[Dual-Perspective Analysis of the Warming Effect of the Methane Emissions from Animal Husbandry in China].

Accurate quantitative evaluation of the greenhouse effects of methane(CH4) is the foundation for developing effective mitigation strategies. This study was the first to quantitatively evaluate the warming effects of the CH4 emissions from animal husbandry in China using the recently proposed climate metric GWP-star(GWP*), which is designed for short-lived climate pollutants(SLCP), and to compare the results with the commonly used climate metric global warming potential(GWP). The results showed:CH4emissions from animal husbandry in China decreased from 957.0×105 t in 2000 to 764.0×105 t. The GWP results showed that the greenhouse effect of CH4 emissions from animal husbandry in China was increasing between 2015 and 2019, and the GWP* results showed that it decreased compared to that 20 years ago. The amount of reduction was equivalent to removing the warming of 2.1×108 t of carbon dioxide. Under the GWP evaluation system, achieving carbon neutrality in the livestock industry in China requires eliminating or offsetting stable annual CH4 emissions from increased carbon sinks. Instead, under the GWP* evaluation system, China's livestock industry could achieve its carbon neutrality in the short term by effectively reducing CH4 emissions by only 0.3% per year. In the case that the livestock industry in China continues to take effective emission reduction measures, the reduction target under the GWP* metric will be reached earlier than that under GWP. Still, the choice of GWP or GWP* requires careful consideration of the objectives of evaluation, the time scale of assessment, and practical operability.

MOF-derived bimetallic coordination polymer@cobalt-aluminum layered double hydroxide for highly selective CO2 adsorption: Experiments, mechanisms.

Selective capture of CO2 is one of the most effective strategies for combating the greenhouse effect. In this study, we report the synthesis of a novel adsorbent-an amine-based cobalt-aluminum layered hydroxide with a hafnium/titanium metal coordination polymer (denoted as Co-Al-LDH@Hf/Ti-MCP-AS)-through the derivatization of metal-organic frameworks (MOFs) for selective CO2 adsorption and separation. Co-Al-LDH@Hf/Ti-MCP-AS achieved the maximum CO2 adsorption capacity of 2.57 mmol g-1 at 25 °C and 0.1 MPa. The adsorption behavior followed the pseudo-second-order kinetics and Freundlich isotherm models, indicating that chemisorption occurs on a non-homogeneous surface. Co-Al-LDH@Hf/Ti-MCP-AS also exhibited selective CO2 adsorption in CO2/N2 and excellent stability over six adsorption-desorption cycles. An in-depth analysis of the adsorption mechanism through X-ray photoelectron spectroscopy and density-functional theory and frontier molecular orbital calculations revealed that adsorption occurs through acid-base interactions between amine functional groups and CO2 and that the tertiary amines (N3) have the highest affinity toward CO2. Our study provides a novel strategy for designing high-performance adsorbents for CO2 adsorption and separation.

Identified factors and predicted unidentified-factors affecting ammonia emissions from a swine building.

Large variabilities in ammonia (NH3) released from animal manure and emitted from different livestock buildings were frequently reported, but the factors influencing the emissions were not sufficiently investigated. In this paper, continuously monitored data of NH3 emissions and other relevant environmental variables under controlled conditions in a 12-room experimental swine building for a 155-d complete wean-to-finish cycle were studied. Measurement data mining was conducted at both spatial and temporal dimensions using panel data analysis with heterogeneous time trends. The pig diet, total pig weight, and the pit air temperature were identified as the major influencing factors for the variabilities by using multivariate linear regression. Two unidentified factors that imposed substantial influences on the NH3 emission variabilities were predicted. They were most possibly related to variations in microenvironment and microbial activity inside the manure in the pit. The results suggest necessary future research to identify physical properties of the new NH3 emissions factors in microbiological and biochemical processes.

The effect of reduced CP, synthetic amino acid supplemented diets on growth performance and nutrient excretion in wean to Finish swine.

