Sorption of polycyclic aromatic compounds to humic and fulvic acid HPLC column materials

Two different humic acids (HA) and a fulvic acid (FA) were chemically immobilized to a high performance liquid chromatography (HPLC) silica column material. The immobilization was performed by binding amino groups in HA/FA to the free aldehyde group in glutardialdehyde attached to the silica gel. The HPLC column materials were compared with a blank column material made by applying the same procedure but without immobilizing HA or FA. Also, a column was made by binding carbonyl groups in HA to amino groups attached to the silica gel. The humic substances were selected to secure appropriate variation of their structural features. The retention factors of 45 polycyclic aromatic compounds (PAC) to the four columns were determined by HPLC. The advantage of the technique is a large number of compounds can easily be studied. The binding procedure does not appear to cause a drastic selection between the HA molecules. The k' values obtained for the two Aldrich HA columns agree in general reasonably. The retention or sorption of the compounds increased with the size of the PAC and the number of lipophilic substituents, but decreased when polar substituents were present. The PAC retention was much stronger to the two HA columns than to the FA and blank column, both for hydrophobic polycyclic aromatic hydrocarbons (PAH) and the polar PAC. Other factors impacting the PAC binding may be specific interactions with HA and the ionic strength of the aqueous phase. The technique has been applied to do direct determinations of Koc.     

Sorption of apolar aromatic compounds to soil humic acid particles affected by aluminum(III) ion Cross-Linking

Sorption of hydrophobic compounds in soils often shows nonlinearity, competition, and hysteresis. Since such behaviors have been associated with organic polymers in glassy state, it has been postulated that some forms of soil humic substances are glassy. The glassy state is favored by properties that decrease the flexibility of macromolecules, such as cross-linking, presence of unsaturated bonds, and high molecular weight. Polyvalent metal ions, which are abundant in soils, may cross-link humic substances by coordinating to multiple functional groups on different strands. Accordingly, we prepared an Al(3+)-cross-linked humic acid (Al-HA) from the H(+) form (H-HA) of a soil humic acid by a flocculation technique that leaves Al ions bound to organic groups. Sorption of naphthalene and 1,2,4-trichlorobenzene (TCB) on H-HA was nonlinear, competitive, and slightly hysteretic, in agreement with previous studies showing glass transition temperatures of humic acids that lie above room temperature. Nonlinearity, competition, and hysteresis were all enhanced in Al-HA, validating the hypothesis that metal ion cross-linking enhances nonideal sorption. Application of a glassy polymer sorption model reveals that cross-linking increases the affinity of solutes for the hole domain relative to the dissolution domain. The results (i) indicate that isolated, purified soil humic acid behaves like a glassy solid, (ii) indicate that metal-ion cross-linking creates a more rigid-chain structure and supports a link between nonideal sorption and the glassy character of soil organic matter, and (iii) underscore the importance of metal ions on humic structure in relation to sorption of hydrophobic organic compounds.     

Polycyclic aromatic hydrocarbon storage in a typical Cerrado of the Brazilian savanna

There may be important biological sources of polycyclic aromatic hydrocarbons (PAHs) to the global environment, particularly of naphthalene, phenanthrene, and perylene, that originate in the tropics. We (i) studied the distribution of PAHs among different compartments of a typical Cerrado to locate their sources and (ii) quantified the PAH storage of this ecosystem. The sum of 20 PAH (sigma20PAHs) concentrations ranged from 25 to 666 microg kg(-1) in plant tissue, 7.4 to 32 microg kg(-1) in litterfall, 206 to 287 microg kg(-1) in organic soil, and 10 to 79 microg kg(-1) in mineral soil. Among the living biomass compartments, the bark had the highest mean PAH concentrations and coarse roots the lowest, indicating that PAHs in the plants originated mainly from aboveground sources. Naphthalene and phenanthrene were the most abundant individual PAHs, together contributing 33 to 96% to the sigma20PAHs concentrations. The total storage of the X20PAHs in Cerrado was 7.5 mg m(-2) to a 0.15-m soil depth and 49 mg m(-2) to a 2-m soil depth. If extrapolated to the entire Brazilian Cerrado region, roughly estimated storages of naphthalene and phenanthrene correspond to 7300 and 400 yr of the published annual emissions in the United Kingdom, respectively. The storage of benzo[a]pyrene, a typical marker for fossil fuel combustion, in the Cerrado only corresponds to 0.19 yr of UK emissions. These results indicate that the Brazilian savanna comprises a huge reservoir of naphthalene and phenanthrene originating most likely from the aboveground parts of the vegetation or associated organisms. Thus, the Cerrado might be a globally important source of these PAHs.     

