Andrew C Chang

Publications (27)58.94 Total impact

• Article: Seasonal variation of endocrine disrupting compounds, pharmaceuticals and personal care products in wastewater treatment plants.

  Yong Yu, Laosheng Wu, Andrew C Chang
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  ABSTRACT: The occurrence of 14 endocrine disrupting compounds (EDCs), pharmaceuticals and personal care products (PPCPs) in influents, effluents and sludge from five wastewater treatment plants (WWTPs) in southern California was studied in winter and summer. All 14 compounds were detected in influent samples from the five WWTPs except for estrone. Paracetamol, naproxen and ibuprofen were the dominant compounds, with mean concentrations of 41.7, 35.7 and 22.3μg/L, respectively. The treatment removal efficiency for most compounds was more than 90% and concentrations in the effluents were relatively low. Seasonal variation of the compounds' concentration in the wastewater was significant: the total concentration of each compound in the wastewater was higher in winter than in summer, which is attributed to more human consumption of pharmaceuticals during winter and faster degradation of the compounds in summer. The highest concentrations of triclosan and octylphenol were detected in sewage sludge, with mean concentrations of 1505 and 1179ng/g, respectively. Risk quotients (RQs), expressed as the ratios of environmental concentrations and the predicted no-effect concentrations (PNEC), were less than unity for all the compounds except for estrone in the effluents, indicating no immediate ecological risk is expected. However, RQs were higher than unity for 2 EDCs (estrone and octylphenol) and carbamazepine in sludge samples, indicating a significant ecotoxicological risk to human health. Therefore, appropriate treatment of sewage sludge is required before its application.
  Science of The Total Environment 11/2012; 442C:310-316. · 3.29 Impact Factor
• Article: Environmental risks of trace elements associated with long-term phosphate fertilizers applications: a review.

  Wentao Jiao, Weiping Chen, Andrew C Chang, Albert L Page
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  ABSTRACT: Application of phosphate fertilizer can be a significant contributor of potentially hazardous trace elements such as arsenic, cadmium, and lead in croplands. These trace elements have the potential to accumulate in soils and be transferred through the food chain. We articulated the environmental risks of trace elements associated with long-term phosphate fertilizer applications by combining data from the literature and results from model simulations. Results illustrate that under normal cropping practice, the impact of phosphate fertilizers applications on trace element accumulation in receiving soils has been limited and localized. Their plant uptake varied greatly depending on the fertilizer application rates, soil and plant characteristics. This has led to a great deal of uncertainty in characterizing soil distribution coefficients, Kd, and plant uptake factors, PUF, two of the most used parameters in assessing the risks of accumulations. Therefore, the risks may be more appropriately assessed based on the probabilistic distributions of Kd and PUF.
  Environmental pollution (Barking, Essex: 1987) 05/2012; 168:44-53. · 3.43 Impact Factor
• Article: Fertilizer Applications and Trace Elements in Vegetable Production Soils of California

  Weiping Chen, Natalie Krage, Laosheng Wu, Albert L. Page, Andrew C. Chang
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  ABSTRACT: We collected and analyzed over 600 soil samples from the vegetable production fields in seven regions across California, examining the total As, Cd, Pb, P, and Zn concentrations of the soils. The ranges for baseline concentrations were determined for each region. The total P and Zn contents of the soils in comparison to the baseline ranges served as indicators on P fertilizers and micronutrients inputs through cultivation, the greater the total contents the larger the inputs. When the soil As, Cd, and Pb concentrations of each region were plotted with respect to those of P and Zn, three data distribution patterns emerged: (1) the soil As, Cd and Pb concentrations of the cropland soils remained within the baseline range regardless of the phosphorus or zinc inputs in 5, 2, 4 of the 7 regions, respectively, (2) the soil As, Cd and Pb concentrations of the cropland soils had moved upward and exceeded the baseline ranges but their concentrations did not rise in proportion to the phosphorus or zinc concentrations of soils in 1, 4, and 3 of the 7 regions, respectively. The enrichment was due to diffuse sources other than phosphorus fertilizers or micronutrients. (3) The soil As and Cd concentrations of the cropland soil in the Oxnard/Ventura Area and Fresno showed trends of increasing with respect to inputs of P and or Zn indicating P fertilizer or micronutrients applications over time have caused As and Cd to slowly accumulate in the cropland soils.
  Water Air and Soil Pollution 04/2012; 190(1):209-219. · 1.63 Impact Factor
• Article: Evaluating Henry's law constant of N-nitrosodimethylamine (NDMA).

