Impact of simulated solar irradiation on disinfection byproduct precursors

The Sacramento-San Joaquin Delta is the major drinking water source for 23 million California residents. Consequently, many studies have examined disinfection byproduct (DBP) formation in relation to Delta dissolved organic carbon (DOC) concentration. However, DOC characteristics within the Delta are not the same as those entering downstream water treatment facilities. As water is transferred to Southern California through the California Aqueduct, a 714.5 km-open channel, it is exposed to sunlight, potentially altering DBP precursors. We collected water from three sites within the Delta and one nearthe California Aqueduct, representing different DOC sources, and irradiated them in a solar simulator at a dose equivalent to that received during four days conveyance in the aqueduct. Photolytic changes in DOC were assessed by measuring CO2 and organic acid production, fluorescence, and ultraviolet absorbance over time. Trihalomethane (THM) and haloacetic acid (HAA) formation potentials, as well as the distribution of hydrophobic, transphilic, and hydrophilic acid fractions were determined at exposures equivalent to one and four days. Solar irradiation significantly decreased ultraviolet absorbance and fluorescence intensity, produced organic acids, and increased the hydrophilic fraction of waters. These changes in DOC caused a shift in bromine incorporation among the THM and HAA species. Our results are the first to demonstrate the importance of sunlight in altering DOC with respect to DBP formation.     

Restored wetlands as a source of disinfection byproduct precursors

The effects of a restored wetland system in the Sacramento Valley, California on the production of dissolved organic carbon (DOC) and nitrogen (DON) and the formation potential of common disinfection byproducts (DBPs: trihalomethanes, haloacetonitriles, and chloral hydrate) were examined. Additionally, the effects of photodegradation and microbial degradation on dissolved organic matter properties and reactivitywith respect to DBP formation potential (DBP-FP) were evaluated. The wetlands increased DOC and DON concentrations by a factor of 2.2 and 1.9 times, respectively, but had little influence on the DOC and DON quality as compared to their source waters. The increase in DOC and DON concentrations increased the formation potential of all DBP species by >100%. Solar radiation and microbial degradation reduced the trihalomethane formation potential by 24 and 10%, respectively, during a 14 day incubation. In contrast, the chloral hydrate formation potential was increased by 22% after phototreatment. Results indicate that current flood-pulse management practices with a 2-3 week residence time could lead to wetlands acting as a source of DBP precursors. Enhanced DBP-FP is especially important as these wetlands contribute to a watershed that is a drinking water source for more than 23 million people.     

Disinfection byproduct relationships and speciation in chlorinated nanofiltered waters

The formation and speciation of disinfection byproducts (DBPs) resulting from chlorination of nanofilter permeates obtained from various source water locations and membrane types are examined. Specific ultraviolet absorbance and bromide utilization are shown to decrease following nanofiltration. Both dissolved organic carbon (DOC) concentration and ultraviolet absorbance at 254 nm were found to correlate strongly with trihalomethane (THM), haloacetic acid (HAA), and total organic halide (TOX) concentrations in chlorinated nanofilter permeates, suggesting that they can be employed as surrogates for DBPs in nanofiltered waters. Because smooth curves were obtained for individual THM and HAA species as well as bromine and chlorine incorporation into THMs and HAAs as a function of Br-/DOC molar ratio, it is likely that mole fractions of these DBPs are more strongly influenced by chlorination conditions, Br-, and DOC concentrations than NOM source and membrane type. Mole fractions of mono-, di-, and trihalogenated HAAs were found to be independent of Br-/DOC. Even at a very low Br-/DOC of 2.9microM/mM, the mixed bromochloro- and tribromoacetic acids constituted 20% of total HAAs on a molar basis. This increased to approximately 50% as Br-/DOC increased to approximately 25microM/mM or more, proving that a large fraction of HAAs may not be covered under existing federal regulations. Total THM and HAA9 concentrations decreased in permeate waters with increasing Br-/DOC suggesting that nanofilter permeates are limited with respect to DBP precursors.     