Multinuclear magnetic resonance analysis of two humic acid fractions from lowland rice soils

To determine the effects of intensive cropping of tropical lowland rice (Oryza sativa L.) and the associated long-term soil submergence on chemical properties of soil organic matter, we used solid-state 13C and 15N and solution 31P nuclear magnetic resonance (NMR) spectroscopy to analyze the labile mobile humic acid (MHA) and the more recalcitrant calcium humate (CaHA) fractions extracted from a series of soils supporting several long-term field experiments in the Philippines. The soils varied mainly in degree of submergence and cropping intensity, ranging from a rainfed rice field without soil submergence to irrigated double- and triple-cropped fields in which soil remains submerged almost all year long. As reported previously, all analyses associated increasing intensity of rice cropping with larger proportions of less humified material in the MHA and CaHA, such as diester phosphorus (P), amide nitrogen (N), and phenolic carbon (C). We established significant correlations between proportions of various spectral areas as well as between some spectral areas and other humic acid (HA) properties such as visible light absorption and free radical concentration (positive indices of humification) and hydrogen (H) concentration (negative index of humification). For example, spectral proportions of heterocyclic N were positively, and proportions of amide N and phenolic C negatively, correlated with visible light absorption and free radical concentration, and each of these spectral proportions had an opposite sign when correlated with H concentration. The correlations of N-alkyl C proportions were the strongest with these properties and with other functional group proportions.     

Structural and sorption characteristics of adsorbed humic acid on clay minerals

Clay-humic complexes are commonly distributed in natural environments. They play very important roles in regulating the transport and retention of hydrophobic organic contaminants in soils and sediments. This study examined the structural changes of humic acid (HA) after adsorption by clay minerals and determined phenanthrene sorption by clay-humic complexes. Solid- and liquid-state 13C nuclear magnetic resonance (NMR), for the first time, provided direct evidence for HA fractionation during adsorption on mineral surfaces, that is, aliphatic fractions were preferentially adsorbed by clay minerals while aromatic fractions were left in the solution. The ratio of UV absorbance of HA at 465 and 665 nm (E4 to E6 ratio), which is related to aromaticity, corroborated with the NMR results. For both montmorillonite and kaolinite, adsorbed HA fractions had higher sorption linearity (N) and affinity (K(oc)) than the source HA. The K(oc) of adsorbed HA for the clay-humic complexes could be up to several times higher than that of the source HA. This large increase may be contributed by the low polarity of the bound HA. Moreover, for each mineral, the N values of adsorbed HA increased with increasing HA loading. It is believed that HA may develop a more condensed structure on mineral surface at lower HA loading level due to the stronger interactions between HA and mineral surface as a result of close contacts.     

Sorption of aromatic compounds to clay mineral and model humic substance-clay complex: effects of solute structure and exchangeable cation

Clay minerals and humic substance (HS)-clay complexes are widely distributed in soil environments. Improved predictions on the uptake of organic pollutants by soil require a better understanding of fundamental mechanisms that control the relative contribution from organic and inorganic constituents. Five selected aromatic compounds varying in electronic structure, including nonpolar phenanthrene (PHEN), 1,2,4,5-tetrachlorobenzene (TeCB), polar 1,3-dinitrobenzene (DNB), 2,6-dichlorobenzonitrile (dichlobenil [DNL]), and 1-naphthalenyl methylcarbamate (carbaryl [CBL]), were sorbed separately from aqueous solution to Na(+)-, K(+)-, Cs(+)-, and Ca(2+)-saturated montmorillonites with and without the presence of dissolved HS at pH about 6. Upon normalizing for hydrophobic effects by solute aqueous solubility, the overall trend of sorptive affinity to HS-free K(+)-clay is DNB > DNL, CBL > PHEN, TeCB, indicating preferential adsorption of the polar solutes. With the presence of HS, sorption of PHEN, TeCB, and CBL increases by several times compared with the pure clay, attributed to HS-facilitated hydrophobic partition (PHEN and TeCB) or H-bonding (CBL). The enhanced sorption of PHEN by HS is cation dependent, where Cs(+) shows the strongest facilitative effect. Coadsorption of HS does not affect sorption of DNB and DNL to clays except that of DNB to Ca(2+)-clay because cation-dipole interactions between the polar group (NO(2) or CN) of solute and weakly hydrated exchangeable cations dominate the overall sorption.     

