Yuzhou Luo

University of California, Davis | UCD · Department of Land, Air and Water Resources

Due to the coarse spatial resolution, the column‐averaged dry‐air mole fraction of CO2 (XCO2) data from the CarbonTracker may be inadequate to reflect the spatial heterogeneity of XCO2. We developed a machine learning model to fill the data gaps in the Orbiting Carbon Observatory 2 satellite retrievals across China during 2015–2018, with cross‐vali...

Until recently, Northern China was one of the most SO2 polluted regions in the world. The lack of long-term and spatially resolved surface SO2 data hinders retrospective evaluation of relevant environmental policies and human health effects. This study aims to derive the spatiotemporal distribution of surface SO2 across Northern China during 2005–2...

Background: Long-term surface NO2 data are essential for retrospective policy evaluation and chronic human exposure assessment. In the absence of NO2 observations for Mainland China before 2013, training a model with 2013-2018 data to make predictions for 2005-2012 (back-extrapolation) could cause substantial estimation bias due to concept drift....

Pesticides and degradates are ubiquitously detected in municipal wastewater influent in the United States. However, little detailed information exists on their sources. The aim of this study is to investigate California Pesticide Use Report (PUR) and sales data to identify pesticide uses with a high potential for indoor down-the-drain (DtD) transpo...

The management of pesticides to parotect water quality remains a significant global challenge. Historically, despite regulatory frameworks intended to prevent, minimize, and manage off-site movement of pesticides, multiple generations of pesticide active ingredients have created a seemingly unending cycle of pesticide water pollution in both agricu...

Given its relatively long lifetime in the troposphere, carbon monoxide (CO) is commonly employed as a tracer for characterizing airborne pollutant distributions. The present study aims to estimate the spatiotemporal distributions of ground-level CO concentrations across China during 2013–2016. We refined the random-forest–spatiotemporal kriging (RF...

A gradient boosting machine (GBM) was developed to model the susceptibility of debris flow in Sichuan, Southwest China for risk management. A total of 3839 events of debris flow during 1949–2017 were compiled from the Sichuan Geo-Environment Monitoring program, field surveys, and satellite imagery interpretation. In the cross-validation, the GBM sh...

A novel algorithm named the stepwise genetic algorithm (SGA) is proposed to optimize the air quality monitoring network of mainland China under the framework of adaptive management. SGA is adapted from the genetic algorithm by modifying the operators of “mutation” and “crossover” to increase the number of removed sites by one at each step. Approxim...

Given its relatively long lifetime in the troposphere, carbon monoxide (CO) is commonly employed as a tracer for characterizing airborne pollutant distributions. The present study aims to estimate the spatiotemporal distributions of ground-level CO concentrations across China during 2013–2016. A refined random-forest-spatiotemporal-kriging model (R...

Thiobencarb is a commonly used herbicide in Northern California rice fields. Released paddy water containing thiobencarb may pose ecological risks to non-targeted organisms. In this research, the Rice Water Quality Model (RICEWQ) is equilibrium tested and then calibrated using monitoring data at field level. Then it is employed to assess the enviro...

Pesticide residue runoff to surface water is of great concern to local stakeholders who seek to preserve or achieve good water quality. The Soil & Water Assessment Tool (SWAT) has been widely used to assess many environmental problems related to water resources and nonpoint-source pollution, including sediment and nutrient loads and pesticides. How...

For the aquatic exposure assessment of pesticides, the USEPA uses the Variable Volume Water Model (VVWM) to predict the estimated environmental concentrations (EECs) of a pesticide in a water body that receives runoff inputs from the Pesticide Root Zone Model (PRZM). The standard farm pond and additional generalized static and flowing water bodies...

Satellite-retrieved aerosol optical depth (AOD) is commonly used to estimate ambient levels of fine particulate matter (PM2.5), though it is important to mitigate the estimation bias of PM2.5 due to gaps in satellite-retrieved AOD. A nonparametric approach with two random-forest submodels is proposed to estimate PM2.5 levels by filling gaps in sate...