  Shinsuke Haruta, Wentao Jiao, Weiping Chen, Andrew C Chang, Jay Gan
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  ABSTRACT: N-Nitrosodimethylamine (NDMA), a potential carcinogen, may contaminate the groundwater when the reclaimed wastewater is used for irrigation and groundwater recharge. Henry's law constant is a critical parameter to assess the fate and transport of reclaimed wastewater-borne NDMA in the soil profile. We conducted a laboratory experiment in which the change of NDMA concentration in water exposed to the atmosphere was measured with respect to time and, based on the data, obtained the dimensionless Henry's law constant (K(H)') of NDMA, at 1.0 x 10(-4). The K(H)' suggests that NDMA has a relatively high potential to volatilize in the field where NDMA-containing wastewater is used for irrigation and the volatilization loss may be a significant pathway of NDMA transport. The experiment was based on the two boundary-layer approach of mass transfer at the atmosphere-water interface. It is an expedient method to delineate K(H)' for volatile or semi-volatile compounds present in water at low concentrations.
  Water Science & Technology 01/2011; 64(8):1636-41. · 1.12 Impact Factor
• Article: Impact of long-term reclaimed wastewater irrigation on agricultural soils: a preliminary assessment.

  Jian Xu, Laosheng Wu, Andrew C Chang, Yuan Zhang
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  ABSTRACT: The effect of reclaimed wastewater irrigation on the alteration of soil properties and accumulation of trace metals in soil profiles was investigated by monitoring different plots from Palmdale, California that had been irrigated with effluents for various lengths of time (3, 8, and 20 years, respectively). The non-effluent-irrigated plot served as the control and provided reference "background" values. Total metals at different soil depths were analyzed by acid digestion, and EDTA-extractable metals were analyzed as available fraction. Results show that soil pH values were significantly (p<0.05) lowered in plots with 20-year irrigation to a depth of 140 cm, while EC was elevated for all three plots compared with control. OM, TC and TN contents increased in the top 10-cm soil layers in plots with 8- and 20-year effluent irrigation. Irrigation with effluents also increased both the total and EDTA-extractable metals in the fields. It showed that long-term effluent irrigation could be of agricultural interest due mainly to its organic matter concentrations and nutrients input, however, trace contaminants such as heavy metals in the upper horizons may be accumulated, which may eventually lead to deterioration of soil and groundwater quality and affect the sustainability of land-based disposal of effluent.
  Journal of hazardous materials 11/2010; 183(1-3):780-6. · 4.14 Impact Factor
• Article: A root exudates based approach to assess the long-term phytoavailability of metals in biosolids-amended soils.

  Bon-Jun Koo, Weiping Chen, Andrew C Chang, Albert L Page, Thomas C Granato, Robert H Dowdy
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  ABSTRACT: Organic acids present in the rhizosphere of growing plants are widely recognized to be responsible for dissolving the solid phase metals in the soil and making them available for plant absorption. We proposed a root exudates-based model to assess the long-term phytoavailability of metals in biosolids-amended soils. The phytoavailability of biosolids-borne metals was defined in terms of a capacity factor and an intensity factor. The plant available metal pool, C(0) (capacity factor, mgkg(-1)), can be estimated by fitting the successive organic acids extraction data to an exponential decay kinetic equation. The field metal removal rate, k (intensity factor, yr(-1)), can be estimated from the successive extraction-based metal release rate through an effective annual organic acid production in the rhizosphere which was found to be characteristic of plant species. The protocol was successfully used to assess the long-term phytoavailability of metals in biosolids-amended soil from two biosolids land application sites.
  Environmental pollution (Barking, Essex: 1987) 08/2010; 158(8):2582-8. · 3.43 Impact Factor
• Article: Uptake of metals by food plants grown on soils 10 years after biosolids application.