Planning implications from the interactions between renewable energy programs and carbon regulation

Complex relationships exist between programs to reduce carbon dioxide (CO₂) from the electricity sector and programs to promote renewable electricity generation. Simulation modeling of three scenarios in the UK electricity sector are used to identify potential interactions between these programs. A strict CO₂ cap can result in a renewable electricity requirement being easily met. Conversely, the renewables quota could be required under low natural gas prices to keep electricity suppliers from switching from coal to gas. Similarly, CO₂ trading can reduce renewables deployment levels because purchased CO₂ allowances replace renewables. Therefore, both programs are required to ensure CO₂ and renewables goals. The planning implications for administrative procedures and renewables subsidies are also discussed.     

Formation of pi-pi complexes between phenanthrene and model pi-acceptor humic subunits

Pi-pi interactions may play a role in association of aromatic compounds with natural organic substances. Complexation in aqueous solvents was studied between the pi donor, phenanthrene (PHEN), and model pi-acceptor species (quinones and N-heteroaromatic cations) that represent certain functional units of humic substances. Charge-transfer bands in the UV and ring-current shifts in the proton nuclear magnetic resonance (NMR) spectrum confirmed the face-to-face, pi-pi donor-acceptor nature of the bond. Complexation constants were obtained by the solubility enhancement method; solubility enhancements up to 2500 were found. Ruled out as predominant causes of solubility enhancement were monomer desolvation (i.e., "hydrophobic" effects), partitioning into micelles, pi-cation interactions, and pi-hydrogen bonding. Acceptor self-stacking and formation of higher-stoichiometry acceptor-donor complexes had to be considered in evaluating donor-acceptor equilibria in some cases. The affinity of acceptor for PHEN followed the order of increasing pi-acceptor strength and varied strongly with the degree of ring overlap with PHEN. Complexation between PHEN and the free solution faces of an acceptor was less favorable than intercalation of PHEN between two acceptor units in a stack. A positive hydrophobic effect on complexation was evident in water mixtures with acetone or methanol and found to correlate with the number of faces of PHEN requiring desolvation to form the complex. When hydrophobic effects are subtracted out, the pi-pi complex actually becomes favored as the solvent water content and polarity decline. The results suggest that phenanthrene, and by implication other donor aromatic compounds, are capable of forming pi-pi interactions with appropriate humic fragments.     

Removal of a red dye using noncommercial peroxidase extracted from rice bran

The present study investigates the application of a noncommercial peroxidase enzyme, which was extracted from rice bran, to decolorize wastewater that was simulating effluent from a textile manufacturer using a red dye in its coloration process.     

Comparative analysis of partial structures of a peat humic and fulvic acid using one- and two-dimensional nuclear magnetic resonance spectroscopy

Nuclear magnetic resonance (NMR) resonance integrals obtained from one-dimensional NMR spectra provide semiquantitative contents of humic constituents with limited resolution in structural detail. When supplemented by connectivity information available from homo- and heteronuclear two-dimensional NMR spectra a more reliable assignment of humic substructures becomes available. This is demonstrated with a comparative one- and two-dimensional NMR analysis of a fulvic and a humic acid obtained from Eriophorum peat. An example of a detailed analysis of the proton chemical shift region normally attributed to carbohydrates shows substantial contributions from amino acids, amino and desoxy sugars, and highly oxidized aliphatic chains of intermediate length. The very good resolution of structural detail by a combined analysis of all NMR spectra shows that the effect of the fractionation procedure on the composition and chemical structure of humic materials is very significant. The comparison of the partial structures comprising humic acid (HA) and fulvic acid (FA) of the peat humic materials studied indicates that FA is diagenetically downstream of HA, favoring the biopolymer degradation (BD) model of humification.     

