Biochar reduces the efficiency of nitrification inhibitor 3,4-dimethylpyrazole phosphate (DMPP) mitigating N2O emissions

Among strategies suggested to decrease agricultural soil N₂O losses, the use of nitrification inhibitors such as DMPP (3,4-dimethylpyrazole phosphate) has been proposed. However, the efficiency of DMPP might be affected by soil amendments, such as biochar, which has been shown to reduce N₂O emissions. This study evaluated the synergic effect of a woody biochar applied with DMPP on soil N₂O emissions. A incubation study was conducted with a silt loam soil and a biochar obtained from Pinus taeda at 500 °C. Two biochar rates (0 and 2% (w/w)) and three different nitrogen treatments (unfertilized, fertilized and fertilized + DMPP) were assayed under two contrasting soil water content levels (40% and 80% of water filled pore space (WFPS)) over a 163 day incubation period. Results showed that DMPP reduced N₂O emissions by reducing ammonia-oxidizing bacteria (AOB) populations and promoting the last step of denitrification (measured by the ratio nosZI + nosZII/nirS + nirK genes). Biochar mitigated N₂O emissions only at 40% WFPS due to a reduction in AOB population. However, when DMPP was applied to the biochar amended soil, a counteracting effect was observed, since the N₂O mitigation induced by DMPP was lower than in control soil, demonstrating that this biochar diminishes the efficiency of the DMPP both at low and high soil water contents.

Dealing with the loss of a resident: An analysis of burnout rates in a reduced complement training program

BACKGROUND

Residents in all fields of medicine experience high levels of burnout and less job-related satisfaction due to the stress experienced during training. Reduced complement residency classes often experience increased workloads due to the need to compensate for the fewer number of classmates.

OBJECTIVE

The goal of this study was to examine whether residency classes of reduced size experience higher levels of burnout.

METHODS

The Maslach Burnout Inventory Survey was distributed to all orthopaedic residents at our institution for four consecutive years. Emotional exhaustion≥27 and depersonalization≥10 correlate with high levels of burnout. At our institution, two residents were lost during their second year of training. Group 1 (n = 56) consisted of residents with reduced-size classes, while group 2 (n = 60) consisted of residents with full complement classes.

RESULTS

Mean emotional exhaustion (29 vs. 30) and depersonalization (17 vs. 17) scores were comparable between reduced and full complement classes. The Maslach data from our study showed no statistical difference in burnout levels between classes of full complement and reduced complement.

CONCLUSIONS

When compared to a previous study on burnout conducted in large orthopaedic residency programs, our entire residency program did demonstrate similar levels of emotional exhaustion and depersonalization.

Surgical Reconstruction of the Acetabulum and Pelvis in Metastatic Bone Disease

Management of a painful metastatic acetabular lesion is complex and requires the assessment of tumor size and location, remaining integrity of the acetabulum, analgesic requirements, ability to use postoperative radiation, and projected patient survival. Patients presenting with suspected periacetabular metastasis frequently have groin pain aggravated by weight bearing. After a complete physical examination, advanced imaging and a complete laboratory workup should be performed to assess the extent of local and systemic disease. If a patient has a previously identified metastatic lesion, it is beneficial to communicate with the patient's medical oncologist to gather information on responses to chemotherapeutic agents, hormonal agents, and radiation therapy. Management may be nonsurgical, interventional, or surgical. Despite the limited life expectancy of patients with periacetabular metastasis, when performed in the appropriate setting, reconstruction by using anti-protrusio cages, screws, and cemented hip arthroplasty can improve quality of life by aiding independent ambulation and decreasing pain.

Complications following allograft reconstruction for primary bone tumors: Considerations for management

Introduction

The aim of this study was to investigate complication rates and types following allograft reconstruction and discuss unique considerations for management.

Methods

Seventy-four consecutive patients underwent large segment allograft reconstruction following resection of primary musculoskeletal tumors from 1991 to 2016. Mean patient age was 32 ± 20 years (range, 5-71 years). Minimum follow-up was 2 years unless patients were lost to disease prior. Mean follow-up was 105 months.

Results

Thirty-five patients had complications requiring subsequent surgery at a mean of 30 months (range, 1-146 months) post-operatively. Individual complication rates were 29%, 50%, and 42% for Allograft Prosthetic Composite, Intercalary, and Osteoarticular allograft reconstruction, respectively. Risk factors for complication included age less than 30 (OR 4.5; p = 0.002), male gender (OR 2.8; p = 0.031), chemotherapy (OR 4.4; p = 0.003), lower extremity disease (OR 3.4; p = 0.025). In patients with complications, limb-retention rate was 91% and mean MSTS scores were 23.6.

