Nitrogen release and plant available nitrogen of composted and un-composted biosolids.

The nitrogen (N) release from composted and un-composted biosolids and plant available N (PAN) of the biosolids were quantified to evaluate if composting can contribute to stabilize biosolids N and reduce the nitrate ( NO 3 - ) leaching potential in biosolids-amended soil. Biosolids were composted at >55°C for 21 days after mixing the biosolids with yard waste at 1:1 (w/w) ratio. In the N release study, we installed field lysimeters filled with soil (sand and clay) amended with composted and un-composted biosolids at two rates (30 and 150 dry Mg/ha) and measured the inorganic N in leachate after each rainfall and soil inorganic N monthly. The N released from composted biosolids during the two-year study period were lower (6% of organic N added for clay and 11% for sandy loam soil) as compared to un-composted biosolids (14% of organic N added for clay and 21% for sandy soils). Composted biosolids showed a lower N release rate constant k value of 0.0014 and 0.0027 month-1 for clay and sandy soil, respectively, compared to corresponding values of 0.0035 and 0.0068 month-1 for un-composted biosolids. We used greenhouse bioassay with corn (Zea mays), ryegrass (Lolium perenne), and Miscanthus (Miscanthus giganteus) as test plants grown for six months with reference to N chemical fertilizer ranging from 0, 75, 150 to 300 kg N/ha to evaluate the PAN of the biosolids. Based on our study, plant growth was not affected by using either composted or un-composted biosolids but the PAN was lower in composted biosolids (4.0%-5.9%) than un-composted biosolids (11.4%-13.6%). Composting results in higher N-retention efficiency in biosolids and composted biosolids are a valuable source of N to support the plant growth with lower N released to the environment. Thus, the potential of N leaching would still be low in the situations where a high rate of biosolids needs to be applied for land reclamation or landscaping soil reconstruction. PRACTITIONER POINTS: Composting enhances N-retention efficiency in biosolids and composted biosolids are a valuable source of N to support the plant growth with lower N released to the environment. Potential of N leaching would still be low in the situations where a high rate of biosolids needs to be applied for land reclamation or landscaping soil reconstruction. N released from composted and un-composted biosolids can be adequately described by first-order kinetic model.

A reduction in triclosan and triclocarban in water resource recovery facilities' influent, effluent, and biosolids following the U.S. Food and Drug Administration's 2013 proposed rulemaking on antibacterial products.

Pharmaceutical and personal care product compounds (PPCPs) comprise a large and diverse group of chemical compounds, including prescription and over-the-counter drugs and cleaning agents. Although PPCPs in the effluent and biosolids of water resource recovery facilities (WRRFs) are currently not regulated, public interest has led the Metropolitan Water Reclamation District of Greater Chicago to monitor for 11 PPCPs in the influent, effluent, and biosolids at its seven WRRFs. In 2016, the U.S. Food and Drug Administration (FDA) issued a final rule establishing that 19 specific ingredients, including triclosan and triclocarban, were no longer generally recognized as safe and effective, which prohibits companies from marketing soaps as antibacterial if they contain one or more of these ingredients. It was presumed that since the proposed rulemaking in 2013, manufacturers began to remove these active ingredients from their products. Annual monitoring of 11 PPCPs from 2012 to 2017 demonstrated a 71% decrease in triclosan and 72% decrease in triclocarban in per capita influent loading into seven WRRFs. There was a 70% decrease in triclosan and 80% decrease in triclocarban concentrations in biosolids. These declines suggest the FDA rule for the reduction in use of these compounds was effective and resulted in manufacturers removing these ingredients from their products. PRACTITIONER POINTS: Reduction in triclosan and triclocarban per capita influent loading observed from 2012 to 2017. Reduction in triclosan and triclocarban biosolids loading observed from 2012 to 2017. 2016 FDA rulemaking on antimicrobial soaps was effective in removing triclosan and triclocarban from these products. Positive impact on quality of biosolids land applied to farmland.

Soil in the City: Sustainably Improving Urban Soils.