  Yanying Bai, Weiping Chen, Andrew C Chang, Albert L Page
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  ABSTRACT: Potentially hazardous trace elements such as Cd, Cu, Cr, Ni and Zn are expected to accumulate in biosolids-amended soil and remain in the soil for a long period of time. In this research, uptake of metals by food plants including cabbage, carrot, lettuce and tomato grown on soils 10 years after biosolids application was studied. All the five metals were significantly accumulated in the biosolids-amended soils. The accumulation of metal in soil did not result in significant increase in concentrations of Cu, Cr and Ni in the edible plant tissues. However, the Cd and Zn concentrations of the edible tissues of plants harvested from the biosolids receiving soils were significantly enhanced in comparison with those of the unaffected soils. The plant uptake under Greenfield sandy loam soil was generally higher than those under the Domino clayey loam soil. The metal concentration of edible plant tissue exhibited increasing trends with respect to the concentrations of the ambulated metals. The extents of the increases were plant species dependent. The indigenous soil metals were absorbed by the plants in much higher rates than those of the biosolids-receiving soils. It appeared that the plant uptake of the indigenous soil-borne metal and the added biosolids-borne metals are independent of one another and mathematically are additive.
  Journal of Environmental Science and Health Part B Pesticides Food Contaminants and Agricultural Wastes 08/2010; 45(6):531-9. · 1.10 Impact Factor
• Article: Soil Temperature Regimes of the Mojave Desert

  Yanying Bai, Thomas A. Scott, Weiping Chen, Robert C. Graham, Laosheng Wu, Andrew C. Chang, Lanny J. Lund
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  ABSTRACT: Soil temperature is an important attribute of classifying and assessing soil resources. It is a key environmental factor to determine soil formation and natural distribution of plants. The spatial distribution of soil temperature regimes is essential for accurate identification of soils and inventory of natural resources. Through efforts initiated more than two decades ago, a long-term continuous soil temperature database covering the full range of elevation, aspects, longitude, and latitude of the Mojave Desert region has been assembled and analyzed. Results show that elevation was the dominant factor governing the spatial variation of soil temperature in the Mojave Desert region. A soil temperature regime map was constructed with support of geographic information system software based on the linear regression relationship between the mean annual soil temperature and elevation. Most soils of this region are in the hyperthermic or thermic temperature regimes. The frigid soil temperature regime was only observed in high mountain areas, at elevations higher than 2,918 m. The seasonal mean soil temperatures also decrease linearly with increased elevation. At the same elevation, the differences between summer and winter soil temperatures are around 20°C. The effect of elevation on soil temperature is more pronounced in summer than in winter season.
  Soil Science 07/2010; 175(8):398-404. · 1.14 Impact Factor
• Chapter: Trace Elements in Biosolids‐Amended Soils

  Weiping Chen, Andrew C. Chang, Laosheng Wu, Albert L. Page, Bonjun Koo
  04/2010: pages 111 - 133; , ISBN: 9781444319477
• Article: Leaching potential of nonsteroidal anti-inflammatory drugs in soils.

