly (PEACE) in Tianjin, China was to characterize personal PM10 exposure, and provide data support for an epidemiological study investigating potential health effects of PM pollution on Chinese elderly population. In this study, a total of 80 elderly participants were recruited for a two-consecutive-day personal exposure measurement, and simultaneously residential indoor, residential outdoor and community PM10 were monitored in the summer and winter of 2009. Personal PM10 concentrations were 192.8 ± 100.6 μg m−3 in summer and 154.6 ± 105.4 μg m−3 in winter. Modeled personal exposures were less than measured personal exposures while a high coefficient of determination (R2) of 0.71 was obtained. Based on measured and modeled exposures, a mean personal cloud of 30.2 μg m−3 was estimated in summer and 16.5 μg m−3 in winter. Moderate correlation emerged between personal and community PM10 concentrations in summer (r = 0.39), and stronger correlation was found in winter (r = 0.82). Analysis of variance (ANOVA) shown that smoking, cooking and cleaning activities did not produce significant effect on personal exposures. Further more, multivariate regression analysis performed in this study revealed that community PM10 level contributed most of personal PM10 exposure, 32% in summer and 64% in winter, respectively. The findings of this study indicated that PM10 personal exposures were considerably influenced by outdoor particulate matter rather than typical indoor sources, and ambient PM10 level measured at community monitoring sites may be used as a surrogate of personal exposure to PM10.

To safely implement geologic carbon sequestration (GCS), a better understanding of geochemical reactions at supercritical CO2 (scCO2)–brine–clay mineral interfaces is necessary. This work investigated phlogopite dissolution and secondary mineral formation after freshly cleaved (001) surfaces were exposed to scCO2–brine systems. Phlogopite was used as a model clay mineral, and scCO2–1 M NaCl–phlogopite systems at 75 °C and 75 atm were chosen to mimic CO2 storage conditions in deep saline aquifers. Additional experiments were also performed at 95 °C to explore the effect of temperature on phlogopite dissolution. The dissolution activation energies for each element were calculated to be 64.2 kJ mol−1 for Si, 53.6 kJ mol−1 for Mg, and 78.4 kJ mol−1 for Al. Over 43 h of reaction time, the activation energy for K dissolution was calculated to be 35.9 kJ mol−1. A whole-mineral activation energy for phlogopite, 62.5 kJ mol−1, was estimated from the weighted mean values of the activation energies of the framework elements (Al, Si, and Mg). Swelling of the phlogopite outer layers, dissolution pit formation, and precipitation of both illite and amorphous silica were dominant at both temperatures. At 75 °C, normalized volumetric surface coverage (μm3/μm2) was 0.34 ± 0.74 for illite and 0.05 ± 0.90 for amorphous silica nanoparticles.

To ensure safe and efficient geologic CO2 sequestration (GCS), it is crucial to have a better understanding of CO2–brine–rock interactions under GCS conditions. In this work, using biotite (K(Mg,Fe)3AlSi3O10(OH,F)2) as a model clay mineral, brine-biotite interactions were studied under conditions relevant to GCS sites (95 °C, 102 atm CO2, and 1 M NaCl solution). After reaction for 3–17 h, fast growth of fibrous illite on flat basal planes of biotite was observed. After 22–70 h reaction, the biotite basal surface cracked, resulting in illite detaching from the surface. Later on (96–120 h), the cracked surface layer was released into solution, thus the inner layer was exposed as a renewed flat basal surface. The cracking and detachment of the biotite surface layer increased the surface area in contact with solution and accelerated biotite dissolution. On biotite edge surfaces, Al-substituted goethite and kaolinite precipitated. In control experiments with water under the same temperature and pressure, neither macroscopic fibrous illite nor cracks were observed. This work provides unique information on biotite-brine interaction under acidic hydrothermal conditions.

Volatile Organic Compounds (VOCs) exposure can induce a range of adverse human health effects. To date, however, personal VOCs exposure and residential indoor and outdoor VOCs levels have not been well characterized in the mainland of China, less is known about health risk of personal exposure to VOCs. In this study, personal exposures for 12 participants as well as residential indoor/outdoor, workplace and in vehicle VOCs concentrations were measured simultaneously in Tianjin, China. All VOCs samples were collected using passive samplers for 5days and were analyzed using Thermal Desorption GC-MS method. U.S. Environmental Protect Agency's Inhalation Unit Risks were used to calculate the inhalation cancer health risk. To assess uncertainty of health risk estimate, Monte Carlo simulation and sensitivity analysis were implemented. Personal exposures were greater than residential indoor exposures as expected with the exception of carbon tetrachloride. Exposure assessment showed modeled and measured concentrations are statistically linearly correlated for all VOCs (P<0.01) except chloroform, confirming that estimated personal exposure using time-weighted model can provide reasonable estimate of personal inhalation exposure to VOCs. Indoor smoking and recent renovation were identified as two major factors influencing personal exposure based on the time-activity pattern and factor analysis. According to the cancer risk analysis of personal exposure, benzene, chloroform, carbon tetrachloride and 1,3-butadiene had median upper-bound lifetime cancer risks that exceeded the U.S. EPA benchmark of 1 per one million, and benzene presented the highest median risks at about 22 per one million population. The median cumulative cancer risk of personal exposure to 5 VOCs was approximately 44 per million, followed by indoor exposure (37 per million) and in vehicle exposure (36 per million). Sensitivity analysis suggested that improving the accuracy of exposure measurement in further research would advance the health risk assessment.

A monitoring program of particulate matter was conducted at eight sampling sites in four highly industrialized cities (Shenyang, Anshan, Fushun, and Jinzhou) of Liaoning Province in Northeast China to identify the major potential sources of ambient PM2.5. A total of 814 PM2.5 and PM2.5–10 samples were collected between 2004 and 2005. All PM samples were collected simultaneously in four cities and analyzed gravimetrically for mass concentrations. A sum of 16 elemental species concentrations in the PM samples were determined using inductively coupled plasma atomic emission spectroscopy. Annual means of PM2.5 concentrations ranged from 65.0 to 222.0 μg m−3 in all the eight sampling sites, and the spatial and seasonal variations were discussed. Enrichment factors were calculated, and Cr, Cu, Zn, As, Cd, and Pb will be pollution-derived elements. Site-to-site comparisons of PM2.5 species in each city were examined using coefficient of divergence, revealing that the two sites in each city are similar in elemental species. Principle component analysis was used for preliminary source analysis of PM2.5. Three or four factors in each city were isolated, and similar sources (crustal source, coal combustion, vehicle exhaust, iron making, or some other metallurgical activities) were identified at four cities.

Comprehensive evaluation of the water environment for effective water quality management is complicated by a considerable number of factors and uncertainties. It is difficult to combine micro-evaluation with the macro-evaluation process. To effectively eliminate the subjective errors of the traditional analytic hierarchy process (AHP), a new modeling approach—the analytic hierarchy process and grey target theory (AHP-GTT) systematic model—is presented in this study to evaluate water quality in a certain watershed. A case study of applying the AHP-GTT systematic model to the evaluation and analysis of the water environment was conducted in the Yibin section of the Yangtze River, China. The micro-evaluation is based on defining the weights of indices of the water quality (IWQ) of each water cross-section, while the macro-evaluation is based on calculating the comprehensive indices of water environmental quality and analyzing the tendency of the water environment of each cross-section. The results indicated that the Baixi and Shuidongmen sections are seriously polluted areas, with the tendencies of becoming worse. Also, the key IWQs of these two cross-sections are 5-day biochemical oxygen demand and chemical oxygen demand of permanganate, respectively.