Sacramento Valley Research Articles

Body Condition of Wintering Pacific Greater White‐Fronted Geese

ABSTRACTExtreme changes to key waterfowl habitats in the Klamath Basin (KB) on the Oregon–California border and the Sacramento Valley (SV) in California, USA, have occurred since 1980. The spatial distribution of Pacific greater white‐fronted geese (Anser albifrons sponsa; geese) has likewise changed among these areas and population size has grown from 79,000 to >600,000 geese during the same period. To assess the effects of landscape changes and spatial‐temporal distribution of geese, we collected Pacific greater white‐fronted geese during winters of 2009–2010 and 2010–2011 in the KB and SV and compared their body condition to geese collected during 1979–1980 and 1980–1981. We modeled body and lipid mass to assess body condition for each sex independently and examined the influence of collection day, year, and region. Body condition of geese varied throughout the winter and within years in a nonlinear fashion. We detected an increase in body condition in both sexes during December and January in the SV, which corresponds with improved habitat conditions and increases seen in other species in the region. Body condition upon arrival in fall migration varied by year for females and by year and region for males. Males and females arrived in poorer body condition during 2010–2011 than all other study years and males in the KB during 2010–2011 had extremely low lipid mass, reflecting poor regional habitat conditions induced by drought. Body condition of females varied over spring, by year, and by region and regional effects were evident for males. Body condition was significantly higher for geese in the SV than in the KB during spring. Our results suggest that Pacific greater white‐fronted geese have adapted to a changing landscape and have adjusted historical spatial use patterns to take advantage of more favorable conditions in the SV between 1979 and 2010. © 2021 The Wildlife Society.

Timing of school desegregation experience and late‐life cognition in the Study of Healthy Aging in African Americans (STAR) cohort

AbstractBackgroundPrior studies suggest segregated school experiences are associated with poorer late‐life cognition among African Americans. However, less is known about how the timing of school desegregation in the individual’s lifecourse or historically is associated with cognition for younger cohorts.MethodThe Study of Healthy Aging in African Americans (STAR) is a cohort of community‐dwelling Kaiser Permanente members residing in the San Francisco Bay area and Sacramento valley. The study has enrolled 722 African Americans (half ages 50‐64, half 65+) and aims to understand lifecourse processes that contribute to cognitive aging disparities. Experiences of segregation were self‐reported and modeled three ways: 1) having attended only segregated schools vs. only integrated; 2) by life stage when first transitioned to a desegregated school (i.e. 1st‐6th, 7th‐9th or 10th‐12th grades); and 3) the historical timing of school desegregation relative to the 1954 Brown vs. Board of Education decision mandating school integration (many districts were reluctant to integrate in a timely manner). Executive function, semantic memory and verbal memory measured with the Spanish and English Neuropsychological Assessment Scales (SENAS) were z‐standardized and averaged for overall cognition. Linear regression was used for analysis; models controlled for age, gender, and education.ResultParticipant mean age was 68 (8.7) and 69% were female. Compared with participants who only attended integrated schools (ref.; n=438), those who only attended segregated schools (n=145) had significantly lower overall cognition, executive function and semantic memory (see table). Those who transitioned from segregated to integrated schools between 7th and 9th grade (n=51) had worse executive function and semantic memory than those who only attended integrated schools; we did not observe significant associations for those who transitioned to integrated schools in 1st‐6th grades (n=44), or 10th‐12th grades (n=43). We observed no differences in cognition by historical timing of desegregation.ConclusionOlder African Americans who attended only segregated schools or experienced desegregation in 7th‐9th grades had worse later‐life cognitive test scores than those who attended racially integrated schools. Our findings suggest that only attending segregated schools and the timing of school desegregation in the lifecourse may have implications for understanding cognitive aging among African Americans.

Nativity differences in lifecourse socioeconomic position and late‐life cognition among KHANDLE participants