  Jian Xu, Laosheng Wu, Weiping Chen, Andrew C Chang
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  ABSTRACT: Nonsteroidal anti-inflammatory drugs (NSAIDs) in soils resulting from application of municipal wastewater or biosolids may migrate through soils intact or be transformed and reach groundwater. In the present study, the leaching potential of four NSAIDs (ibuprofen, naproxen, ketoprofen, and diclofenac sodium) in three U.S. cropland soils was evaluated, and the effect of CaCl(2) solution (as an index of salinity), dissolved organic matter (DOM), and polyacrylamide (PAM) amendment was investigated. The soils were spiked with selected NSAIDs, incubated for 24 h followed by 7-d storage in glass flasks, and then packed into stainless steel columns and leached with deionized water (DIW), 10 mM CaCl(2), DOM (DOC 34 mg/L), and PAM solution (1.0 mg/L) by gravity. Initial concentrations of ibuprofen, naproxen, ketoprofen, and diclofenac sodium in the three packed soils were 1.93 to 2.07, 1.74 to 2.27, 1.79 to 2.16, and 1.99 to 2.13 mg/kg, respectively. Maximum concentrations of the above NSAIDs in column effluents were 1.23, 0.92, 0.69, and 1.12 mg/L, respectively, when the soil was leached with 10 pore volumes of water, which occupied 17.4, 11.1, 9.6, and 15.2% of the total chemicals in each soil column. Dissolved organic matter or PAM solution did not facilitate the NSAIDs release from soils. The CaCl(2) solution, however, reduced the amounts of NSAIDs leached from all three soils. Leaching of NSAIDs differed among the three tested soils. The results suggest that the leaching of NSAIDs through soil to water is significant, and the mobility of NSAIDs in soil is related to their chemicals' characteristics (such as pK(a) values) and soil properties (such as soil organic matter and clay content). Amending soil with DOM or PAM does not significantly affect the leaching behavior of NSAIDs in soil, whereas increasing the salinity of the irrigation water may decrease the extent of contamination of groundwater posed by NSAIDs.
  Environmental Toxicology and Chemistry 04/2010; 29(4):800-7. · 2.81 Impact Factor
• Source

  Available from: uni-hohenheim.de

  Article: Degradation and adsorption of selected pharmaceuticals and personal care products (PPCPs) in agricultural soils.

  Jian Xu, Laosheng Wu, Andrew C Chang
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  ABSTRACT: Pharmaceuticals and personal care products (PPCPs) are emerging contaminants in the environment, which have drawn popular concerns recently. Most studies on the environmental fate of PPCPs have focused on their behaviors during wastewater treatment processes, in aquatic environments, and in the sludge, however, little is known about their behavior in agricultural soils. In this study, adsorption and degradation of six selected PPCPs, including clofibric acid, ibuprofen, naproxen, triclosan, diclofenac and bisphenol A have been investigated in the laboratory using four US agricultural soils associated with reclaimed wastewater reuse. Adsorption test using a batch equilibrium method demonstrated that adsorption of all tested chemicals in soils could be well described with Freundlich equation, and their adsorption affinity on soil followed the order of triclosan>bisphenol A>clofibric acid>naproxen>diclofenac>ibuprofen. Retardation factor (R(F)) suggested that ibuprofen had potential to move downward with percolating water, while triclosan and bisphenol A were readily retarded in soils. Degradation of selected PPCPs in soils generally followed first-order exponential decay kinetics, with half-lives ranging from 0.81 to 20.44 d. Degradation of PPCPs in soils appeared to be influenced by the soil organic matter and clay contents. Sterilization generally decreased the degradation rates, indicating microbial activity played a significant role in the degradation in soils. The degradation rate constant decreased with increasing initial chemical concentrations in soil, implying that the microbial activity was inhibited with high chemical loading levels.
  Chemosphere 11/2009; 77(10):1299-305. · 3.21 Impact Factor
• Article: Leachability of some emerging contaminants in reclaimed municipal wastewater-irrigated turf grass fields.

