[Effect of Nano Zeolite on Growth, Activity of Antioxidant Enzyme, and Chemical Fractions and Concentration of Cd in Chinese Cabbage].

Pot experiment was carried out to investigate the influence of nano zeolite (NZ) and ordinary zeolite (OZ) on the growth, activities of antioxidant enzyme, Cd fraction and Cd concentration in two varieties of Chinese cabbage. The results showed that the activities of SOD, CAT and POD in the shoot and root of two varieties increased, and the dry weight of shoot and the total dry weight of Chinese cabbage increased by 4.5%-96.5% and 3.4%-88.4%, respectively. The application of zeolite effectively reduced the Cd concentration of shoot and root in the two varieties of Chinese cabbage, and the reduction range increased with the increase of the application amount of zeolite. Under the low Cd condition (1mg·kg-1 Cd), the Cd concentration of edible parts (shoots) in SD4 variety and XJC3 variety decreased by 1.0%-75.0% and 19.5%-68.9% (except the Cd1+OZ5/OZ10 processing), respectively. Under the high Cd condition (5 mg·kg-1 Cd), the Cd concentration of the edible parts (shoots) in SD4 variety and XJC3 variety decreased by 7.2%-53.2%(except Cd5+OZ10 processing) and 0.7%-63.0%, respectively. The Cd concentrations of the edible parts (shoots) in tow varieties of Chinese cabbage in the nano zeolite treatments decreased by 10.5%-65.7% compared with the ordinary zeolite treatments. In Cd contaminated soils (1 mg·kg-1 and 5 mg·kg-1 Cd),) the total extraction amount of Cd in the edible parts (shoots) of SD4 variety reduced by 12.4%-68.8% and 13.2%-55.6% (except of Cd5+OZ5 processing), and the total extraction amount of Cd in the edible parts (shoots) of XJC3 variety reduced by 9.4%-71.5% and 3.1%-38.7% (except of Cd1+OZ5 processing), respectively. The application amount of nano zeolite (NZ) and ordinary zeolite (OZ) was more, the reduction range of the total extraction amount of Cd in the edible parts (shoots) of two varieties of Chinese cabbage was greater.

[Effect of Nano Zeolite on Chemical Fractions of Cd in Soil and Uptake by Chinese Cabbage at Different Soil pH and Cadmium Levels].

Incubation experiments were carried out to investigate the influence of different nano zeolite(NZ) and ordinary zeolite(OZ) levels(0, 5, 10 and 20 g·kg-1) on the fraction distribution coefficient (FDC) of Cd and soil CEC at different soil pH (4, 5, 6, 7 and 8) when exposed to different cadmium(Cd) levels(1, 5, 10 and 15 mg·kg-1), and pot experiment were carried out to investigate the effects of nano zeolite(NZ) and ordinary zeolite(OZ) on the growth, Cd concentration and Cd accumulation of Chinese cabbage. The results showed that nano zeolite and ordinary zeolite decreased the concentration and FDC of exchangeable Cd (EX-F), and increased the concentration and FDC of carbonate(CAB-F), Fe-Mn oxide(FMO-F), organic matter (OM-F) and residual fraction(RES-F) in incubation experiments. At the end of incubation, the FDC of soil exchangeable Cd decreased from 72.0%-88.0% to 2.4%-10.7%. The decreasing effect of zeolite on the concentration and FDC of exchangeable Cd (EX-F) increased with the increase of zeolite, and the decreasing effect of nano zeolite (NZ) was better than that of ordinary zeolite (OZ). During the culture of 28 d, the concentration of different Cd fractions in soil was in order of EX-F>RES-F>FMO-F>CAB-F>OM-F under different pH conditions. Exchangeable fraction Cd was the dominant fraction of Cd in soil during the whole incubation. Soil CEC had significant negative correlation with soil exchangeable Cd (EX-F) (P<0.01), and significant positive correlation with the concentrations of Fe-Mn oxide(FMO-F) and organic matter (OM-F) in soil(P<0.01). Nano zeolite and ordinary zeolite effectively increased soil CEC, and soil CEC increased with the increase of the pH value of soil in the zeolite treatments. Significant negative correlation was found in soil pH with soil exchangeable Cd (EX-F)(P<0.01). The dry weight of plant tissues in Chinese cabbage increased by 14.3%-131.4% in the presence of nano zeolite(NZ) and ordinary zeolite(OZ), and Cd concentration of shoot and root decreased by 1.0%-75.0% and 3.8%-53.2%, respectively. Higher concentration and accumulation of Cd were observed in XJC3 variety than those in SD 4 variety. Compared with ordinary zeolite (OZ), nano zeolite (NZ) was better in increasing the biomass of Chinese cabbage as well as decreasing accumulation of Cd in Chinese cabbage.

