Modeling the fate of ionizable pharmaceutical and personal care products (iPPCPs) in soil-plant systems: pH and speciation.

A model was developed to simulate the pH-dependent speciation and fate of ionizable pharmaceutical and personal care products (iPPCPs) in soils and their plant uptake during thedt application of reclaimed wastewater to agricultural soils. The simulation showed that pH plays an important role in regulating the plant uptake of iPPCPs, i.e., ibuprofen (IBU; with a carboxylic group), triclosan (TCS; phenolic group), and fluoxetine (FXT; amine group) as model compounds. It took 89-487 days for various iPPCPs to reach the steady-state concentrations in soil and plant tissues. The simulated steady-state concentrations of iPPCPs in plant tissues at pH 9 is 2.2-2.3, 2.5-2.6, and 1.07-1.08 times that at pH 5 for IBU, TCS, and FXT, respectively. Assuming sorption only for neutral compounds led to miscalculation of iPPCPs concentrations in plant tissues by up to one and half orders magnitude. Efflux of compounds in soil, lettuce leaf, and soybean pods was primarily contributed by their degradation in soil and dilution due to plant tissue growth. Overall, the results demonstrated the importance of considering pH and speciation of iPPCPs when simulating their fate in the soil-plant system and plant uptake.

Modeling the fate and human health impacts of pharmaceuticals and personal care products in reclaimed wastewater irrigation for agriculture.

Wastewater reclamation and reuse for agriculture have attracted a great deal of interest, due to water stress caused by rapid increase in human population and agricultural water demand as well as climate change. However, the application of treated wastewater for irrigation can lead to the accumulation of pharmaceuticals and personal care products (PPCPs) in the agricultural crops, grazing animals, and consequently to human dietary exposure. In this study, a model was developed to simulate the fate of five PPCPs; triclosan (TCS), carbamazepine (CBZ), naproxen (NPX), gemfibrozil (GFB), and fluoxetine (FXT) during wastewater reuse for agriculture, and potential human dietary exposure and health risk. In a reclaimed wastewater-irrigated grazing farm growing alfalfa, it took 100-535 days for PPCPs to achieve the steady-state concentrations of 1.43 × 10-6, 4.73 × 10-5, 1.17 × 10-6, 1.53 × 10-5, and 7.38 × 10-6 mg/kg for TCS, CBZ, NPX, GFB, and FXT in soils, respectively. The accumulated concentration of PPCPs in the plant (alfalfa) and grazing animals (beef) ranged 2.86 × 10-7- 4.02 × 10-3 and 4.39 × 10-15- 6.27 × 10-7 mg/kg, respectively. Human dietary exposure to these compounds through beef consumption was calculated to be 1.67 × 10-18- 1.74 × 10-10 mg/kg bodyweight/d, much lower than the acceptable daily intake (ADI). Similar results were obtained for a 'typical' reclaimed wastewater irrigated farm based on the typical setup using our model. Screening analysis showed that PPCPs with relatively high LogD value and lower ratios of degradation rate (in soils) to plant uptake have a greater potential to be transferred to humans and cause potential health risks. We established a modeling method for evaluating the fate and human health effects of PPCPs in reclaimed wastewater reuse for the agricultural system and developed an index for screening PPCPs with high potential to accumulate in agricultural products. The model and findings are valuable for managing water reuse for irrigation and mitigating the harmful effects of PPCPs.

How specialized is a soil specialist? Early life history responses of a rare Eriogonum to site-level variation in volcanic soils.