  Jian Xu, Weiping Chen, Laosheng Wu, Robert Green, Andrew C Chang
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  ABSTRACT: Emerging pollutants inherent in reclaimed municipal wastewater, including endocrine-disrupting compounds (EDCs) and pharmaceutical and personal care products (PPCPs), often have cast uncertainties on the safety of water reuse. We examined the fate and transport behavior of several PPCP and EDC compounds through observations made at experimental turf fields irrigated with naproxen, clofibric acid, diclofenac sodium, ibuprofen, estrone, 4-tert-octylphenol, bisphenol A, 4-n-nonylphenol, and triclosan latent irrigation water. The potential of the compounds to contaminate underlying groundwater was assessed using three screening protocols that employed the attributes of soils, chemicals, and water fluxes as the estimators. No compound was detected in the leachate draining through the 89-cm profile of a loamy sand soil and a sandy loam soil turf grass field during four months of irrigation according to operations typical of golf courses in southern California (USA). Ibuprofen, naproxen, triclosan, bisphenol A, clofibric acid, and estrone were detected in the surface to 30-cm soil profiles. Higher irrigation rate and coarser textural soil enhanced the downward movement of chemicals in both soils. The pollution risk screenings identified the same six compounds as having the potential to contaminate groundwater, and under conditions of turf grass irrigation, clofibric acid and ibuprofen would be most prone to cause the pollution.
  Environmental Toxicology and Chemistry 05/2009; 28(9):1842-50. · 2.81 Impact Factor
• Article: Cadmium Uptake by Lettuce in Fields Treated with Cadmium‐Spiked Phosphorus Fertilizers

  Weiping Chen, Lianqing Li, Andrew C. Chang, Laosheng Wu, Soon‐Ik Kwon, Rick Bottoms
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  ABSTRACT: The rate of cadmium (Cd) uptake by lettuce (Lactuca savita var. longifolia) over an entire growing season was investigated in a field treated with phosphorus (P) fertilizers spiked to different Cd levels. Romaine lettuce was planted following the standard cultivation practices. Over the growing period, soil and plant samples were taken to determine the total soil Cd content, Cd concentration of 1:0.5 (soil‐to‐water) extracts, and Cd content of plant tissue. Results indicated that lettuce can accumulate as much as 20 mg Cd per kilogram dry biomass without adverse effects on growth. The Cd content in the plant tissues decreased exponentially with time, indicating a dilution factor existing along with the plant growth. The plant uptake rate on a per‐unit‐area basis increased over time and can be simulated by a sigmoid pattern model. The plant uptake coefficient (α, L solution kg biomass−1 day−1) decreased as the Cd treatment level increased.
  Communications in Soil Science and Plant Analysis 04/2009; 40(7-8):1124-1137. · 0.51 Impact Factor
• Article: Simultaneous determination of pharmaceuticals, endocrine disrupting compounds and hormone in soils by gas chromatography-mass spectrometry.

  Jian Xu, Laosheng Wu, Weiping Chen, Andrew C Chang
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  ABSTRACT: Analytical methods have been developed for simultaneous determination of six different pharmaceuticals and personal care products (PPCPs) (clofibric acid, ibuprofen, naproxen, ketoprofen, diclofenac, and triclosan), three endocrine disrupting compounds (EDCs) (4-tert-octylphenol, 4-n-nonylphenol, and bisphenol A (BPA)) and one estrogenic compound (estrone) in soil matrix. The soils were extracted by different solvents with the help of an ultrasonic treatment at 42 kHz, followed by a solid phase extraction (SPE) as a cleanup procedure. The purified extracts were derivatized with N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA) and then analyzed by GC-MSD (SIM mode). The method was evaluated by testing the following variables: initial spiking levels, extraction solvents, solvent volumes, and soil types (sandy and clay soils). For 5 g of soil, four successive extraction steps with the mixture of acetone-ethyl acetate provided satisfactory recoveries. In the sandy soil, the recoveries of all the compounds were from 63.8 to 110.7% for the spiking level of 100 ng/g dry soil, and from 52.2 to 108.2% for 5 ng/g dry soil, respectively. Result was similar for the clay soil. The precision across all recoveries was high, suggesting that this method has a good reproducibility. The method was successfully employed to soil samples collected from a golf course irrigated with reclaimed wastewater in southern California, and resulted in the detection of clofibric acid, ibuprofen, naproxen, triclosan, bisphenol A, and estrone at ng per gram dry weight concentration levels. The method is robust and simple, and provides straightforward analyses of these current-emerging trace organic pollutants in solid matrices.
  Journal of Chromatography 08/2008; 1202(2):189-95. · 4.53 Impact Factor
• Source

  Available from: pc-progress.com

  Article: Leaching risk of N-nitrosodimethylamine (NDMA) in soil receiving reclaimed wastewater.

