Effect of a polybrominated diphenyl ether congener (BDE-47) on growth and antioxidative enzymes of two mangrove plant species, Kandelia obovata and Avicennia marina, in South China

The effects of BDE-47 on the growth and antioxidative responses of the seedlings of Kandelia obovata (Ko) and Avicennia marina (Am) were compared in an 8-week hydroponic culture spiked with different levels of BDE-47, 0.1, 1, 5 and 10 mg l⁻¹. The two highest BDE-47 levels significantly suppressed the growth and increased the activities of three antioxidative enzymes, superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), of Ko in week 1. However, SOD and POD activities at high levels of BDE-47 became lower than the control in week 8. On the contrary, growth of Am was not affected at all contamination levels, and the activities of three enzymes were enhanced by BDE-47 in weeks 1 and 4, but such stimulatory effect became insignificant in week 8. Avicennia was more tolerant to BDE-47 toxicity than Kandelia, as its antioxidative enzymes could better counter-balance the oxidative stress caused by BDE-47.     

Studies on Quantity and Intensity of Potassium in Some Taiwan Farmland Soils

Potassium (K) is one of the major nutritions for plants. The evaluation of K quantity and intensity relationships (K Q/I curve) in different farmland soils is important for the appropriate application of K fertilizer. With this information the pollution of K fertilizer in the environment can be prevented. Potassium ions in solution and in exchange complex are available to plants. However, the K availability is affected by the antagonism of Ca and Mg ions. The K quantity–intensity relationships (K Q/I curve) has been suggested to describe the K availability in soil, taking into account the competition between K ions and Ca and Mg ions for exchange sites on the soil exchange complex. In this experiment, we studied the Q/I plot of the soils and found that the parameters can be used to evaluate the supply state of K. The results show that the K Q/I relationships of the five soils differed as the Ca concentration of the initial solution is varied. This phenomenon reflected different degrees of exchange of K by Ca on the exchangeable sites of the clay minerals. The intensity of the potassium supply of Nieuniaokang and Erling soils possessed higher AR⁰ values, indicating that exchangeable K in these soils are primarily on the plannar surface of the clay particles; while those of the Liuying, Shanghua, and Taikang series are primarily on the crystal edge surfaces and are less available to the plant. The K supply intensity of Chiangjung soil is lower when the Ca concentration is low, but it increased when the Ca concentration is high, and the K supply intensity of Pinchen soil is the opposite. The K supply intensity of Nieuniaokang soil is high, but its potential buffering capacity (PBC) is low. Therefore, it is suggested that the K application should be split into small doses to maintain a high K supply intensity. The K supply intensity of Liuying soil is low, but its PBC is large, so it is expected that a large amount of K fertilizers would be needed to increase the K supply intensity to a more available level. The supply intensity and the buffering capacity of the Chiangjung and Pinchen soils are low, and the K management in these soils will be more difficult.     

Effect of human‐controlled hydrological regime on the source,transport, and flux of particulate organic carbon from the lower Huanghe (Yellow River)

Evaluating the role of fluvial transfer of terrestrial organic carbon (OC) and subsequent burial in the global carbon cycle requires the sources and fluxes of fluvial OC to be assessed, which remains poorly constrained in the Huanghe (Yellow River). Here, we report the elemental, stable isotopic, and radiocarbon activity of particulate organic carbon (POC) sampled at the outlet of Huanghe in 2012–2013. We show that the Huanghe riverine POC can be explained by binary mixing of fossil (POC_fossil) and non‐fossil (POC_non‐fossil) components, the former may reach ~40% of the total POC. The Huanghe POC_non‐fossil is mostly sourced from C3 plants, with a mean residence time of c. 2200 years. The current human‐controlled hydrological regime strongly influenced the POC sources, transport modes, and fluxes. In 2012–2013, the Huanghe delivered 0.73 Tg (1 Tg = 10¹² g) of POC to the sea, and about 28% of the annual POC flux occurred within a short human induced flood event. Globally, the Huanghe should be one of the largest rivers in the transfer and re‐burial of fossil OC. However, the fate of Huanghe fossil OC is still unconstrained and needs to be further investigated. Copyright © 2015 John Wiley & Sons, Ltd.     

Effects of urbanization and stormwater control measures on streamflows in the vicinity of Clarksburg,Maryland, USA

Understanding the efficacy of revised watershed management methods is important to mitigating the impacts of urbanization on streamflow. We evaluated the influence of land use change, primarily as urbanization, and stormwater control measures on the relationship between precipitation and stream discharge over an 8‐year period for five catchments near Clarksburg, Montgomery County, Maryland, USA. A unit‐hydrograph model based on a temporal transfer function was employed to account for and standardize temporal variation in rainfall pattern, and properly apportion rainfall to streamflow at different time lags. From these lagged relationships, we quantified a correction to the precipitation time series to achieve a hydrograph that showed good agreement between precipitation and discharge records. Positive corrections appeared to include precipitation events that were of limited areal extent and therefore not captured by our rain gages. Negative corrections were analysed for potential causal relationships. We used mixed‐model statistical techniques to isolate different sources of variance as drivers that mediate the rainfall–runoff dynamic before and after management. Seasonal periodicity mediated rainfall–runoff relationships, and land uses (i.e. agriculture, natural lands, wetlands and stormwater control measures) were statistically significant predictors of precipitation apportionment to stream discharge. Our approach is one way to evaluate actual effectiveness of management efforts in the face of complicating circumstances and could be paired with cost data to understand economic efficiency or life cycle aspects of watershed management. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.