Acid Buffering Capacity Research Articles

Sorption of sulfate and retention of cations in forest soils of Lien-Hua-Chi watershed in central Taiwan

In Taiwan, the average sulfate and nitrate deposited by acid rain as precipitation amount to 50 kg SO 4 2− and 15–50 kg NO 3 − ha −1 year −1, respectively. The reactions of sulfate and nitrate with forest soils were not fully understood. Thus, we selected two forest pedons, namely the Dystrochrept and Hapludult of the Lien-Hua-Chi watershed in central Taiwan, to study their sorption and desorption of sulfate. Soil samples were leached with simulated acid rain solutions of various acidity and sulfate concentrations to assess their retention of cations and sulfate. The amounts of sorbed-SO 4 2− of two pedons extracted with NaH 2PO 4 (0.016 M) solutions in the range 0.14–1.09 mmol kg −1 soil were higher than that of native water-soluble sulfate (i.e., extracted with H 2O), in the range 0.15–0.41 mmol kg −1 soil. The amounts of native sorbed-SO 4 2− of two pedons correlated significantly with the exchangeable Al ( r = 0.91). The sorption of sulfate did not fit well the Langmuir equation. The native sulfate contents of all tested pedons were near the maximum sulfate sorption capacity. The sulfate sorption capacity and the amount of released Al correlated well with increasing acidity of simulated acid rain added. Introducing solutions of various acidity and sulfate concentrations into the leaching solution flowing through the soil column resulted in sharp increases in amount of sulfate and aluminum released in percolates after several pore volumes were replaced. High clay and sesquioxide contents at soil depths of 30–50 cm (Bw horizon) and 50–80 cm (BC) of pedon 1 retained part of the sulfate added serving as the sulfate sink. Released K, Mg and Ca showed two periods of higher leaching pattern, having a trend similar to that the electrical conductivity (EC) pattern. After leaching of simulated acid rain through the soil column, the soil exchangeable cations were decreased. The tested soils possess an acid-buffering capacity in pedon 1. Pedon 1 is composed of high clay and sesquioxide contents and possesses greater buffer capacity than that of pedon 2.

Application of Polished‐Graded Wheat Grains for Sourdough Bread

ABSTRACTFlours obtained by a specific polishing process were used to prepare sourdough and bread. Three fractions designated C‐1 (100–90%), C‐5 (60–50%), and C‐8 (30–0%) were studied. The pH, total titratable acidity levels, and buffering capacity of sourdoughs made from polished flours were significantly different from those of the control sourdough with No. 1 Canada Western Red Spring (CW), and they provided sourdough breads with better qualities than that of CW. The growth of lactic acid bacteria and yeast in polished flour sourdoughs were significantly accelerated during fermentation over that in CW sourdough. Higher maturation of polished flour sourdoughs softened the hardness of mixed dough. The intricate network of honeycomb structure gluten and uneven surface of starch granules were distinctly observed in SEM images. Substitutions of C‐5 or C‐8 sourdoughs for CW significantly increased the loaf volume and softened breadcrumbs more than CW sourdough. Flour qualities of polished flours such as suitable acidity and good buffering capacity caused by the bran fraction were effective for better growth and longer life of yeast in the dough during fermentation. Therefore, application of polished flours in sourdough bread would improve rheological properties of dough and bread as compared with CW sourdough.

The impact of controlled tidal exchange on drainage water quality in acid sulphate soil backswamps