Pesticide application in rice fields is essential to alleviate pest stress and improve annual yield. However, water quality deterioration and other ecological problems may result from pesticide usage. Modeling is deemed a powerful method to understand the fate and transport of agrochemicals. However, many models fail to reflect the uniqueness of th...

The Surface Water Prioritization (SWMP) model was developed to prioritize pesticides and geographic locations for surface water monitoring in agricultural and urban areas of California. SWMP incorporates California’s Pesticide Use Reporting (PUR) database for calculation of pesticide use amounts, and their accumulation and dissipation at watershed...

A novel model named random-forest-spatiotemporal-kriging (RF-STK) was developed to estimate the daily ambient NO2 concentrations across China during 2013-2016 based on the satellite retrievals and geographic covariates. The RF-STK model showed good prediction performance, with cross-validation R2=0.62 (RMSE=13.3 µg/m3) for daily and R2=0.73 (RMSE=6...

In China, ozone pollution shows an increasing trend and becomes the primary air pollutant in warm seasons. Leveraging the air quality monitoring network, a random forest model is developed to predict the daily maximum 8-h average ozone concentrations ([O3]MDA8) across China in 2015 for human exposure assessment. This model captures the observed spa...

Pesticides move to surface water via various pathways including surface runoff, spray drift and subsurface flow. Little is known about the relative contributions of surface runoff and spray drift in agricultural watersheds. This study develops a modeling framework to address the contribution of spray drift to the total loadings of pesticides in rec...

Quantifying pesticide loading into the Sacramento-San Joaquin Delta of northern California is critical for water quality management in the region, and potentially useful for biological weed control planning. In this study, the Soil and Water Assessment Tool (SWAT) was applied to model streamflow, sediment, and pesticide diuron loading in the San Jo...

A high degree of uncertainty associated with the emission inventory for China tends to degrade the performance of chemical transport models in predicting PM2.5 concentrations especially on a daily basis. In this study a novel machine learning algorithm, Geographically-Weighted Gradient Boosting Machine (GW-GBM), was developed by improving GBM throu...

Pesticides are commonly applied around residential homes, but their occurrence on exterior surfaces (e.g., pavement) has not been thoroughly evaluated. We collected 360 dust samples from curbside gutters, sidewalks and street surfaces at 40 houses in southern California to evaluate pesticide occurrence on urban paved surfaces, as well as their spat...

A georeferenced multimedia model was developed for evaluating the emissions and environmental fate of di-2-ethylhexyl phthalate (DEHP) in the Yangtze River Delta (YRD), China. Due to the lack of emission inventories, the emission rates were estimated by using the observed concentrations in soil as inputs for the multimedia model solved analytically...

Background: Pesticides are routinely applied to residential impervious outdoor surfaces for structural pest control. This residential usage has been linked to the occurrence of toxic levels of pesticides in urban water bodies. It is believed that runoff water transports particles that have sorbed hydrophobic pesticides. However, concentrations of...

In this study, we investigate the concurrent drought probability between the water source and destination regions of the central route of China's South to North Water Diversion Project. We find that both regions have been drying from 1960 to 2013. The estimated return period of concurrent drought events in both regions is 11 years. However, since 1...

The objective of this study was to develop, verify, and validate a new GIS-based model for simulating the fate and transport of rice pesticides in river basins. A plot scale model simulating pesticide fate and transport in rice paddies (PCPF-1) was incorporated into the Soil and Water Assessment Tool (SWAT) basin scale water and pollutant transport...

We tested a methodology for aggregating soil properties across multiple soil survey areas according to soil taxonomic information available within the Soil Survey Geographic (SSURGO) dataset. Most hydrologic modeling studies using SSURGO assume that soil property data are adequately grouped into a “soil type” that is represented by a map unit k...

Data analysis and characterization of precipitation in the Haihe River Basin (HRB) of China are required for management practices for the purpose of flood water control and utilization. In the companion paper, we presented precipitation data in the HRB during 1951–2010 and reported its basic statistics such as temporal trend and spatial variability...