Conclusion

Despite considerable complication rates, management with a systematic approach results in successful outcomes with limb-retention greater than 90% and mean MSTS scores of 79%. In carefully selected patients, allografts provide a reliable method of reconstruction with treatable complications occurring at a mean of 30 months.

Evaluation of the Content and Accessibility of Web Sites for Accredited Orthopaedic Trauma Surgery Fellowships

BACKGROUND

Orthopaedic trauma fellowship applicants use online-based resources when researching information on potential U.S. fellowship programs. The 2 primary sources for identifying programs are the Orthopaedic Trauma Association (OTA) database and the San Francisco Match (SF Match) database. Previous studies in other orthopaedic subspecialty areas have demonstrated considerable discrepancies among fellowship programs. The purpose of this study was to analyze content and availability of information on orthopaedic trauma surgery fellowship web sites.

METHODS

The online databases of the OTA and SF Match were reviewed to determine the availability of embedded program links or external links for the included programs. Thereafter, a Google search was performed for each program individually by typing the program's name, followed by the term "orthopaedic trauma fellowship." All identified fellowship web sites were analyzed for accessibility and content. Web sites were evaluated for comprehensiveness in mentioning key components of the orthopaedic trauma surgery curriculum. By consensus, we refined the final list of variables utilizing the methodology of previous studies on the topic.

RESULTS

We identified 54 OTA-accredited fellowship programs, offering 87 positions. The majority (94%) of programs had web sites accessible through a Google search. Of the 51 web sites found, all (100%) described their program. Most commonly, hospital affiliation (88%), operative experiences (76%), and rotation overview (65%) were listed, and, least commonly, interview dates (6%), selection criteria (16%), on-call requirements (20%), and fellow evaluation criteria (20%) were listed. Programs with ≥2 fellows provided more information with regard to education content (p = 0.0001) and recruitment content (p = 0.013). Programs with Accreditation Council for Graduate Medical Education (ACGME) accreditation status also provided greater information with regard to education content (odds ratio, 4.0; p = 0.0001). Otherwise, no differences were seen by region, residency affiliation, medical school affiliation, or hospital affiliation.

CONCLUSIONS

The SF Match and OTA databases provide few direct links to fellowship web sites. Individual program web sites do not effectively and completely convey information about the programs. The Internet is an underused resource for fellow recruitment. The lack of information on these sites allows for future opportunity to optimize this resource.

A Preoperative Scale for Determining Surgical Readmission Risk After Total Knee Arthroplasty

BACKGROUND

Total knee arthroplasty (TKA) is one of the most common orthopaedic procedures performed in the U.S. The purpose of this study was to develop and verify a scale to preoperatively stratify a patient's risk of being readmitted to the hospital following a TKA.

METHODS

Discharge data on 433,638 patients from New York and California (derivation cohort) and 269,934 patients from Florida and Washington (validation cohort) who underwent TKA were collected from the State Inpatient Database, a part of the Healthcare Cost and Utilization Project of the Agency for Healthcare Research and Quality (2006 to 2011). Demographic and clinical characteristics of patients were abstracted and analyzed to develop the Readmission After Total Knee Arthroplasty (RATKA) Scale.

RESULTS

Overall 30-day readmission rates in the derivation and validation cohorts were 5.11% and 4.98%, respectively. The following factors were significantly associated with increased 30-day readmission rates in the derivation cohort: age of 41 to 50 years (odds ratio [OR] = 1.13), age of 71 to 80 years (OR = 1.21), age of 81 to 90 years (OR = 1.70), male sex (OR = 1.19), African-American race (OR = 1.37), "other" race/ethnicity (OR = 1.08), Medicaid payer (OR = 1.43), Medicare payer (OR = 1.27), anemia (OR = 1.19), chronic obstructive pulmonary disease (OR = 1.29), coagulopathy (OR = 1.22), congestive heart failure (OR = 1.64), diabetes (OR = 1.19), fluid and electrolyte disorder (OR = 1.25), hypertension (OR = 1.10), liver disease (OR = 1.27), renal failure (OR = 1.33), and rheumatoid arthritis (OR = 1.14). These factors were used to create the RATKA Scale. The RATKA score was then used to define 3 levels of risk for readmission: low (RATKA score of <13; 3.7% readmission rate), moderate (RATKA score of 13 to 16; 5.4% readmission rate), and high (RATKA score of >16; 7.6% readmission rate). The relative risk of readmission was 2.06 for the high-risk group compared with the low-risk group.

