Environmental assessments: four under-appreciated elements of design

Environmental assessments generate and/or collect individual research efforts to answer policy-relevant questions and otherwise provide technical advice to decision-makers, typically legislators, international negotiators and regulators. Though one might think first of assessments in terms of the reports that they often produce, the implications of scientific assessment are better understood by viewing assessments as a social processes, rather than principally as a document. Assessment processes are embedded in different sorts of institutional settings, within which scientists, decision-makers, and advocates communicate to define relevant questions for analysis, mobilize certain kinds of experts and expertise, and interpret findings in particular ways. This social process perspective on assessment directs attention beyond the content of assessment reports to encompass questions the design of the social process. In this paper, we focus on four elements of assessment design that are too frequently under-appreciated: assessment context and initiation, science–policy interaction, participation in assessment processes, and assessment capacity. We show how widely these elements vary across five different assessments and discuss the implications of this variation.     

DMS and SO2 at Baring Head, New Zealand: Implications for the Yield of SO2 from DMS

Atmospheric dimethyl sulfide (DMS) and sulfur dioxide (SO₂) concentrations were measured at Baring Head, New Zealandduring February and March 2000. Anti-correlated DMS and SO₂ diurnalcycles, consistent with the photochemical production of SO₂ from DMS, were observed in clean southerly air off the ocean. The data is used to infer a yield of SO₂ from DMS oxidation. The estimated yields are highly dependent on assumptions about the DMS oxidation rate. Fitting the measured data in a photochemical box model using model-generated OH levels and the Hynes et al. (1986) DMS + OH rate constant suggests that theSO₂ yield is 50–100%, similar to current estimates for the tropical Pacific.However, the observed amplitude of the DMS diurnal cycle suggests that the oxidation rate is higher than that used by the model, and therefore, that theSO₂ yield is lower in the range of 20–40%.     

Water and sediment outbursts from advanced Franz Josef Glacier,New Zealand

The Franz Josef Glacier, Westland, New Zealand, has a history of catastrophic sediment‐laden outburst ?oods associated with extreme rainfall events when the glacier toe is advanced over its own sediments. Consideration of these events and inspection of recent sediment deposits suggest that there are three distinct modes of outburst. The ?rst is associated with fans fed by over?ow along the glacier margin. As the glacier has advanced across its own fore?eld gravels, it is inferred that the primary drainage conduit has developed a reach of negative slope. In high ?ows massive boulders can block the conduit, trapping lesser clasts. The resulting backup of water causes over?ows through marginal moulins, producing the fan type of deposit. The second type of outburst deposits massive imbricated boulders at a greater or lesser distance from the glacier portal. In this case, pressure buildup drives the blockage out of the portal where the boulders deposit. Smaller materials are generally carried away. The third type consists of very shallow ?ows, and produces massive gravel deposits of uncertain provenance. In this condition, the excess pressure in the conduit results in slight uplift of the glacier and widespread discharge of water and sediment below the glacier snout; gravels and smaller sediments are laid down in a massive deposit across the fore?eld. The massive, boulder‐veneered deposit from the December 1995 outburst is interpreted in the light of the above mechanisms as a hyperconcentrated ?ow deposit from hydraulic jacking, overlain by boulders emplaced by a subsequent conduit outburst. A possible association of outbursts with the present advanced position of the glacier is suggested. Copyright © 2003 John Wiley & Sons, Ltd.     