AbstractBackgroundSocioeconomic position (SEP) in childhood and adulthood is associated with late‐life cognition. Less is known about how SEP changes may be associated with late‐life cognition in diverse cohorts.MethodsThe Kaiser Healthy Aging and Diverse Life Experiences Study (KHANDLE) is a cohort of community‐dwelling Kaiser Permanente members who reside in the San Francisco Bay area and Sacramento valley (n=1,708; Asians (24%), Blacks (26%), Latinos (20%) and Whites (30%)). KHANDLE aims to evaluate how lifecourse and sociocultural factors influence late‐life brain health and cognitive decline and contribute to race/ethnic disparities. We used linear regression to test the association between lifecourse SEP trajectories and late‐life cognition and tested if these associations differed by US vs. foreign nativity. Childhood SEP is a composite of parents’ education (≥HS vs. <HS), childhood hunger, and self‐reported family financial status. Adult SEP included participants’ education (≥HS vs. <HS), late‐life low income status (e.g. qualified for low‐income welfare programs), and self‐reported social status. Participants were classified as having consistently high SEP (HH), low childhood/high adult SEP (LH), high childhood/low adult SEP (HL), or consistently low SEP (LL). Executive function, semantic memory and verbal episodic memory measured with the Spanish and English Neuropsychological Assessment Scales (SENAS) were z‐standardized and averaged for overall cognition. Pooled analyses adjusted for age, race/ethnicity, gender, and foreign nativity.ResultsOverall, participants classified as LH did not differ from HH (ref.) in any cognitive domain, while those classified as HL and LL had lower cognition than HH in all domains (see table). We observed a significant interaction of US vs. foreign birth and lifecourse SES trajectory for semantic memory (p=0.01), but no other domain. Stratified analyses demonstrated a similar pattern to pooled. However, foreign‐born participants HL participants had significantly lower overall cognition (p=0.03), and verbal memory (p=0.02) than US‐born HL participants. By contrast, foreign‐born LH participants performed significantly better than US‐born LH in semantic memory (p=0.01).ConclusionsThose with high Adult SEP had the best cognitive function, regardless of childhood SEP or nativity. In some measures of cognition, foreign‐born HL participants performed worse than US‐born, while foreign‐born LH performed better.

Life cycle assessment of rice husk torrefaction and prospects for decentralized facilities at rice mills

Utilization of rice husk, an abundant global residual biomass, represent a large opportunity for increasing the share of bioenergy in the power sector. The present work assesses the life cycle emissions of rice husk torrefaction in different reaction conditions and the techno-economic prospects for decentralized torrefaction facilities at rice mills. First, a cradle-to-gate life cycle assessment (LCA) is performed for processing rice husk into torrefied pellets for energy generation. Four system configurations of different temperature and torrefaction medium are considered for torrefied rice husk (TRH) pellet production. Medium torrefaction in inert medium shows the highest GHG emissions of about 0.043 kg CO2 eq/MJ of TRH pellet whereas severe torrefaction in oxidative medium shows the lowest GHG emissions of 0.021 kg CO2 eq/MJ of TRH pellet. The environmental impacts of torrefaction in partially oxidative medium and at higher temperatures are lower, only if a significant portion of the torgas and condensate is efficiently utilized. Second, a techno-enviro-economic evaluation is performed for multiple scenarios of utilizing raw or torrefied rice husk (partially oxidative conditions) for power generation. A case study of the rice mills in the Sacramento valley of California is considered, with an annual supply of about 0.2 million tons of rice husk, to operate a 26.5 MW biopower plant. A centralized facility at the power plant resulted in highest GHG emissions, and a rented mobile facility resulted in highest annual costs. The most desired scenario of having localized facilities at the rice mills proved most cost-effective, with excess TRH breakeven price of 61 USD/ton for medium torrefaction and 471 USD/ton for severe torrefaction. Instead of excess TRH, if the entire TRH is available for sale, the same scenario estimated the average breakeven price of 14.9 USD/ton and 21.1 USD/ton respectively. Sensitivity analysis for a single mill explains the role of factors such as availability of rice husk (milling capacity), transportation distance, and solid mass yield on the breakeven price, costs, and the GHG emissions.

Exploring variability in rangeland soil organic carbon stocks across California (USA) using a voluntary monitoring network

Rangelands are an economically and ecologically important land type that make up more than 40% of California's land area. Protecting and, where appropriate, increasing soil organic carbon (SOC) stocks across these rangelands can help to promote on-site and public ecosystem services including forage production and climate change mitigation. A necessary step toward appropriately and effectively stewarding SOC is understanding baseline variability in SOC stocks and identifying how that variability relates to factors such as climate, soil texture, and topography. While these relationships have been examined at broader spatial scales and in other contexts, analysis for California's rangelands remains lacking. We leveraged a voluntary ecological monitoring program consisting of 45 working ranches to explore how SOC varies with geographic distance, climate, vegetation, soil type, and topography within and across three regions of California. We found that there was large variability in soil C stocks across the state, with the Central Coast region storing more SOC than the San Joaquin and Sacramento Valleys. Network-wide, SOC stocks ranged from 4.83 to 63.54 Mg ha−1 for 0–10 cm depth and 12.15–205.37 Mg ha−1 for 0–40 cm depth. As hypothesized, climate was the strongest predictor of SOC stocks across the entire network, and in general other predictor groups became more important at the regional level. Within each region, we found on average a sixfold difference in SOC stocks, with much of the variation unexplained by the predictor variables included. While some differences in SOC likely result from unaccounted variables such as soil mineralogy, conceivably some of the variation is also due to differences in past and current land use—indicating that there is potential to rebuild SOC through management.