CONCLUSIONS

The RATKA Scale derived from patient data from the derivation cohort was reliably able to explain readmission variability after TKA for patients in the validation cohort at a rate of >95%. Models such as the RATKA Scale will enable identification of the risk of readmission following TKA based on a patient's risk profile prior to surgery.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Effects of local vanadium delivery on diabetic fracture healing

This study evaluated the effect of local vanadyl acetylacetonate (VAC), an insulin mimetic agent, upon the early and late parameters of fracture healing in rats using a standard femur fracture model. Mechanical testing, and radiographic scoring were performed, as well as histomorphometry, including percent bone, percent cartilage, and osteoclast numbers. Fractures treated with local 1.5 mg/kg VAC possessed significantly increased mechanical properties compared to controls at 6 weeks post-fracture, including increased torque to failure (15%; p = 0.046), shear modulus (89%; p = 0.043), and shear stress (81%; p = 0.009). The radiographic scoring analysis showed increased cortical bridging at 4 weeks and 6 weeks (119%; p = 0.036 and 209%; p = 0.002) in 1.5 mg/kg VAC treated groups. Histomorphometry of the fracture callus at days 10 and 14 showed increased percent cartilage (121%; p = 0.009 and 45%; p = 0.035) and percent mineralized tissue (66%; p = 0.035 and 58%; p = 0.006) with local VAC treated groups compared to control. Additionally, fewer osteoclasts were observed in the local VAC treated animals as compared to controls at day 14 (0.45% ± 0.29% vs. 0.83% ± 0.36% of callus area; p = 0.032). The results suggest local administration of VAC acts to modulate osteoclast activity and increase percentage of early callus cartilage, ultimately enhancing mechanical properties comparably to non-diabetic animals treated with local VAC. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2174-2180, 2017.

Hoverboards: A new cause of pediatric morbidity

INTRODUCTION

The hoverboard, a self-balancing powered scooter, was introduced to the market in 2015 and quickly became one of the most popular purchases of the year. As with similar products, this scooter brought a host of concerns surrounding injuries. The purpose of this study is to determine the incidence of injuries that coincided with the popularity of hoverboard.

METHODS

The National Electronic Injury Surveillance System (NEISS) was queried from 2011 through 2015 for injuries related to scooters/skateboards, powered (product number, 5042), which includes the hoverboard. Patient data on sex, age, race, diagnosis, most severely injured body part, location where the injury occurred, and narrative of the injury were collected. The estimated injury incidence was calculated and compared on a yearly and monthly basis. Google Trends was used to determine the popularity of the hoverboard over the same time period.

RESULTS

During the 5-year study period, there were an estimated 47,277 injuries associated with the hoverboard. In 2015, there was an average 208% (range, 167-278%; standard deviation (SD), 51.8%) increase in the number of injuries compared to any of the previous 4 years. Further analysis of these injuries revealed a significant increase in the number of forearm (475%; range, 310-662%; SD, 159%), leg (178%; range, 133-206%; SD, 34%), and head and neck (187%; range, 179-197%; SD, 7.6%) injuries in 2015 compared to the previous 4 years. The most common type of injury in 2015 was a fracture (38.9%). Analysis of the sites of these fractures between 2014 and 2015 revealed a 752% increase in forearm fractures, which included over a 4000% increase in the number of wrist fractures.

CONCLUSIONS

Given the number of injuries caused by these products, safety equipment, such as wrist guards and helmets, should be worn in an attempt to reduce the number of injuries. Additionally, this study highlights the importance of physicians keeping up to date with current trends to best advise their patients on safe practices.

Supplemental Bone Grafting in Giant Cell Tumor of the Extremity Reduces Nononcologic Complications

BACKGROUND

Giant cell tumors (GCTs) are treated with resection curettage and adjuvants followed by stabilization. Complications include recurrence, fracture, and joint degeneration. Studies have shown treatment with polymethylmethacrylate (PMMA) may increase the risk of joint degeneration and fracture. Other studies have suggested that subchondral bone grafting may reduce these risks.

