Aixin Hou

The 2007 water crisis in Wuxi, China: analysis of the origin.

An odorous tap water crisis that affected two million residents for several days occurred in Wuxi, China in the summer of 2007. Volatile sulfide chemicals including methyl thiols, dimethyl sulfide, dimethyl disulfide, and dimethyl trisulfide were the dominant odorous contaminants in Lake Taihu and in tap water during the crisis. These contaminants originated from the decomposition of a massive cyanobacterial bloom that was triggered by illegal industrial discharges and inadequately regulated domestic pollution. A specific emergency drinking water treatment process was quickly developed using a combination of potassium permanganate oxidation and powdered activated carbon adsorption. The emergency treatment process removed the odor from the tap water and solved the crisis successfully in several days. This experience underscores the suggestion that a combination of stresses associated with eutrophication and industrial and domestic wastewater discharges can push an aquatic system to the tipping point with consequences far more severe than would occur if the system were subjected to each stress separately.

Emergency Drinking Water Treatment during Source Water Pollution Accidents in China: Origin Analysis, Framework and Technologies

China has suffered frequent source water contamination accidents in the past decade, which has resulted in severe consequences to the water supply of millions of residents. The origins of typical cases of contamination are discussed in this paper as well as the emergency response to these accidents. In general, excessive pursuit of rapid industrialization and the unreasonable location of factories are responsible for the increasing frequency of accidental pollution events. Moreover, insufficient attention to environmental protection and rudimentary emergency response capability has exacerbated the consequences of such accidents. These environmental accidents triggered or accelerated the promulgation of stricter environmental protection policy and the shift from economic development mode to a more sustainable direction, which should be regarded as the turning point of environmental protection in China. To guarantee water security, China is trying to establish a rapid and effective emergency response framework, build up the capability of early accident detection, and develop efficient technologies to remove contaminants from water.

Impacts of Hurricanes Katrina and Rita on the microbial landscape of the New Orleans area

Floodwaters in New Orleans from Hurricanes Katrina and Rita were observed to contain high levels of fecal indicator bacteria and microbial pathogens, generating concern about long-term impacts of these floodwaters on the sediment and water quality of the New Orleans area and Lake Pontchartrain. We show here that fecal indicator microbe concentrations in offshore waters from Lake Pontchartrain returned to prehurricane concentrations within 2 months of the flooding induced by these hurricanes. Vibrio and Legionella species within the lake were more abundant in samples collected shortly after the floodwaters had receded compared with samples taken within the subsequent 3 months; no evidence of a long-term hurricane-induced algal bloom was observed. Giardia and Cryptosporidium were detected in canal waters. Elevated levels of fecal indicator bacteria observed in sediment could not be solely attributed to impacts from floodwaters, as both flooded and nonflooded areas exhibited elevated levels of fecal indicator bacteria. Evidence from measurements of Bifidobacterium and bacterial diversity analysis suggest that the fecal indicator bacteria observed in the sediment were from human fecal sources. Epidemiologic studies are highly recommended to evaluate the human health effects of the sediments deposited by the floodwaters.

Nitrous oxide emissions from terrestrial ecosystems in China

Abstract N2O emissions from agricultural, forest and grassland ecosystems in China were in situ measured by closed chamber method, and estimation of total annual N2O emissions from these ecosystems and a technique mitigating N2O emission from agricultural soil were reported. The results showed: (1) the annual emissions of N2O from rice, maize, soybean and wheat field, temperate forest and temperate grassland in China were 1.08–2.99, 0.47–4.51, 1.98, 1.02–2.93, 0.28–1.28 and 0.27–0.61 kg N 2 O – N ha −1 , respectively. The total annual N2O emissions from agricultural, forest and temperate grassland ecosystems in China were estimated as 152.49, 94.10 and 112.13 Gg N, respectively. Industrially co-crystallized ammonium bicarbonate (AB) with dicyandiamide, substituting for ammonium bicarbonate in China, decreased N2O emission significantly from a meadow brown soil in laboratory (80.2% at soil moisture 12% and 40.0% at soil moisture 22%, respectively) and upland field condition (74.0%).