PREMISE: Understanding edaphic specialization is crucial for conserving rare plants that may need relocation due to habitat loss. Focusing on Eriogonum crosbyae, a rare soil specialist in the Great Basin of the United States, we asked how site-level variation among volcanic soil outcrops affected plant growth and population distribution. METHODS: We measured emergence, survival, size, and biomass allocation of E. crosbyae seedlings planted in soils collected from 42 outcrops of actual and potential habitat. We also measured phenotypic variation in the wild, documented abiotic and biotic components of E. crosbyae habitat, re-surveyed Nevada populations, and evaluated occupancy changes over time. RESULTS: Plants responded plastically to edaphic variation, growing larger and allocating relatively more to aboveground tissues in soils with greater nutrient availability and growing smaller in soils higher in copper in the field and the greenhouse. However, the chemical and physical soil properties we measured did not predict site occupancy, nor was plant phenotype in the greenhouse different when plants were grown in soils from sites with different occupation status. We observed occupation status reversals at five locations. CONCLUSIONS: Eriogonum crosbyae performed well in soils formed on hydrothermally altered rocks that are inhospitable to many other plants. Extirpation/colonization events observed were consistent with metapopulation dynamics, which may partially explain the patchy distribution of E. crosbyae among outcrops of potential habitat. While soil properties did not predict site occupancy, early life stages showed sensitivity to soil variation, indicating that seedling dynamics may be important to consider for the conservation of this soil specialist.

Trace organic contaminants in field-scale cultivated alfalfa, soil, and pore water after 10 years of irrigation with reclaimed wastewater.

Several studies have assessed the presence of trace organic contaminants (TrOCs) in reclaimed wastewater and their uptake into crops but there are limited data from field-scale studies. In this research, we studied the fate of 12 TrOCs in wastewater samples, 11 in plants and in soil pore water, and 10 in soil at an agricultural research farm, which was irrigated with reclaimed wastewater for more than 10 years. First, we examined the presence of the compounds in the primary, secondary, and treated effluent of a regional water reclamation facility which provides the irrigation water. The agricultural field produced alfalfa, and we measured the contaminants in the alfalfa, soil, and pore water. Reclaimed wastewater contained 11 of 12 TrOCs, with concentrations ranging from 26 ± 9 ng/L (DEET) to 1539 ± 1899 ng/L (trimethoprim). Atrazine was not detected. Pore water collected during non-irrigating periods contained all analyzed TrOCs, from 3 ± 0.1 ng/L (diphenhydramine) to 343 ± 360 ng/L (primidone). TrOCs measured in pore water samples indicated that they may leach to shallow groundwater even when fields are not being irrigated. Soils from 0 to 60 cm contained nine TrOCs from below the reporting limit (fluoxetine) to 329 ng/g (carbamazepine). Atrazine was not detected. TrOC concentrations decreased with increasing soil depth, except carbamazepine, which was more recalcitrant. Nine TrOCs were present in the shoots and leaves of alfalfa grown in the reclaimed wastewater irrigated plots, at concentrations ranging from <1 ng/g (diphenhydramine and fluoxetine) to 49 ng/g dry weight (carbamazepine). Atrazine and caffeine were not detected. We estimated that a maximum of 14% of DEET from the reclaimed wastewater was accumulated in alfalfa. Overall, despite some accumulation of TrOCs in the soil, alfalfa uptake was limited, which results in low exposure to foraging animals.

Reclaimed wastewater as a viable water source for agricultural irrigation: A review of food crop growth inhibition and promotion in the context of environmental change.

The geographical and temporal distribution of precipitation has and is continuing to change with changing climate. Shifting precipitation will likely require adaptations to irrigation strategies, and because 35% of rainfed and 60% of irrigated agriculture is within 20 km of a wastewater treatment plant, we expect that the use of treated wastewater (e.g., reclaimed wastewater) for irrigation will increase. Treated wastewater contains various organic and inorganic substances that may have beneficial (e.g., nitrate) or deleterious (e.g., salt) effects on plants, which may cause a change in global food productivity should a large change to treated wastewater irrigation occur. We reviewed literature focused on food crop growth inhibition or promotion resulting from exposure to xenobiotics, engineered nanoparticles, nitrogen, and phosphorus, metals, and salts. Xenobiotics and engineered nanoparticles, in nearly all instances, were detrimental to crop growth, but only at concentrations much greater than would be currently expected in treated wastewater. However, future changes in wastewater flow and use of these compounds and particles may result in phytotoxicity, particularly for xenobiotics, as some are present in wastewater at concentrations within approximately an order of magnitude of concentrations which caused growth inhibition. The availability of nutrients present in treated wastewater provided the greatest overall benefit, but may be surpassed by the detrimental impact of salt in scenarios where either high concentrations of salt are directly deleterious to plant development (rare) or in scenarios where soils are poorly managed, resulting in soil salt accumulation.