Mixed sex pigs (n = 720) were placed in 12 rooms (Purdue Swine Environmental Research Building) to measure the effect of reduced crude protein (CP), amino acid (AA)-supplemented diets on growth and the carcass. Pigs were blocked by body weight (BW) and gender and allotted to room and pen (10 mixed-sex pigs/pen). Pigs were fed a nine-phase, wean-finish program. Control pigs consumed corn-soybean meal-distiller's dried grains with solubles (DDGS) diets containing no to minimal (Met) synthetic AA. The 2X diet was formulated to meet the seventh most-limiting AA, and balanced using synthetic AAs to meet all AA needs. The 1X diet was formulated to meet a CP value halfway between the control and 2X diet, and also balanced using synthetic AAs to meet all AA needs. Diets were formulated to identical net energy concentrations and balanced to meet standard ileal digestible NRC 2012 AA requirements. Pit vacuum samples were collected at the end of each growth phase for analyses of nitrogen, C and dry matter (DM). Pigs fed the Control and 1X diet grew faster (P < 0.005), had greater gain:feed (P < 0.001), and were heavier at market (P < 0.001) than animals fed the 2X diet. No consistent effects of diet were observed on average daily feed intake. Carcass data were analyzed for sex, diet and sex*diet effects. Reductions in dietary CP resulted in a linear reduction in ammonium nitrogen excretion per kg of BW gain in Nursery (P < 0.001) and Grow-Finish (P < 0.001) phases. Reductions in dietary CP, with synthetic AA supplementation resulted in a linear reduction in total nitrogen excreted per kg BW gain in the Grow-Finish phase (P < 0.001) and overall (P < 0.001). Total mineral excretion per kg gain was reduced in pigs fed 1X and 2X diets compared with control-fed pigs (P < 0.005). Reductions in dietary CP of ~3 and 5%-units from wean-finish result in reductions of total N excretion of 11.7 and 24.4%, respectively. Reduced performance and carcass characteristics observed in pigs fed the 2X diets indicates an inaccurate estimate of NRC 2012 AA requirements or ratios to lysine in a low CP diet.

Collective Solvation and Transport at Tetrahydrofuran-Silica Interfaces for Separation of Aromatic Compounds: Insight from Molecular Dynamics Simulations.

We have performed umbrella sampling molecular dynamics simulations to study the separation mechanism of aromatic compounds at the tetrahydrofuran (THF)-methanol-silica interface by liquid chromatography. Solute molecules with different polarities (naphthol and naphthalene) are selected as representative aromatic compounds. For the polar solute (naphthol), the free energy profile shows a deep minimum near the THF-silica interface, suggesting strong interactions with the polar surface. When methanol is added to the interface, there is a sharp increase in naphthol's free energy minimum, and the corresponding diffusion dynamics also undergoes a dramatic change. These findings explain the fast separation mechanism in recent experiments of separating fused ring compounds in asphaltenes with liquid chromatography. Further solvation structure and orientation analysis suggest that apolar and polar solutes may find their own comfort zones several angstroms away from the interface, and their phenyl ring's orientations would undergo a parallel-to-perpendicular transition as the solute molecule moves away from the surface. Extending our simulation studies to systems with different solute concentrations reveals that there is a decrease in the adsorption free energy accompanied by enhanced surface diffusion as the solute concentration increases, which is related to the crowding in the interfacial layers. Our simulation analysis gives a detailed microscopic description of solute solvation and transport at the THF-silica chromatography interface and will be helpful for improving separation protocols in future applications.

The role of solute polarity on methanol-silica interfacial solvation: a molecular dynamics study.