Quantitative assessment of development sustainability could be a challenge to regional management and planning, especially for areas facing great risks of water shortage. Surface-water decline and groundwater over-pumping have caused serious environmental problems and limited economic development in many regions all around the world. In this paper,...

Pesticide uses on impervious surfaces and subsequent offsite transport significantly contribute to pesticide detection and aquatic toxicity in urban watersheds. This review evaluates the various methods that currently exist to model pesticide washoff from impervious surfaces. Empirical equations successfully describe pesticide washoff by calibratio...

Pesticide runoff from impervious surfaces is a significant cause of aquatic contamination and ecologic toxicity in urban waterways. Effective mitigation requires better understanding and prediction of off-site transport processes. Presented here is a comprehensive study on pesticide washoff from concrete surfaces, including washoff tests, experimen...

The Haihe River Basin (HRB), located in northern China with a drainage area of 318,200 km2, is one of the most developed regions in China. With rapid population growth and economic development, the combined problems of water shortage and groundwater over-pumping significantly constrain the sustainable development in this area. In order to strengthe...

Bracketing the uncertainty of streamflow and agricultural runoff under climate change is critical for proper future water resource management in agricultural watersheds. This study used the Soil and Water Assessment Tool (SWAT) in conjunction with a Latin hypercube climate change sampling algorithm to construct a 95% confidence interval (95CI) arou...

Use of pesticides over impervious surfaces like concrete and subsequent washoff and offsite transport significantly contribute to pesticide detection and aquatic toxicity in urban watersheds. This paper presents a comprehensive study on pesticide washoff from concrete surfaces, including reviews of reported experiments and existing models, developm...

The assessment of hydrologic responses to climate change is required in watershed management and planning to protect water resources and environmental quality. This study is designed to evaluate and enhance watershed modeling approach in characterizing climate change impacts on water supply and ecosystem stressors. Soil and Water Assessment Tool (S...

Agricultural pollutant runoff is a major source of water contamination in California's Sacramento River watershed where 8500 km2 of agricultural land influences water quality. The Soil and Water Assessment Tool (SWAT) hydrology, sediment, nitrate and pesticide transport components were assessed for the Sacramento River watershed. To represent flood...

Modeling approaches for pesticide regulation are required to provide generic and conservative evaluations on pesticide fate and exposure based on limited data. This study investigates the modeling approach for pesticide simulation in a rice paddy, by developing a component-based modeling system and characterizing the dependence of pesticide concent...

This study presents a comprehensive investigation of the State Soil Geographic Database (STATSGO) and the Soil Survey Geographic Database (SSURGO) soil databases for their applications in hydrologic modeling practices, and provides detailed instructions on soil data aggregation. Two types of soil data aggregations are developed and improved for the...

Purpose The purpose of the present study are to analyze the temporal and spatial trends of the pesticide use on almond crops and assess their associated risk to soil, surface water, and air, and to investigate the impacts of pesticide risk on biodiversity. Materials and methods California Pesticide Use Report database was used to determine the org...

Northwest China is the driest region in China and the regional climate fluctuated dramatically during the last century. Aridity index, as the ratio between potential evapotranspiration and precipitation, is a good indicator to represent regional climate character. In this study, the change and attribution of the aridity index was investigated in no...

The Danjiangkou Reservoir is the headwater source of the central route of China's South to North Water Diversion Project (SNWDP). Average annual streamflow into the Reservoir was 40.97 km3 from 1951 to 1989, while it was 31.64 km3 from 1990 to 2006. Between the two periods, the average annual streamflow was reduced by 9.33 km3, accounting for 71.8%...

We develop a stream temperature model within the Soil and Water Assessment Tool (SWAT) that reflects the combined influence of meteorological (air temperature) and hydrological conditions (streamflow, snowmelt, groundwater, surface runoff, and lateral soil flow) on water temperature within a watershed. SWAT currently uses a linear air-stream temper...

Pesticide use in paddy rice production may contribute to adverse ecological effects in surface waters. Risk assessments conducted for regulatory purposes depend on the use of simulation models to determine predicted environment concentrations (PEC) of pesticides. Often tiered approaches are used, in which assessments at lower tiers are based on rel...