Periodic opening of one-way tidal floodgates was undertaken on two coastal flood mitigation drains to promote exchange with estuarine water and improve drain water quality. The drains were located in areas with acid sulphate soils and their drainage water frequently had high acidity and low dissolved oxygen (DO). Tidal exchange via floodgate opening generally raised drain water pH levels through dilution and/or neutralisation of acidity. Increases in DO and moderation of extreme diurnal DO fluctuations were also observed. The magnitude and stability of the improved physico-chemical conditions was highly dependant on the volume and quality of tidal ingress water. Relatively rapid reversion (hours to days) in drain water pH and DO was observed once floodgates were closed again. The rate of reversion following floodgate closure was strongly related to outflow volumes, antecedent drain water quality conditions and groundwater levels. Floodgate opening caused changes in longitudinal drain water gradients and has potential to slow net drainage rates during non-flood periods. However, complex site specific interactions between drain water and adjacent groundwater can also occur. At one location, a 4-day floodgate opening event caused recharge of adjacent acid groundwater during the opening phase, raising the potentiometric groundwater level above local low tide minima. This was followed by tidally modulated draw down of acid groundwater and enhanced acid export in the period immediately following floodgate closure. There are also practical considerations, which limit the efficacy of floodgate opening as an acid management strategy. The low elevation (close to mean sea level) of some acid sulphate soil backswamps, combined with seasonal migration of the estuarine salt wedge, means there is considerable potential for saline overtopping of what is currently agricultural land. This constrains the magnitude and duration of controlled tidal exchange. Also, it is during wet periods that acid drainage outflow to the estuary is greatest. At such times the salinity and acid buffering capacity of estuarine water is often low, thus reducing the capacity of tidal exchange waters to neutralise acidity.

Effect of Acid Buffering Capacity on the Long-Term Mobility of Heavy Metals in Clay Liner

The pH and Eh effects on the mobility of zinc within landfill clay liner are investigated by modified batch tests on Osaka marine clay with cultivation of native microorganisms in the soil. The long-term mobility of zinc in landfill clay liner is discussed based on the pH buffering capacity of liner soil-leachate system. Tests results show that both pH and Eh conditions control the mobility of zinc in Osaka marine clay. Low redox potentials and neutral to basic pH conditions in landfill sites tend to prompt the insolubilization of zinc in landfill liner, in particular in the case where marine clay is used to serve as a natural liner material at offshore landfill sites. In the long-term perspective, oxygen will intrude finally into the landfill, which switches the anaerobic decomposition into an aerobic one and results a decrease in pH. Titration test results indicate that the newly generated leachate has a higher acid buffering capacity than the aged leachate, while leachates from MSW incineration ash have high hydroxides alkalinity at pH>8. Test results reveal that both of the wastes and clay liner possess enough acid buffering capacity to consume the protons produced in organic oxidation reactions. Therefore, high levels of remobilization of heavy metals are not expected in the long-term perspective.

Characterization and Preliminary Assessment of a Sorbent Produced by Accelerated Mineral Carbonation

This study shows that calcium silicate/aluminate-based materials can be carbonated to produce sorbents for metal removal. The material chosen for investigation, cement clinker, was accelerated carbonated, and its structural properties were investigated using X-ray diffraction (XRD), scanning electron microscopy, thermal gravimetric and differential thermal analysis, nuclear magnetic resonance spectroscopy, and nitrogen gas adsorption techniques. The principal carbonation reactions involved the transformation of dicalcium silicate, tricalcium silicate, and tricalcium aluminate into a Ca/Al-modified amorphous silica and calcium carbonate. It was found that carbonated cement had high acid buffering capacity, and maintained its structural integrity within a wide pH range. The uptake of Pb(II), Cd(II), Zn(II), Ni(II), Cr(II), Sr(II), Mo(VI), Cs(II), Co(II), and Cu(II) from concentrated (1000 mg L(-1)) single-metal solutions varied from 35 to 170 mg g(-1) of the carbonate cement. The removal of metals was hardly effected by the initial solution pH due to the buffering capability of the carbonated material. The kinetics of Pb, Cd, Cr, Sr, Cs, and Co removal followed a pseudo-second-order kinetic model, whereas the equilibrium batch data for Cu fitted the pseudo-first-order rate equation. PHREEQC simulation supported by XRD analysis suggested the formation of metal carbonates and silicates, calcium molybdate, and chromium (hydro)oxide. Cesium was likely to be adsorbed by Ca/Al-modified amorphous silica.