QUESTIONS/PURPOSES

Following standard intralesional resection-curettage and adjuvant treatment, is the use of bone graft, with or without supplemental PMMA, (1) associated with fewer nononcologic complications; (2) associated with differences in tumor recurrence between patients treated with versus those treated without bone grafting for GCT; and (3) associated with differences in Musculoskeletal Tumor Society (MSTS) scores?

METHODS

Between 1996 and 2014, 49 patients presented with GCT in the epiphysis of a long bone. Six patients were excluded, four who were lost to followup before 12 months and two because they presented with displaced, comminuted, intraarticular pathologic fractures with a nonreconstructable joint surface. The remaining 43 patients were included in our study at a mean followup of 59 months (range, 12-234 months). After resection-curettage, 21 patients were reconstructed using femoral head allograft with or without PMMA (JB) and 22 patients were reconstructed using PMMA alone (FRP, KSB); each surgeon used the same approach (that is, bone graft or no bone graft) throughout the period of study. The primary study comparison was between patients treated with bone graft (with or without PMMA) and those treated without bone graft.

RESULTS

Nononcologic complications occurred less frequently in patients treated with bone graft than those treated without (10% [two of 21] versus 55% [12 of 22]; odds ratio, 0.088; 95% confidence interval [CI], 0.02-0.47; p = 0.002). Patients with bone graft had increased nononcologic complication-free survival (hazard ratio, 4.59; 95% CI, 1.39-15.12; p = 0.012). With the numbers available, there was no difference in tumor recurrence between patients treated with bone graft versus without (29% [six of 21] versus 32% [seven of 22]; odds ratio, 0.70; 95% CI, 0.1936-2.531; p = 0.586) or in recurrence-free survival among patients with bone graft versus without (hazard ratio, 0.94; 95% CI, 0.30-2.98; p = 0.920). With the numbers available, there was no difference in mean MSTS scores between patients treated with bone graft versus without (92% ± 2% versus 93% ± 1.4%; mean difference 1.0%; 95% CI, -3.9% to 6.0%; p = 0.675).

CONCLUSIONS

Compared with PMMA alone, the use of periarticular bone graft constructs reduces postoperative complications apparently without increasing the likelihood of tumor recurrence.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Radial Shaft Reconstruction With an Intercalary Endoprosthesis Following Resection of Metastatic Tumor

Improvements in imaging and treatment of musculoskeletal tumors have increased the variety of options for reconstruction following joint-sparing diaphyseal resection. The purpose of this case series was to show that reconstruction of malignant tumors of the radial shaft with an intercalary prosthesis may be an option for patients with segmental bone loss. Three consecutive patients underwent wide resection of the radial diaphysis followed by reconstruction with a custom intercalary prosthesis. A custom intercalary prosthesis with lap joint design was used in all 3 cases. Mean follow-up was 18 months (range, 9-25 months). All patients were weight bearing as tolerated 1 week postoperatively. At the most recent follow-up, patients' mean elbow flexion and extension arc was 137° (range, 130°-140°). At the forearm, mean supination was 60° (range, 30°-90°) and mean pronation was 70° (range, 60°-90°). At the wrist, mean palmar flexion was 80° (range, 70°-90°) and mean dorsiflexion was 80° (range, 70°-90°). All patients reported minimal to no pain and no significant functional limitations. Mean Musculoskeletal Tumor Society score was 26/30 (87%). Reconstruction with an intercalary prosthesis is a viable option for patients with metastatic disease of the radial shaft. All patients had satisfactory results and early return to function; none required return to the operating room. Possible advantages of reconstruction with an intercalary prosthesis compared with reconstruction with a bone graft or polymethylmethacrylate osteosynthesis include early return to function and minimal weight-bearing restrictions postoperatively. [Orthopedics. 2017; 40(2):e242-e247.].

Biochars Reduce Mine Land Soil Bioavailable Metals

Biochar has been proposed as an amendment to remediate mine land soils; however, it could be advantageous and novel if feedstocks local to mine land sites were used for biochar production. Two different feedstocks (pine beetle-killed lodgepole pine [] and tamarisk [ spp.]), within close proximity to mine land-affected soils, were used to create biochars to determine if they have the potential to reduce metal bioavailability. Four different mine land soils, contaminated with various amounts of Cd, Cu, Pb, and Zn, received increasing amounts of biochar (0, 5, 10, and 15% by wt). Soil pH and metal bioavailability were determined, and the European Community Bureau of Reference (BCR) sequential extraction procedure was used to identify pools responsible for potential shifts in bioavailability. Increasing biochar application rates caused increases in soil pH (initial, 3.97; final, 7.49) and 55 to 100% (i.e., no longer detectable) decreases in metal bioavailability. The BCR procedure supported the association of Cd with carbonates, Cu and Zn with oxyhydroxides and carbonates, and Pb with oxyhydroxides; these phases were likely responsible for the reduction in heavy metal bioavailability. This study proved that both of these feedstocks local to abandoned mining operations could be used to create biochars and reduce heavy metal bioavailability in mine land soils.

