Jack Watson

Radio and Television

Radio transmission and reception was perhaps one of the earliest applications of electronics, and is—so far—the application that has made the greatest impact on society. Oddly, we can use radio, predict its properties and design circuits that work very efficiently, but we know little about the real nature of radio. Ask an electronics engineer what radio is, and the answer will be a confident, ‘Electromagnetic waves.’ Ask a physicist what electromagnetic waves are, and he will begin to hedge, or he will tell you that really we don’t know. We do know that electromagnetic radiation is a form of energy, and that it behaves as if it is propagated as waves. The model becomes more of a model and less like reality when we discover that radio travels through a vacuum. How can there be waves in a vacuum? Perhaps in the future, theoretical physics will give us an answer. In the meantime, we use radio, describe it mathematically, and design and use electronic circuits that function happily despite our underlying ignorance.

Antibiotics in Agroecosystems: Introduction to the Special Section

The presence of antibiotic drug residues, antibiotic resistant bacteria, and antibiotic resistance genes in agroecosystems has become a significant area of research in recent years and is a growing public health concern. While antibiotics are used in both human medicine and agricultural practices, the majority of their use occurs in animal production where historically they have been used for growth promotion, in addition to the prevention and treatment of disease. The widespread use of antibiotics and the application of animal wastes to agricultural lands play major roles in the introduction of antibiotic-related contamination into the environment. Overt toxicity in organisms directly exposed to antibiotics in agroecosystems is typically not a major concern because environmental concentrations are generally lower than therapeutic doses. However, the impacts of introducing antibiotic contaminants into the environment are unknown, and concerns have been raised about the health of humans, animals, and ecosystems. Despite increased research focused on the occurrence and fate of antibiotics and antibiotic resistance over the past decade, standard methods and practices for analyzing environmental samples are limited and future research needs are becoming evident. To highlight and address these issues in detail, this special collection of papers was developed with a framework of five core review papers that address the (i) overall state of science of antibiotics and antibiotic resistance in agroecosystems using a causal model, (ii) chemical analysis of antibiotics found in the environment, (iii) need for background and baseline data for studies of antibiotic resistance in agroecosystems with a decision-making tool to assist in designing research studies, as well as (iv) culture- and (v) molecular-based methods for analyzing antibiotic resistance in the environment. With a focus on the core review papers, this introduction summarizes the current state of science for analyzing antibiotics and antibiotic resistance in agroecosystems, discusses current knowledge gaps, and develops future research priorities. This introduction also contains a glossary of terms used in the core reivew papers of this special section. The purpose of the glossary is to provide a common terminology that clearly characterizes the concepts shared throughout the narratives of each review paper.

Uptake of Three Antibiotics and an Antiepileptic Drug by Wheat Crops Spray Irrigated with Wastewater Treatment Plant Effluent

With rising demands on water supplies necessitating water reuse, wastewater treatment plant (WWTP) effluent is often used to irrigate agricultural lands. Emerging contaminants, like pharmaceuticals and personal care products (PPCPs), are frequently found in effluent due to limited removal during WWTP processes. Concern has arisen about the environmental fate of PPCPs, especially regarding plant uptake. The aim of this study was to analyze uptake of sulfamethoxazole, trimethoprim, ofloxacin, and carbamazepine in wheat ( L.) plants that were spray-irrigated with WWTP effluent. Wheat was collected before and during harvest, and plants were divided into grain and straw. Subsamples were rinsed with methanol to remove compounds adhering to surfaces. All plant tissues underwent liquid-solid extraction, solid-phase extraction cleanup, and liquid chromatography-tandem mass spectrometry analysis. Residues of each compound were present on most plant surfaces. Ofloxacin was found throughout the plant, with higher concentrations in the straw (10.2 ± 7.05 ng g) and lower concentrations in the grain (2.28 ± 0.89 ng g). Trimethoprim was found only on grain or straw surfaces, whereas carbamazepine and sulfamethoxazole were concentrated within the grain (1.88 ± 2.11 and 0.64 ± 0.37 ng g, respectively). These findings demonstrate that PPCPs can be taken up into wheat plants and adhere to plant surfaces when WWTP effluent is spray-irrigated. The presence of PPCPs within and on the surfaces of plants used as food sources raises the question of potential health risks for humans and animals.

Occurrence of carbamazepine in soils under different land uses receiving wastewater.