Effect of wood acidity and catalyst on UF resin gel time

Abstract Knowledge of pH and buffering capacity of raw fiber materials is important for understanding the effects of raw material on the curing rate of urea formaldehyde (UF) resin, used for panel manufacturing, especially with some less-desirable wood materials such as bark, top, and commercial thinnings. The effects of pH and buffering capacity as well as catalyst content on the gel time of UF resin were investigated. The results obtained from this study indicate that bark has a lower pH value as well as higher acid and alkaline buffering capacities than wood of the same species due to their extractives. The pH values of the raw fiber materials studied decrease with increased absolute and relative acid buffering capacity due to the increased absolute acidity mass in the solution. At lower levels of added catalyst, the effect of raw material pH on UF resin gel time is significant, while it is insignificant at higher catalyst contents. This may be due to the acidity of wood, which is the main acid catalyst source of the mixture at lower levels of added catalyst, while at higher levels, catalyst is the main source. With higher catalyst contents, all studied raw materials mixed with UF resin result in a longer gel time than does UF resin alone.

English

Copper Flat, located in southwestern New Mexico, approximately 23 miles southwest of Truth or Consequences, is a porphyry copper deposit with associated gold, silver, molybdenum, and sulfide minerals. The stock contains a 75 million-year-old quartz monzonite breccia pipe forming the center of an eroded andesite strato-volcano. Quintana Minerals Corporation mined the property for three months in 1982 producing 7.4 million pounds of copper, 2,306 ounces of gold, and 55,966 ounces of silver. Mining activities ceased because of low copper prices. The mining equipment was dismantled and sold. Since no mining activities have occurred since 1982, the site is an excellent field laboratory for studying the behavior of metals and sulfide minerals exposed with waste rock and tailings in the arid southwest. There is a 12.8-acre pit and pit lake on site that is located near the center of the breccia pipe. The entire study undertaken at Copper Flat focused on the potential impact of the pit lake, the waste rock piles, and the tailing impoundment on the local surface and groundwater quality; however, this paper focuses on the pit lake. The pit lake has been sampled at least 65 times between 1989 and 1997. The pH of the lake is typically neutral to alkaline, with exception occurring in 1992 and 1993, where the pH dropped as low as 4.4. At least one intermittent seep from the pit wall has been sampled and the results reported a pH of 2.64, a total dissolved solid concentration (TDS) of 12,770 milligrams per liter (mg/L), and a sulfate concentration of 790 mg/L. The andesitic host rocks surrounding the ore body and groundwater inflow have a high acid buffering capacity as shown by the partial dissolution of calcite and the precipitation of gypsum and goethite. The alkalinity of the groundwater and host rocks quickly neutralizes and dilutes acidic discharges into the pit lake. Groundwater samples collected from monitoring wells located down gradient from the pit lake indicate groundwater chemistry is similar before and after the excavation of the pit.

Enhanced Electrokinetic Remediation of Heavy Metals in Glacial Till Soils Using Different Electrolyte Solutions

Previous electrokinetic remediation studies involving the geochemical characterization of heavy metals in high acid buffering soils, such as glacial till soil, revealed significant hexavalent chromium migration towards the anode. The migration of cationic contami- nants, such as nickel and cadmium, towards the cathode was insignificant due to their precipitation under the high pH conditions that result when the soil has a high acid buffering capacity. Therefore the present laboratory study was undertaken to investigate the performance of different electrolyte ~or purging! solutions, which were introduced to either dissolve the metal precipitates and/or form soluble metal complexes. Tests were conducted on a glacial till soil that was spiked with Cr~VI! ,N i~II!, and Cd~II! in concentrations of 1,000, 500, and 250 mg/kg, respectively, under the application of a 1.0 VDC/cm voltage gradient. The electrolyte solutions tested were 0.1M EDTA ~ethylenediaminetetraacetic acid!, 1.0M acetic acid, 1.0M citric acid, 0.1M NaCl/0.1M EDTA, and 0.05M sulfuric acid/0.5 M sulfuric acid. The results showed that 46 - 82% of the Cr~VI! was removed from the soil, depending on the purging solution used. The highest removal of Ni~II! and Cd~II! was 48 and 26%, respectively, and this removal was achieved using 1.0M acetic acid. Although cationic contaminant removal was low, the use of 0.1M NaCl as an anode purging solution and 0.1M EDTA as a cathode purging solution resulted in significant contaminant migration towards the soil regions adjacent to the electrodes. Compared to low buffering capacity soils, such as kaolin, the removal of heavy metals from the glacial till soil was low, and this was attributed to the more complex composition of glacial till. Overall, this study showed that the selection of the purging solutions for the enhanced removal of heavy metals from soils should be primarily based upon the contaminant characteristics and the soil composition.