[Effect of Nano Zeolite on Chemical Fractions of Cd in Soil and Its Uptake by Cabbage].

Incubation experiments were carried out to investigate the influence of different nano zeolite (NZ) and ordinary zeolite (OZ) levels(0, 5, 10 and 20 g · kg⁻¹) on the change trends in fraction distribution coefficient (FDC) of Cd when exposed to different Cadmium (Cd) levels (1, 5, 10 and 15 mg · kg⁻¹), and pot experiments were carried out to investigate their influence on soil Cd fraction and Cd uptake by cabbage. The results in incubation experiments showed that the application of nano zeolite as well as ordinary zeolite effectively decreased the FDC of exchangeable Cd and increased the FDC of Fe-Mn oxide fraction. The FDC of soil Cd from 0 d to 28 d was deceased at first, then increased and tended to be stable, and finally increased. At the end of incubation, the FDC of soil exchangeable Cd decreased from 72.0%-88.0% to 30.0%-66.4%. Exchangeable fraction Cd was the most dominant Cd fraction in soil during the whole incubation. The results in pot experiment indicated that the application of nano zeolite and ordinary zeolite decreased the concentration and FDC of soil exchangeable Cd, and concurrently the concentration and FDC of Cd in carbonate, Fe-Mn oxide, organic matter and residual fraction were increased. The lowest EX-Cd was observed in the treatment with high dose of nano zeolite (20 g · kg⁻¹). The FDC of exchangeable Cd showed significant negative relationship with the soil pH (P < 0.05), and was concurrently extremely positively correlated with Cd concentration in shoot and root of cabbage (P < 0.01). Soil pH increased by 1.8%-45.5% and 6.1%-54.3% in the presence of zeolite when exposed to 5 mg · kg⁻¹ 1 and Cd, respectively; FDC of exchangeable Cd decreased by 16.3%-47.7% and 16.2%-46.7%; Cd concentration in each tissues of cabbage decreased by 1.0%-75.0% and 3.8%-53.2%, respectively. Moreover, the reduction effect of nano zeolite on soil and plant Cd was better than that of ordinary zeolite. The growth of cabbage was stimulated by low and medium zeolite doses (≤ 10 g · kg⁻¹), while inhibited by high zeolite doses (20 g · kg⁻¹). Compared to ordinary zeolite, the biomass of Chinese cabbage was significantly increased by Nano zeolite, while the exchangeable Cd in soil as well as Cd concentration and Cd accumulation of cabbage were significantly reduced.

[Effect of Ryegrass and Arbuscular Mycorrhizal on Cd Absorption by Varieties of Tomatoes and Cadmium Forms in Soil].

Field trial was carried out to investigate the effects of ryegrass and arbuscular mycorrhizal single or compound treatment to two varieties of tomato ("Defu mm-8" and "Luobeiqi") on the plant growth, concentrations and accumulations of Cd as well as the impact on microorganisms, enzyme activities, pH and Cd forms in soil when exposed to Cd (5.943 mg · kg⁻¹). The results showed that dry weights of fruit, root, stem, leaf and plant significantly increased by single or compound treatment of ryegrass and arbuscular mycorrhizal by 14.1%-38.4% and 4.2%-18.3%, 20.9%-31.5% and 8.4%-10.3%, 13.0%-16.8% and 3.0%-9.5%, 10.7%- 16.8% and 2.7%-7.6%, 14.3%-36.6% and 4.5%-16.8%, respectively. The amounts of bacteria, fungi, actinomycetes of soil and the activities of urease, invertase, acid phosphatase, catalase in soil were increased by single or compound treatment of ryegrass and arbuscular mycorrhizal, and the soil microorganism amounts and enzyme activities significantly differed between the two varieties of tomato and treatments (P < 0.05). Soil pH was increased by single or compound treatment of ryegrass and arbuscular mycorrhizal, while the concentrations of EXC-Cd, CAB-Cd, Fe-Mn-Cd and total Cd in soil were decreased, and the total Cd content was decreased by 16.9%-27.8%. Cadmium concentrations in fruit, leaf, stem and root of both varieties were significantly decreased by 6.9%-40.9%, 5.7%-40.1%, 4.6%-34.7% and 9.8%-42.4%, respectively. Cadmium accumulations in tomato were in order of leaf > stem > root > fruit. Comparing the two tomato varieties, Cd concentrations and Cd accumulations in fruit and plant were in order of "Luobeiqi" < "Defu mm-8" in the presence or absence of single or compound treatment of ryegrass and arbuscular mycorrhizal.