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[Objective] Black rock series contain high amounts of cadmium (Cd) and selenium (Se). During weathering and soil formation on the rocks, the chemical form transformation and release of Cd and Se from the rocks can have an impact on the surrounding ecological environment. [Methods] In this study, a black rock series distribution area of Hetang formation of the Lower Cambrian was selected in northwest Zhejiang. By collecting horizonal soil samples from soil profiles along different parts of the terrain (hill upslope, hill middle slope, hill downslope, inter hill valley bottom and valley terrace), the quantity and chemical form transformation patterns of Cd and Se during the process of weathering soil formation and weathering material migration of the black rock series were discussed. [Results] The results showed that total Cd and total Se in the soil decreased from parent rock to soil. The loss of Cd and Se in the weathered matter of black rock series increased with the increasing of transportation distance along the hilly slope, and the loss of Cd and Se in the process of evolution from slope deposit to diluvium was greater than that from residual to slope deposit. The Cd and Se lost from the weathered materials could affect the contents of Cd and Se in the topsoil derived from the alluvial of the downstream river in the way of water diffusion, but the degree of influence decreased with the increasing of distance. With the increasing of the transportation distance of weathered materials and the evolution of soil, the transformation of carbonate bound Cd and residual Cd to water-soluble Cd, exchangeable Cd, organic matter bound Cd and oxide bound Cd occurred. The residual Se gradually activated and transformed into exchangeable Se, organic matter bound Se and oxide bound Se. The results also showed that soil water-soluble Cd, exchangeable Cd (Se) and organic matter bound Cd (Se) showed an increasing trend toward the surface. The organic enrichment and topsoil enrichment of Se were more obvious than those of Cd. [Conclusion] The results indicated that the weathering of black rock series could not only directly affect the contents of soil Cd and Se in their distribution area through residue, but also affect the contents of soil Cd and Se in the surrounding areas through water diffusion.

【Objective】 Reclaiming the saline coastal soils in eastern China is crucial for ensuring food security. Given the significance of soil carbon in soil quality, this paper investigates the change in soil organic carbon and phosphorus in the soil following initiation of reclamation. 【Method】 The experiment was conducted in the northern regions of Hangzhou Bay and Yueqing Bay in eastern Zhejiang province. Soil samples were collected from vegetable fields, orchards, and paddy fields to measure their organic carbon, phosphorus, and other soil properties, from which we analyzed the relationship between soil organic carbon, phosphorus composition, reclamation duration, and land usage. A non-reclaimed soil was taken as the control. 【Result】 As reclamation time elapsed, soil pH decreased while total organic carbon (TOC), total phosphorus (TOP), and available phosphorus increased. Fifty years of reclamation led to a reduction in soil pH in Hangzhou Bay and Yueqing Bay by 1.72 to 2.36 and 1.14 to 2.24, respectively. This was accompanied by significant increases in organic carbon and TOP by 126.46% to 294.97% and 130.37% to 266.14%, and available phosphorus by 17.66% to 100.00% and 39.31% to 87.20%, respectively. The decrease in soil pH among different land usages was ranked in the order of wasteland > paddy field > orchard > vegetable field; the increase in soil organic carbon followed the order of paddy field > orchard > vegetable field > wasteland; and the increase in TOP and available phosphorus followed the order of wasteland < paddy field < orchard < vegetable land. Reclamation also significantly increased different forms of soil organic carbon. Over time, the ratio of free particulate organic carbon to organic carbon (fPOC/TOC) in micro-aggregates decreased initially and then gradually increased, while the ratio of occluded particulate organic carbon to organic carbon (oPOC/TOC) increased gradually. The ratio of mineral-associated organic carbon to organic carbon (MOC/TOC) initially increased significantly and then decreased slowly. Land usage had a notable impact on the MOC/TOC ratio, with paddy fields showing the highest influence, followed by orchards and vegetable fields. The impact of land usage on TOP and available phosphorus was more significant than reclamation time. Except for residual phosphorus and HCl-P, other forms of phosphorus increased with reclamation time. It was also found that with the increase in reclamation time, the fraction of residual phosphorus and HCl-P decreased, while the fraction of phosphorus in other forms increased. TOC and organic carbon in different forms exhibited a strong correlation, but no correlation was found between TOP and phosphorus. 【Conclusion】 Reclamation of the coastal saline soils results in continuous changes in composition and content of organic carbon and phosphorus, characterized by decreasing pH, increasing organic carbon and phosphorus. Land usage has a more substantial impact on the change in organic carbon and phosphorus than reclamation history. Growing rice promotes organic carbon sequestration, whereas vegetable cultivation enhances phosphorus accumulation.