Sorption and detoxification of toxic compounds by a bifunctional organoclay

Organoclays are excellent sorbents for nonionic contaminants and therefore may have many environmental applications. A major limitation on the use of organoclays is that the contaminant merely changes its location from one environmental compartment to another while still remaining intact. In this study, a new type of organoclay, termed a bifunctional organoclay, has been prepared. It is able not only to sorb organophosphate pesticides, but also to catalyze their hydrolysis, and thereby detoxify them. The bifunctional organoclay prepared in this study is based on sodium montmorillonite, in which the inorganic counter ions are replaced by N-decyl-N,N-dimethyl-N-(2-aminoethyl) ammonium (DDMAEA). The detoxifying capacity of this organoclay for two organophosphate pesticides, methyl parathion [O,O-dimethyl O-(p-nitrophenyl) thionophosphate] and tetrachlorvinphos [2-chloro-1-(2,4,5-trichlorophenyl)ethenyl dimethyl phosphate], was demonstrated. It was shown that although the sorption of these pesticides on the bifunctional organoclay is very similar to that on N-decyl-N,N,N-trimethyl ammonium (DTMA) organoclay (the corresponding nonbifunctional organoclay), the hydrolysis of these pesticides is substantially enhanced only by the bifunctional organoclay. The half-life for the hydrolysis of the investigated pesticides in the presence of the bifunctional organoclay is about 12 times less than for their spontaneous hydrolysis, and the enhancement is even more pronounced relative to the hydrolysis of these pesticides in the presence of the DTMA organoclay (which actually inhibits their hydrolysis). Based on kinetic measurements, the pK(a) of the ethylamino group of the bifunctional organoclay was estimated to be around 9.0. It is postulated that the catalytic effect of the bifunctional organoclay can be attributed to a nucleophilic attack of the unprotonated ethylamino group of the organoclay on the organophosphate ester.     

Proton binding by humic and fulvic acids from pig slurry and amended soils

The knowledge of acid-base characteristics of humic acid (HA) and fulvic acid (FA) fractions of organic amendments and amended soils is of considerable importance for assessing their agronomic efficacy and environmental impact. In this work, the acid-base properties of HAs and FAs isolated from pig slurry, soils amended with either 90 or 150 m(3) ha(-1) yr(-1) of pig slurry for 3 yr, and the corresponding nonamended control soil were investigated by using a current potentiometric titration method. The nonideal competitive adsorption (NICA) model that describes proton binding by two classes of binding sites (carboxylic- and phenolic-type groups) was successfully fit to titration data. With respect to the control soil HA and FA, pig-slurry HA and FA were generally characterized by smaller carboxylic-type group contents, slightly smaller phenolic-type group contents, larger affinities for proton binding by the carboxylic-type groups, and much smaller, in the case of the HA fraction, or similar, in the case of the FA fraction, affinities for proton binding by the phenolic-type groups. Amendment with pig slurry determined a number of modifications in soil HAs and FAs, including decrease of acidic functional group contents, and slight increase of the proton affinity of the carboxylic-type groups. Further, a slight decrease of the affinities for proton binding by the phenolic-type groups of HAs was observed. These effects can have a large impact on the biological availability, mobilization, and transport of macro- and micronutrients, toxic metal ions, and xenobiotic organic cations in pig slurry-amended soils.     

Nonthermal mechanism of interactions between electromagnetic fields and biological systems: a calmodulin example

The possible mechanisms of interactions of electromagnetic fields (EMF) with biological systems are often discussed in bioelectromagnetics in light of thermal versus nonthermal mechanisms. This paper attempts to show the principle difference between the biophysical and engineering approaches to biological mechanisms of EMF initiated bioeffects. While biophysical approach is based on experimentally obtained data on biological responses to the applied EMF, the engineering approach strongly relies on specific absorption rate (SAR) value. With experimental data, comparing effects of low- and high-frequency electromagnetic fields, discussing modulation of radiofrequency (RF) signals, the author demonstrates the superiority of the nonthermal approach. Biological windows, resonance mechanism, and various reported biological effects of geomagnetic fields are also in favor of the nonthermal mechanisms. Finally, one potential nonthermal mechanism involving the role of calmodulin in cellular functions is shown in this paper.     

