CHEMICAL WEATHERING PROCESSES AND ATMOSPHERIC CO_2 CONSUMPTION OF HUANGHE RIVER AND CHANGJIANG RIVER BASINS

Rock weathering plays an important role in studying the long-term carbon cycles and global climatic change. According to the statistics analysis, the Huanghe (Yellow) River water chemistry was mainly controlled by evaporite and carbonate weathering, which were responsible for over 90% of total dissolved ions. As compared with the Huanghe River basin, dissolved load of the Changjiang (Yangtze) River was mainly originated from the carbonate dissolution. The chemical weathering rates were estimated to be 39.29t/(km2·a) and 61.58t/(km2·a) by deducting the HCO3- derived from atmosphere in the Huanghe River and Changjiang River watersheds, respectively. The CO2 consumption rates by rock weathering were calculated to be 120.84×103mol/km2 and 452.46×103mol/km2 annually in the two basins, respectively. The total CO2 consumption of the two basins amounted to 918.51×109mol/a, accounting for 3.83% of the world gross. In contrast to other world watersheds, the stronger evaporite reaction and infirm silicate weathering can explain such feature that CO2 consumption rates were lower than a global average, suggesting that the sequential weathering may be go on in the two Chinese drainage basins.

Effect of atmospheric precipitation on the dissolved loads of the Dongjiang River,China

The atmospheric precipitation plays an important role in influencing the river chemistry of the Dongjiang River. The atmospheric contribution to river water is estimated by reference to Cl concentration called Cl ref . The Cl ref of 41 97 μmol/L represents the highest chloride concentration of the rainwater inputs to river water, thus sea salts are responsible for total Cl concentration of the Dongjiang River. According to the principal compositions of precipitation and river water, two approaches sea salt correction and precipitation correction were proposed in order to correct the contribution proportions of atmospheric precipitation on the solutes and to calculate chemical weathering rate. The results reflected that the atmospheric contribution ratios fluctuate from ～5% to ～20% of TDS(total dissolved solids) in the Dongjiang River. As compared with the other world watersheds, the lower dissolved ion contents and high runoff may result in the obvious influence of precipitation on river chemistry in the Dongjiang basin. The major elemental chemistry is mainly controlled by silicate weathering, with the anion HCO - 3 and cation Ca 2+ and Na\++ dominating the major compositions in this basin. The estimated chemical weathering rate of 15 78—23 48 t/(km 2·a) is only 40%—60% of a global average in the Dongjiang basin. Certainly, the estimated results are still under correction gradually because the effect of human activities on the precipitation chemistry has never been quantified in detail.

Adsorption of zinc on manganite(γ-MnOOH): particle concentration effect and adsorption reversibility

The adsorption and desorption processes of Zn(Ⅱ) on γ-MnOOH as a function of particle concentrations(C p) were studied. An obvious C p effect was observed in this adsorption system. The degree of adsorption hysteresis increased greatly with the increasing of C p, indicating that the extent of the real metastable-equilibrium states deviating from the ideal equilibrium state was enhanced with the increasing of C p. The C p-reversibility relationship confirmed the metastable-equilibrium adsorption(MEA) inequality(Pan, 1998a), which was the core formulation of the MEA theory. Because the MEA inequality was based on the basic hypothesis of MEA theory that adsorption density Γ is not a state variable, the C p-reversibility relationship gave indirect evidence to the basic hypothesis of MEA theory.

A method to extract algae toxin of microcystin-LR

A simple and low-cost method to obtain cyanobacterial toxin microcystin-LR(MC-LR) was developed. A new strain of Microcystis aeruginosa, named DC-1, producing microcystin-LR but not microcystin-RR, was separated from the field blooming algae samples of Dianchi Lake, in southwest of China. Following three times' freeze and thaw treatment, the cultivated DC-1 cells were extracted with 40% methanol in water. The extract was centrifuged and the supernatant applied to a Hydrophilic-Lipophilic Balance(HLB) SPE cartridge. Eluted impurities with a certain gradient from 30% to 50% methanol in water, MC-LR was finally eluted from the HLB cartridge with 60% methanol in water, and samples containing 3.85% to 14.8% of MC-LR were obtained. These MC-LR samples may be used in adsorption and biodegradation experiments instead of using expensive standard reagents.