The Natural Defenses of Copper Flat Sierra County, New Mexico

Copper Flat, located in southwestern New Mexico, approximately 23 miles southwest of Truth or Consequences, is a porphyry copper deposit with associated gold, silver, molybdenum, and sulfide minerals. The stock contains a 75 million-year-old quartz monzonite breccia pipe forming the center of an eroded andesite strato-volcano. Quintana Minerals Corporation mined the property for three months in 1982 producing 7.4 million pounds of copper, 2,306 ounces of gold, and 55,966 ounces of silver. Mining activities ceased because of low copper prices. The mining equipment was dismantled and sold. Since no mining activities have occurred since 1982, the site is an excellent field laboratory for studying the behavior of metals and sulfide minerals exposed with waste rock and tailings in the arid southwest. There is a 12.8-acre pit and pit lake on site that is located near the center of the breccia pipe. The entire study undertaken at Copper Flat focused on the potential impact of the pit lake, the waste rock piles, and the tailing impoundment on the local surface and groundwater quality; however, this paper focuses on the pit lake. The pit lake has been sampled at least 65 times between 1989 and 1997. The pH of the lake is typically neutral to alkaline, with exception occurring in 1992 and 1993, where the pH dropped as low as 4.4. At least one intermittent seep from the pit wall has been sampled and the results reported a pH of 2.64, a total dissolved solid concentration (TDS) of 12,770 milligrams per liter (mg/L), and a sulfate concentration of 790 mg/L. The andesitic host rocks surrounding the ore body and groundwater inflow have a high acid buffering capacity as shown by the partial dissolution of calcite and the precipitation of gypsum and goethite. The alkalinity of the groundwater and host rocks quickly neutralizes and dilutes acidic discharges into the pit lake. Groundwater samples collected from monitoring wells located down gradient from the pit lake indicate groundwater chemistry is similar before and after the excavation of the pit.

Thermoreversible gel formulation containing sodium lauryl sulfate as a potential contraceptive device.

The contraceptive properties of a gel formulation containing sodium lauryl sulfate were investigated in both in vitro and in vivo models. Results showed that sodium lauryl sulfate inhibited, in a concentration-dependent manner, the activity of sheep testicular hyaluronidase. Sodium lauryl sulfate also completely inhibited human sperm motility as evaluated by the 30-sec Sander-Cramer test. The acid-buffering capacity of gel formulations containing sodium lauryl sulfate increased with the molarity of the citrate buffers used for their preparations. Furthermore, experiments in which semen was mixed with undiluted gel formulations in different proportions confirmed their physiologically relevant buffering capacity. Intravaginal application of the gel formulation containing sodium lauryl sulfate to rabbits before their artificial insemination with freshly ejaculated semen completely prevented egg fertilization. The gel formulation containing sodium lauryl sulfate was fully compatible with nonlubricated latex condoms. Taken together, these results suggest that the gel formulation containing sodium lauryl sulfate could represent a potential candidate for use as a topical vaginal spermicidal formulation to provide fertility control in women.

Effect of pH control at the anode for the electrokinetic removal of phenanthrene from kaolin soil