Changes in snowmelt runoff due to climate change are expected to impact seasonal stream temperatures and associated biogeochemical processes. Many hydrologic models, such as the soil water assessment tool (SWAT), determine stream temperature based solely on a linear relationship with air temperature. However, in situations where warmer spring tempe...

This study aims to determine temporal trends and spatial distribution of the annual and monthly precipitation in the Haihe River Basin, China, during 1951–2008. A significant decreasing trend was observed for the annual precipitation, mainly attributed to the abrupt decrease in the flood-season precipitation (June–September) around the year of 1979...

Pan-evaporation (Epan) as the indicator of atmospheric evaporative demand has decreased worldwide with climate change in the last decades, which is called "Pan Evaporation Paradox". This study investigates the recent changes in Epan dynamics in China using the observed Epan records for the period 1960-2007. The records show that Epan decreased in C...

Field-scale environmental models have been widely used in aquatic exposure assessments of pesticides. Those models usually require a large set of input parameters and separate simulations for each pesticide in evaluation. In this study, a simple use-exposure relationship is developed based on regression analysis of stochastic simulation results gen...

Synthetic pyrethroid insecticides have generated public concerns due to their increasing use and potential effects on aquatic ecosystems. A modeling system was developed in this study for simulating the transport processes and associated sediment toxicity of pyrethroids at coupled field/watershed scales. The model was tested in the Orestimba Creek...

This paper reports a study on the impact of resource use, irrigation in particular, on farm productivity in the upper and middle parts of the Yellow River basin, China. A comprehensive database was constructed with processed geographical, climatic, hydrologic, and economic data to provide information for the current and future studies. Descriptive...

Field runoff is an important transport mechanism by which pesticides move into the hydrologic environment of intensive agricultural regions such as California's Central Valley. This study presents a spatially explicit modeling approach to extend Pesticide Root Zone Model (PRZM), a field-scale pesticide transport model, into basin level. The approac...

The Soil and Water Assessment Tool (SWAT) was used to assess the impact of climate change on sediment, nitrate, phosphorus and pesticide (diazinon and chlorpyrifos) runoff in the San Joaquin watershed in California. This study used modeling techniques that include variations of CO(2), temperature, and precipitation to quantify these responses. Prec...

The Soil and Water Assessment Tool (SWAT) was calibrated for hydrology conditions in an agricultural watershed of Orestimba Creek, California, and applied to simulate fate and transport of two organophosphate pesticides chlorpyrifos and diazinon. The model showed capability in evaluating pesticide fate and transport processes in agricultural fields...

Quantifying the hydrological response to an increased atmospheric CO2 concentration and climate change is critical for the proper management of water resources within agricultural systems. This study modeled the hydrological responses to variations of atmospheric CO2 (550 and 970 ppm), temperature (+1.1 and +6.4 °C), and precipitation (0%, ±10%, an...

This paper presents a framework for cumulative risk characterization of human exposure to pesticides through multiple exposure pathways. This framework is illustrated through a case study of selected organophosphate (OP) pesticides in the northern San Joaquin Valley of California. Chemical concentrations in environmental media were simulated using...

A geo-referenced modeling system was developed in this study to investigate the spatiotemporal variability of pesticide distributions and associated ecosystem risks. In the modeling system, pesticide fate and transport processes in soil-canopy system were simulated at field scale by the pesticide root zone model (PRZM). Edge-of-field mass fluxes we...

The quantification of the hydrological response to climate change and increasing atmospheric CO2 concentrations is required for the proper management of agricultural systems and water resources. This study simulated variations in CO2, temperature and precipitation to quantify the hydrologic response in an intensive agricultural system. The Soil and...

In the last decade, the detection of organophosphate (OP) pesticides in the San Joaquin River watershed has raised concerns about water quality. This study examined the influences of almond pest management practices (PMPs) on water quality. The Soil and Water Assessment Tool (SWAT) model was employed to simulate pesticide concentration in water as...