Photoinduced oxidation of antimony(III) in the presence of humic acid

Interactions of antimony with natural organic matter (NOM) are important for the fate of Sb in aquatic systems. The kinetics of the photosensitized oxidation of Sb(III) to Sb(V) in the presence of Suwannee River Humic Acid (SRHA) was investigated using UV-A and visible light (medium-pressure mercury lamp). At a concentration of 5 mg L(-1) dissolved organic carbon (DOC) the light-induced reaction was 9000 times faster (rate coefficient k(exp) = 7.0 +/- 0.05 x 10(-4) s(-1)) than the dark reaction and followed pseudo-first-order kinetics. Rates increased linearly with the concentration of DOC. Between pH 4 and 8 rates increased by a factor of 5. Further results and kinetic considerations indicate that singlet oxygen, hydroxyl radicals, hydrogen peroxide, and hydroperoxyl radicals/superoxide are not important photooxidants in this system, while other NOM-derived reactive species, in particular excited triplet states and/or phenoxyl radicals, seem to be relevant. The dependence of rate coefficients on Sb(III)/DOC ratio was consistent with a two binding site model including (i) a strong binding site at low concentration inducing fast oxidation, (ii) a weak binding site at high concentration inducing slower oxidation, and (iii) the even slower oxidation of Sb(OH)3. Photoirradiation of natural water samples spiked with Sb(III) showed that the oxidation rates could be well predicted based on DOC.     

Dissolved organic carbon reduces uranium bioavailability and toxicity. 1. Characterization of an aquatic fulvic acid and its complexation with uranium[VI

Fulvic acid (FA) from a tropical Australian billabong (lagoon) was isolated with XAD-8 resin and characterized using size exclusion chromatography, solid state cross-polarization magic angle spinning, 13C nuclear magnetic resonance spectroscopy, elemental analysis, and potentiometric acid-base titration. Physicochemical characteristics of the billabong FA were comparable with those of the Suwannee River Fulvic Acid (SRFA) standard. The greater negative charge density of the billabong FA suggested it contained protons that were more weakly bound than those of SRFA, with the potential for billabong water to complex less metal contaminants, such as uranium (U). This may subsequently influence the toxicity of metal contaminants to resident freshwater organisms. The complexation of U with dissolved organic carbon (DOC) (10 mg L(-1)) in billabong water was calculated using the HARPHRQ geochemical speciation model and also measured using flow field-flow fractionation combined with inductively coupled plasma mass-spectroscopy. Agreement between both methods was very good (within 4% as U-DOC). The results suggest that in billabong water at pH 6.0, containing an average DOC of 10 mg L(-1) and a U concentration of 90 μg L(-1), around 10% of U is complexed with DOC.     

Biological oxygen demand dynamics in the lower San Joaquin River, California

Dissolved oxygen less than 5 mg L(-1) (U. S. EPA advisory level) commonly occurs in the lower San Joaquin River (SJR), California. Most acute episodes typically occur in late summer and fall. The oxygen deficit can stress and kill aquatic organisms, often inhibiting the upstream migration of Chinook salmon (Oncorhynchus tshawytscha). This 5 year study examined watershed-scale spatial and temporal biological oxygen demand (BOD) loads and the primary components believed to contribute to BOD: ammonium, algal biomass, nonalgal particulate organic carbon, dissolved organic carbon, and dissolved organic nitrogen. Samples were collected bimonthly at 15 sites during the summers of 2000 and 2001 and from three lower mainstem sites from May 2002 to March 2005. BOD loads showed a downstream increase in parallel with increasing algal biomass loads resulting primarily from in-stream growth. BOD loads from measured tributaries and drains accounted for 28% and 39% of the BOD load at the downstream Vernalis site in 2000 and 2001, respectively. Algal C was positively correlated (r=0.80) with BOD, explaining 64% of BOD variance for data collected from 2001 to 2005. Less than 20% of BOD was found in the dissolved fraction (<0.45 microm). We conclude that algal biomass is the primary contributor to BOD loads in the lower SJR, upstream of Mossdale.     

