Improving phosphorus removal in a surface flow wetland and land application system by geochemical augmentation with alum.

Constructed surface flow (SF) wetlands are commonly used for phosphorus (P) removal. Geochemistry of wetlands provides explicit mechanisms for permanent P-sequestration in sediments. This study had two goals: (1) Find P removal performance and rate at the highest alum doses that do not produce floc in an SF wetland; and (2) Determine potential improvements to P removal performance with low alum doses in a 140-ha land application system downstream from the wetland. The study started with a small fraction of a conventional, flocculation/sedimentation alum dose, then progressively increased the dose to observe initiation of floc formation and removal of P. For flows near 10 megaliters per day in an 0.8 ha SF wetland, doses started 189 L d-1 for two weeks, then increasing by 189 L d-1 every two weeks until the final two weeks at 946 L d-1. At an alum dosing rate of 189 L d-1 (alum concentration of 9.5 mg L-1), there was an order of magnitude improvement in P removal rates over literature values. Floc formation in the wetland was observed at 567 L d-1, but no significant improvement in P removal rates were observed until a conventional alum dose of 946 L d-1 was applied. Alum addition improved P removal performance in the land application system. In 2014, during which there was no alum dosing, the median effluent total P (TP) during the July-September dry season (groundwater dominated outflow) was 0.43 mg L-1. In 2015, (alum dosing August-October) median dry weather TP of 0.18 mg L-1 was significantly lower (p < 0.0001). Alum dosing in 2016 at 189 L d-1 produced a dry weather median of 0.28 mg L-1, which was significantly lower (p = 0.015) than in the 2014 median. Mean daily dry weather TP loads to the land application system were 44 kg d-1 in 2014, 45 kg d-1 in 2015, and 41 kg d-1 in 2016.

Practical salinity management for leachate irrigation to poplar trees.

Landfill leachate can be beneficially reused for irrigation of fiber crops with appropriate attention to nutrient and salinity management. The Riverbend Landfill in Western Oregon has been effectively practicing irrigation of landfill leachate to poplar trees since 1993. Over that time, the site has been adaptively managed to control salinity impacts to the tree crop while beneficially utilizing the applied water and nutrients during each growing season. Representative leachate irrigation water has ranged in concentration of total dissolved solids from 777 to 6,940 mg/L, chloride from 180 to 1,760 mg/L and boron from 3.2 to 7.3 mg/L. Annual leachate irrigation applications have also ranged between 102 and 812 mm/yr. Important conclusions from this site have included: 1) Appropriate tree clone selection and tree stand spacing, thinning, and harvest rotations are critical to maintaining a productive tree stand that is resilient and resistant to salt stress. The most effective combinations have included clones DN-34, OP-367, 184-411, 49-177, and 15-29 planted at spacing of 3.7-m x 1.8-m to 3.7-m x 3.7-m; 2) Leaf tissue boron levels are closely correlated to soil boron levels and can be managed with leaching. When leaf tissue boron levels exceed 200 to 250 mg/kg, signs of salt stress may emerge and should be monitored closely; 3) Salinity from leachate irrigation can be managed to sustain a healthy tree crop by controlling mass loading rates and providing appropriate irrigation blending if necessary. Providing freshwater irrigation following each leachate irrigation and targeting freshwater irrigation as 30 percent of total irrigation water applied has successfully controlled salt impacts to vegetation; and 4) Drip irrigation generally requires more careful attention to long-term soil salinity management than spray irrigation. Moving drip irrigation tubes periodically to prevent the formation of highly saline zones within the soil profile is important. In this paper, a fifteen year record of monitoring and operational data are presented that can be used by others in managing irrigation of saline water to poplar trees. When salinity is carefully managed, tree systems can help to provide sustainable leachate management solutions for landfills.

X-linked protocadherin 19 mutations cause female-limited epilepsy and cognitive impairment.

Epilepsy and mental retardation limited to females (EFMR) is a disorder with an X-linked mode of inheritance and an unusual expression pattern. Disorders arising from mutations on the X chromosome are typically characterized by affected males and unaffected carrier females. In contrast, EFMR spares transmitting males and affects only carrier females. Aided by systematic resequencing of 737 X chromosome genes, we identified different protocadherin 19 (PCDH19) gene mutations in seven families with EFMR. Five mutations resulted in the introduction of a premature termination codon. Study of two of these demonstrated nonsense-mediated decay of PCDH19 mRNA. The two missense mutations were predicted to affect adhesiveness of PCDH19 through impaired calcium binding. PCDH19 is expressed in developing brains of human and mouse and is the first member of the cadherin superfamily to be directly implicated in epilepsy or mental retardation.