The hydrology, sediment, and pesticide transport components of the Soil and Water Assessment Tool (SWAT) were evaluated on the northern San Joaquin Valley watershed of California. The Nash-Sutcliffe coefficients for monthly stream flow and sediment load ranged from 0.49 to 0.99 over the watershed during the study period of 1992-2005. The calibrated...

The impact of inputs on farm production growth was evaluated by analyzing the economic data of the upper and middle parts of the Yellow River basin, China for the period of 1980–1999. Descriptive statistics were employed to characterize the temporal trends and spatial patterns in farm production and five pertinent inputs of cultivated cropland, irr...

A geo-referenced environmental fate model was developed for analyzing unsteady-state dispersion and distribution of chemicals in multimedia environmental systems. Chemical transport processes were formulated in seven environmental compartments of air, canopy, surface soil, root-zone soil, vadose-zone soil, surface water, and sediment. The model ass...

A multimedia environmental fate model was developed to study the temporal dynamics and spatial distribution of a chemical pollutant at watershed scale. The theoretical considerations and implementation of the model were described in the accompanying paper (Part I). This paper presents the result of a test simulation on the transport of trichloroeth...

This paper presented a framework for analysis of chemical concentration in the environment and evaluation of variance propagation within the model. This framework was illustrated through a case study of selected organic compounds of benzo[α]pyrene (BAP) and hexachlorobenzene (HCB) in the Great Lakes region. A multimedia environmental fate model was...

A fugacity-based multimedia model was presented in this paper to predict chemical distribution at a basin scale. The core transport simulation was based on a geo-referenced multimedia environmental model developed at the University of Connecticut. To account for the heterogeneity of environmental characteristics of the territory, a detailed descrip...

A geo-referenced environmental fate model was developed for analyzing unsteady-state dispersion and distribution of chemicals in multimedia environmental systems. Chemical transport processes were formulated in seven environmental compartments of air, canopy, surface soil, root-zone soil, vadose-zone soil, surface water, and sediment. The model ass...

Analyses were performed to evaluate the impact of resources and technological inputs on farm production in northwestern China, including five provincial districts of Shaanxi, Gansu, Ningxia, Qinghai, and Xinjiang. The gross value of farm production using 1978 constant prices was chosen to be the dependent variable in data analysis. Input variables...

A geo-referenced environmental fate model was developed for analyzing unsteady-state dispersion and distribution of chemicals in multimedia environmental systems. In this model, chemical transport processes in various environmental media were incorporated in a GIS-based framework, to support spatial characterization and time-dependent parameter est...

A comprehensive analysis on resources sustainability and farm production in Northwest China is discussed. A comparison between irrigated land and rainfed land showed that farm productivity is depended on irrigation in this region. The impact of overall improvement in agriculture infrastructure and education accounted for over a quarter of the incre...

A high-resolution model was presented in this study for estimating the environmental fate and distribution of multi-species chemicals. This model was based on the GIS-integrated multimedia modeling (GIM3) framework developed in the University of Connecticut. The current model had a more detailed environmental description than previous multimedia mo...

A network of eight monitoring stations was established to study the atmospheric nitrogen concentration and deposition in the State of Connecticut. The stations were classified into urban, rural, coastal and inland categories to represent the geographical location and land use characteristics surrounding the monitoring sites. Nitrogen species includ...

A GIS-integrated spatial-compartmental modeling approach was presented for analyzing the dynamic transport and distribution of chemicals in the multimedia environment system. The intermedia mass transport processes were incorporated into a GIS-based modeling framework, which supported the multi-media analysis and exposure assessment by simulating t...

Four monitoring stations were established along the Connecticut coastline to study the atmospheric deposition of nitrogen into the Long Island Sound (LIS). Two stations at Bridgeport and Hammonasset were set up in 1991. Two additional ones have been in full operation since 1997 at Old Greenwich and Avery Point. Measurements were taken continuously...

The USDA-NRCS Soil Survey Geographic (SSURGO) dataset provides the most comprehensive, detailed soil data coverage across the United States. Correct usage of these data within a hydrologic model depends on assumptions that define how soil property data are aggregated. To reduce data intensity and improve model efficiency, most hydrologic modeling s...