Large tracts of abandoned urban land, resulting from the deindustrialization of metropolitan areas, are generating a renewed interest among city planners and community organizations envisioning the productive use of this land not only to produce fresh food but to effectively manage stormwater and mitigate the impact of urban heat islands. Healthy and productive soils are paramount to meet these objectives. However, these urban lands are often severely degraded due to anthropogenic activities and are generally contaminated with priority pollutants, especially heavy metals and polycyclic aromatic hydrocarbons. Characterizing these degraded and contaminated soils and making them productive again to restore the required ecosystem services was the theme of the "Soil in the City- 2014" conference organized by W-2170 Committee (USDA's Sponsored Multi-State Research Project: Soil-Based Use of Residuals, Wastewater, & Reclaimed Water). This special section of comprises 12 targeted papers authored by conference participants to make available much needed information about the characteristics of urban soils. Innovative ways to mitigate the risks from pollutants and to improve the soil quality using local resources are discussed. Such practices include the use of composts and biosolids to grow healthy foods, reclaim brownfields, manage stormwater, and improve the overall ecosystem functioning of urban soils. These papers provide a needed resource for educating policymakers, practitioners, and the general public about using locally available resources to restore fertility, productivity, and ecosystem functioning of degraded urban land to revitalize metropolitan areas for improving the overall quality of life for a large segment of a rapidly growing urban population.

Greening a Steel Mill Slag Brownfield with Biosolids and Sediments: A Case Study.

The former US Steel Corporation's South Works site in Chicago, IL, is a 230-ha bare brownfield consisting of steel mill slag fill materials that will need to be reclaimed to support and sustain vegetation. We conducted a case study to evaluate the suitability of biosolids and dredged sediments for capping the steel mill slag to establish good quality turfgrass vegetation. Eight study plots were established on a 0.4-ha parcel that received biosolids and dredged sediment blends of 0, 25, 50, or 100% biosolids (v/v). Turfgrass was successfully established and was thicker and greener in biosolids-amended sediments than in unamended sediments. Concentrations of N, P, K, and micronutrients in turfgrass tissues increased with increasing biosolids. Soil organic carbon, N, P, and micronutrients increased with increasing biosolids. Cadmium, Cu, Ni, and Zn concentrations in biosolids-amended sediments also increased with increasing biosolids but were far below phytotoxicity limits for turfgrass. Lead and Cr concentrations in biosolids-amended plots were comparable to concentrations in unamended sediments. Groundwater monitoring lysimeters and wells below the study site and near Lake Michigan were not affected by nutrients leaching from the amendments. Overall, the results from this case study demonstrated that blends of biosolids and dredged sediments could be successfully used for capping steel mill slag brownfield sites to establish good quality turfgrass vegetation.

In-situ infiltration performance of different permeable pavements in a employee used parking lot--A four-year study.

Permeable pavements are being adopted as a green solution in many parts of the world to manage urban stormwater quantity and quality. This paper reports on the measured in-situ infiltration performance over a four-year period since construction and use of three permeable parking sections (permeable pavers, permeable concrete and permeable asphalt) of an employee car parking lot. There was only a marginal decline in infiltration rates of all three pavements after one year of use. However, between years two to four, the infiltration rates declined significantly due to clogging of pores either by dry deposition of particles and/or shear stress of vehicles driving and degrading the permeable surfaces; during the last two years, a greater decline was also observed in driving areas of the parking lots compared to parking slots, where minimal wear and tear are expected. Maintenance strategies were employed to reclaim some of the lost infiltration rate of the permeable pavements to limited success. Despite this decline, the infiltration rates were still four to five times higher than average rainstorm intensity in the region. Thus, these permeable pavement parking lots may have significant ecological importance due to their ability to infiltrate rainwater quickly, reduce the runoff in the catchment area, and also dampen runoff peak flows that could otherwise enter the collection system for treatment in a combined sewer area.

Application of organic amendments to restore degraded soil: effects on soil microbial properties.