The Use of the h-Index in Academic Orthopaedic Surgery

BACKGROUND

The Hirsch index (h-index), widely considered a valuable measure of assessing academic productivity, has been studied in various medical and surgical specialties and has shown strong associations between higher h-indices and academic promotion, as well as with National Institutes of Health (NIH) awards. Additionally, the m-index and e-index may complement the h-index in this assessment of merit. The purpose of this study was to investigate the relationship between the h, m, and e-indices and academic rank for 2,061 academic orthopaedic surgeons in the United States.

METHODS

The h-indices of faculty members from 120 academic orthopaedic surgery residency programs were organized and calculated using the Scopus and Google Scholar databases. Additionally, m-index and e-index scores were calculated from Google Scholar. After application of exclusion criteria, 2,061 academic orthopaedic surgeons were included.

RESULTS

Academic rank (assistant professor, associate professor, professor, and chair) increases as mean h-index, m-index, and e-index scores increase. Among 976 assistant professors, 504 associate professors, 461 professors, and 120 chairs, mean h, m, and e-indices increased with each academic rank. In the comparison of male and female surgeons, there was no significant difference in h, m, or e-index scores, with the exception of increased h-index scores among male assistant professors.

CONCLUSIONS

Scholarly impact, as defined by academic productivity and scientific relevance, can be classified by the h-index and supplemented by the m and e-indices. This study has revealed well-defined differences in h, m, and e-indices with regard to academic rank among orthopaedic surgeons. Although the h, m, and e-indices may be of value as adjunct assessment devices for scholarly merit, careful consideration of their limitations must be maintained.

Customizable orthopaedic oncology implants: one institution's experience with meeting current IRB and FDA requirements

Background

Customizable orthopaedic implants are often needed for patients with primary malignant bone tumors due to unique anatomy or complex mechanical problems. Currently, obtaining customizable orthopaedic implants for orthopaedic oncology patients can be an arduous task involving submitting approval requests to the Institutional Review Board (IRB) and the Food and Drug Administration (FDA). There is great potential for the delay of a patient’s surgery and unnecessary paperwork if the submission pathways are misunderstood or a streamlined protocol is not in place.

Purpose

The objective of this study was to review the existing FDA custom implant approval pathways and to determine whether this process was improved with an institutional protocol.

Methods

An institutional protocol for obtaining IRB and FDA approval for customizable orthopaedic implants was established with the IRB at our institution in 2013. This protocol was approved by the IRB, such that new patients only require submission of a modification to the existing protocol with individualized patient information. During the two-year period of 2013–2014, eight patients were retrospectively identified as having required customizable implants for various orthopaedic oncology surgeries. The dates of request for IRB approval, request for FDA approval, and total time to surgery were recorded, along with the specific pathway utilized for FDA approval.

Results

The average patient age was 12 years old (7–21 years old). The average time to IRB approval of a modification to the pre-approved protocol was 14 days (7–21 days). Average time to FDA approval after submission of the IRB approval to the manufacturer was 12.5 days (7–19 days). FDA approval was obtained for all implants as compassionate use requests in accordance with Section 561 of the Federal Food Drug and Cosmetic Act’s expanded access provisions.

Conclusions

Establishment of an institutional protocol with pre-approval by the IRB can expedite the otherwise time-consuming and complicated process of obtaining customizable orthopaedic implants for orthopaedic oncology patients.

Level of evidence

Retrospective case series, Level IV. See the Guidelines for authors for a complete description of levels of evidence.