Role of aluminum speciation in the removal of disinfection byproduct precursors by a coagulation process

Humic acid (HA) was extracted and separated into different molecular weight (MW) fractions, then coagulated by aluminum chloride and polyaluminum chloride (PACl). The removal of disinfection byproduct (DBP) precursors and the aluminum speciation variation of the coagulants were investigated in detail. In particular, the role of aluminum speciation in the removal of DBP precursors was discussed. During the coagulation process, AlCl3 hydrolyzed into dominating in situ Al13 species at pH 5.5. The in situ Al13 species exhibited better removal ability for haloacetic acid (HAA) precursors than PACl. At pH 7.5, in situ hydrolyzed Al13 species of AlCl3 decomposed into dimeric Al species. In this case, preformed Al13 of PACl had a high removal ability of HAA precursors. Specially, the greatest reduction of HAA precursors with a low MW (<30 kDa) was through charge neutralization at pH 5.5, and that of HAA precursors in high MW (> 30 kDa) fractions was through adsorption at pH 7.5. Different from HAA precursors, the in situ Al13 species did not have a high removal ability of trihalomethane (THM) precursors. Therefore, PACl exhibited a better removal ability of THM precursors than AlCl3 at different pH values. In the different MW fractions, the greatest reduction of THM precursors was through charge neutralization at pH 5.5.     

Partitioning of fluorotelomer alcohols to octanol and different sources of dissolved organic carbon

Interest in the environmental fate of fluorotelomer alcohols (FTOHs) has spurred efforts to understand their equilibrium partitioning behavior. Experimentally determined partition coefficients for FTOHs between soil/water and air/water have been reported, but direct measurements of partition coefficients for dissolved organic carbon (DOC)/water (K(doc)) and octanol/ water(K(ow)) have been lacking. Here we measured the partitioning of 8:2 and 6:2 FTOH between one or more types of DOC and water using enhanced solubility or dialysis bag techniques, and also quantified K(ow) values for 4:2 to 8:2 FTOH using a batch equilibration method. The range in measured log K(doc) values for 8:2 FTOH using the enhanced solubility technique with DOC derived from two soils, two biosolids, and three reference humic acids is 2.00-3.97 with the lowest values obtained for the biosolids and an average across all other DOC sources (biosolid DOC excluded) of 3.54 +/- 0.29. For 6:2 FTOH and Aldrich humic acid, a log K(doc) value of 1.96 +/- 0.45 was measured using the dialysis technique. These average values are approximately 1 to 2 log units lower than previously indirectly estimated K(doc) values. Overall, the affinity for DOC tends to be slightly lower than that for particulate soil organic carbon. Measured log K(ow) values for 4:2 (3.30 +/- 0.04), 6:2 (4.54 +/- 0.01), and 8:2 FTOH (5.58 +/- 0.06) were in good agreement with previously reported estimates. Using relationships between experimentally measured partition coefficients and C-atom chain length, we estimated K(doc) and K(ow) values for shorter and longer chain FTOHs, respectively, that we were unable to measure experimentally.     

Characterization of high molecular weight disinfection byproducts resulting from chlorination of aquatic humic substances

Aquatic humic substances react with chlorine to produce numerous disinfection byproducts (DBPs) during chlorination of drinking water. Although low molecular weight (MW) chlorinated DBPs have been intensively studied over the past several decades, relatively little is known about high MW chlorinated DBPs (above 500 Da) that may be associated with adverse health implications. In this work, carrier-free radioactive 36Cl was introduced into a Suwannee River fulvic acid sample to label the chlorine-containing DBPs. By combining the fractionation techniques of ultrafiltration (UF) and size exclusion chromatography (SEC) with the detection of 36Cl, UV, and dissolved organic carbon (DOC), the high MW region in the SEC-36Cl profiles of the chlorinated sample with and without UF was defined. SEC-UV and SEC-DOC profiles were found to be approximately indicative of SEC-36Cl profiles for the high MW region. The MW distribution shows that the high MW chlorinated DBPs were highly dispersed with an average MW around 2000 Da based on calibration with polystyrene sulfonate standards. The Cl/C atomic ratios of the high MW DBPs were roughly constant (0.025), which is much lower than those of the common known chlorinated DBPs.     

