Characterizing copper and zinc content in forested wetland soils of North Carolina, USA.

Wetlands are often located in landscape positions where they receive runoff or floodwaters, which may contain toxic trace metals and other pollutants from anthropogenic sources. Over time, this can lead to the accumulation of potentially harmful levels of metals in wetlands soils. To assess the potential risk of Cu and Zn buildup in wetland soils in North Carolina, soil data from 88 wetlands were analyzed. In a subset of 16 wetlands, more intensive sampling was conducted. Samples were analyzed for Mehlich 3 Cu and Zn, and a subset of the samples was analyzed for total Cu and Zn. Overall, Mehlich 3 Cu and Zn were low, with mean values of 0.9 mg/kg for Cu and 3.2 mg/kg for Zn. Warning levels for Mehlich 3 Zn were only exceeded in three of the 88 sites; elevated Mehlich Cu was not observed. Total Cu and Zn were also low, with only a few sites having elevated levels; however, there was not a strong linear relationship between Mehlich 3 and total metals. Mean levels of Mehlich 3 Cu and Zn in wetlands were much lower than for human-impacted upland soils and background threshold concentrations that might be indicative of disturbance were much lower than warning levels for agricultural soils. The very low mobile Zn and Cu in most of these wetlands indicated that these metals do not pose a risk to the biota in most North Carolina wetlands, but wetlands with a direct and significant anthropogenic source of metal contamination could be exceptions.

Cooled Radiofrequency Ablation of the Articular Sensory Branches of the Obturator and Femoral Nerves using Fluoroscopy and Ultrasound Guidance: A Large Retrospective Study.

BACKGROUND: We previously reported on a combined technique and initial data of hip denervation using an anterior approach and cooled radiofrequency. OBJECTIVES: A large retrospective study to evaluate the long-term effectiveness of cooled radiofrequency ablation (CRFA) in the general chronic hip pain population. STUDY DESIGN: Retrospective electronic chart review. SETTING: A single specialty private practice. METHODS: Retrospective chart review of 235 consecutive (CRFA) in 136 patients with chronic hip pain. RESULTS: Out of 235 CRFA, 178 (96 initial procedures and 82 repeats) were performed in 84 patients with 12 or more months follow-up. The average decrease in visual analog scale (VAS) pain scores was 7.3 ± 1.3 to 2.3 ± 1.5 and 2.48 ± 1.5 for the first and second diagnostic block, respectively, and was statistically significant (P < 0.001). Similarly, the average decrease in VAS pain scores at 6 and 12 months after CRFA denervation was 3.44 ± 2.5 and 4.23 ± 2.5, respectively; P < 0.001. Out of the 96 initial procedures in 84 patients, 66 procedures (69%) provided more than 50% relief at 6 months, and 50 (52%) at 12 months. There were 82 repeat denervations in 36 patients. Repeated procedures in the same patients provided a similar degree of pain relief with no statistically significant difference in the median pain scores (2.8 ± 2.1 cm vs 3.1 ± 1.7 cm ; P = 0.197) or time interval of pain relief (12.7 ± 10.9 vs 10.3 ± 4.7;  P = 0.508). There were 3 minor complications. LIMITATIONS: Retrospective nature of the study. CONCLUSION: Improvements in pain scores and longevity of pain relief from chronic hip pain using a simple, anterior approach to radiofrequency denervation of the lateral obturator and lateral femoral nerves justifies further randomized prospective trials. Repeated CRFAs demonstrated consistency in pain relief and absolute safety of repeated denervation.

A Review of Peripheral Nerve Stimulation Techniques Targeting the Medial Branches of the Lumbar Dorsal Rami in the Treatment of Chronic Low Back Pain.