Aerobic respiration of mineral-bound organic carbon in a soil.

Associations with minerals can potentially augment soil organic carbon (SOC) stability by reducing the bioavailability and degradation of SOC. However, few studies have directly measured aerobic respiration of mineral-bound SOC. In this study, we investigated the microbial aerobic respiration and bioavailability of ferrihydrite-sorbed glucose (Fh-GLU) and ferrihydrite-sorbed formic acid (Fh-FA) by adding 13C-labeled compounds to a soil. During an 11-day incubation, 30.2% of free, non-Fh-sorbed glucose (GLU) and 61.8% of free formic acid (FA) were respired, whereas 4.2% and 27.9% of Fh-GLU and Fh-FA were respired, respectively. Our results demonstrated that Fh-bound GLU/FA had lower bioavailability compared to free organic compounds. Associations with Fh led to greater inhibition in the bioavailability of GLU than that for FA. The priming effects of added compounds on the respiration of native SOC were decreased by their association with Fh. Our results demonstrated that the bioavailability and priming effect of organic compounds depend on their interactions with minerals.

Microbial Transformation of Multiwalled Carbon Nanotubes by Mycobacterium vanbaalenii PYR-1.

Carbonaceous nanomaterials are widely used in industry and consumer products, but concerns have been raised regarding their release into the environment and subsequent impacts on ecosystems and human health. Although many efforts have been devoted to understanding the environmental fate of carbonaceous nanomaterials, information about their microbial transformation is still rare. In this study, we found that within 1 month a polycyclic aromatic hydrocarbon-degrading bacterium, Mycobacterium vanbaalenii PYR-1, was able to degrade both pristine and carboxyl-functionalized multiwalled carbon nanotubes (p-MWCNT and c-MWCNT), as demonstrated by consistent results from high resolution transmission electron microscopy, Raman spectroscopy, and confocal Raman microspectroscopy. Statistical analysis of Raman spectra identified a significant increase in the density of disordered or amorphous carbon in p-MWCNT and c-MWCNT after biodegradation. Microbial respiration further suggested potential mineralization of MWCNTs within about 1 month. All of our analyses consistently showed higher degradation or mineralization of c-MWCNT compared to p-MWCNT. These results highlight the potential of using bacteria in engineered systems to remove residual carbonaceous nanomaterials and reduce risk of human exposure and environmental impact. Meanwhile, our finding suggests possible transformation of carbonaceous nanomaterials by polycyclic aromatic hydrocarbon-degrading bacteria in the natural environment, which should be accounted for in predicting the environmental fate of these emerging contaminants and in nanotechnology risk regulation.

Plant species effects on soil nutrients and chemistry in arid ecological zones.

The presence of vegetation strongly influences ecosystem function by controlling the distribution and transformation of nutrients across the landscape. The magnitude of vegetation effects on soil chemistry is largely dependent on the plant species and the background soil chemical properties of the site, but has not been well quantified along vegetation transects in the Great Basin. We studied the effects of plant canopy cover on soil chemistry within five different ecological zones, subalpine, montane, pinyon-juniper, sage/Mojave transition, and desert shrub, in the Great Basin of Nevada all with similar underlying geology. Although plant species differed in their effects on soil chemistry, the desert shrubs Sarcobatus vermiculatus, Atriplex spp., Coleogyne ramosissima, and Larrea tridentata typically exerted the most influence on soil chemistry, especially amounts of K(+) and total nitrogen, beneath their canopies. However, the extent to which vegetation affected soil nutrient status in any given location was not only highly dependent on the species present, and presumably the nutrient requirements and cycling patterns of the plant species, but also on the background soil characteristics (e.g., parent material, weathering rates, leaching) where plant species occurred. The results of this study indicate that the presence or absence of a plant species, especially desert shrubs, could significantly alter soil chemistry and subsequently ecosystem biogeochemistry and function.

