Qingye Hou

Evaluation of potential effects of soil available phosphorus on soil arsenic availability and paddy rice inorganic arsenic content

The transfer of arsenic from paddy field to rice is a major exposure route of the highly toxic element to humans. The aim of our study is to explore the effects of soil available phosphorus on As uptake by rice, and identify the effects of soil properties on arsenic transfer from soil to rice under actual field conditions. 56 pairs of topsoil and rice samples were collected. The relevant parameters in soil and the inorganic arsenic in rice grains were analyzed, and then all the results were treated by statistical methods. Results show that the main factors influencing the uptake by rice grain include soil pH and available phosphorus. The eventual impact of phosphorus is identified as the suppression of As uptake by rice grains. The competition for transporters from soil to roots between arsenic and phosphorus in rhizosphere soil has been a dominant feature.

Annual input fluxes of heavy metals in agricultural soil of Hainan Island, China

The accumulation of heavy metals in farmland has become an important issue related to food security and environmental risk. The annual inputs of heavy metals (As, Cd, Hg, Pb, Cr, Cu, and Zn) to agricultural soil for a full year in Hainan Island have been studied. Three fluxes through the cultivated horizon were considered: (1) atmospheric depositions, (2) fertilization, and (3) irrigation water. The corresponding samples were collected and analyzed on a large regional scale. The total input fluxes show obvious spatial variability among different regions. The inventory of heavy metal inputs to agricultural land demonstrates that agricultural soil is potentially at risk of heavy metal accumulation from irrigation water. The potential at risk of heavy metal accumulation from atmospheric deposition and fertilizer is relatively low compared to irrigation. The results indicate that Hg is the element of prior concern for agricultural soil, followed by Cd and As, and other heavy metal elements represent little threat to the environment in the study area. This work provides baseline information to develop policies to control and reduce toxic elements accumulated in agricultural soil.

Eco-geochemical Assessment of Agroecosystems: Cd in the Chengdu Economical Region, Sichuan, China

The cadmium (Cd) in the Chengdu Economic Region was studied as an example of eco-geochemical assessment on agroecosystems. Dry and wet atmospheric deposition samples, chemical fertilizers, irrigation water, and plants were collected. The concentrations of Cd and other elements in these samples were analyzed and the fluxes of input and output of the agroecosystem were calculated. The results indicated that the Cd was more concentrated in the surface soil than in the deep soil, and Cd concentration in some rice samples exceeded the upper limit of the pollution-free agricultural products. The input of Cd into the agroecosystem was 17.8 g·hm−2·y−1 on average, which accounted for 85.2% of the total input. Infiltration (2.34 g·hm−2·y−1) and harvest (1.87 g·hm−2·y−1) were the two most important Cd outputs. The average increase of Cd content in soil was 0.006 mg·kg−1·y−1, which was a result of sources outside of the agroecosystem. In the next 20 years, the area of the grade III soil will increase 2–3 times under the current input and output condition of Cd, which will lead to significant decrease of the arable land. The decrease of the pH in the study area was 0.106 y−1 because of fertilization and acid rain, of which 89.6% was from the contribution of chemical fertilizers. The present study indicates that, even though 95% of the rice production is safe, after 20 years, 70% of the safe soil will degrade, and the area of alarming soil will increase rapidly from 4% to 27% of the total cultivated area in the region.

Ecological geochemical assessment and source identification of trace elements in atmospheric deposition of an emerging industrial area: Beibu Gulf economic zone

Industrialization and urbanization have led to a deterioration in air quality and provoked some serious environmental concerns. Fifty-four samples of atmospheric deposition were collected from an emerging industrial area and analyzed to determine the concentrations of 11 trace elements (As, Cd, Cu, Fe, Hg, Mn, Mo, Pb, Se, S and Zn). Multivariate geostatistical analyses were conducted to determine the spatial distribution, possible sources and enrichment degrees of trace elements in atmospheric deposition. Results indicate that As, Fe and Mo mainly originated from soil, their natural parent materials, while the remaining trace elements were strongly influenced by anthropogenic or natural activities, such as coal combustion in coal-fired power plants (Pb, Se and S), manganese ore (Mn, Cd and Hg) and metal smelting (Cu and Zn). The results of ecological geochemical assessment indicate that Cd, Pb and Zn are the elements of priority concern, followed by Mn and Cu, and other heavy metals, which represent little threat to local environment. It was determine that the resuspension of soil particles impacted the behavior of heavy metals by 55.3%; the impact of the coal-fired power plants was 18.9%; and the contribution of the local manganese industry was 9.6%. The comparison of consequences from various statistical methods (principal component analysis (PCA), cluster analysis (CA), enrichment factor (EF) and absolute principle component score (APCS)-multiple linear regression (MLR)) confirmed the credibility of this research.