First Report of Phytophthora chlamydospora Causing Crown and Root Rot on Almond in California

First Report of <i>Phytophthora chlamydospora</i> Causing Crown and Root Rot on Almond in California

Dispossessed: How Predatory Bureaucracy Foreclosed on the American Middle Class by Noelle Stout

Reviewed by: Dispossessed: How Predatory Bureaucracy Foreclosed on the American Middle Class by Noelle Stout Nicholas L. Caverly Noelle Stout, Dispossessed: How Predatory Bureaucracy Foreclosed on the American Middle Class. Berkeley: University of California Press, 2019. 280 pp. More than a decade on from the Great Recession, it is evident that the economic crash continues to reverberate in the downward mobility of middle-class Americans. Noelle Stout's Dispossessed: How Predatory Bureaucracy Foreclosed on the American Middle Class shows us why. She does so by examining erosion of middle-class livelihoods following the early 21st century collapse in home values and subsequent wave of mortgage foreclosures. Between 2006 and 2013, more than 13.7 million households entered foreclosure proceedings. Despite federal programs that allocated hundreds of billions to assist these homeowners, more than nine million households lost their homes to foreclosure. Stout follows the bureaucratic routines—fine print, convoluted applications, lost files, misdirected calls, outright lies—through which banks and financial institutions profited by denying more than seventy percent of applications for aid. As Stout writes, "My task is to make these bureaucratic dramas as vivid and memorable as the more visible scenes, the evictions and tent cities that dominated news coverage of the crisis" (7). This task strikes at the technical systems of political economy in order to theorize the moral economy of debt relations. In so doing, it offers a model for public anthropology that advances theoretical debates through deep engagement with issues of pressing concern. Dispossessed is ethnographically grounded in Northern California's Sacramento Valley. Not only is the region home to one of the greatest concentrations of mortgage foreclosures, it is also where Stout has generations [End Page 573] of family ties. This methodological standpoint allows Stout to observe a disjuncture between the contemporary dispossession of middle-class people and the federally-administered programs that allowed her relations to construct a middle-class existence following the Great Depression. By contrast to government-run New Deal projects, the response to the Great Recession was routed through the same lending bureaucracies that precipitated the financial crisis to begin with. As Dispossessed attends to this shift, it tracks how neoliberal economic policies have made the entrapment of middle-class people in unpayable debts a constitutive feature of twenty-first century capitalism. Using everyday moments of dispossession, Stout identifies how "post-middle-class-life projects" came to characterize much of contemporary American existence (14). Dispossessed considers the conditions of predatory bureaucracy through five chapters. In turn, the chapters trace a chronological route though the making of the foreclosure crisis and its aftermath. Chapter 1 centers how the Sacramento Valley has been the recursive site of speculation and dispossession. As the valley became a heartland of middle-class homeownership during the second half of the twentieth century, it built upon settler-colonial territory that codified seizure as the foundation of American economic practice. Chapter 2 focuses on how subprime loan agents leveraged working class Black and Latinx social networks in the neighborhood of Oak Park to route people into mortgages they could not afford. Across the country, similar techniques saw foreclosures hit first and hardest in places like Oak Park, where they compounded the cumulative effects of racist housing markets. Chapter 3 moves through a series of middle-income neighborhoods across the valley. While people in places like Oak Park lost their homes before federal mortgage assistance programs existed, these programs promised a lifeline for homeowners with greater class and racial privilege. And yet, privileged homeowners also found themselves facing evictions after corporate lending bureaucracies denied their applications for mortgage modifications, citing incomplete information and lost paperwork. Chapter 4 turns to the employees of predatory bureaucracies who processed loan modification applications. While these employees were sympathetic to borrowers, their attempts to modify loans were undermined by circuitous applications and workflows demanded by Wall Street lenders. Stout contends these inefficiencies are not faults in bureaucratic rationalization, but purposeful designs that enabled lenders to expand the scope of profit and deny modifications. Chapter 5 returns to [End Page 574] middle-class homeowners after banks denied their modification requests. Contrasts between government bailouts of financial institutions and their own impending dispossession drove middle-class...

Identification and Characterization of Neofabraea kienholzii and Phlyctema vagabunda Causing Leaf and Shoot Lesions of Olive in California.