Do increased summer precipitation and N deposition alter fine root dynamics in a Mojave Desert ecosystem?

Climate change is expected to impact the amount and distribution of precipitation in the arid southwestern United States. In addition, nitrogen (N) deposition is increasing in these regions due to increased urbanization. Responses of belowground plant activity to increases in soil water content and N have shown inconsistent patterns between biomes. In arid lands, plant productivity is limited by water and N availability so it is expected that changes in these factors will affect fine root dynamics. The objectives of this study were to quantify the effects of increased summer precipitation and N deposition on fine root dynamics in a Mojave Desert ecosystem during a 2-year field experiment using minirhizotron measurements. Root length density, production, and mortality were measured in field plots in the Mojave Desert receiving three 25 mm summer rain events and/or 40 kg N ha(-1)  yr(-1) . Increased summer precipitation and N additions did not have an overall significant effect on any of the measured root parameters. However, differences in winter precipitation resulting from interannual variability in rainfall appeared to affect root parameters with root production and turnover increasing following a wet winter most likely due to stimulation of annual grasses. In addition, roots were distributed more deeply in the soil following the wet winter. Root length density was initially higher under canopies compared to canopy interspaces, but converged toward the end of the study. In addition, roots tended to be distributed more deeply into the soil in canopy interspace areas. Results from this study indicated that increased summer precipitation and N deposition in response to climate change and urbanization are not likely to affect fine root dynamics in these Mojave Desert ecosystems, despite studies showing aboveground plant physiological responses to these environmental perturbations. However, changes in the amount and possibly distribution of winter precipitation may affect fine root dynamics.

Concurrent and lagged impacts of an anomalously warm year on autotrophic and heterotrophic components of soil respiration: a deconvolution analysis.

*Partitioning soil respiration into autotrophic (R(A)) and heterotrophic (R(H)) components is critical for understanding their differential responses to climate warming. *Here, we used a deconvolution analysis to partition soil respiration in a pulse warming experiment. We first conducted a sensitivity analysis to determine which parameters can be identified by soil respiration data. A Markov chain Monte Carlo technique was then used to optimize those identifiable parameters in a terrestrial ecosystem model. Finally, the optimized parameters were employed to quantify R(A) and R(H) in a forward analysis. *Our results displayed that more than one-half of parameters were constrained by daily soil respiration data. The optimized model simulation showed that warming stimulated R(H) and had little effect on R(A) in the first 2 months, but decreased both R(H) and R(A) during the remainder of the treatment and post-treatment years. Clipping of above-ground biomass stimulated the warming effect on R(H) but not on R(A). Overall, warming decreased R(A) and R(H) significantly, by 28.9% and 24.9%, respectively, during the treatment year and by 27.3% and 33.3%, respectively, during the post-treatment year, largely as a result of decreased canopy greenness and biomass. *Lagged effects of climate anomalies on soil respiration and its components are important in assessing terrestrial carbon cycle feedbacks to climate warming.

Prolonged suppression of ecosystem carbon dioxide uptake after an anomalously warm year.

