Laosheng Wu

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

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.

Simultaneous determination of pharmaceuticals, endocrine disrupting compounds and hormone in soils by gas chromatography-mass spectrometry.

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.

Effects of soil water repellency on infiltration rate and flow instability

Laboratory infiltration experiments were carried out to quantify the effects of soil water-repellency on infiltration rate and the wetting front instability. A two-dimensional transparent chamber (41.5 cm wide, 50 cm high and 2.8 cm thick) was constructed for infiltration experiments using three water-repellent Ouddorp sands (The Netherlands) and a wettable silicon sand. The results showed that if the water-ponding depth (h0) at the soil surface was lower than the water-entry value (hwe) of repellent sands, infiltration would not start until the water drop penetration time (WDPT) is exceeded; and contrary to infiltration in wettable soils, the infiltration rate increased with time. However, infiltration could immediately start at any time whenh0 . hwe: The wetting front was unconditionally unstable for h0 , hwe; resulting in fingered flow. However, the flow was conditionally stable for h0 . hwe if the soil was not layered in a fine-over-coarse or wettable-over-repellent configuration, and if soil air was not compressed during infiltration. The occurrence of stable and unstable flow in repellent soils was consistent with the prediction based on a linear instability analysis. The findings can be used to improve irrigation efficiencies in water repellent soils, e.g. using high-ponding irrigation methods. q 2000 Elsevier Science B.V. All rights reserved.

Assessing the soil quality of long-term reclaimed wastewater-irrigated cropland

The properties of soils may be characterized by many attributes. However, there is not a systematic procedure to objectively select the measurement parameters that may be used to assess soil quality. Following the data collection, it is often a dilemma to decide how many and which of the measured parameters should be included in the assessment as the outcomes may be influenced by the parameters included. In this study, 29 physical, chemical, and biological attributes of soils at a long-term reclaimed wastewater-irrigated field in Bakersfield, CA and its adjacent non-wastewater-irrigated control were determined with samples collected along a 100-m transect at 1-m interval. The fields have been cultivated with varieties of field crops over the past 70 years. The spatial variability of the data was evaluated. The principal component method was employed to identify the soil attributes that were most significant in describing variances of the fields. Soil quality of the treated and control fields were compared using the principal components identified in this process. Results indicated that the soil quality might be evaluated by comparing the total porosity (or drainable porosity), pH, electrical conductivity (EC), magnesium (Mg), phosphorus (P), and zinc (Zn) of soils in the control and the treated fields. Except for the total porosity and Mg, the other soil parameters of the control and treated fields were not significantly different. While the soils of both fields support successful crop production, the reclaimed wastewater irrigation appeared to slightly increase the soil compaction and reduce the soils capacity of holding nutrient elements, such as Mg.

A hybrid global optimization method for inverse estimation of hydraulic parameters: Annealing‐Simplex Method

Inverse estimation of unsaturated hydraulic parameters is often a highly nonlinear optimization problem with multiple parameters. The objective functions involved are often topographically complex and may contain many local minima. Because of these reasons, the inverse solutions are commonly very sensitive to the initial guess of the parameters when conventional optimizers are used. This paper presents an annealing-simplex method that incorporates simulated annealing strategies into a classical downhill simplex method. An upward infiltration experiment was used as an example of inverse estimation to test the method. Numerical experiments of both minimizing an algebraic function and inversion of upward infiltration data showed that the new method successfully converged to the global minimum in all cases, irrespective of the initial hydraulic parameter estimates, while the classical downhill method often converged to unfavorable local minima. The CPU times needed for the annealing-simplex method to estimate 5 and 7 hydraulic parameters simultaneously are about a half hour and 1 hour on a PC, respectively. Additionally, no special requirements are imposed on the objective function, and the method is independent of the details of the simulation submodel. Therefore the proposed method should be applicable to other optimization problems in water resources when it is important to have a robust global search capability.