California produces over 95% of the olives grown in the United States. In 2017, California's total bearing acreage for olives was 14,570 hectares producing 192,000 tons of olives valued at $186.6 million. During the early spring of 2016, unusual leaf and shoot lesions were detected in olive trees from superhigh-density orchards in the Northern San Joaquin and Sacramento valleys of California. Affected trees displayed numerous leaf and shoot lesions developing at wounds created by mechanical harvesters. The 'Arbosana' cultivar was highly affected by the disease, whereas the disease was sporadic in 'Arbequina' and not found in 'Koroneiki' cultivar. Two fungal species, Neofabraea kienholzii and Phlyctema vagabunda, were found to be consistently associated with the disease, and Koch's postulates were completed. Species identity was confirmed by morphology and molecular data of the partial large subunit rDNA, the internal transcribed spacer region, and partial beta-tubulin region. The disease signs and symptoms are described and illustrated.

The Native South: New Histories and Enduring Legacies ed. by Tim Alan Garrison and Greg O'Brien

Reviewed by: The Native South: New Histories and Enduring Legacies ed. by Tim Alan Garrison and Greg O'Brien Steven J. Peach (bio) The Native South: New Histories and Enduring Legacies. Edited by Tim Alan Garrison and Greg O'Brien. (Lincoln: University of Nebraska Press, 2017. Pp. xx, 279. $60.00 cloth; $30.00 paper; $60.00 e-book) The Native South: New Histories and Enduring Legacies examines the state of southern Indian history and honors the two scholars who shaped it into a mature field of inquiry, Theda Perdue and her late husband, Michael D. Green. The volume includes original essays from thirteen of the former doctoral students of Perdue and Green, including the volume's editors, Tim Alan Garrison and Greg O'Brien. Moving forward in time from the early eighteenth century to today, Native South examines how southern Indians adapted to Euro-American invasion, diseases, and settlement. In addition to chronological breadth, the collection includes numerous themes. Some essays offer a fresh take on Indian removal, intertribal diplomacy, and European-Indian encounters. Others probe new topics altogether, including southern Indian feminism in the 1970s. No matter the focus, each piece bears the imprint of Perdue and Green. During an interview that O'Brien conducted with his retired advisors in 2012, Theda remarked that "Mike and I have had the great good fortune to see our legacy while we're still living" (p. 31). That [End Page 373] legacy is their students. Taking their cue from Perdue and Green, the contributors to Native South employ the ethnohistorical method. It draws upon historical records, archaeological evidence, oral traditions, and indigenous language materials to study the cultures, worldviews, and concerns of indigenous people over time. Ethnohistory first emerged in the mid-1950s when Indians and their non-Indian allies sued the federal government to reclaim lands stolen by white Americans since the nineteenth century. By the 1970s, as Perdue indicated to O'Brien during the interview, the Civil Rights and Red Power Movements prompted white academics to replace "white man's history" with ethnohistory, which put Native people front and center (p. 13). Consequently, the essays in Native South examine the history of indigenous southerners and demonstrate that these peoples creatively blended elements of white American culture with those of traditional culture to address disease, war, land loss, and other factors resulting from Euro-American colonization. Native South challenges popular assumptions about the southern Indians. David A. Nichols reminds us that Indians "had no more innate inclination for violence than their European contemporaries" (p. 33). Nevertheless, the Chickasaws used that stereotype to their advantage. According to Nichols, the eighteenth-century Chickasaws used their fearsome military power as a source of "capital" to secure trade goods from Europeans and preserve influence in the South (p. 37). In the same vein, Tim Alan Garrison uproots the popular notion that Cherokee removal was inevitable. Studying newspapers and legislative votes from southern states that overwhelmingly favored removal, such as Georgia, he excavates a forceful, if small, opposition to removal by white southern jurists and lawmakers. Unfortunately, white southern opposition to removal was "weak, unorganized, and poorly led" (p. 121). Many contributors insert southern Indian women into the larger drama of nineteenth-century U.S. history. Rose Stremlau interprets the letters of Barbara Longknife, a Cherokee who migrated to California [End Page 374] with her immediate family in 1850. A participant in the Gold Rush, Longknife helped formed a "nascent Cherokee diaspora community" in California (p. 175). Like the white American men who left the Northeast to pan for gold in the Sacramento valley, Longknife seized new economic opportunities but struggled to accumulate wealth. Similar to Stremlau, Malinda Maynor Lowery demonstrates that Chickasaw women in the mid-to-late 1800s made American capitalism their own. To that end, they leveraged their position in the influential Colbert matrilineage to pave new avenues to wealth and, more broadly, to empower Chickasaw sovereignty. In Indian Territory, which became the state of Oklahoma in 1907, women of the Cherokee Nation asserted their social and political influence. Focusing on Cherokee jurisprudence, Julie L. Reed argues that the Cherokee Nation balanced the U.S. legal principle of retributive justice with the...