Designer, acidic biochar influences calcareous soil characteristics

In a proof-of-concept study, an acidic (pH 5.8) biochar was created using a low pyrolysis temperature (350 °C) and steam activation (800 °C) to potentially improve the soil physicochemical status of an eroded calcareous soil. Biochar was added at 0%, 1%, 2%, and 10% (by wt.) and soils were destructively sampled at 1, 2, 3, 4, 5, and 6 month intervals. Soil was analyzed for gravimetric water content, pH, NO3-N, plant-available Fe, Zn, Mn, Cu, and P, organic C, CO2 respiration, and microbial enumeration via extractable DNA and 16S rRNA gene copies. Gravimetric soil water content increased with biochar application regardless of rate, as compared to the control. Soil pH decreased between 0.2 and 0.4 units, while plant-available Zn, Mn, and P increased with increasing biochar application rate. Micronutrient availability decreased over time likely due to insoluble mineral species precipitation. Increasing biochar application raised the soil organic C content and remained elevated over time. Increasing biochar application rate also increased respired CO2, yet the CO2 released decreased over time. Soil NO3-N concentrations significantly decreased with increasing biochar application rate likely due to microbial immobilization or denitrification. Depending on application rate, biochar produced a 1.4 to 2.1-fold increase in soil DNA extracted and 1.4- to 2.4-fold increase in 16S rRNA gene abundance over control soils, suggesting microbial stimulation and a subsequent burst of activity upon biochar addition. Our results showed that there is promise in designing a biochar to improve the quality and water relations of eroded calcareous soils.

Hardwood biochar and manure co-application to a calcareous soil

Biochar may affect the mineralization rate of labile organic C sources such as manures via microbial community shifts, and subsequently affect nutrient release. In order to ascertain the positive or negative priming effect of biochar on manure, dairy manure (2% by wt.) and a hardwood-based, fast pyrolysis biochar were applied (0%, 1%, 2%, and 10% by wt.) to a calcareous soil. Destructive sampling occurred at 1, 2, 3, 4, 6 and 12 months to monitor for changes in soil chemistry, water content, microbial respiration, bacterial populations, and microbial community structure. Overall results showed that increasing biochar application rate improved the soil water content, which may be beneficial in limited irrigation or rainfall areas. Biochar application increased soil organic C content and plant-available Fe and Mn, while a synergistic biochar-manure effect increased plant-available Zn. Compared to the other rates, the 10% biochar application lowered concentrations of NO3-N; effects appeared masked at lower biochar rates due to manure application. Over time, soil NO3-N increased likely due to manure N mineralization, yet soil NO3-N in the 10% biochar rate remained lower as compared to other treatments. In the presence of manure, only the 10% biochar application caused subtle microbial community structure shifts by increasing the relative amounts of two fatty acids associated with Gram-negative bacteria and decreasing Gram-positive bacterial fatty acids, each by ∼1%. Our previous findings with biochar alone suggested an overall negative priming effect with increasing biochar application rates, yet when co-applied with manure the negative priming effect was eliminated.

Desmoplastic fibroma of the distal radius: an interesting case and a review of the literature and therapeutic implications

Desmoplastic fibromas are rare, benign, locally aggressive bone tumors, which arise primarily in patients younger than 30 years old. Historically, even with greater functional loss, en bloc or wide resection of the tumors to prevent local recurrence has been the method of choice in treatment. This article discusses the presentation of a 10-year-old male who presented with a mass in the distal forearm, after reporting difficulty in pronation and supination. The patient was ultimately treated with wide resection and allo-arthrodesis with allograft. Post-operatively, the patient has exhibited excellent recovery, including normal range of motion at the shoulder and elbow, and ability to perform all activities of daily livings despite reduced grip strength compared with the contralateral side.

Copper and zinc speciation in a biosolids-amended, semiarid grassland soil

Predicting trace-metal solid-phase speciation changes associated with long-term biosolids land application is important for understanding and improving environmental quality. Biosolids were surface-applied (no incorporation; 0, 2.5, 5, 10, 21, and 30 Mg ha) to a semiarid grassland in 1991 (single application) and 2002 (repeated application). In July 2003, soils were obtained from the 0- to 8-, 8- to15-, and 15- to 30-cm depths in all plots. Using soil pH, soluble anion and cation concentrations from 0.01 mol L CaCl extractions, dissolved organic C (DOC) content, and an estimate of solid phase humic and fulvic acids present, Cu and Zn associated with minerals, hydrous ferric oxides (HFO), organically complexed, electrostatically bound to organic matter (OM), or DOC phases was modeled using Visual Minteq. Scanning electron microscopy and energy-dispersive X-ray analysis (SEM-EDXRA) was also used to identify solid-phase metal associations present in single and repeated biosolids-amended soils. Based on soil solution chemistry in all depths, as modeled using Visual Minteq, >90% of the Cu and >95% of the Zn from the single or repeated biosolids-applied soils were sorbed electrostatically or as mono- or bidentate solid-phase OM complexes. Up to 10 and 5% of the Cu and Zn, respectively, was associated with HFO, with negligible amounts associated with DOC. The SEM-EDXRA of clay-sized separates from all soil depths led to direct observation of Fe-Cu and Fe-Zn associations. Results implied that after surface-applying biosolids either once or twice with up to 30 Mg ha, some shifts occurred in phases controlling Cu and Zn solubility, but solution concentrations remained below drinking water standards.