OBJECTIVES: The lumbar medial branch nerve has historically been a focus for ablative techniques in the treatment of chronic low back pain (CLBP) of facetogenic origin. Recent developments in the field of neuromodulation have been employed to target these nerves for analgesia and/or functional restoration in broader populations of CLBP patients. The objective of this article was to provide an introductory review of procedural techniques and devices employed for peripheral nerve stimulation (PNS) of the lumbar medial branch of the dorsal ramus for the treatment of CLBP. METHODS: A literature search via PubMed.gov was performed through September 2019 with key words focusing on peripheral nerve stimulation for chronic low back pain. This was refined to include only those articles that focused specifically on stimulation of the lumbar medial branch of the dorsal ramus. References within selected articles and unpublished data currently in the peer review process were also utilized. RESULTS: Ninety articles from PubMed.gov were obtained. Two approaches to PNS of the medial branch of the dorsal ramus were identified. CONCLUSIONS: Our review of the current literature regarding techniques for neuromodulation of the medial branch of the dorsal ramus revealed two dominant methods: a temporarily implanted percutaneous coiled-lead approach and a permanently implanted system. The two techniques share some similarities, such as targeting the medial branch of the dorsal ramus, and also have some differences, such as indwelling time, stimulation parameters, duration of treatment, image guidance, and degrees of invasiveness, but they are both demonstrating promising results in clinical trials.

Long-Term Retrospective Assessment of Clinical Efficacy of Radiofrequency Ablation of the Knee Using a Cooled Radiofrequency System.

BACKGROUND: Cooled radiofrequency ablation (CRFA) in a randomized, prospective study demonstrated significantly greater improvements in pain, functional, and global outcome measures. OBJECTIVES: This large, real-life, retrospective study evaluated the long-term effectiveness of CRFA in the general chronic knee pain population. STUDY DESIGN: Retrospective electronic chart review. SETTING: Outpatient private practice. METHODS: After institutional review board approval, we reviewed data of 275 consecutive patients who had undergone a geniculate nerve block at a single-site pain practice between July 1, 2014 and July 1, 2017. A total of 44 patients had a negative response to the geniculate block, and 11 patients had long-term pain relief from the block and declined CRFA. Eight patients underwent knee surgery after the block, and 7 never followed up for further treatment. Finally, 205 patients had undergone CRFA, and 183 (89%) of them returned to provide data. RESULTS: The average age of the 183 patients was 61 (28-95) years, body mass index 34 (18.5-57), and there were 105 women and 78 men. A total of 137 patients had unilateral knee pain, whereas 46 patients had bilateral knee pain. Eighty percent (146/183) reported at least one or more additional sources of chronic pain (back, shoulder, and others). The average opioid use at baseline was 50 mg morphine sulfate equivalents (median 30 mg). The average baseline pain scores were 8.5, which decreased to 2.2 after the geniculate local anesthetic block, and to 4.2 after CRFA. A total of 65% of the patients claimed > 50% pain relief, whereas 77% had 2 or more Visual Analog Scale points decrease, and 26 (14%) patients reported no pain at all after CRFA. The mean duration of > 50% pain relief after CRFA was 12.5 months (range 0-35 months). There was no significant decrease of opioid use. Patients who underwent a repeated procedure (n = 43) achieved a similar pain relief (P = 0.402). We could not find a statistical difference in geniculate CRFA outcomes between the group who had total knee arthroplasty (TKA; n = 21) and maintained chronic knee pain and patients who had no prior surgery (P = 0.542). LIMITATIONS: Retrospective nature of the study. CONCLUSIONS: This study demonstrates the clinical effectiveness of CRFA in the treatment of chronic knee pain from osteoarthritis, and even in those patients who maintained chronic knee pain after TKA. Our real-life data seems to agree with data previously published in a randomized controlled trial, despite the fact that this was quite a heterogenous patient population with various sources of chronic pain. KEY WORDS: Radiofrequency ablation, chronic knee pain, knee osteoarthritis.

Addressing the fouling of in situ ultraviolet-visual spectrometers used to continuously monitor water quality in brackish tidal marsh waters.