The solvation structure and dynamics of small organic molecules at the methanol-silica interface are important for understanding the reaction dynamics in heterogeneous catalysis as well as the transport mechanisms in liquid chromatography. The role of solute polarity in interfacial solvation at the methanol-silica interface has been investigated via umbrella sampling molecular dynamics (MD) simulations and 1,3-propanediol and n-pentane were selected as representative species of polar and apolar solutes. Free energy calculations reveal that it took a similar free energy cost to transfer both solute molecules from the interface to the bulk, despite the huge difference in their polarities. The 1,3-propendiol molecule can penetrate the adsorbed methanol layer and form hydrogen bonds with the silica surface with its backbone perpendicular to the silica surface, resulting in a significant slowdown of translational and rotational dynamics. Further analysis of solvent density and solute orientations suggest that at the minimum of the adsorption free energy curve, the 1,3-propanediol molecule is in a desolvated state, while n-pentane is in a solvated state. The collective effect of solute concentration has also been studied by unbiased MD simulations, and the free energy barriers of transferring the solute molecule from the interface to bulk, as well as the parallel diffusion coefficients at the interface, show a non-monotonic dependence on solute concentration, which can be related to the crowded environment in the interfacial layers.

Molecular dynamics simulations of amino acid adsorption and transport at the acetonitrile-water-silica interface: the role of side chains.

The solvation and transport of amino acid residues at liquid-solid interfaces have great importance for understanding the mechanism of separation of biomolecules in liquid chromatography. This study uses umbrella sampling molecular dynamics simulations to study the adsorption and transport of three amino acid molecules with different side chains (phenylalanine (Phe), leucine (Leu) and glutamine (Gln)) at the silica-water-acetonitrile interface in liquid chromatography. Free energy analysis shows that the Gln molecule has stronger binding affinity than the other two molecules, indicating the side chain polarity may play a primary role in adsorption at the liquid-solid interface. The Phe molecule with a phenyl side chain exhibits stronger adsorption free energy than Leu with a non-polar side chain, which can be ascribed to the better solvated configuration of Phe. Further analysis of molecular orientations found that the amino acid molecules with apolar side chains (Phe and Leu) have 'standing up' configurations at their stable adsorption state, where the polar functional groups are close to the interface and the side chain is far from the interface, whereas the amino acid molecule with a polar side chain (Gln) chooses the 'lying' configuration, and undergoes a sharp orientation transition when the molecule moves away from the silica surface. Extending our simulation studies to systems with different solute concentrations reveals that there is a decrease in the adsorption free energy as well as surface diffusion as the solute concentration increases, which is related to the crowding in the interfacial layers. This simulation study gives a detailed microscopic description of amino acid molecule solvation and transport at the acetonitrile-water-silica interface in liquid chromatography and will be helpful for understanding the retention mechanism for amino acid separation.

The joint effect of surface polarity and concentration on the structure and dynamics of acetonitrile solution: a molecular dynamics simulation study.

The interfacial properties of the acetonitrile (ACN)-water-silica interface have great implications in both liquid chromatography and heterogeneous catalysis. We have performed molecular dynamics (MD) simulations of ACN and water binary solutions to give a comprehensive study of the collective effect of silica surface polarity and ACN concentration on interfacial structures and dynamics by tuning both surface charges and ACN concentration. MD simulation results indicate that many properties in the liquid-solid interface region undergo a monotonic change as the silica surface is tuned from polar to apolar due to the weakening of hydrogen bonding, while their dependence on ACN concentration is presumably governed by the preferential adsorption of water at the silica surface over ACN. However, at apolar surfaces, the interfacial structures of both water and ACN behave like the liquid-vapor interface, and this resemblance leads to an enrichment of ACN at the interface as well as accelerated dynamics, which is very different from that in the bulk solution. The organization of ACN molecules at both polar and apolar surfaces can be attributed to the amphiphilic nature of ACN, by which the micro-heterogeneity domain formed can persist both in the bulk and at the liquid-solid interface. Moreover, extending diffusion analysis to the second layer of the interface shows that the interfacial transport pathways at polar surfaces are likely very different from that of apolar surfaces. These simulation results give a full spectrum description of the ACN/water liquid-solid interface at the microscopic level and will be helpful for explaining related spectroscopic experiments and understanding the microscopic mechanisms of separation protocols in current chromatography applications.

The effect of surface polarity on the structure and collective dynamics of liquid ethanol.