Hardwood biochar influences calcareous soil physicochemical and microbiological status

The effects of biochar application to calcareous soils are not well documented. In a laboratory incubation study, a hardwood-based, fast pyrolysis biochar was applied (0, 1, 2, and 10% by weight) to a calcareous soil. Changes in soil chemistry, water content, microbial respiration, and microbial community structure were monitored over a 12-mo period. Increasing the biochar application rate increased the water-holding capacity of the soil-biochar blend, a trait that could be beneficial under water-limited situations. Biochar application also caused an increase in plant-available Fe and Mn, soil C content, soil respiration rates, and bacterial populations and a decrease in soil NO-N concentration. Biochar rates of 2 and 10% altered the relative proportions of bacterial and fungal fatty acids and shifted the microbial community toward greater relative amounts of bacteria and fewer fungi. The ratio of fatty acid 19:0 cy to its precursor, 18:1ω7c, was higher in the 10% biochar rate soil than in all other soils, potentially indicating an environmental stress response. The 10% application rate of this particular biochar was extreme, causing the greatest change in microbial community structure, a physiological response to stress in Gram-negative bacteria, and a drastic reduction in soil NO-N (85-97% reduction compared with the control), all of which were sustained over time.

Investigation of copper sorption by sugar beet processing lime waste

In the western United States, sugar beet processing for sugar recovery generates a lime-based waste product (∼250,000 Mg yr) that has little liming value in the region's calcareous soils. This area has recently experienced an increase in dairy production, with dairies using copper (Cu)-based hoof baths to prevent hoof diseases. A concern exists regarding soil Cu accumulation because spent hoof baths may be disposed of in waste ponds, with pond waters being used for irrigation. The objective of this preliminary study was to evaluate the ability of lime waste to sorb Cu. Lime waste was mixed with increasing Cu-containing solutions (up to 100,000 mg Cu kg lime waste) at various buffered pH values (pH 6, 7, 8, and 9) and shaken over various time periods (up to 30 d). Copper sorption phenomenon was quantified using sorption maximum fitting, and the sorption mechanism was investigated using X-ray absorption spectroscopy. Results showed that sorption onto lime waste increased with decreasing pH and that the maximum Cu sorption of ∼45,000 mg kg occurred at pH 6. X-ray absorption spectroscopy indicated that Cu(OH) was the probable species present, although the precipitate existed as small multinuclear precipitates on the surface of the lime waste. Such structures may be precursors for larger surface precipitates that develop over longer incubation times. Findings suggest that sugar beet processing lime waste can viably sorb Cu from liquid waste streams, and thus it may have the ability to remove Cu from spent hoof baths.

Macroscopic and molecular investigations of copper sorption by a steam-activated biochar

Excessive Cu concentrations in water systems can negatively affect biological systems. Because Cu can form strong associations with organic functional groups, we examined the ability of biochar (an O-C-enriched organic bioenergy by-product) to sorb Cu from solution. In a batch experiment, KOH steam-activated pecan shell biochar was shaken for 24 h in pH 6, 7, 8, or 9 buffered solutions containing various Cu concentrations to identify the effect of pH on biochar Cu sorption. Afterward, all biochar solids from the 24-h shaking period were air-dried and analyzed using X-ray absorption fine structure (XAFS) spectroscopy to determine solid-phase Cu speciation. In a separate batch experiment, biochar was shaken for 30 d in pH 6 buffered solution containing increasing Cu concentrations; the Cu sorption maximum was calculated based on the exponential rise to a maximum equation. Biochar sorbed increasing amounts of Cu as the solution pH decreased from 9 to 6. The XAFS spectroscopy revealed that Cu was predominantly sorbed onto a biochar organic phase at pH 6 in a molecular structure similar to Cu adsorbed on model humic acid (Cu-humic acid [HA]). The XAFS spectra at pH 7, 8, and 9 suggested that Cu was associated with the biochar as three phases: (i) a complex adsorbed on organic ligands similar to Cu-HA, (ii) carbonate phases similar to azurite (Cu(CO)(OH)), and (iii) a Cu oxide phase like tenorite (CuO). The exponential rise equation fit to the incubated samples predicted a Cu sorption maximum of 42,300 mg Cu kg. The results showed that KOH steam-activated pecan shell biochar could be used as a material for sorbing excess Cu from water systems, potentially reducing the negative effects of Cu in the environment.

