Sediment-Water Interactions Affecting Dissolved-Mercury Distributions in Camp Far West Reservoir, California

Field and laboratory studies were conducted in April and November 2002 to provide the first direct measurements of the benthic flux of dissolved (0.2-micrometer filtered) mercury species (total and methylated forms) between the bottom sediment and water column at three sampling locations within Camp Far West Reservoir, California: one near the Bear River inlet to the reservoir, a second at a mid-reservoir site of comparable depth to the inlet site, and the third at the deepest position in the reservoir near the dam (herein referred to as the inlet, midreservoir and near-dam sites, respectively; Background, Fig. 1). Because of interest in the effects of historic hydraulic mining and ore processing in the Sierra Nevada foothills just upstream of the reservoir, dissolved-mercury species and predominant ligands that often control the mercury speciation (represented by dissolved organic carbon, and sulfides) were the solutes of primary interest. Benthic flux, sometimes referred to as internal recycling, represents the transport of dissolved chemical species between the water column and the underlying sediment. Because of the affinity of mercury to adsorb onto particle surfaces and to form insoluble precipitates (particularly with sulfides), the mass transport of mercury in mining-affected watersheds is typically particle dominated. As these enriched particles accumulate at depositional sites such as reservoirs, benthic processes facilitate the repartitioning, transformation, and transport of mercury in dissolved, biologically reactive forms (dissolved methylmercury being the most bioavailable for trophic transfer). These are the forms of mercury examined in this study. In contrast to typical scientific manuscripts, this report is formatted in a pyramid-like structure to serve the needs of diverse groups who may be interested in reviewing or acquiring information at various levels of technical detail (Appendix 1). The report enables quick transitions between the initial summary information (figuratively at the top of the pyramid) and the later details of methods or results (figuratively towards the base of the pyramid) using hyperlinks to supporting figures and tables, and an electronically linked Table of Contents. During two sampling events, two replicate sediment cores (Coring methods; Fig. 2) from each of three reservoir locations (Fig. 1) were used in incubation experiments to provide flux estimates and benthic biological characterizations. Incubation of these cores provided “snapshots” of solute flux across the sediment-water interface in the reservoir, under benthic, environmental conditions representative of the time and place of collection. Ancillary data, including nutrient and ligand fluxes, were gathered to provide a water-quality framework from which to compare the results for mercury

Kasvikuitupohjaisten lämmöneristemateriaalien kosteustekninen toiminta

Opinnäytetyön tarkoituksena oli perehtyä rakenteiden sekä tiettyjen kasvikuitueristemateriaalien lämpö- ja kosteustekniseen toimintaan ja koota aiheesta kirjallisuusselvitys tukemaan opinnäytetyön toisena osana toimivaa laskentaa. Kasvikuitueristeiden toiminnan perustana on materiaalien suuri hygroskooppisuus, minkä avulla rakenne tasaa kosteutta huokosrakenteeseensa ja mukautuu näin ollen vallitseviin ilmaston kosteusrasituksiin. Käytännössä useimmat kasvikuitueristetyt rakenteet on todettu toimiviksi tavanomaisissa kosteusolosuhteissa, kun rakenteista on tehty kosteusmittauksia sekä rakenneavauksia. Laskennallisella tarkastelulla on toisaalta havaittu kosteuden aiheuttamia riskejä, kuten kohtalaisen korkeaa homehtumisriskiä rakenteen ulkokerroksissa. Näin ollen laskentatulokset ovat osittain ristiriitaisia käytännön kokemuksiin sekä kokeellisesti mitattuihin arvoihin verrattaessa. Kirjallisuusselvityksen lisäksi opinnäytetyössä perehdyttiin WUFI Pro 1D -simulointiohjelmalla tuotettuihin laskelmiin kahdesta eri kasvikuitueristeisestä ulkoseinärakenteesta sekä vertailurakenteista. Rakenteiden reunaehtoina simulointilaskennassa käytettiin olemassa olevista rakenteista tuotettuja 7 ja 12 kuukauden mittausdatoja rakenteiden lämpötiloista sekä suhteellisista kosteuksista. Mitatun ilmastotiedon avulla rakenteista selvitettiin mitattujen ja laskennalla tuotettujen arvojen lämpö- ja kosteusteknisiä eroavaisuuksia sekä tutkittiin rakenteiden mahdollista homehtumisriskiä suomalaisen homemallin avulla. Olki- sekä puukuitueristeisen rakenteen toiminta perustuu tarkkaan kosteuden hallintaan rakentamisen aikana ja sen jälkeen. Laskennan mukaan olki- sekä puukuitueristeisen seinän homehtumisriski on olemassa, mitä korkeammat rakenteiden alkuolosuhteiden suhteelliset kosteudet ovat. Tutkittaessa laskennallisesti rakenteiden toimivuutta on kuitenkin huomioitava laskennan ja mittauksen tuomat rajoitteet sekä virhetekijät, jotka vaikuttavat vertailtaviin tuloksiin. Laskennallisen tarkastelun perusteella voidaan varmistua rakenteen kosteusteknisestä toimivuudesta vain, jos rakenteessa käytettyjen materiaalien ominaisuudet ovat riittävän hyvin tiedossa. Laskelmia tuleekin pitää lähinnä suuntaan antavina, joiden avulla pystytään arvioimaan rakenteiden kosteusteknisen toiminnan riskitekijöitä. Laskennalla tulisi varmistaa rakenteiden kosteustekninen toimivuus, etenkin kun rakenne eroaa yleisistä ohjeistuksista, tai kun rakenteen toimivuudesta ei ole käytännön kokemuksia.The purpose of the research was to study and gather existing information about the moisture physical behavior of structures, and investigate moisture condensation and mold growth of two organic thermal insulation structures. The purpose was to find the differences between the measured values and the results of the calculation for the heat and moisture behavior of the structures. The study was commissioned by Vahanen Rakennusfysiikka Oy. In this research, the simulation of heat and moisture transference for the two different structures were made by using WUFI Pro 1 -dimensional transient heat and moisture modeling program and mold growth with Finnish mold index program. The moisture physical behaviors of selected structures were analyzed numerically under the climate conditions of Finland and using typical interior conditions of living spaces. The starting point of the calculation was to find the differences between the measurements result by using a variety of material properties and by changing the initial conditions of the structures. The results of this research show, that structures which thermal insulations has used plant-fibre based materials are sensitive to biological damage by moisture. The use of porous thermal insulation materials is based on moisture equilibrium of the structure. Excess moisture in a structure causes condensation to structural layers, like the inside surface of the air barrier or wind protection if the moisture cannot evaporate out of the structure simultaneously. In order that the moisture content of the porous structure stays in balance, the structure’s water vapor resistance should decrease from the inside out. Calculations can only be used as direction of moisture behavior because of calculation error factors. Computational insurance should be done for the structures that differ from the general instructions and for the structures which have no practical experience

