改良剂对酸性土壤上伴矿景天铝毒缓解作用及镉锌吸收性的影响

为探究不同改良剂对酸性土壤铝(Al)胁迫条件下镉(Cd)锌(Zn)超积累植物伴矿景天Sedum plumbizincicola生长以及镉和锌吸取修复效率的影响,分别添加不同种类改良剂(钙镁磷肥(CMP)、MgCO3、KH2PO4)和不同浓度CMP进行温室盆栽试验。结果表明,CMP能够一定程度上提高土壤pH值并降低土壤交换性Al的浓度,MgCO3能够显著提高土壤pH值和降低土壤交换性Al的浓度,KH2PO4能够降低土壤中交换性Al浓度但未改变土壤pH值。施用适量的CMP(9.39 mg/kg)能够提高伴矿景天生物量和Cd、Zn吸取修复效率,用量过高会抑制伴矿景天生长和Cd、Zn修复效率;施用MgCO3可增大伴矿景天生物量和Cd、Zn修复效率,施用KH2PO4反而抑制了伴矿景天生长。酸性土壤上施用适量的CMP和MgCO3能够缓解伴矿景天的铝毒作用,维持较高的重金属吸收效率。

贵州省典型汞铊矿区周边农田土壤跳虫群落特征

大量的采矿活动导致矿区周边土壤重金属污染,严重危害土壤生物安全。汞、铊等重金属元素毒性强,相关污染的土壤生态风险鲜有研究。跳虫作为土壤环境变化指示生物,能很好地反映土壤质量的健康状况。本研究以贵州省某汞铊矿区周边的农田土壤为研究对象,按离矿区距离和作物类型设置4个采样区,每个采样区种植2种作物,每种作物农田设置3个样方。研究土壤跳虫群落结构和多样性及其影响因子。结果表明,调查区内跳虫平均密度为12,000 ind./m2;采样区距离矿区越近,土壤重金属污染程度越大,综合污染指数越高,跳虫种数、密度、多样性和丰富度指数均呈先增加再降低的趋势;环境因子分析表明重金属显著影响跳虫群落结构:Folsomides americanus、Isotomiella minor和Protaphorura encarpatus数量与汞、铊和砷含量呈负相关。高有机质含量能缓解重金属对土壤跳虫的影响,但作物类型(玉米与薏仁)对土壤跳虫群落结构的影响无显著差异。本研究结果表明土壤有机质或能反向调节重金属污染对土壤跳虫群落的影响。

Adsorption and desorption characteristics of diphenylarsenicals in two contrasting soils

Diphenylarsinic acid （DPAA） is formed during the leakage of aromatic arsenic chemical weapons in soils, is persistent in nature, and results in arsenic contamination in the field. The adsorption and desorption characteristics of DPAA were investigated in two typical Chinese soils, an Acrisol （a variable-charge soil） and a Phaeozem （a constant-charge soil）. Their thermodynamics and some of the factors influencing them （i.e., initial pH value, ionic strength and phosphate） were also evaluated using the batch method in order to understand the environmental fate of DPAA in soils. The results indicate that Acrisol had a stronger adsorption capacity for DPAA than Phaeozem. Soil DPAA adsorption was a spontaneous and endothermic process and the amount of DPAA adsorbed was affected significantly by variation in soil pH and phosphate. In contrast, soil organic matter and ionic strength had no significant effect on adsorption. This suggests that DPAA adsorption may be due to specific adsorption on soil mineral surfaces. Therefore, monitoring the fate of DPAA in soils is recommended in areas contaminated by leakage from chemical weapons.

