Carol Kendall

Carol Kendall
United States Geological Survey | USGS · California Water Science Center

About

265
Publications
37,232
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
23,149
Citations

Publications

Publications (265)
Article
River deltas and their diverse array of aquatic environments are increasingly impacted by anthropogenic inputs of nitrogen (N). These inputs can alter the N biogeochemistry of these systems and promote undesirable phenomena including harmful algae blooms and invasive aquatic macrophytes. To examine N sources and biogeochemical processes in the Sacr...
Article
Full-text available
Estuaries worldwide are undergoing changes to patterns of aquatic productivity because of human activities that alter flow, impact sediment delivery and thus the light field, and contribute nutrients and contaminants like pesticides and metals. These changes can influence phytoplankton communities, which in turn can alter estuarine food webs. We us...
Article
Little is known about the regional extent and variability of nitrate from atmospheric deposition that is transported to streams without biological processing in forests. We measured water chemistry and isotopic tracers of nitrate sources across the Northern Forest Region of the USA and Canada and reanalyzed data from other studies to determine when...
Data
This data publication includes water chemistry, nitrate isotopic values (δ15N and δ18O), apportioned amounts of unprocessed atmospheric nitrate in freshwaters, streamflow, streamflow apportioned into quick flow, and associated metadata. Data were collected from forested or predominantly forested catchments in the United States and Canada. Some samp...
Article
Full-text available
Anthropogenic alteration of the form and concentration of nitrogen (N) in aquatic ecosystems is widespread. Understanding availability and uptake of different N sources at the base of aquatic food webs is critical to establishment of effective nutrient management programs. Stable isotopes of N (¹⁴N, ¹⁵N) are often used to trace the sources of N fue...
Article
Full-text available
Anthropogenic alteration of the form and concentration of nitrogen (N) in aquatic ecosystems is widespread. Understanding availability and uptake of different N sources at the base of aquatic food webs is critical to establishment of effective nutrient management programs. Stable isotopes of N (¹⁴N, ¹⁵N) are often used to trace the sources of N fue...
Article
Full-text available
Phytoplankton are critical component of the food web in most large rivers and estuaries, and thus identifying dominant controls on phytoplankton abundance and species composition is important to scientists, managers, and policymakers. Recent studies from a variety of systems indicate that ammonium ( ) in treated wastewater effluent decreases primar...
Article
Stable isotopes present in water (δ2H, δ18O) have been used extensively to evaluate hydrological processes such as evaporation, precipitation, mixing and residence time. In estuarine aquatic habitats, residence time (τ) is a major driver of biogeochemical processes, affecting trophic subsidies and conditions in fish-spawning habitats. But τ is high...
Article
Full-text available
Groundwater quality is a concern in alluvial aquifers that underlie agricultural areas, such as in the San Joaquin Valley of California. Shallow domestic wells (less than 150 m deep) in agricultural areas are often contaminated by nitrate. Agricultural and rural nitrate sources include dairy manure, synthetic fertilizers, and septic waste. Knowledg...
Article
Sulfur, a nutrient required by terrestrial ecosystems, is likely to be regulated by atmospheric processes in well-drained, upland settings because of its low concentration in most bedrock and generally poor retention by inorganic reactions within soils. Environmental controls on sulfur sources in unpolluted ecosystems have seldom been investigated...
Chapter
This chapter introduces the fundamentals of environmental isotope tracers in hydrologic studies, provides an overview of the most common applications of light isotopes for understanding the hydrologic cycle and tracing solutes in aquatic systems, and summarizes recent advances in these fields. Isotope tracers have been extremely useful in providing...
Article
Laser spectroscopy for analysis of stable isotopes is a rapidly emerging technology with the potential to enable new scientific investigations in hydrology and biogeochemistry. The two basic advantages of laser spectroscopy over mass spectrometry—lower instrument cost and ease of use—mean more laboratories can obtain the capability. Portability of...
Article
Autumn is a season of dynamic change in forest streams of the northeastern USA due to effects of leaf fall on both hydrology and biogeochemistry. Few studies have explored how interactions of biogeochemical transformations, various nitrogen sources, and catchment flowpaths affect stream nitrogen variation during autumn. To provide more information...
Article
A suite of particulate and dissolved organic and inorganic stable isotopes were needed to determine the source of the nutrients and cells that initiate and sustain the toxic cyanobacteria bloom of Microcystis in San Francisco Estuary. Particulate and dissolved inorganic and organic matter in water and plankton samples were collected biweekly during...
Article
Increasingly, hydrologic studies require information on the isotopic composition of natural waters. This report presents stable hydrogen (delta2H) and oxygen isotope ratios (delta18O) from 391 selected sites of the U.S. Geological Survey's National Stream Quality Accounting Network (NASQAN) and BENCHMARK surface water networks collected during the...
