Fog Water Collection Effectiveness: Mesh Intercomparisons

Abstract

To explore fog water harvesting potential in California, we conducted long-term measurements involving three types of mesh using standard fog collectors (SFC). Volumetric fog water measurements from SFCs and wind data were collected and recorded in 15-minute intervals over three summertime fog seasons (2014)(2015)(2016) at four California sites. SFCs were deployed with: standard 1.00 m 2 double-layer 35% shade coefficient Raschel; stainless steel mesh coated with the MIT-14 hydrophobic formulation; and FogHa-Tin, a German manufactured, 3-dimensional spacer fabric deployed in two orientations. Analysis of 3419 volumetric samples from all sites showed strong relationships between mesh efficiency and wind speed. Raschel mesh collected 160% more fog water than FogHa-Tin at wind speeds less than 1 m s -1 and 45% less for wind speeds greater than 5 m s -1 . MIT-14 coated stainless-steel mesh collected more fog water than Raschel mesh at all wind speeds. At low wind speeds of < 1 m s -1 the coated stainless steel mesh collected 3% more and at wind speeds of 4-5 m s -1 , it collected 41% more. FogHa-Tin collected 5% more fog water when the warp of the weave was oriented vertically, per manufacturer specification, than when the warp of the weave was oriented horizontally. Time series measurements of three distinct mesh across similar wind regimes revealed inconsistent lags in fog water collection and inconsistent performance. Since such differences occurred under similar wind-speed regimes, we conclude that other factors play important roles in mesh performance, including in-situ fog event and aerosol dynamics that affect droplet-size spectra and droplet-to-mesh surface interactions.

Atmospheric mercury deposition over the land surfaces and the associated uncertainties in observations and simulations: a critical review

“…There have been numerous forest Hg deposition studies in the recent decade in East Asia with the second highest average litterfall Hg deposition flux (35.5 ± 27.7 µg m −2 yr −1 ) (Wan et al, 2009;Wang et al, 2009;Fu et al, 2010aFu et al, , b, 2016aGong et al, 2014;Luo et al, 2016;Ma et al, 2015Ma et al, , 2016Han et al, 2016;Wang et al, 2016b;Zhou et al, 2016Zhou et al, , 2017. Lower levels of litterfall Hg deposition fluxes were found in North America (12.3 ± 4.9 µg m −2 yr −1 ) and Europe (14.4 ± 5.8 µg m −2 yr −1 ) (Larssen et al, 2008;Obrist et al, 2009Obrist et al, , 2012Fisher and Wolfe, 2012;Juillerat et al, 2012;Risch and Kenski, 2018;Risch et al, 2012Risch et al, , 2017Benoit et al, 2013;Navrátil et al, 2014;Gerson et al, 2017). Throughfall Hg deposition is another important way for Hg input in forests.…”

“…where F litterfall is the litterfall Hg deposition flux; E A is the litterfall trap area expansion factor (note: leaves outside the area above the trap could fall into the trap due to horizontal air fluctuation); C l is the Hg mass concentration in litterfall; M l is the total dry weight of litterfall; A is the litterfall trap area; and t is the sampling time. Litterfall samples are collected during the leaf-growing or -falling seasons with litterfall traps or collectors (Fisher and Wolfe, 2012). Total litterfall consists of leaves and needles, woody material such as twigs and bark, and reproductive bodies such as flowers, seeds, fruits, and nuts (Meier et al, 2006;Risch et al, 2012).…”

“…The Hg content in litterfall can be determined by thermal decomposition, amalgamation, and cold vapor atomic absorption spectrophotometry (CVAAS) following EPA Method 7473 (Richardson and Friedland, 2015;Fu et al, 2016a;Zhou et al, 2017;Risch et al, 2017). Alternatively, the litterfall samples can be digested and analyzed following EPA Method 1631E (Fu et al, 2010a;Fisher and Wolfe, 2012). The uncertainty in litterfall Hg content analysis is about ±7 % according to the Litterfall Mercury Monitoring Network developed by NADP (Risch et al, 2017) and individual studies (Benoit et al, 2013;Ma et al, 2015;Zhou et al, 2016;Gerson et al, 2017).…”

Hydrologic Resilience from Summertime Fog and Recharge: A Case Study for Coho Salmon Recovery Planning

“…Fogdrip is typically collected using an impacting surface such as a 1m 2 mesh in a stiff frame or threads on a cylindrical harp suspended above ground on top of a collecting trough funneling fog water into a tipping bucket rain gauge (Goodman 1985;Fischer and Still 2007;Fernandez et al 2018). Fogdrip is also collected using an arrangement of rain troughs radiating from a bucket positioned under a tree canopy (Sawaske and Freyberg 2015).…”

“…Fog droplets impact on surfaces such as redwood or pine needles, coalesce, and drip. Volumetric collection efficiency of surfaces varies and depends on impaction dynamics, relative wind, aerosol chemistry, surface hydroscopic characteristics, and fog droplet size (de Dios Rivera 2011; Regalado and Ritter 2016;Fernandez et al 2018). Fog water deposition is an important source of water to coastal ecosystems, constituting 30%-40% or more of total water input for redwood forests (Harr 1982;Burgess and Dawson 2004), up to 44% for Bishop pine forests (Fischer et al 2009), and during summer drought, 28%-66% for coastal prairie grasses (Corbin et al 2005).…”