The Modeled Effects of Rice Field Idling on Groundwater Storage in California’s Sacramento Valley

Rice farmers occupy a potentially important intersection between economics and hydrology in Northern California. While drought makes water an increasingly precious commodity across California, the monetary worth of water is not uniform across different localities and uses. As a result, circumstances have given many Sacramento Valley rice farmers the option to sell their water to users elsewhere, in lieu of using it themselves. Because the sold water is typically surface water that would normally help recharge local aquifers when applied to a field; it is reasonable to suspect that transferring that water elsewhere could adversely affect local aquifers since that recharge would be reduced. This study performs numerical experiments using the United States Geological Survey’s Central Valley Hydrologic Model (CVHM) to better understand the temporal effects of a set of land idling scenarios. CVHM is capable of modeling the entire Central Valley, which encompasses the Sacramento and San Joaquin Valleys, and of representing rice field idling on a large scale. These experiments were executed using historical data to contrast recently typical amounts of rice field idling with scenarios reflecting varying degrees of hypothetical, increased idling. In doing so, this study aims to characterize the nature and potential magnitude of idling rice fields on groundwater storage in the Sacramento Valley. The impact of these scenarios on groundwater storage was quantified relative to an unaltered baseline model scenario. The results of this research show rice field idling will reduce recharge and groundwater storage levels; these results may provide useful information for future policy decisions and provide a basis for future study.

A record of late Holocene paleomegafloods from Little Packer Lake and Razor Slough, Sacramento valley oxbow Lakes

A record of late Holocene paleomegafloods from Little Packer Lake and Razor Slough, Sacramento valley oxbow Lakes

Insights into controls on hexavalent chromium in groundwater provided by environmental tracers, Sacramento Valley, California, USA

Environmental tracers are useful for determining groundwater age and recharge source, yet their application in studies of geogenic Cr(VI) in groundwater has been limited. Environmental tracer data from 166 wells located in the Sacramento Valley, northern California, were interpreted and compared to Cr concentrations to determine the origin and age of groundwater with elevated Cr(VI), and better understand where Cr(VI) becomes mobilized and how it evolves along flowpaths. In addition to major ion and trace element concentrations, the dataset includes δ18O, δ2H, 3H concentration, 14C activity (of dissolved inorganic C), δ13C, 3He/4He ratio, and noble gas concentrations (He, Ne, Ar, Kr, Xe). Noble gas recharge temperatures (NGTs) were computed, and age-related tracers were interpreted in combination to constrain the age distribution in samples and sort them into six different age categories spanning from <60yr old to >10,000yr old. Nearly all measured Cr is in the form of Cr(IV). Concentrations range from <1 to 46μgL−1, with 10% exceeding the state of California’s Cr(VI) maximum contaminant level of 10μgL−1. Two groups with elevated Cr(VI) (⩾5μgL−1) were identified. Group 1 samples are from the southern part of the valley and contain modern (<60yr old) water, have elevated NO3− concentrations (>3mgL−1), and commonly have δ18O values enriched relative to local precipitation. These samples likely contain irrigation water and are elevated due to accelerated mobilization of Cr(VI) in the unsaturated zone (UZ) in irrigated areas. Group 2 samples are from throughout the valley and typically contain water 1000–10,000yr old, have δ18O values consistent with local precipitation, and have unexpectedly warm NGTs. Chromium(VI) concentrations in Group 2 samples may be elevated for multiple reasons, but the hypothesis most consistent with all available data (notably, the warm NGTs) is a relatively long UZ residence time due to recharge through a deep UZ near the margin of the basin. A possible explanation for why Cr(VI) may be primarily mobilized in the UZ rather than farther along flowpaths in the oxic portion of the saturated zone is more dynamic cycling of Mn in the UZ due to transient moisture and redox conditions.

Laboratory investigations of the effects of nitrification-induced acidification on Cr cycling in vadose zone material partially derived from ultramafic rocks