Topsoil removal, compaction, and other practices in urban and industrial landscapes can degrade soil and soil ecosystem services. There is growing interest to remediate these for recreational and residential purposes, and urban waste materials offers potential to improve degraded soils. Therefore, the objective of this study was to compare the effects of urban waste products on microbial properties of a degraded industrial soil. The soil amendments were vegetative yard waste compost (VC), biosolids (BioS), and a designer mix (DM) containing BioS, biochar (BC), and drinking water treatment residual (WTR). The experiment had a completely randomized design with following treatments initiated in 2009: control soil, VC, BioS-1 (202 Mg ha(-1)), BioS-2 (403 Mg ha(-1)), and DM (202 Mg BioS ha(-1) plus BC and WTR). Soils (0-15-cm depth) were sampled in 2009, 2010, and 2011 and analyzed for enzyme activities (arylsulfatase, ß-glucosaminidase, ß-glucosidase, acid phosphatase, fluorescein diacetate, and urease) and soil microbial community structure using phospholipid fatty acid analysis (PLFA). In general, all organic amendments increased enzyme activities in 2009 with BioS treatments having the highest activity. However, this was followed by a decline in enzyme activities by 2011 that were still significantly higher than control. The fungal PLFA biomarkers were highest in the BioS treatments, whereas the control soil had the highest levels of the PLFA stress markers (P < 0.10). In conclusion, one-time addition of VC or BioS was most effective on enzyme activities; the BioS treatment significantly increased fungal biomass over the other treatments; addition of BioS to soils decreased microbial stress levels; and microbial measures showed no statistical differences between BioS and VC treatments after 3 years of treatment.

Bioaccumulation of perfluoroalkyl acids by earthworms (Eisenia fetida) exposed to contaminated soils.

The presence of perfluoroalkyl acids (PFAAs) in biosolids-amended and aqueous film-forming foam (AFFF)-impacted soils results in two potential pathways for movement of these environmental contaminants into terrestrial foodwebs. Uptake of PFAAs by earthworms (Eisenia fetida) exposed to unspiked soils with varying levels of PFAAs (a control soil, an industrially impacted biosolids-amended soil, a municipal biosolids-amended soil, and two AFFF-impacted soils) was measured. Standard 28 day exposure experiments were conducted in each soil, and measurements taken at additional time points in the municipal soil were used to model the kinetics of uptake. Uptake and elimination rates and modeling suggested that steady state bioaccumulation was reached within 28 days of exposure for all PFAAs. The highest concentrations in the earthworms were for perfluorooctane sulfonate (PFOS) in the AFFF-impacted Soil A (2160 ng/g) and perfluorododecanoate (PFDoA) in the industrially impacted soil (737 ng/g). Wet-weight (ww) and organic carbon (OC)-based biota soil accumulation factors (BSAFs) for the earthworms were calculated after 28 days of exposure for all five soils. The highest BSAF in the industrially impacted soil was for PFDoA (0.42 goc/gww,worm). Bioaccumulation factors (BAFs, dry-weight-basis, dw) were also calculated at 28 days for each of the soils. With the exception of the control soil and perfluorodecanoate (PFDA) in the industrially impacted soil, all BAF values were above unity, with the highest being for perfluorohexanesulfonate (PFHxS) in the AFFF-impacted Soil A (139 gdw,soil/gdw,worm). BSAFs and BAFs increased with increasing chain length for the perfluorocarboxylates (PFCAs) and decreased with increasing chain length for the perfluoroalkyl sulfonates (PFSAs). The results indicate that PFAA bioaccumulation into earthworms depends on soil concentrations, soil characteristics, analyte, and duration of exposure, and that accumulation into earthworms may be a potential route of entry of PFAAs into terrestrial foodwebs.

Nitrogen mineralization from anaerobically digested centrifuge cake and aged air-dried biosolids.

This study was conducted to estimate nitrogen (N) mineralization of anaerobically digested centrifuge cake from the Stickney Water Reclamation Plant (SWRP) and Calumet Water Reclamation Plant (CWRP), lagoon-aged air-dried biosolids from the CWRP, and Milorganite at three rates of application (0, 12.5 and 25 Mg ha(-1)). The N mineralized varied among biosolids as follows: Milorganite (44%) > SWRP centrifuge cake (35%) > CWRP centrifuge cake (31%) > aged air-dried (13%). The N mineralized in the SWRP cake (32%) and CWRP aged air-dried biosolids (12%) determined from the 15N study were in agreement with the first study. The N mineralization value for centrifuge cake biosolids observed in our study is higher than the value given in the Part 503 rule and Illinois Part 391 guidelines. These results will be used to fine-tune biosolids application rate to match crop N demand without compromising yield while minimizing any adverse effect on the environment.

Perfluoroalkyl acid distribution in various plant compartments of edible crops grown in biosolids-amended soils.