Nitrous oxide and nitric oxide fluxes from an upland field in Japan : Effect of urea type, placement, and crop residues

Fertilizer type and application mode may influence nitrous oxide(N2O) and nitric oxide (NO) emissions as well as crop yield. Using astatic chamber method, fluxes of both gases from a Chinese cabbage field inJapan were measured in situ following the application of easily decomposableurea by broadcasting (U-BC) and banding (U-B) and coated urea by banding(CU-B),respectively, at an application rate of 250 kg Nha−1. The measurements were made throughout the growingseason and continued 3 more months after harvest to determine the effect ofcropresidues on the emissions. Large N2O fluxes from U-BC occurredwithinabout 2 weeks after the application of the N fertilizer, while that from bothU-B and CU-B was prolonged by about 2 weeks, and significant emissions lasted alonger time but with a smaller emission size. Substantial N2O fluxesderived from crop residues were observed in the late growing season (especiallyfollowing rainfall) as well as after harvest, at all treatments including thecontrol plots (CK). Large NO fluxes occurred only at U-BC within the first 2weeks through the measurements. Total emissions were estimated to be 38.1,78.3,77.8, and 100.4 mg N2O-N m−2 and 0.7,194.9, 8.5, and 11.4 mg NO-N m−2 at CK, U-BC,U-B,and CU-B, respectively. Statistical analyses indicate that neither the bandmodenor the coated urea was able to significantly reduce the total N2Oemission through the season, but the band mode substantially reduced the NOemission. However, the application of urea by the band mode presented a 22.8%increase in crop yield as compared with urea applied by broadcasting.Therefore,by improving fertilizer use efficiency to decrease the amount of N needed tobetter meet the crop growing demand, the band mode may be a good agriculturalpractice to also reduce N2O emission. In addition, the experimentdemonstrated that crop residue is a large source of N2O emission.

Effects of urea form and soil moisture on N2O and NO emissions from Japanese Andosols

Abstract Nitrous oxide (N 2 O) and nitric oxide (NO) emissions from soil are affected by many factors. Soil nitrogen source, especially N fertilizer input, and soil moisture might be the most important factors to control these two gases emission rate. In this study, laboratory incubation experiments were conducted to determine the effect of the urea form and the soil moisture on N 2 O and NO emissions in Japanese Andosols. Results showed that there were no significant differences in the total amount of N 2 O and NO emissions over 77 d between non-coated and coated urea (CU) treatments, except for NO emission at 40% wfps (water filled pore space) where it was reduced by 23% when CU was applied. As compared to easily decomposable urea (U), however, CU did reduce N 2 O and NO emissions in the earlier period shortly after fertilization. The results also indicated that soil moisture had a much more significant effect on N 2 O and NO emissions than the form of urea. From 40% to 100% wfps, there was a positive relationship between N 2 O emission and soil water content and a negative relationship for NO. The flux ratio of NO/N 2 O was governed by soil moisture with a greatest value at the lowest wfps treatments for each fertilizer treatment. Soil moisture could be the most important factor controlling N 2 O and NO emissions when a rich N supply exist in soil.

Response of salt marshes to oiling from the Deepwater Horizon spill: Implications for plant growth, soil surface-erosion, and shoreline stability

We investigated the initial impacts and post spill recovery of salt marshes over a 3.5-year period along northern Barataria Bay, LA, USA exposed to varying degrees of Deepwater Horizon oiling to determine the effects on shoreline-stabilizing vegetation and soil processes. In moderately oiled marshes, surface soil total petroleum hydrocarbon concentrations were ~70mgg(-1) nine months after the spill. Though initial impacts of moderate oiling were evident, Spartina alterniflora and Juncus roemerianus aboveground biomass and total live belowground biomass were equivalent to reference marshes within 24-30months post spill. In contrast, heavily oiled marsh plants did not fully recover from oiling with surface soil total petroleum hydrocarbon concentrations that exceeded 500mgg(-1) nine months after oiling. Initially, heavy oiling resulted in near complete plant mortality, and subsequent recovery of live aboveground biomass was only 50% of reference marshes 42months after the spill. Heavy oiling also changed the vegetation structure of shoreline marshes from a mixed Spartina-Juncus community to predominantly Spartina; live Spartina aboveground biomass recovered within 2-3years, however, Juncus showed no recovery. In addition, live belowground biomass (0-12cm) in heavily oiled marshes was reduced by 76% three and a half years after the spill. Detrimental effects of heavy oiling on marsh plants also corresponded with significantly lower soil shear strength, lower sedimentation rates, and higher vertical soil-surface erosion rates, thus potentially affecting shoreline salt marsh stability.