Sacramento Valley (California, USA) soils and sediments have high concentrations of Cr(III) because they are partially derived from ultramafic material. Some Cr(III) is oxidized to more toxic and mobile Cr(VI) by soil Mn oxides. Valley soils typically have neutral to alkaline pH at which Cr(III) is highly immobile. Much of the valley is under cultivation and is both fertilized and irrigated. A series of laboratory incubation experiments were conducted to assess how cultivation might impact Cr cycling in shallow vadose zone material from the valley. The first experiments employed low (7.1mmolN per kg soil) and high (35mmolNkg−1) concentrations of applied (NH4)2SO4. Initially, Cr(VI) concentrations were up to 45 and 60% greater than controls in low and high incubations, respectively. After microbially-mediated oxidation of all NH4+, Cr(VI) concentrations dropped below control values. Increased nitrifying bacterial populations (estimated by measurement of phospholipid fatty acids) may have increased the Cr(VI) reduction capacity of the vadose zone material resulting in the observed decreases in Cr(VI). Another series of incubations employed vadose zone material from a different location to which low (45meqkg−1) and high (128meqkg−1) amounts of NH4Cl, KCl, and CaCl2 were applied. All treatments, except high concentration KCl, resulted in mean soil Cr(VI) concentrations that were greater than the control. High concentrations of water-leachable Ba2+ (mean 38μmolkg−1) in this treatment may have limited Cr(VI) solubility. A final set of incubations were amended with low (7.1mmolNkg−1) and high (35mmolNkg−1) concentrations of commercial liquid ammonium polyphosphate (APP) fertilizer which contained high concentrations of Cr(III). Soil Cr(VI) in the low APP incubations increased to a concentration of 1.8μmolkg−1 (5× control) over 109days suggesting that Cr(III) added with the APP fertilizer was more reactive than naturally-occurring soil Cr(III).

Hygroscopicity and composition of California CCN during summer 2010

We present an overview and analysis of cloud condensation nuclei (CCN) sampled in California by a NOAA WP‐3D aircraft during the 2010 CalNex project. Four distinct geographical regions are characterized, including the Los Angeles basin, the San Joaquin and Sacramento Valleys, and the eastern Pacific Ocean west of southern California. Median size distributions in the Central Valley were unimodal (Dg ∼ 25 nm) with a larger fraction of organic species and smaller fraction of nitrate species in the Sacramento Valley aerosol than in the San Joaquin Valley aerosol. Size distributions in the Los Angeles basin and marine outflow were bimodal (geometric mean diameter, Dg ∼ 30, 90–100 nm) with similar organic fractions and some replacement of nitrate with sulfate in the marine outflow. Both fine particle and CCN concentrations were found to decrease rapidly above the planetary boundary layer (∼2 km altitude), with CCN concentrations in the boundary layer ranging from ∼102–104 cm−3 STP, while fine particle concentrations (0.004–1 μm diameters) ranged from ∼103–105 cm−3STP. The CCN‐active number fraction varied between 0–100% in the Los Angeles Basin and Marine Outflow, but was substantially lower (0–40%) in the San Joaquin and Sacramento Valleys. Values of the hygroscopicity parameter,κ, inferred from the CCN measurements varied from 0.1–0.25, with the highest values in the marine outflow and the lowest values in the Sacramento Valley. The κvalues agreed well with the predictions based on size‐resolved aerosol composition, but were overpredicted by almost twofold when size‐averaged composition was used. CCN closure was assessed for simplified compositional and mixing state assumptions, and it was found that assuming the aerosol to be internally mixed overpredicted CCN concentrations by 30–75% for all air mass types except within the Sacramento Valley, where good closure (overprediction &lt; 10%) was achieved by assuming insoluble organics. Assuming an externally‐mixed aerosol fraction or incorporating size‐resolved composition data improved closure in the other three regions, consistent with the bimodal nature of the aerosol size distribution.

Waste Rice Seed in Conventional and Stripper-Head Harvested Fields in California: Implications for Wintering Waterfowl

Abstract Waste rice seed is an important food for wintering waterfowl and current estimates of its availability are needed to determine the carrying capacity of rice fields and guide habitat conservation. We used a line-intercept method to estimate mass-density of rice seed remaining after harvest during 2010 in the Sacramento Valley (SACV) of California and compared results with estimates from previous studies in the SACV and Mississippi Alluvial Valley (MAV). Posterior mean (95% credible interval) estimates of total waste rice seed mass-density for the SACV in 2010 were 388 (336–449) kg/ha in conventionally harvested fields and 245 (198–307) kg/ha in stripper-head harvested fields; the 2010 mass-density is nearly identical to the mid-1980s estimate for conventionally harvested fields but 36% lower than the mid-1990s estimate for stripped fields. About 18% of SACV fields were stripper-head harvested in 2010 vs. 9–15% in the mid-1990s and 0% in the mid-1980s; but due to a 50% increase in planted rice area, total mass of waste rice seed in SACV remaining after harvest in 2010 was 43% greater than in the mid-1980s. However, total mass of seed-eating waterfowl also increased 82%, and the ratio of waste rice seed to seed-eating waterfowl mass was 21% smaller in 2010 than in the mid-1980s. Mass-densities of waste rice remaining after harvest in SACV fields are within the range reported for MAV fields. However, because there is a lag between harvest and waterfowl use in the MAV but not in the SACV, seed loss is greater in the MAV and estimated waste seed mass-density available to wintering waterfowl in SACV fields is about 5–30 times recent MAV estimates. Waste rice seed remains an abundant food source for waterfowl wintering in the SACV, but increased use of stripper-head harvesters would reduce this food. To provide accurate data on carrying capacities of rice fields necessary for conservation planning, trends in planted rice area, harvest method, and postharvest field treatment should be tracked and impacts of postharvest field treatment and other farming practices on waste rice seed availability should be investigated.