Crop uptake of perfluoroalkyl acids (PFAAs) from biosolids-amended soil has been identified as a potential pathway for PFAA entry into the terrestrial food chain. This study compared the uptake of PFAAs in greenhouse-grown radish (Raphanus sativus), celery (Apium graveolens var. dulce), tomato (Lycopersicon lycopersicum), and sugar snap pea (Pisum sativum var. macrocarpon) from an industrially impacted biosolids-amended soil, a municipal biosolids-amended soil, and a control soil. Individual concentrations of PFAAs, on a dry weight basis, in mature, edible portions of crops grown in soil amended with PFAA industrially impacted biosolids were highest for perfluorooctanoate (PFOA; 67 ng/g) in radish root, perfluorobutanoate (PFBA; 232 ng/g) in celery shoot, and PFBA (150 ng/g) in pea fruit. Comparatively, PFAA concentrations in edible compartments of crops grown in the municipal biosolids-amended soil and in the control soil were less than 25 ng/g. Bioaccumulation factors (BAFs) were calculated for the root, shoot, and fruit compartments (as applicable) of all crops grown in the industrially impacted soil. BAFs were highest for PFBA in the shoots of all crops, as well as in the fruit compartment of pea. Root-soil concentration factors (RCFs) for tomato and pea were independent of PFAA chain length, while radish and celery RCFs showed a slight decrease with increasing chain length. Shoot-soil concentration factors (SCFs) for all crops showed a decrease with increasing chain length (0.11 to 0.36 log decrease per CF2 group). The biggest decrease (0.54-0.58 log decrease per CF2 group) was seen in fruit-soil concentration factors (FCFs). Crop anatomy and PFAA properties were utilized to explain data trends. In general, fruit crops were found to accumulate fewer long-chain PFAAs than shoot or root crops presumably due to an increasing number of biological barriers as the contaminant is transported throughout the plant (roots to shoots to fruits). These data were incorporated into a preliminary conceptual framework for PFAA accumulation in edible crops. In addition, these data suggest that edible crops grown in soils conventionally amended for nutrients with biosolids (that are not impacted by PFAA industries) are unlikely a significant source of long-chain PFAA exposure to humans.

Improvements in biosolids quality resulting from the Clean Water Act.

Promulgation of the Clean Water Act (CWA) authorized the United States Environmental Protection Agency (U.S. EPA) to regulate quality standards for surface waters and establish regulations limiting the amounts and types of pollutants entering the nation's waters. U.S. EPA imposed national pretreatment standards on industrial wastes discharged to the collection systems of publicly owned treatment works (POTWs) and promulgated General Pretreatment Regulations in 1978. This study analyzed trace metals data from the National Sewage Sludge Surveys conducted by U.S. EPA and the American Metropolitan Sewage Agencies (AMSA) to evaluate the effect of implementation of the national industrial pretreatment standards on concentrations of trace metals in sludges generated by POTWs in the United States. The data showed that implementation of pretreatment programs has been highly effective in reducing the amount of pollutants that enter POTWs and has resulted in a substantial reduction in the levels of trace metals in the municipal sludges. Concentrations of chromium, lead, and nickel in sludge declined by 78, 73, and 63%, respectively, within a year after promulgation of General Pretreatment Regulations. Resulting from these measures, metal concentrations in the sludges generated by a majority of POTWs in the United States are sufficiently low that the sludges can be classified as biosolids and also meet the U.S. EPA's exceptional quality criteria for trace metals in biosolids. This improvement gives POTWs the option to use their biosolids beneficially through land application.

Uptake of perfluoroalkyl acids into edible crops via land applied biosolids: field and greenhouse studies.