Conference Paper
Full-text available
Background/Question/Methods Agricultural production in arid regions results in large-scale modifications of landscape and hydrology, causing disruption of natural ecosystem function. Drainage from irrigated agriculture results in nutrient enrichment and the eutrophication of impacted rivers. In the Central Valley of California, the most productiv...
Article
Full-text available
Reservoirs are critical components of many water supply systems as they allow the storage of water when supply exceeds demand. However, during water storage biogeochemical processes can alter both the amount and composition of dissolved organic matter (DOM), which can in turn affect water quality. While the balance between production and loss deter...
Article
Full-text available
Nitrate concentrations above the 10 mg/L NO3-N maximum contaminant level (MCL) have been found in many wells throughout the Central Valley, California. This area contains many possible anthropogenic nitrate sources including current and historic agriculture, private septic systems, municipal waste water, and confined animal feeding operations (prim...
Article
The USGS Isotope Tracers Project uses stable isotopes and tritium to add a unique dimension of chemical information to a wide range of environmental investigations. The use and application of isotopes is usually an unfamiliar and even esoteric topic to the general public. Therefore during three USGS open house events, as a public outreach effort, w...
Article
Full-text available
Within reservoirs, production, transformation, and loss of dissolved organic matter (DOM) occur simultaneously. While the balance between production and loss determines whether a reservoir is a net sink or source of DOM, changes in chemical composition are also important because they affect DOM reactivity with respect to disinfection by-product (DB...
Article
Nonpoint source nitrogen (N) pollution is a leading contributor to U.S. water quality impairments. We combined watershed N mass balances and stable isotopes to investigate fate and transport of nonpoint N in forest, agricultural, and urbanized watersheds at the Baltimore Long-Term Ecological Research site. Annual N retention was 55%, 68%, and 82% f...
Article
Recently, methods have been developed to analyze NO3- for δ15N and δ18O, improving our ability to identify NO3- sources and transformations. However, none of the existing methods are suited for waters with low NO3- concentrations (0.7-10 µM). We describe an improved method for collecting and recovering NO3- on exchange columns. To overcome the leng...
Article
To investigate the mechanism for diel (24 h) changes commonly observed at fixed sampling locations and how these diel changes relate to downstream transport in hypereutrophic surface waters, we studied a parcel of agricultural drainage water as it traveled for 84 h in a concrete-lined channel having no additional water inputs or outputs. Algal fluo...
Article
The Sacramento and San Joaquin Rivers are the main rivers draining the northern and southern parts of California's Central Valley. Both watersheds are underlain by similar sediments, are dominated by similar agricultural and urban land uses, and water supplies are highly regulated in both rivers. While agricultural land uses are major sources of nu...
Article
Isotopes are a potentially powerful component of monitoring and assessment programs aimed at quantifying and mitigating alterations to environments from human activities. Locations exhibiting unusually high rates of biogeochemical cycling or elevated pollution levels usually have distinctive isotopic compositions that are suggestive or diagnostic o...
Article
In order to better understand the factors controlling nitrogen sources and cycling within Suisun Bay and the Sacramento-San Joaquin River confluence, stable isotope measurements of nitrate (NO3), water, and particulate organic matter (POM) were combined with estimates of volumetric water source contributions calculated using the DSM2-HYDRO hydrodyn...
Article
Nonpoint source nitrogen (N) pollution is a leading contributor of water quality impairments including coastal eutrophication and hypoxia. Improved identification of nonpoint N sources will be critical in prioritizing strategies for watershed N reductions. We combined long-term monitoring, watershed mass balances, and stable isotope source identifi...
Article
Ammonium input from Sacramento Regional Wastewater Treatment Plant (SRWTP) is of concern because of its potential to alter the aquatic food chain by favoring a different mix of aquatic primary producers and/or by reducing phytoplankton abundance through inhibition of nitrate assimilation. Samples were collected from 23 sites along a transect from t...
Article
Climate change is expected to dramatically alter the timing and quantity of water within the nation’s river systems. These changes are driven by variation in the form, location and amount of precipitation that will affect the temporal and spatial distribution of river source water over time. To manage the impact of climate change, we will need to u...
Chapter
Full-text available
Isotopes are a potentially powerful component of monitoring and assessment programs aimed at quantifying and mitigating alterations to environments from human activities. In particular, isotopic techniques have proved useful for tracing sources and sinks of various pollutants in large river basins, wetlands, and airsheds. Many of these studies have...