青海门源地震台爆破干扰的分析与甄别

随着我国经济建设的发展,很多地震台站的观测环境受到各种工程施工的破坏,给测震观测带来干扰。对门源地震台爆破干扰进行了系统分析,确定观测环境的干扰源,并对干扰源的特征做以甄别,研究结果有助于评估门源地震台测震背景干扰的严重程度。     

Hyporheic exchange flow around constructed in‐channel structures and implications for restoration design

In‐channel rock vane structures are widely used in stream restoration as a way to reduce stream channel erosion and create pool or riffle features. When these structures change hydraulic gradients they may affect ecological stream functions, such as hyporheic exchange flow (HEF) patterns. A study of constructed in‐channel structure controls on HEF was conducted in the third‐order Batavia Kill, New York using stream and hyporheic temperature amplitude analysis and computational fluid dynamics (CFD) hydraulic simulations. Temperature monitors were installed in the water column and channel bed at six locations around each of seven in‐channel restoration structures (three cross‐vanes and four J‐hooks) at baseflow in 2007. Elevation surveys of the structures were then used to simulate HEF using CFD. The results indicate a pattern of pronounced upwelling in the run section just below the structure, upwelling transitioning to downwelling within the pool, and pronounced downwelling in the glide out of the pool. This pattern is consistent with natural riffle pool sequences. The direction of HEF inferred from the temperature amplitude analysis agreed with the direction of flow simulated with CFD at 80% of the locations, and the few disagreements were expected due to model limitations. CFD simulation demonstrated that increasing stream flows result in changes in HEF spatial patterns and magnitude at each structure. This work illustrates how CFD simulations can guide design of in‐channel restoration structures for HEF function. Copyright © 2009 John Wiley & Sons, Ltd.     

Understory vascular plant community assembly in relation to time-since-fire and environmental variables in a Chinese boreal forest

Understanding the response of understory vegetation to fire disturbance is vital to biodiversity conservation and management of boreal forests. We surveyed understory vascular plant richness and composition, and measured related environmental variables along a toposequence within three successional stages, initial (3 years post-fire), early (13 years post-fire) and late (>100 years post-fire) successional stages. Using permutation multivariate ANOVA and nonmetric multidimensional scaling, we analyzed how understory species richness and composition change as time-since-fire proceeds, and their correlative relationships with environmental variables. Species richness and composition showed significant differences among the three successional stages. Understory species richness and abundance were significantly associated with time-since-fire, topographic position, elevation and organic layer depth. Among these variables, time-since-fire had the strongest effect and topographic position was the second major factor on affecting understory community assembly. In addition, time-since-fire overwhelmed the effects of soil pH in the initial successional stage and gravimetric soil moisture in early and late successional stages on understory species composition     

High temperature gas–solid reactions in calc–silicate Cu–Au skarn formation; Ertsberg,Papua Province,Indonesia

The 2.7–3 Ma Ertsberg East Skarn System (Indonesia), adjacent to the giant Grasberg Porphyry Copper deposit, is part of the world’s largest system of Cu–Au skarn deposits. Published fluid inclusion and stable isotope data show that it formed through the flux of magma-derived fluid through contact metamorphosed carbonate rock sequences at temperatures well above 600° C and pressures of less than 50 MPa. Under these conditions, the fluid has very low density and the properties of a gas. Combining a range of micro-analytical techniques, high-resolution QEMSCAN mineral mapping and computer-assisted X-ray micro-tomography, an array of coupled gas–solid reactions may be identified that controlled reactive mass transfer through the ~ 1 km³ hydrothermal skarn system. Vacancy-driven mineral chemisorption reactions are identified as a new type of reactive transport process for high-temperature skarn alteration. These gas–solid reactions are maintained by the interaction of unsatisfied bonds on mineral surfaces and dipolar gas-phase reactants such as SO₂ and HCl that are continuously supplied through open fractures and intergranular diffusion. Principal reactions are (a) incongruent dissolution of almandine-grossular to andradite and anorthite (an alteration mineral not previously recognized at Ertsberg), and (b) sulfation of anorthite to anhydrite. These sulfation reactions also generate reduced sulfur with consequent co-deposition of metal sulfides. Diopside undergoes similar reactions with deposition of Fe-enriched pyroxene in crypto-veins and vein selvedges. The loss of calcium from contact metamorphic garnet to form vein anhydrite necessarily results in Fe-enrichment of wallrock, and does not require Fe-addition from a vein fluid as is commonly assumed.