【Objective】 Nutrient loss from agricultural soils is a great environmental concern in many countries, and rotating crops and intercropping are believed to be one solution to slowing down this loss. The aim of this paper is to investigate the efficacy of different intercropping systems in reducing the loss of suspended solids and major dissolved nutrients from farmland. 【Method】 The experiment was conducted from 2014 to 2017 in Zhejiang province, southeast China. We compared five intercropping systems: vegetable - Zizania latifolia, vegetable - paddy rice, orchard - Zizania latifolia, mulberry - paddy rice and orchard - lotus pond, with traditional cultivation used by local farmers taken as the control. In each system, we measured the reduction in sediment loss, change in total and soluble phosphorus (P), total and soluble nitrogen (N). 【Result】 Compared with the control, all five intercropping systems reduced the loss of suspended solid and P and N by more than 70% on average. In particular, they reduced the total P loss by 90.63%, soluble P loss by 89.14%, suspended solid loss by 88.72%, soluble N loss by 86.75%, and total N loss by 86.64%. In terms of efficacy, the five systems were ranked in the order of orchard - lotus pond > vegetable - Zizania latifolia > orchard - Zizania latifolia > mulberry - paddy rice > vegetable - paddy rice. 【Conclusion】 The mechanisms underlying the intercropping systems for reducing loss of suspended solids and nutrients from soils was the reduced drainage and the increased ability of soil to absorb nutrients. Intercropping is a low-cost but efficient technology to ameliorate nutrient loss from farmland systems. For the five intercropping systems we compare, lotus pond-Zizania latifolia was most effective.

Systematic studies on the genesis, properties, and distribution of natural nanoparticles (NNPs) in soil remain scarce. This study examined a soil chronosequence of continuous paddy field land use for periods ranging from 0 to 1 000 years to determine how NNPs in soil changed at the early stages of soil genesis in eastern China. Soil samples were collected from coastal reclaimed paddy fields that were cultivated for 0, 50, 100, 300, 700, and 1 000 years. Natural nanoparticles were isolated and characterized along with bulk soil samples (< 2-mm fraction) for selected physical and chemical properties. The NNP content increased with increasing soil cultivation age at 60 g m−2 year−1, which was related to decreasing soil electrical conductivity (172–1 297 µS cm−1) and NNP zeta potentials (from –22 to –36 mV) with increasing soil cultivation age. Changes in several NNP properties, such as pedogenic iron oxide and total organic carbon contents, were consistent with those of the bulk soils across the soil chronosequence. Notably, changes in NNP iron oxide content were obvious and illustrated active chemical weathering, pedogenesis, and potential impacts on the microbial community. Redundancy analysis demonstrated that the soil cultivation age was the most important factor affecting NNP properties, contributing 60.7% of the total variation. Cluster and principal component analysis (PCA) revealed splitting of NNP samples into age groups of 50–300 and 700–1 000 years, indicating rapid evolution of NNP properties, after an initial period of desalinization (approximately 50 years). Overall, this study provides new insights into NNP evolution in soil during pedogenesis and predicting their influences on agriculture and ecological risks over millennial-scale rice cultivation.