Switchgrass biochar affects two aridisols

The use of biochar has received growing attention because of its ability to improve the physicochemical properties of highly weathered Ultisols and Oxisols, yet very little research has focused on its effects in Aridisols. We investigated the effect of low or high temperature (250 or 500°C) pyrolyzed switchgrass () biochar on two Aridisols. In a pot study, biochar was added at 2% w/w to a Declo loam (Xeric Haplocalcids) or to a Warden very fine sandy loam (Xeric Haplocambids) and incubated at 15% moisture content (by weight) for 127 d; a control (no biochar) was also included. Soils were leached with 1.2 to 1.3 pore volumes of deionized HO on Days 34, 62, 92, and 127, and cumulative leachate Ca, K, Mg, Na, P, Cu, Fe, Mn, Ni, Zn, NO-N, NO-N, and NH-N concentrations were quantified. On termination of the incubation, soils were destructively sampled for extractable Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Zn, NO-N, and NH-N, total C, inorganic C, organic C, and pH. Compared with 250°C, the 500°C pyrolysis temperature resulted in greater biochar surface area, elevated pH, higher ash content, and minimal total surface charge. For both soils, leachate Ca and Mg decreased with the 250°C switchgrass biochar, likely due to binding by biochar's functional group sites. Both biochars caused an increase in leachate K, whereas the 500°C biochar increased leachate P. Both biochars reduced leachate NO-N concentrations compared with the control; however, the 250°C biochar reduced NO-N concentrations to the greatest extent. Easily degradable C, associated with the 250°C biochar's structural make-up, likely stimulated microbial growth, which caused NO-N immobilization. Soil-extractable K, P, and NO-N followed a pattern similar to the leachate observations. Total soil C content increases were linked to an increase in organic C from the biochars. Cumulative results suggest that the use of switchgrass biochar prepared at 250°C could improve environmental quality in calcareous soil systems by reducing nutrient leaching potential.

Biochar and manure affect calcareous soil and corn silage nutrient concentrations and uptake

Carbon-rich biochar derived from the pyrolysis of biomass can sequester atmospheric CO, mitigate climate change, and potentially increase crop productivity. However, research is needed to confirm the suitability and sustainability of biochar application to different soils. To an irrigated calcareous soil, we applied stockpiled dairy manure (42 Mg ha dry wt) and hardwood-derived biochar (22.4 Mg ha), singly and in combination with manure, along with a control, yielding four treatments. Nitrogen fertilizer was applied when needed (based on preseason soil test N and crop requirements) in all plots and years, with N mineralized from added manure included in this determination. Available soil nutrients (NH-N; NO-N; Olsen P; and diethylenetriaminepentaacetic acid-extractable K, Mg, Na, Cu, Mn, Zn, and Fe), total C (TC), total N (TN), total organic C (TOC), and pH were evaluated annually, and silage corn nutrient concentration, yield, and uptake were measured over two growing seasons. Biochar treatment resulted in a 1.5-fold increase in available soil Mn and a 1.4-fold increase in TC and TOC, whereas manure produced a 1.2- to 1.7-fold increase in available nutrients (except Fe), compared with controls. In 2009 biochar increased corn silage B concentration but produced no yield increase; in 2010 biochar decreased corn silage TN (33%), S (7%) concentrations, and yield (36%) relative to controls. Manure produced a 1.3-fold increase in corn silage Cu, Mn, S, Mg, K, and TN concentrations and yield compared with the control in 2010. The combined biochar-manure effects were not synergistic except in the case of available soil Mn. In these calcareous soils, biochar did not alter pH or availability of P and cations, as is typically observed for acidic soils. If the second year results are representative, they suggest that biochar applications to calcareous soils may lead to reduced N availability, requiring additional soil N inputs to maintain yield targets.