Sorption of inorganic and total phosphorus from dairy and swine slurries to soil

Understanding P sorption from animal manures is essential to formulate best management practices with regard to land application of manure from the standpoint of crop production and environmental quality. Little research has focused on the construction of P sorption isotherms where the P source is manure. The objectives of this study were to: (i) develop a procedure to characterize how inorganic P (P(i)) and total P (P(t)) from dairy slurry and swine slurry sorbs to soil; and (ii) compare the sorption characteristics of P(i) and P(t) where the P source was dairy slurry, swine slurry, or potassium phosphate (KH2PO4). Sorption solutions were prepared in 0.1 M KCl at pH 6 and equilibrated with soils at a 1:25 (w/v) soil/solution ratio for 24 h. Inorganic P, P(t), Al, and Fe in the equilibrated solutions were measured. For all soils, P(i) and P(t) sorption capacity of dairy slurry was greater than KH2PO4. Total P sorption capacity of swine slurry was greater than KH2PO4, while P(i) sorption capacity was less than KH2PO4. Overall, P(i) and P(t) sorption strengths of the manure slurries were less than or equal to KH2PO4. Increased P(i) sorption from dairy slurry was correlated with Fe and Al desorption. Reduction of P(i) sorption capacity from swine slurry was related to preferential sorption of organic P. Additional studies need to be conducted to determine how differences in P sorption between manures and fertilizer impact in-field P availability to a crop and potential for losses in runoff water.     

Atrazine toxicity to Handroanthus heptaphyllus,a nontarget species from a Brazilian biome threatened by agriculture

The economic basis of the Brazilian midwest is agriculture, concentrating most of the grain production in the country. With the purpose of increasing yield, farmers have intensified land use and the use of atrazine among other pesticides, which can supposedly compromise human health and photosynthetic metabolism of plant species from Cerrado, such as Handroanthus heptaphyllus. The aim of this study was to determine experimentally the sensitivity level of H. heptaphyllus to atrazine, by measuring gas exchange, chlorophyll a fluorescence, chloroplastidic pigments, and membrane permeability. The experiment was conducted in a factorial scheme. Nine‐month‐old H. heptaphyllus plants were treated with six realistic doses of atrazine: 0, 25, 50, 100, 200, and 400 g a.i. ha^–1 (corresponding to 10, 20, 40, 80, and 100% of the commercial dose recommended for corn crops, respectively), with five replications. Evaluations were performed at 12, 36, 84, 180, and 276 h after treatment application. Photosynthesis, the effective quantum yield of photosystem II, and electron transport rate were gradually reduced by the action of atrazine. On the other hand, the nonphotochemical quenching increased gradually, which indicates that this mechanism was not sufficient to avoid oxidative stress and cellular damage in H. heptaphyllus treated plants. Based on these results, we concluded that the action of the herbicide in the photosynthetic reduction occurs by the electron transport rate limitation. Therefore, H. heptaphyllus trees are at risk in Cerrado areas next to agricultural lands.     

Sorption kinetics and equilibria of organic pesticides in carbonatic soils from South Florida

A batch reactor was used to determine sorption kinetic parameters (k2, F, and K*) and the equilibrium sorption coefficient (K). The two-site nonequilibrium (TSNE) batch sorption kinetics model was used to calculate the kinetic parameters. Two probe organic pesticides, atrazine [2-chloro-4-ethylamino-6-isopropylamino-s-triazine] and diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] were studied using three carbonatic soils from South Florida (Chekika, Perrine, and Krome), one noncarbonatic soil from Iowa (Webster), and one organic soil (Lauderhill) from South Florida. Carbonatic soils contained more than 600 g kg(-1) CaCO3. Sorption is initially very fast up to 3 h and then slowly reaches equilibrium. All soil-chemical combinations reached sorption equilibrium after about 24 h and all sorption isotherms were linear. The sorption kinetics data were well described by the TSNE model for all soil-chemical combinations except for the marl soil data (Perrine-Atrazine), which were better described by the one-site nonequilibrium (OSNE) model. Diuron, with higher K, undergoes slower sorption kinetics than atrazine. The Lauderhill soil containing organic carbon (OC) of 450 g kg(-1) exhibited slowest sorption kinetics for both pesticides. An inverse relationship between k3 and K was observed for atrazine and diuron separately in Chekika, Webster, and Lauderhill soils but not in Perrine and Krome soils. The sorption kinetic parameters were used to distinguish the sorption behavior between atrazine and diuron and to identify differences between soils. Normalizing the sorption coefficient (K) to OC showed that atrazine and diuron had K oc values in carbonatic soils that were a third of reported literature values for noncarbonatic soils. Using existing literature K oc values in solute transport models will most likely underestimate the mobility of atrazine, diuron, and other neutral organic chemicals in carbonatic soils.     