Due to its resistance to many wastewater treatment processes, the antiepileptic drug carbamazepine (CBZ) is routinely found in wastewater effluent. Wastewater irrigation is an alternative to stream discharge of wastewater effluent, which utilizes the soil as a tertiary filter to remove excess nutrients and has the potential to remove pharmaceutical compounds. Previous data suggest that CBZ is strongly sorbed to soil; however, it is unknown what its fate is for long periods of irrigation and if land use affects its distribution. Therefore, the objectives of our research were to characterize CBZ concentrations in soils that have been receiving wastewater irrigation for >25 yr under three different land uses: cropped, grassed, and forested. Triplicate soil cores were collected at each of the land uses to a depth of 120 cm. Extractions for CBZ were performed using 5-g soil samples and 20 mL of acetonitrile. The extracted solutions were analyzed on a liquid chromatograph tandem mass spectrometer. The samples were also analyzed for supporting information such as organic carbon, pH, and electrical conductivity. Results suggest that there is accumulation of the CBZ in the surface soils, which have the highest organic carbon content. Average concentrations of CBZ in the surface soils were 4.92, 2.9, and 1.92 ng g, for the forested, grassed, and cropped land uses, respectively. The majority of the CBZ was found in the upper 30 cm of the profile. Our results suggest that the soils adsorb CBZ and slow its movement into groundwater, compared to the movement of nonadsorbed chemicals.

Nitrogen fertilization effects on lesquerella production

Abstract Progress has been made towards the commercialization of Lesquerella fendleri (Gray) Wats. as a fall-planted oilseed crop for the southwestern United States. Research to develop suitable cultural practices for commercial production of lesquerella has been underway since the late 1980s; however, information is limited on the plant’s nitrogen (N) requirement. Field experiments were conducted during two growing seasons to determine the optimum amount and timing of N applications for lesquerella production. Yield results indicate that lesquerella grown on desert soils is strongly influenced by N fertilization. Nitrogen rates as high as 180 kg N ha−1 increased seed yield. Seed oil content decreased as the N rate was increased. The increase in seed yield at the higher N rates generally offsets the decrease in oil content, but oil yields appeared to be near maximum at 180 kg N ha−1. Split-applications of N in the Spring increased seed and oil yields in one of two seasons. Nitrogen had no influence on 1000-seed weight or lesquerolic acid content of the oil. No Spring leaf blade total N level was identified as being related to maximum seed yield. A suggested N management program for lesquerella production is to apply a small portion of N at planting time and the major portion of N in several applications during the period from onset of bloom through full bloom (February–April).

Adsorption of estrogens on laboratory materials and filters during sample preparation.

Despite improvements in analytical techniques for detecting hormones, such as estrogen in environmental samples, there is conflicting information regarding sample filtration before analyses. In addition, there is little information about estrogen adsorption onto other common laboratory materials, including glass, plastic, or stainless steel. Therefore, we have quantified the adsorption of three different types of estrogen (estrone [E1], 17alpha-ethynylestradiol [EE2], and 17beta-estradiol [E2]) onto 11 different types of filters and six other types of materials used for sample storage and laboratory experiments. We observed significant (p < 0.05) differences in the amount of estrogen adsorbed to the different filters. Glass fiber filters adsorbed the lowest amount, whereas nylon filters adsorbed nearly all of the estrogen that contacted them during filtration. Stainless steel and polycarbonate also adsorbed significant amounts of E1, E2, and EE2. The materials with which estrogen comes into contact should be chosen carefully to avoid potential losses due to sorption.

Evapotranspiration estimates derived from subsoil salinity data

Abstract A method is described for estimating past evapotranspiration (ET) rates from irrigated fields. It is based on the assumption that salt concentrations below the crop root zone are a function of the flux of naturally occurring salts applied by irrigation at the soil surface and the rate of soil water depletion due to ET. Thus, if irrigation histories and subsoil salinity data are available, ET rates may be calculated. For irrigated fields with low leaching fractions, corrections to the ET estimates may be necessary due to chemical precipitation. This is done through modeling of solution chemistry or from the use of observed chloride concentrations in solution. ET estimates for 1976–1980 for cotton at Safford, Arizona were made from subsoil salinity data collected to 3 m in April 1983. The average seasonal ET was found to be 1.04 m, which was only 2% below the average seasonal ET estimated by the modified Blaney-Criddle method. The estimated ET for cotton was on average 0.48 of the seasonal pan evaporation and 0.76 of the annual irrigation plus rain-fall amount. The method appears to be suitable for use in selected semi-arid and arid areas which have relatively uniform soils and deep water tables.

