[Influence and assessment of biochar on the bioavailability of chlorobenzenes in soil].

A laboratory experiment was conducted to study the influence of biochar on the residues of chlorobenzenes (CBs) in soil. Two treatments as the control and the addition of 1% wheat straw biochar were designed. Three chemical extractions as butanol, HPCD and Tenax extractions and earthworm accumulation were used to assess the changes of the bioavailability of CBs in soil. The results showed that the residues of HCB, PeCB and 1,2,4,5-TeCB in the control were 29.87%, 18.02% and 5.16% after 4 months incubation, however, the residues of HCB, PeCB and 1,2,4,5-TeCB in biochar amended soil were 68.25%, 61.32% and 58.02%, respectively, indicating that biochar amendment would inhibit the dissipation of CBs in soil. Butanol, HPCD and Tenax extraction as well as earthworm accumulation results demonstrated that the bioavailability of CBs in soil was significantly affected by biochar amendment (P < 0.05). With aging time increase, the biochar amendment significantly lowered the bioavailability of CBs. The extraction ratios differed among different chemical extraction methods. The extraction ratio was HCB > PeCB > 1,2,4,5-TeCB for butanol and Tenax extraction, while 1,2,4,5-TeCB > PeCB > HCB for HPCD extraction. The bioaccumulation factor of CBs by earthworm was significantly lower in biochar amended soil compared to the control (P < 0.05). This study showed that the biochar could reduce the bioavailability of organic pollutants, however, the high residues of the pollutants in soil showed potential environmental risk.

[Contribution of wheat rhizosphere respiration to soil respiration under elevated atmospheric CO2 and nitrogen application].

With the support of free-air carbon dioxide enrichment (FACE) system and by using isotope 13C technique, and through planting wheat (Triticum aestivum L., C3 crop) on a soil having been planted with maize (Zea mays L., C4 crop) for many years, this paper studied the effects of elevated atmospheric CO2 and nitrogen application on the delta 13C value of soil emitted CO2 and the wheat rhizosphere respiration. With the growth of wheat, the delta 13C value of soil emitted CO2 had a gradual decrease. Elevated atmospheric CO2 concentration (200 micromol mol(-1)) decreased the delta 13C value of emitted CO2 at booting and heading stages significantly when the nitrogen application rate was 250 kg hm(-2) (HN), and at jointing and booting stages significantly when the nitrogen application rate was 150 kg hm(-2) (LN). Nevertheless, the elevated atmospheric CO2 promoted the proportions of wheat rhizosphere respiration to soil respiration at booting and heading stages significantly. From jointing stage to maturing stage, the proportions of wheat rhizosphere respiration to soil respiration were 24%-48% (HN) and 21%-48% (LN) under elevated atmospheric CO2, and 20%-36% (HN) and 19%-32% (LN) under ambient atmospheric CO2. Under both elevated and ambient atmospheric CO2 concentrations, the delta 13C value of emitted CO2 and the rhizosphere respiration had different responses to the increased nitrogen application rate, and there was a significant interactive effect of atmospheric CO2 concentration and nitrogen application rate on the wheat rhizosphere respiration at jointing stage.

[Effects of O3-FACE(ozone-free air control enrichment) on gas exchange and chlorophyll fluorescence of rice leaf].

O3-FACE (Ozone-free air control enrichment) platform has been established for observing the effect of elevated tropospheric ozone concentration on the gas exchange and chlorophyll fluorescence of two rice varieties (Wuyunjing 21 and Liangyoupeijiu). The results showed that high ozone concentration decreased the net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) of rice leaves. After 76d fumigation the decline in them for Wuyunjing 21 was as follows: 21.7%, 26.64% and 24.74% respectively, and that for Liangyoupeijiu was as follows: 25.53%, 30.31% and 25.48% respectively; however, no significant impact on leaf intercellular CO2 concentration was observed. Chlorophyll fluorescence kinetics parameters changed as can be seen by the decrease in F0 (initial fluorescence in the dark), ETR (The apparent electron transfer rate) and psiPSII (actual photochemical efficiency of PS II in the light), and the increase in NPQ (non-photochemical quenching). After 76 days of O3 treatment, the NPQ of Wuyunjing 21 and Liangyoupeijiu was enhanced by 16.37% and 11.77%, respectively. The impact of ozone on rice was a cumulative effect, and the extent of variation in the above parameters and the differences between the two varieties were enlarged as the O3 treatment time increased; At the same time because the rice leaf intercellular CO2 concentration did not significantly reduce, the inferred decrease in net photosynthetic rate was restricted by non-stomatal factors. The results of this experiment indicated that Liangyoupeijiu was more susceptible to ozone than Wuyunjing 21.

[Photosynthetic damage induced by elevated O3 in two varieties of winter wheat with free air controlled enrichment approach].

O3-FACE (ozone-free air controlled enrichment) platform has been established for observing the photosynthetic damage induced by elevated O3 in functional leaves of two winter wheat (Tritcium aestivum L.) varieties (Yangmai 16 and Yannong 19) during grain filling stage. The results showed that the response trend of all the parameters was similar: (1) The net photosynthetic rate (Pn) decreased gradually and after 35 days of O3 treatment, Pn decreased by 56.21% and 21.82% for Yannong 19 and Yangmai 16, respectively. (2) Chlorophyll fluorescence kinetics parameters changed as decreased in Fv/Fm (maximal photochemical efficiency of PS II in the dark), qp (photochemical quenching), Phiexe (excitation capture efficiency of PS II or intrinsic PS II efficiency), PhiPSII (actual photochemical efficiency of PS II in the light), and increased in NPQ (non-photochemical quenching); Energy distribution parameters changed as rose in % D (fraction of light absorbed in PS II that is dissipated in the PS II antenna), reduced in % P (fraction of light absorbed that is used in photochemistry), and no significant changed in % X (fraction of light absorbed that is not used or dissipated in the PS II antenna). After 35 days of O3 treatment, the actual photochemical efficiency of PS II of Yannong 19 and Yangmai 16 were reduced by 24.42% and 9.97%, respectively.(3) It was declined in Chlt/Car (total chlorophyll content/carotinoid content) while the ratio of Chla/Chlb (chlorophyll a content/chlorophyll b content) was increased. There was a growth in Mg2+, Ca2+-ATPase, activities and ATP contents in chloroplast. The extent of variation in the above parameters and the differences between the two varieties were enlarged as the O3 treatment time increasing and it could be found a more serious damage effect in Yannong 19 than that of in Yangmai 16. In conclusion, the responses of the capacities of defense and repair systems of the two varieties to elevated O3 were reflected by increase in heat dissipation, changes in contents and composition of photosynthetic pigments, and enhancement in the ATP (ATP enzyme) activities in chloroplast. With the time of O3 treatment elongating, there was an accumulation effect of 03 damage to wheat and a great different tolerance between the two varieties was observed.