Although regulatory agencies require adsorption and soil mobility data prior to registering pesticides, such data are not necessarily adequate to accurately predict the environmental fate or mobility of any particular chemical. The unexpected detection of hydrophobic pesticides in remote ecosystems and ground waters, compounds deemed immobile based on their partition coeffi cients, is indicative of an incomplete understanding of pesticide adsorption and desorption processes in natural environments (McCall et al. 1980; Corsolini et al. 2002; Montone et al. 2005) . One key element needed to fill this knowledge gap, in addition to continued basic research, is to comprehensively synthesize existing research findings pertinent to the adsorption and desorption of pesticides. Therefore, we have analyzed an extensive number of peer-reviewed journal articles, and herewith present a critical examination of the environmental presence, adsorption, and desorption of chlorpyrifos (CPF), one of the most widely used organophosphorus pesticides worldwide. This review complements past reviews that have addressed the environmental fate and ecotoxicology of CPF (Racke 1993; Barron and Woodburn 1995; Giesy et al. 1999), and the general process of soil adsorption for multiple pesticides (Delle Site 2001 ; Wauchope et al. 2002 ) . We fi rst review the environmental presence of CPF and then address CPF adsorption data for a range of solid matrices, including soils, sediments, organic matter, and minerals. Our review was performed using the framework of the common methods employed to quantify pesticide adsorption: batch equilibrium, chromatography, and use of ancillary pesticide characteristics such as water solubility, the octanol–water partition coefficient, and topological structure. Thereafter, we address peer-reviewed data that documents CPF desorption, a key process that affects the long-term fate and impact of CPF in the environment, but has heretofore been inadequately addressed. We conclude the review by providing key recommendations for future research. 

This article describes the outreach experience of a graduate fellow who participated in Washington State University’s efforts to promote interest in engineering and sustainability by underrepresented high school students. The fellow mentored students from a rural high school as they developed projects related to sustainable energy for the university’s 2008 Imagine Tomorrow competition. Outreach strategies focused on fostering student ownership, using formative assessment, and promoting student preparation. In contrast to other winning high schools, the study high school exhibited low academic achievement and high ethnic diversity. Yet, the high school won the grand prize. Inspired, the school has competed in and won an award in every Imagine Tomorrow competition since 2008 with teams including American Indian students, a target of future outreach efforts. The experience shows that outreach to appropriate schools, in combination with university-sponsored technology competitions, can promote underrepresented student participation in engineering.

Hypolimnetic oxygenation, the engineered addition of oxygen gas to the bottom of lakes and reservoirs, can improve water quality by repressing the accumulation of nutrients, metals, and toxic compounds in bottom waters. This study designed and tested an oxygenation system in Lake Bard, California. Hypolimnetic oxygen demand, a key design parameter, was estimated through the combination of sediment–water chamber incubations and numerical analysis of water column dissolved oxygen (DO) profiles. Chamber incubations showed that increased water velocity near the sediment–water interface substantially increased the rate of sediment oxygen uptake, and this observation was incorporated into system sizing. The chamber study also confirmed that maintenance of oxygenated conditions repressed sediment release of phosphate, ammonia, manganese, and sulfide. Phosphorus and manganese release rates were 6–8 mg/m2/d and 2–5 mg/m2/d under anoxic conditions, respectively, but negligible or negative under oxic conditions. The novel hypolimnetic oxygenation system used a waste product, oxygen-rich off-gas from an ozone contactor at a nearby water treatment plant, to sustainably improve source water quality. The system was tested over a 2 week period in June 2004. Oxygen addition averaged 380 kg/d and increased bottom water DO from 1–2 to 5–6 mg/L with a concurrent drop in water column phosphate and iron, and a delay in sediment release of ammonia. Manganese, with its slow oxidation kinetics, remained in bottom waters during the oxygenation test, indicating that the oxygenation system needs to be turned on earlier in the season to better control manganese accumulation in bottom waters.

Constructed treatment wetlands (CTWs) are unique ecotechnologies that can sustainably treat a range of wastewaters. This study focused on a 0.23 ha vegetated surface-flow CTW polishing nitrate-rich (3–6 mg-N/L) tertiary effluent from a municipal wastewater treatment plant. Water quality was monitored longitudinally in the fall of 2009 and 2010. The CTW cooled water by from around 20 W C to <15 W C in both years. Longitudinal temperature profiles were successfully modeled using an energy balance approach (2009 R2 0.69; 2010 R2 0.92). The magnitude of key model fitting parameters, including albedo (0.1–0.2) and convective transfer coefficient (0.1–0.9 MJ/m2-d-W-C), were within ranges reported in the literature. In both years, dissolved oxygen decreased through the wetland from 6–7 mg/L to 3–4 mg/L, yielding an oxygen mass consumption rate of 0.08–0.09 g/m2-d. Longitudinal nitrate profiles were well represented by the P-k-C* model (2009 R2 0.88; 2010 R2 0.92). First order removal rates were 20.2 m/yr in 2009 and 29.0 m/yr in 2010 at a P value of 6.0. Levels of ammonia and total phosphorus increased negligibly through the wetland, remaining below 0.25 mg/L. This study shows that vegetated surface-flow CTWs are well suited to cool and polish low-BOD nitrate-dominated tertiary effluents with little degradation of other water quality parameters of concern, including phosphorus and ammonia.

