Andrew Bruce Gray

University of California, Riverside | UCR · Department of Environmental Sciences

This article provides a commentary about the state of integrated, coordinated, open, and networked (ICON) principles in Earth and Planetary Surface Processes and discussion on the opportunities and challenges of adopting them. This commentary focuses on the challenges with current inclusive, equitable, and accessible science and highlights how rese...

Despite global efforts to monitor, mitigate against, and prevent trash (mismanaged solid waste) pollution, no harmonized trash typology system has been widely adopted worldwide. This impedes the merging of datasets and comparative analyses. We addressed this problem by 1) assessing the state of trash typology and comparability, 2) developing a stan...

Region Ventura River watershed, California, USA Focus After wildfire, small mountainous watersheds can produce dramatic increases in fluvial sediment transport, but these changes are often evaluated under the assumption of stationary pre-fire sediment dynamics. The objectives of this study were to investigate temporal dependence in the fine (silt...

Although the study of microplastics in the aquatic environment incorporates a diversity of research fields, it is still in its infancy in many aspects while comparable topics have been studied in other disciplines for decades. In particular, extensive research in sedimentology can provide valuable insights to guide future microplastics research. To...

As coastal ecosystems become widely recognized for their capacity to sequester carbon (blue carbon), standard accounting methodologies for the generation of carbon credits are being developed. To ensure the applicability of these standards across blue carbon ecosystems, we investigated organic carbon provenance and burial in salt marshes and seagra...

Urban areas are the primary source of human-made litter globally, and roadsides are a primary accumulation location. This study aimed to investigate how litter arrives at roadsides and determine the accumulation rate and composition of roadside litter. We monitored select roadsides in the Inland Empire, California, for litter abundance (count) and...

Urban areas are the primary source of human-made litter to the global environment, and roadsides are a primary accumulation location in urban areas. The goal of this study was to investigate how litter arrives at roadsides and what can be done to prevent it. We monitored roadsides in the Inland Empire, California for litter abundance (count) and co...

Seagrass meadows are globally important habitats, protecting shorelines, providing nursery areas for fish, and sequestering carbon. However, both anthropogenic and natural environmental stressors have led to a worldwide reduction seagrass habitats. For purposes of management and restoration, it is essential to produce accurate maps of seagrass mead...

Microplastic pollution research has suffered from inadequate data and tools for spectral (Raman and infrared) classification. Spectral matching tools often are not accurate for microplastics identification and are cost-prohibitive. Lack of accuracy stems from the diversity of microplastic pollutants, which are not represented in spectral libraries....

River flow is a major conveyance of microplastic (1−5000 μm) pollution from land to marine systems. However, the current approaches to monitoring and modeling fluvial transport of microplastic pollution have primarily relied on sampling the surface of flow and assumptions about microplastic concentration depth profiles to estimate the depth-average...

The spatial analysis of biota, particulate organic matter, and sediments for stable isotopes of carbon (δ 13 C), nitrogen (δ 15 N), and sulfur (δ 34 S) have proved useful for identifying patterns in productivity, nutrient pollution, and relationships between biological and physiochemical variables at the local and global scales. Yet such approaches...

Postfire debris flows are particularly complex to study because they do not form discrete initiation locations and commonly involve multiple simultaneously operating erosional processes. Although recent work has begun to elucidate a more mechanistic understanding of postfire debris flows, there is still a paucity of detailed sediment budgets charac...

Microplastic is exposed to numerous weathering processes in the environment, which change particle properties and thus influence transport behaviors, including settling and rising velocities in aquatic environments. However, the extent to which particles in the environment differ from virgin particles in their transport behaviors has not yet been i...

Microplastic research is a rapidly developing field, with urgent needs for high throughput and automated analysis techniques. We conducted a review covering image analysis from optical microscopy, scanning electron microscopy, fluorescence microscopy, and spectral analysis from Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, py...

The ubiquitous pollution of the environment with microplastics, a diverse suite of contaminants, is of growing concern for science and currently receives considerable public, political, and academic attention. The potential impact of microplastics in the environment has prompted a great deal of research in recent years. Many diverse methods have be...

Coastal cities in tropical areas are often low-lying and vulnerable to the effects of flooding and storms. San Juan, Puerto Rico, is a good example of this. It is built around a lagoon-channel complex called the San Juan Bay Estuary (SJBE). A critical channel in the estuary, the Caño Martín Peña, has filled in and now frequently floods the surround...

Tropical urban estuaries are severely understudied. Little is known about the basic biogeochemical cycles and dominant ecosystem processes in these waterbodies, which are often low-lying and heavily modified. The San Juan Bay Estuary (SJBE) in San Juan, Puerto Rico is an example of such a system. Over the past 80 years, a portion of the estuary has...

This paper demonstrates CleanUpOurWorld; a research spatial database that is designed and deployed to collect, process, query, and visualize anthropogenic litter data. Such data has a significant importance in the field of environmental sciences due to its important use cases. We make a major on-going effort to collect and maintain such data worldw...

Diverse studies predict global expansion of Oxygen Minimum Zones (OMZs) as a consequence of anthropogenic global warming. While the observed dissolved oxygen concentrations in many coastal regions are slowly decreasing, sediment core paleorecords often show contradictory trends. This is the case for numerous high-resolution reconstructions of oxyge...

