[Chemical depletion of cumulative phosphorus in soils].

Cumulative phosphorus was defined as the phosphorus which was unavailable for plants and accumulated in soils fertilizer application. In this paper, chemical depletion of cumulative phosphorus in soils was studied by methods of batch equilibrium, kinetic, and anionic exchange resin membrane. The results showed that desorption amount of cumulative P increased with time increasing, and the desorption process was consonant with second-order kinetic equation. Release rate of P in different treatments was in order of PK > NPK > NK. The amount and rate of P released from red soil were higher than those of Fluvio-aquic soil. Desorbed P was significantly correlated with soil available P and P uptake by Plant. The maximum utilization of cumulative P in soils was about 45% of total phosphorus.

Heavy metals in water bodies purified by suspended substrate of rivers.

The equations, which are used to describe the relationships of adsorption quantity (s), adsorption percent (Pa), aqueous equilibrium concentration(c) of heavy metal on river suspended substrates and the ratio of adsorbent to water(j), are developed when heavy metal adsorption on river suspended substrate satisfies with linear adsorption equation. The results, according to the simulation from heavy metal adsorption on suspended substrates of several main Chinese rivers from a previous research report, indicated that these developed equations could describe the linear adsorption processes in practice very well, meanwhile, the adsorption equilibrium constant of adsorbent for heavy metal was an intensity factor regardless of ratio of suspended substrates to water but strongly depended on media's pH. Furthermore, the suspended substrates of Yellow River gave stronger purification ability for Pb than for Cd and Cu. When Cd was purified by different river suspended substrates, it exhibited that the order of their purification ability for Cd was that of Songhuajiang River > Zhujiang Pearl River > Yellow River, which was consistent with their contents of cation exchange capacity(CEC). In addition, we estimated and compared the purification ability of river suspended substrates for cadmium, and the resulting purification percent was 37.64%, 64.58% and 50.98% for Songhuajiang River, Yangtze River and Zhujiang River, respectively.

[Conformation transformation of lead in rhizosphere].

With rhizoboxes, this study dealt with the distribution and conformation transformation of lead in the rhizosphere and non-rhizosphere of wheat and rice grown on red soil. The results showed that the predominant forms of lead were acid dissolved and Carb-Pb (bound to carbonates), Exch-Pb (exchangeable-Pb), and FeMnO-Pb (boud to iron and manganese oxides). Exch-Pb in the rhizosphere of both rice and wheat was much higher than those in the non-rhizosphere, which means that the activation process in the rhizosphere was very strong, and bio-available Pb greatly increased. Various levels of Pb treatment and Pb-Cd interaction also had certain effects on the distribution of lead. In treatment of low Pb concentration, FeMnO-Pb was higher than Exch-Pb, but the contrary result was observed in treatment of high Pb concentration. Both Exch-Pb and FeMnO-Pb in wheat rhizosphere decreased with an increase of Cd. Exch-Pb in rice rhizosphere was correlative to the Cd content in soil. Compared with the treatment in the absence of Cd, the activation of Exch-Pb in rice rhizosphere was weaker in 5 mg Cd.kg-1 treatment, but stronger in 10 mg Cd.kg-1 treatment.