Polycyclic aromatic hydrocarbon (PAH)-contaminated soils exist at numerous sites, and these sites may threaten public health and the environment because many PAH compounds are toxic, mutagenic, and/or carcinogenic. PAHs are also hydrophobic and persistent, so conventional remediation methods are often costly or inefficient, especially when the contaminants are present in low permeability and/or organic soils. An innovative technique, electrokinetically enhanced in situ flushing, has the potential to increase soil–solution–contaminant interaction and PAH removal efficiency for low permeability soils; however, the electrolysis reaction at the anode may adversely affect the remediation of low acid buffering capacity soils, such as kaolin. Therefore, the objective of this study was to improve the remediation of low acid buffering soils by controlling the pH at the anode to counteract the electrolysis reaction. Six bench-scale electrokinetic experiments were conducted, where each test employed one of three different flushing solutions, deionized water, a surfactant, or a cosolvent. For each of these solutions, tests were performed with and without a 0.01 M NaOH solution at the anode to control the pH. The test using deionized water with pH control generated a higher electroosmotic flow than the equivalent test performed without pH control, but the electroosmotic flow difference between the surfactant and cosolvent tests with and without pH control was minor compared to that observed with the deionized water tests. Controlling the pH was beneficial for increasing contaminant solubilization and migration from the soil region adjacent to the anode, but the high contaminant concentrations that resulted in the middle or cathode soil regions indicates that subsequent changes in the soil and/or solution chemistry caused contaminant deposition and low overall contaminant removal efficiency.

English

Many land reclamation technologies have been used on mining-impacted lands within the Clark Fork River Basin Superfund sites over the past 20 years. Several sites are examples of in-situ reclamation or phytostabilization. Since phytostabilization does not remove metal contaminants, the permanence of this technology as a remedial alternative has received significant scrutiny. Many of these projects have had limited long term monitoring, and as such, the permanence of these efforts is undocumented. However, the continued existence of these sites provides a unique opportunity to evaluate the permanence of in-situ treatment strategies. The purpose of this investigation was to generate sufficient data and information from areas receiving phytostabilization treatments, varying in age from 6 to 19 years, so that the permanence and self-sufficiency of the established and reconstructed ecosystem(s) can be assessed. Six different field sites were selected that represent phytostabilization implementation in different landscape positions, using slightly different equipment, and at different times. The sites are similar in that each was degraded because of impacts from the metal mine/mill/smelter processes. Soils or tailings at the sites contain acid producing materials and are elevated in metal concentrations compared to adjacent, non-impacted landscapes. At each site, neutralizing amendments were added to raise the soil or waste pH to a target level of seven, and at some sites, other amendments were also added. Vegetation response variables observed or measured at the six sites included cover, species richness, evidence of reproduction, evidence of nutrient cycling, evidence of succession, and biomass. Soil response variables measured included pH, acid buffering capacity, and metal concentrations. This paper will present these data and discuss the efficacy of phytostabilization in terms of the sites' ability to sustain current land use and their ability to support other possible land uses. The permanence of the amendments to perform their function of attenuating acid production and immobilization of metals will also be addressed.

Acid buffering capacity and potential acidification of cotton soils in northern New South Wales

Soil acidity has been of major concern in Australia since European settlement. Acidification processes have been accelerated due to agricultural activities such as N fertiliser application and leguminous N-fixation in farm rotations. In this paper, we measured the acid buffering capacity (pHBC) of Vertosols, soils used predominantly for growing cotton in northern New South Wales. The pHBC values were used to calculate decrease in soil pH assuming net acid input due to agricultural practices. We combined the acidification results with geostatistics to spatially simulate the decline in soil pH of surface soils over time. The results indicate that it would take 10–417 years for soil pH to decrease by 1 unit on an assumed acid input of 5�kmol�H+/ha.year. Soil pH will drop by 1 unit within 100 years for 90% of the soils and within 15 years for 10% of the soils. This reflects the variability of the pHBC for the studied soils. In 50 years from present, most of the eastern and north-western parts of the study region may become highly acidic with soil pH declining to 5.5. There may be a potential threat to sustainable agriculture from acidification in the region, although more work needs to be done to corroborate the counter-effects of water fluxes and carbonate dissolution. Sensitivity analysis indicates that even at low levels of acid input, some areas in the study region may experience significant decline in soil pH in the surface layer.