Environmental Factors Affecting Mercury in Camp Far West Reservoir, California, 2001–03

This report documents water quality in Camp Far West Reservoir from October 2001 through August 2003. The reservoir, located at approximately 300 feet above sea level in the foothills of the northwestern Sierra Nevada, California, is a monomictic lake characterized by extreme drawdown in the late summer and fall. Thermal stratification in summer and fall is coupled with anoxic conditions in the hypolimnion. Water-quality sampling was done at approximately 3-month intervals on eight occasions at several stations in the reservoir, including a group of three stations along a flow path in the reservoir: an upstream station in the Bear River arm (principal tributary), a mid-reservoir station in the thalweg (pre-reservoir river channel), and a station in the deepest part of the reservoir, in the thalweg near Camp Far West Dam. Stations in other tributary arms of the reservoir included those in the Rock Creek arm of the reservoir, a relatively low-flow tributary, and the Dairy Farm arm, a small tributary that receives acidic, metal-rich drainage seasonally from the inactive Dairy Farm Mine, which produced copper, zinc, and gold from underground workings and a surface pit. Several water-quality constituents varied significantly by season at all sampling stations, including major cations and anions, total mercury (filtered and unfiltered samples), nitrogen (ammonia plus organic), and total phosphorus. A strong seasonal signal also was observed for the sulfur-isotope composition of aqueous sulfate from filtered water. Although there were some spatial differences in water quality, the seasonal variations were more profound. Concentrations of total mercury (filtered and unfiltered water) were highest during fall and winter; these concentrations decreased at most stations during spring and summer. Anoxic conditions developed in deep parts of the reservoir during summer and fall in association with thermal stratification. The highest concentrations of methylmercury in unfiltered water were observed in samples collected during summer from deep-water stations in the anoxic hypolimnion. In the shallow (less than 14 meters depth) oxic epilimnion, concentrations of methylmercury in unfiltered water were highest during the spring and lowest during the fall. The ratio of methylmercury to total mercury (MeHg/HgT) increased systematically from winter to spring to summer, largely in response to the progressive seasonal decrease in total mercury concentrations, but also to some extent because of increases in MeHg concentrations during summer. Water-quality data for Camp Far West Reservoir are used in conjunction with data from linked studies of sediment and biota to develop and refine a conceptual model for mercury methylation and bioaccumulation in the reservoir and the lower Bear River watershed. It is hypothesized that MeHg is produced by sulfate-reducing bacteria in the anoxic parts of the water column and in shallow bed sediment. Conditions were optimal for this process during late summer and fall. Previous work has indicated that Camp Far West Reservoir is a phosphate-limited system—molar ratios of inorganic nitrogen to inorganic phosphorus in filtered water were consistently greater than 16 (the Redfield ratio), sometimes by orders of magnitude. Therefore, concentrations of orthophosphate were expectedly very low or below detection at all stations during all seasons. It is further hypothesized that iron-reducing bacteria facilitate release of phosphorus from iron-rich sediments during summer and early fall, stimulating phytoplankton growth in the fall and winter, and that the MeHg produced in the hypolimnion and metalimnion is released to the entire water column in the late fall during reservoir destratification (vertical mixing). Mercury bioaccumulation factors (BAF) were computed using data from linked studies of biota spanning a range of trophic position: zooplankton, midge larvae, mayfly nymphs, crayfish, threadfin shad, bluegill, and spotted bass. Significant increases in total mercury in tissue with increasing organism size were observed for all three fish species and for crayfish. The BAF values were computed using the average methylmercury concentration (wet) in biota divided by the arithmetic mean concentration of methylmercury in filtered water (0.04 nanograms per liter). As expected, the BAF values increased systematically with increasing trophic position. Values of BAF were 190,000 for zooplankton; 470,000 to 930,000 for three taxa of invertebrates; 2.7 million for threadfin shad (whole body); 4.2 million for bluegill (fillet); and 10 million for spotted bass (fillet). The BAF values are high compared with those for biota in other reservoirs in northern California and elsewhere, indicating relatively efficient biomagnification of mercury in Camp Far West Reservoir