Framing community forestry challenges with a broader lens: case studies from the Brazilian Amazon

Community forestry initiatives have been shown to reduce rural poverty while promoting the conservation and sustainable use of forests. However, a number of challenges face communities wanting to initiate or maintain formal, community-based forest management. Through a grounded theory approach, this paper uses three case studies of community forest management models in the eastern Amazon to create a framework showing challenges faced by communities at different phases of formal management. The framework shows that, in the development phase, four root problems (land ownership, knowledge acquisition, community organization, and adequate capital) need to be addressed to obtain legal management permission. With this permission in hand, further challenges to operationalization are presented (deterring illegal loggers, maintaining infrastructure, obtaining necessary managerial skills and accessing markets). The interrelatedness of these challenges emphasizes that all challenges need to be addressed in a holistic manner for communities to maintain a profitable and self-sufficient operation. This contradicts current development approaches that only address part of this framework. The framework proposed here can be used as a starting point for community forestry initiatives in other regions.     

Sorption of atmospheric ammonia by soil and perennial grass downwind from two large cattle feedlots

Livestock manure in feedlots releases ammonia (NH3), which can be sorbed by nearby soil and plants. Ammonia sorption by soil and its effects on soil and perennial grass N contents downwind from two large cattle feedlots in Alberta, Canada were investigated from June to October 2002. Atmospheric NH3 sorption was measured weekly by exposing air-dried soil at sampling points downwind along 1700-m transects. The amount of NH3 sorbed by soil was 2.60 to 3.16 kg N ha(-1) wk(-1) near the source, declining to about 0.25 kg N ha(-1) wk(-1) 1700 m downwind, reflecting diminishing atmospheric NH3 concentrations. Ammonia sorption at a control site away from NH3 sources was much lower: 0.085 kg N ha(-1) wk(-1). Based on these rates, about 19% of emitted NH3 is sorbed by soil within 1700 m downwind of feedlots. Field soil and grass samples from the transect lines were analyzed for total N (TN) and KCl-extractable N content (soil only). Nitrate N content in field soil followed a trend similar to that of atmospheric NH3 sorption. Soil TN contents, because of high background levels, showed no clear pattern. The TN content of grass, downwind of the newer feedlot, followed a pattern similar to that of NH3 sorption; downwind of the older feedlot, grass TN was correlated to soil TN. Our results suggest that atmospheric NH3 from livestock operations can contribute N to local soil and vegetation, and may need to be considered when determining fertilizer rates and assessing environmental impact.     

石英砂、生物质炭、胡敏酸的相互作用及其对BDE-47吸附行为的影响

研究了生物质炭、胡敏酸、石英砂之间的相互作用对BDE-47吸附行为的影响,结果表明：（1）石英砂和生物质炭的相互作用对BDE-47的吸附行为的影响不显著;（2）在低浓度条件下（Ce=0.05Sw时）,石英砂可以促进胡敏酸对BDE-47的吸附作用,使胡敏酸的吸附能力提高16％;在高浓度条件下（Ce=0.25Sw时）,石英砂可以抑制胡敏酸对BDE-47的吸附作用,使胡敏酸的吸附能力降低64％;（3）胡敏酸和生物质炭之间的相互作用可以抑制生物质炭-胡敏酸-石英砂体系对BDE-47的吸附作用,使整体吸附能力降低35％～38％.