Article
Transformations of phosphate (Pi) in different soil fractions were tracked using the stable isotopic composition of oxygen in phosphate (δ18Op) and Pi concentrations. Clay soil from Israel was treated with either reclaimed waste water (secondary, low grade) or with fresh water amended with a chemical fertilizer of a known isotopic signature. Change...
Conference Paper
Background/Question/Methods Increased delivery of nitrogen due to land-use change has contributed to increased coastal eutrophication. Improved knowledge of nonpoint sources and transformations of nitrogen will be critical in managing the nitrogen cycle in response to interactive land-use and climate change. We investigated effects of land use, hy...
Article
As a part of the Chuzhou hydrological experimental system, the No.1 experimental catchment, Nandadish, with drainage area of 7897 m2 sits on the andesite bedrock with Quaternary deposit of 2.46 m in average. Various runoff components, surface runoff and subsurface runoff including interflow from unsaturated zone, groundwater flow from saturated zon...
Article
The nitrogen (N) and oxygen (O) isotopic composition (δ15N and δ18O) of water soluble aerosol nitrate was measured in aerosol samples collected in Eilat, Israel, from August 2003 to November 2004. During this period δ15N values ranged from − 6.9‰ to + 1.9‰ and δ18O from + 65.1‰ to + 84.9‰ and exhibited strong seasonal variability with higher averag...
Article
Full-text available
1] Dry deposition is a major component of total atmospheric nitrogen deposition and thus an important source of bioavailable nitrogen to ecosystems. However, relative to wet deposition, less is known regarding the sources and spatial variability of dry deposition. This is in part due to difficulty in measuring dry deposition and associated depositi...
Article
Full-text available
Three sediment cores were collected off the Mississippi River delta on the Louisiana Shelf at sites that are variably influenced by recurring, summer-time water-column hypoxia and fluvial loadings. The cores, with established chronology, were analyzed for their respective carbon, nitrogen, and sulfur elemental and isotopic composition to examine va...
Conference Paper
Sampling at appropriate time scales that will capture relevant processes is a critical component of large scale environmental studies. When sampling over large areas and/or over long time periods it is usually not possible to sample each site at the same point in the diel or tidal cycle. Therefore, it is necessary to understand short term fluctuati...
Article
Stable isotope analysis of carbon, nitrogen, and sulfur has been used successfully for source identification in numerous studies, but P has only one stable isotope, making this direct approach impossible. However, P in nature is strongly bound to oxygen, and oxygen has three stable isotopes. Advances in stable isotope mass spectrometry, dissolved i...
Article
Full-text available
Variations in nitrogen (N) deposition sources to high-elevation ecosystems in the Rocky Mountains were evaluated using spatially and temporally distributed N isotope data for water years 1995-2006. This unique dataset links N in wet deposition and snowpack to source emissions, and enhances understanding of the impacts of anthropogenic activities an...
Article
In California's Central Valley, nitrate contamination of drinking water wells is a significant concern, and there are multiple potential sources of nitrate in this area including septic discharge, synthetic and manure fertilizers, and concentrated animal feeding operations. Dairies represent the majority of animal feeding operations in California,...
Article
One of the potential causes of declines in several species of fish in the San Francisco Bay Estuary ecosystem is NH4-inhibition of algal productivity in the Delta and Suisun Bay, which is hypothesized to cause pelagic organism decline via cascading trophic interactions. Hence, there is considerable interest in determining the relative contributions...
Article
Full-text available
The major ion chemistry of water from an 11.42-km reach of the Pajaro River, a losing stream in central coastal California, shows a consistent pattern of higher concentrations during the 2nd (dry) half of the water year. Most solutes are conserved during flow along the reach, but [NO3−] decreases by ~30% and is accompanied by net loss of channel di...
Article
The oxygen isotopic composition of dissolved inorganic phosphate (delta18Op) in many aquatic ecosystems is not in isotopic equilibrium with ambient water and, therefore, may reflect the source delta18Op. Identification of phosphate sources to water bodies is critical for designing best management practices for phosphate load reduction to control eu...
Article
Water samples collected during three sampling trips to Lake Erie displayed oxygen isotopic values of dissolved phosphate (delta18Op) that were largely out of equilibrium with ambient conditions, indicating that source signatures may be discerned. delta18Op, values in the Lake ranged from +10% per hundred to +17% per hundred, whereas the equilibrium...
Article
Full-text available
Knowledge of key sources and biogeochemical processes that affect the transport of nitrate (NO(3)(-)) in streams can inform watershed management strategies for controlling downstream eutrophication. We applied dual isotope analysis of NO(3)(-) to determine the dominant sources and processes that affect NO(3)(-) concentrations in six stream/river wa...