The effects of glucose on enhanced biological phosphorus removal (EBPR) activated sludge enriched with acetate was investigated using sequencing batch reactors. A glucose/acetate mixture was serially added to the test reactor in ratios of 25/75%, 50/50%, and 75/25% and the EBPR activity was compared to the control reactor fed with 100% acetate. P removal increased at a statistically significant level to a near-complete in the test reactor when the mixture increased to 50/50%. However, EBPR deteriorated when the glucose/acetate mixture increased to 75/25% in the test reactor and when the control reactor abruptly switched to 100% glucose. These results, in contrast to the EBPR conventional wisdom, suggest that the addition of glucose at moderate levels in wastewaters does not impede and may enhance EBPR, and that glucose waste products should be explored as an economical sustainable alternative when COD enhancement of EBPR is needed.

Since the mid-20th century, oxygen status at the sediment–water interface (SWI) has been implicated in regulating lake internal phosphorus loading. In deeper lakes, summer hypolimnetic oxygen depletion may thus play a critical role in phosphorus cycling and lake trophic status. Hypolimnetic aeration (HA) has been utilized for more than 4 decades to prevent development of anoxia, decrease internal phosphorus load, and enhance fisheries. Most recently, interest has shifted to hypolimnetic oxygenation (HO) for potential performance and economic advantages. In Newman Lake, hypolimnetic oxygenation was initiated in 1992 when the first lake application of downflow contact bubble oxygenation (Speece Cone technology) was installed. Oxygenation at Newman has reduced growing season Nurnberg Anoxic Factors (AF) from a range of about 30–60 d to ¨ <10 d. We propose that differences in predicted versus observed AF based on phosphorus may be utilized to assess lake restoration performance. Newman Lake has demonstrated the importance of operating the system at full capacity, as lower oxygen delivery rates do not produce proportional hypolimnetic oxygen concentrations, as well as other insights into HO system sizing and design.

At environmentally relevant concentrations in soils and sediments, chlorpyrifos, a hydrophobic organic insecticide, showed strong adsorption that correlated significantly with organic matter content. Chlorpyrifos desorption followed a nonsingular falling desorption isotherm that was estimated using a memorydependent mathematical model. Desorption of chlorpyrifos was biphasic in nature, with a labile and nonlabile component. The labile component comprised 1828% of the original solid-phase concentration, and the residue was predicted to slowly partition to the aqueous phase, implying long-term desorption from contaminated soils or sediments. The newly proposed mechanism to explain sorption/desorption hysteresis and biphasic desorption is the unfavorable thermodynamic energy landscape arising from limitation of diffusivity of water molecules through the strongly hydrophobic domain of soils and sediments. Modeling results suggest that contaminated soils and sediments could be secondary long-term sources of pollution. Long-term desorption may explain the detection of chlorpyrifos and other hydrophobic organic compounds in aquatic systems far from application sites, an observation that contradicts conventional transport predictions.

Enhanced biological phosphorus removal (EBPR) is a well-established technology for removing phosphorus from wastewater. However, the process remains operationally unstable in many systems, primarily because there is a lack of understanding regarding the microbiology of EBPR. This paper presents a review of advances made in the study of EBPR microbiology and focuses on the identification, enrichment, classification, morphology, and metabolic capacity of polyphosphate- and glycogen-accumulating organisms. The paper also highlights knowledge gaps and research challenges in the field of EBPR microbiology. Based on the review, the following recommendations regarding the future direction of EBPR microbial research were developed: (1) shifting from a reductionist approach to a more holistic system-based approach, (2) using a combination of culture-dependent and cultureindependent techniques in characterizing microbial composition, (3) integrating ecological principles into system design to enhance stability, and (4) reexamining current theoretical explanations of why and how EBPR occurs.

Addition of oxygen to surface-flow wetland mesocosms treating synthetic secondary effluent resulted in a significant increase in ammonia oxidation potential in sediment compared to non-oxygenated controls. Ammonia oxidation potential in oxygenated wetland sediment (1.2–3.5 mg N g dw-1 d-1) was 2–3 orders of magnitude higher than those measured in sediment and soil systems reported in the literature. Phylogenic analysis of sediment from the two treatments revealed substantial differences in microbial diversity including the presence of ammonia-oxidizing bacteria (Nitrosomonas oligotropha) and denitrifying bacteria only in oxygenated sediment, and an increase in the diversity of aerobic phototrophs and methanotrophs in control sediment. These observations supported the contention by Palmer et al. (2009) that oxygenation ‘activated’ nitrifying bacteria in wetland sediment leading to high rates of biological ammonia oxidation.

Paso Bonito Reservoir (mean depth = 6.5 m; volume = 8.0 × 10^6 m3) is a small raw water reservoir in south-central Cuba. This study evaluated sources of high levels of manganese in the reservoir causing taste and odor problems. Watershed monitoring showed that levels of total manganese (Mn) and total iron (Fe) were high (Mn 0.14–0.64 mg/L; Fe 5.3–12.4 mg/L) during the first flood of the wet season in river sampling stations near historical pyrite mining operations. Monitoring in the reservoir showed that Mn and Fe were present in bottom waters throughout the year, with peak levels (>8 mg/L of Mn and >30 mg/L of Fe) coinciding with low levels of oxygen in summer months. Empirical modeling of Mn concentration in the reservoir water column showed that it correlated significantly with Fe (positive correlation), redox potential (negative correlation) and dissolved oxygen (negative correlation). Statistical evaluation of the temporal cycle of Mn in raw water delivered to the Juan Gonzales Water Treatment Plant showed that Mn accumulation was highly seasonal, peaking annually around September when dissolved oxygen in raw water was at a minimum. Data suggest that during first-flood conditions early in the wet season, mass loading of Mn and Fe from the watershed to the reservoir is high. During the subsequent drier low-flow summer period, external mass loading of metals drops dramatically and the reservoir becomes a large exporter of Mn and Fe as the metals are internally recycled under anaerobic conditions in bottom waters.