  Shinsuke Haruta, Weiping Chen, Jay Gan, Jirka Simůnek, Andrew C Chang, Laosheng Wu
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  ABSTRACT: N-nitrosodimethylamine (NDMA) is a potential carcinogen frequently found in treated wastewater as a byproduct of chlorination. The potential for NDMA to contaminate the groundwater is a significant concern. A solute fate and transport model, Hydrus-1D, was used to evaluate the leaching potential of NDMA under different irrigation practices and soil properties. The results indicate that the risk of NDMA to reach the ground water is slim, when the reclaimed wastewater is applied under the customary conditions for landscape irrigation. The NDMA disappears in the reclaimed wastewater receiving soils rapidly through the microbial degradation and the volatilization processes. The factors that enhance the leaching risk are the soil hydraulic conductivity, the NDMA adsorption constants, and the irrigation intensity. When the hydraulic conductivity of soil is high, the NDMA adsorption constant of soil is low and/or the irrigation intensity is high, the NDMA leaching risk may dramatically increase. To reduce the NDMA leaching risk, it is imperative that the fields be irrigated at the proper volume and frequency and attention be paid to fields with soils having high-hydraulic conductivities and/or low-NDMA adsorption constants.
  Ecotoxicology and Environmental Safety 04/2008; 69(3):374-80. · 2.29 Impact Factor
• Article: Metal uptake by corn grown on media treated with particle-size fractionated biosolids.

  Weiping Chen, Andrew C Chang, Laosheng Wu, Yongsong Zhang
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  ABSTRACT: Particle-size of biosolids may affect plant uptake of heavy metals when the biosolids are land applied. In this study, corn (Zea mays L.) was grown on sand media treated with biosolids to study how particle-size of biosolids affected the plant uptake of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn). Two biosolids, the Nu-Earth biosolids and the Los Angeles biosolids, of dissimilar surface morphology were utilized. The former exhibited a porous and spongy structure and had considerably greater specific surface area than that of the latter, which was granular and blocky. The specific surface area of the Los Angeles biosolids was inversely proportional to its particle-size, while that of Nu-Earth biosolids did not change significantly with particle-size. For each biosolid, the metal concentrations were not affected by particle sizes. The biomass yields of plants grown on the treated media increased as the biosolid particle-size decreased, indicating that plant uptake of nutrients from biosolids was dependent on interactions at the root-biosolids interface. The effect of particle-size on a metal's availability to plants was element-specific. The uptake rate of Cd, Zn, Cu, and Ni was correlated with the surface area of the particles, i.e., smaller particles having higher specific area provided greater root-biosolids contact and resulted in enhanced uptake of Cd and Zn and slightly less increased uptake of Cu and Ni. The particle morphology of biosolids had limited influence on the plant tissue concentrations of Cr and Pb. For both types of biosolids, total metal uptake increased as biosolid particle-size decreased. Our research indicates that biosolid particle-size distribution plays a deciding role in plant uptake of heavy metals when they are land applied.
  Science of The Total Environment 04/2008; 392(1):166-73. · 3.29 Impact Factor
• Article: Modeling uptake kinetics of cadmium by field-grown lettuce.

  Weiping Chen, Lianqing Li, Andrew C Chang, Laosheng Wu, Soon-Ik Kwon, Rick Bottoms
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  ABSTRACT: Cadmium uptake by field grown Romaine lettuce treated with P-fertilizers of different Cd levels was investigated over an entire growing season. Results indicated that the rate of Cd uptake at a given time of the season can be satisfactorily described by the Michaelis-Menten kinetics, that is, plant uptake increases as the Cd concentration in soil solution increases, and it gradually approaches a saturation level. However, the rate constant of the Michaelis-Menten kinetics changes over the growing season. Under a given soil Cd level, the cadmium content in plant tissue decreases exponentially with time. To account for the dynamic nature of Cd uptake, a kinetic model integrating the time factor was developed to simulate Cd plant uptake over the growing season: C Plant=C Solution.PUF max.exp[-b.t], where C Plant and C Solution refer to the Cd content in plant tissue and soil solution, respectively, PUF max and b are kinetic constants.
  Environmental Pollution 04/2008; 152(1):147-52. · 3.75 Impact Factor
• Article: Assessing long-term environmental risks of trace elements in phosphate fertilizers.

