19 research outputs found
Geochemical and physical sources of radon variation in a subterranean estuary — implications for groundwater radon activities in submarine groundwater discharge studies
Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Marine Chemistry 110 (2008): 120-127, doi:10.1016/j.marchem.2008.02.011.Submarine groundwater discharge (SGD), in form of springs and diffuse seepage,
has long been recognized as a source of chemical constituents to the coastal ocean.
Because groundwater is two to four orders of magnitude richer in radon than surface
water, it has been used as both a qualitative and a quantitative tracer of groundwater
discharge. Besides this large activity gradient, the other perceived advantage of radon
stems from its classification as noble gas; that is, its chemical behavior is expected not to
be influenced by salinity, redox, and diagenetic conditions present in aquatic
environments.
During our three-year monthly sampling of the subterranean estuary (STE) in
Waquoit Bay, MA, we found highly variable radon activities (50-1600 dpm L-1) across
the fresh-saline interface of the aquifer. We monitored pore water chemistry and radon
activity at 8 fixed depths spanning from 2 to 5.6 m across the STE, and found seasonal
fluctuations in activity at depths where elevated radon was observed. We postulate that
most of pore water 222Rn is produced from particle-surface bound 226Ra, and that the
accumulation of this radium is likely regulated by the presence of manganese
(hydr)oxides. Layers of manganese (hydr)oxides form at the salinity transition zone
(STZ), where water with high salinity, high manganese, and low redox potential mixes
with fresh water. Responding to the seasonality of aquifer recharge, the location of the
STZ and the layers with radium enriched manganese (hydr)oxide follows the seasonal
land- or bay-ward movement of the freshwater lens. This results in seasonal changes in
the depth where elevated radon activities are observed.
The conclusion of our study is that the freshwater part of the STE has a radon
signature that is completely different from the STZ or recirculated sea water. Therefore,
the radon activity in SGD will depend on the ratio of fresh and recirculated seawater in
the discharging groundwater.This work is a
result of research sponsored by NSF (OCE- 0425061 to M.A.C.) and the WHOI
Postdoctoral Scholar program (to H.D.)
Mapping the planet’s critical natural assets
Sustaining the organisms, ecosystems and processes that underpin human wellbeing is necessary to achieve sustainable development. Here we define critical natural assets as the natural and semi-natural ecosystems that provide 90% of the total current magnitude of 14 types of nature’s contributions to people (NCP), and we map the global locations of these critical natural assets at 2 km resolution. Critical natural assets for maintaining local-scale NCP (12 of the 14 NCP) account for 30% of total global land area and 24% of national territorial waters, while 44% of land area is required to also maintain two global-scale NCP (carbon storage and moisture recycling). These areas overlap substantially with cultural diversity (areas containing 96% of global languages) and biodiversity (covering area requirements for 73% of birds and 66% of mammals). At least 87% of the world’s population live in the areas benefitting from critical natural assets for local-scale NCP, while only 16% live on the lands containing these assets. Many of the NCP mapped here are left out of international agreements focused on conserving species or mitigating climate change, yet this analysis shows that explicitly prioritizing critical natural assets and the NCP they provide could simultaneously advance development, climate and conservation goals.We thank all the participants of two working groups hosted by Conservation International and the Natural Capital Project for their insights and intellectual contributions. For further advice or assistance, we thank A. Adams, K. Brandon, K. Brauman, A. Cramer, G. Daily, J. Fisher, R. Gould, L. Mandle, J. Montgomery, A. Rodewald, D. Rossiter, E. Selig, A. Vogl and T. M. Wright. The two working groups that provided the foundation for this analysis were funded by support from the Marcus and Marianne Wallenberg Foundation to the Natural Capital Project (R.C.-K. and R.P.S.) and the Betty and Gordon Moore to Conservation International (R.A.N. and P.M.C.)
Markets and jungles
Economic institutions determine prospects for growth and development. This paper examines necessary conditions for an economy to support institutions that implement markets. Agents differ in land holdings, skill, and power. A competitive market assigns land to the skilled, not necessarily to the powerful. Therefore a market allocation needs to be robust to coalitional expropriation. In a dynamic setting, market payoffs may induce sufficient inequality in next period’s endowments for markets to alternate with expropriation in a limit cycle, decreasing efficiency and amplifying macroeconomic fluctuations. Long run stability of markets is favored by higher social mobility, more initial equality, and less mismatch between skill and land
PrhA controls a novel regulatory pathway required for the specific induction of Ralstonia solanacearum hrp genes in the presence of plant cells
Microbe-aliphatic hydrocarbon interactions in soil: implications for biodegradation and bioremediation.
Aliphatic hydrocarbons make up a substantial portion of organic contamination in the terrestrial environment. However, most studies have focussed on the fate and behaviour of aromatic contaminants in soil. Despite structural differences between aromatic and aliphatic hydrocarbons, both classes of contaminants are subject to physicochemical processes, which can affect the degree of loss, sequestration and interaction with soil microflora. Given the nature of hydrocarbon contamination of soils and the importance of bioremediation strategies, understanding the fate and behaviour of aliphatic hydrocarbons is imperative, particularly microbe-contaminant interactions. Biodegradation by microbes is the key removal process of hydrocarbons in soils, which is controlled by hydrocarbon physicochemistry, environmental conditions, bioavailability and the presence of catabolically active microbes. Therefore, the aims of this review are (i) to consider the physicochemical properties of aliphatic hydrocarbons and highlight mechanisms controlling their fate and behaviour in soil; (ii) to discuss the bioavailability and bioaccessibility of aliphatic hydrocarbons in soil, with particular attention being paid to biodegradation, and (iii) to briefly consider bioremediation techniques that may be applied to remove aliphatic hydrocarbons from soil