The presence of perfluoroalkyl acids (PFAAs) in biosolids destined for use in agriculture has raised concerns about their potential to enter the terrestrial food chain via bioaccumulation in edible plants. Uptake of PFAAs by greenhouse lettuce ( Lactuca sativa ) and tomato ( Lycopersicon lycopersicum ) grown in an industrially impacted biosolids-amended soil, a municipal biosolids-amended soil, and a control soil was measured. Bioaccumulation factors (BAFs) were calculated for the edible portions of both lettuce and tomato. Dry weight concentrations observed in lettuce grown in a soil amended (biosolids:soil dry weight ratio of 1:10) with PFAA industrially contaminated biosolids were up to 266 and 236 ng/g for perfluorobutanoic acid (PFBA) and perfluoropentanoic acid (PFPeA), respectively, and reached 56 and 211 ng/g for PFBA and PFPeA in tomato, respectively. BAFs for many PFAAs were well above unity, with PFBA having the highest BAF in lettuce (56.8) and PFPeA the highest in tomato (17.1). In addition, the BAFs for PFAAs in greenhouse lettuce decreased approximately 0.3 log units per CF2 group. A limited-scale field study was conducted to verify greenhouse findings. The greatest accumulation was seen for PFBA and PFPeA in both field-grown lettuce and tomato; BAFs for PFBA were highest in both crops. PFAA levels measured in lettuce and tomato grown in field soil amended with only a single application of biosolids (at an agronomic rate for nitrogen) were predominantly below the limit of quantitation (LOQ). In addition, corn ( Zea mays ) stover, corn grains, and soil were collected from several full-scale biosolids-amended farm fields. At these fields, all PFAAs were below the LOQ in the corn grains and only trace amounts of PFBA and PFPeA were detected in the corn stover. This study confirms that the bioaccumulation of PFAAs from biosolids-amended soils depends strongly on PFAA concentrations, soil properties, the type of crop, and analyte.

Polybrominated diphenyl ethers in U.S. sewage sludges and biosolids: temporal and geographical trends and uptake by corn following land application.

Polybrominated diphenyl ethers (PBDEs) have been used extensively to flame-retard polymers and textiles. These persistent chemicals enter wastewater streams following manufacture, use, and disposal, concentrating in the settled solids during treatment. Land application of stabilized sewage sludge (known as biosolids) can contribute PBDEs to terrestrial systems. Monitoring sludge/biosolids contaminant burdens may be valuable in revealing trends in societal chemical usage and environmental release. In archived Chicago area sludges/biosolids from 1975 to 2008, penta-BDE concentrations increased and then plateaued after about 2000. Penta-BDE manufacture in the United States ended in December 2004. Deca-BDE concentrations in biosolids rose from 1995 to 2008, doubling on a 5-year interval. Evaluation of U.S. Environmental Protection Agency Targeted National Sewage Sludge Survey data from 2006 to 2007 revealed highest penta-BDE biosolids levels from western and lowest from northeastern wastewater treatment plants (2120 and 1530 µg/kg, respectively), consistent with patterns reported in some recent indoor dust and human blood studies. No significant regional trends were observed for deca-BDE concentrations. Congener patterns in contemporary Chicago biosolids support the contention that BDE-209 can be dehalogenated to less brominated congeners. Biosolids application on agricultural fields increased PBDE soil concentrations. However, corn grown thereon did not exhibit measurable PBDE uptake; perhaps due to low bioavailability of the biosolids-associated flame retardants.

Distinct responses in ammonia-oxidizing archaea and bacteria after addition of biosolids to an agricultural soil.

The recently discovered ammonia-oxidizing archaea (AOA) have been suggested as contributors to the first step of nitrification in terrestrial ecosystems, a role that was previously assigned exclusively to ammonia-oxidizing bacteria (AOB). The current study assessed the effects of agricultural management, specifically amendment of soil with biosolids or synthetic fertilizer, on nitrification rates and copy numbers of archaeal and bacterial ammonia monooxygenase (amoA) genes. Anaerobically digested biosolids or synthetic fertilizer was applied annually for three consecutive years to field plots used for corn production. Biosolids were applied at two loading rates, a typical agronomic rate (27 Mg hectare(-1) year(-1)) and double the agronomic rate (54 Mg hectare(-1) year(-1)), while synthetic fertilizer was applied at an agronomic rate typical for the region (291 kg N hectare(-1) year(-1)). Both biosolids amendments and synthetic fertilizer increased soil N and corn yield, but only the biosolids amendments resulted in significant increases in nitrification rates and increases in the copy numbers of archaeal and bacterial amoA genes. In addition, only archaeal amoA gene copy numbers increased in response to biosolids applied at the typical agronomic rate and showed a significant correlation with nitrification rates. Finally, copy numbers of archaeal amoA genes were significantly higher than copy numbers of bacterial amoA genes for all treatments. These results implicate AOA as being primarily responsible for the increased nitrification observed in an agricultural soil amended with biosolids. These results also support the hypothesis that physiological differences between AOA and AOB may enable them to occupy distinct ecological niches.

Occurrence and fate of perfluorochemicals in soil following the land application of municipal biosolids.