Effects of water management on arsenic and cadmium speciation and accumulation in an upland rice cultivar

Pot and field experiments were conducted to investigate the effects of water regimes on the speciation and accumulation of arsenic（As） and cadmium（Cd） in Brazilian upland rice growing in soils polluted with both As and Cd. In the pot experiment constant and intermittent flooding treatments gave 3–16 times higher As concentrations in soil solution than did aerobic conditions but Cd showed the opposite trend. Compared to arsenate, there were more marked changes in the arsenite concentrations in the soil solution as water management shifted, and therefore arsenite concentrations dominated the As speciation and bioavailability in the soil. In the field experiment As concentrations in the rice grains increased from 0.14 to 0.21 mg/kg while Cd concentrations decreased from 0.21 to 0.02 mg/kg with increasing irrigation ranging from aerobic to constantly flooding conditions. Among the various water regimes the conventional irrigation treatment produced the highest rice grain yield of 6.29 tons/ha. The As speciation analysis reveals that the accumulation of dimethylarsinic acid（from 11.3% to 61.7%） made a greater contribution to the increase in total As in brown rice in the intermittent and constant flooding treatments compared to the intermittent-aerobic treatment. Thus, water management exerted opposite effects on Cd and As speciation and bioavailability in the soil and consequently on their accumulation in the upland rice. Special care is required when irrigation regime methods are employed to mitigate the accumulation of metal（loid）s in the grain of rice grown in soils polluted with both As and Cd.

Toxicity of lead pollution to the collembolan Folsomia candida in Ferri-Udic Cambosols

Toxic effect of lead(Pb) pollution on Collembola in soils has seldom been studied in depth, which is especially true for growth responses since the juveniles are very small and numerous. A single species test was conducted using the collembolan Folsomia candida as the indicator species, and soil Pb pollution(at Pb concentrations of 0, 300, 600, 1 200, 2 400, and 4 800 mg kg^(-1)) was simulated by mixing Pb(NO_(3))_(2) with a natural unpolluted soil. Adult survival, reproduction, body length, and body Pb concentration were determined. Adult survival and reproduction started to decrease at soil Pb concentrations of 1 200 and 600 mg kg^(-1), respectively. Lead concentrations in adult and juvenile bodies increased with increasing Pb concentration in soil. The percentage and individual abundances based on body length analysis showed that the larger adults(2.1–2.6 mm, P < 0.01) were more sensitive to soil Pb concentration than the intermediate(1.9–2.1 mm, P < 0.001) and smaller(1.7–1.9 mm, P < 0.001) adults. Similarly, the larger juveniles(1.0–1.4 mm, P < 0.001) were more sensitive to soil Pb concentration than the intermediate(0.6–1.0 mm, P < 0.001) and smaller(0.3–0.6 mm, P < 0.001) juveniles. For both adults or juveniles, the abundance and percentage of larger individuals declined significantly with increasing soil Pb concentration, suggesting that larger individuals were more sensitive to soil Pb pollution. Therefore, body length features, especially the percentage and abundance of larger individuals, would be potential bio-indicators of soil Pb pollution and possibly other types of soil pollution.

Biological transfer of silver under silver nanoparticle exposure and nitrogen transfer via a collembolan- predatory mite food-chain and ecotoxicity of silver sulfide

The development of nanotechnology has accelerated the use of silver nanoparticles(AgNPs)in household chemicals and the accumulation of Ag in sewage treatment systems.The application of sewage sludge products to soils raises concerns over the safety of Ag in the function and biogeochemical cycles of the soil belowground ecosystem.Here,we assess the potential risk of the accumulation and transfer of Ag under AgNPs exposure and its effects on the trophic transfer of nitrogen(N)through a soil animal food chain(Folsomia candida–Hypoaspis aculeifer).The formation of stable silver sulfide(Ag_(2)S)was also studied via a single species test using F.candida.Concentrations of Ag in F.candida increased with increasing AgNPs concentration,as did those in the predator H.aculeifer,but the Ag bioaccumulation factors of both animals were<1.Folsomia candida body tissue 15 N abundance declined markedly compared with that of H.aculeifer.Silver sulfide did have adverse effects on the survival and reproduction of F.candida.The Ag concentrations of F.candida increased with increasing Ag_(2)S concentration in sludge-treated soils.Silver sulfide showed ecotoxicity to the collembolan,therefore ecotoxicity resulting from the transformation and fate of AgNPs in soils needs to be considered before biosolid products are applied to agricultural soils.