Ozone pollution regimes modeled for a summer season in California’s San Joaquin Valley: A cluster analysis

Abstract This study demonstrates an application of cluster analysis to model simulation data for California’s San Joaquin Valley (SJV) for the purpose of identifying meteorologically representative pollution regimes. Principal component analysis is employed to facilitate exploring and visualizing temporal variations in highly resolved gridded model data. Six regimes are clustered according to the spatial distribution of SJV 8 h ozone maxima. Meteorological effects (temperature and winds) are shown to explain the observed ozone spatial distributions in the SJV, and their relationship to those in upwind San Francisco Bay Area air basin (SFB) under certain prevailing wind flow patterns. In general, average ozone levels in the SJV increase with temperature, while their spatial distributions depend on flow regimes, especially the strength of sea breezes and upslope flows. More ventilated flow regimes, associated with stronger sea breeze and upslope flows, cause eastward transport of pollutants, increasing ozone in the southeastern SJV and decreasing it in the northwest SJV. The opposite occurs during the most stagnant conditions associated with the weakest sea breeze and upslope flows. The two most prominent relationships between the SFB and SJV were found to be associated with the most ventilated and the most stagnant conditions, respectively, indicating a strong inter-basin transport (or the lack thereof) event. Spatial representativeness of existing measurement sites and the confounding influences of emission changes on clustering results are also investigated. Existing measurement sites are able to capture ozone spatial patterns in the SFB and Sacramento Valley (SV), whereas those along the western side of the SJV are under-represented. Differences in day-of-week emissions produce minor effects on spatial ozone distributions and the clusters are largely stable under these changes.

Speciation of Mercury (II) and Methylmercury in Cloud and Fog Water

The fate of oxidized mercury (Hg) in clouds and fogs is affected by the complexation of oxidized Hg(Ⅱ) with other chemical species present in cloud and fog water. Metal complexation often influences the types of reactions available to a metal in an aqueous system. The influence of pH, major inorganic ions, and organic acids on the complexation of Hg(Ⅱ) and methylmercury (MeHg) was examined for a range of cloud and fog water compositions. Fog water was collected in the San Joaquin Valley, CA and rain water was collected at Devil's Lake State Park, WI to provide additional measurements of the chemical conditions of atmospheric media. A thermodynamic model was used to determine the speciation of Hg(Ⅱ) and methylmercury (MeHg) over a range of atmospherically-relevant cloud and fog compositions. The speciation of Hg(Ⅱ) in cloud and fog water was highly dependent on pH. For conditions found in most clouds and fogs, the chloride ion was the most important major ion controlling Hg(Ⅱ) complexation, even under conditions of relatively low chloride content. However, Hg(OH)2(subscript (aq)), and HgClOH(subscript (aq)) were found to dominate over HgCl2 in locations with high pH due emissions of agricultural ammonia; i.e. San Joaquin and Sacramento Valleys, CA. At concentrations relevant to typical cloud and fog waters, carboxylic acids (e.g. formate and acetate) did not play a significant role in Hg(Ⅱ) speciation. Methyl mercury was speciated as MeHgCl in most locations, except for the locations with high pH, where MeHgOH dominated. These results provide constraints over potential reaction pathways that may transform oxidized Hg(Ⅱ) in clouds and fogs.

Climate impact on airborne particulate matter concentrations in California using seven year analysis periods