Water-entry value as an alternative indicator of soil water-repellency and wettability

Abstract Soil water-repellency is an increasingly important consideration in hydrology. In this paper, we relate the degree of soil water-repellency and wettability to the critical water-entry value of a soil. A water-ponding method was used for simple measurement of water-entry value in repellent soils. A tension–pressure infiltrometer method was demonstrated for measuring water-entry value in both repellent and wettable soils. The measurement techniques were used to detect a sudden breakdown of repellency under a sufficiently high water pressure. Experimental results have proven that the water-entry value, in terms of soil water potential, is positive in repellent soils, and negative in wettable soils or soil conditions. The water-entry value is shown to be an easily measured indicator of repellency or wettability that provide an assessment of hydraulic effects of soil physical, chemical and biological properties.

Analysis of endocrine disrupting compounds, pharmaceuticals and personal care products in sewage sludge by gas chromatography–mass spectrometry

Endocrine disrupting compounds (EDCs) and pharmaceuticals and personal care products (PPCPs) have been acknowledged as emerging pollutants due to widespread contamination in environment. A rapid and reliable analytical method, based on ultrasonic extraction, clean up on Envi-carb cartridge, derivatized with N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide (MTBSTFA), and analyzed by gas chromatography-mass spectrometry (GC-MS), was developed for determination of 4 EDCs (bisphenol A, estrone, nonylphenol and octylphenol) and 10 PPCPs (acetylsalicylic acid, carbamazepine, clofibric acid, diclofenac, gemfibrozil, ibuprofen, ketoprofen, naproxen, paracetamol and triclosan) in sewage sludge. Mean recoveries of the target analytes, at different spike levels (40, 300 and 2000 ng/g), ranged from 57.9% to 103.1%. Relative standard deviations (RSDs) were in the range of 1.3-9.5% at different spiked levels. The limit of quantification (LOQ) ranged from 4.7 to 39 ng/g. The method was applied to sewage sludge samples from sewage treatment plants (STPs) in southern California. High concentrations of PPCPs and EDCs were found in sewage sludge, ranging from 1502 to 5327 ng/g dry weight. Appropriate disposal of sewage sludge was required to avoid secondary contamination.

Leachability of some emerging contaminants in reclaimed municipal wastewater-irrigated turf grass fields.

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.

Soil enzyme activities of long-term reclaimed wastewater-irrigated soils.

Studies have shown that physical and chemical properties of soils may be significantly changed when they are subjected to long-term reclaimed water irrigation. It remains unclear how reclaimed water application may affect nutrient cycling in soils. Soil enzymes are responsible for the biogeochemical cycling of many elements and are more sensitive indicators of the ecological changes. In this study, 17 soil enzymes, including those associated with the C, N, P, and S cycles and two oxidoreductases (catalase and dehydrogenase), were assayed in soils obtained from five long-term reclaimed wastewater irrigation sites in southern California. The soil enzyme activities varied widely among the sampling sites. Compared with their respective controls, the overall activities of enzymes involved in the cycling of the four elements in soil were enhanced by an average of 2.2- to 3.1-fold. Principal component analysis and cluster analysis indicated that the soil microbial functional diversity may be evaluated based on activities of catalase, alkaline phosphatase, acid phosphatase, dehydrogenase, and urease.

Effect of dissolved organic carbon on sorption of pyrethroids to sediments.

Despite their strong hydrophobicity, recent studies showed widespread occurrence of pyrethroid in downstream surface waters bodies. In this work, the effect of dissolved organic carbon (DOC) on the sorption and desorption of pyrethroids in sediment was evaluated to understand the role of DOC in facilitating pyrethroid transport. Presence of DOC from three sources at 38 ± 2 mg L⁻¹ in the aqueous phase decreased pesticide sorption to a sediment by 1.7 to 38.9 times and increased their desorption by 1.2 to 41.4 times. The effect on pyrethroid sorption to the sediment was linear. In addition, interactions between DOC and pyrethroids, when taking place prior to the contact with sediment, decreased sorption of some pyrethroids even further, implying that DOC-pyrethroid complexs were relatively stable in solution. DOC sources with higher contents of carboxylic and phenolic groups were found to have a higher potential to associate with pyrethroids. The DOC-water partition coefficients (K(DOC)) obtained by solid-phase microextraction measurement were significantly correlated (P < 0.01) with K(d) values measured for the sediment. These results provide evidence that DOC increases the distribution of pyrethroids from the sediment to the solution phase and plays an important role in mobilizing pyrethroids in runoff and surface streams.