We have performed molecular dynamics simulations to study the structure and dynamics of liquid ethanol at the α-Al2O3 surface. We scale the surface charges by a dimensionless parameter k, ranging from 0 to 1, which allows us to model the surface changing from apolar to polar. Compared with previous studies on hydrophilic surfaces, interfacial ethanol molecules form less densely packed layering structures and show less preferential orientational ordering as the alumina surface gradually becomes more apolar. Further analysis of hydrogen bonds and density correlation functions suggest that both hydrogen bonding between ethanol and the alumina surface and the interdigitation of alkyl groups control the interfacial structures collectively. Rotational dynamics and in-plane diffusion analysis show an acceleration of interfacial dynamics as the surface is switched to nonpolar, whereas interfacial rotational dynamics does not follow a monotonic trend during polarity tuning. Extending in-plane diffusion analysis to the second layer of the interface shows a strong enhancement of diffusion from the first layer at the polar interface in comparison to the apolar surfaces, suggesting different surface diffusion mechanisms at polar surfaces that may play an important role in the mobile phase transport in liquid chromatography.

Effects of antibiotic-free pig rearing on ammonia emissions from five pairs of swine rooms in a wean-to-finish experiment.

Antibiotic use and ammonia (NH3) emissions during animal production are two environmental issues of worldwide concern. However, the role of antibiotics on NH3 emissions is still unknown. This study evaluated the effects of rearing pigs without antibiotics on NH3 emissions from a swine experimental building starting with 657 piglets during a wean-to-finish production cycle of 154 days. Pigs were reared in two groups of 10 rooms that were divided into five 2-room pairs (P1-P5) and fed in nine dietary phases. Each pair consisted of one room without antibiotics (no antibiotics in the diet, water, or injectable) and another room as a positive control. Control animals were fed diets containing carbadox-10 (phases 1-4), chlortetracycline (CTC, phase 5), lincomix (phases 6-7), and tylan 40 (phases 8-9). Temperatures in the pig living space and the under-floor manure pit headspace were continuously measured. Ventilation rates at all wall fans and pit fans were obtained by continuous monitoring. Ammonia concentrations in the wall and pit fan exhaust air, and in room inlet air were measured with two multi-gas monitors. Only days that contained at least 18 h of data each day were validated and used. The study generated 1337 room-days of valid data of NH3 emission rates, with a data completeness of 88.6%. Daily mean NH3 emission patterns demonstrated large variations between the paired rooms and among different pairs. Within the individual 2-room pairs, no NH3 emission differences were found in P1 (rooms 1 and 2, p = 0.34) and P2 (rooms 3 and 4, p = 0.44). Significant differences were found in P3-P5 (p < 0.01). The antibiotic-free rooms emitted more NH3 from P3 and P4, but less NH3 from P5. However, the combined cycle mean NH3 emissions from the group of five antibiotic-free rooms and the group of five control rooms were 41.6 ±â€¯10.5 and 39.4 ±â€¯10.6 g d-1 AU-1 (mean ±â€¯standard deviation. AU = 500 kg live body weight), respectively. Therefore, there was no statistical difference in combined cycle mean NH3 emissions from rearing pigs with or without antibiotics (p = 0.78). This study also revealed that experiments with multiple replicates and long NH3 monitoring durations were necessary to avoid potential misinterpretation of experimental results.

Hydrogen sulfide emissions from a swine building affected by dietary crude protein.

Hydrogen sulfide (H2S) is a toxic air pollutant at animal facilities; but the understanding of its generation and emission processes has been limited. This paper studied H2S emissions during a complete cycle of wean-finish pigs from a research building, where 12 pig rooms were divided into three groups that were fed with standard feed (control), and 2.1-3.8% (T1) and 4.4-7.8% (T2) reduced dietary crude protein (CP) feed. The group cycle mean H2S emission rates were 4.0 ± 2.9, 4.3 ± 3.2, and 5.4 ± 4.0 g d-1 AU-1 (Animal Unit = 500 kg live mass), respectively, for the control, T1, and T2 groups. Emissions of H2S were promoted by 10.0 and 36.7%, respectively, for the T1 and T2 groups (p < 0.001), although large variabilities existed in the emissions from different rooms within the same groups. The enhanced H2S emissions from the T1 and T2 groups were related to the reduced manure pH and were possibly affected through a number of pathways, which could involve volatile fatty acids and nitrogen concentrations, and microbial activities in manure.