Effects of organic and N fertilizers on methane production potential in a Chinese rice soil and its microbiological aspect.

An incubation experiment to determine the effects of organic and chemical N fertilizers on methane (CH4) production potential in a Chinese flooded rice soil was conducted. Organic matter, added as rice straw and organic manure, increased CH4 production rate significantly. Chemical N fertilizers such as ammonium bicarbonate (AB), modified ammonium bicarbonate (MAB), and urea (U) did not show a clear effect when they were applied with rice straw. Field results may be very different because of the involvement of rice plants. Organic manure showed different promoting effects on CH4 production rate. Pig manure stimulated the production rate most, followed by chicken and cattle manure. This difference in organic manure was not related to either total C added to the system or to C/N. The study on bacteria groups related to CH4 production indicated that the different effects of organic matter may be closely related to content of easily decomposable organic matter. A significant linear relationship between CH4 production and the logarithm of the number of zymogenic bacteria was found with an r value of 0.96. This finding suggests that the number of zymogenic bacteria may be used as an index to predict CH4 production potential in flooded rice fields and other wetlands.

Characterization of clinical and environmental types of Vibrio vulnificus isolates from Louisiana oysters.

Vibrio vulnificus, a naturally occurring estuarine bacterium frequently transmitted to humans via raw oysters, is a leading cause of seafood-related deaths in the United States. Although unique virulence markers have not been identified to date, multiple biomarkers have been used previously to associate strains with clinical or environmental types of V. vulnificus. In this study, we evaluated the usefulness of these biomarkers in characterizing 349 V. vulnificus oyster isolates by the presence/absence of a viuB-associated fragment and genotypes of three biomarkers: the virulence-correlated gene (vcg), 16S rRNA, and the capsular polysaccharide (CPS) operon. Genotyping data indicated that environmental-type V. vulnificus strains accounted for the majority of oyster isolates, and the percentages ranged from 51.6% for 16S rRNA (type A) to 72.5% for CPS (allele 2 or none). There was also a small percentage (8%) of V. vulnificus isolates possessing both environmental (type A) and clinical (type B) genotypes of 16S rRNA. Additionally, the presence of the viuB fragment (41%) was significantly associated with clinical genotypes of V. vulnificus (p < 0.0001). An interesting seasonal pattern was observed, with clinical-type V. vulnificus isolates more frequently associated with warmer months. In conclusion, the majority of V. vulnificus isolates present in Louisiana raw oysters were of environmental type. There existed a seasonal variation in the V. vulnificus genotypes identified, which may help guide future control measures to focus more specifically on seasons that tend to accumulate more clinical-type V. vulnificus. The study also highlighted the need to identify unique virulence markers in this organism, which could facilitate future screening of virulent V. vulnificus strains from oysters.

4 Years after the Deepwater Horizon Spill: Molecular Transformation of Macondo Well Oil in Louisiana Salt Marsh Sediments Revealed by FT-ICR Mass Spectrometry

Gulf of Mexico saltmarsh sediments were heavily impacted by Macondo well oil (MWO) released from the 2010 Deepwater Horizon (DWH) oil spill. Detailed molecular-level characterization of sediment extracts collected over 48 months post-spill highlights the chemical complexity of highly polar, oxygen-containing compounds that remain environmentally persistent. Electrospray ionization (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), combined with chromatographic prefractionation, correlates bulk chemical properties to elemental compositions of oil-transformation products as a function of time. Carboxylic acid incorporation into parent MWO hydrocarbons detected in sediment extracts (corrected for mass loss relative to C30 hopane) proceeds with an increase of ∼3-fold in O2 species after 9 months to a maximum of a ∼5.5-fold increase after 36 months, compared to the parent MWO. More importantly, higher-order oxygenated compounds (O4-O6) not detected in the parent MWO increase in relative abundance with time as lower-order oxygenated species are transformed into highly polar, oxygen-containing compounds (Ox, where x > 3). Here, we present the first molecular-level characterization of temporal compositional changes that occur in Deepwater Horizon derived oil contamination deposited in a saltmarsh ecosystem from 9 to 48 months post-spill and identify highly oxidized Macondo well oil compounds that are not detectable by routine gas-chromatography-based techniques.