Evaluation of the potential effects of soil properties on molybdenum availability in soil and its risk estimation in paddy rice

PurposeMolybdenum (Mo) is an essential element critical to biochemical processes in plants and animals. The effects of soil properties on the availability of Mo to rice were investigated.Materials and methodsA total of 56 paired samples of topsoil and rice were collected. Relevant parameters in soil and Mo in rice grains were measured, and the results were analyzed using statistical methods.Results and discussionDescriptive statistics for Mo contents in soil and soil properties are presented. Mo adsorption can be predicted using the following soil chemical properties: pH, cation exchange capacity, soil organic carbon (SOC) content, inorganic carbon content, and iron oxide content. This study focused on soil pH, SOC, S, and Na2O because these parameters are the most important factors in controlling the levels of soil Mo in correlation analyses. SOC and available P were the best predictors of Mo availability.ConclusionsAmong the soil properties in this study, soil pH is the most important factor restricting the supply of soil available Mo. The dominant factors that directly affected Mo availability were the levels of available P and SOC. Leaching and adsorption of Mo in soils were considered key processes that affected the levels of soil available Mo. Rice grown in the study area may pose potential Mo risks to food safety and human health, especially in rural areas.

Annual input fluxes and source identification of trace elements in atmospheric deposition in Shanxi Basin: the largest coal base in China.

Industrialization and urbanization have led to a great deterioration of air quality and provoked some serious environmental concerns. One hundred and five samples of atmospheric deposition were analyzed for their concentrations of 13 trace elements (As, Cd, Cu, Fe, Al, Co, Cr, Hg, Mn, Mo, Pb, Se, and Zn) in Shanxi Basin, which includes six isolate basins. The input fluxes of the trace elements in atmospheric deposition were observed and evaluated. Geostatistical analysis (EF, PCA, and CA ) were conducted to determine the spatial distribution, possible sources, and enrichment degrees of trace elements in atmospheric deposition. Fe/Al and K/Al also contribute to identify the sources of atmospheric deposition. The distribution of trace elements in atmospheric deposition was proved to be geographically restricted. The results show that As, Cd, Pb, Zn, and Se mainly come from coal combustion. Fe, Cu, Mn, Hg, and Co originate mainly from interactions between local polluted soils and blowing dust from other places, while the main source of Al, Cr, and Mo are the soil parent materials without pollution. This work provides baseline information to develop policies to control and reduce trace elements, especially toxic elements, from atmospheric deposition. Some exploratory analytical methods applied in this work are also worth considering in similar researches.

From soil to rice – a typical study of transfer and bioaccumulation of heavy metals in China

ABSTRACT For the purpose of studying the contamination, bioaccumulation and transfer of heavy metals and understanding the effects of soil properties on these, the work was carried out on a regional scale. A total of 30 sets of soil and pairing rice tissues samples (root, straw and grain) were collected in Xiangzhou of Guangxi, China; soil properties and Cd, Cu, Pb and Zn of different rice tissues were analyzed. The mobility and bioaccumulation of Cd, Cu, Pb and Zn were assessed by transfer coefficients and bioaccumulation factors of them. The results indicated that the excess proportions of Cd and Pb were 50%, 3.33% and 30%, 6.67% in soil and rice grain, respectively, according to Chinese maximum permitted concentrations of heavy metals. Cd and Zn showed stronger bioaccumulation and mobility capability; the bioaccumulation and transfer of Cu were slightly lower than Cd and Zn; Pb had the weakest mobility. The bioaccumulation and mobility of heavy metals from soil to rice were restrained by soil pH, CaO, SOC, Fe oxides and Mn.