  Weiping Chen, Andrew C Chang, Laosheng Wu
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  ABSTRACT: The potential risks originating from arsenic and cadmium accumulations in cropland soils through the fertilizer applications have been public concern. A generalized trace element mass balance model was developed to evaluate the long-term fate and transport of arsenic and cadmium in cropland soils. Model simulation results showed that normal cropping practices do not have a significant effect on the total As content of the receiving soils, but the application of Cd-containing P fertilizers could, over time, cause Cd to accumulate in soil and therefore increases the risk of its transfer through the food chain. Regulations have been enacted in several states to set the maximum contaminant levels for arsenic and cadmium in fertilizers. The simulation outcomes indicated that some of the existing fertilizer regulations are not strict enough to prevent significant accumulation of Cd in cropland soils. Sensitivity analyses show the solid-solution partitioning coefficient, and the plant uptake factors are primary factors that affect the fate and transport of As and Cd in cropland soils. The uncertainty associated with assessing the fate of trace elements in cropland soils is due to the high variability of model parameters.
  Ecotoxicology and Environmental Safety 06/2007; 67(1):48-58. · 2.29 Impact Factor
• Article: Probability Distribution of Cadmium Partitioning Coefficients of Cropland Soils

  Weiping Chen, Andrew C. Chang, Laosheng Wu, Lianqing Li, Soon-Ik Kwon, Albert L. Page
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  ABSTRACT: The solution to solid partitioning coefficient (Kd) is an important parameter in assessing the environmental and health risks of potentially toxic metals in soils. Ideally, the metal in solution phase should be determined at the field moisture condition under which the exposures take place. In reality, it is often represented by the concentration in extracts of a given soil-to-water ratio. Using cadmium (Cd) as an example, we demonstrated the uncertainties in determining the soil solution concentrations in cropland soils where the metal contents are only slightly higher than the baselines. Results of extraction experiments showed the Cd concentration of soil solution under simulated field moisture conditions (i.e., water-to-soil ratio of 0.5) tends to be stochastic and follows a normal distribution. The distribution of Kd of two California cropland soils was quantitatively described by a normal probability distribution function. The normal distribution pattern wasfurther validated by data collected in the field. When Kd is characterized in the probabilistic terms, the risks of environmental andhealth harm of metals in the cropland soils may be more appropriately assessed.
  Soil Science 01/2007; 172(2):132-140. · 1.14 Impact Factor
• Article: Distinguishing sources of groundwater nitrate by 1H NMR of dissolved organic matter.

  Jianhang Lu, Andrew C Chang, Laosheng Wu
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  ABSTRACT: Dissolved organic matter (DOM) originating from a certain source usually carries characteristic marks in its molecular structures that can be recognized by spectroscopic analysis. Sources of water-borne contaminants, such as nitrate, can be identified by recognition of the characteristics of DOM entrained in the water. In this study, DOM in groundwaters sampled from a dairy/crop production area (Chino Basin, CA) was analyzed by 1H nuclear magnetic resonance (1H NMR). Results showed that DOM derived from natural soil organic matter has a characteristic resonance at a chemical shift region of 4.0-4.3 ppm, while DOM derived from dairy wastes has a characteristic resonance at a lower chemical shift region of 3.2-3.6 ppm. These signature resonances were then used to distinguish the origins of nitrate in the groundwater. It was found that disposal of dairy wastes on croplands is the primary source of nitrate contamination in groundwater underlying the Chino Basin dairy area.
  Environmental Pollution 12/2004; 132(2):365-74. · 3.75 Impact Factor