Tribromopyrrole,brominated acids,and other disinfection byproducts produced by disinfection of drinking water rich in bromide

Using gas chromatography/mass spectrometry (GC/MS), we investigated the formation of disinfection byproducts (DBPs) from high bromide waters (2 mg/L) treated with chlorine or chlorine dioxide used in combination with chlorine and chloramines. This study represents the first comprehensive investigation of DBPs formed by chlorine dioxide under high bromide conditions. Drinking water from full-scale treatment plants in Israel was studied, along with source water (Sea of Galilee) treated under carefully controlled laboratory conditions. Select DBPs (trihalomethanes, haloacetic acids, aldehydes, chlorite, chlorate, and bromate) were quantified. Many of the DBPs identified have not been previously reported, and several of the identifications were confirmed through the analysis of authentic standards. Elevated bromide levels in the source water caused a significant shift in speciation to bromine-containing DBPs; bromoform and dibromoacetic acid were the dominant DBPs observed, with very few chlorine-containing compounds found. Iodo-trihalomethanes were also identified, as well as a number of new brominated carboxylic acids and 2,3,5-tribromopyrrole, which represents the first time a halogenated pyrrole has been reported as a DBP. Most of the bromine-containing DBPs were formed during pre-chlorination at the initial reservoir, and were not formed by chlorine dioxide itself. An exception wasthe iodo-THMs, which appeared to be formed by a combination of chlorine dioxide with chloramines or chlorine (either added deliberately or as an impurity in the chlorine dioxide). A separate laboratory study was also conducted to quantitatively determine the contribution of fulvic acids and humic acids (from isolated natural organic matter in the Sea of Galilee) as precursor material to several of the DBPs identified. Results showed that fulvic acid plays a greater role in the formation of THMs, haloacetic acids, and aldehydes, but 2,3,5-tribromopyrrole was produced primarily from humic acid. Because this was the first time a halopyrrole has been identified as a DBP, 2,3,5-tribromopyrrole was tested for mammalian cell cytotoxicity and genotoxicity. In comparison to other DBPs, 2,3,5-tribromopyrrole was 8x, 4.5x, and 16x more cytotoxic than dibromoacetic acid, 3-chloro-4-(dichloromethyl)-5-hydroxy-2-[5H]-furanone [MX], and potassium bromate, respectively. 2,3,5-Tribromopyrrole also induced acute genomic damage, with a genotoxic potency (299 microM) similar to that of MX.     

Seasonal variations in concentrations of pharmaceuticals and personal care products in drinking water and reclaimed wastewater in southern California

Southern California imports nearly all of its potable water from two sources: the Colorado River and the California State Water Project (Sacramento-San Joaquin River Basin). Sewage treatment plant effluent (STPE) heavily impacts both of these sources. A survey of raw and treated drinking water from four water filtration plants in San Diego County showed the occurrence of several polar organic "pharmaceuticals and personal care products" (PPCP). These included phthalate esters, sunscreens, clofibrate, clofribric acid, ibuprofen, triclosan, and DEET. Several of these were also found in the finished water, such as di(ethylhexyl) phthalate, benzophenone, ibuprofen, and triclosan. Occurrence and concentrations of these compounds were highly seasonally dependent, and reached maximums when the flow of the San Joaquin River was low and the quantity of imported water was high. The maximum concentrations of the PPCPs measured in the raw water were correlated with low flow conditions in the Sacramento-San Joaquin Delta that feeds the State Water Project. The PPCP concentrations in raw imported water in the summer months approached that of reclaimed nonpotable wastewater.     

Drowning in disinfection byproducts? Assessing swimming pool water

Disinfection is mandatory for swimming pools: public pools are usually disinfected by gaseous chlorine or sodium hypochlorite and cartridge filters; home pools typically use stabilized chlorine. These methods produce a variety of disinfection byproducts (DBPs), such as trihalomethanes (THMs), which are regulated carcinogenic DBPs in drinking water that have been detected in the blood and breath of swimmers and of nonswimmers at indoor pools. Also produced are halogenated acetic acids (HAAs) and haloketones, which irritate the eyes, skin, and mucous membranes; trichloramine, which is linked with swimming-pool-associated asthma; and halogenated derivatives of UV sun screens, some of which show endocrine effects. Precursors of DBPs include human body substances, chemicals used in cosmetics and sun screens, and natural organic matter. Analytical research has focused also on the identification of an additional portion of unknown DBPs using gas chromatography (GC)/mass spectrometry (MS) and liquid chromatography (LC)/MS/MS with derivatization. Children swimmers have an increased risk of developing asthma and infections of the respiratory tract and ear. A 1.6-2.0-fold increased risk for bladder cancer has been associated with swimming or showering/bathing with chlorinated water. Bladder cancer risk from THM exposure (all routes combined) was greatest among those with the GSTT1-1 gene. This suggests a mechanism involving distribution of THMs to the bladder by dermal/inhalation exposure and activation there by GSTT1-1 to mutagens. DBPs may be reduced by engineering and behavioral means, such as applying new oxidation and filtration methods, reducing bromide and iodide in the source water, increasing air circulation in indoor pools, and assuring the cleanliness of swimmers. The positive health effects gained by swimming can be increased by reducing the potential adverse health risks.     