Mitigation of ammonia emissions from pig production using reduced dietary crude protein with amino acid supplementation.

To mitigate ammonia (NH3) emissions from pig production and understand dynamic emission profiles, reduced dietary crude protein (CP) with amino acid supplementation was studied with 720 pigs in a 12-room research building for 155days that covered from weaned to finishing stages. The pigs were divided into three 4-room groups and fed with 2.1-3.8% reduced CP (T1), 4.4-7.8% reduced CP (T2), and standard (control) diets, respectively. Compared with the control group, T1 and T2 decreased manure volumes and manure NH4+-N concentrations. Group-mean NH3 emission from the control group was 68.9gd-1AU-1 (AU=500kg live mass). Emissions from T1 (46.7gd-1AU-1) and T2 (29.8gd-1AU-1) were reduced by 33.0% and 57.2% (p<0.05), respectively. Dynamic peak NH3 emissions appeared during the third nursery phase for T1 and T2, but delayed to the first grower phase for the control group.

Long-ranged contributions to solvation free energies from theory and short-ranged models.

Long-standing problems associated with long-ranged electrostatic interactions have plagued theory and simulation alike. Traditional lattice sum (Ewald-like) treatments of Coulomb interactions add significant overhead to computer simulations and can produce artifacts from spurious interactions between simulation cell images. These subtle issues become particularly apparent when estimating thermodynamic quantities, such as free energies of solvation in charged and polar systems, to which long-ranged Coulomb interactions typically make a large contribution. In this paper, we develop a framework for determining very accurate solvation free energies of systems with long-ranged interactions from models that interact with purely short-ranged potentials. Our approach is generally applicable and can be combined with existing computational and theoretical techniques for estimating solvation thermodynamics. We demonstrate the utility of our approach by examining the hydration thermodynamics of hydrophobic and ionic solutes and the solvation of a large, highly charged colloid that exhibits overcharging, a complex nonlinear electrostatic phenomenon whereby counterions from the solvent effectively overscreen and locally invert the integrated charge of the solvated object.

Orientational time correlation functions for vibrational sum-frequency generation. 2. Propionitrile.

Molecular dynamics (MD) simulations of propionitrile have been performed to assess the influence of reorientation on vibrational sum-frequency-generation (VSFG) spectra at the liquid/vapor (LV) and liquid/silica (LS) interfaces. Orientational time-correlation functions (TCFs) are derived for the VSFG spectroscopy of the symmetric and asymmetric stretches of functional groups such as methylene groups and rotationally hindered methyl groups. The MD simulations are used to compute VSFG orientational TCFs for the methyl, methylene, and cyanide groups of propionitrile at the LV and LS interfaces. Although propionitrile exhibits relatively fast reorientation in the bulk liquid, we find that for symmetric stretching modes at these interfaces, reorientation only plays a significant role in VSFG spectra under SPS polarization conditions. For asymmetric stretches, reorientation affects the VSFG spectra significantly under all polarization conditions. Azimuthal dynamics tend to dominate the orientational TCFs.

[Study on quantification assessment and odor fingerprint of volatile aromatic hydrocarbons from sewage treatment plant].