Comparison of equilibrium and non-equilibrium distribution coefficients for the human drug carbamazepine in soil

The distribution coefficient (KD) for the human drug carbamazepine was measured using a non-equilibrium technique. Repacked soil columns were prepared using an Airport silt loam (Typic Natrustalf) with an average organic matter content of 2.45%. Carbamazepine solutions were then leached through the columns at 0.5, 1.0 and 1.5 mL min(-1) representing average linear velocities of 1.8, 3.5 and 5.3 cm h(-1) respectively. Each flow rate was replicated three times and three carbamazepine pulses were applied to each column resulting in a total of 9 columns with 27 total carbamazepine pulses. Breakthrough curves were used to determine KD using the parameter fitting software CXTFIT. Results indicate that as flow rate decreased from 5.3 to 1.8 cm h(-1), KD increased an average of 21%. Additionally, KD determined by column leaching (14.7-22.7 L kg(-1)) was greater than KD determined by a 2h batch equilibrium adsorption (12.6 L kg(-1)). Based on these KDs carbamazepine would be generally characterized as non-mobile in the soil investigated. However, repeated carbamazepine applications resulted in an average 22% decrease in KD between the first and third applications. Decreasing KD is attributed to differences in sorption site kinetics and carbamazepine residence time in contact with the soil. This would indicate that the repeated use of reclaimed wastewater at high application rates for long-term irrigation or groundwater recharge has the potential to lead to greater transport of carbamazepine than KD determined by batch equilibrium would predict.

Sorption/Desorption of lincomycin from three arid-region soils.

The antibiotic lincomycin is commonly found in treated municipal waste water and in waste from swine and poultry production. Environmental disposal of these wastes has the potential to introduce a significant mass of lincomycin into the ecosystem. In the present study, a series of sorption and desorption experiments were conducted to determine the potential mobility of lincomycin in soils from arid environments. Sorption and desorption isotherms were obtained for lincomycin using three different soils. Isotherms were fit to the Freundlich equation. Adsorption of lincomycin was found to have a of 11.98 for a biosolid-treated soil (1.58% OC) and a of 210.15 for a similar unamended soil (1.42% OC). It was also found that for a low-organic-content soil the was 5.09. The differences in adsorption can be related to the soil pH and the pKa of lincomycin (7.5-7.8). When the soil solution pH is below the pKa, the cationic species of lincomycin dominates, resulting in increased water solubility. Interaction with the cation exchange complex is minimal due to a high solution cation concentration (Ca and Na). Desorption isotherms also indicate that when the solution pH is lower than the pKa, retention of lincomycin is reduced. Our results indicate that the mobility of lincomycin in these arid region soils is dependent on soil pH.

Nitrogen fertilization effects on jojoba seed production

Abstract Although jojoba (Simmondsia chinensis (Link) C. Schneider) has been cultivated in the United States for many years, information is limited on the plants nitrogen (N) requirement. A 10-year field study, which began with 2-year-old plants, evaluated the effect of N application rates on growth, flower bud survival, seed yield, seed weight, seed wax content and leaf blade total N content of three clones. Nitrogen rates were 0, 30 and 60 kg N per ha per year for the first 4 years and then were increased to 0, 60 and 120 kg N per ha per year for the remaining 6 years of the study. Nitrogen rates had a significant effect on growth in height in only 1 year. Growth was generally less in years when high seed yields were produced. Seed yields were increased linearly by N rate in 4 of the 7 years that crops were produced. Nitrogen rate had no effect on flower bud survival. Highest bud survival followed winters with temperatures no lower than −3°C and little or no survival occurred when temperatures reached −6 or −7°C. Seed weight was increased by N in 3 of the 7 years. A negative linear relationship existed between seed yield and seed weight. In 5 of the 7 years, seed wax content was reduced as the N rate was increased. Seed yields of clones varied among years, but AT-1310 had the highest seed wax content in 4 of the 7 years. Leaf blade total N content generally increased linearly as the N rate was increased after the first 3 years of the study. Based on leaf N content and seed yields obtained over a 7-year period, it appears that a leaf N content lower than 2% from July through September is associated with reduced seed yield in the following crop year.