Wastewater effluent is a prevalent source of contaminants of emerging concern in aquatic environments, including plastic pollution. A wide range of monitoring and analytical techniques to assess the contribution of wastewater derived microplastic pollution have been employed over the past two decades. The goal of this report is to critically evalua...

Diatoms have been successfully used as indicators of past and present environmental conditions in freshwater and marine habitats, but their diversity and indicative properties in microtidal coastal wetlands of temperate zone are relatively poorly studied. The goal of this study was to determine whether diatoms can be used as indicators of sea level...

Small mountainous coastal watersheds are thought to be responsible for transporting disproportionately large volumes of sediment to the global ocean. In comparison with low-relief passive margin rivers, their geologic setting is associated with high rates of sediment production, high peak flows due to uniformity in runoff lag-times, and limited flo...

Fluvial suspended sediment concentration and discharge is most commonly estimated by applying rating curves developed over a given base period of sediment monitoring to longer, continuous records of water discharge. This practice invokes the tacit assumption of stationary suspended sediment concentration–water discharge relationships (i.e. suspende...

Fluvial sediment deposits can provide useful records of integrated watershed expressions including flood event magnitudes. However, floodplain and estuarine sediment deposits evolve through the interaction of watershed/marine sediment supply and transport characteristics with the local depositional environment. Thus extraction of watershed scale si...

This study is an investigation into the roles of wildfire and changing agricultural practices in controlling the inter-decadal scale trends of suspended sediment production from semi-arid mountainous rivers. In the test case, a decreasing trend in suspended sediment concentrations was found in the lower Salinas River, California between 1967 and 20...

This study proposes a modification of the current model for abandoned channel fill stratigraphy produced in unidirectional flow river reaches to incorporate seasonal tidal deposition. Evidence supporting this concept came from a study of two consecutive channel abandonment sequences in Ropers Slough of the lower Eel River Estuary in northern Califo...

Rivers display temporal dependence in suspended sediment – water discharge relationships. Although most work has focused on multi-decadal trends, river sediment behavior often displays sub-decadal scale fluctuations that have received little attention. The objectives of this study were to identify interannual to decadal scale fluctuations in the su...

Recent studies of estuarine sediment deposits have focused on grain size spectra as a tool to better understand depositional processes, in particular those associated with tidal inlet and basin dynamics. The key to accurate interpretation of lithostratigraphic sequences is establishing clear connections between morphodynamic changes and the resulti...

The occurrence of two wildfires separated by 31 yr in the chaparral-dominated Arroyo Seco watershed (293 km(2)) of California provides a unique opportunity to evaluate the effects of wildfire on suspended-sediment yield. Here, we compile discharge and suspended-sediment sampling data from before and after the fires and show that the effects of the...

The delivery of particulate organic carbon (POC) from rivers to marine sediments is the major long-term sink of CO2 on Earth and a net source of oxygen over millennial time scales. Small mountainous river systems (SMRS) may be responsible for half of the POC delivery to global oceans. The flux of POC in SMRS has been thought to be regulated by hydr...

The delivery of particulate organic carbon (POC) from rivers to marine sediments is the major long-term sink of CO2 on Earth and a net source of oxygen over millennial time scales. Small mountainous river systems may be responsible for half of the POC delivery to global oceans. The flux of POC in SMRS has been thought to be regulated by hydro-geomo...

Estuarine restoration is a major focus of coastal management. To set estuarine restoration targets, coastal managers need to understand natural baselines and human modifications. The goal of this study was to characterize baseline environmental conditions for the purposes of restoration planning at Elkhorn Slough, a regionally significant Californi...

Wildfire can dramatically alter the physical and geochemical conditions of the landscape and modify rates of runoff and erosion. The occurrence of two large wildfires in the Arroyo Seco watershed (293 km2) of California along with water and sediment sampling before and after both fires provides a unique opportunity to evaluate the watershed-scale e...

Fire causes major changes to organic carbon, converting biological organic materials to pyrogenic-derived organic carbon (Py-OC), including black carbon. Wildfire also dramatically affects hydrological and erosion processes within watersheds, potentially increasing the erosion and discharge of Py-OC as particulate organic carbon (POC). We hypothesi...

Pretreatment of sediment with hydrogen peroxide to remove organic constituents and aid deflocculation is a common component of particle size analyses of terrestrial and marine sediments. This study quantitatively determined the effect of a range of treatment levels on particle size distribution among four sediment types representing a range of mine...

The discharge of particulate organic carbon (POC) from small mountainous rivers may contribute nearly half of the world's POC to the ocean. However, these smaller rivers have highly variable discharges throughout the year, which in turn affect the content and composition of POC being delivered to coastal margins. Further, POC composition has been s...

Small mountainous rivers display highly variable discharges on both seasonal and event scales. Previous work has shown marked differences in the composition of the particulate load of rivers collected at different stages of the hydrograph, but fewer studies have specifically investigated how the biogeochemical compositions of particulate organic ma...

Erosion rates in mountainous watersheds have increased during historic times due to land use changes such as logging, mining, road construction, agriculture, and urban/suburban development. This increase in erosion rates has resulted in (1) increased sediment accumulation in small and/or closed catchments, (2) rapid sediment infilling in reservoirs...