The recent implementation of soil and drinking water screening guidance values for two perfluorochemicals (PFCs), perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) by the U.S. Environmental Protection Agency (EPA), reflects the growing concerns regarding the presence of these persistent and bioaccumulative chemicals in the natural environment. Previous work has established the potential risk to the environment from the land application of industrially contaminated biosolids, but studies focusing on environmental risk from land application of typical municipal biosolids are lacking. Thus, the present study investigated the occurrence and fate of PFCs from land-applied municipal biosolids by evaluating the levels, mass balance, desorption, and transport of PFCs in soils receiving application of municipal biosolids at various loading rates. This study is the first to report levels of PFCs in agricultural soils amended with typical municipal biosolids. PFOS was the dominant PFC in both biosolids (80-219 ng/g) and biosolids-amended soil (2-483 ng/g). Concentrations of all PFCs in soil increased linearly with increasing biosolids loading rate. These data were used to develop a model for predicting PFC soil concentrations in soils amended with typical municipal biosolids using cumulative biosolids loading rates. Mass balance calculations comparing PFCs applied vs those recovered in the surface soil interval indicated the potential transformation of PFC precursors. Laboratory desorption experiments indicated that the leaching potential of PFCs decreases with increasing chain length and that previously derived organic-carbon normalized partition coefficients may not be accurate predictors of the desorption of long-chain PFCs from biosolids-amended soils. Trace levels of PFCs were also detected in soil cores from biosolids-amended soils to depths of 120 cm, suggesting potential movement of these compounds within the soil profile over time and confirming the higher transport potential for short-chain PFCs in soils amended with municipal biosolids.

Persistence of triclocarban and triclosan in soils after land application of biosolids and bioaccumulation in Eisenia foetida.

The presence of the antimicrobial chemicals triclocarban (TCC) and triclosan (TCS) in municipal biosolids has raised concerns about the potential impacts of these chemicals on soil ecosystems following land application of municipal biosolids. The relative persistence of TCC and TCS in agricultural fields receiving yearly applications of biosolids at six different loading rates over a three-year period was investigated. Soil and biosolids samples were collected, extracted, and analyzed for TCC and TCS using liquid chromatography-tandem mass spectrometry. In addition, the potential for bioaccumulation of TCC and TCS from the biosolids-amended soils was assessed over 28 d in the earthworm Eisenia foetida. Standard 28-d bioaccumulation tests were conducted for three biosolids loading rates from two sites, representing agronomic and twice the agronomic rates of biosolids application plots as well as control plots receiving no applications of biosolids. Additional bioaccumulation kinetic data were collected for the soils receiving the high biosolids loadings to ensure attainment of quasi steady-state conditions. The results indicate that TCC is relatively more persistent in biosolids-amended soil than TCS. In addition, TCC bioaccumulated in E. foetida, reaching body burdens of 25 ± 4 and 133 ± 17 ng/g(ww) in worms exposed for 28 d to the two soils amended with biosolids at agronomic rates. The 28-d organic carbon and lipid-normalized biota soil accumulation factors (BSAFs) were calculated for TCC and ranged from 0.22 ± 0.12 to 0.71 ± 0.13. These findings suggest that TCC bioaccumulation is somewhat consistent with the traditional hydrophobic organic contaminant (HOC) partitioning paradigm. However, these data also suggest substantially reduced bioavailability of TCC in biosolids-amended soils compared with HOC partitioning theory.

Triclocarban, triclosan, polybrominated diphenyl ethers, and 4-nonylphenol in biosolids and in soil receiving 33-year biosolids application.

Land application of biosolids is a common practice throughout the world. However, concerns continue to be raised about the safety of this practice, because biosolids may contain trace levels of organic contaminants. The present study evaluated the levels of triclocarban (TCC), triclosan (TCS), 4-nonylphenol (4-NP), and polybrominated diphenyl ethers (PBDEs) in biosolids from 16 wastewater treatment plants and in soils from field plots receiving annual applications of biosolids for 33 years. All of the four contaminants evaluated were detected in most of the biosolids at concentrations ranging from hundreds of microg/kg to over 1,000 mg/kg (dry wt basis). They were detected at microg/kg levels in the biosolids-amended soil, but their concentrations decreased sharply with increasing soil depth for 4-NP, PBDEs, and TCC, indicating limited soil leaching of those compounds. However, potential leaching of TCS in the biosolids-amended soils was observed. The levels of all four compounds in the surface soil increased with increasing biosolids application rate. Compared with the estimated 33-year cumulative input to the soil during the 33-year consecutive biosolids application, most of the PBDEs and a small percentage of 4-NP, TCC, and TCS remained in the top 120-cm soil layer. These observations suggest slow degradation of PBDEs but rapid transformation of 4-NP, TCC, and TCS in the biosolids-amended soils.