Selective oxidation of key functional groups in cyanotoxins during drinking water ozonation

Chemical kinetics were determined for the reactions of ozone and hydroxyl radicals with the three cyanotoxins microcystin-LR (MC-LR), cylindrospermopsin (CYN) and anatoxin-a (ANTX). The second-order rate constants (k(O3)) at pH 8 were 4.1 +/- 0.1 x 10(5) M(-1) s(-1) for MC-LR, approximately 3.4 x 10(5) M(-1) s(-1) for CYN, and approximately 6.4 x 10(4) M(-1) s(-1) for ANTX. The reaction of ozone with MC-LR exhibits a k(O3) similar to that of the conjugated diene in sorbic acid (9.6 +/- 0.3 x 10(5) M(-1) s(-1)) at pH 8. The pH dependence and value of k(O3) for CYN at pH > 8 (approximately 2.5 +/- 0.1 x 10(6) M(-1) s(-1)) are similar to deprotonated amines of 6-methyluracil. The k(O3) of ANTX at pH > 9 (approximately 8.7 +/- 2.2 x 10(5) M(-1) s(-1)) agrees with that of neutral diethylamine, and the value at pH < 8 (2.8 +/- 0.2 x 10(4) M(-1) s(-1)) corresponds to an olefin. Second-order rate constants for reaction with OH radicals (*OH), k(OH) for cyanotoxins were measured at pH 7 to be 1.1 +/- 0.01 x 10(10) M(-1) s(-1) for MC-LR, 5.5 +/- 0.01 x 10(9) M(-1) s(-1) for CYN, and 3.0 +/- 0.02 x 10(9) M(-1) s(-1) for ANTX. Natural waters from Switzerland and Finland were examined for the influence of variations of dissolved organic matter, SUVA254, and alkalinity on cyanotoxin oxidation. For a Swiss water (1.6 mg/L DOC), 0.2, 0.4, and 0.8 mg/L ozone doses were required for 95% oxidation of MC-LR, CYN, and ANTX, respectively. For the Finnish water (13.1 mg/L DOC), >2 mg/L ozone dose was required for each toxin. The contribution of hydroxyl radicals to toxin oxidation during ozonation of natural water was greatest for ANTX > CYN > MC-LR. Overall, the order of reactivity of cyanotoxins during ozonation of natural waters corresponds to the relative magnitudes of the second-order rate constants for their reaction with ozone and *OH. Ozone primarily attacks the structural moieties responsible for the toxic effects of MC-LR, CYN, and ANTX, suggesting that ozone selectively detoxifies these cyanotoxins.     

Bonding of ppb levels of methyl mercury to reduced sulfur groups in soil organic matter

The strong binding of CH3Hg+ to natural organic matter (NOM) in soils and waters determines the speciation of CH3Hg under aerobic conditions and indirectly its bioavailability and rates of demethylation. In lab experiments, halides (Cl, Br, I) were used as competing ligands to determine the strength of CH3Hg+ binding to solid-phase soil organic carbon (SOC) and to dissolved soil organic carbon (DOC) as a function of time, pH, and concentration of halide. Experiments were conducted with native concentrations of CH3Hg (1.7-9.8 ng g(-1)) in organic soils, and equilibrium concentrations of CH3Hg were determined by species-specific-isotope-dilution (SSID) gas-chromatography-induced-coupled-plasma-mass-spectrometry (GC-ICP-MS). A simple model (RS- + CH3Hg+ = CH3HgSR; log KCH3HgSR) was used to simulate the binding to SOC and DOC, in which the binding sites (RSH) were independently determined by X-ray absorption near-edge structure (XANES) spectroscopy. The pKa values of RSH groups were fixed at 8.50 and 9.95, reflecting the two major thiol groups in proteins. Log KCH3HgSR values determined for SOC and DOC were similar, showing a range of 15.6-17.1 for all experiments covering a pH range of 2.0-5.1. Despite large differences in affinities between Cl, Br, and I for CH3Hg+, determined constants were independent of type and concentration of halide used in the experiments (log KCH3HgSR = 16.1-16.7 at pH 3.5-3.6). Even if our log KCH3HgSR values were conditional in that they decreased with pH above 3.5, they were in fair agreement with stability constants determined for the association between CH3Hg+ and thiol groups in well-defined organic molecules (log K1 = 15.7-17.5). Speciation calculations based on our results show that, in absence of substantial concentrations of inorganic sulfides, neutral chloro-complexes (CH3HgCl) and free CH3Hg+ reach concentrations on the order of 10(-17)-10(-18) M at pH 5 in soil solutions with 3 x 10(-5) M of chloride.     