Experimental study on mine spoils during superficial geochemical processes

Based on the mineral and chemical compositions of spoils taken from the Shilu Cu-Mo deposit and Hetai gold deposit, the leaching and batch experiments were made on spoils taken from these two deposits using the leaching column designed by the authors. The experimental results showed that it is not always true that the mine drainage is acidic. Its acidity depends on acid-buffering capacity of gangue, host rock and its alteration mineral assemblage. The composition of the drainage water is related with the interaction between superficial or underground water and solid materials in the spoils, including minerals, hydroxides and amorphous substances. The leaching extent of the element is related with its occurrence form in the deposit. The preferential flow results in leaching-out of heavy metals in large amounts. So it is important to prevent the generating of preferential flow in the system. The results will provide very important grounds for the comprehensive management of land and ecological rehabilitation of the mine site.

The effect of consumption of foods that differ in energy density and/or sodium bicarbonate supplementation on subsequent diet selection in sheep

The short-term consumption of foods that differed in energy density (ED) and/or NaHCO3 supplementation, on subsequent food intake and diet selection in sheep were measured. Thirty sheep weighing 35·9 (SD 2·89) KG WERE USED. TWO FOODS WERE FORMULATED: H HAD 11 AND L HAD 8 MJ METABOLIZABLE ENERGY/KG FRESH MATTER. FOUR FURTHER FOODS WERE FORMULATED BY ADDING EITHER 40 G NAHCO3/KG OR 16·5 G NACL/KG TO FOODS H AND L. NACL WAS ADDED TO GIVE THE SAME NA CONCENTRATION AS WITH 40 G NAHCO3/KG TO CONTROL FOR ANY EFFECTS OF NA PER SE. IN A PRELIMINARY TEST, IT WAS FOUND THAT A 2 H CONSUMPTION OF FOOD H SUPPLEMENTED WITH NAHCO3 COULD BUFFER POTENTIAL IMPACT ON THE RUMEN ENVIRONMENT OF SUBSEQUENT CONSUMPTION OF FOOD H ALONE (AS JUDGED BY RUMEN PH AND ACID-BUFFERING CAPACITY); HOWEVER, IT WAS NOT AS EFFECTIVE AS THE CONSUMPTION OF FOOD L ALONE IN DOING SO. EACH FOOD TREATMENT WAS OFFERED TO ONE OF SIX GROUPS (N 5) FOR 2 H FOLLOWING 16 H OF FOOD DEPRIVATION. SHEEP WERE THEN OFFERED A CHOICE BETWEEN H AND L FOR A FURTHER 6 H. SUPPLEMENTING H OR L WITH EITHER NAHCO3 OR NACL HAD NO SIGNIFICANT EFFECT ON EITHER INTAKE OR DIET SELECTION. ED SIGNIFICANTLY (P<0·01) AFFECTED INTAKE DURING THE 2 H SINGLE FEEDING PERIOD, WITH SHEEP OFFERED H OR L CONSUMING 540 AND 663 (sed 37) g respectively, but had no effect on subsequent intake during the choice period. During the choice period all sheep showed a preference for food H, but sheep previously offered L selected significantly more H (0·873 g/g) than sheep previously offered H (0·544 (sed 0·028) g/g; P<0·001). It is concluded that short-term consumption of foods that differ in ED, and hence in their potential impact on the rumen environment, significantly affects subsequent diet selection. This is in agreement with the hypothesis that ruminant animals select a diet to help maintain the rumen environment within a certain physiological range. Food H with 40 g NaHCO3 added/kg may not have been sufficient to affect subsequent diet selection. It is suggested that larger, rather than smaller, changes in the rumen environment achieved through previous feeding should be expected to alter subsequent diet selection.

The effect of consumption of foods that differ in energy density and/or sodium bicarbonate supplementation on subsequent diet selection in sheep.