Unintended consequences of management actions in salt pond restoration: cascading effects in trophic interactions.

Salt evaporation ponds have played an important role as habitat for migratory waterbirds across the world, however, efforts to restore and manage these habitats to maximize their conservation value has proven to be challenging. For example, salinity reduction has been a goal for restoring and managing former salt evaporation ponds to support waterbirds in the South Bay Salt Pond Restoration Project in San Francisco Bay, California, USA. Here, we describe a case study of unexpected consequences of a low-dissolved oxygen (DO) event on trophic interactions in a salt pond system following management actions to reduce salinity concentrations. We document the ramifications of an anoxic event in water quality including salinity, DO, and temperature, and in the response of the biota including prey fish biomass, numerical response by California Gulls (Larus californicus), and chick survival of Forster's Tern (Sterna forsteri). Management actions intended to protect receiving waters resulted in decreased DO concentrations that collapsed to zero for ≥ 4 consecutive days, resulting in an extensive fish kill. DO depletion likely resulted from an algal bloom that arose following transition of the pond system from high to low salinity as respiration and decomposition outpaced photosynthetic production. We measured a ≥ 6-fold increase in biomass of fish dropped on the levee by foraging avian predators compared with weeks prior to and following the low-DO event. California Gulls rapidly responded to the availability of aerobically-stressed and vulnerable fish and increased in abundance by two orders of magnitude. Mark-recapture analysis of 254 Forster's Tern chicks indicated that their survival declined substantially following the increase in gull abundance. Thus, management actions to reduce salinity concentrations resulted in cascading effects in trophic interactions that serves as a cautionary tale illustrating the importance of understanding the interaction of water quality and trophic structure when managing restoration of salt ponds

Model selection table for Forster’s Tern chick daily survival rates.

<p>Model selection table for Forster’s Tern chick daily survival rates.</p

Study location in South San Francisco Bay, California, Alviso Pond A17 (north) and Pond A16 (south).

<p>Arrows indicate the dominant direction of flow from Coyote Creek in the north through the inflow gate to Pond A17, through the uncontrolled internal levee channel into Pond A16, and out the A16 discharge gate in the southeast corner into Alviso Slough. The circle indicates datasonde location; triangles indicate minisonde sampling locations. Forster’s Tern nesting colonies occurred on the four linear islands in the southern part of pond A16. Imagery provided by Landsat 8 and 2005 National Agricultural Imagery Program (NAIP).</p

Chain of events and trophic interactions of Pond A16 concomitant with the low DO and gull intrusion events.

<p>Salinity reduction resulted from management actions during the Initial Stewardship Plan (ISP) of the South Bay Salt Pond Restoration Project in San Francisco Bay.</p

Fine scale water quality and environmental parameters of Pond A16 from 25 July through 25 August 2005.

<p>Water quality conditions from the pond (pale grey line) and weir box (dark grey) datasondes are depicted in the top three panels: Dissolved oxygen (DO; mg L^-1), pH and salinity (PSU), water temperature (°C). Weather conditions are represent in the bottom two panels: air temperature (°C), photosynthetically active radiation (PAR; mol quanta m^-2 s^-2), and wind speed (m s^-1). Data download (circles) and calibration (diamonds) occurred on alternating weeks. Triangles (top two panels) represent ambient South San Francisco Bay water conditions. The DO sensor of both datasondes were fouled and failed to log data from 12–15 August.</p