Haloacetic acid and trihalomethane formation from the chlorination and bromination of aliphatic beta-dicarbonyl acid model compounds

While it is known that resorcinol- and phenol-type aromatic structures within natural organic matter (NOM) react during drinking water chlorination to form trihalomethanes (THMs), limited studies have examined aliphatic-type structures as THM and haloacetic acid (HAA) precursors. A suite of aliphatic acid model compounds were chlorinated and brominated separately in controlled laboratory-scale batch experiments. Four and two beta-dicarbonyl acid compounds were found to be important precursors for the formation of THMs (chloroform and bromoform (71-91% mol/mol)), and dihaloacetic acids (DXAAs) (dichloroacetic acid and dibromoacetic acid (5-68% mol/mol)), respectively, after 24 h at pH 8. Based upon adsorbable organic halide formation, THMs and DXAAs, and to a lesser extent mono and trihaloacetic acids, were the majority (> 80%) of the byproducts produced for most of the aliphatic beta-dicarbonyl acid compounds. Aliphatic beta-diketone-acid-type and beta-keto-acid-type structures could be possible fast- and slow-reacting THM precursors, respectively, and aliphatic beta-keto-acid-type structures are possible slow-reacting DXAA precursors. Aliphatic beta-dicarbonyl acid moieties in natural organic matter, particularly in the hydrophilic fraction, could contribute to the significant formation of THMs and DXAAs observed after chlorination of natural waters.     

Risk-based approach to evaluate the public health benefit of additional wastewater treatment

The City of Stockton, CA operates a wastewater treatment facility that discharges tertiary treated effluent during the summer and secondary treated effluent during the winter to the San Joaquin River. Investigations were carried out between 1996 and 2002 to provide insight regarding the potential public health benefit that may be provided by year-round tertiary treatment. A hydraulic model of the San Joaquin River and a dynamic disease transmission model integrated a wide array of disparate data to estimate the level of viral gastroenteritis in the population under the two treatment scenarios. The results of the investigation suggest that risk of viral gastroenteritis attributable to the treatment facility under the existing treatment scheme is several orders of magnitude below the 8-14 illnesses per 1000 recreation events considered tolerable by U.S. EPA, and winter tertiary treatment would further reduce the existing risk by approximately 15-50%. The methodologies employed herein are applicable to other watersheds where additional water treatment is being considered to address public health concerns from recreation in receiving waters.     

Characterization of disinfection byproduct precursors based on hydrophobicity and molecular size

Natural organic matter (NOM) from five water sources was fractionated using XAD resins and ultrafiltration membranes into different groups based on hydrophobicity and molecular weight (MW), respectively. The disinfection byproduct formation from each fraction during chlorination and chloramination was studied. In tests using chlorination, hydrophobic and high MW (e.g., >0.5 kDa) precursors produced more unknown total organic halogen (UTOX) than corresponding hydrophilic and low MW (e.g., <0.5 kDa) precursors. Trihaloacetic acid (THAA) precursors were more hydrophobic than trihalomethane (THM) precursors. The formation of THM and THAA was similar among different fractions for a water with low humic content. Hydrophilic and low MW (<0.5 kDa) NOM fractions gave the highest dihaloacetic acid (DHAA) yields. No significant difference was found for DHAA formation among different NOM fractions during chloramination. Increasing pH from 6 to 9 led to lower TOX formation for hydrophobic and high MW NOM fractions but had little impact on TOX yields from hydrophilic and low MW fractions. Bromine and iodine were more reactive with hydrophilic and low MW precursors as measured by THM or HAA formation than their corresponding hydrophobic and high MW precursors. However, hydrophobic and high MW precursors produced more UTOX when reacting with bromine and iodine.     