Levels of dioxins in soil and corn tissues after 30 years of biosolids application.

Detectable levels of dioxins have been reported in biosolids, but very little information is available on the effect of long-term application of biosolids on dioxins accumulation in soil and uptake by plants. We analyzed dioxins in soil and corn tissue samples from field plots after 30 continuous applications of biosolids at 0 (Control), 16.8, and 67.2 Mg biosolids ha(-1) yr(-1) resulting in 0, 504, and 2016 Mg ha(-1) cumulative loadings of biosolids, respectively. The levels of dioxins in soil were only 79.9, 115.5, and 247.5 ng toxic equivalents (TEQs) kg(-1) in the 0, 504, and 2016 Mg biosolids ha(-1) plots, respectively. Dioxins were not detected in the corn grain, and only trace levels (6.8-7.5 ng TEQs kg(-1)) were found in the corn stover; however, these values were not statistically different between control and biosolids-amended soils. These observations suggest that although long-term application of biosolids may increase the levels of dioxins in soil, it does not affect dioxins uptake by corn.

Abiotic transformation of DDT in aqueous solutions.

Significant concentrations of chlorinated pesticides such as 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) and its two main transformation products, 1,1-dichloro-2,2-bis(4-chlorophenyl)ethane (DDD) and 1,1-dichloro-2,2-bis(4-chlorophenyl)ethylene (DDE) are still present in soil and sediment systems more than 30 years after DDT use was banned in the United States. DDT enters waterways via the runoff from industrial point sources, agricultural lands and atmospheric deposition. We evaluated zero-valent iron (Fe(0)), ferrous sulfide (FeS), as well as combining them with hydrogen peroxide (H(2)O(2)) as viable treatment technologies for degrading DDT in an aqueous solution. Treatment of DDT with Fe(0) and FeS resulted in approximately 88% and 56% transformation of DDT within 150h, respectively. DDE production was insignificant in all systems. The DDT removal was slower with FeS than with Fe(0), but the amounts of DDD and DDE produced did not exceed baseline. Treatment with a 1:1 mixture of Fe(0)-FeS removed about 95% of the added mass of DDT within 4days and generated significant amounts of DDD and minor amounts of DDMU. When small amounts of H(2)O(2) were introduced halfway through the Fe(0) and FeS treatment times, the mass of DDT decreased by 87% and 96%, respectively, within 2days. Our results demonstrate that mixtures of Fe(0)-FeS in combination with H(2)O(2) can be used for rapid and efficient removal of DDT from aqueous solutions.

Sorption and transport behavior of naphthalene in an aggregated soil.

Soil solution chemistry influences the sorption and transport behavior of hydrophobic organic compounds (HOCs) in soil. We used both batch and column studies to investigate the influence of ionic strengths (0.03 and 1.5 M) and flow velocities (12 and 24 cm h-1) on sorption and transport of naphthalene (NAP) in aggregated soil. Sorption parameters such as the Freundlich coefficient (Kf) and exponent (n) calculated from batch studies and column experiments were also compared. Retardation of NAP transport was greater at higher solution ionic strength, which may be attributed to greater sorption affinity due to enhanced aggregation of the sorbent. The effect of ionic strength on sorption of NAP observed in the batch study was consistent with the results from the column study. The Kf and n values obtained from the batch study for the two ionic strengths ranged from 7.8 to 13.7 and 0.68 to 0.80, respectively, whereas the Kf and n values obtained from the column study ranged from 7.9 to 9.9 and 0.73 to 0.85, respectively. The effluent breakthrough curve (BTC) of NAP at a flow rate of 24 cm h-1 showed significant chemical and physical nonequilibrium behavior, implying that a considerable amount of sorption in aggregated soil was time dependent when flow was relatively fast. The BTCs calculated with the parameters determined from batch studies compared poorly with the measured BTCs. The potential for nonequilibrium transport should be incorporated in models used for predicting the fate and transport of HOCs. Furthermore, caution is required when extrapolating the results from batch studies, especially for aggregated soils.