Abstract. The effect of global climate change on the annual average concentration of fine particulate matter (PM2.5) in California was studied using a climate-air quality modeling system composed of global through regional models. Output from the NCAR/DOE Parallel Climate Model (PCM) generated under the "business as usual" global emissions scenario was downscaled using the Weather Research and Forecasting (WRF) model followed by air quality simulations using the UCD/CIT airshed model. The system represents major atmospheric processes acting on gas and particle phase species including meteorological effects on emissions, advection, dispersion, chemical reaction rates, gas-particle conversion, and dry/wet deposition. The air quality simulations were carried out for the entire state of California with a resolution of 8-km for the years 2000–2006 (present climate with present emissions) and 2047–2053 (future climate with present emissions). Each of these 7-year analysis periods was analyzed using a total of 1008 simulated days to span a climatologically relevant time period with a practical computational burden. The 7-year windows were chosen to properly account for annual variability with the added benefit that the air quality predictions under the present climate could be compared to actual measurements. The climate-air quality modeling system successfully predicted the spatial pattern of present climate PM2.5 concentrations in California but the absolute magnitude of the annual average PM2.5 concentrations were under-predicted by ~4–39% in the major air basins. The majority of this under-prediction was caused by excess ventilation predicted by PCM-WRF that should be present to the same degree in the current and future time periods so that the net bias introduced into the comparison is minimized. Surface temperature, relative humidity (RH), rain rate, and wind speed were predicted to increase in the future climate while the ultra violet (UV) radiation was predicted to decrease in major urban areas in the San Joaquin Valley (SJV) and South Coast Air Basin (SoCAB). These changes lead to a predicted decrease in PM2.5 mass concentrations of ~0.3–0.7 μg m−3 in the southern portion of the SJV and ~0.3–1.1 μg m−3 along coastal regions of California including the heavily populated San Francisco Bay Area and the SoCAB surrounding Los Angeles. Annual average PM2.5 concentrations were predicted to increase at certain locations within the SJV and the Sacramento Valley (SV) due to the effects of climate change, but a corresponding analysis of the annual variability showed that these predictions are not statistically significant (i.e. the choice of a different 7-year period could produce a different outcome for these regions). Overall, virtually no region in California outside of coastal + central Los Angeles, and a small region around the port of Oakland in the San Francisco Bay Area experienced a statistically significant change in annual average PM2.5 concentrations due to the effects of climate change in the present~study. The present study employs the highest spatial resolution (8 km) and the longest analysis windows (7 years) of any climate-air quality analysis conducted for California to date, but the results still have some degree of uncertainty. Most significantly, GCM calculations have inherent uncertainty that is not fully represented in the current study since a single GCM was used as the starting point for all calculations. The PCM results used in the current study predicted greater wintertime increases in air temperature over the Pacific Ocean than over land, further motivating comparison to other GCM results. Ensembles of GCM results are usually employed to build confidence in climate calculations. The current results provide a first data-point for the climate-air quality analysis that simultaneously employ the fine spatial resolution and long time scales needed to capture the behavior of climate-PM2.5 interactions in California. Future downscaling studies should follow up with a full ensemble of GCMs as their starting point, and include aerosol feedback effects on local meteorology.

Population Structure and Relatedness among Female Northern Pintails in Three California Wintering Regions

Abstract. Female Northern Pintails (Anas acuta) were sampled in California's three main Central Valley wintering regions (Sacramento Valley, Suisun Marsh, San Joaquin Valley) during September–October before most regional movements occur and microsatellite and mitochondrial DNA were analyzed to examine population structure and relatedness. Despite reportedly high rates of early-fall pairing and regional fidelity, both sets of markers indicated that there was little overall genetic structuring by region. Pintails from Suisun Marsh did exhibit higher relatedness among individuals and capture groups than in the Sacramento or San Joaquin Valleys, likely reflecting a sample comprised of a greater proportion of local breeders. The lack of genetic structuring among regions indicates that a high degree of movement and interchange occurs among pintails wintering in the Central Valley. Thus, although maintaining the existing distribution of pintails among Central Valley regions is important for other reasons, it doe...

Annual carbon and nitrogen loadings for a furrow-irrigated field

Evaluations of agricultural management practices for soil C sequestration have largely focused on practices, such as reduced tillage or compost/manure applications, that minimize soil respiration and/or maximize C input, thereby enhancing soil C stabilization. Other management practices that impact carbon cycling in agricultural systems, such as irrigation, are much less understood. As part of a larger C sequestration project that focused on potential of C sequestration for standard and minimum tillage systems of irrigated crops, the effects of furrow irrigation on the field C and N loading were evaluated. Experiments were conducted on a laser-leveled 30 ha grower's field in the Sacramento valley near Winters, CA. For the 2005 calendar year, water inflow and runoff was measured for all rainfall and irrigation events. Samples were analyzed for C and N associated with both sediment and dissolved fractions. Total C and N loads in the sediment were always higher in the incoming irrigation water than field runoff. Winter storms moved little sediment, but removed substantial amounts of dissolved organic carbon (DOC), or about one-third of the total C balance. Despite high DOC loads in runoff, the large volumes of applied irrigation water with sediment and DOC resulted in a net increase in total C for most irrigation events. The combined net C input and N loss to the field, as computed from the field water balance, was 30.8 kg C ha −1 yr −1 and 5.4 kg N ha −1 yr −1 for the 2005 calendar year. It is concluded that transport of C and N by irrigation and runoff water should be considered when estimating the annual C field balance and sequestration potential of irrigated agro-ecosystems.