The malodorous volatile organic compounds (MVOCs) from a typical municipal sewage treatment plant in Guangzhou were detected and analyzed using thermal-desorption/GC-MS and electronic nose, respectively. The results showed that: (1) Aromatic hydrocarbons were the main malodorous volatile organic compounds of the sewage treatment plant, with concentrations ranging from 96.61 microg x m(-3) to 818.03 microg x m(-3), accounting for more than 50% of the total MVOCs, much higher than other MVOCs species. (2) Volatile aromatic hydrocarbons (VAH) in municipal sewage treatment plant were mainly from domestic wastewater, and the sludge treatment process played an important part in release of these pollutants. The total concentration of aromatic hydrocarbons emitted from each processing unit in a descending order was: the sludge dehydration room > sludge thickener > aeration tank > grille > biochemical pool> grit chamber. (3) rincipal component analysis (PCA) was able to distinguish the characteristic of odor emission from each processing unit, with the recognition index reaching 71% , and the PCA recognition index of simulated gases which simulated the VAH levels of different processes reached 94% , indicating that there was big difference among the srmll of the VAH emitted from different processes. (4) The comparison of the original odor fingerprint and simulated odor fingerprint measured by the sensor T70/2 showed that the original odor fingerprint was greater than the simulated odor fingerprint, and the correlation analysis indicated that the VAH had a great contribution to the odor fingerprint of each unit, and the contribution of VAH odor of the aeration tank tq the original odor fingerprint reached 0. 98.

Orientational time correlation functions for vibrational sum-frequency generation. 1. Acetonitrile.

Orientational time correlation functions (TCFs) are derived for vibrational sum-frequency generation (VSFG) spectroscopy of the symmetric and asymmetric stretches of high-symmetry oscillators such as freely rotating methyl groups, acetylenic C-H groups, and cyanide groups. Molecular dynamics simulations are used to calculate these TCFs and the corresponding elements of the second-order response for acetonitrile at the liquid/vapor and liquid/silica interfaces. We find that the influence of reorientation depends significantly on both the functional group in question and the polarization conditions used. Additionally, under some circumstances, reorientation can cause the VSFG response function to grow with time, partially counteracting the effects of other dephasing mechanisms.

[Source emission characteristics and impact factors of volatile halogenated organic compounds from wastewater treatment plant].

A low enrichment method of using Tenax as absorbent and liquid nitrogen as refrigerant has been established to sample the volatile halogenated organic compounds in Guangzhou Liede municipal wastewater treatment plant as well as its ambient air. The composition and concentration of target halogenated hydrocarbons were analyzed by combined thermal desorption/GC-MS to explore its sources profile and impact factors. The result showed that 19 halogenated organic compounds were detected, including 11 halogenated alkanets, 3 halogenated alkenes, 3 halogenated aromatic hydrocarbons and 2 haloesters, with their total concentrations ranged from 34.91 microg x m(-3) to 127.74 microg x m(-3) and mean concentrations ranged from n.d. to 33.39 microg x m(-3). Main pollutants of the studied plant were CH2Cl2, CHCl3, CFC-12, C2H4Cl2, CFC-11, C2HCl3 and C2Cl4, they came from the wastewater by volatilization. Among the six processing units, the dehydration room showed the highest level of halogenated organic compounds, followed by pumping station, while the sludge thickener was the lowest. The emissions from pumping station, aeration tank and biochemical pool were significantly affected by temperature and humidity of environment.

[Quantification assessment of the relationship between chemical and olfactory concentrations for malodorous volatile organic compounds].

Using self-made cold-traps and gas bags, the odor samples were collected from 6 sewage treatment workshops of a typical municipal sewage treatment plant in Guangzhou City. The chemical composition and olfactory concentrations of these samples were respectively analyzed by thermal-desorption/GC-MS and triangle odor bag method. Finally, a mathematical equation was built for assessing the relationship between principal organic odorants and the olfactory concentrations. The result showing that: (1) More than 70 volatile organic compounds were detected in municipal sewage treatment plant, among which were 30 malodorous volatile organic compounds (MVOCs), ranging from 0.37 to 1 872.24 microg x m(-3) and appearing in sludge dewatering, thickening and aeration tank with the highest concentrations. (2) Principle component analysis was used to group the target MVOCs into 5 categories: benzenes, halohydrocarbons, aldehydes, hydrocarbons and S, N-containing organic compounds. (3) Multiple lineal regression analysis was used to build a quantified relationship between chemical and olfactory concentrations of MVOCs. The result indicated that 25% of the odor problem of sewage treatment unit was due to MVOCs. The predicted values were fitting well with measured values. The sensitivity of mathematical equation for measuring odor concentration was higher than that of human olfactory system.