Terrestrial ecosystems control carbon dioxide fluxes to and from the atmosphere through photosynthesis and respiration, a balance between net primary productivity and heterotrophic respiration, that determines whether an ecosystem is sequestering carbon or releasing it to the atmosphere. Global and site-specific data sets have demonstrated that climate and climate variability influence biogeochemical processes that determine net ecosystem carbon dioxide exchange (NEE) at multiple timescales. Experimental data necessary to quantify impacts of a single climate variable, such as temperature anomalies, on NEE and carbon sequestration of ecosystems at interannual timescales have been lacking. This derives from an inability of field studies to avoid the confounding effects of natural intra-annual and interannual variability in temperature and precipitation. Here we present results from a four-year study using replicate 12,000-kg intact tallgrass prairie monoliths located in four 184-m(3) enclosed lysimeters. We exposed 6 of 12 monoliths to an anomalously warm year in the second year of the study and continuously quantified rates of ecosystem processes, including NEE. We find that warming decreases NEE in both the extreme year and the following year by inducing drought that suppresses net primary productivity in the extreme year and by stimulating heterotrophic respiration of soil biota in the subsequent year. Our data indicate that two years are required for NEE in the previously warmed experimental ecosystems to recover to levels measured in the control ecosystems. This time lag caused net ecosystem carbon sequestration in previously warmed ecosystems to be decreased threefold over the study period, compared with control ecosystems. Our findings suggest that more frequent anomalously warm years, a possible consequence of increasing anthropogenic carbon dioxide levels, may lead to a sustained decrease in carbon dioxide uptake by terrestrial ecosystems.

Atmospheric mercury exchange with a tallgrass prairie ecosystem housed in mesocosms.

This study focused on characterizing air-surface mercury Hg exchange for individual surfaces (soil, litter-covered soil and plant shoots) and ecosystem-level flux associated with tallgrass prairie ecosystems housed inside large mesocosms over three years. The major objectives of this project were to determine if individual surface fluxes could be combined to predict ecosystem-level exchange and if this low-Hg containing ecosystem was a net source or sink for atmospheric Hg. Data collected in the field were used to validate fluxes obtained in the mesocosm setting. Because of the controlled experimental design and ease of access to the mesocosms, data collected allowed for assessment of factors controlling flux and comparison of models developed for soil Hg flux versus environmental conditions at different temporal resolution (hourly, daily and monthly). Evaluation of hourly data showed that relationships between soil Hg flux and environmental conditions changed over time, and that there were interactions between parameters controlling exchange. Data analyses demonstrated that to estimate soil flux over broad temporal scales (e.g. annual flux) coarse-resolution data (monthly averages) are needed. Plant foliage was a sink for atmospheric Hg with uptake influenced by plant functional type and age. Individual system component fluxes (bare soil and plant) could not be directly combined to predict the measured whole system flux (soil, litter and plant). Emissions of Hg from vegetated and litter-covered soil were lower than fluxes from adjacent bare soil and the difference between the two was seasonally dependent and greatest when canopy coverage was greatest. Thus, an index of plant canopy development (canopy greenness) was used to model Hg flux from vegetated soil. Accounting for ecosystem Hg inputs (precipitation, direct plant uptake of atmospheric Hg) and modeled net exchange between litter-and-plant covered soils, the tallgrass prairie was found to be a net annual sink of atmospheric Hg.

Divergence of reproductive phenology under climate warming.

Because the flowering and fruiting phenology of plants is sensitive to environmental cues such as temperature and moisture, climate change is likely to alter community-level patterns of reproductive phenology. Here we report a previously unreported phenomenon: experimental warming advanced flowering and fruiting phenology for species that began to flower before the peak of summer heat but delayed reproduction in species that started flowering after the peak temperature in a tallgrass prairie in North America. The warming-induced divergence of flowering and fruiting toward the two ends of the growing season resulted in a gap in the staggered progression of flowering and fruiting in the community during the middle of the season. A double precipitation treatment did not significantly affect flowering and fruiting phenology. Variation among species in the direction and magnitude of their response to warming caused compression and expansion of the reproductive periods of different species, changed the amount of overlap between the reproductive phases, and created possibilities for an altered selective environment to reshape communities in a future warmed world.