The introduction of portable in situ ultraviolet-visual spectrometers has made possible the collection of water quality parameters at a high frequency in dynamic systems such as tidal marshes. The usefulness of this technology is inhibited by fouling of the instrument's optics. In this study, a spectrometer fitted with manufacturer-recommended compressed air optical cleaning was installed in a brackish marsh to determine if fouling interfered with measurements between bi-weekly servicing. During a 2-wk period, the absorbance measured in air at 220 nm increased from 9 to 549 m, indicating major fouling. An antifouling system was developed that reduced the time of exposure of the optics to stream water and used a pressurized fresh water cleaning. After implementation of the system, the absorbance in air increased to at most 63 m after 2 wk of data collection. The dramatic reduction in fouling will allow quality long-term data to be collected using this technology.

Relationships between nitrogen transformation rates and gene abundance in a riparian buffer soil.

Denitrification is a critical biogeochemical process that results in the conversion of nitrate to volatile products, and thus is a major route of nitrogen loss from terrestrial environments. Riparian buffers are an important management tool that is widely utilized to protect water from non-point source pollution. However, riparian buffers vary in their nitrate removal effectiveness, and thus there is a need for mechanistic studies to explore nitrate dynamics in buffer soils. The objectives of this study were to examine the influence of specific types of soluble organic matter on nitrate loss and nitrous oxide production rates, and to elucidate the relationships between these rates and the abundances of functional genes in a riparian buffer soil. Continuous-flow soil column experiments were performed to investigate the effect of three types of soluble organic matter (citric acid, alginic acid, and Suwannee River dissolved organic carbon) on rates of nitrate loss and nitrous oxide production. We found that nitrate loss rates increased as citric acid concentrations increased; however, rates of nitrate loss were weakly affected or not affected by the addition of the other types of organic matter. In all experiments, rates of nitrous oxide production mirrored nitrate loss rates. In addition, quantitative polymerase chain reaction (qPCR) was utilized to quantify the number of genes known to encode enzymes that catalyze nitrite reduction (i.e., nirS and nirK) in soil that was collected at the conclusion of column experiments. Nitrate loss and nitrous oxide production rates trended with copy numbers of both nir and 16s rDNA genes. The results suggest that low-molecular mass organic species are more effective at promoting nitrogen transformations than large biopolymers or humic substances, and also help to link genetic potential to chemical reactivity.

Substrate organic matter to improve nitrate removal in surface-flow constructed wetlands.

A wetland mesocosm experiment was conducted in eastern North Carolina to determine if organic matter (OM) addition to soils used for in-stream constructed wetlands would increase NO3--N treatment. Not all soils are suitable for wetland substrate, so OM addition can provide a carbon and nutrient source to the wetland early in its development to enhance denitrification and biomass growth. Four batch studies, with initial NO3--N concentrations ranging from 30 to 120 mg L-1, were conducted in 2002 in 21 surface-flow wetland mesocosms. The results indicated that increasing the OM content of a Cape Fear loam soil from 50 g kg-1 (5% dry wt.) to 110 g kg-1 (11% dry wt.) enhanced NO3--N wetland treatment efficiency in spring and summer batch studies, but increases to 160 g kg-1 (16% dry wt.) OM did not. Wetlands constructed with dredged material from the USACE Eagle Island Confined Disposal Facility in Wilmington, NC, with initial OM of 120 g kg-1 (12% dry wt.), showed no improvement in NO3--N treatment efficiency when increased to 180 g kg-1 (18% dry wt.), but did show increased NO3--N treatment efficiency in all batch studies when increased to 220 g kg-1 (22% dry wt.). Increased OM addition and biosolids to the Cape Fear loam and dredged material blends significantly increased biomass growth in the second growing season when compared to no OM addition. Results of this research indicate that increased OM in the substrate will reduce the area required for in-stream constructed wetlands to treat drainage water in humid regions. It also serves as a demonstration of how dredged material can be used successfully in constructed wetlands, as an alternative to costly storage by the USACE.