The short-term consumption of foods that differed in energy density (ED) and/or NaHCO3 supplementation, on subsequent food intake and diet selection in sheep were measured. Thirty sheep weighing 35.9 (sd 2.89) kg were used. Two foods were formulated: H had 11 and L had 8 MJ metabolizable energy/kg fresh matter. Four further foods were formulated by adding either 40 g NaHCO3/kg or 16.5 g NaCl/kg to foods H and L. NaCl was added to give the same Na concentration as with 40 g NaHCO3/kg to control for any effects of Na per se. In a preliminary test, it was found that a 2 h consumption of food H supplemented with NaHCO3 could buffer potential impact on the rumen environment of subsequent consumption of food H alone (as judged by rumen pH and acid-buffering capacity); however, it was not as effective as the consumption of food L alone in doing so. Each food treatment was offered to one of six groups (n 5) for 2 h following 16 h of food deprivation. Sheep were then offered a choice between H and L for a further 6 h. Supplementing H or L with either NaHCO3 or NaCl had no significant effect on either intake or diet selection. ED significantly (P<0.01) affected intake during the 2 h single feeding period, with sheep offered H or L consuming 540 and 663 (sed 37) g respectively, but had no effect on subsequent intake during the choice period. During the choice period all sheep showed a preference for food H, but sheep previously offered L selected significantly more H (0.873 g/g) than sheep previously offered H (0.544 (sed 0.028) g/g; P<0.001). It is concluded that short-term consumption of foods that differ in ED, and hence in their potential impact on the rumen environment, significantly affects subsequent diet selection. This is in agreement with the hypothesis that ruminant animals select a diet to help maintain the rumen environment within a certain physiological range. Food H with 40 g NaHCO3 added/kg may not have been sufficient to affect subsequent diet selection. It is suggested that larger, rather than smaller, changes in the rumen environment achieved through previous feeding should be expected to alter subsequent diet selection.

Diet selection of sheep: sodium bicarbonate, but not the offering of hay, modifies the effect of urea on diet selection

AbstractThe hypotheses tested were that the expected preference of sheep for a food with adequate rumen degradable protein (RDP) supplemented with urea would be reduced both by the addition of a buffer (sodium bicarbonate (SB)) and by offering ad libitum access to hay. A control food (C), calculated to be adequate in its ratio of effective RDP to fermentable metabolizable energy (fME), was formulated. Other foods were made by adding 12·5 (U1) or 25 (U2) g urea per kg fresh matter (FM) to C and 20 g SB per kg FM to C, U1and U2. The acid buffering capacity (ABC) of each food was measured in vitro. The experiment consisted of two successive periods, each of 4 weeks. Ninety-eight female, Texel ✕ Greyface sheep were randomly allocated to 14 groups each with seven animals. Groups 1 to 6 were offered one of: C, U2, C + SB, U2+ SB, C with hay or U2with hay throughout the experiment. Groups 7 to 10 were offered the choices of C v. U1or C v. U2, either with or without hay in a change-over design; animals that received hay during period 1 (groups 8 and 10) did not do so during period 2 and vice versa (groups 7 and 9). Groups 11 to 14 (no. = 7) were offered the choices of C v. U1or C v. U2, either with or without SB supplemented to both foods, in a change-over design. Adding either urea, or SB, or both to C had no effects on intake or live-weight gain when offered alone. Both supplements significantly (P 0·001) increased the ABC of food C. Throughout the experiment hay consumption was very low (overall mean: 23 (s.e. 2·5) g hay per sheep day). Offering hay caused no change in the preference for the urea-supplemented foods. Sheep offered the choices C v. U1or C v. U2, with neither hay nor SB, selected 0.466 (s.e. 0·036) and 0.588 (s.e. 0·025) kg/kg total food intake (TFI) of U1and U2respectively. The proportions of the urea-supplemented foods were significantly reduced (P 0.01) by SB supplementation: to 0.348 (s.e.0·045) and 0·406 (s.e.0·059) kg/kg TFI of U1and U2respectively. The effect of SB addition on the diet selection of sheep could be due to its buffering properties. When SB is added to both foods the need for urea to be used as a buffer is reduced with a consequent decrease in the proportion selected as the urea-supplemented food. Effects of diet on buffering may override other diet selection objectives, such as the avoidance of an excess intake of RDP.