Conference Paper
Excess nitrogen cascades through terrestrial biogeochemical cycles and affects stream nitrate concentrations in upland forests where atmospheric deposition is an important source of anthropogenic nitrogen. We will discuss approaches including high-frequency sampling, isotopic tracers, and end-member mixing analysis that can be used to decipher the...
Conference Paper
There is a need to understand the coupled biogeochemical and hydrological processes that control stream hydrochemistry in upland forested catchments. At watershed 9 (W-9) of the Sleepers River Research Watershed in the northeastern USA, we use high-frequency sampling, environmental tracers, end-member mixing analysis, and stream reach mass balances...
Article
Full-text available
Sugar cane cropping for biofuel production reduces water discharge from a northern Indian basin and threatens downstream communities. Regulators want to partition blame between climate change-induced declines in mountain snowpack and excessive evaporation from poorly managed fields. In the same basin, a tiger is found shot. Is it the nuisance anima...
Article
Full-text available
Nitrate (NO3 -) concentrations and dual isotopic composition (delta 15N and delta 18O) were measured during various seasons and tidal conditions in Elkhorn Slough to evaluate mixing of sources of NO3 - within this California estuary. We found the isotopic composition of NO3 - was influenced most heavily by mixing of two primary sources with unique...
Article
Full-text available
1. We investigated diurnal nitrate (NO3−) concentration variability in the San Joaquin River using an in situ optical NO3− sensor and discrete sampling during a 5-day summer period characterized by high algal productivity. Dual NO3− isotopes (δ15NNO3 and δ18ONO3) and dissolved oxygen isotopes (δ18ODO) were measured over 2 days to assess NO3− source...
Article
Full-text available
In the United States, environmentally impaired rivers are subject to regulation under total maximum daily load (TMDL) regulations that specify watershed wide water quality standards. In California, the setting of TMDL standards is accompanied by the development of scientific and management plans directed at achieving specific water quality objectiv...
Article
1] We explored catchment processes that control stream nutrient concentrations at an upland forest in northeastern Vermont, USA, where inputs of nitrogen via atmospheric deposition are among the highest in the nation and affect ecosystem functioning. We traced sources of water, nitrate, and dissolved organic matter (DOM) using stream water samples...
Conference Paper
The San Joaquin River (SJR) is a large hypereutrophic river located in the Central Valley, California, a major agricultural region. Nutrient subsidies, algae, and other organic material from the San Joaquin River contribute to periods of low dissolved oxygen in the Stockton Deep Water Ship Channel, inhibiting salmon migration. We used a multi-isoto...
Article
Episodic conditions of low dissolved oxygen (DO) occurring in the San Joaquin River deep water shipping channel (DWSC) at Stockton, California inhibit salmon migration during late summer and early fall. As part of a CALFED study to determine the sources of organic matter and nutrients related to the low DO problem, four diel studies were undertaken...
Conference Paper
The d15N of algae in nitrate-rich rivers is often about 4 to 5 permil lower than the d15N of the nitrate used by the algae. In cases where the algal productivity significantly depletes the available nitrate pool, the uptake of nitrate can cause significant increases in the d15N and d18O of the residual nitrate, resulting in isotope values similar t...
Article
In order to better understand sources of dissolved organic matter (DOM) in streams from the small to large watershed scales, we initiated a one-year investigation of the chemical and isotopic characteristics of DOM at the HJ Andrews Experimental Forest (HJA) in Blue River, OR. DOM is a biologically significant loss from these watersheds, but its so...
Conference Paper
The San Joaquin River is a eutrophic, heavily impacted river which drains extensive agricultural areas and receives waste water discharge from rapidly growing urban areas. The Delta-San Francisco Bay region is hydrodynamically complex, drains a watershed covering approximately 40% of the area of California, and is considered to be one of the most a...
Article
This study assesses how rivers, wetlands, island drains and open water habitats within the Sacramento–San Joaquin River Delta affect dissolved organic matter (DOM) content and composition, and disinfection byproduct (DBP) formation. Eleven sites representative of these habitats were sampled on six dates to encompass seasonal variability. Using a su...
Article
In the Rocky Mountains, there is uncertainty about the source areas and emission types that contribute to nitrate (NO3) deposition, which can adversely affect sensitive aquatic habitats of high-elevation watersheds. Regional patterns in NO3 deposition sources were evaluated using NO3 isotopes in five National Parks, including 37 lakes and 7 precipi...
Article
The stable isotopic composition of dissolved inorganic carbon (δ13C-DIC) was investigated as a potential tracer of streamflow generation processes at the Sleepers River Research Watershed, Vermont, USA. Downstream sampling showed δ13C-DIC increased between 3–5‰ from the stream source to the outlet weir approximately 0·5 km downstream, concomitant w...