The effect of water table decline on plant biomass and species composition in the Zoige peatland: A four-year in situ field experiment

The Zoige peatland is the largest alpine peatland in the world, and it is suffering the threat of water table decline. Plant productivity and species composition are important to ecosystem carbon sequestration and soil carbon input in peatlands. We examined the responses of plant community composition and biomass accumulation to water table decline to better understanding the responses of this peatland to environmental changes. A four-year in situ field experiment was conducted involving three treatments: deep, shallow, and control water tables, which were achieved by experimental drainage with 50 cm, 20 cm, and 0 cm deep ditches, respectively. Experimental drainage decreased the annual mean height of water table by ca. 12 cm and 15 cm (relative to the control) in the shallow and deep water table treatments, respectively, over the four years. The response of aboveground plant biomass (APB) to water table decline declined in the first year, remained unchanged in the second year and increased during the third and fourth years. However, water table decline had a non-significant effect on belowground plant biomass. This duration-dependent response of APB can be attributed to the changes in community species composition during the study years. Specifically, the negative effect of water table decline in the first year was due to the significant decrease in APB of hygrophytes (sedges and rushes). In the second year, although water table decline significantly increased APB of mesophytes (grasses and forbs), this increase was offset by the decrease in APB of hygrophytes, leading to a neutral effect. In both the third and fourth years, the extent of the increase in APB of mesophytes (typically the forb species Anemone trullifolia var. linearis) was greater than that of the decrease in APB of hygrophytes, leading to a positive effect. Our results indicate that short-term decline of the water table may increase the primary productivity by shifting dominant species of hygrophytes to mesophytes in the Zogie peatland

Evaluation of DBPs formation from SMPs exposed to chlorine, chloramine and ozone

Soluble microbial products (SMPs) are an important group of components in wastewater effluents. In this study, the formation of disinfection by-products (DBPs), including trihalomethanes (THMs), haloacetic acids (HAAs), chlorinated solvents (CSs), haloketones (HKs), haloacetonitriles (HANs) and trichloronitromethane (TCNM) (chloropicrin), from SMPs during chlorination, chloramination and ozonation was investigated. More carbonaceous DBPs (C-DBPs: THMs, HAAs, CSs and HKs) and nitrogenous DBPs (N-DBPs: HANs and TCNM) were formed in chlorination than chloramination. More dichloroacetic and N-DBPs, and higher DBP formation potential were generated by SMPs than by natural organic matter. The results also show that disinfection factors, including temperature, pH, disinfectant dose, reaction time and bromide level significantly affected the formation of DBPs from SMPs. Additionally, the bromine incorporation factor indicates that chloramination may be a good alternative to chlorination in reducing the formation of Br-DBPs from SMPs. Bromide level and pH were the key factors affecting the formation of DBPs in both chlorination and chloramination

Long-term Pleistocene aridification and possible linkage to high-latitude forcing: New evidence from grain size and magnetic susceptibility proxies from loess-paleosol record in northeastern China

Loess deposits are regarded as good indicators of the inception and development of arid and semi-arid climate in central Asia and northern China during the late Cenozoic. In northeastern China extensive loess deposits are found surrounding the Horqin and Otindag sand fields, and they have great potential for reconstructing the long-term aridification history of the region. However, these loess deposits are currently poorly understood. Here, we present a high-resolution magnetic susceptibility (MS) and grain-size record spanning the last 1.0 Ma from a 36.6-m-thick loess-paleosol sequence at Niuyangzigou site (NYZG) in NE China. The grain-size record reveals a long-term drying trend in NE China since ca. 1.0 Ma, punctuated by two significant abrupt drying events at similar to 0.65 Ma and similar to 0.3 Ma. These results demonstrate a process of stepwise intensification of drying in NE China over the past 1 Ma, and lend support to the hypothesis that global ice volume/temperature changes were the major driver of the long-term aridification of Asian dust source areas. However, unlike the widely studied loess deposits on the central Chinese Loess Plateau (CLP), the MS record in paleosol units Sl, S2 and S4 from the NYZG site do not show evidence of enhanced monsoon precipitation resulting from decreased global ice volume and the prolonged episodes of interglaciation after the Mid-Pleistocene Transition evident in the ice volume record. We hypothesize that this may be due to differences in the climatic sensitivity of the MS of Chinese loess deposits on a regional scale, rather than to in regional differences in monsoon intensity. (C) 2017 Elsevier B.V. All rights reserved

Effects of Cu2+ and humic acids on degradation and fate of TBBPA in pure culture of Pseudomonas sp strain CDT

Soil contamination with tetrabromobisphenol A (TBBPA) has caused great concerns; however, the presence of heavy metals and soil organic matter on the biodegradation of TBBPA is still unclear. We isolated Pseudomonas sp. strain CDT, a TBBPA-degrading bacterium, from activated sludge and incubated it with C-14-labeled TBBPA for 87 days in the absence and presence of Cu2+ and humic acids (HA). TBBPA was degraded to organic-solvent extractable (59.4% +/- 2.2%) and non-extractable (25.1% +/- 1.3%) metabolites, mineralized to CO2 (4.8% +/- 0.8%), and assimilated into cells (10.6% +/- 0.9%) at the end of incubation. When Cu2+ was present, the transformation of extractable metabolites into non-extractable metabolites and mineralization were inhibited, possibly due to the toxicity of Cu2+ to cells. HA significantly inhibited both dissipation and mineralization of TBBPA and altered the fate of TBBPA in the culture by formation of HA-bound residues that amounted to 22.1% +/- 3.7% of the transformed TBBPA. The inhibition from HA was attributed to adsorption of TBBPA and formation of bound residues with HA via reaction of reactive metabolites with HA molecules, which decreased bioavailability of TBBPA and metabolites in the culture. When Cu2+ and HA were both present, Cu2+ significantly promoted the HA inhibition on TBBPA dissipation but not on metabolite degradation. The results provide insights into individual and interactive effects of Cu2+ and soil organic matter on the biotransformation of TBBPA and indicate that soil organic matter plays an essential role in determining the fate of organic pollutants in soil and mitigating heavy metal toxicity. (C) 2017 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V