Chemistry of fog waters in California's Central Valley—Part 3: concentrations and speciation of organic and inorganic nitrogen

Although organic nitrogen (ON) has been found to be a ubiquitous and significant component in wet and dry deposition, almost nothing is known about its concentration or composition in fog waters. To address this gap, we have investigated the concentration and composition of ON in fog waters collected in Davis, in California's Central Valley. Significant quantities of dissolved organic nitrogen (DON) were found in these samples, with a median concentration of 303 μM N (range=120–1630 μM N). DON typically represented approximately 16% of the total dissolved nitrogen (inorganic+organic) in Davis fog waters. The median concentration of nitrogen in free amino acids and alkyl amines was 16 μM N (range=3.8–120 μM N), which accounted for 3.4% of the DON in Davis fogs. Thus, although the absolute concentrations of free amino compounds were significant, they were only a minor component of the DON pool. Combined amino nitrogen (e.g., proteins and peptides) was present at higher concentrations and accounted for 6.1–29% (median=16%) of DON. Overall, free and combined amino compounds typically accounted for a median value of 22% of DON in the fog waters. The high concentrations of DON found, and the fact that amino and other N-containing organic compounds can serve as nitrogen sources for microorganisms and plants, indicate that atmospheric ON compounds likely play an important role in nitrogen cycling in the Central Valley. In addition, due to the basicity of some N functional groups, ON compounds likely contribute to the previously observed acid buffering capacity of Central Valley fog waters. Finally, a comparison of fog waters with fine particles (PM 2.5) collected from the same site during the same period of time indicated that the median concentrations (mol N m −3-air) of total water-soluble ON, free amino nitrogen and total amino nitrogen were very similar in the fog water and PM 2.5. Given the high water solubility of many organic N compounds, this result suggests that ON might contribute to the hygroscopic properties of atmospheric particles.

Heavy metal speciation and leaching behaviors in cement based solidified/stabilized waste materials

A circuit board printing factory sludge containing high concentrations of copper, zinc and lead was stabilized and solidified (S/S) with different portions of ordinary Portland cement (OPC) and pulverized fly ash (PFA). The chemical speciation and leaching behavior of heavy metals in these cement-based waste materials were studied by different sequential extraction procedures, standard toxicity characteristic leaching procedure (TCLP) and progressive TCLP tests. The sequential extraction results showed that more than 80% of Cu, Pb and Zn were associated with Fraction 2 (weak acid soluble, extracted with 1 M NaOAc at pH 5.0 with a solid to liquid ratio of 1:60). This indicated that the heavy metals could exist in the S/S matrix as metal hydrated phases or metal hydroxides precipitating on the surface of calcium silicate hydrates (CSH), PFA and sludge particles. The progressive TCLP test results and MINTEQA2 calculation also showed the importance of Cu and Zn oxides during the leaching process. The leaching behaviors of these metals in the S/S waste materials were mainly controlled by the alkaline nature and acid buffering capacity of the S/S matrix. During the progressive TCLP tests, the alkaline conditions and acid buffering capacity of the matrix decreased with the dissolution of calcium hydroxide and CSH, therefore, the leaching of heavy metals in the S/S waste materials increased. The leaching of heavy metals in the S/S materials can be considered as a pH dependent and corresponding metal hydroxide solubility controlled process.

Chemical Characteristics and Acid Buffering Capacity of Surface Soils in Japanese Forests

To determine the geological distribution of acid buffering capacity and exchangeable Al of forest soils in Japan, surface soils under forest vegetation were collected nationwide from a total of 1,034 sites. Generally, surface soils in Japanese forests are mostly acidic and low in both exchangeable cation content and exchangeable Al. The median of soil pH(H2O), total exchangeable cations, and exchangeable Al are 5.1, 76 mmol(+)Kg−1, and 19.6 mmol(+)kg−1, respectively. Acid buffering capacities of selected soils were determined using a soil column, which was comparable to the capacity that resulted from cation exchanges with protons. Soils with high buffering capacity and low exchangeable Al are widely distributed in Japan, and overlap with the areas of Andisol distribution. Volcanogenic materials seem to mask soil characteristics derived from underlying geology even though they are not Andisols. However, central to western Honshu Island, Shikoku Island, and northern Kyushu Island showed weak acid buffering capacities with high exchangeable Al potential in surface soils.