Mobile source and livestock feed contributions to regional ozone formation in Central California

A three-dimensional air quality model with 8 km horizontal resolution was applied to estimate the summertime ozone (O(3)) production from mobile sources and fermented livestock feed in California's San Joaquin Valley (SJV) during years 2000, 2005, 2010, 2015, and 2020. Previous studies have estimated that animal feed emissions of volatile organic compounds (VOCs) have greater O(3) formation potential than mobile-source VOC emissions when averaging across the entire SJV. The higher spatial resolution in the current study shows that the proximity of oxides of nitrogen (NO(x)) and VOC emissions from mobile sources enhances their O(3) formation potential. Livestock feed VOC emissions contributed 3-4 ppb of peak O(3) (8-h average) in Tulare County and 1-2 ppb throughout the remainder of the SJV during the CCOS 2000 July-August episode. In total, livestock feed contributed ~3.5 tons of the ground level peak O(3) (8 h average) in the SJV region, and mobile VOC contributed ~12 tons in this episode. O(3) production from mobile sources is declining over time in response to emissions control plans that call for cleaner fuels and engines with advanced emissions controls. Projecting forward to the year 2020, mobile-source VOC emissions are predicted to produce ~3 tons of the ground level peak O(3)(8-h average) and livestock feed VOC emissions are predicted to contribute ~2.5 tons making these sources nearly equivalent.     

Fluctuations of dissolved organic matter in river used for drinking water and impacts on conventional treatment plant performance

Natural organic matter (NOM) in drinking water supplies can provide precursors for disinfectant byproducts, molecules that impact taste and odors, compounds that influence the efficacy of treatment, and other compounds that are a source of energy and carbon for the regrowth of microorganisms during distribution. NOM, measured as dissolved organic carbon (DOC), was monitored daily in the White River and the Indiana-American water treatment plant over 22 months. Other parameters were either measured daily (UV-absorbance, alkalinity, color, temperature) or continuously (turbidity, pH, and discharge) and used with stepwise linear regressions to predict DOC concentrations. The predictive models were validated with monthly samples of the river water and treatment plant effluent taken over a 2-year period after the daily monitoring had ended. Biodegradable DOC (BDOC) concentrations were measured in the river water and plant effluent twice monthly for 18 months. The BDOC measurements, along with measurements of humic and carbohydrate constituents within the DOC and BDOC pools, revealed that carbohydrates were the organic fraction with the highest percent removal during treatment, followed by BDOC, humic substances, and refractory DOC.     

Use of Br and Se in peat to reconstruct the natural and anthropogenic fluxes of atmospheric Hg: A 10000-year record from Caribou Bog, Maine

Using Br and Se as reference elements, the natural and anthropogenic fluxes of atmospheric Hg were reconstructed for the past 10,000 years using peat cores from Caribou Bog, ME. In the ombrotrophic peat layers, the average background Hg accumulation rate (AR) was 1.7 +/- 1.3 microg m(-2) year(-1) which is comparable with the natural rate of atmospheric Hg accumulation reported in other retrospective studies. The average Hg AR determined using all peat samples dating from preindustrial times, including minerotrophic peat, was slightly greater (3.1 +/- 2.3 microg m(-2) year(-1)) which may reflect differences in canopy interception due to the changes in plant communities, aquatic inputs, or possibly climatic factors. The maximum Hg AR (32 microg m(-2) year(-1)) occurred ca. 1961 A.D. In samples predating the settlement by Europeans, there is a linear correlation between the AR of Hg and those of Br and Se; this relationship allows both Br and Se to be used to calculate the natural AR of Hg (Hgnat). The difference between Hg AR and Hg(nat) is the Hg AR in excess of background (Hg(ex)). Because Hg(ex) was positive only after ca. 1840 A.D., it is assumed to represent the anthropogenic Hg component. By the late 19th century, Hg(ex) deposition was equal to the natural flux. At the peak in Hg deposition in 1961 A.D., Hgex made up >90% of total atmospheric Hg deposition. The AR in the uppermost peat decreased to 25% of peak values by 2000 A.D.