Shilu Wang

The spatial distribution and emission of nitrous oxide (N2O) in a large eutrophic lake in eastern China: anthropogenic effects.

The emission of N(2)O from China is globally significant, but relatively few direct observations have been made in many of the fresh water environments most likely to be important sites of N(2)O production. In this paper, N(2)O saturations were examined in the ecologically heterogeneous, eutrophied, Lake Taihu, as well as in surrounding rivers in eastern China. The emissions of N(2)O were estimated and compared with those from other landscapes within the Lake Taihu drainage basin. We found that anthropogenically-enhanced inorganic N inputs act as a limited primary control on the spatial distribution of N(2)O saturations in heavily eutrophied parts of the lake only and that overall, lake N(2)O production and emission are not raised as significantly as expected due to high N inputs. In comparison, the heavily eutrophied river network is an important fraction of the local N(2)O budget, and when considered together with emissions of N(2)O from the lake, constitute a major (10-50% depending on season) fraction of total N(2)O emissions from the Lake Taihu drainage basin.

Analyses of 210Pb concentrations in surface air and in rain water at the central Guizhou, China

Samples of surface air and rain water were collected at the Mt. Guanfeng site located at Guiyang, China. The monthly mean 210Pb concentrations in surface air exhibited a U-pattern with high values appearing in winter and low values in summer and early autumn. The annual mean of 210Pb concentrations in surface air was estimated to be 2.7 ± 0.6 mBq m-3, which was at least four times higher than the annual mean reported from a large number of monitoring stations located throughout the world. The amounts of enriched Uranium in soil at the region could significantly contribute a great deal of release of 222Rn that decay to 210Pb which gets attached to the atmospheric aerosols. The site was under the influence of a monsoon climate. The distribution of monthly mean of 210Pb concentrations in surface air correlates well with the reciprocal of monthly average of observed air temperature and rainfall. The partition coefficients of 210Pb between rain water-surface air in the winter and spring were larger than those in the summer and autumn. The type and duration of rain depending on season played key roles for the changes of partition coefficients, although the rain amount is important.

Atmospheric pollutants transport tracks revealed from 131I, 137Cs, and 134Cs leaked from Fukushima accident and 7Be and 210Pb observed at Guiyang of China

A massive earthquake measuring 9.0 on the Richter scale that occurred on March 11, 2011, on Honshu Island, Japan, caused radioactivity leakage from the Fukushima Nuclear Power Plant, which led to the leakage of artificial nuclides (131I, 137Cs, and 134Cs) and their global transportation by atmospheric circulation. This paper reports a systematic comparative observation on radioactive concentrations of natural nuclides (7Be and 210Pb) and artificial nuclides (131I, 137Cs, and 134Cs) at the surface level, measured in weekly continuous aerosol sampling at Mount Guanfeng, Guiyang, China, from March 17, 2011 to April 28, 2011. During this period, the variations in the nuclide concentrations associated with their transport paths were analyzed with 315 hour back-trajectories of air mass initialized 500 m above the surface level at Guiyang. The results show that the pollutants of nuclear leakage from the Fukushima accident were transported to the Guiyang region of China via two significant pathways. In the first pathway the first wave of nuclear pollutants were transported from west to east in air masses at higher altitudes via global atmospheric circulation. The nuclear pollutants encircled the Earth almost once and after about 10 days to two weeks, between March 24 and March 31, 2011, intruded Guiyang from the northwestern region of China. In the second pathway, the nuclear pollutants from the Fukushima region arrived at Guiyang between April 7 and April 14, 2011, via air masses at lower altitudes that moved southwards because of the squeezing of the northeast Asian weather system and then by the influence, in succession, of the northeastern and southeastern air currents in the low-latitude region. The first transport pathway for atmospheric pollutants is on a global scale and based on air masses at higher altitudes, and the second transport pathway is on an eastern Asia regional scale and based on the air masses at lower altitude.

Importance of Considered Organic Versus Inorganic Source of Carbon to Lakes for Calculating Net Effect on Landscape C Budgets

Lakes and reservoirs transform, emit, and bury carbon that is exported from land and are thus significant components of terrestrial carbon budgets. Their significance is often assessed by integrating these water bodies into terrestrial primary production. However, the transfer of inorganic carbon (IC) is likely a sticking point for these integrations because IC is not part of net ecosystem production. Here we integrated carbon evasion and organic carbon (OC) burial in a lake in the context of inorganic and OC cycling in a karst catchment from a system perspective. The lake emitted carbon dioxide (CO2) and buried OC at rates of 1.0 +/- 0.2 and 0.9 +/- 0.2 g Cm-2 a(-1), respectively, approximately equaling 13% and 11% of catchment net ecosystem production, respectively. These proportions represent significant influences on terrestrial carbon budgets, given an organic origin. However, catchment carbon export is dominated by IC that is derived from carbonates dissolved by soil CO2. Lake CO2 evasion accounts for less than 0.1% of soil CO2 efflux, suggesting little potential in significantly altering terrestrial carbon budgets. This comparison indicates the significance of aquatic CO2 evasion, requiring an adjustment of terrestrial carbon budgets to recognize their dependence on carbon origins. The significance may be overstated if inorganic origin is ignored. Our study suggests that a careful reassessment of the significance of CO2 evasion and OC burial in freshwater ecosystems to local and global carbon budgets, with full consideration of their sources, is necessary and pressing.

Impoundment-induced nitrogen–phosphorus imbalance in cascade reservoirs alleviated by input of anthropogenic nutrients

ABSTRACT The ratio of nitrogen to phosphorus (N:P) is an important variable that has a close relationship with the ecological problems of nuisance algal blooms and eutrophication in aquatic environments in terms of nutrient limitation. Reservoirs generally have much higher retention efficiency for P than for N. This inherent dissimilarity in the N and P biogeochemical cycles likely results in N–P stoichiometric imbalance in downstream rivers and reservoirs, consequently causing an increase in the N:P ratio and aggravating P limitation. Here we determined the total N (TN) and total P (TP) concentrations in the cascade reservoirs of the Wujiang River and Lancangjiang River basins. The results show that TN:TP ratios in these 2 basins exhibited a common inverted V-shaped (∧) pattern downstream. We found that P is not only retained by reservoirs more efficiently than N but is also replenished at faster rates than N given anthropogenic impacts; consequently, the N–P imbalance caused by these impoundments is alleviated within a short distance downstream because of inputs of anthropogenic nutrients. Our research suggests that construction of cascade reservoirs does not necessarily lead to strict P deficiency and anomalously high N:P ratios downstream.